#[Ni(CO)4]

The hybridization of the central metal ion in [Ni(CO)4] is:

[Ni(CO)4] is tetrahedral (Ni in 0 oxidation state, d10). It uses 4 orbitals from 4s and 4p, forming sp3 hybrid orbitals to bond with 4 CO ligands.

Ref: NCERT Class 12 Chemistry > Chapter 5: Coordination Compounds > Topic: Bonding - Valence Bond Theory and Hybridisation