Question

Describe the bonding in the tetrahedral complex Ni(CO)₄ on the basis of valence bond theory. Give the orbital diagrams of metal atoms in free state and in the complex. Mention the number of unpaired electrons in the complex.

Answer 1

Ni (CO)₄ (tetrahedral), oxidation state of Ni is zero.

Electron configuration of Ni: [Ar]3d⁸4s² 

Orbital diagram of free metal atom:

The complex is tetrahedral. Ni must be sp³ hybridized. Therefore, in the presence of ligands, 3d electrons are forced to pair up and two 4s electrons are transferred to vacant d-orbital. One 4s and three 4p orbitals hybridize to form four sp³ vacant hybrid orbitals which overlap with filled orbitals of ligands to form coordinate bonds.

∴ number of unpaired electrons  =  0.