A tertiary phosphine that is too bulky: preparation of catalytically less active carbene and vinylidene ruthenium(II) complexes

Tricyclooctylphosphine PCoc3 (1), which has been prepared from PCl3 and cyclooctyl Grignard reagent, reacts under an atmosphere of H2 with the dimer [RuCl2(η3:η3-C10H16)]2 (2) to give the hydrido(dihydrogen) complex [RuHCl(H2)(PCoc3)2] (4); in contrast, treatment of 2 with PPh3 under the same conditions affords [RuHCl(PPh3)3] (3). The reaction of 4 with acetylene in the presence of MgCl2 and water leads to the formation of the ruthenium carbene [RuCl2(CHCH3)(PCoc3)2] (5) in 70% isolated yield. In the absence of MgCl2 and water, 4 reacts with acetylene at low temperature to give the hydrido(vinylidene) complex [RuHCl(CCH2)(PCoc3)2] (6) almost quantitatively. Compounds 5, 6 and [RuH(κ2-O2CCF3)(CCH2)(PCoc3)2] (7), the latter being obtained from 6 and CF3CO2K by ligand exchange, are poor catalysts for ROMP and cross olefin metathesis.