Chemistry - Coordination Chemistry Question with Solution | TestHub

Complex I ($[CoC{l}_3(N{H}_3{)}_3]$) exists as both fac (facial) and mer (meridional) geometrical isomers.

If Complex I is the fac-isomer, substituting two cis-$C{l}^{-}$ ligands with the bidentate $en$ ligand keeps the three $N{H}_3$ groups on a face, producing only the fac-isomer of Complex II (making A correct).

This resulting fac-isomer of Complex II contains a plane of symmetry, making it optically inactive (making C incorrect).

If Complex I is the mer-isomer, substitution yields only one product—the mer-isomer of Complex II—which also possesses a plane of symmetry and is optically inactive (making B incorrect and D correct).