Electrochemistry of iron and ruthenium flyover bridge complexes

The redox chemistry of dimetallacycloheptadiene (flyover bridge) complexes M2(CO)6[C(R)=C(R’)- COC(R”)=(R”’)] (M = Fe or Ru) has been investigated by electrochemical and spectroscopic techniques. For the Fe2(CO),[ (PhCzPh)2CO] derivative the bulk of the data indicates a sequence of electrochemical events involving the formation of the monoanion and its decomposition to solvated [Fe(C0I3]- and Fe- (CO),[ (PhC2Ph)2CO] fragments, which are able to recombine together on electrochemical or chemical reoxidation giving back the parent complex. Electron paramagnetic resonance features of electroreduced solutions of 13CO-enriched sample of Fe2(CO),[ (PhC2Ph)2CO] and its monophosphine derivative Fez- (CO)5(PPh)3([P hC2Ph)2CO]l end support to the proposed mechanism. The influence of the dienone substituents, R, as well as the effect of the replacement of group V (15) donor ligands for CO on the trend of the electrode potentials is discussed.