Title: Mechanism and activity of ruthenium olefin metathesis catalysts : the role of ligands and substrates from a theoretical perspective
Authors : Adlhart, Christian
Chen, Peter
Published in : Journal of the American Chemical Society
Volume(Issue) : 126
Issue : 11
Pages : 3496
Pages to: 3510
Publisher / Ed. Institution : American Chemical Society
Issue Date: 25-Feb-2004
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subjects : Metathesis catalysts; Reaction mechanism; Alkene reactions; Density functional theory
Subject (DDC) : 540: Chemistry
Abstract: The reaction mechanism of olefin metathesis by ruthenium carbene catalysts is studied by gradient-cor. d. functional calcns. (BP86). Alternative reaction mechanisms for the reaction of the "first-generation" Grubbs-type catalyst (PCy3)2Cl2Ru:CH2 (1) for the reaction with ethylene are studied. The most likely dissociative mechanism with trans olefin coordination is investigated for the metathesis reaction between the "first-" and the "second-generation" Grubbs-type catalysts 1 and (H2IMes)(PCy3)Cl2Ru:CH2 (2) with different substrates, ethylene, Et vinyl ether, and norbornene, and a crucial influence of the substrate is found. In contrast to the degenerate reaction with ethylene, the reactions with Et vinyl ether and norbornene are strongly exergonic by 8-15 kcal/mol, and this excess energy is released after passing through the metallacyclobutane structure. While the metallacyclobutane is in a deep potential min. for degenerate metathesis reactions, the energy barrier for the [2+2] cycloreversion vanishes for the most exergonic reactions. On the free energy surface under typical exptl. conditions, the rate-limiting steps for the overall reactions are then either metallacyclobutane formation for 1 or phosphine ligand dissocn. for 2.
Departement: Life Sciences und Facility Management
Organisational Unit: Institute of Chemistry and Biotechnology (ICBT)
Publication type: Article in scientific Journal
DOI : 10.1021/ja0305757
ISSN: 0002-7863
URI: https://digitalcollection.zhaw.ch/handle/11475/2100
Appears in Collections:Publikationen Life Sciences und Facility Management

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