BANSAL CLASSES BREAK Co Ordination Compound

CO-ORDINATION COMPOUND

Delhi: 48, Hasanpur, I.P. Extn., Patparganj, Pin-110092; Ph: 011-43094712, Mobile: 09811744029Kashipur : Aryna Nagar, Near Himalyan Public School, Kashipur (Uttarakhand) Ph. : 05947-276252 Mobile :9837617412E-mail: [email protected] Website: www.marksmanclasses.com

[180]

• Coordination CompoundsIntroduction: The complexes show a wide variety of physical and chemical properties which are quite differentfrom normal salts. These difference arise due to the difference in their structures.Molecular or addition compounds: When solution containing two or more salts in stoichiometric (i.e.,simple molecular) proportions are allowed to evaporate, we get crystals of compounds known as molecular oraddition compounds.

2 2 2 2(carnallite)

KCl MgCl 6H O KCl.MgCl .6H O

2 4 2 4 3 2 2 4 2 4 3 2(potash alum)

K SO Al (SO ) 24H O K SO .Al (SO ) .24H O

2 2(potassium ferrocyanide)

Fe(CN) 4KCN Fe(CN) .4KCN

These are of two types depending on their behaviour in aqueous solution.I) Double salts or Lattice compounds: The addition compounds having the following characteristic are calleddouble salts or lattice compounds.a) They exist as such in crystalline state.b) When dissolved in water, these dissociate into ions in the same way in which the individual components

of the double salts do.

2 2–4 4 2 4 2 4 4

Mohr 's saltFeSO .(NH ) SO .6H O Fe (aq) 2NH (aq) 2SO (aq)

3 2 –2 4 2 4 3 2 4

Potash alumK SO .Al (SO ) .24H O 2K (aq) 2Al (aq) 4SO (aq)

.II) Coordination (or complex) compounds: It has been observed that when solutions of Fe( 2CN) and KCN

are mixed together and evaporated, potassium ferrocyanide, 2Fe(CN) .4KCN is obtained which in aqueous

solution does not give test for the 2Fe and –CN ions, but gives the test for K ion and ferrocyanide ion,4

6Fe(CN)

4–2 2 6Fe(CN) 4KCN Fe(CN) .4KCN 4K Fe(CN)

Thus we see that in the molecular compound like 2Fe(CN) 4KCN, the individual compounds lose their identity.

Such molecular compounds are called coordination (or complex) compounds.A complex compound may contain a simple cation and a complex anion or a complex cation and a

simple anion or a complex cation and complex anion, e.g. IV IV2 6 3 4 2 2K [Pt Cl ], [Pt (NH ) Br ]Br and

III III3 6 2 4 3[CO (NH ) ][Cr (C O ) ] are all complex compounds. The term complex compound is used

synonymously with the term coordination compound. In the above complex compounds, the ions–[ ] ,[ ( ) ] ,[ ( ) ] IV 2 IV 2 III 3

4 3 4 2 3 6Pt Cl Pt NH Br Co NH and –[ ( ) ]III 32 4 3Cr C O are called complex ions. Thus

a complex ion is an electrically charged radical which is formed by the union of a metal cation with one or more

neutral molecules or anions. Neutral complexes such as 3 34 6 3, ,Ni CO Cr CO Co NH Cl are

also known.




[181]

Different parts of Co-ordination compound :

• COORDINATION SPHERE

Aggregate of metal and ligands attached to it is called coordination sphere. It remains as a single unit in thesolutions. Metal atom acts as Lewis acid and ligand acts as Lewis base in these complexes.

e.g. K4 [Fe(CN)6]

Ionic Co-oridnationSphere sphere

• COORDINATION NUMBER

The number of lone pairs accepted by a given central atom from ligands. It may be different from number ofligands attached.

In [Cu(NH3)4]+2 the co-ordination no. of Cu is 4.

In [Co(en)3]3+, the co-ordination no. of cobalt is 6 and en is a bidentate ligand.

• LIGANDS:

1. The neutral molecules, anions or cations which are directly linked with central metal atom or ion in acomplex ion are called ligands.

2. The ligands are attached to central metal ion or atom through co-ordinate bond or dative bond.

3. Denticity:The number of atoms (Sites) through which any ligand can attach to a metal atom is called itsdenticity.

Type of Ligand DefinitionMonodentate Ligands having only one site of attachementMultidentate Ligands having many sites (atoms) through which these can attach to central

metal atomAmbidentate Ligands which can attach a metal atom through more than one way /atom.Bridging Ligands Ligands which can be attached simultaneously to more than one metal atoms.

(denoted by in normenclature)4. Classification of Ligands:

1) Neutral unidentate :

2) Univalent unidentate : , , , , ,F Cl Br I OH CN

3) Neutral bidentate : , ,en bipy phen

4) Univalent bidentate : acac, DMG, Glycine5) Bivalent bidentate : Oxalate, Sulphate, Carbonate6) Multidentate or Flexidentate : Dien, Tren, EDTA

7) Ambidentate : 2, ,NCS NO CN

8) Bridging : 2, , , ,Cl OH NH CO NCS

5. SOME COMMON POLYDENTATE LIGANDSNAME ABBREVIATION STRUCTURE

Ethylenediamine enH2N

NH2



[182]

2,2-bipyridyl bipy

N N

1,10-phenanthroline(phen phen

N N

Acetylacetanato Acac

Oxalate Ox OOC COO

Glycinato gly

O

ONH2

Dimethylglyoximate DMG

C

C

N

NCH3

CH3

OOH

Diethylenetriamine dienNH2

NHNH2

Triethylenetetramine trenH2N CH2

CH2 NH

CH2 CH2

NH CH2

CH2 NH2

Ethylendiamine tetraacetate E.D.T.A. N CH2 CH2 NCH2COO

CH2COO

OOCH2C

OOCH2C

(Hexadentate)

6. Chelation

Polydentate ligands whose structure permit the attachment of their two or more donor atoms (or sites) to thesame metal ion simultaneously and thus produce one or more rings are called chelate or chelating ligands(from the Greek for claw) or chelating groups. However, it should be noted that every multidentate ligand is notnecessarily a chelating ligand — the coordinating atoms of the ligand may be so arranged that they cannot be

coordinated to the same metal atom to produce a ring structure. Thus — — —2 2 2 2NH CH CH NH is a

chelating ligand, while



[183]

2 2 2N — CH — CH — NH

2 2—(CH ) —

2 2—(CH ) —

is not, although both are diamines. The formation of such rings is termed chelation

and the resulting ring structures have been called chelate rings or chelates.

