Question

Explain the type hybridisation, magnetic property and geometry for ${\left[Ni{\left(CN\right)}_4\right]}^{2-}$ and ${\left[Ni{\left({NH}_3\right)}_4\right]}^{2+}$ using VB theory.

Answer 1

(1) Number of unpaired electrons$=2$
$\therefore {\mu }_s=2\sqrt{2(2+2)}=2.83BM$
Since the hybridisation is ${sp}^3$, the geometry of the molecule is tetrahedral.
(2) Another possible geometry for the 4 coordinated complex is the square planar configuration involving $d{sp}^2$ hybridisation.
The ligand ${CN}^{-}$ is a powerful ligand. Hence if forces the unpaired electrons to pair up in $d$ orbitals. Hence this complex ion does not contain unpaired electrons. It is diamagnetic.
The geometry of the molecule is square planar.