Synthesis, crystal structures and reactivity of ruthenium-(II) and -(III) complexes containing β-ketophosphine or phosphino enolate ligands

Abstract

Reaction of 1, 2 or 3 equivalents of (diphenylphosphino)acetophenone, Ph₂PCH₂C(O)Ph (L), with [RuCl₂(PPh₃)₃] in toluene afforded selectively trans,mer-[[graphic omitted])Ph}(PPh₃)₂]1, trans,cis,cis-[[graphic omitted])Ph}₂]2 or trans,mer-[[graphic omitted])Ph}{Ph₂PCH₂C(O)Ph}₂]3, respectively. Complex 1 hydrogenates and isomerises hex-1-ene at atmospheric hydrogen pressure, whereas 2 is inactive. Complex 3 exhibits a dynamic behaviour on the ¹H NMR time-scale which corresponds to exchange between chelating and terminally bound phosphines. The activation energy of this process was calculated to be 63.7 ± 0.7 kJ mol^–1. Reaction of 3 with TIPF₆ in CH₂Cl₂ gave mer-[[graphic omitted])Ph}₂{Ph₂PCH₂C(O)Ph}]PF₆9 which reacted with a second equivalent of TIPF₆ in MeCN to give the dicationic complex trans,cis,cis-[[graphic omitted];)Ph}₂(NCMe)₂][PF₆]₂10. The fac and mer isomers of the tris(enolato) Ru^II complex [Na][[graphic omitted])Ph}₃]11a and 11b were obtained by reaction of 9 with NaH in tetrahydrofuran (thf). Treatment of 3 with NaOMe in toluene afforded selectively 11b, which has been crystallised by addition of 1,4,7,10,13-pentaoxacyclopentadecane (15-crown-5) to give [Na(15-crown-5)·H₂O][mer-[graphic omitted])Ph}₃]·thf 12. Protonation of 11b with HBF₄·Et₂O gave the neutral intermediate mer-[[graphic omitted])Ph}]13, characterised spectroscopically, and the final product mer-[[graphic omitted])Ph}₃][BF₄]₂14. Treatment of [RuCl₃(AsPh₃)₂(MeOH)] with 2 equivalents of L yielded the ruthenium(III) complex mer,trans-[[graphic omitted])Ph}{Ph₂PCH₂C(O)Ph}]15, which was easily reduced to the ruthenium(II) complex 2. The solid state structures of complexes 2, 10 and 12 have been determined by single crystal X-ray analysis. The co-ordination of the metal in 2 and 10 is slightly distorted octahedral with the two phosphorous atoms (and oxygen atoms) in a cis position and the chloride and acetonitrile ligands, respectively, in a trans position. In the chiral anion of complex 12 the distorted octahedral structure has a meridional arrangement of the P atoms and electronic delocalisation occurs within the chelating phosphino enolate ligands.