The coordination number of `Ni^(2+)` is 4
`NiCI_(2) + KCN` (excess)rarr`A` (cyano complex)
Predict the magnetic nature of `A` and `B` .

Options

A. Both are diamagnetic .
B. `A` is diamagnetic and `B` is paramagnetic with one unpaired electron .
C. A is diamagnetic and `B` is paramagnetic with two unpaired electrons .
D. Both are paramagnetic .

Answer

b

Explanation

(i) `[Ni(CN)_(4)]_(2),Ni(Z =28)implies 3d^(8) 4s^(2)`
`Ni^(2+) =3d^(8)`
Cyano is a strong fileld ligand, it causes pairing `dsp^(2)` hybridisation (square planar) There are no unpaired electrons, so the complex is diamagnetic. Spin magnetic moment `=zero`
(ii) `[NiCI_(4)]^(2)`
`Ni^(2+) = [Ar]3d^(8)`
Chlorido is a weak field ligand no pairing `sp^(3)` hybridisation (tetrahedral) Threr are two unpaired electrons, so the complex paramagnetic Spin magnetic moment
`mu =sqrt( n (n +2)) BM = sqrt(2(2 + 2)) BM =sqrt8 BM`