JEE Main · 2024 · 30 Jan 2024 · Shift 2 · Coordination Compounds

A complex is optically active when it is chiral — that is, when it has neither a plane of symmetry nor a centre of symmetry. $cis\text{-}[{\text{Cr(ox)}}_2{\text{Cl}}_2{]}^{3-}$, $[{\text{Co(en)}}_3{]}^{3+}$, $cis\text{-}[{\text{Pt(en)}}_2{\text{Cl}}_2{]}^{2+}$ and $cis\text{-}[{\text{Co(en)}}_2{\text{Cl}}_2{]}^{+}$ each lack any internal symmetry element that would superimpose them on their mirror images, so all four are chiral and optically active. Their $trans$ counterparts, $trans\text{-}[{\text{Pt(en)}}_2{\text{Cl}}_2{]}^{2+}$ and $trans\text{-}[{\text{Cr(ox)}}_2{\text{Cl}}_2{]}^{3-}$, each possess a mirror plane through the two monodentate/axial ligands and are achiral. Four of the six complexes listed are optically active.