The total possible co-ordination isomers for the following compounds respectively are :

$\left[\mathrm{Co}(\mathrm{en}{)}_3\right]\left[\mathrm{Cr}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]$

$\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_4\right]\left[{\mathrm{CuCl}}_4\right]$

$\left[\mathrm{Ni}(\mathrm{en}{)}_3\right]\left[\mathrm{Co}{\left({\mathrm{NO}}_2\right)}_6\right]$

Coordination isomers has two or more coordination compounds where composition within the coordination sphere is not same.

Coordination isomers in the complexes:

$\left[\mathrm{Co}(\mathrm{en}{)}_3\right]\left[\mathrm{Cr}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]\to 4$

$\left[\mathrm{Cu}{\left({\mathrm{NH}}_3\right)}_4\right]\left[{\mathrm{CuCl}}_4\right]\to 2$

$\left[\mathrm{Ni}(\mathrm{en}{)}_3\right]\left[\mathrm{Co}{\left({\mathrm{NO}}_2\right)}_6\right]\to 4$