1

CHAPTER 1

INTRODUCTION

11 HYDRAZINE

Hydrazine is the simplest diamine in its class of compounds and may be

thought of as derived from ammonia by replacement of a hydrogen atom by the ndash

NH2 group The hydrated hydrazine N2H4H2O was first prepared by Curtius in

1887 The anhydrous hydrazine as a water free base was prepared by De Bruyn for

the first time Preparation of hydrazine by the oxidation of NH3 with hypochlorite ndash

a process that became the chief commercial method of manufacture was first

demonstrated by Raschig

For many years hydrazine was considered as a special chemical available

only in aqueous solution and in the formation of few salts It remained as a

laboratory curiosity for over 50 years During the Second World War Germany

discovered the interesting property of hydrazine as a rocket fuel Now it is one of the

most powerful liquid fuels among current rocket propellants However the chemical

uses of hydrazine now far surpass its use as a fuel The bibliographic works on

hydrazine (Bottomley 1970 Schmidt 1984) are indispensable bibles for hydrazine

chemists The field of hydrazine chemistry and its applications are over widening

111 Applications

Anhydrous hydrazine (mp 2 degC bp114 degC) a fuming colourless liquid

is surprisingly stable in view of its endothermic nature(∆Hf = 5043KJ mol) and its

simple methyl and dimethyl derivatives have endothermic heats of formation and

2 high heats of combustion They have nitrogen in -2 valence state Nitrogens natural

tendency however is towards zero valency (N equiv N) which gives off nearly six

times as much as energy as the N-N bond Thus tremendous amount of energy is

released not only during decomposition of N2H4 to N2 but also at the time of the

mixing with the oxidizer Hence they are used as fuels in rocket and spacecraft

powered engines As a strong reducing agent hydrazine is used for corrosion control

in boilers and hot water heating systems for metal plating and for reducing noble

metal catalysts and unsaturated bonds in organic compounds It is also an oxidizing

agent under suitable conditions with two active nucleophilic nitrogens and four

replaceable hydrogens It is the starting material for many derivatives among which

foaming agents for plastics antioxidants polymers polymer cross linking and chain

extending agents as well as biologically active pesticides herbicides plant growth

regulators and pharmaceuticals are important As it is a good complexing ligand

numerous complexes have been studied (Bottomley 1970 and Schmidt 1984) Many

heterocyclics are based on hydrazine with rings containing from 1 to 5 nitrogen

atoms as well as other hetero atoms The many advantageous properties of hydrazine

are exploited in the field of photographic chemicals and dyes New uses for

hydrazine derivatives are discovered daily

112 Basicity and Salt Forming Ability

As an Arrhenius base hydrazine is a weaker base than ammonia because

the more electronegative group NH2 has the - I effect on the lone pair of electron of

the neighbouring nitrogen making it less basic for protonation

NH3 + H2O rarr NH4+ + OH - Kb =18 X 10-5 (11)

N2H4 + H2O rarr N2H5 + + OH - Kb = 85 X 10-7 (12)

3

N2H5+ + H2O rarr N2H6

2+ + OH - Kb = 89 X 10-16 (13)

In principle it can form two series of salts with monobasic acids one

having the hydrazinium (+1) cation N2H5+ and the other hydrazinium(+2) cation

N2H62+ The basic ionization constants of hydrazine in water suggest that N2H6

2+

exists only in the solid state or in conc acid solutions The salts containing this

cation are extensively hydrolyzed in water to give highly acidic solutions containing

the N2H5+ ion

N2H62+ + H2O rarr N2H5

+ + H3O+ (14)

The divalent cation seems to violate Paulingrsquos adjacent charge rule

H3N+- NH3+ but is likely that this is in equilibrium with other tautomeric forms eg

H3N+- NH2H+The N2H5+ salts have been prepared with carboxylic acids and

numerous examples of them have been reported (Schmidt 1984) whereas the salts of

N2H62+ are limited (Starosta and Leciejewicz 2007 Starosta and Leciejewicz 2008)

12 TYPES OF HYDRAZINE SALTS

The hydrazinium salts are inorganic derivatives well-crystallized and

colorless compounds comparable to the corresponding ammonium salts The

reducing property and the lack of thermal stability of hydrazinium salts differentiate

them from ammonium salts

Hydrazine forms not only mono- and di acid salts of the types N2H4HA

N2H42HA where HA represents a simple mono-basic acid but also compounds of

the types 2N2H4H2B and N2H4H2B where H2B represents a dibasic acid The best

known of these are N2H4HA or 2N2H4H2B [N2H5A or (N2H5)2B] and N2H42HA or

4 N2H4H2B [N2H6A2 or N2H6B] and not N2H42H2B The N2H5

+ and N2H62+ salts are

generally referred to as hydrazinium(+1) and hydrazinium(+2) salts respectively

Even though N2H62+ salts are generally formed with strong acids double

salts of this cation with ammonium ion are also formed For example

(NH4)2N2H6(ClO4)4 and (NH4)2N2H6(SO4)2 (Frech et al 1993) salts have been

prepared and characterized Recently redetermination of hydrazinium (+2)

dichloride (N2H62+2Cl-) has been reported (Kruszynski and Trzesowska 2007) In

many cases the preparation of hydrazinium salts is very easy but in other cases

such as in the preparation of hydrazinium nitrates or perchlorates special

precautions are necessary to prevent unexpected explosions

It is interesting to note that a few hydrazine salts form hydrates eg

N2H5ClO405H2O N2H6X22H2O X = ClO4- Br- and I- It has been shown by IR

thermal and conductivity measurements that water in these compounds is partially

present as oxonium ion H3O+ and involved in hydrogen bonding with N2H4 (Patil et

al 1983) (N2H5)2SO3H2O (Patil et al 1980)

121 Methods of Preparation of Simple Hydrazinium Salts

1211 Acid -Base Neutralization Method

In this method the base is directly neutralized by the addition of the

corresponding acids in the aqueous medium The pH of the solution is an important

factor to get the type of salt desired The reactions are represented as given below

N2H4H2O + HA rarr N2H5A + H2O (15)

N2H4 H2O + 2HA rarr N2H6A2 + H2O (16)

N2H4 H2O + H2B rarr N2H6B + H2O (17)

5 where HA is a monobasic acid eg HCl CH3COOH HNO3 etc and H2B is a

dibasic acid eg H2SO4 H2C2O4 etcAcids like H2SO4 (Hudson et al 1967) and HF

(Patil et al 1979) react with N2H4H2O to form exclusively N2H62+ salts because of

their strong acidic nature and the low solubility of the resulting salts

1212 Double Decomposition Method

Hydrazinium sulphate (N2H5)2SO4 reacts with the corresponding barium

salts (Jones 1975) in the aqueous medium to form the salts For example

(N2H5)2SO4 + Ba(NO3)2 rarr BaSO4 + 2 N2H5NO3 (18)

1213 Decomposition Method of Ammonium Salts

The reaction of stoichiometric quantities of N2H4H2O and the simple

ammonium salts (Soundararajan 1979) produces the hydrazinium salts with the

liberation of NH3

NH4X + N2H4H2O rarr N2H5X + NH3+ H2O (19)

where x = halides NO3- N3

- CH3COO - H2PO4 - HF2- HSO4

- etc

(NH4)2Y + 2N2H4H2O rarr (N2H5)2Y + 2NH3 + 2H2O (110)

where Y = SO42- C2O4

2- HPO42- S2O3

2- etc

This method is a heterogeneous reaction The salts N2H5HF2 (Patil et al

1979) and N2H5HSO4 (Vittal 1981) which could not be prepared by other methods

can be prepared by this method

The hydrazinium (+2) salts containing one molecule of a simple binary

acid are stable in solution The diacid salts however exist in the solid state and

undergo immediate hydrolysis when dissolved in water (Nesamani 1982) The

monoacid salts N2H4HA [N2H5A] are usually more soluble in water than the diacid

6 salts N2H42HA (N2H6A2) Again N2H5

+ salts are mostly hygroscopic and even some

of them are in liquid state (Patil et al 1980) while N2H62+ salts are not so with an

exception of N2H6(ClO4)22H2O which is highly hygroscopic

122 Salts of Hydrazine with Different Acids

1221 With Inorganic acids

Hydrazine hydrate reacts with halogen acids to give salts of the type

N2H5X and N2H6X2 under different reaction conditions (Patil et al 1979 Patil et al

1978) where X = Cl- Br- I- or F- When pure hydrazine reacts with nitric acid it

forms hydrazinium (+) nitrate and its crystal structure is reported (Grigoriev et al

2005) Hydrazine and nitrous acid undergo mutual destructive reaction In neutral

solution it is possible to obtain hydrazinium(+1) nitrite as colorless to yellowish

hygroscopic solid

Hydrazinium (+1) hydrogensulphate has been prepared (Patil and Vittal

1982) for the first time by the reaction of solid ammonium hydrogen sulphate with

hydrazine hydrate

2N2H6SO4 + BaCO3 rarr BaSO4 + (N2H5)2SO4 + H2O + CO2 (111)

