Some Pentamethylcyclopentadienyl-Ruthenium Derivatives of Methyl Propiolate

Abstract

The reaction between methyl propiolate and RuCl(PPh₃)₂Cp* and NH₄PF₆ in EtOH gives cationic vinylidene [Ru{=C=CH(CO₂Me)}(PPh₃)₂Cp*] [PF₆] (1), which is deprotonated to Ru(C_CCO2Me)(PPh3)2Cp* by NaOMe. The alkynyl complex reacts with PhCH2Br to give [Ru{=C=C(CH2Ph)(CO₂Me)}(PPh₃)₂Cp*] + , isolated as its bromide and PF₆ – salts. In contrast, reactions between methyl propiolate and RuCl(PPh₃)₂Cp* in benzene afford neutral vinyl-idene RuCl{=C=CH(CO₂Me)}(PPh₃)Cp* (4) and metallacycle RuCl{CH=C(CO₂Me)CH=C(CO₂Me)}(PPh₃)Cp* (5). The former complex is dehydrochlorinated by NaOMe in the presence of MeCN or P(OMe)₃ to give Ru(C_CCO₂Me)(L)(PPh₃)Cp* [L = MeCN and P(OMe)₃, respectively]. A minor product (2%), obtained from treatment of (5) with NaOMe, is Ru{CH=C(CO₂Me)CH=C(CO₂Me)C=CHC(O)OMe}(CO)(PPh₃)₂ (8). X-Ray crystal structures of complexes (1), (4), (5) and (8) are reported.