The chelate rings are most stable, because of reducd strain, when they have 5 or 6 membered ring includingthe metal ion. The enhanced stability of complexes containing chelated ligands (i.e., multidentate ligands) isknown as the chelate effect.

2 2

2 3 3 24 44 4Cd H O NH Cd NH H O ...............(1)

0 1 0 1 1 056.3 , 67.3 , 37.2 /H k J mol S J mol K G kJ mol 2 2

2 24 22 4Cd H O en Cd en H O .....................(2)

0 1 0 1 1 056.8 , 14.1 , 60.7 /H kJ mol S J mol K G kJ mol Note that 0H is same due to formation of Cd - N bond. There is difference in entropy. It is called Entropyeffect. In second case, 2en replace 24H O molecules. So increase in entropy of the system.

• IUPAC Nomenclature Of Coordination Compounds1. Naming of salt: If the complex is a salt, the cation is named first followed by the name of the anion.2. For the complex entity, the name of the ligand(s) is put before the name of the metal atom. However,

the reverse order is followed in writing the formula of the compound.3. Naming of the negative ligands: The names of all anionic ligands end in ‘o’ .

2: , : , : , :F Fluoro Cl Chloro O Oxo CN Cyano

Cationic and neutral ligands have no special ending. There are a few exceptions like ‘aqua’ for H2O,ammine for NH3, carbonyl for CO, and nitrosyl for NO groups.

4. Indication of the number of ligands: The number of ligands is indicated by adding prefixes di–, tri–,tetra–, penta–, hexa–, etc. for two, three, four, five, six, etc entities of the ligand. For example,

3 6 3[Co(NH ) ]Cl will be called hexaamminecobalt(III) chloride.

If the ligands are big complicated groups, instead of di–, tri–, tetra–, penta– prefixes we use bis–, tris–

, tetrakis–, pentakis– etc. For instance 3 3 2Cu(CH COCHCOCH ) is called bis(acetylacetonato)copper.(II)

5. Order of Naming ligands: The ligands are quoted in alphabetical order. Numerical prefixes indicatingthe number of ligands are not considered in determining that order. For example, a compound like

2 2[CoCl(NO )(en) ]Cl will be called chlorobis (ethylenediamine) nitrocobalt (III) chloride.

6. Oxidation state: The oxidation state of the metal ion in a complex is indicated by Roman (I), (II), (III)etc. or an Arabic (O) and placed in parenthesis immediately after the name of the metal.

7. Naming of complex: The name of the complex anion ends in ‘ate’ and the Latin name of the metal

atom is used. 2 6K [PtCl ] : Potassium hexachloroplatinate(IV), 2K[Ag(CN) ] :Potassiumdicyanoargentate(I).

8. A little space is given between the name of the cation and the anion. No space or hyphen is usedanywhere else.

9. Once the complex entity is completely identified according to the above rules, no mention of the number

of cations or anions used for charge balancing is required. For example, 3 6 3[Co(NH ) ]Cl is called

hexaamminecobalt(III) chloride and not hexaamminecobalt(III) trichloride. Similarly, 2 6K [PtCl ] is namedpotassium hexachloroplatinate(IV) and not dipotassium hexachloroplatinate(IV).



[184]

10. Ligands having more than one donor atom: If a ligand has more than one donor atom, the actualatom involved in the bond formation with the metal ion is indicated by putting italicized symbol of the

atom after the name of the ligand. For example, –[ ( ) ]32 3 2Ag S O is called dithiosulphato S-argentate(I)

ion.

SCN thiocyanato CN - : Cyano 2NO nitro

NCS isothiocyanato NC : Isocyano ONO nitrito

11. Naming of Bridging ligands: A bridging group is indicated by putting the Greek letter ‘ ’immediatelybefore its name and separated by hyphens from other ligands. For

example, 4OH2 OH 24 4H O Fe Fe H O

is called -dihydroxobis [tetraaquairon(II)] ion and the

formula could be written as 42 4 2 2 4[(H O) Fe( OH) Fe(H O) ] also.

12. Structural information may be given in the names and formulae by prefixes such as cis–, trans– etc.

3 2 2[Pt(NH ) Cl ]can be written as cis-dichlorodiammineplatinum(II) or trans-dichlorodiammineplatinum(II),respectively.

Note: When writing the formula of a complex, the central atom is listed first. The coordinated groups (i.e., ligands)are listed in the order: formally anionic ligands, neutral ligands followed by cationic ligands. Within eachgroup, the ligands are listed alphabetically according to the first symbol

Illustration 3: Write down IPUAC name of K2 [Fe(CN)3 Cl2(NH3)2]Solution: The positive part is named first followed by the negative part. In the negative part the names are written

in alphabetical order followed by metal. So the name is Potassium diamminedichlorotricyano-N-ferrate(III).

Illustration 4: Using IUPAC rules, write the formula for the following:Hexaamminecobalt(III) sulphateSolution: [Co(NH3)6]2(SO4)3

• IsomerismCompounds that have the same chemical formula but different structural arrangement are called isomers.Because of the complicated formula of many coordination compounds,the variety of bond types and the no ofshapes possible, many different types of isomerism occur.

• Structural Isomersimi) Polymerization Isomerism: This is not true isomerism because it occurs between compounds having

the same empirical formula, but different molecular weights. For example, , [Pt(NH3)2Cl2], [Pt(NH3)4][PtCl4],[Pt(NH3)4] [Pt(NH3)Cl3]2.

ii) Ionization Isomerism: This type of isomerism is due to the exchange of groups between the complexion and the ions outside it. [Co(NH3)5Br]SO4 is red – violet. An aqueous solution gives a white precipitate

of BaSO4 with BaCl2 solution, thus confirming the presence of free 24SO ions. In contrast [Co(NH3)5SO4]Br

is red. A solution of this complex does not give a positive sulphate test with BaCl2. It gives a pale yellowcoloured precipitate of AgBr with AgNO3, thus confirming the presence of free Br– ions.

iii) Hydrate Isomerism: Three isomers of CrCl3.6H2O are known. From conductivity measurements andquantitative precipitation of the ionized chlorine, they have been given the following formulae:Complex Colour No.of 3AgNO Conc. Molar Cation

Cl 2 4H SO cond. Exchange[Cr(H2O)6]Cl3 violet 3 100% No wt.loss 430 3HCl

[Cr(H2O)5Cl]Cl2.H2O green 2 66.66% 1 2H O loss 220 2HCl

[Cr(H2O)4Cl2].Cl.2H2O dark green 1 33.33% 22H O loss 80 1HCl

a) Conc. 2 4H SO removes lattice water and not the coordinated water molecules.

b) Molar conductivity is in 1 2 1Ohm cm mol



[185]

c) When the known amount of the complex is sent through cation exchange resin 3RSO H , HCl isliberated. The acid can be estimated by titration with standard NaOH solution.Eg:- The first complex gives 3 moles of HCl per mole of the complex.

iv) Linkage Isomerism: Certain ligands contain more than one atom which could donate an electron pair.

