. Isomerism in coordination compounds We have already learnt the concept of isomerism in the context of organic compounds, in the previous year chemistry classes. Similarly, coordination compounds also exhibit isomerism. Isomerism is the phenomenon in which more than one coordination compounds having the same molecular formula have different physical and chemical properties due to different arrangement of ligands around the central metal atom.
The following flow chart gives an overview of the common types of isomerism observed in coordination compounds, Isomerism Ionisation isomerism Hydration isomerism Linkage isomerism Coordination isomerism Geometrical isomerism Optical isomerism Structural Isomerism Stereo Isomerism arises due to the difference in the structures of coordination compounds arises due to different spatial orientation of ligands around the metal ion Figure . Isomerism in coordination compounds . . Structural isomers The coordination compounds with same formula, but have different connections among their constituent atoms are called structural isomers or constitutional isomers.
Four common types of structural isomers are discussed below. XII U5 Coordination XII U5 Coordination - - - - Linkage isomers: This type of isomers arises when an ambidentate ligand is bonded to the central metal atom/ion through either of its two different donor atoms. In the below mentioned examples, the nitrite ion is bound to the central metal ion Co + through a nitrogen atom in one complex,and through oxygen atom in other complex. [Co(NH ) (NO )] + + N Co H N H N NH NH NH + N Co H N H N NH NH NH Figure .
Linkage isomers Coordination isomers: This type of isomers arises in the coordination compounds having both the cation and anion as complex ions. The interchange of one or more ligands between the cationic and the anionic coordination entities result in different isomers. For example, in the coordination compound, [Co(NH ) ][Cr(CN) ] the ligands ammonia and cyanide were bound respectively to cobalt and chromium while in its coordination isomer [Cr(NH ) ][Co(CN) ] they