Hydrazinium (+2) dithionate N2H6S2O6 can be prepared from

hydrazinium (+2) sulphate and barium dithionate Hydrazinium (+2) sulphamate is

prepared in a similar fashion from N2H6SO4 and Ba(SO3NH2)2

When SO2 gas is passed through a 11 aqueous solution of hydrazine

N2H5HSO3 is formed in less concentrated solution whereas (N2H5)2S2O5 is formed

in more concentrated solution no hydrazinium sulphate formation is observed

Earlier studies have reported the formation of dihydrazinium hydrazodisulphite

(HNSOON2H5)2 by the same reaction Bubbling SO2 into an alcoholic solution of

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

2 high heats of combustion They have nitrogen in -2 valence state Nitrogens natural

tendency however is towards zero valency (N equiv N) which gives off nearly six

times as much as energy as the N-N bond Thus tremendous amount of energy is

released not only during decomposition of N2H4 to N2 but also at the time of the

mixing with the oxidizer Hence they are used as fuels in rocket and spacecraft

powered engines As a strong reducing agent hydrazine is used for corrosion control

in boilers and hot water heating systems for metal plating and for reducing noble

metal catalysts and unsaturated bonds in organic compounds It is also an oxidizing

agent under suitable conditions with two active nucleophilic nitrogens and four

replaceable hydrogens It is the starting material for many derivatives among which

foaming agents for plastics antioxidants polymers polymer cross linking and chain

extending agents as well as biologically active pesticides herbicides plant growth

regulators and pharmaceuticals are important As it is a good complexing ligand

numerous complexes have been studied (Bottomley 1970 and Schmidt 1984) Many

heterocyclics are based on hydrazine with rings containing from 1 to 5 nitrogen

atoms as well as other hetero atoms The many advantageous properties of hydrazine

are exploited in the field of photographic chemicals and dyes New uses for

hydrazine derivatives are discovered daily

112 Basicity and Salt Forming Ability

As an Arrhenius base hydrazine is a weaker base than ammonia because

the more electronegative group NH2 has the - I effect on the lone pair of electron of

the neighbouring nitrogen making it less basic for protonation

NH3 + H2O rarr NH4+ + OH - Kb =18 X 10-5 (11)

N2H4 + H2O rarr N2H5 + + OH - Kb = 85 X 10-7 (12)

3

N2H5+ + H2O rarr N2H6

2+ + OH - Kb = 89 X 10-16 (13)

In principle it can form two series of salts with monobasic acids one

having the hydrazinium (+1) cation N2H5+ and the other hydrazinium(+2) cation

N2H62+ The basic ionization constants of hydrazine in water suggest that N2H6

2+

exists only in the solid state or in conc acid solutions The salts containing this

cation are extensively hydrolyzed in water to give highly acidic solutions containing

the N2H5+ ion

N2H62+ + H2O rarr N2H5

+ + H3O+ (14)

The divalent cation seems to violate Paulingrsquos adjacent charge rule

H3N+- NH3+ but is likely that this is in equilibrium with other tautomeric forms eg

H3N+- NH2H+The N2H5+ salts have been prepared with carboxylic acids and

numerous examples of them have been reported (Schmidt 1984) whereas the salts of

N2H62+ are limited (Starosta and Leciejewicz 2007 Starosta and Leciejewicz 2008)

12 TYPES OF HYDRAZINE SALTS

The hydrazinium salts are inorganic derivatives well-crystallized and

colorless compounds comparable to the corresponding ammonium salts The

reducing property and the lack of thermal stability of hydrazinium salts differentiate

them from ammonium salts

Hydrazine forms not only mono- and di acid salts of the types N2H4HA

N2H42HA where HA represents a simple mono-basic acid but also compounds of

the types 2N2H4H2B and N2H4H2B where H2B represents a dibasic acid The best

known of these are N2H4HA or 2N2H4H2B [N2H5A or (N2H5)2B] and N2H42HA or

4 N2H4H2B [N2H6A2 or N2H6B] and not N2H42H2B The N2H5

+ and N2H62+ salts are

generally referred to as hydrazinium(+1) and hydrazinium(+2) salts respectively

Even though N2H62+ salts are generally formed with strong acids double

salts of this cation with ammonium ion are also formed For example

(NH4)2N2H6(ClO4)4 and (NH4)2N2H6(SO4)2 (Frech et al 1993) salts have been

prepared and characterized Recently redetermination of hydrazinium (+2)

dichloride (N2H62+2Cl-) has been reported (Kruszynski and Trzesowska 2007) In

many cases the preparation of hydrazinium salts is very easy but in other cases

such as in the preparation of hydrazinium nitrates or perchlorates special

precautions are necessary to prevent unexpected explosions

It is interesting to note that a few hydrazine salts form hydrates eg

N2H5ClO405H2O N2H6X22H2O X = ClO4- Br- and I- It has been shown by IR

thermal and conductivity measurements that water in these compounds is partially

present as oxonium ion H3O+ and involved in hydrogen bonding with N2H4 (Patil et

al 1983) (N2H5)2SO3H2O (Patil et al 1980)

121 Methods of Preparation of Simple Hydrazinium Salts

1211 Acid -Base Neutralization Method

In this method the base is directly neutralized by the addition of the

corresponding acids in the aqueous medium The pH of the solution is an important

factor to get the type of salt desired The reactions are represented as given below

N2H4H2O + HA rarr N2H5A + H2O (15)

N2H4 H2O + 2HA rarr N2H6A2 + H2O (16)

N2H4 H2O + H2B rarr N2H6B + H2O (17)

5 where HA is a monobasic acid eg HCl CH3COOH HNO3 etc and H2B is a

dibasic acid eg H2SO4 H2C2O4 etcAcids like H2SO4 (Hudson et al 1967) and HF

(Patil et al 1979) react with N2H4H2O to form exclusively N2H62+ salts because of

their strong acidic nature and the low solubility of the resulting salts

1212 Double Decomposition Method

Hydrazinium sulphate (N2H5)2SO4 reacts with the corresponding barium

salts (Jones 1975) in the aqueous medium to form the salts For example

(N2H5)2SO4 + Ba(NO3)2 rarr BaSO4 + 2 N2H5NO3 (18)

1213 Decomposition Method of Ammonium Salts

The reaction of stoichiometric quantities of N2H4H2O and the simple

ammonium salts (Soundararajan 1979) produces the hydrazinium salts with the

liberation of NH3

NH4X + N2H4H2O rarr N2H5X + NH3+ H2O (19)

where x = halides NO3- N3

- CH3COO - H2PO4 - HF2- HSO4

- etc

(NH4)2Y + 2N2H4H2O rarr (N2H5)2Y + 2NH3 + 2H2O (110)

where Y = SO42- C2O4

2- HPO42- S2O3

2- etc

This method is a heterogeneous reaction The salts N2H5HF2 (Patil et al

1979) and N2H5HSO4 (Vittal 1981) which could not be prepared by other methods

can be prepared by this method

The hydrazinium (+2) salts containing one molecule of a simple binary

acid are stable in solution The diacid salts however exist in the solid state and

undergo immediate hydrolysis when dissolved in water (Nesamani 1982) The

monoacid salts N2H4HA [N2H5A] are usually more soluble in water than the diacid

6 salts N2H42HA (N2H6A2) Again N2H5

+ salts are mostly hygroscopic and even some

of them are in liquid state (Patil et al 1980) while N2H62+ salts are not so with an

exception of N2H6(ClO4)22H2O which is highly hygroscopic

122 Salts of Hydrazine with Different Acids

1221 With Inorganic acids

Hydrazine hydrate reacts with halogen acids to give salts of the type

N2H5X and N2H6X2 under different reaction conditions (Patil et al 1979 Patil et al

1978) where X = Cl- Br- I- or F- When pure hydrazine reacts with nitric acid it

forms hydrazinium (+) nitrate and its crystal structure is reported (Grigoriev et al

2005) Hydrazine and nitrous acid undergo mutual destructive reaction In neutral

solution it is possible to obtain hydrazinium(+1) nitrite as colorless to yellowish

hygroscopic solid

Hydrazinium (+1) hydrogensulphate has been prepared (Patil and Vittal

1982) for the first time by the reaction of solid ammonium hydrogen sulphate with

hydrazine hydrate

2N2H6SO4 + BaCO3 rarr BaSO4 + (N2H5)2SO4 + H2O + CO2 (111)

Hydrazinium (+2) dithionate N2H6S2O6 can be prepared from

hydrazinium (+2) sulphate and barium dithionate Hydrazinium (+2) sulphamate is

prepared in a similar fashion from N2H6SO4 and Ba(SO3NH2)2

When SO2 gas is passed through a 11 aqueous solution of hydrazine

N2H5HSO3 is formed in less concentrated solution whereas (N2H5)2S2O5 is formed

in more concentrated solution no hydrazinium sulphate formation is observed

Earlier studies have reported the formation of dihydrazinium hydrazodisulphite

(HNSOON2H5)2 by the same reaction Bubbling SO2 into an alcoholic solution of

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

3

N2H5+ + H2O rarr N2H6

2+ + OH - Kb = 89 X 10-16 (13)

In principle it can form two series of salts with monobasic acids one

having the hydrazinium (+1) cation N2H5+ and the other hydrazinium(+2) cation

N2H62+ The basic ionization constants of hydrazine in water suggest that N2H6

2+

exists only in the solid state or in conc acid solutions The salts containing this

cation are extensively hydrolyzed in water to give highly acidic solutions containing

the N2H5+ ion

N2H62+ + H2O rarr N2H5

+ + H3O+ (14)

The divalent cation seems to violate Paulingrsquos adjacent charge rule

H3N+- NH3+ but is likely that this is in equilibrium with other tautomeric forms eg

H3N+- NH2H+The N2H5+ salts have been prepared with carboxylic acids and

numerous examples of them have been reported (Schmidt 1984) whereas the salts of

N2H62+ are limited (Starosta and Leciejewicz 2007 Starosta and Leciejewicz 2008)

12 TYPES OF HYDRAZINE SALTS

The hydrazinium salts are inorganic derivatives well-crystallized and

colorless compounds comparable to the corresponding ammonium salts The

reducing property and the lack of thermal stability of hydrazinium salts differentiate

them from ammonium salts

Hydrazine forms not only mono- and di acid salts of the types N2H4HA

N2H42HA where HA represents a simple mono-basic acid but also compounds of

the types 2N2H4H2B and N2H4H2B where H2B represents a dibasic acid The best

known of these are N2H4HA or 2N2H4H2B [N2H5A or (N2H5)2B] and N2H42HA or

4 N2H4H2B [N2H6A2 or N2H6B] and not N2H42H2B The N2H5

+ and N2H62+ salts are

generally referred to as hydrazinium(+1) and hydrazinium(+2) salts respectively

Even though N2H62+ salts are generally formed with strong acids double

salts of this cation with ammonium ion are also formed For example

(NH4)2N2H6(ClO4)4 and (NH4)2N2H6(SO4)2 (Frech et al 1993) salts have been

prepared and characterized Recently redetermination of hydrazinium (+2)

dichloride (N2H62+2Cl-) has been reported (Kruszynski and Trzesowska 2007) In

many cases the preparation of hydrazinium salts is very easy but in other cases

such as in the preparation of hydrazinium nitrates or perchlorates special

precautions are necessary to prevent unexpected explosions

It is interesting to note that a few hydrazine salts form hydrates eg

N2H5ClO405H2O N2H6X22H2O X = ClO4- Br- and I- It has been shown by IR

thermal and conductivity measurements that water in these compounds is partially

present as oxonium ion H3O+ and involved in hydrogen bonding with N2H4 (Patil et

al 1983) (N2H5)2SO3H2O (Patil et al 1980)

