STUDIES ON THE CaORDINATION COMPOUNDS OF TRANSITION METALS CONTAINING

UGANDS OF ELECTRON RICH ELEMENTS

DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS

FOR THE AWARD OF THE DEGREE OF

iHagter of ^IjilosiopI)? IN

CHEMISTRY

BY

ABDUL BASHAR

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1989

DS/S. A ^

Q)p. cK. d . C^iddiqi

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH-2)2001

PHONE : Office : 5515

Date. l l o l . l 9 8 9

Cer t i f i ed t h a t the work embodied

in t h i s d i s s e r t a t i o n i s the r e s u l t of the

or ig ina l researches of the candidate

carr ied out under my supervis ion .

k-r-( K.S. Siddiqf^)

.T . ' ^ 3 Reader

ACKNOWLEDGEMENT

I express my hearty thanks and sincerest gratitude

to my supervisor Dr. K.S. Siddiqi, Reader, Department of

Chemistry, Aligarh Muslim University, Aligarh for his

benevolent guidance, sympathetic behaviour, keen interest

and devotion throughout the tenure of this work.

I am grateful to Prof. S.A.A. Zaidi for his valuable

suggestions and help rendered from time to time.

I am very thankful to Dr. M.I. Khan who helped me

in the initial stages of my work.

I also avail the opportunity to express gratefulness

to my father and mother(late) for encouragement and interest

in my academic persuit.

The cooperation of Dr. S.Tabassum along with other

colleagues and friends is thankfully acknowledged.

Finally, I express my gratefulness to Prof. S.M.Osman,

Chairman, Department of Chemistry, A.M.U., Aligarh for

providing necessary research facilities and the Government

of Assam for awarding scholarship and sanctioning leave.

( Abdul Bashar )

C O N T E N T S

1 . INTRODUCTION

2. PRESENT WORK

3. EXPERIMENTAL

4. RESULTS AND DISCUSSION.

5. REFERENCES

Page No.

1

5

6

8

25

I N T R O D U C T I O N

INTRODUCTION

Thionalide also known as a-mercapto N, 2-naphthyl

acetamide, has been used, since long in the detection and

identification of a number of transition metal ions

Mercury and silver were determined quantitatively by the 5

precipitation with thionalide . An appreciable number of

transition metal complexes with thionalide have been reporte

It has also been found that thionalide may act both as oxi-

^ . - ^

disirig and reducing agent and has been invariably used in the

oxide.tion and reduction of platinum in its salts .

Some sulphides of 2-quinoxaline derivatives derived Q

from thionalide have been reported , Treatment of 2-quino-

xalin? with appropriate mercapto derivative gave 2-(3-naphthyl

amino acetyl thio)quinoxaline (A).

H

RN-CO-CHj-S

[*.' R = 2-naphthyl, Ph, tolyl]

H

[A]

Some important stable polyamide fibres have been

10 syntheslsed in the presence of thionalide complexes

Thermal oxidation resistant polyamlde fibres have been

synthesised in the presence of Cu(ll) acetamide complex (B).

H

Where, R = 2-naphthyl , Ph, t o t y l .

[B]

Anothe'r type of hea t ox ida t ion r e s i s t a n t polyamlde, such as

polyn>lons, have a l so been prepared in the presence of

C u ( l l ) t h i a z o l e complex (C). I t he lps in t h e po lymer i sa ­

t i o n of monomeric spec i e s .

R - N - N - C u - N - N - R

3 X3/Xg/ ^ ^ V S

[•.* R = naphthyl , Me, Et , Pr , Ph, t o l y l ]

[c]

Potentiometric studies of thionalide complexes with

1 12 metal ions have been made ' . For instance, lead and

antimony were determined potentiometrically using thionalide.

Some organic sulphur compounds, such as thiols and thiones

were determined by titration with 0.01N Ag(l) in ammoniacal 1 14

solution using alcoholic benzene solution * . The selective

determination of Ag(l) by amperometric titration with thicnaUde

15 has a].so been done . The extractive method of radiochemical

separcition of Hg, In(Cd), Tc(Ho), Cu(Zn) and As and trace

1 fi elements in water by co-precipitation have been developed .

Nickel and cobalt were extracted from an aqueous solution by

17 using an organic solvent containing thionalide . Substoi-

chiometric levels of lead in biological materials were

extracted wiih thionalide dissolved in methyl isobutyl ketone

to form lead-thionalide complexes which were subjected to

1R photon activation analysis

Mossbauer study of magnetic behaviour of some Fe(ll)

19 20 complexes with thionalide have been made extensively * .

