title: Decomposition of ruthenium olefin metathesis catalysts.
abstract: The decomposition of a series of ruthenium metathesis catalysts has been examined using methylidene species as model complexes. All of the phosphine-containing methylidene complexes decomposed to generate methylphosphonium salts, and their decomposition routes followed first-order kinetics. The formation of these salts in high conversion, coupled with the observed kinetic behavior for this reaction, suggests that the major decomposition pathway involves nucleophilic attack of a dissociated phosphine on the methylidene carbon. This mechanism also is consistent with decomposition observed in the presence of ethylene as a model olefin substrate. The decomposition of phosphine-free catalyst (H2IMes)(Cl)2Ru=CH(2-C6H4-O-i-Pr) (H2IMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) with ethylene was found to generate unidentified ruthenium hydride species. The novel ruthenium complex (H2IMes)(pyridine)3(Cl)2Ru, which was generated during the synthetic attempts to prepare the highly unstable pyridine-based methylidene complex (H2IMes)(pyridine)2(Cl)2Ru=CH2, is also reported.
authors.affiliation: Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Soon Hyeok
authors.initials: SH
authors.lastname: Hong
authors.forename: Anna G
authors.initials: AG
authors.lastname: Wenzel
authors.forename: Tina T
authors.initials: TT
authors.lastname: Salguero
authors.forename: Michael W
authors.initials: MW
authors.lastname: Day
authors.forename: Robert H
authors.initials: RH
authors.lastname: Grubbs
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D005030:Ethylenes / Q000737:chemistry; D008967:Molecular Biology; D015394:Molecular Structure; D010720:Phosphines / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D000475:Alkenes; D005030:Ethylenes; D010720:Phosphines; C016629:olefin sulfate; D012428:Ruthenium; C036216:ethylene