121 Methods of Preparation of Simple Hydrazinium Salts

1211 Acid -Base Neutralization Method

In this method the base is directly neutralized by the addition of the

corresponding acids in the aqueous medium The pH of the solution is an important

factor to get the type of salt desired The reactions are represented as given below

N2H4H2O + HA rarr N2H5A + H2O (15)

N2H4 H2O + 2HA rarr N2H6A2 + H2O (16)

N2H4 H2O + H2B rarr N2H6B + H2O (17)

5 where HA is a monobasic acid eg HCl CH3COOH HNO3 etc and H2B is a

dibasic acid eg H2SO4 H2C2O4 etcAcids like H2SO4 (Hudson et al 1967) and HF

(Patil et al 1979) react with N2H4H2O to form exclusively N2H62+ salts because of

their strong acidic nature and the low solubility of the resulting salts

1212 Double Decomposition Method

Hydrazinium sulphate (N2H5)2SO4 reacts with the corresponding barium

salts (Jones 1975) in the aqueous medium to form the salts For example

(N2H5)2SO4 + Ba(NO3)2 rarr BaSO4 + 2 N2H5NO3 (18)

1213 Decomposition Method of Ammonium Salts

The reaction of stoichiometric quantities of N2H4H2O and the simple

ammonium salts (Soundararajan 1979) produces the hydrazinium salts with the

liberation of NH3

NH4X + N2H4H2O rarr N2H5X + NH3+ H2O (19)

where x = halides NO3- N3

- CH3COO - H2PO4 - HF2- HSO4

- etc

(NH4)2Y + 2N2H4H2O rarr (N2H5)2Y + 2NH3 + 2H2O (110)

where Y = SO42- C2O4

2- HPO42- S2O3

2- etc

This method is a heterogeneous reaction The salts N2H5HF2 (Patil et al

1979) and N2H5HSO4 (Vittal 1981) which could not be prepared by other methods

can be prepared by this method

The hydrazinium (+2) salts containing one molecule of a simple binary

acid are stable in solution The diacid salts however exist in the solid state and

undergo immediate hydrolysis when dissolved in water (Nesamani 1982) The

monoacid salts N2H4HA [N2H5A] are usually more soluble in water than the diacid

6 salts N2H42HA (N2H6A2) Again N2H5

+ salts are mostly hygroscopic and even some

of them are in liquid state (Patil et al 1980) while N2H62+ salts are not so with an

exception of N2H6(ClO4)22H2O which is highly hygroscopic

122 Salts of Hydrazine with Different Acids

1221 With Inorganic acids

Hydrazine hydrate reacts with halogen acids to give salts of the type

N2H5X and N2H6X2 under different reaction conditions (Patil et al 1979 Patil et al

1978) where X = Cl- Br- I- or F- When pure hydrazine reacts with nitric acid it

forms hydrazinium (+) nitrate and its crystal structure is reported (Grigoriev et al

2005) Hydrazine and nitrous acid undergo mutual destructive reaction In neutral

solution it is possible to obtain hydrazinium(+1) nitrite as colorless to yellowish

hygroscopic solid

Hydrazinium (+1) hydrogensulphate has been prepared (Patil and Vittal

1982) for the first time by the reaction of solid ammonium hydrogen sulphate with

hydrazine hydrate

2N2H6SO4 + BaCO3 rarr BaSO4 + (N2H5)2SO4 + H2O + CO2 (111)

Hydrazinium (+2) dithionate N2H6S2O6 can be prepared from

hydrazinium (+2) sulphate and barium dithionate Hydrazinium (+2) sulphamate is

prepared in a similar fashion from N2H6SO4 and Ba(SO3NH2)2

When SO2 gas is passed through a 11 aqueous solution of hydrazine

N2H5HSO3 is formed in less concentrated solution whereas (N2H5)2S2O5 is formed

in more concentrated solution no hydrazinium sulphate formation is observed

Earlier studies have reported the formation of dihydrazinium hydrazodisulphite

(HNSOON2H5)2 by the same reaction Bubbling SO2 into an alcoholic solution of

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

4 N2H4H2B [N2H6A2 or N2H6B] and not N2H42H2B The N2H5

+ and N2H62+ salts are

generally referred to as hydrazinium(+1) and hydrazinium(+2) salts respectively

Even though N2H62+ salts are generally formed with strong acids double

salts of this cation with ammonium ion are also formed For example

(NH4)2N2H6(ClO4)4 and (NH4)2N2H6(SO4)2 (Frech et al 1993) salts have been

prepared and characterized Recently redetermination of hydrazinium (+2)

dichloride (N2H62+2Cl-) has been reported (Kruszynski and Trzesowska 2007) In

many cases the preparation of hydrazinium salts is very easy but in other cases

such as in the preparation of hydrazinium nitrates or perchlorates special

precautions are necessary to prevent unexpected explosions

It is interesting to note that a few hydrazine salts form hydrates eg

N2H5ClO405H2O N2H6X22H2O X = ClO4- Br- and I- It has been shown by IR

thermal and conductivity measurements that water in these compounds is partially

present as oxonium ion H3O+ and involved in hydrogen bonding with N2H4 (Patil et

al 1983) (N2H5)2SO3H2O (Patil et al 1980)

121 Methods of Preparation of Simple Hydrazinium Salts

1211 Acid -Base Neutralization Method

In this method the base is directly neutralized by the addition of the

corresponding acids in the aqueous medium The pH of the solution is an important

factor to get the type of salt desired The reactions are represented as given below

N2H4H2O + HA rarr N2H5A + H2O (15)

N2H4 H2O + 2HA rarr N2H6A2 + H2O (16)

N2H4 H2O + H2B rarr N2H6B + H2O (17)

5 where HA is a monobasic acid eg HCl CH3COOH HNO3 etc and H2B is a

dibasic acid eg H2SO4 H2C2O4 etcAcids like H2SO4 (Hudson et al 1967) and HF

(Patil et al 1979) react with N2H4H2O to form exclusively N2H62+ salts because of

their strong acidic nature and the low solubility of the resulting salts

1212 Double Decomposition Method

Hydrazinium sulphate (N2H5)2SO4 reacts with the corresponding barium

salts (Jones 1975) in the aqueous medium to form the salts For example

(N2H5)2SO4 + Ba(NO3)2 rarr BaSO4 + 2 N2H5NO3 (18)

1213 Decomposition Method of Ammonium Salts

The reaction of stoichiometric quantities of N2H4H2O and the simple

ammonium salts (Soundararajan 1979) produces the hydrazinium salts with the

liberation of NH3

NH4X + N2H4H2O rarr N2H5X + NH3+ H2O (19)

where x = halides NO3- N3

- CH3COO - H2PO4 - HF2- HSO4

- etc

(NH4)2Y + 2N2H4H2O rarr (N2H5)2Y + 2NH3 + 2H2O (110)

where Y = SO42- C2O4

2- HPO42- S2O3

2- etc

This method is a heterogeneous reaction The salts N2H5HF2 (Patil et al

1979) and N2H5HSO4 (Vittal 1981) which could not be prepared by other methods

can be prepared by this method

The hydrazinium (+2) salts containing one molecule of a simple binary

acid are stable in solution The diacid salts however exist in the solid state and

undergo immediate hydrolysis when dissolved in water (Nesamani 1982) The

monoacid salts N2H4HA [N2H5A] are usually more soluble in water than the diacid

6 salts N2H42HA (N2H6A2) Again N2H5

+ salts are mostly hygroscopic and even some

of them are in liquid state (Patil et al 1980) while N2H62+ salts are not so with an

exception of N2H6(ClO4)22H2O which is highly hygroscopic

122 Salts of Hydrazine with Different Acids

1221 With Inorganic acids

Hydrazine hydrate reacts with halogen acids to give salts of the type

N2H5X and N2H6X2 under different reaction conditions (Patil et al 1979 Patil et al

1978) where X = Cl- Br- I- or F- When pure hydrazine reacts with nitric acid it

forms hydrazinium (+) nitrate and its crystal structure is reported (Grigoriev et al

2005) Hydrazine and nitrous acid undergo mutual destructive reaction In neutral

solution it is possible to obtain hydrazinium(+1) nitrite as colorless to yellowish

hygroscopic solid

Hydrazinium (+1) hydrogensulphate has been prepared (Patil and Vittal

1982) for the first time by the reaction of solid ammonium hydrogen sulphate with

hydrazine hydrate

2N2H6SO4 + BaCO3 rarr BaSO4 + (N2H5)2SO4 + H2O + CO2 (111)

Hydrazinium (+2) dithionate N2H6S2O6 can be prepared from

hydrazinium (+2) sulphate and barium dithionate Hydrazinium (+2) sulphamate is

prepared in a similar fashion from N2H6SO4 and Ba(SO3NH2)2

When SO2 gas is passed through a 11 aqueous solution of hydrazine

N2H5HSO3 is formed in less concentrated solution whereas (N2H5)2S2O5 is formed

in more concentrated solution no hydrazinium sulphate formation is observed

Earlier studies have reported the formation of dihydrazinium hydrazodisulphite

(HNSOON2H5)2 by the same reaction Bubbling SO2 into an alcoholic solution of

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

5 where HA is a monobasic acid eg HCl CH3COOH HNO3 etc and H2B is a

dibasic acid eg H2SO4 H2C2O4 etcAcids like H2SO4 (Hudson et al 1967) and HF

(Patil et al 1979) react with N2H4H2O to form exclusively N2H62+ salts because of

their strong acidic nature and the low solubility of the resulting salts

1212 Double Decomposition Method

Hydrazinium sulphate (N2H5)2SO4 reacts with the corresponding barium

salts (Jones 1975) in the aqueous medium to form the salts For example

(N2H5)2SO4 + Ba(NO3)2 rarr BaSO4 + 2 N2H5NO3 (18)

