Explain [Co(NH₃)₆]³⁺ is an inner orbital complex whereas [Ni(NH₃)₆]²⁺ is an outer orbital complex.

[Co(NH₃)₆]³⁺

[Ni(NH₃)₆]²⁺

Oxidation state of cobalt:

Overall charge balance:

X + 6(0) = 3

X = + 3

Oxidation state of nickel:

Overall charge balance:

X + 6(0) = 2

X = + 2

Outer electronic configuration of cobalt = d⁶

Outer electronic configuration of nickel = d⁸

NH₃ is a strong field ligand so it causes pairing of electron. Therefore cobalt undergoes d²sp³ hybridisation. As in the hybridisation d² orbitals are used from the (n-1)d orbitals(inner orbitals as n = 4 being quantum number) . hence it is a inner orbital complex.

NH₃ is a strong field ligand so it causes pairing of electron. Therefore nickel undergoes sp³ d² hybridisation. As in the hybridisation d² orbitals are used from the nd orbitals (outer orbitals as n = 4 being quantum number) . hence it is a outer orbital complex.