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

Explanation

In the presence of `NH_(3)`, the 3d electrons pair up leaving two d orbitals
empty to be involved in `d^(2)sp^(3)` hybridisation forming inner orbital complex
in case of `[Co(NH_(3))_(6)]^(3+)`. In `Ni(NH_(3))_(6)
^(2+)`, Ni is in +2 oxidation state and has `d^(8)` configuration,
the hybridisation involved is `sp^(3)d^(2)` forming outer orbital complex.