Explain `[Co(NH_3)_6]^(3+)` is an inner orbital complex whereas `[Ni(NH_3)_6]^(2+)` is an outer orbital complex.

Explanation

In `[Co(NH_(3))_(6)]^(3+)`, Co is in +3 state with the configuration `3d^(6)`. In the presence of `NH_(3)`, 3d electrons pair up leaving two d-orbital empty. Hence, the hybridisation is `d^(2)sp^(3)` forming an inner orbital complex.
In `[Ni(NH_(3))_(6)]^(2+)`, Ni is in +2 state with the configuration `3d^(8)`. In presence of `NH_(3)`, the 3d electrons do not pair up. The hybridisation involved is `sp^(3)d^(2)` forming an outer orbital complex.