General Considerations.Manipulation of organometallic compounds was performed using

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 (H 2IMes)(Cl)2RudCH(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 pyridinebased methylidene complex (H2IMes)(pyridine)2(Cl)2RudCH2, is also reported.

General Considerations. Manipulation of organometallic compounds was performed using standard Schlenk techniques under an atmosphere of dry argon or in a nitrogen-filled Vacuum Atmospheres drybox (O 2 < 2 ppm). NMR spectra were recorded on a Varian Inova (499. Methyltricyclohexylphosphonium chloride 9 was obtained along with some unidentified decomposed ruthenium species by the addition of pentane (5 mL) to the filtered benzene solution.Dinuclear ruthenium complex 8.

General Considerations. Manipulation of organometallic compounds was performed using standard Schlenk techniques under an atmosphere of dry argon or in a nitrogen-filled Vacuum Atmospheres drybox (O 2 < 2.5 ppm). NMR spectra were recorded on a Varian Mercury 300 (299.817 MHz for 1 H; 75.4 MHz for 13 C). D 2 O was purchased from Cambridge Isotope Laboratories and degassed by bubbling with Ar. Puriss water was purchased from Aldrich and degassed by bubbling with Ar. The starting materials, 5 1 and 6 2 were prepared according to literature procedure. Substrates

Amides are synthesized directly from alcohols and amines in high yields using an in situ generated catalyst from easily available ruthenium complexes such as the (p-cymene, an N-heterocyclic carbene (NHC) ligand, and a nitrogen containing L-type ligand such as acetonitrile. The phosphine-free catalyst systems showed improved or comparable activity compared to previous phosphine-based catalytic systems. The in situ generated catalyst from [RuA C H T U N G T R E N N U N G (benzene)Cl 2 ] 2 , an NHC ligand, and acetonitrile showed excellent activity toward reactions with cyclic secondary amines such as piperidine and morpholine.

Communication Ruthenium Olefin Metathesis Catalysts for the Ethenolysis of Renewable FeedstocksRuthenium olefin metathesis catalysts have been evaluated for the ethenolysis of methyl oleate, a natural seed oil derivative, to produce useful terminal olefins. Several N-heterocyclic carbene-based ruthenium catalysts demonstrate good activity and selectivity for the formation of terminal olefins. In particular, catalysts (10) and (21) achieved higher TONs (A20 000).

An in situ generated catalyst from readily available RuH(2)(PPh(3))(4), an N-heterocyclic carbene (NHC) precursor, NaH, and acetonitrile was developed. The catalyst showed high activity for the amide synthesis directly from either alcohols or aldehydes with amines. When a mixture of an alcohol and an aldehyde was reacted with an amine, both of the corresponding amides were obtained with good yields. Homogeneous Ru(0) complexes such as (eta(4)-1,5-cyclooctadiene)(eta(6)-1,3,5-cyclooctatriene)ruthenium [Ru(cod)(cot)] and Ru(3)(CO)(12) were also active in the amidation of an alcohol or an aldehyde with the help of an in situ generated NHC ligand.

Well-defined N-heterocyclic carbene based ruthenium complexes were developed as highly active catalysts for direct amide synthesis from alcohols and amines. A catalytic amount of a base such as KOtBu was essential to initiate the catalytic cycle. Activity of the Ru complexes was comparable with the reported in situ Ru catalysts. These catalysts provided mechanistic insight suggesting a Ru hydride species as an active catalytic intermediate. The generation of the Ru hydride was critical for the amidation of free aldehydes.