Evaluation of the carbene hydride mechanism in the carbon-carbon bond formation process of alkane metathesis through a DFT study.
Olefin metathesis on a silica supported tantalumhydridocarbene complex, the key carbon-carbon making process in alkane metathesis, requires a large number of elementary steps in contrast to the known olefin metathesis pathway, which corresponds to successive [2 + 2]-cycloaddition and cycloreversion steps. The direct pathway is forbidden because it requires the formation of a high energy reaction intermediates, an olefin adduct of trigonal bipyramid (TBP) geometry, where the carbene is trans to an hydride ligand. Extra low-energy steps are therefore necessary to connect the reactants to products, the key being a turnstile interconversion at the metallacyclobutane intermediates.
Schinzel
Sandra
S
Université Lyon-1, Laboratoire de Chimie-Physique Théorique, Université de Lyon, and CNRS UMR 5180 Sciences Analytiques, Bât Dirac, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France.
Chermette
Henry
H
Copéret
Christophe
C
Basset
Jean-Marie
JM