What is coordination of the metal in $\left[\mathrm{Co}(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right]?$

The coordination is the number of bonds which are connected between the metal and ligand. The chlorine ligand is a mono dentate ligand and the ethylenediamine is a bidentate ligand. So, two ethylenediamine formed the four bonds and the two chlorine ligand formed the two bonds. Hence, the coordination of the metal in $\left[\mathrm{Co}(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right]$ is $6$.