Home About us Contact
|
Home About us Contact | ||
|
|
||
Transition Metal Catalysts (transition + metal_catalyst)
Selected AbstractsCarbon,Carbon Bond Cleavage of Diynes Through the Hydroamination with Transition Metal Catalysts.CHEMINFORM, Issue 40 2003Tomohiro Shimada No abstract is available for this article. [source] Selective, Catalytic Carbon,Carbon Bond Activation and Functionalization Promoted by Late Transition Metal Catalysts.CHEMINFORM, Issue 22 2003Suzanne C. Bart Abstract For Abstract see ChemInform Abstract in Full Text. [source] FI Catalysts: A Molecular Zeolite for Olefin PolymerizationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Haruyuki Makio Abstract A bis(phenoxyimine) group 4 transition metal catalyst (now known as FI catalysts) can discern ethylene from a mixture of ethylene and propylene at more than 99% selectivity. Denisty function theory (DFT) calculations revealed a spatially confined reaction site in the transition states of the migratory insertion which is just the right size for an ethylene molecule but too small for a propylene one. The substituents adjacent to the phenoxy-oxygens are of crucial importance in developing the size/shape-selectivity. [source] Effects of MgCl2 Crystallographic Structure on Active Centre Formation in Immobilized Single-Centre and Ziegler,Natta Catalysts for Ethylene PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2008Rubin Huang Abstract The ability of a MgCl2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu2 with HCl gave high activity with TiCl4 but low activity with (n -PrCp)2ZrCl2. High polymerization activities with the zirconocene were only obtained with supports of type MgCl2/AlRn(OEt)3,n prepared from the reaction of AlR3 with MgCl2,·,1.1EtOH. These supports are characterized by additional peaks in the X-ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species. [source] Z Ma, W-H Sun, N Zhu, Z Li, C Shao, Y Hu, ,Preparation of silica-supported late transition metal catalyst and ethylene polymerization' Polymer International51(4) 2002, 349,352POLYMER INTERNATIONAL, Issue 6 2002Article first published online: 23 MAY 200 The original article to which this correction refers was published in Polymer International 51(4)2002, 349,352 [source] Design of new poly(ethylene) based materials by coordination (co)polymerization of macromonomers with ethylene,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006J.-F. Lahitte Abstract The present work discusses first the homopolymerization of , -allyl, , -undecenyl or , -vinylbenzyl polystyrene (PS) macromonomers in the presence of selected early or late transition metal catalysts. Homopolymerization degrees were found to depend on the type of catalyst, the terminal double bond, the polymerization temperature and the concentration of the various species. Higher molar masses were reached at low temperatures and low catalyst and cocatalyst concentrations. Best results were obtained with the constrained geometry catalyst (CGC)-Ti. The same PS macromonomers were copolymerized with ethylene in the presence of the VERSIPOLTM catalyst to design a new type of poly(ethylene) based graft copolymer. The macromonomer weight percent content decreases with increasing ethylene pressure whereas the molar mass of the copolymer increases with ethylene pressure. The PS macromonomer content as well as the molar mass of the copolymer can be still increased by using ,,, -difunctional PS macromonomers. The dilute solution and solid-state behavior of these copolymers were examined and compared to those of poly(ethylenes) prepared under the same conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Transition metal catalyzed carbon-silicon bond forming reactions using chlorosilanes promoted by Grignard reagentsTHE CHEMICAL RECORD, Issue 1 2007Jun Terao Abstract New catalytic CSi bond-forming reactions using chlorosilanes are described. These reactions proceed efficiently under mild conditions by the combined use of Grignard reagents and transition metal catalysts, such as Ti, Zr, Ni, and Pd. It is proposed that ate complex intermediates formed by the reaction of transition metals with Grignard reagents play important roles as the active catalytic species. The present study demonstrates the practical use of chlorosilanes in transition metal catalyzed silylation reactions providing convenient methods for allyl- or vinylsilane synthesis. The reaction pathways of these transformations as well as the scope and limitations are discussed. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 57,67; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20101 [source] Hydrosilylation conditions applied on alkenyl benzylated xyloses: selective reduction and isomerizationAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2009Caroline Hadad Abstract In the presence of triethylsilane and different transition metal catalysts, the main reactive pathways observed from benzylated xyloses bearing an unsaturated tether were the reduction and the isomerization of the double bond without debenzylation of the sugar moiety. Copyright © 2009 John Wiley & Sons, Ltd. [source] Surface of Metallic Catalysts under a Pressure of Hydrocarbon Molecules: Metal or Carbide?CHEMCATCHEM, Issue 6 2010Philippe Sautet Dr. What have I done to the surface? The nature of the surface of a solid catalyst can be modified by the reactants; molecular decomposition can produce new phases in the near-surface region, changing the catalytic properties in,situ. First-principle calculations show trends among transition metal catalysts for the formation of a surface carbide from a range of hydrocarbon molecules or CO. Pd, Ni, and Fe are most prone to carbon penetration in the subsurface. [source] 1-Alkynylphosphines and Their Derivatives as Key Starting Materials in Creating New PhosphinesCHEMISTRY - AN ASIAN JOURNAL, Issue 3 2010Azusa Kondoh Abstract This Focus Review summarizes transformations of 1-alkynylphosphines and their derivatives directed toward the synthesis of new phosphines. Owing to the importance of organophosphines as ligands for transition metal catalysts, development of efficient methods for the synthesis of new phosphines is quite important. 1-Alkynylphosphines and their derivatives have been emerging as useful precursors for the creation of new phosphines. Chemical modifications of the carbon,carbon triple bonds, including nucleophilic addition and cycloaddition, lead to a wide range of new useful phosphines that are otherwise difficult to synthesize. [source] | |||||||||||||||||||||||||