1213 Decomposition Method of Ammonium Salts

The reaction of stoichiometric quantities of N2H4H2O and the simple

ammonium salts (Soundararajan 1979) produces the hydrazinium salts with the

liberation of NH3

NH4X + N2H4H2O rarr N2H5X + NH3+ H2O (19)

where x = halides NO3- N3

- CH3COO - H2PO4 - HF2- HSO4

- etc

(NH4)2Y + 2N2H4H2O rarr (N2H5)2Y + 2NH3 + 2H2O (110)

where Y = SO42- C2O4

2- HPO42- S2O3

2- etc

This method is a heterogeneous reaction The salts N2H5HF2 (Patil et al

1979) and N2H5HSO4 (Vittal 1981) which could not be prepared by other methods

can be prepared by this method

The hydrazinium (+2) salts containing one molecule of a simple binary

acid are stable in solution The diacid salts however exist in the solid state and

undergo immediate hydrolysis when dissolved in water (Nesamani 1982) The

monoacid salts N2H4HA [N2H5A] are usually more soluble in water than the diacid

6 salts N2H42HA (N2H6A2) Again N2H5

+ salts are mostly hygroscopic and even some

of them are in liquid state (Patil et al 1980) while N2H62+ salts are not so with an

exception of N2H6(ClO4)22H2O which is highly hygroscopic

122 Salts of Hydrazine with Different Acids

1221 With Inorganic acids

Hydrazine hydrate reacts with halogen acids to give salts of the type

N2H5X and N2H6X2 under different reaction conditions (Patil et al 1979 Patil et al

1978) where X = Cl- Br- I- or F- When pure hydrazine reacts with nitric acid it

forms hydrazinium (+) nitrate and its crystal structure is reported (Grigoriev et al

2005) Hydrazine and nitrous acid undergo mutual destructive reaction In neutral

solution it is possible to obtain hydrazinium(+1) nitrite as colorless to yellowish

hygroscopic solid

Hydrazinium (+1) hydrogensulphate has been prepared (Patil and Vittal

1982) for the first time by the reaction of solid ammonium hydrogen sulphate with

hydrazine hydrate

2N2H6SO4 + BaCO3 rarr BaSO4 + (N2H5)2SO4 + H2O + CO2 (111)

Hydrazinium (+2) dithionate N2H6S2O6 can be prepared from

hydrazinium (+2) sulphate and barium dithionate Hydrazinium (+2) sulphamate is

prepared in a similar fashion from N2H6SO4 and Ba(SO3NH2)2

When SO2 gas is passed through a 11 aqueous solution of hydrazine

N2H5HSO3 is formed in less concentrated solution whereas (N2H5)2S2O5 is formed

in more concentrated solution no hydrazinium sulphate formation is observed

Earlier studies have reported the formation of dihydrazinium hydrazodisulphite

(HNSOON2H5)2 by the same reaction Bubbling SO2 into an alcoholic solution of

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

6 salts N2H42HA (N2H6A2) Again N2H5

+ salts are mostly hygroscopic and even some

of them are in liquid state (Patil et al 1980) while N2H62+ salts are not so with an

exception of N2H6(ClO4)22H2O which is highly hygroscopic

122 Salts of Hydrazine with Different Acids

1221 With Inorganic acids

Hydrazine hydrate reacts with halogen acids to give salts of the type

N2H5X and N2H6X2 under different reaction conditions (Patil et al 1979 Patil et al

1978) where X = Cl- Br- I- or F- When pure hydrazine reacts with nitric acid it

forms hydrazinium (+) nitrate and its crystal structure is reported (Grigoriev et al

2005) Hydrazine and nitrous acid undergo mutual destructive reaction In neutral

solution it is possible to obtain hydrazinium(+1) nitrite as colorless to yellowish

hygroscopic solid

Hydrazinium (+1) hydrogensulphate has been prepared (Patil and Vittal

1982) for the first time by the reaction of solid ammonium hydrogen sulphate with

hydrazine hydrate

2N2H6SO4 + BaCO3 rarr BaSO4 + (N2H5)2SO4 + H2O + CO2 (111)

Hydrazinium (+2) dithionate N2H6S2O6 can be prepared from

hydrazinium (+2) sulphate and barium dithionate Hydrazinium (+2) sulphamate is

prepared in a similar fashion from N2H6SO4 and Ba(SO3NH2)2

When SO2 gas is passed through a 11 aqueous solution of hydrazine

N2H5HSO3 is formed in less concentrated solution whereas (N2H5)2S2O5 is formed

in more concentrated solution no hydrazinium sulphate formation is observed

Earlier studies have reported the formation of dihydrazinium hydrazodisulphite

(HNSOON2H5)2 by the same reaction Bubbling SO2 into an alcoholic solution of

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

7 hydrazine hydrate precipitates (N2H5)2SO3 which can also be prepared (Patil et al

1980) by the heterogeneous reaction between solid ammonium sulphite and

hydrazine hydrate The reaction of hydrazine with a mixture of SO2 and CO2 results

in dual substitution on both nitrogen atoms to give a mixed sulphinate carbazate

N2H5OOSNHNHCOON2H5 On passing SO3 into an excess anhydrous hydrazine it

gives the hydrazinium salt of hydrazinosulphuric acid N2H3SO3N2H5 The

hydrazinium thiocyanate has been prepared from solid ammonium thiocyanate and

hydrazine hydrate (Patil et al 1980)

The latter salt also forms 11 adduct with phosphoric acid N2H5H2PO4

H3PO4 The salts N2H5H2PO4 and (N2H5)2HPO4 have been prepared by the reaction

between the corresponding ammonium phosphate and hydrazine hydrate and

characterized (Patil et al 1978) by chemical analysis and IR spectra(νN-N = 980 cm-1)

NH4 H2PO4 (S) + N2H4H2O rarr N2H5H2PO4 (S) + H2O + NH3 (112)

(NH4)2HPO4 (S) + 2N2H4H2O rarr (N2H5)2HPO4 (S) + 2H2O + 2NH3 (113)

The crystal structures of N2H5H2PO4 and N2H6(H2PO4)2 have also been

studied (Liminga 1965 and Liminga 1966)

Trihydrazinium (+1) dihydrogentriphosphate (N2H5)3H2P3O10

and tetra hydrazinium (+1) tetrametaphosphate (N2H5)4P4O12 were prepared

as anhydrous salts whereas tetrahydrazinium(+1) pyrophosphate (N2H5)4P2O7H2O

and octa meta phosphate (N2H5)8P8O24 H2O were obtained as hydrates

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

8

1222 With carboxylic acids

The hydrazinium salts of a number of aliphatic mono and di carboxylic

acids and aromatic mono di tri and tetra carboxylic acids have been reported

Hydrazinium (+1) formate (hydrazinium monoformate) though reported

(Schmidt 1984) to have been prepared from formic acid and hydrazine hydrate has

not been well characterized The preparation of hydrazinium(+1) acetate has

been reported by the decomposition of ammonium acetate by hydrazine hydrate

(Patil et al 1980) The dihydrazinium(+1) oxalate (N2H5)2C2O4 has been repeatedly

studied because it is a well crystallized solid and also forms double salts with other

cations The metathetical reaction of ammonium oxalate monohydrate with excess of

N2H4H2O gives (COON2H5)2N2H4 which begins to lose solvated hydrazine at 90

degC and then melts at 153 degC (Patil et al 1979 and Patil et al 1978) The

hydrazinium(+1) oxalate can be obtained by treating hydrazinium(+2) oxalate in

aqueous solution with N2H4H2O until the solution becomes permanently alkaline

The N2H5HC2O4 has been prepared by mixing hot aqueous solutions whereas

(N2H5)2C2O4 has been prepared in cold condition Efforts to crystallize the latter

from hot solution always resulted in the former only

Numerous salts of hydrazine with several organic acids are available in

the literature Some of the common salts are N2H5C7H4NO3S (Banerjee et al 2006)

hydrazinium propionate butyrate(Schmidt 1984) Moreover hydrazinium salts of a

series of dicarboxylic acids like hydrazinium hydrogenmalonate hydrogenglutarate

hydrogenadipate and dihydrazinium succinate (Sivasankar 1994) higher

homologous dicarboxylic acids viz pimelic suberic azelaic alpha keto glutaric and

iminodiacetic malic aspartic and glutamic acids (Yasodhai and Govindarajan

1999) oxydiacetic acid (Yasodhai and Govindarajan 2000) heteroaromatic acids

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

9 like pyridine dicarboxylic acids (Saravanan and Govindarajan 2003) and pyrazine

carboxylic acids (Premkumar et al 2003) have been prepared by the acid-base

neutralisation method and characterized Hydrazine also forms salts with aromatic

carboxylic acids like benzoic salicylic phthalic acids (Kuppusamy 1995) trimesic

trimellitic hemimellitic and pyromellitic acids (Vairam and Govindarajan 2004)

naphthoic hydroxy naphthoic and naphthoxy acetic acids (Arunadevi 2009)

Simple hydrazinium salts have numerous applications (Schmidt 1984)

such as a source of anhydrous hydrazine additives in propellants drugs to treat

cancer and Hodgkinrsquos disease explosives(Schimidt 1984) and as ligands to prepare

metal hydrazinehydrazinium complexes(Govindarjan et al 1986 Govindarajan et al

1986a and Yasodhai et al 1999) A few of them are also used as flame retardants

(Patil et al 1980 and Patil et al 1981) and proton conductors (Chandra and Singh

1983)

