Question

Among the complexs, `[N_(CO)_(4)],[NI(CN)_(4)]^(2-)` anhd `[NiCI_(4)]^(2-)`
A. `[Ni(CO)_(4)]` si diamagnetic but `[Ni(CO)_(4)]` and `[NI(CN)_(4)]^(2-)` are paramagentic
B. `[Ni(CN)_(4)]^(2-)` and `[NI(CO)_(4)` aren diamagnetic but `[NiCI_(4))^(2-) is paramagnetic
C. `[Ni(CI_(4)]^(2-)` and `[Ni(CO)_(4)]` are diamgnetic but `[Ni(CN)_(4)]^(2-)` is paramagnetic
D. `[Ni(C)_(4)]^(2-)` and `[Ci(CO)_(4)]^(-2)` are diamagnetic but `[Ni(CO)_(4)]` is paramagnetic

Answer 1

(b) The oxidation state of Ni in `[Ni(CN_(4)]^(2+)` and `[NiCI_(4)]^(2-)` is +2 while in `[Ni(CO)_(4)]` it is in zero oxidation state.
Since CO and `CI^(-)` are strong ligands "thereofe" they cause paring of the unpaired electrons.
`:Therefore" `[Ni(CO)_(4)] and [Ni(CN)_(4)]^(2-)` are diagnetic Whereas, `CI^(-)` is a weak ligand that does not cause pairing of electons , resulting in paramagnetic complex. Hence, `[NiCI_(4)]^(2-)` is paramagnetic.