9.1 Explain the bonding in coordination compounds in terms of Werner’s postulates.
Werner his theory of coordination compounds and gave some postulates. The main postulates are:
1. In coordination compounds metals show two types of linkages or valences namely primary valency and secondary valency.
2. The primary valences are generally ionisable and are satisfied or balanced by negative ions.
3. The secondary valences are non-ionisable. These are satisfied by either neutral molecules or by negative ions. The secondary valence is equal to the coordination number (No. of atoms surrounding the metal) and is constant for a metal.
4. According to different coordination numbers, the ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements.