|Title:||Mechanism and activity of ruthenium olefin metathesis catalysts : the role of ligands and substrates from a theoretical perspective|
|Authors :||Adlhart, Christian|
|Published in :||Journal of the American Chemical Society|
|Publisher / Ed. Institution :||American Chemical Society|
|License (according to publishing contract) :||Licence according to publishing contract|
|Type of review:||Peer review (Publication)|
|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|
|Appears in Collections:||Publikationen Life Sciences und Facility Management|
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