In the 2NO ion, either N or O atoms could act as the electron pair donor. Thus there is the possibility

of isomerism. Two different complexes [Co(NH3)5(NO2)]Cl2 and [Co(NH3)5(ONO)]Cl2have been prepared,

each containing the 2NO group in the complex ion.v) Coordination Isomerism: If the complex is a salt having both cation and anion as complex ions then

the ligands can exchange position between the cation and the anion. This will result in the formation ofcoordination isomers. For example

3 36 6 6 6Cr NH Co CN and Co NH Cr CN

3 4 3 44 4Pt NH CuCl and Cu NH PtCl

3 2 4 3 2 2 4 2 4 2[Co(en) ][Cr(C O ) ] and [Co(en) (C O )][Cr(en)(C O ) ]

2 2 4 2 4 2 3 2 4 3[Cr(en) (C O )][Co(en)(C O ) ] and [Cr(en) ][Co(C O ) ]vi) Coordination Position Isomerism: If in a multinuclear complex the distribution of ligands around the

metal centre changes, it results in a different isomer. Such an isomerism is called coordination positionisomerism. Some typical examples are

: 3 4 3 2 2 2 3 3 3 3 2[(NH ) Co Co(NH ) Cl ] Cl and [Cl(NH ) Co Co(NH ) Cl]Cl 2

2

NHO

2

2

NHO

3 2 2 3 3[(R P) Pt PtCl ] and [Cl(R P) Pt Pt(R P)Cl] ClCl

ClCl , ( 3R P Tri alkyl phosphine)

viii) Electronic Isomerism: The complex 3 5 2[Co(NH ) NO]Cl exists in two forms. One is blackparamagnetic while the other is pink and diamagnetic. The black isomer is a Co(II) complex containingneutral NO group whereas the pink one is a Co(III) complex with –NO . This kind of isomerism is knownas electronic isomerism.• Stereo Isomerisms: Stereoisomers have the same bonds but the arrangement of atoms in space is different.

Stereoisomerism can be divided into two kinds: geometrical and optical.i) Geometrical isomerism or cis-trans isomerism: It occurs when ligands can assume different positions

around rigid bonds with the metal ion.

(1) The compound [ 3 2 2Pt(NH ) Cl ]has a square planar structure. The two possible arrangements are.

Pt

3H N

3H N Cl

Cl

Pt

3H N

3NHCl

Cl

They are differentiated by dipole moment. Cis has larger dipole moment than trans one.For square

planar complexes 4 3Ma , Ma b or 3Mab where a and b are monodentate ligands, the geometrical

isomerism is not possible. The square planar complexes, 2 2Ma b 2Ma bc, Mabcd and

2M(AA) , 2M(AB) where AA and AB represent symmetrical and unsymmetrical chelating ligandsgive geometrical isomers.

(2) Geometrical Isomers - structures:

(a) 2 2Ma b 3 2 2Pt(NH ) Cl



[186]

Pt

3H N

3H N Cl

Cl

Pt

3H N

3NHCl

Cl

(b) 2Ma bc

3 2Pt(NH ) Cl Br Pt

3H N

3H N Br

Cl

Pt

3H N

3NHBr

Cl

(c) Mabcd 3 5 5Pt(NH )(C H N)(Cl)(Br)

Pt

3H N

Br Cl

Pt

3H N5 5NC H

Cl

5 5NC H

BrPt

3H N

5 5NC H

Cl

Br

(d) Bridged binuclear planar complexes like

[ ( ) ]3 2 2Pt PEt Cl may exist in three isomeric forms:

ClPt

ClPt

PEt 3

Et 3P Cl Cl

ClPt

ClPt

Cl

Et 3P Cl PEt 3

Et 3PPt

ClPt

Cl

Et 3P Cl Cl

trans– cis– unsymmetrical

ii) (1) Six coordinated octahedral complexs of the type , , , ,4 2 3 3 3 2 3 2 2Ma b Ma b Ma b c Ma bcd Ma b cd

,2Ma bcde Mabcdef would all give geometrical isomers. Systems with one or two bidentate ligandsand rest monodentate would also give geometrical isomers.

(2) A number of isomers are possible whether they can be isolated or separated is a different questionwhich depends on so many factors. As we increase the number of different ligands, the possible numberof isomers increases.

(3) 4 2Ma b type of complex would give only two isomers cis–and trans–.



[187]

(4) 3 3Ma b gives two isomers facial (fac–) and meridional (mer–) isomers. In the former (fac–) three ligandsof one type form one triangular face of the octahedron and the other three on the opposite face. In thelatter (mer–) one set of these ligands are arranged around an edge of the octahedron whereas the otherset occupies the opposite edge as shown in figure.

M

a

a b

b

b

a

M

ab

b

a

b

a

Facial and meridional isomers of 3 3Ma b complex

(5) Mabcdef is expected to give 15 isomers. 26 C . a to f are unidentate ligands.

iii) Optical isomerism:(1) Two isomers which have almost identical physical and chemical properties like mp, bp, density, colour

etc., but differ in the way they rotate the plane-polarised light are called optical isomers.(2) Optically active compounds exist in pairs and are known as stereoisomers or enantiomers. These

isomers aer non-superimposable mirror images of each other.(3) Any molecule which contains either a centre of symmetry or a plane of symmetry will not show optical

isomerism.(4) Optical isomerism is rarely observed in square planar complexes. Tetrahedral complexes of the

type[ ( ) ]2M AB [AB = bidentate ligand] do give optical isomers as shown in figure especially where M

= Be, B etc.M

A

B

A

B

M

A

B

A

B

\

(5) (a) Optical isomerism is very common with octahedral complexes.

