b
\({\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}}\)

\(\mathrm{Co}^{3+}(\text { strong field ligand }) \Rightarrow 3 \mathrm{~d}^6\left(\mathrm{t}_{2 \mathrm{~g}}^6, \mathrm{e}_{\mathrm{g}}^0\right),\)

Hybridisation : \(d^2 \mathrm{sp}^3\)

Inner obital complex(spin paired complex)

Pairing will take place.

\(\left[\mathrm{CoF}_6\right]^{3-}\)

\(\mathrm{Co}^{3+}\) (weak field ligand) \(\Rightarrow 3 \mathrm{~d}^6\left(\mathrm{t}_{2 \mathrm{~g}}^4, \mathrm{e}_{\mathrm{g}}^2\right)\)

Hybridisation : \(\mathrm{sp}^3 \mathrm{~d}^2\)

Outer orbital complex (spin free complex) no pairing will take place