question_answer

\[[NiC{{l}_{2}}{{\{P{{({{C}_{2}}{{H}_{5}})}_{2}}({{C}_{6}}{{H}_{5}})\}}_{2}}]\] exhibits temperature dependent magnetic behaviour (paramagnetic/ diamagnetic). The coordination geometries of \[N{{i}^{2+}}\] in the paramagnetic and diamagnetic states are respectively 

A) tetrahedral and tetrahedral

B) square planar and square planar

C) tetrahedral and square planar

D) square planar and tetrahedral

Correct Answer: C

Solution :

[c] In both states (paramagnetic and diamagnetic) of the given complex, Ni exists as \[N{{i}^{2+}}\] whose electronic configuration is \[[Ar]3{{d}^{8}}4{{s}^{0}}\]. In the above paramagnetic state, geometry of the complex is \[s{{p}^{3}}\] giving tetrahedral geometry. The diamagnetic state is achieved by pairing of electrons in 3d orbital. Thus the geometry of the complex will be \[ds{{p}^{2}}\] giving square planar geometry.