The sum of coordination number and oxidation number of the metal M in the complex  $\left[M(en{)}_2\left({\mathrm{C}}_2{\mathrm{O}}_4\right)\right]\mathrm{Cl}$ (where en is ethylenediamine) is

$\left[\mathrm{M}(\mathrm{en}{)}_2\left({\mathrm{C}}_2{\mathrm{O}}_4\right)\right]\mathrm{Cl}:$

en…neutral, bidentate

oxolato…bivalent,negative,bidentate

Oxidation number of metal = +3

Coordination number of metal = 6

$\therefore$Sum of oxidation number and coordination number = 3 + 6 = 9