Which one of the following is an outer orbital complex and exhibits paramagnetic behaviour ?

Options

A. `[Ni(NH_(3))_(6)]^(2+)`
B. `[Zn(NH_(3))_(6)]^(2+)`
C. `[Cr(NH_(3)))_(6)]^(3+)`
D. `[Co(NH_(3))_(6)]^(3+)`

Answer

A

Explanation

Outer orbital complex utilises outer D-orbitals for bonding and exhibit paramagnetic behaviour , only if unpaired electrons are.
(a) `In [Ni(NH_(3))_(6)]^(2+)Ni^(2+)=[Ar] 3d^(8) 4s^(0) `

So this is an outer orbital complex having paramagnetic character .
(b) `[Zn(NH_(3))_(6)]^(2+), sp^(3) d^(2) ` hybridisation , outer orbital complex and diamagnetic .
(C ) `[Cr(NH_(3))_(6)]^(3+),d^(2)sp^(3)` hybridisation , inner orbital complex and paramagnetic .
(d) `[Co(NH_(3))_(6)]^(3+),d^(2)sp^(3) ` hybridisation ,inner orbital complex and diamagnetic .