(b) But , , , ( ) , ( ) , ( ) ,5 4 2 3 3 3 2 2 2Ma b Ma b Ma b M AA M AA ab M AA a b ( )( ) 2M AA BB a ,do notshow optical isomerism since they have symmetry element.(c) A few typical examples which show optical activity are



[188]

3 2 3 3

2 4 2 4 2 4 2 43 3 3 3, , , ( )Co en Ir C O Cr C O Al C O C O Oxalate

Co

2H N

2H N

2H N

2H N

2H C

2H C

2CH

2CH

2CH

2CH

Co

N

2NO

2NON

N

N

en

en

Co

N

2O N

2O N N

N

N

en

en

Co

2H N

2NH

2H C

2H C

2CH

2CH

2CH

2CH3 3

2NH

2NH

2H N

2H N2NH

2NH

(d)

2 22 2

.

sin .

Co en NO and Cis Co en Cl are optically active

Trans isomer is not optically active ce it has symmetry element Not unsymmetrical

Cis

Illustration 5: How do you distinguish between the following pairs of isomers?

i) [ ( ) ] [ ( ) ]B3 5 3 5Cr NH Br Cl and Cr NH Cl r

ii) 2 2 2 2 34 6.2Co H O Cl Cl H O A and Co H O Cl B

Solution:

i) The isomers can be distinguished by using 3AgNO reagent. One gives curdy precipitate of AgClsoluble in ammonia while the other will form light yellow precipitate of AgBr partially soluble inammonia.

ii) A B

3AgNO 1 mol of AgCl 3 mol of AgCl

Molar Conductivity 60 4201 2 1( )Ohm cm mol

Wt.Loss on Conc. 2 4H SO Loss of 22H O No wt.lossCation exchange resin 1 mol of HCl 3 mol of HCl

3RSO H

• Werner’s Theory Of Coordination Compounds(1893): Postulatesi) Most elements exhibt two types of valenceis: (a) primary valency and (b) secondary valency.

a) Primary valency: This corresponds to oxidation state of the metal ion. This is also called principal,ionisable or ionic valency. It is satisfied by negative ions and its attachment with the central metal ion isshown by dotted lines.

b) Secondary or auxiliary valency: It is also termed as coordination number (usually abbreviated as CN)of the central metal ion. It is non-ionic or non-ionisable (i.e. coordinate covalent bond type). This issatisfied by either negative ions or neutral molecules. The ligands which satisfy the coordination numberare directly attached to the metal atom or ion and shown by thick lines. While writing down the formulaethese are placed in the coordination sphere along with the metal ion. These are directed towards fixedposition in space about the central metal ion, e.g. six ligands are arranged at the six corners of a regularoctahedron with the metal ion at its centre. This postulate predicted the existence of different types ofisomerism in coordination complexes and after 19 years Werner actually succeeded in resolving various



[189]

coordination examples into optically active isomers.

.3 3C oC l 6NH or

Co

H 3N

H 3N

Cl

NH 3

NH 3

Cl

ClNH 3

NH 3

–[( ( ) ] ( )III 33 6 3C o N H C l

Co

H 3N

H 2O

Cl

NH 3

NH 3

Cl

ClNH 3

NH 3

.3 3 2CoCl 5NH H O or–[( ( ) ( )] ( )III 3

3 5 2 3C o N H H O C l

.3 3C oC l 5 N H o r

Co

H 3 N

H 3 NC l

NH 3

C lNH 3

NH 3

C l

–[( ( ) ] ( )III 23 5 2C o N H C l C l

.3 3 2C oC l 4 N H H O or–[( ( ) ]III

3 4 2C o N H C l C l

Co

H 3 N

H 3 NC l

C l

NH 3

C l

NH 3

. [ ( ) ]III 03 3 3 3 3CoCl 3NH or Co NH Cl

Co

H3N

Cl

Cl

NH3

Cl

NH3

ii) Every element tends to satisfy both its primary and secondary valencies. In order to meet this requirementa negative ion may often show a dual behaviour, i.e. it may satisfy both primary and secondary valenciessince in every case the fulfillment of coordination number of the central metal ion appears essential .

iii) Basis of Werners theory: Different isomers, color of the complexes, precipitation, electrical conductivity,Ion exchange studies, dipole moment, dehydration temperature.

Characteristic of Co(III) amminesAmmines (i.e. No. of Cl– ions Molar Total No. of Charge type IonicComplexes Precipitated conductivity ions given on ions Formulation

as AgCl by range by complexAgNO3 (Ohm-1cm2 mol-1) in soln.

CoCl3.6NH3 3(100%) 430 4 (3+,-1) [CoIII(NH3)6]3+(Cl–)3

CoCl3.5NH3. H2O 3 (100%) 430 4 (3+,1-) [CoIII(NH3)5(H2O)]3+(Cl–)

CoCl3.5NH3 2(66.66%) 250 3 (2+,-1) [CoIII(NH3)5Cl]2++(Cl–)CoCl3.4NH3 1(33.33%) 100 2 (1+,1-) [CoIII(NH3)4Cl2]+Cl–

CoCl3. 3NH3 0 ( -- ) 0 - - [CoIII(NH3)3Cl3]10

(non-electrolyte)

• Effective Atomic Number: (EAN)1) Sidgwick, with his effective atomic number rule, suggested that electron pairs from ligands were added

until the central metal was surrounded by the same number of electrons as the next noble gas.

2) [ ( ) ]4 6K Fe CN (potassium ferrocyanide): Fe2+ ; 24e 4–6[Fe(CN) ] = 24 (6 2) 36 (Kr - The

nearest noble gas). The EAN rule correctly predicts the number of ligands in many complexes.



