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 vinylidene 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)(PPh 3)2 (8). X-Ray crystal structures of complexes (1), (4), (5) and (8) are reported. © CSIRO 2000.