Alkyne insertion into ruthenium–carbon bonds: formation and ring-closing reactions of vinyl complexes

Abstract

Compounds [Ru(CO)₂(C₆H₄X-4)CI(PMe₂Ph)₂][(1a), X = H; (1b), X = Cl; (1c), X = Me; (1d), X = OMe] react with MeO₂CCCCO₂Me to yield vinyl complexes [Ru(CO)₂{C(CO₂Me)C(CO₂Me)(C₆H₄X-4)}Cl(PMe₂Ph)₂](2a)–(2d). The mechanism of formation appears to involve CO substitution by the alkyne, combination of alkyne and aryl ligands, and finally re-entry of CO. Thermal decomposition of (2a)–(2d) yields products [[graphic omitted]H₃X)}(PMe₂Ph)₂](3a)–(3d), complexes (4a)–(4d) whose structure is either [[graphic omitted]O)(C₆H₄X-4))(PMe₂Ph)₂] or [[graphic omitted]O)C(CO₂Me)(C₆H₄X-4)}(PMe₂Ph)₂], alkenes CH(CO₂Me)C(CO₂Me)(C₆H₄X-4)(5a)–(5d), and cis-[Ru(CO)₂Cl₂(PMe₂Ph)₂]. Complex (3a) is also obtained from [Ru(CO)₂(Me)Ph(PMe₂Ph)₂] and MeO₂CCCCO₂Me, while the reaction of [Ru(CO)₂Me₂(PMe₂Ph)₂] with MeO₂CCCCO₂Me yields [Ru(CO)₂{C(CO₂Me)C(CO₂Me)Me}Me(PMe₂Ph)₂](6).