What are linkage isomers? Give me an example

Linkage isomers are coordination compounds that have the same composition but differ in the connectivity of the ligand to the metal.

For example, a thiocyanato group could be connected to the metal atom by either the S atom or the N atom.

Typical ligands that give rise to linkage isomers are:

• thiocyanate, SCN⁻ and isothiocyanate, NCS⁻
• selenocyanate, SeCN⁻ and isoselenocyanate, NCSe⁻
• nitrite, NO₂⁻
• sulfite, SO₃²⁻

Two examples of linkage isomers are

• the violet thiocyanato-κ-S and orange thiocyanato-κ-N isomers [(NH₃)₅Co-SCN]²⁺ and [(NH₃)₅Co-NCS]²⁺

• the yellow nitrito-κ-N and red nitrito-κ-O isomers [(NH₃)₅Co-NO₂]²⁺ and [(NH₃)₅Co-ONO]²⁺