Arrange the following cobalt complexes in the order of increasing crystal field stabilisation energy (CFSE) value.

Complexes $\underset{\left(\mathrm{A}\right)}{{\left[{\mathrm{CoF}}_6\right]}^{3-}}, \underset{\left(\mathrm{B}\right)}{{\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}}, \underset{\left(\mathrm{C}\right)}{{\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}} \mathrm{and} \underset{\left(\mathrm{D}\right)}{{\left[\mathrm{Co}{\left(\mathrm{en}\right)}_3\right]}^{3+}}$

Choose the correct option.

For the same central metal ion, the CFSE increases with increase in strength of the ligand. The order of strength of ligand is given by the spectrochemical series :

$\begin{array}{l}{\mathrm{I}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{SCN}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{S}}^{2-}<{\mathrm{F}}^{-}<{\mathrm{OH}}^{-}\\ <{\mathrm{C}}_2{\mathrm{O}}_4^{2-}<{\mathrm{H}}_2\mathrm{O}<{\mathrm{NCS}}^{-}<{\mathrm{EDTA}}^{4-}<{\mathrm{NH}}_3<\text{ en }<{\mathrm{CN}}^{-}<\mathrm{CO}\end{array}$

Thus, the order of CFSE of given complexes will be :

$\underset{\left(\mathrm{A}\right)}{{\left[{\mathrm{CoF}}_6\right]}^{3-}} < \underset{\left(\mathrm{B}\right)}{{\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}} < \underset{\left(\mathrm{C}\right)}{{\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}} < \underset{\left(\mathrm{D}\right)}{{\left[\mathrm{Co}{\left(\mathrm{en}\right)}_3\right]}^{3+}}$.