Question

A coordination complex [MX2L2], has a CN=4 and two unidentate ligands X and L. When the two L ligands are arranged opposite to each other in its geometry, it is called _______ isomer.

(a) cis

(b) trans

(c) fac

(d) mer

The question was posed to me during an interview.

This key question is from Isomerism in Coordination Compounds topic in chapter Coordination Compounds of Chemistry – Class 12

Answer 1

Correct option is (a) cis

To explain I would say: The shape of the complex will be square planar as the CN is 4 and isomerism cannot be observed in tetrahedral shapes (also CN=4). When a particular ligand in this type of complex is arranged opposite to each other, it is a trans isomer, else it is called a cis isomer.