Electrochemical generation of low-valent molybdenum tri-tertiary phosphine complexes: interactions with monophosphines and molecular nitrogen
Abstract
The electrochemical reduction of the 15-electron molybdenum(III) complex [MoCl3(dpepp)], dpepp = Ph2PCH2CH2P(Ph)CH2CH2PPh2, has been studied in the presence of PPh3 under argon and under molecular nitrogen. The primary reduction of the trichloride involves a reversible single-electron transfer to give the unstable 16-electron molybdenum(II) anion [MoCl3(dpepp)]–. Loss of chloride from this anion prior to or following further electron transfer provides two principal pathways to molybdenum(0) products, [Mo(η6-C6H5PPh2)(dpepp)] under Ar or cis-[Mo(N2)2(dpepp)(PPh3)] under molecular nitrogen, a relatively high potential pathway via molybdenum(I) solvated intermediates and a low potential pathway via trans-[MoCl2(dpepp)(PPh3)]. The cis-dinitrogen complex is unstable on the preparative time-scale, small amounts of trans-[Mo(N2)2(dpepp)(PPh3] are formed, presumably by isomerisation, but the major product is the η6-arene complex.