Question

How many stereoisomers does the following compound have?

(a) 0

(b) 2

(c) 3

(d) 4

This question was posed to me during an interview.

This interesting question is from Isomerism in Coordination Compounds in division Coordination Compounds of Chemistry – Class 12

Answer 1

Correct choice is (c) 3

For explanation: Firstly, the compound can have 2 geometric isomers, cis and trans, depending on whether similar ligands are placed adjacent to or opposite each other. Furthermore, one of them, i.e. the cis form is optically active and has two non-superimposable forms. This means that the cis form is both a geometric isomers as well as an optical isomer. Hence, there are 3 stereoisomers (1 geometric, 1 optical, 1 both geometric and optical).