[190]

3) Effective atomic numbers of some metals in complexesAtom Atomic No. Complex Oxidation state Ligand Electrons EANCr 24 [Cr(CO)6] 0 12 36Fe 26 [Fe(CN)6]4- 2 12 36Fe 26 [Fe(CO)5] 0 10 36Co 27 [Co(NH3)6]3+ 3 12 36 [Kr]Ni 28 [Ni(CO)4] 0 8 36Cu 29 [Cu(CN)4]3- 1 8 36Pd 46 [Pd(NH3)6]4+ 4 12 54 [Xe]Pt 78 [Pt(Cl6)]2- 4 12 86 [Rn]Fe 26 [Fe(CN)6]3- 3 12 35Ni 28 [Ni(NH3)6]2+ 2 12 38Pd 46 [PdCl4]2- 2 8 52Pt 78 [Pt(NH3)4]2+ 2 8 84

4) There are, however, a significant number of exceptions where the EAN is not found to have a noble gasconfiguration.

a) 4 : 27 4 2 35Co CO , In such cases the complex has odd electron. 4Co CO is

therefore unstable and dimerises to form 2 8Co CO .

b) 5 : 25 5 2 35Mn CO

5Mn CO is unstable and 2 10Mn CO is stable.

c) 4 536Co CO and Mn CO e Kr

are stable as they obey EAN rule.

d) 6 6: 23 12 35 ,V CO e V CO is stable. 6V CO does not dimerise as it has complete coordination

sphere (coordination no.6)

5) 2

3 6 : 25 6 2 37Co NH e

3

3 6 : 24 6 2 36Co NH e

3

3 6Co NH

is more stable than 2

3 6Co NH

.

2

3 6Co NH

can be easily oxidised by air 2O to 3

3 6Co NH

.

6) NO is considered as 3e donor. 3 2CO NO

From 6Cr CO , one can get 3 2 4Cr CO NO and Cr NO . No other complex can form.

4: 24 4 3 36Cr NO Kr .

• Valence Bond Theory (Pauling)1. Pauling used hybridization theory to derive the geometry of the complex. The basis of this theory is the

magnetic property of the complexes. He classified ligands into ‘Strong field’ (Low spin complexes) and ‘Weakfield’ (High spin complexes). The complexes can be diamagnetic or paramagnetic. If paramagnetic, the

magnetic moment 2n n BM , n = no.of unpaired electrons.



[191]

2. Strong field and weak field ligands:

(a) 4

6Fe CN

6 2 2 6: 3 4 , : 3Fe d s Fe d

2 3d sp hybridization octahedral.

( )Diamagnetic Experimentally shown

CN is a SFL, Low spin complex

Inner orbital complex (uses inner 3d orbital)

(b) 3 3 56

: : 3Fe CN Fe d

3

6:Fe CN

2 3d sp hybridization octahedral paramagnetic, low spin 1 2 3 1.73 BM

CN is a strong field ligand. Inner orbital complex.

4 6K Fe CN is diamagnetic and 3 6

K Fe CN is paramagnetic. Both of them can be

differentiated.

(c) 3 3 56 , ; 3FeF Fe d

3 2sp d octahedral paramagnetic, HIgh spin complex. 5 5 2 35 5.87 BM outer

orbital complex (uses outer 4d orbitals) 5 5 2 35 5.87 BM

Stereochemistry

(a) 8 24, ;3 4Ni CO Ni O d s

(CO is a strong field ligand. The complex was found to be diamagnetic experimentally.)



[192]

3sp Hybridization Tetrahedral

(b) 24NICl

is found to be paramagnetic with a magnetic moment of 2.84 BM.

3sp , tetrahedral.

(c) 2

4Ni CN

is found to be diamagnetic.

2

4:Ni CN

2dsp sq.planar

(d) 24PtCl

is found to be diamagnetic.

2 8:5Pt d

2dsp , square planar

Note that 24NiCl is paramagnetic but 2

4PtCl is diamagnetic. It is not thatCl is acting as weak orstrong field ligand. Its field strength does not change. But the 5d orbitals in Pt are more open, outer andexposed,so it feels the Cl field strong and electrons pair up.(e) [FeCl4]–. The electronic configuration of Fe3+ ion is 3d

5

Since Cl– ion is a weak field ligand it is unable to pair the unpaired electrons and hence, the Cl– ion uses 4s and4p orbitals to form a tetrahedral complex of sp3 hybridisation.

• Illustration-6: Calculate the magnetic moment of the “Brown ring” complex.

“Brownn ring” complex is 22 5

Fe H O NO

, 1 2, 1x O x

6 2 1 6 1: 3 4 , : 3 4Fe d s Fe d s

1 :Fe

2

2 5Fe H O NO

3 2sp d , octahedral ‘outer orbital complex.

Paramagnetic, 3 3 2 15 3.87 BM .

Illustration-7:. All octahedral Ni(II) complexes are paramagnetic and outer orbital complexes. Explain.



[193]

2 2 83 6

, ; 3Ni NH Ni d

2

3 6:Ni NH

3 2 , 2.84sp d BM

On pairing up, we do not get 2 3d sp . So no pairing up.

2

2 6Ni H O

3 2 , 2.84sp d BM Irrespective of whether the ligand is strong field or weak field ligand all the complexes are outer orbital andparamagnetic.

Illustration 8: 33 6[Co(NH ) ] is diamagnetic and 3–

6[CoF ] is strongly paramagnetic. Explain

Solution:

3Co

33 6[Co(NH ) ]

3–6[CoF ]

2 3d sp

3 2sp d

diamagnetic due to paired electrons

Paramagnetic due to four unpaired electrons

3Co has 63d configuration with four unpaired electrons in ground state. In presence of

3NH (strong ligand) all the unpaired electrons in 3Co get paired and thus

33 6[Co(NH ) ] has 2 3d sp hybridization (octahedral structure), thus it is diamagnetic (no electron unpaired).

–F is a weak ligand hence six lone pairs of six

–F are filled in outer d-orbitals of 3Co which has now four electrons unpaired. Thus 3–6CoF has 3 2sp d hybridization

in 3Co and is thus paramagnetic due to unpaired electrons.

• FAILURE OF VB THEORY:

(a) Pauling VB theory could not explain satisfactorily the geometry of 2

3 4Cu NH

. 2 93Cu d

2

3 4:Cu NH

3sp hybridization, Tetrahedral. But the actual geometry (experimentally) is found to be squareplanar. This was explained as

2

3 4:Cu NH

(b) It could not explain the color of the complexes.



[194]

(c) It could not explain why certain ligands act as strong field ligands and others as weak field ligand.

Table: Hybridization and Geometry of the complexes:

Coordination No.

