prepared by dr. hoda el-ghamry lecturer of inorganic chemistry faculty of science-chemistry...

Prepared by Dr. Hoda El-Ghamry

Lecturer of Inorganic Chemistry

Faculty of Science-Chemistry Department

Tanta University

Inorganic Chemistry (2)

Coordination number and stereochemistry of complexes

The coordination no. shown by metals in complexes are 2-9, the

most common are 4 & 6Coordination number 2

The complexes having CN =2 are linear since this geometry provides the

minimum ligand repulsion

Cu+, Ag+, Au+ and in some cases Ag2+ form such complexes

Example: Cu(CN)2-, Cu(NH3) 2

+, Hg(CN)2 , [CuCl2] -

M LL

180

Coordination number 3

The possible geometries exhibited by the CN =3 is Equilateral triangular in

which the ligands are arranged at the corners of slightly distorted equilateral

triangle with the metal ion at its center

Example: [Hgl3] -L

L L

M120

120

120


Two possible geometries exhibited by complexes with CN =4

i) Tetrahedral

ii) Square planar

tetrahedral geometry

Example: ZnCl42-, Cu(CN) 4

2-, Cu(X) 4-, FeCl4

-

square planar geometry

Example: [Cu(en)2]2+, Ni(CN) 42-, [Cu(NH 3) 4 ]2+, PtCl4

2-


Complexes with CN = 5 imay be trigonal bipyramidal or square pyramidal

trigonal bipyramidal geometry

Square pyramidal geometry

Example: SnCl5- , [Fe(CO)5], CuCl5

3-

Example: vanadyl acetyl acetone [VO(acac)2]


This is the most common C.N formed by transition metal complexes. The

possible geometries exhibited by the CN =6 are Hexagonal planar , trigonal

prismatic and octahedral

Nomenclature of coordination compounds

Classification of coordination compounds

1) Cationic complexes [CrIII(H2O)4 Cl2]+

2) Anionic complexes [FeII(CN)6 ]4-

3) Ionic complexes [PtII(Py)4]2+ [PtIICl4]2-

4) Neutral complexes [CoIII(NO2)3 (NH3)3]0

For naming all the types of complexes mentioned above, the following

rules are followed:

5) For cationic, anionic and ionic complexes, the positively charged ion

is written at first followed by the negatively charged ion

Example: [CrIII(NH3)6 ] (NO3)3 Hexaamine chromium (III) nitrate

K2[PtIVCl6]2- Potassium hexachloro platinate (IV)

2) For Naming the complex cation or anion, the ligands are named at first

and the central metal is named last

i) Order of naming ligands

If there are two or more different types of ligands, the order of naming such

ligands is: negative ligands, neutral ligands and finally positive ligands.

ii) Naming of negative ligands:

If the anion name ends in –ide, -ite or ate, the final –e is replaced by O

SO32- Sulphite → sulphito SO4

2- Sulphate → sulphato

S2- Sulphide → sulphido NO3- Nitrate → Nitrato

Exceptions: F- (Fluoro), Cl- (Chloro), CN- (Cyano), O-2 (oxo), OH-

(hydroxo), O22 - (peroxo)

iii) The names of neutral ligands are not systematic

Special names are used for some ligands

H2O → (aqua), NH3 →(ammine), CO → (carbonyl), NO → (nitrosyl)

iv) Positively charged ligands

If the cation name ends in –in , we add -ium

Example: NH2-NH3+ Hydrazin→hydrazinium

v) The prefix di, tri, tetra, penta and hexa are used to indicate the number

of ligands

vi) When the name of the ligands include a number (e.g. ethylene diamine,

dipyridyl, triphenyl ohosphine) the prefixes bis-, tris, tetrakis, pentakis

and hexakis are used instead of di, tri, tetra, penta and hexa and in this

case the name of the ligand is placed between brackets.

Example: [CoIII(en)2 Cl2] Cl dichloro bis (ethylene diamine) cobalt (III)

chloride.

vii) For anionic complexes, the suffix ate is attached to the name of the

metal.

Example: [CrIII(NH3)6 ] (NO3)3 Hexaamine chromium (III) nitrate

K2[PtIVCl6]2- Potassium hexachloro platinate (IV)

viii) In order to indicate the oxidation state of the metal center, the name of

the metal ion is followed by the roman numbers I, II, III which is

added between brackets .

For negative oxidation state, the negative sign is added before the roman

number.

Example: [PtIVCl6]2- hexachloro platinate (IV)

[Co(CO)4]- tetracarbonyl cobaltate(-I)

[Ni(CN)4] 4- tetracyano nickelate (0)

Complexes of ambidentate ligand

Ambidentate ligands named by 2 ways:

1- by special names

M-NO2 Nitro NO2-

M-ON=O Nitrito

M-CN Cyano CN-

M-NC Isocyano

M-SCN Thiocyanato

NCS-

M-NCS Isothiocyanato

2- The symbol of the element coordinated with the metal ion is written after

the name of the ligand

Example: [PtIV(SCN)6] 4- hexathiocyanato-S- platinate(IV)

[PtIV(NCS)6] 4- hexathiocyanato-N- platinate(IV)

Bridging polynuclear complexes

The complexes having two or more metal atoms are called polynuclear complexes.

In these complexes, the bridging group is indicated in the complex formula,

separately. The Greek letter µ should be repeated before the the name of different

bridging ligand

Example: HO

CrIII Cr III(NH3)5(NH3)5 Cl5

µ- hydroxo-bis{penta amine chromium (III)} chloride

H2N

CoIII

OH

CoIII(NH3)4(NH3)4

µ- amido- µ- hydroxo octa amine dicobalt(III) ion

Metal to metal bonding

In complexes having metal to metal bonding, the prefix bi- is added before the

name of the metals forming a metal to metal bond

Example:

PtII PtII

Cl Cl

(NH2CH3)4(H3CH2N)4 2Cl-

Dichloro octakis( methyl amine) bi-platinum (II) chloride

prepared by dr. hoda el-ghamry lecturer of inorganic chemistry faculty of science-chemistry...

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