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

Abstract

Tricyclooctylphosphine PCoc 3 ( 1), which has been prepared from PCl 3 and cyclooctyl Grignard reagent, reacts under an atmosphere of H 2 with the dimer [RuCl 2(η 3:η 3-C 10H 16)] 2 ( 2) to give the hydrido(dihydrogen) complex [RuHCl(H 2)(PCoc 3) 2] ( 4); in contrast, treatment of 2 with PPh 3 under the same conditions affords [RuHCl(PPh 3) 3] ( 3). The reaction of 4 with acetylene in the presence of MgCl 2 and water leads to the formation of the ruthenium carbene [RuCl 2(CHCH 3)(PCoc 3) 2] ( 5) in 70% isolated yield. In the absence of MgCl 2 and water, 4 reacts with acetylene at low temperature to give the hydrido(vinylidene) complex [RuHCl(CCH 2)(PCoc 3) 2] ( 6) almost quantitatively. Compounds 5, 6 and [RuH(κ 2-O 2CCF 3)(CCH 2)(PCoc 3) 2] ( 7), the latter being obtained from 6 and CF 3CO 2K by ligand exchange, are poor catalysts for ROMP and cross olefin metathesis.