contains introduction about co-ordination compounds

1. 1
Co-ordination Compounds

2. Double salt Vs complex salt
 Double salts : These are addition compounds in which
individual constituents retain there identity. Example :
Mohr’s Salt (FeSO4.(NH4)2SO4.6H2O)
FeSO4.(NH4)2SO4.6H2O → 𝐹𝑒2+
+ 2𝑁𝐻4+
+2SO42−
 Complex salts: They lose there identity in solid as well
as in liquid state. Example: K4[Fe(CN)6]
K4[Fe(CN)6] → 4𝐾+
+ 𝐹𝑒 𝐶𝑁 6
4 −

3. Who forms coordination compounds
and Why?
Mainly transition elements (d & f block elements) form complexes
because:
 small size of the ions
 higher nuclear charge
 high charge density
 presence of vacant
d-orbitals
 have a large polarizing
power and can attract lone
pairs from other atoms to
form complexes.
 Exhibits variable oxidat-
ion states (Fe+2 and Fe+3,
Cu+ and Cu2+)

4. 4
Werner's Theory of Coordination
Compounds
Alfred Werner in 1898 gave his theory of coordination compounds.
Metal atom in coordination compounds possess two types of
linkages or valences – primary and secondary.
The primary valences are normally ionisable and are satisfied by
negative ions.
The secondary valences are non – ionisable and are satisfied by
neutral or negative ions. It is equal to the coordination number and is
fixed for a metal.
The ions/groups bound by the secondary linkages to the metal have
characteristic spatial arrangements corresponding to different
coordination numbers.
Those spatial arrangements are called coordination polyhedral. The
species enclosed in square bracket are coordination entities or
complexes and the ions outside the square bracket are called counter
ions.

5. Primary Valency
oxidation state of central metal
atom
Number of ligands need to satisfy
the central metal atom charge
Primary valency of Fe in complex
K4[Fe(CN)6] is +2
Secondary Valency
coordination number of central
metal atom
Number of ligands attached to
the central metal atom
Secondary valency of Fe in
complex K4[Fe(CN)6] is 6

6. Some Basic Terms
Coordination entity
Central metal atom/ion
Ligands
Coordination number
Coordination sphere
Coordination polyhedron
Oxidation number of central metal atom
Homoleptic and Heteroleptic

7. Ligands and their Classification
Anionic Neutral Cationic
Cl-(chloro) NH3 (ammine) NO2
+
(nitrosonium)
CN-(cyano) H2O (aqua) N2H5
+
(hydrazinium)
O2-(chloro) NO (nitro)
OH-(hydroxo) CO (carbonyl)
C2O4
2-(oxalato) NH2CH2CH2NH2
(ethylene diamine)
AcO-(acetato)
On the basis of
charge
Anionic
Neutral
Cationic
On the basis of
number of
donor sites
Monodentate
Bidentate
Polydentate
On the basis of
bonding
Chelating
ligands
Ambidentate
ligands

8. 8