Hybridization Geometry Examples

2 Sp Linear 1

3 2 2Ag NH Ag CN

1

3 2 2,Cu NH Cu CN

1

32 2,Au CN Au NH

3 (rare)

2Sp Trigonal planar

13HgI

4 3Sp Tetrahedral 2 14 4 4, ,BeCl AlCl FeCl ,

24 , , ,CoX X Cl Br I NCS

24 , , ,ZnX X Cl Br I NCS

24 , , ,CdX X Cl Br I NCS

24 , , ,HgX X Cl Br I NCS

2 24 4 4, ,MnCl MnBr Ni CO , 2 2 2

4 4 4, ,NICl SnCl GeCl 4 2dsp Square

planar 2

4 2,Ni CN Ni DMG

DMG Dimethyl glyoxime ,

24 ( , , , , )PtX X Cl Br I NCS CN

24 , , , ,PdX X Cl Br I NCS CN

2

3 22 2,Pt NH Cl Pt en

5 (rare)

3sp d Trigonal bipyramid

5Fe CO , 43Zn tu SO 2

4Ctu Itiourea SO is abidentate ligand) 5

(rare) 3dsp Square

pyramid 3

5Ni CN

6 2 3d sp Octahedral 4 3

6 6,Fe CN Fe CN

3 3

3 6 3Co NH Co en

3 3

3 6 6,Cr NH Cr CN

6 3 2Sp d Octahedral 3

2 6Fe H O

, 36FeF

, 2

2 6MN H O

2 2

3 26 6Ni NH Ni H O

, 2

3Ni en

7,8,9,12 (rare)

337 2 29 12, ,ZrF Nd H O Lu H O

• Ligand field theoryShapes of d-Orbitals: Since d orbitals are often used in coordination complexes it is important to study theirshapes and distribution in space. The five d orbitals are not identical and the orbitals may be divided into two

sets. The three 2gt orbitals have identical shape and point between the axes, x, y and z. The two ge orbitals

have different shapes and point along the axes. Alternative names for 2gt and ge are d and d respectively.



[195]

x

2gt

orbitals(d )

x y

y z z

xyd xzd yzd

+-

+ -

- +

+ -

- +

+ -

• (1) Ligand Field Splitting in Octahedral Complex: Let us consider the case of six ligands forming anoctahedral complex. For convenience, we may regard the ligands as being symmetrically positioned along theaxes of a Cartesian co-ordinate system with the metal ion at the origin. To simplify the situation, we canconsider an octahedral complex as a cube, having the metal ion at the centre of the body and the 6 ligands atthe face centres

and if we take the metal ion as the origin of a Cartesian co-ordinate, the ligands will be along the axes. It isobvious that not all of the orbitals will be affected to the same extent when the ligands approach the metal ion.

The orbitals lying along the axes 2 2 2z x yd and d will be more strongly repelled than the orbitals with lobes

directed between the axesdxy, dxz, dyz). The d-orbitals are thus split into two sets with the –2 2 2z x yd and d at a

higher energy than the other three.

2y2x2zd,d

dxy, dyz, dxz

0

• Outer orbital and Inner orbital complexesa) In a weak ligand field such as [CoF6]

3–, the approach of the ligand causes only a small split in theenergy level. O < P(pairing energy)



[196]

4 4 2 24 4.87 .B M

Since the ligand is a weak field ligand, its repulsions with the electrons in 2 2 2z x yd and d orbitals are very

less (or) in other words we can say that the electrons in 2zd and 2 2x yd cannot move away from theapproaching ligands since they have insufficient energy to pair up with the electrons in dxy, dyz and dxzorbitals.Thus there are no vacant orbitals in the 3d shell and the ligands occupy the first six vacant orbitals (one4s, three 4p and two 4d). Since outer d orbitals are used, this is an outer orbital complex. The orbitalsare hybridised and are written sp3d2 to denote this. Since none of the electrons has been forced to pairoff, this is a high spin complex and will be strongly paramagnetic because it contains 4 unpaired 3delectrons.

(b) Under the influence of a strong ligand field as in the complex [Co(NH3)6]3+, the approach of the ligand

causes a greater split in the energy level. 0 > P

Since, the split is very high, we can say that the energy difference between the two sets of orbitals is much

greater and this energy difference is sufficient to allow the electrons in 2 2 2z x yd and d orbitals to move into the

half filled dxz, dxy and dyz orbitals, even though this pairing requires energy. We can also view this like, the ligandrepel the electrons in higher energy level to an extent such that they get paired up against Hund’s rule

The 2zd and 2 2x yd orbitals become vacant. The six ligands each donate a lone pair to the first six vacant

orbitals, which are: two 3d, one 4s and three 4p. Inner d-orbitals are used and so this is an inner orbitalcomplex. The orbital are hybridised and written d2sp3 to denote the use of inner orbitals.Since, the orginal unpaired electrons have been forced to pair off, there is a low spin complex and is in factdiamagnetic.The inner and outer orbital complexes may be distinguished by magnetic measurements. Since the outerorbital complexes use high energy levels, they tend to be more reactive. The inner orbitals are sometimescalled inert orbitals.

(c) Distribution of d-electrons in 2gt and ge sets in strong(er) and weak (er) octahedral ligand fields.

Ions Strong (er) field (low spin or spin paired Weak (er) field (high -spin or spin freeComplexes) (0 > P) complexes ) (0<P)



[197]

p q2g gt e n s p q

2g gt e n sConfiguration Configuration

d1 1 02g gt e 1 1/2 1 0

2g gt e 1 1/2

d2 2 02g gt e 2 1 2 0

2g gt e 2 1

d3 3 02g gt e 3 3/2 3 0

2g gt e 3 3/2

d4 4 02g gt e 2 1 3 1

2g gt e 4 2

d5 5 02g gt e 1 1/2 3 2

2g gt e 5 5/2

d66 02g gt e 0 0 4 2

2g gt e 4 2

d7 6 12g gt e 1 1/2 5 2

2g gt e 3 3/2

d8 6 22g gt e 2 1 6 2

2g gt e 2 1

d9 6 32g gt e 1 1/2 6 3

2g gt e 1 1/2

d10 6 42g gt e 0 0 6 4

2g gt e 0 0

Factors affecting the magnitude of O

i) Oxidation state of the metal ion: The magnitude of O increases with increasing ionic charge on thecentral metal ion. As the ionic charge on the metal ion increases greater is the attraction for the ligands,

greater the repulsion and hence greater the magnitude of O . 3 4

6 6Fe CN Fe CN

ii) Nature of the ligands: Based on experimental observation for a wide variety of complexes, it is possible

to list ligands in order of increasing field strength in a spectrochemical series. Although it is not possibleto form a complete series of all ligands with a single metal ion, it is possible to construct one fromoverlapping sequences, each constituting a portion of the series:

2 3 2F H O Cl NH en NO CN CO (Increasing order of O ).

