question_answer

Amongst \[Ni{{\left( CO \right)}_{4}},\] \[{{\left[ Ni{{(CN)}_{4}} \right]}^{2-}}\] and \[{{[NiC{{l}_{4}}]}^{2-}}\] [IIT 1991]

A) \[Ni{{\left( CO \right)}_{4}}\] and \[{{\left[ NiC{{l}_{4}} \right]}^{2-}}\]are  diamagnetic  and \[{{[Ni{{(CN)}_{4}}]}^{2-}}\] is paramagnetic

B) \[{{\left[ NiC{{l}_{4}} \right]}^{2-}}\] and \[{{\left[ Ni{{\left( CN \right)}_{4}} \right]}^{2-}}\] are diamagnetic and \[Ni{{\left( CO \right)}_{4}}\] is paramagnetic

C) \[Ni{{\left( CO \right)}_{4}}\] and \[{{\left[ Ni{{\left( CN \right)}_{4}} \right]}^{2-}}\] are diamagnetic and \[{{\left[ NiC{{l}_{4}} \right]}^{2-}}\] is paramagnetic

D) \[Ni{{\left( CO \right)}_{4}}\] is diamagnetic and \[{{\left[ NiC{{l}_{4}} \right]}^{2-}}\] and \[{{\left[ Ni{{\left( CN \right)}_{4}} \right]}^{2-}}\] are paramagnetic

Correct Answer: C

Solution :

  The electronic configuration of Ni in \[{{[Ni{{(CN)}_{4}}]}^{2-}},\,{{[Ni(C{{l}_{4}})]}^{2-}}\] and \[Ni{{(CO)}_{4}}\] are as following      \[N{{i}^{+}}\]in\[{{[Ni{{(CN)}_{4}}]}^{2-}}\]-         \[N{{i}^{2+}}\]in\[{{[Ni(C{{l}_{4}})]}^{2-}}\]-     \[Ni\] in \[[Ni{{(CO)}_{4}}]\] - CO and \[C{{N}^{-}}\] are strong ligands so they induces pairing of electrons so their complexes are diamagnetic while \[C{{l}^{-}}\] is a weak ligand so it does not induce the pairing of electrons so its complex is paramagnetic.