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Generation Grubbs' Catalyst (generation + grubb_catalyst)
Selected AbstractsOlefin metathesis applied to cellulose derivatives,Synthesis, analysis, and properties of new crosslinked cellulose plastic filmsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Nicolas Joly Abstract New crosslinked cellulose-based plastic films were synthesized with olefin metathesis as a crosslinking reaction. Microcrystalline cellulose was first dissolved in a lithium chloride/N,N -dimethylacetamide solvent system and acylated by ,-undecenoyl chloride under microwave irradiation with N,N -dimethyl-4-aminopyridine as the catalyst. Cellulose unsaturated fatty acyl esters with a degree of substitution (DS) ranging from 1.4 to 2.0 were then crosslinked by olefin metathesis with a first generation Grubbs catalyst. Crosslinking ratios (T) ranging from 20 to 90% were obtained for low catalyst amounts (<1.2%), but gels appeared when T was too high. To avoid this gel formation, cellulose was acylated with a mixture of lauroyl and ,-undecenoyl chlorides. This internal dilution allowed us to obtain films of every case and various T (varying from 10 to 80% for a catalyst amount below 3.5%). Plastics were characterized by Fourier transform infrared (FTIR) spectroscopy, and the fatty acid mixture resulting from the hydrolysis of cellulose esters were analyzed by gas chromatography (GC) and NMR spectroscopy. Mechanical properties showed that the elastic modulus and tensile failure stress was higher when the plastic films were crosslinked. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 407,418, 2005 [source] Comparative DFT study on the role of conformers in the ruthenium alkylidene-catalyzed ROMP of norborn-2-eneJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2008Sergej Naumov Abstract Comparative quantum chemical calculations on the reaction pathways for the formation of ruthena(IV)cyclobutanes from both 1st - and 2nd -generation Grubbs catalysts of the general formula RuX2(L)(L,)(CH2) (L,=,PCy3 or 1,3-dimesityl-4,5-dihydroimidazolin-2-ylidene, L,,=,PCy3) and norborn-2-ene (NBE) were carried out on the B3LYP/LACVP** level in dependence on the ligand X,=,I, Br, Cl, and F. The mechanism proposed by Straub for the formation of (one) active and (three) inactive NBE,Ru,carbene complexes for non-cyclic alkenes was applied to the cyclic alkene NBE. In RuX2(PCy3)2(CH2), the inactive NBE,Ru,carbene complex is energetically more stable than the active one; however, in RuX2(IMesH2)(PCy3)(CH2), the active NBE,Ru,carbene complex is more stable than the inactive one. In due consequence, the possible rate limiting barrier for the conversion of the NBE,Ru,carbene complex into the corresponding metallocyclobutane (MCB) is systematically larger in the case of 1st -generation Grubbs catalysts than of 2nd -generation Grubbs catalysts due to an additional re-arrangement for the formation of an active , -complex from the more stable (inactive) conformer. This correlates with the observed reactivity of both types of initiators. There is a strong influence of the ligands L and X on the conformational properties and relative stabilities of the 14-electron intermediates, which has a direct effect on the distribution of the inactive and active conformations of the corresponding Ru,carbene,NBE complexes. A direct correlation between the conformational properties of the 14-electron intermediates and the relative stabilities of the active Ru,carbene,NBE complexes was observed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Efficient Functionalisation of Cubic Monovinylsilsesquioxanes via Cross-Metathesis and Silylative Coupling with Olefins in the Presence of Ruthenium ComplexesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Patrycja Abstract Monovinylheptaisobutylsilsesquioxane undergoes efficient cross-metathesis and silylative coupling with styrenes. Allyl derivatives were successfully tested in cross-metathesis in the presence of first generation Grubbs' catalyst, while heteroatom-substituted vinyl derivatives (vinyl ethers, 9-vinylcarbazole) efficiently undergo silylative coupling catalysed by ruthenium hydride complexes. Both reactions proceed highly stereoselectively and lead to nearly quantitative formation of E isomers. Only when vinyl ethers are used does the reaction lead to a mixture of stereoisomers. Atmospheric pressure photoionisation has been successfully used for recording mass spectra of the functionalised silsesquioxanes. [source] Hybrid Organic-Inorganic Materials Derived from a Monosilylated Hoveyda-type Ligand as Recyclable Diene and Enyne Metathesis CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2007Xavier Elias Abstract The synthesis of a monosilylated Hoveyda-type monomer is described as well as the preparation of several organic-inorganic hybrid materials derived from it by sol-gel processes and by anchoring to commercial silica gel and MCM-41. The resulting materials were treated with first and/or second generation Grubbs' catalyst to generate Hoveyda,Grubbs' type alkylidene ruthenium complexes covalently bonded to the silica matrix. These materials are efficient recyclable catalysts for the ring-closing metathesis reaction of dienes and enynes, even for the formation of tri- and tetrasubstituted olefins. [source] Hybrid-Bridged Silsesquioxane as Recyclable Metathesis Catalyst Derived from a Bis-Silylated Hoveyda-Type LigandADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2006Xavier Elias Abstract The synthesis of a bis-silylated Hoveyda-type monomer is described as well as the preparation of several organic-inorganic hybrid materials derived from it by a sol-gel process (with and without tetraethyl orthosilicate) and by anchoring to MCM-41. The resulting materials were treated with second generation Grubbs' catalyst to generate second generation Hoveyda,Grubbs-type alkylideneruthenium complexes covalently bonded to the silica matrix. These materials are recyclable catalysts for the ring-closing metathesis reaction of dienes and enynes. [source] | ||||||||||