how to find the oxidation state of complex compound

You can follow the following steps to find the oxidation state in a complex compound:

• If the complex is neutral : The sum of charges on the ligands and the central metal atom is equal to Zero.
• If the complex is positively charged : The sum of charges on the ligands and the central metal atom is equal to charge on the coordination sphere.
• If the complex is negatively charged : The sum of charges on the ligands and the central metal atom is equal to charge on the coordination sphere.

For example, let us find the charge on central metal ion in the following coordination compound:

[Fe(CN)₆]^4-.

Oxidation state of Iron = x

Charge on ligand CN^- = -1

So, x + (-1)x6 = -4

x – 6 = -4

x = 6 – 4

x = +2