Back coordination of Fe(ll)-thionalide complexes was also

demonstrated by means ofMossoauer spectroscopy and magnetic

19 susceptibility measurements , The dissociation constants of As and Cd complexes with thionalide have been studied by

21 UV-absDrption spectroscopy ,

Complexes of dichloro bis(cyclopentadienyl) titanium

(IV) with N-(aryl)-2-mercapto acetamide has recently been

22 prepared . Titanium mercaptoacetamides, CppTi(MA)Cl and

Cp2Ti(MA)2 [where^Cp= cyclopentadienyl, MAH=RNH-C0-CH2-SH,

R=a-naphthyl, Ph, tolyl] have been synthesised by the reacticn

of Cp TiCl with MAH in THF at room temperature in the

presence of triethyl amine.

A large number of coordination compounds of d and

f block elements with urea, thiourea, semicarbazide and

27

chlorohydrates of thiosemicarbazide are reported . The

lanthanides are known to have the tendency to expand their

coordination number greater than six in general" ~ but in excepi:ional cases they have been reported to achieve

lanid

28,29

27 coordination number six only . The complexes of lanthanide

ions v/ith various amide der ivat ives have also been reported

An appreciable work has been done on sulphur

analo^:ues of natural ly occurring purine and pyrimidine bases .

A few compounds of rare earth ions have been reported to be

useful in chemotherapy of cancer. For example, 6-raercapto

purine and S-methyl mercapto purine have been reported

to have extremely c l in i ca l ly useful antileukemic ac t iv i ty .

PRESatT WORK

A thorough search of chemical literature reveals

that no systematic work on rare earth chelates of thionalide

has been carried out so far. The diverse properties of

thionalide both as chelating agent and as antileukemic drug

motivated the author to undertake the study of thionalide

complexes with Ce(III), Pr(III), Nd(lll), Gd(lll), Dy(lII)

and Er(lll) both in solution and as solid to examine the mode

of coordination and the nature of complexes.

All the sites in thionalide apparently seem to be

prone to coordination but it acts as a bidentate ligand as

has been shown in several cases.

The solid complexes were characterised by elemental

analysis and IR spectral data. In some cases NMR spectra

were also run in deuterated n^SO. In order to determine the

stability constant and other physical parameters of some

complexes formed in solution Bjerrum-Calvin pH-metric titration 35

technii ue as modified by Irving and Rossotti was adopted.

E X P E R I M E N T A L

EXPERIMENTAL

Rare earth metal(IIl) chloride (Kay and Baker)

solution was prepared in perchloric acid for pH-metric

titration. Thionalide was dissolved in an acetone-water

mixture. Sodium hydroxide(E.Merck), perchloric acid and

sodium perchlorate(Riedel) solutions were prepared in

carbondioxide free distilled water and standardised by

know.i method.

An Elico L1-10 pH-meter with an accuracy of _+0.05

was employed in combination with glass calomel electrode.

The piH electrode system was caliberated with the help of

stanoard buffers (pHA.O and pK9»2)» The IR spectra were

recorded on a Shimadzu IR-hOd model as KBr disc. The NMR

spectra were recorded in deutarated dimethyl sulfoxide

with Varian A-50D model.

SYNTHESIS OF COMPLEXES

The thionalide dissolved in alcohol-acetone mixture

was mixed with metal(IIl) chloride solution in alcohol in

1:1 molar ratio. This mixture was stirred for twenty four

hours at room temperature. A white precipitate was obtained

when t!ie volume of the solvent was reduced to half. It was

kept overnight, filtered, washed with alcohol and dried in

an oven at 60°C.

POTiJlNTIOMETRIC TITRATION

The metal chloride solution was prepared in

perchloric acid to prevent hydrolysis. The experiment

was carried out at ambient ternperature and at 0.1M ionic

strength. The following solutions were titrated against

0.2128M sodium hydroxide solution.

1. 5inl HCIO^ (0.1M)

2. 5inl HCIO^ and 25 ml thionalide solution (0.005M)

3. 2 )ml thionalide solution(0.005M) and 5ml HCIO^

containing 0.005M metal chloride solution. To the above

mixture a known quantity of sodium perchlorate was added

to maintain the ionic strength at 0.1M. However, the

total volume of the above solution was kept at 50ml by

adding calculated volume of carbondioxide free distilled

water.

R E S U L T S A N D D I S C U S S I O N

8

RESULTS AND DISCUSSION

The thionalide is a negatively charged bidentate

lig£uid. Analytical data suggests the formation of MCl2L»2HpO

type complexes. The complexes are stable to heQt and air

oxidation. They were formed according to the reaction

MCI, + C^2H^^NS0 > MC12.C^2H^QNS0 •»• HCl

The iDolar conductance of one raillimolar solution of the

complexes in EMSO indicates their covalent nature (12-15«8

Ohm"' Cm^ mol"'').

