Question -
Answer -
Thoughboth [NiCl4]2− and [Ni(CO)4]are tetrahedral, their magnetic characters are different. This is due to adifference in the nature of ligands. Cl− is a weak fieldligand and it does not cause the pairing of unpaired 3d electrons.Hence, [NiCl4]2− is paramagnetic.
InNi(CO)4, Ni is in the zero oxidation state i.e., ithas a configuration of 3d8 4s2.
ButCO is a strong field ligand. Therefore, it causes the pairing of unpaired 3d electrons.Also, it causes the 4s electrons to shift to the 3d orbital, thereby givingrise to sp3 hybridization.Since no unpaired electrons are present in this case, [Ni(CO)4]is diamagnetic.