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Ni-, Pd-, or Pt-catalyzed ethylene dimerization: a mechanistic description of the catalytic cycle and the active species

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Title Ni-, Pd-, or Pt-catalyzed ethylene dimerization: a mechanistic description of the catalytic cycle and the active species
 
Creator ROY, D
SUNOJ, RB
 
Subject density-functional theory
heck reaction
agostic interactions
asymmetric hydrovinylation
homogeneous hydrogenation
polymerization catalysts
olefin polymerization
carbonyl-complexes
phosphine-ligands
rhodium complexes
 
Description Two key mechanistic possibilities for group 10 transition metal [M(eta(3)-allyl)(PMe(3))](+) catalyzed (where M = Ni(II), Pd(II) and Pt(II)) ethylene dimerization are investigated using density functional theory methods. The nature of the potential active catalysts in these pathways is analyzed to gain improved insights into the mechanism of ethylene dimerization to butene. The catalytic cycle is identified as involving typical elementary steps in transition metal-catalyzed C-C bond formation reactions, such as oxidative insertion as well as beta-H elimination. The computed kinetic and thermodynamic features indicate that a commonly proposed metal hydride species (L(n)M-H) is less likely to act as the active species as compared to a metal-ethyl species (L(n)M-CH(2)CH(3)). Of the two key pathways considered, the active species is predicted to be a metal hydride in pathway-1, whereas a metal alkyl complex serves as the active catalyst in pathway-2. A metal-mediated hydride shift from a growing metal alkyl chain to the ethylene molecule, bound to the metal in an eta(2) fashion, is predicted to be the preferred route for the generation of the active species. Among the intermediates involved in the catalytic cycle, metal alkyls with a bound olefin are identified as thermodynamically stable for all three metal ions. In general, the Ni-catalyzed pathways are found to be energetically more favorable than those associated with Pd and Pt catalysts.
 
Publisher ROYAL SOC CHEMISTRY
 
Date 2011-08-28T14:15:53Z
2011-12-26T12:58:04Z
2011-12-27T05:47:13Z
2011-08-28T14:15:53Z
2011-12-26T12:58:04Z
2011-12-27T05:47:13Z
2010
 
Type Article
 
Identifier ORGANIC & BIOMOLECULAR CHEMISTRY, 8(5), 1040-1051
1477-0520
http://dx.doi.org/10.1039/b921492e
http://dspace.library.iitb.ac.in/xmlui/handle/10054/11760
http://hdl.handle.net/10054/11760
 
Language en