NH3 produces a greater splitting than H2O. 3 , ,NH CN CO , en are strong field ligands. 2,F H O

are weak field ligands.

• (2) Ligand Field Splitting in Square Planar Complex: If the central metal ion has eight

d-electrons( 2Ni , these will be arranged as

In a weak octahedral ligand field, a regular octahedral complex is thus formed by using outer d-orbitals.However,

under the influence of a strong ligand field, the electrons in the 2zd and 2 2x yd orbitals may pair up, leaving onevacant d-orbital, which can accept a lone pair from a ligand. Consider an octahedral comple, when two ligandsin z - direction are removed, then a square planar complex results.When the two axial ligands ( in z - direction) are removed. z containing orbitals will be come lower in energy

and xy containing orbitals will become higher in energy. 2 2x yd

orbital is involved in bonding. Strong field

ligands usually give rise to square planar complexes and are diamagnetic. 1.33SP O

Eg:- 2 224 34 4, ,Ni CN PtCl Pt NH



[198]

2

4Ni CN

is a square planar where as 2

4NiCl is tetrahedral since CN is a strong field ligand.

• (3). Ligand Field Splitting in Tetrahedral Complexes: A regular tetrahedron is related to a cube with anatom at the centre and four of the eight corners occupied by ligands.

y x

z

The directions x,y and z point to the centre of the faces. The 2Zd and 2 2x yd orbitals point along x,y and z axisand dxy, dyz and dxz orbitals point in between x,y and z.The directions of approach of the ligands does not

coincide exactly with either the 2zd and 2 2x yd orbitals (or) the dxy, dyz and dxz orbitals. The approach of ligandsraises the energy of both sets of orbitals, but since the dxy,dyz and dxz orbitals correspond more closely to the

position of the ligands, their energy increases most and the 2Zd and 2 2x yd orbitals are filled first. This is

opposite to what happens in octahedral complexes. Ot and so many tetrahedral complexes are

paramagnetic and high spin complexes. 4 0.45 ,9t O O SP O t .

Consider, 4FeCl , Ligand field theory : 3 5:3Fe d

5 5 2 35 5.87 .B M



[199]

• Metal Carbonyls

a) The homoleptic carbonyls (compounds containing carbonyl ligands only) are formed by most of the transitionmetals. These carbonyls have simple, well defined structures. Tetracarbonylnickel (0) is tetrahedral,pentacarbonyliron(0) is trigonal bipyramidal while hexacarbonylchrominum (0) is octahedral.

Decacarbonyldimanganese(0) is made up of two Mn(CO)5 units joined by a Mn-Mn bond.Octacarbonyldicobalt (0) has a Co-Co bond bridged by two CO groups

CO

NIOC CO CO

Ni(CO)4Tetrahedral

CO

FeOC

OCCO

COFe(CO)5

Trigonal bipyramidal

CrCO

COOC

OC COCO

Cr(CO)6 Octahedral

Mn

COCO

OC Mn

OC CO

CO

CO

CO

OC CO

[Mn2(CO)10]

Co Co

COOCOC

OC

CO

CO

CO CO

[Co2(CO)8]

(b) Bonding in metal carbonyls: (a) - donation

Empty Metal d - orbitals Filled CO orbitalsFilled CO orbitals overlap with empty metal d - orbitals.

(b) - back bonding

Filled metal d - orbitals overlap with empty * molecular orbitals of CO.



[200]

(c) Resonance forms can be represented as

M C O M C O The M - C bond order increases and bond length is expected to decrease. The C - O bond order

decreases and C - O bond length increases when compared to C - O bond length in uncoordinatedCO. More the back bonding the lesser will be C - O bond.(d) The - donation and bonding order and greater will be C - O bond length back bonding occurs

synergistically. Both occur simultaneously.(e) Since - back bonding requires filled metal d - orbitals, carbonyls are usually formed in lower

oxidation state. 3

36 5 6,Cr CO Fe CO Cr NH

is stable but 3

6Cr CO

is not known.

(f) Both CO and 2N are isoelectronic (14e). But metal carbonyls are stable whereas metal dinitrogen

M N N complexes are less stable. In metal carbonyls, the * molecular orbital is of lower

in energy and can overlap with metal d - orbitals. In 2N , the * - molecular orbital energy lever is

higher and cannot overlap with the metal filled d- orbitals. No back donation possible in 2N .

(g) Usually a ligand donate an electron pair to metal. In CO, it can accept electron from the metal. It is

known as - acceptor ligand. 3, , ,CO CN NO PPh (Vacant d - orbital) can act as - acceptor

ligands. 3 2,NH H O are only - donors and not - acceptor.

• STABILITY OF COORDINATION COMPOUNDS For a given metal and ligand the stability is generally greater, the greater the charge on the metal ion. Thus,stability of coordination entitites of ions of charge 3+ is greater than the entities of 2+ ions.

3 4

6 6Fe CN Fe CN

Further. for the divalent ions of the first row transition elements, irrespective

of the ligand involved, the stabilities vary in the Irving -Williams order:II II II II II IIMn Fe Co Ni Cu Zn .

3 2

2 2 26 6 6;A H O Mg H O Na H O

The metal ions, ‘Class A acceptors like metals of groups 1 and 2, the inner transition elements and the early

members of the transition series (groups 3 to 6 like 4 6 7, ,Zr Cr Mn ) form their most stable coordinationentities with ligands containing N, O or F donor atoms.The metal ions, class B acceptors like the transition elements - Rh, Pd, Ag, Ir Au and Hg having relatively fulld orbitals form their most stable complexes with ligands whose donor atoms are the heavier members as P,

S, I groups. 3 36 6FeF FeI

; 2 24 4HgI HgF

The stability also depends on the formation of chelate rings. If L is an unidentate ligand and L-L, a didentateligand and if the donor atoms of L and L-L are the same element, then L-L will replace L. The stabilisation due

to chelation is called the chelate effect. 3 3

33 6Co en Co NH

. It is of great importance in biological

systems and analytical chemistry. The chelate effect is maximum for the 5- and 6- memebered rings. Ingeneral, rings provide greater stability to the complex.If a multidentate ligand happens to be cyclic, a further increase in stability occurs. This is termed the macrocycliceffect.• ORGANOMETALLIC COMPOUNDS AND THEIR APPLICATIONSA) These compounds may be classified into three classes

i) Sigma bonded complexesIn these complexes , the metal atoms and carbon atom of the ligand are bonded with a sigma bond in whichligand contributes one electron and is therefore called one electron donor



[201]

EXAMPLESa) Grignard Reagent R –Mg –X where R is a alkyl or aryl group and X is halogen

b) 3 3 2 5 2 3 2 2 54 4 6 6CH Li, CH Sn, C H Pb,Al CH ,Al C H etc

CH3

AlCH3

CH3

CH3

AlCH3

CH3

Bridging groups

ii) pie () bonded organometallic compoundsThese are the compounds of metal with alkenes, alkynes, benzene and other ring compounds.

e.g. Zeise’s salt 23 2 4K PtCl C H

Cl

Cl

Pt

Cl

H

C

H

CH H

K+

Potassium trichloro ( 2 ethylene) platinate(II)The coordinated alkene will have a longer C - C bond than in pure alkene. This is due to the pumpingof metal d electrons into * orbitals of the alkene.

