An electrochemical study, complimented by a density functional theory study, on nine Mo(O) Fischer carbene complexes of the formula [(CO)(2)(L,11)Mo=C(Y)(2-fury1)] with Y= OEt, NH2 or NHCy; L,L' = CO,CO; PPh3,CO or dppe (diphenyl phosphinoethane), showed that the Mo-based oxidation process can be systematically tuned by the substitution of the CO groups: (most difficult to oxidize, largest oxidation potential Epa) [(CO)(5)Mo-carbene complex] > [(CO)(4)(PPh3)Mo-carbene complex] > [(C0)3(dppe)Mo-carbene complex]. The one-electron reduction of the complexes that is mainly localized on the carbene carbon, followed the same trend. (C) 2015 Elsevier Ltd. All rights reserved.