Oligomerisation of alkynes at a pentamethylcyclopentadienylruthenium centre

Abstract

Reactions between the neutral vinylidene RuCl(CCHPh)(PPh₃)Cp* 2 and AgCCCO₂Me gave Ru{η¹-C(CCPh) CHC(O)OMe-O}(PPh₃)Cp* 3, while either LiCCPh or HCCPh/NaOMe afforded the known Ru{η³-PhCHCHC CPh(CCPh)}(PPh₃)Cp* 1. Similarly, RuCl{CCH(CO₂Me)}(PPh₃)Cp* 4 reacted with HCCPh/NaOMe to give Ru{η³-CH(CO₂Me)CHCCPh(CCCO₂Me)}(PPh₃)Cp* 5. Complex 3 reacted with HCCCO₂R (R = Me or Et) to give the 1,3,4,5-tetraen-1-yls Ru{η¹,η²-C(CO₂R)CHCPhCCCH(CO₂Me)}(PPh₃)Cp* (R = Me 6 or Et 7)] and with HCCSiMe₃ to give a mixture of Ru{η³-CH(CO₂Me)C(CHCHSiMe₃)CCPhCCSiMe₃}(PPh₃)Cp* 8 and Ru{η³-CH(CO₂Me)CHCCPh(CCSiMe₃)}(PPh₃)Cp* 9. Crystal structures of 1, 3 and 5–8 were determined. These reactions provide routes to the stepwise formation of novel non-cyclic oligomers of 1-alkynes, with 8 containing the first example derived from four alkynes.