Ferrocene 55 5 2

Fe C H -1

-1

Fe +2

bis( 5 - cyclopentadienyl) iron(II), it is a Sandwich complex and diamagnetic.

Dibenzenechromium 66 6 2

Cr C H Cr

bis( 6 - benzene) chromium (O)

iii) & bonded organometallic comp. eg Metal carbonyls ; 4 6,Ni CO Cr O

b) Some of the applications of organometallic compounds are as follows1) Tetraethyllead is used as antiknock compound in gasoline2) Wilkinson’s catalyst [Rh(PPh3) 3Cl] is used as homogeneous catalyst in the hydrogenation of alkenes.3) The extraction and purification of nickel is based on the formation of organometallic compound4) The formation of Ni(CO)4 at 50-800 C and its decomposition at 150-1800C is used in the extraction of

nickle by MONDS PROCESSZeigler Natta catalyst (trialkyl aluminium + titanium tetrachloride) acts as a heterogeneous catalyst inthe polymerisation of ethylene to polyethylene.

5) 2 8Co CO Catalysis: Hydroformylation reaction

2 2 2 3 2CH CH H CO CH CH CHO



[202]

6) Wackers oxo process 2 2PdCl CuCl

2 2 2 3CH CH H O CH CHO Application of coordination compounds:

1). Qualitative Analysis:

(a) AgCl is soluble in aq. 3NH due to complex formation 3 2Ag NH Cl .

(b) 3

2. 2

DMGaq NH

Ni Ni DMG Scarlet or Rosy red ppt.

(c) 232 5

4

.dil HClFe Fe H O NCS

NH SCN

Blood red color

(d) 22 4

4

NH SCNCo Co NCS

acetone Blue color

(e) Sodium nitro prusside: 2 5Na Fe CN NO . Note that NO is +1 state. Oxidation state of Fe is

2 5 1 0, 2x x . This is used to test the sulphide ion in alkaline medium (Lassighnes test)

2 225 5

Fe CN NO S Fe CN NO SViolet colour

2). Quantitative Analysis:(a) Complexometric titrations using 2Na EDTA (EDTA). Many metal ions form complexes with EDTA.

By this titration, one can estimate 2 2 2 2 2 2, , , , ,Zn Cd Co Ni Ca Mg etc.(b) Molarity is used rather normality

Eg: 1000 cc - 1MEDTA solution 63.54 g of 2Zn .

(c) Hardness of water is determined by EDTA method. 2Ca and 2Mg are estimated together in water

by EDTA titration. Hhardness of water is expressed as mg of 3CaCO in 1 lit. of water. (PPm)For the calculations use

1000 cc - 1 MEDTA solution 100 g of 3CaCO .3) Biological systems:

(a) Haemoglobin: Heme + globin (globular protein).Heme : 2Fe Porphyrin ring (made up of 4 pyrrole rings, macrocyclic ligand).



[203]

deoxy Hb, 4 22 ggt e oxy Hb 6 0

2 ggt eHigh spin complex Low spin complex

Everytime in our body the transition from !HS LS occurs

3, ,CO CN pph are poisonous as they bind to iron atom irreversibly.(b) Carboxy peptidase carbonic anhydrase: Zn containing enzyme.

(c) Vitamin 12B : Cyano cobalamine 2Co corrin ring .A naturally occuring compound with Co - C bond!

(d) Nitrogenase : Atmospheric fixation of 2N by Azotobacterium or Rhizobium. Nitrogenase can reduce

2N to 3NH . It has Fe - Mo - S cluster complex.(e) Superoxide dismutase: Cu - Zn enzyme

(f) Cisplatin : 3 22Cis Pt NH Cl anti cancer drug.

(g) Chlorophyll: 2Mg + Porphyrin ring + Phytin photosynthesis. 2 2 6 11 5 2nCO H O C H O O

KEY CONCEPTS Transition elements have parlty filled d-orbital. The covalent radii of transition elements decrease from left to right across a row, until near the end when

size increaes slightly. All the transition elements are metals and good conductors of heat and electricity, have a metallic luster

and are hard strong & ductile. Low atomic volume and high denisty. Melting and boiling points of transition elements are generally very high. The first ionization energy gradually increases from left to right. Generally, the ionization energies of

transition elements are intermediate between those of S & P-block elements. Transition elements usually exist in several different oxidation states and the oxidation states change in

units of one. Compounds of transition element and inner transition elements are colour due to presence of incomplete

d-or f-sushells. When solutions containing two or more simple stable salt s in stoichiometric proportions are allowed to

evaporate, addition compounds are formed Addition compounds which lose their identify in solution are called double salts. The neutal molecules or ions which are linked directly with the central metal atom ion are called ligands. The total number of atoms of ligands that can coordinate to the central metal atom/ion is called coordination

number The central metal and ligands are enclosed in a square bracket called coordination sphere The total number of electrons, which the central metal atom appears to possess in the complex,

including those gained by it in bonding is called effective atomic number (EAN) Primary valency corresponds to the oxidation state of the metal ion. Secondary or auxiliary valency is also termed as coordination number of the central metal . It is non-

ionic or non-ionisable, but directional. Sidgwick theory explains the stability of metal carbonyls using EAN rule. Paulings valence bond theory uses the hybridization to explain the geometry and the magnetic nature

of the complexes. Ligand field theory explains the splitting of d orbitals in octahedral, tetrahedral and square planar

complexes. Direct M - C or bond should present in an organometallic compound.

Documents

BANSAL CLASSES BREAK Co Ordination Compound