Coordination Compounds

Werner’s theory was the first theory given for structures of Coordination compounds

It is named after Alfred Werner who gave this theory in 1823 and won a noble prize on this work in 1913. Alfred Werner is also known as the father of the coordination compounds

According to his theory:

Central metal atom of a coordination compound can possess two kinds of valencies i.e. primary valency and secondary valency, and these valencies determine the structure of a coordination compound

• Primary Valency: It is ionisable valency which shows the charge on central metal atom. Hence it is found by determining the oxidation state (O.S.) of central metal atom.

For example the primary valency of

• Secondary Valency: It is non-ionisable valency which determines the number of ligands attached to central metal atom. And it is calculated the same way (i.e. by determining the number of ligands attached to central metal atom).

For example the secondary valency of while secondary valency is represented by continuous line (3/4) . If the charge on ligand is not zero it is represented by both dotted as well as continuous lines

Below are some examples of how structure of coordination compounds are drawn using Werner Theory

Structure of coordination compounds

1)

2)

3)

4)

Facial isomer (Cis)                           Meridonial isomer (Trans)