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

Abstract

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.