Abstract

The reaction of the dichloro(vinylidene)ruthenium compounds [RuCl2(CCHR)L2] (R = Ph or tBu and L = PCy3 or PiPr3) (1a−d) with [H(OEt2)2]BArf (BArf- = [B{C6H3(CF3)2-3,5}4]-) resulted in the attack of the proton at the Cβ carbon atom of the vinylidene ligand and afforded the corresponding cationic, five-coordinate carbyneruthenium complexes [RuCl2(⋮CCH2R)L2]BArf (2a−d) in almost quantitative yields. The protonation of the carboxylato derivatives [RuCl(κ2-O2CR)(CCHPh)(PiPr3)2] [R = H (3a), CH3 (3b), or Ph (3f)] with [H(OEt2)2]BArf led to the formation of the five-coordinate cyclic carbene complexes [RuCl{C(CH2Ph)OC(O)R}(PiPr3)2]BArf [R = H (6a), CH3 (6b), or Ph (6f)], which are formed via nucleophilic attack of the carboxylato ligand to a cationic carbyneruthenium intermediate. The protonation of the related vinylidene compounds [RuCl(κ2-O2CR)(CCHPh)(PiPr3)2] [R = CH2F (3c), CHF2 (3d), CF3 (3e), C6H4NO2-4 (3g), C6H4NO2-2 (3h), C6F5 (3i), and C6H3(NO2)2-2,4 (3j)] with [H(OEt2)2]BArf gave an equilibrium mixture of the carbyne [RuCl(κ2-O2CR)(⋮CCH2Ph)(PiPr3)2]BArf (5c−e, 5g−j) and the isomeric, cyclic carbene complexes [RuCl{C(CH2Ph)OC(O)R}(PiPr3)2]BArf (6c−e, 6g−j). The position of this equilibrium significantly depends on the basicity of the carboxylato ligand. The six-coordinate cyclic carbene complexes [Ru(κ2-O2CR1){C(CH2Ph)OC(O)R2}(PiPr3)2]BArf [R1 = R2 = CHF2 (7a), CF3 (7b); R1 = CF3, R2 = H (7c)] were obtained on protonation of the precursors [Ru(κ1-O2CR1)(κ2-O2CR2)(CCHPh)(PiPr3)2] (4a−c) with [H(OEt2)2]BArf. Both 7a and 7b undergo a fluxional process in solution resulting in a κ1/κ2 interconversion of the carboxylato groups. The crystal and molecular structures of 2b, 5e, and 6a were determined by X-ray crystallography.

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