Valence bond theory

$\ce{NiCl2\{P(C2H5)2(C6H5)\}2}$ exhibits temperature dependent magnetic behaviour (paramagnetic / diamagnetic). The coordination geometries of $\ce{Ni^{2+}}$ in the paramagnetic and diamagnetic states are respectively

Geometrical shapes of the complexes formed by the reaction of $\ce{Ni^{2+}}$ with $\ce{Cl-}$, $\ce{CN-}$ and $\ce{H2O}$, respectively, are

Both $\ce{[Ni(CO)4]}$ and $\ce{[Ni(CN)4]^{2-}}$ are diamagnetic. The hybridisations of nickel in these complexes, respectively, are