13 THERMAL PROPERTIES OF HYDRAZINE AND ITS SIMPLE

SALTS

Heating of hydrazine salts in most cases causes decomposition A very

few of them are stable at their melting points The diacid salts on heating decompose

to yield the monoacid salts as intermediates

N2H42HA rarr N2H4HA + HA (114)

The hydrazinium salts of the type N2H5X [X = Cl- Br- I- 05SO42-

H2PO4-] decompose exothermally in air to the corresponding ammonium salts with

the evolution of ammonia and nitrogen (Patil et al 1979 and Jasim 1988) Some of

the hydrazinium salts like N2H5N3 (Patil et al 1979) N2H5HF2 (Patil et al 1979) and

N2H5F (Soundararajan 1979) do not decompose exothermally but volatilize under

the conditions employed The simultaneous TG DTA and EGA thermolysis of

hydrazinium sulphate has also been studied (Jasim 1988) The hydrazine salts such

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

10 as hydrazinium perchlorate and nitrate are used as high energy oxidisers in

propellants Hence thermal decomposition of these compounds has been

investigated in detail (Pai Verneker et al 1976 Breisacher et al 1972 and Patil et al

1980) Thermal studies on hydrazinium sulphite hydrate (Patil et al 1980) shows that

it melts before decomposition In the same report an interesting and quantitative

conversion of hydrazinium thiocyanate to thiosemicarbazide has been discussed

The thermal decomposition of hydrazinium carboxylates is more

interesting The hydrazinium formate hemihydrate (Sivasankar and Govindarajan

1995) melts before undergoing endothermic decomposition to gaseous products The

hydrazinium acetate also follows the same pattern of thermal decomposition as

already reported (Patil et al 1980) The thermal decomposition of hydrazinium

hydrogen oxalate and dihydrazinium oxalate has been investigated in detail (Udupa

1982 Gajapathy et al 1983) An interesting behaviour in their thermal properties is

that dihydrazinium salt is converted to monohydrazinium salt after melting and

losing one N2H4 molecule

The thermal decomposition of hydrazinium dicarboxylates of malonic

succinic glutaric adipic acid (Yasodhai and Govindarajan 1999) and phthalic acids

has been studied by TG-DTA method All of them except terephthalate and

isophthalates decompose to gaseous products endothermally (Sivasankar 1994)

Terephthalate and isophthalate salts (Kuppusamy et al 1995) undergo exothermic

and endothermic decompositions Hemimellitate trimellitate trimesate and

pyromellitate salts undergo strong exothermic decomposition with the formation of

carbon residue as the final product (Vairam and Govindarajan 2004)

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

11

14 METAL HYDRAZINE COMPLEXES

The hydrazine does not frequently act as a reducing agent in reactions

with transition metals but acts as a ligand to form complexes This broad area of

hydrazine complexes has been reviewed earlier (Bottomley 1970 Dilworth 1976)

141 Hydrazine as a Ligand

Hydrazine like other polybasic ligands offers the possibility of several

different types of coordination behavior towards metal ions It can of course

function as a monodentate ligand but may also serve as either a bridging or chelating

bidentate ligand Although numerous examples of both monodentate and bridging

hydrazine have been demonstrated crystallographically no verified examples

(with the possible exception of (i-pro)4MN2H4 M = Ti or Zr) of chelatively bound

hydrazine have been reported

Monoprotonated hydrazine hydrazinium cation (N2H5+) still retains a

basic site and is capable of coordination It is potentially a monodentate ligand and

complexes containing it are known The donor abilities of hydrazine from

complexometric titration (Bisacchi and Goldwhite 1970) are shown in the order

N2H4 gt CH3NHNH2 gt C2H5NHNH2 gt (CH3)2NNH2 (115)

A number of complexes with substituted hydrazines have been reviewed

by Heaton et al 1996

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

12

142 Synthesis of Metal Hydrazine Complexes

1421 Reactions of Hydrazine and its Salts with Metal

The high dielectric constant of anhydrous hydrazine suggests that it would

be a moderate solvent for many ionic compounds It is not altogether unexpected to

find that hydrazine salts when dissolved in hydrazine or hydrazine hydrate behave as

acids Thus metals like Mg Fe Co Ni Zn or Cd dissolved in a solution containing

hydrazine hydrate and hydrazinium or ammonium salts liberate hydrogen (Patil et al

1982)

M + 2N2H5X rarr M(N2H4)2X2+ H2 (116)

where X = 05 SO42- 05 C2O4

2- N3- ClO4

- etc

Some mixed metal oxalate derivatives such as MFe2(C2O4)3(N2H4)x (M =

Mg Mn Co Ni or Zn x = 5 and 6 ) and MgFe2(N2O2)3(N2H4)5 (Gajapathy 1982)

have been synthesized using the above procedure The complex (N2H5)2Mg(SO4)2

has been prepared by the reaction of magnesium powder and ammonium sulphate in

the presence of hydrazine hydrate (Patil

et al 1981)

1422 Reactions of Hydrazine with Metal Salts

The insoluble complexes M(N2H4)2X2 (M = Mn Co Ni Zn or Cd and X

= Cl- Br- I- 05SO42- NCS- HCOO- CH3COO- 05C2O4

2- H2NCH2COO-

HOCH2COO- etc) (Srivastava et al 1980 House and Vandenbrook 1989 House and

Vandenbrook 1990 Anagnostopoulos et al 1979 Ravindranathan and Patil 1983 and

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

13 Mahesh and Patil 1986) are the usual products of reaction between hydrazine

hydrate and first row transition metal salts

The tris-hydrazine complexes M(N2H4)3X2(X= 05 SO42- 05SO3

-

05S2O3- NO3

- etc) (Anagnostopoulos and Nicholls 1976 and Athavale and

Padmamabha Iyer 1967) have been prepared by the reaction between the transition

metal salts and hydrazine hydrate The tris-hydrazine metal glycinates and glycolates

M(XCH2COO)2(N2H4)3(X = NH2- or OH- and M = Mn Co Ni Zn or Cd) have

been prepared (Sivasankar and Govindarajan 1994) by mixing the metal nitrate

hydrates and a mixture of the acid and excess hydrazine hydrate The copper (II)

complex however is particularly difficult to isolate from aqueous solution because

of its ease of reduction Synthesis of bis(hydrazine) complexes

[Fe(RNHNH2)2PPh(OEt)24](Albertin et al 2001) was achieved by reacting

bis(nitrile)complex [Fe(CH3CN)2PPh(OEt)24](BPh4)2 with an excess of hydrazine

Also with the triethyl phosphate complex [Fe(CH3CN)2P(OEt)34](BPh4)2 as a

precursor the reaction with NH2NH2 gave the new nitrile-hydrazine

[Fe(NH2NH2)(CH3CN)2P(OEt)33](BPh4)2 derivative

1423 Reactions of Hydrazinium Salts with Metal Salts

The hydrazinum salts such as N2H6BeF4 N2H6F2 N2H5F N2H42HF

N2H5Cl N2H4HCl N2H42HCl N2H5Br N2H6SO4 (N2H5)2SO4 (N2H5)2C2O4

(N2H5)2H2EDTA N2H3COON2H5 N2H5NCS etc react directly with transition

metal salts to form normally hydrazinium(+1) metal complexes (Tedenac et al 1971

Satpathy and Sahoo 1970 Bukovec and Golic 1976 Kumar et al 1991 Cheng et al

1977 Reiff et al 1977 Witteveen and Reedijk 1973 Witteveen and Reedijk 1974

Nieuwpoort and Reedijk 1973 Govindarajan et al 1986 Gajapathy et al 1983

Saravanan et al 1994) or hydrazine adducts of the corresponding metal salts

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

14 (Sivasankar and Govindarajan 1994 Patil et al 1983 and Sivasankar and

Govindarajan 1995)

The hydrazinium (+2) metal complexes have also been isolated and

studied (Glavic et al 1975 Slivnik et al 1968 Frlec et al 1980) The hydrazinium

(+1) lanthanide metal sulphate complexes have been prepared by the reaction

between the lanthanide salts and N2H6SO4 and studied systematically (Bukovec and

Miliev 1987 and Govindarajan et al 1986)

1424 Reactions of Hydrazine Hydrate and the Acid Mixture with Metal

Salts

Instead of hydrazinium salts the mixture of hydrazine hydrate and the

acid of the corresponding anion can be added to the metal salt solution which

precipitates the complexes containing bidentate bridging hydrazine N2H5+ or

N2H62+ This method is suitable when the particular hydrazinium salts cannot be

prepared in the solid form A report describes the preparation of MX(N2H4)2 (M =

Co Ni Zn or Cd X = malonate or succinate) complexes by adding a mixture of

hydrazine hydrate and the acids to the metal nitrate hydrates (Sivasankar and

Govindarajan 1994)

The complexes of propionate M(CH3CH2COO)2(N2H4)2 (M = Mn Co

Ni Zn or Cd) and M13Co23(CH3CH2COO)2(N2H4)2 (M = Mg Mn Ni Zn or Cd)

have been prepared by this method The N2H62+ containing complexes like

N2H6SbF5 (Ballard et al 1976) N2H6CrF5H2O (Bukovec 1974) have been prepared

by adding the mixture of 40 HF and N2H4H2O to CrF3 in the aqueous medium

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

15

1425 Reactions of Hydrazinium Salt with Metal Salts in the Presence

of Excess Acid

This method is suitable to prepare the complexes in acidic pH so that

N2H5+ or N2H6

2+ cation containing complexes can be obtained For example

N2H5CuCl3 (N2H5)2CuCl42H2O and (N2H5)2Cu3Cl6 complexes (Brown et al 1979)

have been prepared by adding 3M HCl and N2H6Cl2 mixture to the aqueous solution

of CuCl22H2O under different conditions Under this condition of acidic pH the

reduction of Cu(II) is also prevented The complexes of the type

(N2H5)Ln(SO4)2H2O (Ln = La Ce Pr Nd Sm) have been prepared (Govindarajan

et al 1986) by this technique The N2H6FeF5 has been synthesized from metallic Fe

HF and aqueous N2H6F2 (Hanzel et al 1977 and Hanzel et al 1974) A number of

N2H62+ containing metal complexes with fluoride anion have been prepared by this

method in which metal fluorides react with a mixture of HF and N2H6F2 in the

aqueous medium (Slivnik 1976 Frlec et al 1981 and Chakravorti and Pandit 1974)

