Coordination Compounds 2 Question 31
####33. $NiCl _2{P\left(C _2 H _5\right) _2\left(C _6 H _5\right) } _2$ exhibits temperature dependent magnetic behaviour (paramagnetic/diamagnetic) the coordination geometries of $Ni^{2+}$ in the paramagnetic and diamagnetic states respectively, are
(2012)
(a) tetrahedral and tetrahedral
(b) square planar and square planar
(c) tetrahedral and square planar
(d) square planar and tetrahedral
Coordination Compounds 245
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Answer:
Correct Answer: 33. $A$
Solution:
- In the given complex, $NiCl _2{P\left(C _2 H _5\right) _2\left(C _6 H _5\right) } _2$ nickel is in +2 oxidation state and the ground state electronic configuration of $Ni^{2+}$ ions in free gaseous state is
For the given four coordinated complex to be paramagnetic, it must possess unpaired electrons in the valence shell. To satisfy this condition, four lone pairs from the four ligands occupies the four $s p^{3}$-hybrid orbitals as :
Therefore, geometry of paramagnetic complex must be tetrahedral. On the otherhand, for complex to be diamagnetic, there should not be any unpaired electrons in the valence shell.
This condition can be fulfilled by pairing electrons of $3 d$-orbitals against Hund’s rule as
The above electronic arrangement gives $d s p^{2}$-hybridisation and therefore, square planar geometry to the complex.
