The Sensitive Balance between Five-Coordinate Carbene and Six-Coordinate Carbyne Ruthenium Complexes Formed from Ruthenium Vinylidene Precursors

摘要

The reaction of the dichloro(vinylidene)ruthenium compounds {RuCl_2(=C=CHR)L_2] (R = Ph or tBu and L = PCy_3 or PiPr_3) (1a-d) with [H(OEt_2)_2]BAr_f (BAr_f~- = [B{C_6H_3(CF_3)_2-3,5}_4]~-) resulted in the attack of the proton at the C_#beta# carbon atom of the vinylidene ligand and afforded the corresponding cationic, five-coordinate carbyneruthenium complexes [RuCl_2-(ident to CCH_2R)L_2]BAr_f (2a-d) in almost quantitative yields. The protonation of the carboxylato derivatives [RuCl(k~2-O_2CR)(=C=CHPh)(PiPr_3)_2] [R = H (3a), CH_3 (3b), or Ph (3f)] with [H(OEt_2)_2]BAr_f led to the formation of the five-coordinate cyclic carbene complexes [RuCl-{=C(CH_2Ph)OC(O)R}(PiPr_3)_2]BAr_f [R = H (6a), CH_3 (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(k~2-O_2CR)(=C=CHPh)(PiPr_3)_2][R = CH_2F (3c), CHF_2 (3d), CF_3 (3e), C_6H_4NO_2-4 (3g), C_6H_4NO_2-2 (3h), C_6F_5 (3i), and C_6H_3-(NO_2)_2-2,4 (3j)] with [H(OEt_2)_2]BAr_f gave an equilibrium mixture of the carbyne [RuCl-(k~2-O_2CR)(ident to CCH_2Ph)(PiPr_3)_2]BAr_f (5c-e, 5g-j) and the isomeric, cyclic carbene complexes [RuCl{=C(CH_2Ph)OC(O)R}(PiPr_3)_2]BAr_f (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(k~2-O_2CR~1){=C(CH_2Ph)OC(O)R~2}(PiPr_3)_2BAr_f[R~1 = R`2 = CHF_2 (7a), CF_3 (7b); R~1 = CF_3, R~2 = H (7c)] were obtained on protonation of the precursors [Ru(k~1-O_2CR~1)(k~2-O_2CR~2)(=C=CHPh)(PiPr_3)_2] (4a-c) with [H(OEt_2)_2]BAr_f. Both 7a and 7b undergo a fluxional process in solution resulting in a k~1/k~2 interconversion of the carboxylato groups. The crystal and molecular structures of 2b, 5e, and 6a were determined by X-dray crystallography.