The hydrazinium formato and acetato complexes (N2H5)2M(XCOO)4 (X = H or

CH3 M= Co Ni or Zn) have been prepared (Sivasankar 1994 and Sivasankar and

Govindarajan 1995) by the reaction of metal nitrate hydrates with the corresponding

hydrazinium salts and acid mixture

1426 Reactions of Hydrazine Carboxylate Complexes with Acids

Whenever it is not possible to prepare hydrazinium metal complexes with

particular anion the same can be prepared conveniently by decomposing

hydrazinium metal hydrazine carboxylates with dilute acids of the corresponding

anion For example (N2H5)2M(NCS)42H2O (M = Co or Ni) complexes have been

prepared (Kumar et al 1991) by adding freshly prepared solid

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

16 N2H5M(N2H3COO)3H2O to dilute thiocyanic acid in small portions while

maintaining the reaction temperature around 0degC The (N2H5)2MnF4

(N2H5)2MCl42H2O (M = Co or Ni) (Kumar et al 1991) and (N2H5)UO2(CH3COO)3

complexes have been prepared by the same procedure

In spite of a number of methods described for the preparation of the

complexes it is not possible to detail all the possibilities as it is still a growing field

For example some complexes have been prepared in non-aqueous medium and

(N2H5)2UF6 has been prepared by the reaction between UF6 and N2H5F in anhydrous

hydrazine (Glavic and Slivnik 1970) The lanthanide hydrazine complexes with

anions like halides carbonate nitrate sulphate perchlorate acetate oxalate

(Schmidt 1984) and squarate(Vairam and Govindarajan 2006) have been prepared

by the addition of hydrazine hydrate to the metal salts in an aqueous or alcoholic

medium

15 THERMAL REACTIVITY

Thermal reactivity of the complexes varies from explosion rarr deflagration

rarr decomposition depending upon the anion Transition metal perchlorate nitrate

and azide hydrazines are primarily explosives non-transition metal (Li+ Mg2+ Al3+)

perchlorate nitrate and azide hydrazines and transition metal oxalate sulphite and

hydrazine carboxylate hydrazine complexes deflagrate and the rest simply

decompose with the loss of hydrazine The deflagrating nature of metal hydrazines

has been used in the preparation of ferrites (Gajapathy and Patil 1983) and cobaltites

(Ravindranathan et al 1987) It is rather surprising that thermolysis of

Mg(N3)2(N2H4)2 gave a blue coloured residue which showed a strong IR absorption

at 2100 cm-1 characteristic of molecular nitrogen The composition of the residue has

been fixed as Mg(NH2)2N2 by chemical analysis and TG studies (Patil et al 1982)

The tris-hydrazine complexes are considerably less stable both thermally and in air

than the corresponding bis- hydrazine complexes The complexes

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

17 M(XCH2COO)2(N2H4)3 (X = NH2

- or OH- and M = Mn Co Ni Zn or Cd)

decompose violently above 200 degC in an exothermic single step to form metal

powders (Sivasankar and Govindarajan 1994) Thus thermal properties of the

complexes differ depending on the composition the metal ion and type of the anion

the coordination mode of hydrazine and the atmosphere used in the experiments

151 Thermal Decomposition of Metal Hydrazine Complexes

Thermal decomposition of metal hydrazine complexes with a variety of

anions such as halides NCS- (Vittal 1981) NO3- and N3

- (Patil et al 1982) have been

studied Depending upon the anion the decomposition path changes dramatically

(violently) giving mostly metal oxides as the final residue whereas hydrazine

complexes M(N2H4)nX2 (Patil et al 1981 Glavic et al 1977 Glavic et al 1979 and

Glavic et al 1980 ) to MX2 MOX2 MO M2O3 or M Thermal reactivity of

MFe2(C2O4)3(N2H4)x (Patil et al 1983) (M = Mg Co Ni or Zn and x = 5 or 6 ) and

MFe2(N2H4)5(C2O4)3 (Gajapathy 1982) has been reported and these complexes

decompose at low temperature to give ferrites as the final product Preparation and

thermal reactivity of MgC2O4(N2H4)2 (Patil et al 1982) have also been reported

Thermal decomposition of metal carboxylate hydrazines are more

interesting due to their easier combustibility For example metal hydrazine formate

(Ravidranathan and Patil 1983) acetate (Mahesh and Patil 1986) propionate

chloroacetate glycinate and glycolate (Sivasankar 1994) oxalate (Patil et al 1982)

malonate and succinate (Sivasankar and Govindarajan 1994) benzoate salicylate

(Kuppusamy 1995) trimellitate(Vairam et al 2010) and pyromellitate(Vairam et al

2010a) complexes have been studied by simultaneous DTA-TG-DTG

thermoanalytical method These complexes have been reported to decompose at

lower temperatures than their non-carboxylate counterparts Moreover the oxalate

complexes exhibit autocatalytic decomposition This behaviour has been attributed

to the simultaneous exothermic decomposition of hydrazine and metal salt (Patil et

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

18 al 1982) This phenomenon has been made use of in the preparation of fine particle

ferrites (Gajapathy and Patil 1983) and cobaltites (Patil et al 1983) by the low

temperature decomposition of M13Fe23(C2O4)(N2H4)2 (M = Mg Mn Co Ni or Zn)

and M13Co23(C2O4)(N2H4)2 (M = Mg or Ni) respectively Large surface area CeO2

has been prepared by the thermal decomposition of cerium oxalate hydrazine

complex The thermal behaviour of metal maleate and fumarate hydrazine

complexes have also been reported (Govindarajan et al 1995) The decomposition of

nickel hydrazine glycinate complexes (Sivasankar 1994) have been reported to be

violently exothermic and lead to explosion if the samples are heated in bulk They

give metal powder as the final product even in air unusually Metal (Co Ni and Zn)

hydrazine phthalate complexes produce metal powder and benzoate isophthalate

and terephthalate complexes the oxides as residue (Kuppusamy 1995)

Metal hydrazine carboxylates decompose in air at a low temperature (75-

200degC) to yield fine particle oxide materials Thermal studies on

M(N2H3COO)2nH2O (M = Ca Mg Mn Fe Co Ni Zn or Cu n = 0 05 1 2 3)

are carried out extensively in air or inert atmosphere (Ravidranathan and Patil 1985

Macek and Rahten 1989 Macek and Rahten 1993 Braibanti et al 1967 Manoharan

and Patil 1989) The thermal property of Nd(N2H3COO)33H2O in an inert

atmosphere (Macek and Rahten 1989 Macek and Rahten 1993) the synthesis of

La(N2H3COO)32H2O and thermal reactivity of Ln(N2H3COO)33H2O(Ln = Ce Pr

Nd Sm Eu Gd Tb Dy Ho Er Yb or Y) and UO2(N2H3COO)2N2H4H2O

(Mahesh et al 1986) have been reported already The decomposition is autocatalytic

and accompanied by swelling due to the evolution of large amounts of gases like

NH3 H2O H2 and CO2 The preparation of γ-Fe2O3 and Co doped γ-Fe2O3 the

commonly used recording material has been achieved by the thermal decomposition

of iron hydrazine carboxylates in a single step Similarly ultra fine ferrites and fine

particle cobaltites have been obtained at very low temperatures by the thermal

decompositioncombustion of solid solution precursors (Ravindranathan and Patil

1987 Arunadevi et al 2009)

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

19 The thermal decomposition of metal sulphite hydrazine hydrates

(Budkuley 1987) has been reported The decomposition of mixed metal sulphite

hydrazine occurs at low temperature due to high exothermicity of hydrazine

decomposition in the complex Iron is also known to catalyze the decomposition of

hydrazine (Patil 1986) Hence these compounds undergo auto combustion once

ignited The thermal decomposition behavior of metal hydrazine sulphate was

reported for the first time (Sivasankar and Govindarajan 1994) The thermal

decomposition of the metal hydrazine phenyl acetate complexes have been reported

(Jiji and Aravindakshan 1993)

152 Thermal Decomposition of N2H5+ and N2H6

2+ Metal Complexes

The simultaneous TG-DTA studies of (N2H5)2M(SO4)2 ( M= Mn or Co)

have been reported (Banerjee et al 1981) The complexes decompose exothermally

at 275degC to MSO4 via an intermediate compound M(N2H4)05HSO4(SO4)05 The

thermal decomposition of (N2H5)2Mg(SO4)2 (N2H5)2M(SO4)2 and

(N2H5)2M(SO4)2(N2H4)3 has been studied thoroughly (Patil et al 1981) The thermal

properties of hydrazinium aluminium sulphate have been studied (Govindarajan and

Patil 1982) Govindarajan et al 1986 reported the thermal reactivity by TG -DTA

methods of hydrazinium lanthanide sulphate hydrates (N2H5)Ln(SO4)2H2O

Thermal and structural studies on hydrazinium metal chlorides dihydrates were

reported (Kumar et al 1991) and these complexes were found to yield metal oxide as

the final residue via metal chloride But the iron complex form FeO and the copper

complex Cu2O instead of the usual products Fe2O3 and CuO respectively

Slivink et al 1968 and others have studied the thermal decomposition of

N2H5+ and N2H6

2+ fluorometallates of transition metals (Frlec et al 1980 Frlec et al

1981 Slivnik et al 1966 Siftar and Bukovec 1970 and Bukovec et al 1971) The

intermediate products of thermal decomposition are either hydrazinium(+1)

fluorometallates which further decompose to ammonium fluorometallates or

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

20 adducts of metal fluorides and hydrazine It is observed that the formation of

ammonium fluorometallates is highly exothermic In all the cases the final products

