One-Electron Reduction of Molybdenum η²(4e)-Alkyne Complexes as a Pathway to the η²(3e) Vinyl Ligand

Abstract

Reaction of the molybdenum alkyne complex [Mo(P{OMe}3)2(η2{4e}-PhC2Ph)(η5-C5H5)][BF4] with K[Fe(CO)2(η5-C5H5)] results in the formation of the η2(3e)-vinyl complex and [Fe(CO)2(η5-C5H5)]2. A study of the reaction by EPR spectroscopy implies that the reaction proceeds via [Mo(P{OMe}3)2(η2{4e}-PhC2Ph)(η5-C5H5)], which is then thought to undergo a hydrogen-abstraction reaction to give the observed product. The same radical was observed in the reaction of [Mo(P{OMe}3)2(η2{4e}-PhC2Ph)(η5-C5H5)][BF4] with LiBEt3H, implying the presence of an alternative mechanistic pathway to the direct addition of hydride to the molybdenum alkyne complex.