How many of the following complex do not exhibit optical activity but having diamagnetic characters.
(a) $Cis - [Co (en)_{2} (H_{2} O)_{2}]^{3 +}$ (b) $Cis - [Pt (NH_{3})_{2} Cl_{2}]$
(c) Trans- $[Co (en)_{2} (H_{2} O)_{2}]^{3 +}$ (d) $[Ni (CO)_{4}]$

Question

How many of the following complex do not exhibit optical activity but having diamagnetic characters.

(a) $Cis - [Co (en)_{2} (H_{2} O)_{2}]^{3 +}$ (b) $Cis - [Pt (NH_{3})_{2} Cl_{2}]$

(c) Trans- $[Co (en)_{2} (H_{2} O)_{2}]^{3 +}$ (d) $[Ni (CO)_{4}]$

TestHub · Accepted Answer

To exhibit optical activity, a complex must be chiral (non-superimposable on its mirror image). Diamagnetic complexes have all electrons paired.

(a) Cis-[Co(en)₂(H₂O)₂]³⁺: Chiral, so optically active. Co³⁺ (d⁶) is low spin, hence diamagnetic.

(b) Cis-[Pt(NH₃)₂Cl₂]: Square planar, achiral (has a plane of symmetry), so not optically active. Pt²⁺ (d⁸) is diamagnetic.

(c) Trans-[Co(en)₂(H₂O)₂]³⁺: Achiral (has a plane of symmetry), so not optically active. Co³⁺ (d⁶) is low spin, hence diamagnetic.

(d) [Ni(CO)₄]: Tetrahedral, achiral (has S₄ axis), so not optically active. Ni(0) (d¹⁰) is diamagnetic.

Complexes (b), (c), and (d) do not exhibit optical activity and are diamagnetic. Thus, there are 3 such complexes.

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