of decomposition are metal fluorides except in the case of copper complex which

forms the metal as the end product

Thermal behaviour of hydrazinium (+2) hexafluorogermenate has been

studied (Gantar et al 1985) The thermal decomposition of some methyl hydrazine

and methyl hydrazinium complexes of copper (II) copper (I) and mixed valence

species has been studied by Dowling and Class 1988

The simultaneous DTA-TG-DTG studies of hydrazinium metal formate

hydrates of the formula (N2H5)2M(HCOO)4H2O (M = Co Ni or Zn) have been

prepared (Sivasankar and Govindarajan 1995) The Co and Zn complexes form

metal oxides and Ni complex forms metal as the final product of decomposition

Thermal behaviour of (N2H5)2M(CH3COO)4 (M = Co Ni or Zn) has been reported

(Sivasankar 1994) These complexes decompose at a lower temperature than the

corresponding metal carboxylate hydrazine complexes They have also studied the

thermal behaviour of hydrazinium metal glycinates malonate and mixed metal

malonate dihydrates (M = Co Ni or Zn) Glycinate complexes gave metal and the

malonate complexes gave metal oxides as the final products of decomposition

The thermal behaviour of (N2H5)2M(C2O4)2nH2O (M = Co Ni or Cu and

n = 3 2 and 1 respectively) have been studied (Gajapathy et al 1983) Copper

compound after melting undergoes exothermic decomposition whereas Co and Ni

complexes decompose endothermally

Thermal studies of hydrazinium (+1) metal hydrazinecarboxylate

hydrates (N2H5)M(N2H3COO)3H2O have been reported by a number of authors at

different periods at different atmospheres viz air nitrogen or argon Premkumar

2002 who carried out the analysis in air and nitrogen atmosphere have reported the

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

21 formation of the metal oxides as the final products of decomposition However the

authors (Macek and Rahten 1989 and Macek and Rahten 1993) who experimented

the thermal decomposition in argon atmosphere for Fe Co and Ni complexes have

reported the metal powders as the end products which are very reactive and

sensitive to oxidation by the impurities in the argon All of them decompose

exothermally

16 INFRARED SPECTRA OF HYDRAZINE ITS SALTS AND

COMPLEXES

One of the best features of an infrared spectrum is that the absorption or

the lack of absorption in specific frequency regions can be correlated with specific

stretching and bending motions and in some cases with the relationship of these

groups to the remainder of the molecule IR spectra of hydrazine and its derivatives

are studied in the finger print region between 1300 cm-1 and 650 cm-1 They have

been reported for several hydrazine derivatives (Savoie and Guay 1975 Glavic and

Hadzi 1972) and metal complexes (Nieuwpoort and Reedijik 1973 Brown et al

1979 Braibanti et al 1968) Normal coordinate analysis for N2H2 N2H4 N2H5+

N2H62+ has been carried out (Mielke and Ratajczak 1973)

Of special interest in the vibrational assignment of hydrazine is N-N

stretching frequency since the presence of this frequency has been used as a

criterion for determining the mode of bonding of hydrazine to metal ions as well as

to distinguish it from N2H5+ and N2H6

2+ ions

Braibanti et al 1968 have given a thumb rule on the basis of earlier

studies In the complexes examined by them and others νN-N could be found at the

following frequency ranges

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

22

N2H4 (in solid state) 875 cm-1

N2H4 (unidendate) 930-940 cm-1

N2H4 ( bridging ) 948 - 985 cm-1

NH2NHY (Y = COO CSS) 986-1012 cm-1

N2H5+ cation (non-coordinated) 960 - 970 cm-1

N2H5+ cation (coordinated) 990 - 1015 cm-1

N2H62+ cation 1020-1045 cm-1

Hydrazine as a unidentate ligand (Schmidt 1984) also shows N-N

stretching at higher wave numbers for example 956 cm-1 in Мe3ВN2H4

952 cm-1 in [Hg(N2H4)2]Cl2 or 950 cm-1 in SiF4(N2H4)2

Although the N-N stretchings for free N2H5+ and bridging N2H4 overlap

fixing the molecular formulae can identify them by analytical and other techniques

The assignment of the band at 875 cm-1 in the spectrum of hydrazine to

νN-N was questioned by Durig et al (Durig et al 1966) who assigned this band to -

NH2 rocking vibration and the band at 1126 cm-1 to νN-N The infrared spectra of

M(N2H4)2Cl2 (M = Mn Fe Co Ni or Zn) complexes were recorded (Satyanarayana

and Nicholis 1978 ) and the absorption in the region 1150 -1170 cm-1 were assigned

to νN-N of bridged hydrazine Despite these reservations the frequency of νN-N is a

useful indication of the type of coordinated hydrazine

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

23

17 STRUCTURAL STUDIES OF HYDRAZINE COMPOUNDS

171 Structure and Bonding in Hydrazine

Infrared Raman microwave NMR photoelectron spectra and

X-ray diffraction have been used to elucidate the structure and bonding of hydrazine

(Shvo 1975 and Durig et al 1975) The high values of the melting point boiling

point and Troutons constant of hydrazine indicate that it is extensively associated

through an intermolecular H - bonding in the condensed phase but monomeric in

the gas phase Electron diffraction data give N-N-H angle as 112deg and N-N bond

length as 145- 147 Adeg suggesting sp3 hybridisation for the nitrogen atoms Thus the

two nitrogen atoms are joined by a σ-bond rotation around which can give rise to

one of the conformational isomers illustrated in Figure 11

Figure 11 The possible isomers of hydrazine (a) Staggered trans C2h

(b) Eclipsed cis C2v (c) Semi-eclipsed half cis C2 (d) Gauche C

The high value of dipole moment (Verstakov et al 1978) for hydrazine

(183 -184 D) eliminates the trans (C2h) formation and the gauche form is

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

24 considered to be the equilibrium conformation as both the eclipsed and the semi-

eclipsed conformations would involve coplanar repulsions

Electronic infrared Raman and microwave spectra show that the

molecule has C2 symmetry in the vapour and liquid states (Durig et al 1975)

However X-ray and neutron diffraction investigations in the solid state show that

the molecule to have either the gauche (C2) or cis (C2V) conformation

172 Simple Hydrazine Compounds

Two types of simple hydrazine compounds have been reported

(i) Simple molecular compounds of hydrazine of the formula

N2H4nROH where R = H CH3 or C2H5 and n = 1 for H 2 or 4 for

CH3 and 2 for C2H5

(ii) Salts of hydrazine with HCl HF HBr H2SO4 HCIO4 H3PO4

H2C2O42H2O CH3COOH 2 3 pyrazinedicarboxylic acid 3 5-

pyrazoledicarboxylic acid etc

Extensive work has been done by Liminga and his coworkers (Liminga

and Olovsson 1964 Liminga and Alex Mehlsen 1969 and Liminga 1967) The

crystal structure of N2H5+C4H5O6

- consists of infinite chain of tartrate anions linked

by head to tail by O ndash HhellipO hydrogen bonds Two such chains are cross-connected

by O ndash HO hydrogen bonds to form dimeric chains The hydrazinium cation sits at

the center of four tartrate dimers and bridges them by two center and three center N -

HO hydrogen bonds As a whole the structure is stabilized by numerous hydrogen

bonds

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

25

173 Complexes Containing Hydrazine as a Unidentate Ligand

The crystal structure of the Zn(N2H3COO)2(N2H4)2 and

Co(N2H3COO)2(N2H4)2 are found to consist of chelates of the type as shown in

Figure 12

M

NH2

NH2

NH2

NH2

NH2

NH2N

N

O

O

C

C

O

OH

H

Figure 12 Structure of M(N2H3COO)2(N2H4)2 where M= Co or Zn

The hydrazine molecule which acts as a unidentate ligand and the

hydrazinecarboxylate anion which acts as a bidentate ligand are both coordinated in

the trans position The coordination around the metal is octahedral Manganese and

nickel form complexes isomorphous with zinc and cobalt analogues

(Ravindranathan and Patil 1985)

174 Complexes Containing Hydrazine as a Bidentate Bridging Ligand

Many stable complexes of metal salts with one two or three hydrazine

molecules are known but their structures have so far received very little attention

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

26 The only available crystal structures are on the complexes M(N2H4)2X2 (Ferrari et al

1963 and Ferrari et al 1965) (M= Mn Co Ni Zn or Cd and X= Cl- (Ferrari et al

1963) NCS- (Ferrari et al 1965) and CH3COO- (Ferrari et al 1965) The above

complexes have infinite chain structures (Figure 13) with cis bridging hydrazine

molecules and respective anions in the trans positions

M M

NH2NH2

NH2 NH2

NH2

NH2NH2

X

X X

X

NH2

Figure 13 Structure of [M(N2H4)2X2]n where M= Mn Co Ni Zn and Cd X=

Cl- NCSndash and CH3COOndash

It has been pointed out that chains of complexes are not held together by

hydrogen bonds thus favouring twinning which is observed in the crystals

Infrared (Sivasankar and Govindarajan 1994 and Braibanti et al 1968) and

preliminary X-ray investigation of the complexes [M(N2H4)3]X2 (X= NO3-

H2NCH2COO- HOCH2COO- and M = Mn Fe Co Ni Zn or Cd) appear to suggest

a structure with three bridging hydrazine molecules linking metal ions which have

an octahedral coordination Recently crystal structure of

[Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10 has been determined The structure of

the complex is shown in Figure 14

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

27

Figure 14 Structure of [Ni6(N2H4)6(SO4)4(OH)2(H2O)8](SO4)(H2O)10

The complex cation in the compound has a remarkable structure with

unusual diversity of bridging groups including hydrazine molecules sulphate ions

and hydroxo group (Gustafsson et al 2010)