The NMR spectra of the complexes recorded in EMSO d

have been compared with those of the ligand. The NH proton

signal in the secondary and tertiary amines are dependent on

the extent of solvent exchange rate. When the rate of exchange

is slow the NH proton signal broadens and the protons are

decou])led from the nitrogen and CH protons. However, it gives

a broad singlet at 69*3 which does not appear in the complexes

showir.g the replacement of amino hydrogen by metal. The CHp

and SH proton signals are observed at 6 3«4 and 63.9 respecti­

vely. Other aromatic proton signals are also observed in the

range of 67.5 - 8.5-

IR SPECTRA

It is well knowi that there is very little shift

in VCC-O) and V(C-N) if both these groups are coordinated

to metal lon^ . Since thionalide contains both these donor

sites it was essential to examine if they both were chelated

to lanthanide ions. In the present case a strong V(N-H)

band at 3000 cm in the free ligand disappears on complexa-

tion with lanthanide ions showing the replacement of the

amino hydrogen by metal ion which has been further supported

by the quantitative analysis of chlorine in the complexes.

Two broad bands of medium intensity at 1290 cm and 1355 _^

cm in the free ligand assigned to V(C-N) are shifted and

in sonie cases remain almost unaltered. The 0=0 stretching

band on the other hand, has been found to be positively

shifted from its position by about 10 cm in each case.

These observations corroborate that both nitrogen and oxygen

atoms are coordinated to lanthanide ions.

The absorption bands observed at 3250 cm . and at

1605 cm~^ have been assigned to V(O-H) and 6(H-0H), respect­

ively. On the basis of these studies the complexes are

proposed to have an octahedral geometry.

N C-CH2-SH (I

0

H2O—M~Cl

/ \

CI OHo

io

TABLE 1 ELEMENTAL ANALYSIS AND MELTING POINTS OF THIONALIDE

COMPLEXES.

Complexes M.P. •C

Colour % C

Calcd. (Found)

% H

Calcd. Found)

% N

Calcd. (Found)

1. (C^2H^QNS0)CeCl22H20

2. (C^2H^QNS0)PrCl2.2H20

3 . (C^2"^QNS0)NdCl2.2H20

4 . (C.2H^QNS0)GdCl2.2H^'0

5. (C.|2H^o^^°^^y^^?'^^2°

6. (C.|2H^QNS0)ErCl2.2H20

208-10 White .31.11 3.04 3.02 (31.00) (2 .91) (2.89)

280-10 White 31.06 3.03 3.01 (30.99) (3 .00) (2 .97)

230-32 White 30.83 3.01 2.99 (30.80) (2.95) (2.98)

205 V/hite 30.00 2.93 2.91 (29.75) (2.86) (2.80)

205 White 29.67 2.90 2.88 (29.55) (2.80) (2.79)

210 D White 29.39 2.87 2.85 (29.27) (2 .69) (2.70)

D i n d i c a t e s decomposition

n

TABLE 2 - IR SPECTRA OF THIONALIDE AND ITS COMPLEXES.

Complexes V(C-N) V (C=0) V(O-H) 6 ( H - 0 H )

-1 -1 -1 -1 cm cm cm cm

C^^H-i NSO (Ligand) 1290(m), 1355(m) I645(s)

(C^2^^QNSO:CeCl2.2H20 1295(m), 1355(m) l655(s ) 3250(b) I605(s)

(C^2HioNSO)PrClp.2H20 1295(m), 1355(ra) I655(s) 3250(s) I600(s)

(C^2Hio'^^*^'N^^^2*^"2° I300(m), 1360(m), I650(s ) 3300(b) , I6l0(m)

(0^2^10^^^^'^^'^^2'^"2° ''295(m), 1355(m) I660(s) 3250(b) I 6 l 0 ( s ) -4 -

(C^2HioNSO)DyCl2.2H20 1295(m), 1355(m) I650(s) 3250(b) I605(s)

(C^2Hio^^*^)^^*^^2*^"2*^ 1300(m), 1350(m) I650(s) 3300(b) 1590(s)

12

PROTON LIGAND STABILITY CONSTANT

The only d i s s o c i a b l e p ro ton in t h i o n a l i d e i s

r e l e a s e d in the pH range of 2 -2 .5 as shown below.

