Question

$\left[NiC{l}_2\right\{P\left(C_2{H}_5{)}_2\right(C_6{H}_5\left){\}}_2\right]$ exhibits temperature dependent magnetic behaviour (paramagnetic/diamagnetic). The coordination geometry of $N{i}^{2+}$ in the paramagnetic and diamagnetic states are respectively:

• A. Tetrahedral in both
• B. Square planar in both
• C. Tetrahedral and square planar
• D. Square planar and tetrahedral

Answer 1

The correct option is C Tetrahedral and square planar

Electronic configuration of:
$Ni:\left[Ar\right]3d^{8}4s^2$
$N{i}^{2+}:\left[Ar\right]3d^{8}4s^0$
Paramagnetic behaviour is possible when pairing does not take place i.e., $3d$ will not participate in bonding and hybridisation will be $s{p}^3$ including $4s$ and $4p$, thus structure is tetrahedral.
Diamagnetic behaviour is possible when pairing takes place. This happens in the presence of strong field ligand.

Therefore, $N{i}^{2+}:\text{paramagnetic},s{p}^3,\text{tetrahedral}N{i}^{2+}:\text{diamagnetic},ds{p}^2,\text{square planar}$