JEE Main · 2024 · 09 Apr 2024 · Shift 2 · Coordination Compounds

(A) ${\text{K}}_2[{\text{Ni(CN)}}_4]$: CN${}^{-}$ is a strong-field ligand, pairing $d$-electrons of Ni${}^{2+}$ ($d^8$) to leave one empty $d$-orbital — hybridisation $ds{p}^2$ — matches III.

(B) $[{\text{Ni(CO)}}_4]$: Ni(0) ($3d^{8}4s^2$) with CO as a strong-field ligand causing $4s$-electrons to pair into $3d$, leaving the $4s$ and $4p$ orbitals for bonding — hybridisation $s{p}^3$ — matches I.

(C) $[{\text{Co(NH}}_3{)}_6]{\text{Cl}}_3$: Co${}^{3+}$ ($3d^6$) with NH${}_3$ as a strong-field ligand, inner-orbital complex — hybridisation $d^{2}s{p}^3$ — matches IV.

(D) ${\text{Na}}_3[{\text{CoF}}_6]$: Co${}^{3+}$ with F${}^{-}$ as a weak-field ligand, outer-orbital complex — hybridisation $s{p}^3{d}^2$ — matches II.

Matching: A–III, B–I, C–IV, D–II.