Introduction of a phosphorus ylide moiety into [η2-(ω-hydroxy)alkenyl]chromium(0) carbene complexes with Ph3PCCO and consecutive Wittig alkenations with 2-alkynals. Part 12: the chemistry of metallacyclic alkenylcarbene complexes

Ketenylidenetriphenylphosphorane, Ph3PCCO (2), reacts selectively with the ω-hydroxy group of the alkene–carbene complexes (OC)4CrC(η2-NMeCH2CHCHCH2OH)R1 (1) (R1=Me: (1a); Ph: (1b)) to give the acyl ylide terminated complexes (OC)4CrC[(4,5-η2)-NMeCH2CHCHCH2O(O)C–CHPPh3]R1 (3) (R1=Me: (3a); Ph: (3b)). Complexes 3 undergo Wittig alkenation reactions with aldehydes such as 2-alkynals, R2–CC–CHO (R2=H, SiMe3, Ph), to give the corresponding 4Z, 9E-dien-11-ynes (OC)4CrC[(4,5-η2)-NMeCH2CHCHCH2O(O)C–CHCH–CC–R2]R1 (4–6) (R1=Me, R2=H, SiMe3, Ph: (4a–6a); R1=Ph, R2=H, SiMe3, Ph: (4b–6b)). All complexes were characterized in solution by one- and two-dimensional NMR spectroscopy (1H, 13C, 29Si, 31P, 1H/1H COSY, 13C/1H HETCOR, 31P/31P EXSY).