The oxidation state of molybdenum in its oxo complex species Mo2O4C2H42H2O22− is :

[Mo2O4C2H42H2O2]2−:2(O.N. of Mo) +4( O.N. of O)+2O.N. of C2H4+2O.N. of H2O=−22 (O.N. of Mo) +4(−2)+(2×0)+2(0)=−2;O.N. of Mo =(−2+8)/2=+3