Which of the following is not optically active? — Coordination Compounds Chemistry Question

💡 Solution & Explanation

Step 1: Optical activity requires a molecule to be chiral, which means it must lack a plane of symmetry (σ) and a center of inversion (i). Step 2: The tris-chelated complexes [Co(en)3]^3+ and [Cr(Ox)3]^3- and the cis-isomer of [CoCl2(en)2]^+ are highly asymmetric and chiral, exhibiting optical activity. Step 3: The trans-isomer of [CoCl2(en)2]^+ possesses both a plane of symmetry and a center of inversion (as the two chloride ligands lie in trans-axial positions). Thus, it is achiral and optically inactive, matching option (d).