Coordination number of Cr is six. A complex with C2O42−, en and superoxide O2Θ will be in the ratio to make complex Cr⁡C2O4x,(en)yO2zΘ

Cr3+,C2O42−,(en)0,O2ΘC2O42− and (en)0 are bidentate ligand. CN of Cr3+=6,  So, x=1,y=1,z=2CN=x×2+y×2+2z=6=1×2+1×2+2×1=6Sum of charges = Net charges+3+(−2x)+0(y)+(−1×z)=−1(x=1,y=1,z=2)∴+3−2+9−1×2=−1Sum of charges = -1, Net charges = - 1