Q. Explain about Coordination Isomerism?

Coordination Isomerism: If the complex is a salt having both cation and anion as complex ions then the ligands can exchange position between the cation and the anion. This will result in the formation of coordination isomers. Let us consider one such series:

[Co (en) ₃][Cr(C₂O₄)₃] Co(en)₂ (C₂O₄)] [ Cr(en) (C₂O₄) ₂]

[Cr(en)₂(C₂O₄] [Co(en) (C₂O₄)₂] [ Cr(en)₃ (C₂O₄) ₂]

It is possible to have the same metal ion present in both cationic and anionic species as shown by the following example:

[Cr (en)₃[Cr(C₂0₄)₃ and [Cr(en)₂ (C₂0₄)I [Cr(en) (C₂O₄)₂]

Note that in the above example both the oxidation state of the metal ion and its coordination number is same in the cation and anion. Let us consider yet another example where the above condition may be different:

[P^II (NH₃)₄] [Pt^iv Cl₆ ]and [Pt^iv(NH₃)₄ Cl₂] [Pt^IICl₄]