This document discusses coordination chemistry and coordination compounds. It defines coordination chemistry as the study of compounds formed between metals and ligands. Coordinate covalent bonds are observed in these complexes. Coordination compounds can exist as either double salts, which fully ionize in polar solvents, or complex compounds, which partially ionize. Ligands are classified as monodentate, bidentate, or polydentate based on the number of donor atoms bonding to the central metal atom. Common examples of various types of ligands are provided.

1. Co-ordination Chemistry
By
Dr.S.Manimekalai
Assistant Professor of Chemistry
E.M.G.Yadava Women’s College
Madurai

2. Co-ordination Chemistry
Introduction
 It is the study of a class of compounds formed by
metals
 Coordinate covalent bonds are observed in
complexes
 These compounds are basically the compounds
of the d-block elements
 These compounds have major importance in
industries, metallurgy and pigment
 EDTA is a ligand that is used to determine the
hardness of the water. EDTA is also used for DNA
agarose gel.

3. Continue…..
The addition compound which is undergoing
 complete ionisation (called double salt) in polar solvent
 partial ionisation ( called complex compounds) in polar
solvent
Ex: double salt: KCl MgCl2 KCl.MgCl2.6H2O
H2O
H3O+ K+Mg2+Cl-
polar solvent complete
dissociation
Complex compounds:
K3[Fe(CN)6] K+ + [Fe(CN)6]-
polar solvent partial ionisation

4. Continue ……
[ M Lx ] y ionisation sphere
Central metal atom coordination number
ligand
co-ordination sphere
In complex form central metal atom acts as lewis
acid(electron pair acceptor )
Ligand acts as lewis base (electron pair donar)
Transfer of C-H σ bonding electrons is called agostic
interaction M C
H

5. Classification of ligands
1. Mono dentate ligands
 The ligands which only have one atom as the donor atom
Examples
Neutral molecules
H2O – aqua
CS - thio carbonyl
NS – thio nitrosyl
CH3-NH2 – methyl amine
CO - Carbonyl
NO - nitrosyl
NH3 - amine

6. (CH3CH2)3N - tri ethyl amine
(CH3)2NH – dimethyl amine
ph3P - triphenyl phosphene
(C2H5)3P – tri ethyl phosphene
PF3 - phosphorus tri fluoride ligand
C2H5-O-C2H5 – diethyl ether
O2 - dioxygen
N2 - dinitrogen
C5H5N – pyridine

7. Anions
F- - fluoro
Br- -Bromo
Cl- - Chloro
I- - iodo
OH- - hydroxo
H- - hydrido
SH- - mercapto
CN- - cyano
NC- - isocyano

8. CH3COO- - acetato
NH2
- - amido
NH2
- - imido
N3
- - azido
N3
- - nitrido
(CH3)2N- - dimethyl amido
CH3O- - methoxo
C2H5O- - ethoxo
O2
- - superoxo
O2
2- - peroxo
O2- - oxo

9. SO4
2- - sulphato
ONO- - nitrito
NO2
- - nitro
SCN- - thio cyanato
NCS- - iso thio cyanato
S2- - sulphido
SO3
2- - sulphito
Bidentate ligands
 ligands which have two atoms as the donor atoms
Examples:
NH2-CH2-CH2-NH2 - ethylene diamine (en)
PH2-CH2-CH2-PH2 - ethylene diphosphene (diphos)

10. CH3-CH(NH2)-CH2(NH2) - propylene diamine (Pn)
CH3-CH(NH2)-CH(NH2)-CH3 - butylene diamine (Bn)
CH3-C(CH3)(NH2)-C(CH3)(NH2)-CH3- tetra methylene diamine (tn)
NH2NH2 - hydrazine
O=C-O- - oxalato (ox2-)
O=C-O-
O=C O- - carbonato
O-
O=N O- - nitrato
O-

11. Polydentate ligands
Some ligands have many donor atoms
Example:
Tri dentate ligand- 3 donor atoms
NH2-CH2-CH-NH2-CH2-NH2 - Propylene triamine(pn)
Tetra dentate ligand- 4 donor atoms
NH2-(CH2)2-NH-(CH2)2-NH-(CH2)2-NH2- triethylene tetramine
penta dentate ligands- 5 donor atoms
NH2-(CH2)2-NH-(CH2)2-NH-(CH2)2-NH-(CH2)2-NH2- tetra ethylene
pentamine
EDTA (ethylene diamine tri acetato)