Coordination number of central atom in  $\left[\mathrm{Pt}{\left(\mathrm{en}\right)}_2{\left({\mathrm{H}}_2\mathrm{O}\right)}_2\right]{\mathrm{Cl}}_4$ Complex is 

2H₂O and 2 en (bidentate ligand) ligands are directly donate the electron pair towards central metal atom Co, so coordination number of  $\left[\mathrm{Pt}{\left(\mathrm{en}\right)}_2{\left({\mathrm{H}}_2\mathrm{O}\right)}_2\right]{\mathrm{Cl}}_4$ Complex is 6