Which of the following complexes is diamagnetic and square planar?

Step-by-step solution

[ CoF ₆ ]³⁻ Co ³⁺[ Ar ] 3 ~d ^6 45^ Sp ^3 ~d ^2 Hybridisation, Octahedral shape [ Co ( NH ₃ )₆ ]³⁺ Co ³⁺[ Ar ] 3 ~d ^6 45^ d ^2 sp ^3 Hybridisation, pairing due to strong field ligand In [ NiCl ₄ ]²⁻ Ni is in +2 oxidation state Ni ⁺²-[ Ar ] 3 ~d ^8 Hybridization involved is sp ^3 as participating orbitals are 4 ~S & 4 P . In [ NiCN ₄ ]²⁻ Ni is in +2 oxidation state. Ni ⁺²-[ Ar ] 3 ~d ^8 CN ⁻ is strong field ligand. It causes pairing of 3 ~d electrons. Hybridization involved is dsp ^2 as participating orbitals are 3