Reductive elimination of ketones from ruthenium(II) complexes

Abstract

Complexes [Ru(CO)₂R₂(PMe₂Ph)₂](R = aryl or alkyl) decompose at room temperature in CHCl₃ or Me₂CO solution to yield the ketones R₂CO. Decomposition is intramolecular, since the complexes [Ru(CO)₂RR′(PMe₂Ph)₂] yield only the unsymmetrical ketones RR′CO, and the disappearance of [Ru(CO)₂(C₆H₄Me-4)₂(PMe₂Ph)₂] follows simple first-order kinetics. The acyl complex [Ru(CO)(CNCMe₃)(COC₆H₄Me-4)(C₆H₄Me-4)(PMe₂Ph)₂] also decomposes in CHCl₃ solution to give (4-MeC₆H₄)₂CO, but the decomposition is inhibited by free Me₃CNC. It is believed that the ketones are formed by reductive elimination from [Ru(CO)(COR)R(PMe₂Ph)₂]. A ruthenium(0) product could not be isolated, but the ruthenium(II) complex [[graphic omitted]C₆H₄Me}(PMe₂Ph)₂] was obtained when the decomposition of [Ru(CO)₂(C₆H₄Me-4)₂(PMe₂Ph)₂] in CHCl₃ was carried out at higher temperatures.