175 Complexes with Bidentate Chelating (η2) Hydrazine

The present crystallographically characterized complexes containing

η2N2H4 are [W(NAr)(N(NTs)2)Cl(η2 - N2H4)] (Cai and Schrock 1991) where Ar =

26-C6H3Pr2 N(NTs)2 = 26 ndashN(C5H3) (CH2Ts)2 [CpWMe3(η2-N2H4)]+(Schrock et

al 1993) [Co(tripod)(η2-N2H4)]2+ (tripod = MeC(CH2PPh2)3 and [Cp2Sm(THF)(η2

-N2H4)]+ (Heaton et al 1996) As an example the structure of [Co(tripod)( η2-

N2H4)]2+ is given in Fig 15

Figure 15 Structure of [Co(tripod)(η2 -N2H4)]2+

Co

P

P NH2

NH2

P

CH3

C

2+

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

28 176 Compounds Containing N2H5

+ as a Ligand

The crystal structure of iron complex (N2H5)2FeCl42H2O has been

studied (Kumar et al 1991) The complex consists of chloride ions and complex

cation [Fe(N2H5)2(H2O)2Cl2]2+ The metal coordinated site in the molecule is a

distorted octahedron made up of two nitrogen atoms (one from each N2H5+ ion) two

oxygen atoms(from water molecule) and two chlorine atoms The complex is found

to be isomorphous with the corresponding Co Ni and Cu analogues

The crystal structure of (N2H5)Nd(SO4)2H2O has also been reported

(Govindarajan et al 1986) Recently crystal structure of (N2H5)[Li3(C6H2-

N2O4)2(H2O)2]H2On has been reported(Starosta and Leciejewicz 2012) The

structure is composed of molecular dimmers each built up of two symmetry ndashrelated

LiI ions with distorted trigonal - bipyramidal coordinations bridged by two

deprotonated ligand molecules The layers are held together by hydrogen bonds in

which the hydrazinium cations coordinated and crystal water molecules act as

donors and carboxylate O atoms acts as acceptors

The crystal structure of the complex (N2H5)2Co(NCS)42H2O has been

studied (Kumar et al 1991) The crystal structure consists of discrete

(N2H5)2Co(NCS)4 and H2O molecules The cobalt ion is six coordinated by two

hydrazinium and four thiocyanate ions All the four thiocyanate groups are terminal

N bonded The structure of [Co(N2H5)2(NCS)4] is illustrated in Figure 16 The

nickel complex is iso-structural with the cobalt complex

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

29

Co

S

C

N

S

C

N

S

C

N

S

C

N

NH2

NH2

NH3

NH3

+

+

Figure 16 Structure of [Co(N2H5)2(NCS)4]

The structure of the complex (N2H5)2PtCl42H2O has been determined by

a single crystal X-ray crystallography (Kumar et al 1991) This consists of

[Pt(N2H5)2Cl2]2+ cations and water molecules The platinum ion has a square planar

coordination bonded by two chlorine atoms and two nitrogen atoms from the N2H5+

ions through trans positions

Sivasankar and Govindarajan (Sivasankar and Govindarajan 1995 and

Sivasankar 1994) have proposed an octahedral structure for [(N2H5)2MX4] (M = Co

Ni or Zn and X = HCOO- CH3COO- and H2NCH2COO- and

(N2H5)2M(OOCCH2COO)22H2O (M = Co Ni Zn or Cd) on the basis of IR and

electronic spectra magnetic and thermal studies

Recently crystal structures of [Cr(N2H5)2(SO4)2](Parkins et al 2001)

[Cd(N2H5)2(SO4)2](Srinivasan et al 2006) and [Mn(N2H5)2(SO4)2](Srinivasan et al

2007) have been determined

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

30

177 Compounds Containing Non-coordinated N2H5+ Ion

Though N2H5+ ion is a potential coordinating group in some compounds

it behaves like the ammonium ion ie it is outside the coordination sphere The

compounds with halides and hydrazinecarboxylate anions fall under this category

In the halide group the crystal structures of (N2H5)3CrF6 (Kojic-Prodic et

al 1972) N2H5InF4H2O (Bukovec and Golic 1976) N2H5LiBeF4 (Anderson et al

1973) and N2H5BeF3 (Anderson et al 1973a) have been determined In these

compounds N2H5+ ion is not coordinated to the metal ion In N2H5LiSO4 also N2H5

+

is not coordinated (Anderson and Brown 1974)

In the case of hydrazinium metal hydrazinecarboxylate

hydrates the crystal structure of N2H5[Ni(N2H3COO)3]H2O(Braibanti et al 1967)

has been investigated It has N2H5+ cation complex anion and water molecules In

the complex anion the nickel(II) is octahedrally coordinated by three bidentate

hydrazine carboxylate anions The crystals of the nickel compound

(N2H5)[Ni(N2H3COO)3]H2O are piezoelectric The corresponding cobalt and zinc

compounds are isomorphous with the nickel compound (Jesih et al 2004) A novel

coordination mode for hydrazine carboxylate in a polymeric ten-coordinate barium

complex has been established crystallographically (Edwards et al 1993)

The crystal structure of N2H5[Cu(C2O4)2]H2O (Gajapathy et al 1983) has

revealed that the molecule contains discrete N2H5+ ions [Cu(C2O4)2]2- ions and

water molecules It is shown in Figure 17 The same authors have reported the non-

coordination of N2H5+ in (N2H5)2Co(C2O4)23H2O

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

31

Cu

O

O

O

O

O

O

O

O

C

C

C

C

2-

Figure 17 Structure of [Cu(C2O4)2] 2- anion

Recently the crystal structure of (N2H5)2[Ln(pyzCOO)5]2H2O where Ln =

La Ce amp (pyzCOO) = 2-pyrazine carboxylic acid and

(N2H5)3[Ln(pyzCOO)4(H2O)]2NO3 where Ln = Pr Nd Sm and Dy have been

synthesized(Premkumar et al 2009) The crystal structure consists of N2H5+ cations

La(pyzCOO)2- anions and water molecules In these crystals there are independent

N2H5+ ions present in asymmetric unit and are not coordinated to the metal ion

The crystal structure of (N2H5)[Nd(C2O4)2(H2O)]4H2O and

(N2H5)[Gd(C2O4)2(H2O)]45H2O have been synthesized(Arab et al 2005) The Nd

atom is surrounded by nine oxygen atoms in which eight from four bidentate oxalate

ions and one from aqua ligand The coordination polyhedron around Nd(III) metal

ion can be described as tri-capped trigonal prism

178 Compounds Containing N2H62+ Cation

In this class of compounds N2H62+ ion exists as a cation to compensate the

negative charges of the anionic complexes Most of the compounds are known with

fluoride anion and the crystal structures of (N2H6)[TiF6] (Kojic-Prodic et al 1971)

N2H6SiF6 (Frlec et al 1980) N2H6[GeF6]H2O (Frlec et al 1981) N2H6[ZrF6] (Kojic-

Prodic et al 1971) (N2H6)2[TiF6]F2 (Golic et al 1980) N2H6[SnF3]2(Kaucic et al

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

32 1988) (N2H6)3[Zr2F13]F (Rahten et al 1990) N2H6[GaF5(H2O)](Meden et al 1996)

(N2H6)[Ca(C7H2O6)2(H2O)2](Yasodha et al 2007)have been investigated

179 Compounds Containing N2H5+ and N2H6

2+ Cations

In this class of compounds two types of cations coexist in the atomic

arrangement (hydrazinium(+1) ion NH2-NH3+ and hydrazinium(+2) ion NH3

+-

NH3+) The crystal structure of (N2H5)2(N2H6)2P6O18 (Pouchot and Durif 1991) has

been reported

18 SCOPE AND OBJECTIVE

The literature survey detailed so far illustrate the interaction of hydrazine

hydrate with inorganic aliphatic and aromatic carboxylic acids and metal ions

leading to the formation of compounds with a variety of structures With the view to

understand the structure of metal complexes with carboxylic acids and functional

group containing sulphur this work was undertaken Moreover there is no report on

sulphur containing carboxylic acids in the hydrazine system In this work a

systematic study has been carried out to find the results of interaction of hydrazine

hydrate with the acids like thioglycolic thiomalic thiobenzoic and 5-sulphosalicylic

acids in the presence of divalent metal ions like Co2+ Ni2+ Zn2+ Cd2+ Cu2+ Hg2+

and Pb2+ and inner transition metal ions like La3+ Pr3+ Nd3+ Sm3+ and Gd3+ are

reported An attempt has also been made to use these complexes as precursors to

prepare nano metal oxides Single crystals are prepared using 5-sulphosalicylic acid

with hydrazine and the structure has been found for the first time

For clarity the structure of acids and the different coordination modes of

hydrazine are shown in Figure 18(a-d) and 19(a-c) respectively

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

33

(a) Thioglycolic acid (b) Thiomalic acid (c) Thiobenzoic acid

(d) 5-Sulphosalicylic acid Figure 18(a-d) Structure of the acids

(a)Monodentate hydrazine (b)Bidentate hydrazine (c)Monodentate hydrazinium cation Figure 19(a-c) Structure of hydrazine

COSHSHCH2COOH

HO

O

HOS

O

OOH

SH-CHCOOH

CH2COOH

SH-CHCOOH

CH2COOH

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters

34

The main objectives of the present work are

To prepare hydrazinium salts of thioglycolic thiomalic thiobenzoic and

sulphosalicylic acids and characterize them by analytical IR spectroscopic

thermal analysis and single crystal XRD analysis

To prepare metal hydrazine complexes of thioglycolic thiomalic

thiobenzoic and 5 ndash sulphosalicylic acids by the reaction of hydrazine hydrate

with metal nitrate hydrates and characterize them by different physico-chemical

techniques

To correlate structure and thermal reactivity relationship among the

complexes

Hydrazine complexes are found to yield metal oxides at low temperatures

in the nano scale hence it was aimed to use the complexes to prepare nano metal

oxides using them as precursors

To find the conductivity of the complexes in their solid state

To study the isomorphism among the complexes using powder X-ray

diffraction technique

To evaluate the kinetic parameters of dehydration and dehydrazination

decarboxylation of all the complexes and hydrazinium salts

Based on the above objectives this research work was performed and

the results obtained are discussed in the following chapters