title: [Ru(NHC)(xantphos)(CO)H(2)] complexes: intramolecular C-H activation and applications in C-C bond formation.
abstract: Treatment of [Ru(PPh3)(xantphos)(CO)H2] (1) with the N-heterocyclic carbenes (NHCs) IEt2Me2 (1,3-diethyl-4,5-dimethylimidazol-2-ylidene), IiPr2Me2 (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) and IMes (1,3-dimesitylimidazol-2-ylidene) at elevated temperature affords the C-H activated carbene complexes [Ru(NHC)(xantphos)(CO)H] (2-4). In contrast, ICy (1,3-dicyclohexylimidazol-2-ylidene) reacts with 1 to give the substitution product [Ru(ICy)(xantphos)(CO)H2] (6), which can be converted into the C-H activated species [Ru(ICy)(xantphos)(CO)H] (7) upon thermolysis in the presence of H2CCHSiMe3. Addition of H2 to 2 yields [Ru(IEt2Me2)(xantphos)(CO)H2] (5), while H2 reacts with 7 to reform 6. Complexes 2-4 and 7 catalyse the Knoevenagel reaction of PhCH2OH with tBuC(O)CH2CN, although they prove to be somewhat less active than the phosphine complex 1.
authors.affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY.
authors.forename: Araminta E W
authors.initials: AE
authors.lastname: Ledger
authors.forename: Mary F
authors.initials: MF
authors.lastname: Mahon
authors.forename: Michael K
authors.initials: MK
authors.lastname: Whittlesey
authors.forename: Jonathan M J
authors.initials: JM
authors.lastname: Williams
mesh_terms: D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D013237:Stereoisomerism; D014966:Xanthenes / Q000737:chemistry*
chemical_list: D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D014966:Xanthenes; C030011:carbene; D012428:Ruthenium; D008697:Methane