Chemistry - Coordination Chemistry Question with Solution | TestHub

Concept: Spin-paired complex: pairing of $e^{-}$ takes place.

(A) $[\mathrm{Co}({\mathrm{NH}}_3{)}_6{]}^{3+}$: ${\mathrm{Co}}^{3+}$ is $3{\mathrm{d}}^6$. ${\mathrm{NH}}_3$ is a strong field ligand (SFL) for ${\mathrm{Co}}^{3+}$.

The electronic configuration is ${\mathrm{t}}_{2\mathrm{g}}^{222}{\mathrm{e}}_{\mathrm{g}}^{00}$ (spin-paired complex).

(B) $[{\mathrm{CoF}}_6{]}^{3-}$: ${\mathrm{Co}}^{3+}$ is $3{\mathrm{d}}^6$. ${\mathrm{F}}^{-}$ is a weak field ligand (WFL).

The electronic configuration is ${\mathrm{t}}_{2\mathrm{g}}^{211}{\mathrm{e}}_{\mathrm{g}}^{11}$. Hybridization is ${\mathrm{sp}}^3{\mathrm{d}}^2$ (high spin complex).

(C) $[{\mathrm{NiCl}}_4{]}^{2-}$: ${\mathrm{Ni}}^{2+}$ is $3{\mathrm{d}}^8$. ${\mathrm{Cl}}^{-}$ is a weak field ligand (WFL), forming a tetrahedral complex.