Preparation, structure, and reactions of alkenyl complexes of ruthenium(II)

Complexes trans-[Ru(CO)2Cl2L2](L = PMe2Ph or AsMe2Ph) react with alkynes RO2CCCCO2R (R = Me or Et) to yield alkenyl complexes [Ru(CO)2{C(CO2R)C(CO2R)Cl}ClL2]. From the structure of [Ru(CO)2{C(CO2Me)C(CO2Me)Cl}Cl(PMe2Ph)2], as determined by X-ray diffraction, and from kinetic evidence, it would appear that alkyne complexes [Ru(CO)(RO2CCCCO2R)Cl2L2] are formed initially, and that the alkyne then undergoes intramolecular nucleophilic attack by a chloride ligand. Unlike the methyl and σ-allyl complexes [Ru(CO)2R(Cl)(PMe2Ph)2], which react with PMe2Ph to form acyl complexes [Ru(CO)(COR)Cl(PMe2Ph)3](R = Me or C3H5), the complex [Ru(CO)2{C(CO2Me)C(CO2Me)Cl}Cl(PMe2Ph)2] undergoes carbonyl substitution to yield [Ru(CO){C(CO2Me)C(CO2Me)Cl}Cl(PMe2Ph)3]. Neither [Ru(CO)2{C(CO2Me)C(CO2Me)Cl}Cl(PMe2Ph)2] nor the corresponding complex containing a weakly bound ClO4 ligand in place of chloride reacts with further molecules of alkyne.