Question

Identify the type of isomerism exhibited by the following structures.

(a) Geometric isomerism

(b) Optical isomerism

(c) Linkage isomerism

(d) Coordination isomerism

This question was posed to me during an interview.

My question is taken from Isomerism in Coordination Compounds in section Coordination Compounds of Chemistry – Class 12

Answer 1

Correct answer is (c) Linkage isomerism

The explanation: Geometric and optical isomerism are types of stereoisomerism in which the chemical bonds remain same. The two structures shown have different chemical bonds between the central atom (Co) and the ligand group (NO2). Nitrate is an ambidentate ligand which can result in two forms in the entities it is present in. If it links through N atom, it forms nitrito-N form (NO2) as in figure i), and if it binds through O atom, it forms nitrito-O form (ONO) as in figure ii). This type of isomerism is called linkage isomerism.