Which one of the following is an inner orbital complex as well as diamagnetic in nature?

Options

A. (a) `[Cr(NH_3)_6]^(3+)`
B. (b) `[Co(NH_3)_6]^(3+)`
C. (c) `[Ni(NH_3)_6]^(2+)`
D. (d) `[Zn(NH_3)_6]^(2+)`

Answer

B

Explanation

In `[Zn(NH_3)_6]^(3+)`, `Zn` exists as `Zn^(2+) ._(30)Zn: 3d^(10), 4s^2`
`Zn^(2+): 3d^(10)`. Thus, no unpaired electron but it is outer orbital complex.
In `[Co(NH_3)_6]^(3+)`, Co exists as `Co^(3+)`
`._(27)Co:3d^7, 4s^2`
`Co^(3+): 3d^(6)`, It is `d^2 sp^3` inner orbital complex with no unpaired `e^(-)` in `3d` due to forced pairing.