A reinvestigation of compound CpMo(PMe3)2(CH3)2: alkylation by single electron transfer and radical addition?

Abstract

The synthesis of the half-sandwich molybdenum(III) diphosphine dimethyl complex CpMo(PMe₃)₂(CH₃)₂ has been reinvestigated. The compound was obtained from the corresponding dichloro complex CpMo(PMe₃)₂Cl₂ and methyllithium at low temperatures and isolated as a crystalline product by conducting all operations at temperatures lower than −10 °C. The complex is thermally unstable at room temperature but has been fully characterised by EPR spectroscopy, cyclic voltammetry and X-ray diffraction. The formation reaction is retarded by excess phosphine. On the basis of this and other related observations, a mechanism involving phosphine pre-dissociation followed by single electron transfer and radical addition is proposed.