NH-CO-CH2.SH ^ f ^ j , ^VN-C0-CH2-SH + H"

The proton ligand formation number, nA was calculated from

Irving and Rossotti equation(l). Pointwise calculation for

the proton ligand stability constant was calculated using

equation 2 and 3«

(V -V ) (N** + E«)

V - - H — ; •••• (^ (V^. V ^ ) T L

where,

y = number of dissociable protons

v^= volume of NaOH consumed in titrating pure acid

Vp= volume of NaOH consumed in titrating acid + ligand

V = total volume i.e. 50 ml o

N*'= cDncentration of NaOH solution

£**= concentration of acid solution

T. = concentration of ligand solution

PK, = PH + log —!^ (2)

when 1.0 < n. < 2.0

13

PK" - PH + log .pj- .... (3)

when n. < 1.0 A

The acid ligand curves in ali the cases deviate

from 1:he pure acid curve at pH meter reading 2.5 (fig-l).

The h.Lghest n. value found was 0.95 and hence only pK-H

were calculated.

METAL LIGAND STABILITY CONSTANT

Stepwise calculation of stability constant was

made with the assumption that the hydrolysis of the metal

ions did not occur and the formation of polynuclear species

was prevented. The metal ligand titration curve deviates

from pure ligand curve at pH 2.50. The highest n values

calculated from equation 4 for Ce(IIl), Nd(IIl) and Dy(lll)

were 0.79, 0.85 and 0,92 respectively at 0.1M ionic strength

and therefore, only logK was calculated. The n values at

(V,-Vp)(N''+ E")

(V^. V^) n^ T,

where,

M

V-, = Volume of NaOH consumed in titrating acid

+ ligand + metal ions.

pH7.5 indicates the hydrolysis of the complexes. The pL

M

m i s of ;JaC

F I G . - I TV PIC A - r i T R A T f O N CUf^VSS OF R A R E

E A R T H {111) I O N C O M P L E X

IS

1

2 3 ^ 5 6 7 8 9 10 11 12

FIG.2 PROTON LIGAND FORMATION CURVE

u

values; were calculated at various n values using equation 5*

antilog eJJ. +,-i2„ H (V +V,) PL » Log^o [ M antilofi pH o 3 ] ... (5)

The m(?tal ligand formation curves were obtained by plotting

n ver.'sus pL (Fig 3)» From these accurate logK was obtained

by pointwise calculation using equation 6.

n LogK = PL + log ... (6)

1 - n

e2 A plot of logK versus shows a roughly linear

relationship suggesting ionic character for the metal ligand

bond (Fig 4). The metal ions may be arranged in the

following increasing order of their stability constants Ce<

Nd < Dy.

r 7

TABLE .5 n^ VALUES OF THIONALIDE AT 30«C AND M = 0.1M.

(B)

pH-meter reading

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

Proton ligand formation number

0.95

0.90

0.81

0.81

0.81

0.81

0.76

0.76

0.71

0.71

0.62

0.62

0.62

0.57

0.52

0.52

0.48

0.48

. - cs* '

I 6

TABLE 4- PROTON LIGAND STABILITY CONSTANT OF THIONALIDE

AT 30«'C AND 0.1M IONIC STRENGTH.

PK2 7.15

19

TABLE 5 - RARE EARTH COMPLEXES WITH THIONALIDE AT 30'C

AND 0.1M IONIC STRENGTH;

(B) Ce(lll)

pH-me':er reading ^ n PL

2.5 0.35 7.18

3.0 0.31 6.65

3.5 0.'40 6.22

4.0 0.52 5.81

4.5 0.58 5.37

5.0 0.58 4.87

5.5 0.61 4.41

6.0 0.68 3.99

6.5 0.72 3.55

7.0 0.79 3.18

2't)

(B) Nd( l I I )

pH-meter reading " — ZT"

2,5

5.0

5.5

4.0

4 .5

3.0

3.5

6.0

6.5

7 .0

0.40

0.47

0.52

0.64

0.75

0.69

0.74

0.80

0.85

0.79

7 .2

6.77

6.31

5.94

5.60

5.01

4 .58

4 .20

3.82

3.18

21

(B) Dy(lll)

pH-meter reading ^ ^

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

0.40

0.79

0.81

0.87

0.87

0.87

0.92

0.92

0.92

0.92

7.20

7.01

6.72

6.38

5.88

5.39

5.10

4.60

4.10

3.60

??

TABLE 6- STABILITY CONSTANT, logK OF COMPLEXES AT

50»C AND AT 0.1M IONIC STRENGTH.

Complex log K

Ce(lII) 4.72

Nd(lII) 5.50

Dy(III) 6.37

23

0.8

0.6

0.4 -

7 8

PL

FIG.3 - TYPICAL FORMATION CURVE OF RARE

EARTH COMPLEX OF THIONALIDE

i4

H 5

24

8 8.5 1

9.5

e^/r

f 10

1 ia5 11

FIG. 4

R E F E R E N C E S

?5

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