Synthesis and Reactivities of Cationic Diruthenium Complexes with Terminal Vinylidene Ligands. Hydration and Novel Cyclization of Acetylenes on the Diruthenium Center

Abstract

The cationic diruthenium complexes with a terminal vinylidene ligand [Cp*RuCl(μ2-SPri)2Ru(CCHR)Cp*][OTf] (3a, R = COOMe; 3b, R = COMe; 3c, R = H; Cp* = η5-C5Me5, OTf = OSO2CF3) were obtained in high yields by the reaction of [Cp*RuCl(μ2-SPri)2Ru(OH2)Cp*][OTf] with HC⋮CR. Hydration of 3a and 3b gave the carbonyl complex [Cp*RuCl(μ2-SPri)2Ru(CO)Cp*][OTf] and CH3R in almost quantitative yields, while the reaction of 3c with water gave the μ2-acetyl complex [Cp*RuCl(μ2-SPri)2{μ2-C(O)Me}RuCp*][OTf] (5). A reaction mechanism for the former reactions is proposed, which includes hydration of the vinylidene ligands to form the μ2-β-ketoacetyl complexes with a six-membered dimetallacyclic structure [Cp*Ru(μ2-SPri)2(η1:η1-μ2-COCH2COR‘)RuCp*]+ (R‘ = OMe, Me) and the following decarbonylation reaction of the μ2-COCH2COR‘ ligand on the bimetallic center to produce the carbonyl complex and CH3COR‘ via the enolato−carbonyl complexes [Cp*Ru(CO)(μ2-SPri)2Ru(OCR‘CH2)Cp*]+. In accordance with this mechanism, the reaction of 3a with MeOH afforded [Cp*Ru(μ2-SPri)2{η1:η1-μ2-C(OMe)CHCOOMe}RuCp*][OTf] (7). Complexes 3a and 3b reacted with p-tolylacetylene to form the dinuclear metallacyclic complexes 9a and 9b [Cp*Ru(μ2-SPri)2{η1:η1-μ2-C(Tol)CCCHC(R‘)O}RuCp*][OTf] (9a, R‘ = OMe; 9b, R‘ = Me), respectively. The structures of 3b, 5, 7, and 9a have been determined by X-ray crystallography.