Photochemical Reduction of CpW(CO)3CH3 (Cp = η5-C5H5) to CpW(CO)3(1-); An Isolobal Analogy to the Disproportionation of Cp2Mo2(CO)6

Article abstract of DOI:10.1021/ja00261a015

Irradiation (λ > 380 nm) of CpW(CO)3Me in inert solvents in the presence of PPh3 gives as well as the substitution product CpW(CO)2(PPh3)Me (Φ _{disappearance CpW(CO)3Me} = 0.45 +/- 0.005, Φ _{apparance CpW(CO)3(1-)} = 0.04 +/- 0.01).The mechanism of CpW(CO)3(1-) formation was studied.Experiments suggest that CpW(CO)2(PPh3)Me may be an intermediate in the reaction but direct reductive elimination of PPh3Me(1+) from this species or from CpW(CO)(PPh3)2Me was ruled out.Experiments using PTol3 demonstrated that PAr3Me(1+) (Ar = aryl) is formed from exogenous, not coordinated, phosphine.The mechanism proposed for the reduction of CpW(CO)3Me involves the intermediate formation of phosphoranyl radicals, ^.PPh3Me, formed by addition of Me radicals (from W-CH3 homolysis) to PPh3.Phosphoranyl reduction of a variety of metal species which are present in solution is shown to lead to CpW(CO)3(1-).The proposed mechanism is isolobal with a mechanism we proposed for the photochemical disproportionation of metal-metal bonded dimers (e.g., Cp2Mo2(CO)6) involving 19-valence-electron intermediates.