Question

Using valence bond theory, predict the hybridization and magnetic character of the complex:

[Ni(CO)₄] (Atomic number: Ni = 28)

Using valence bond theory, explain the hybridisation and magnetic character of the following:

[Ni(CO)₄] (At. no.: Ni = 28)

Answer 1

The oxidation state of nickel is 0. In the ground state, nickel has the valence shell electronic configuration 3d⁸ 4s². However, due to the presence of strong field CO ligands, the two 4s electrons are forced to pair up in the 3d orbitals. As a result, all ten electrons occupy the 3d orbitals, leading to the formation of sp³ hybridisation.

Orbitals of Ni:

↑ ↓	↑ ↓	↑ ↓	↑	↑		↑ ↓
3d						4s		4p

sp³ hybridised orbitals of Ni:

↑ ↓	↑ ↓	↑ ↓	↑ ↓	↑ ↓
3d						sp3 hybrid

[Ni(CO)₄] (low spin complex):  

↑ ↓	↑ ↓	↑ ↓	↑ ↓	↑ ↓		XX	XX	XX	XX
3d						sp3 hybrid

Therefore, the complex [Ni(CO)₄] involves sp³ hybridisation and the complex is diamagnetic, as evident from the absence of unpaired electrons.