Question

Explain how the two complexes of nickel, [Ni(CN)₄]^2- and [Ni(CO)₄] have different structures but have the same magnetic behaviour.

Answer 1

In [Ni (CN)₄]^2- Ni exist in Ni²⁺ state, i.e.
Ni²⁺ → [Ar] 3d and CN^– is a strong field ligand, so it causes pairing

In [Ni(CO)₄], Ni exist in Ni(o) state and electrons of 4s gets paired up in 3d orbital due to strong field ligand-CO.

As discussed above, geometry is different in both the cases but none of these have impaired electrons, hence both are diamagnetic.