Irradiation (λ > 380 nm) of CpW(CO)3Me in inert solvents in the presence of PPh3 gives [PPh3CH3 +][CpW(CO)3 -] as well as the substitution product CpW(CO)2(PPh3)Me (φdisappearance CpW(CO)3Me = 0-45 ± 0.005, φappearance CpW(CO)3- = 0.04 ± 0.01). The mechanism of CpW(CO)3 - formation was studied. Experiments suggest that CpW(CO)2(PPh3)Me may be an intermediate in the reaction but direct reductive elimination of PPh3Me+ from this species or from CpW(CO)(PPh3)2Me was ruled out. Experiments using PTol3 demonstrated that PAr3Me+ (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 -. 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.
|Number of pages||6|
|Journal||Journal of the American Chemical Society|
|Publication status||Published - 1986|
ASJC Scopus subject areas