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Synthesis and characterization of [Ru(1-3:5,6-η-cyclooctadienyl)(η6-cyclooctatriene)]PF 6 and its use as a precursor into 1-3:5,6-η- and 1-5-η-cyclooctadienyl ruthenium(II) complexes. The X-ray crystal structure determinations of [Ru(1-3:5,6-η-cyclooctadienyl)(η6-cyclooctatriene)]PF 6 ...
Ashworth, Terence V.,Chalmers, Anthony A.,Liles, David C.,Meintjies, Elsie,Singleton, Eric
, p. 1543 - 1552 (2008/10/08)
Full title: Synthesis and characterization of [Ru(1-3:5,6-η-cyclooctadienyl)(η6-cyclooctatriene)]PF 6 and its use as a precursor into 1-3:5,6-η- and 1-5-η-cyclooctadienyl ruthenium(II) complexes. The X-ray crystal structure determinations of [Ru(1-3:5,6-η-cyclooctadienyl)(η6-cyclooctatriene)]PF 6 and [Ru(1-5-η-cyclooctadienyl)(PMe2Ph)3]PF6. Treatment of the complex [RuH(cod)(NH2NMe2)3]PF6 (1) (cod = cycloocta-1,5-diene) in methanol or acetone solutions with excess cyclooctatetraene gives the salt [Ru(1-3:5,6-η-cyclooctadienyl)(η 6-1,3,5-cyclooctatriene)]PF6 (2) in 30% yield. A mechanism involving intramolecular hydrogen transfer is proposed to explain the formation of the η6-1,3,5-cyclooctatriene ligand. Variable-temperature NMR studies demonstrate that 2 is fluxional with two distinct species being observed at 303 and 190 K. The structure of 2 was assigned from the limiting slow-exchange 13C (125.5 MHz) and 1H (500.12 MHz) NMR at 190 K. The solution structure at low temperature can be readily related to the solid-state structure as determined by X-ray crystallography. Complex 2 reacts with isocyanides and CO to give [Ru(1-3:5,6-η-C8H11)L3]PF6 (3) (L = CO, CNR; R = t-Bu, 2,6-Me2C6H3), whereas with more sterically demanding ligands, isomerization of the 1-3:5,6-η-C8H11 ligands occurs to give the 1-5-η-complexes [Ru(1-5-η-C8H11)L3]PF6 (4) (L = P(OMe)3, PMe2Ph, AsMe2Ph, and AsMePh2). 4 (L = PMe2Ph, and AsMePh2) may also be obtained by heating a solution of [RuH(cod)L3]PF6 (5) (L = PMe2Ph and AsMePh2) in methanol or dioxane in the presence of excess cod that acts as a hydrogen acceptor. The crystal and molecular structures of 2 and 4 (L = PMe2Ph) have been determined by X-ray diffraction techniques and refined to conventional R factors of 0.0673 and 0.0531, respectively. The activation energy for the isomerization of the C8H11 ligand from the 1-3:5,6-η-to the 1-5-η-form is provided, most likely, by the build-up of steric strain energy within the molecule. Projection diagrams reveal the larger cone angle of the 1-3:5,6-η-form. All the new compounds were isolated as analytically pure solids and were characterized by IR and 1H and 13C{1H} NMR spectroscopy.
