title: Direct observation of reaction intermediates for a well defined heterogeneous alkene metathesis catalyst.
abstract: Grafting of [W([triple bond]NAr)(=CHtBu)(2,5-Me(2)NC(4)H(2))(2)] on a silica partially dehydroxylated at 700 degrees C (SiO(2- (700))) generates the corresponding monosiloxy complex [([triple bond]SiO)W([triple bond]NAr)(=CHtBu)(2,5-Me(2)NC(4)H(2))] as the major species (approximately 90%) along with [([triple bond]SiO)W([triple bond]NAr)(CH(2)tBu)(2,5-Me(2)NC(4)H(2))(2)], according to mass balance analysis, IR, and NMR studies. This heterogeneous catalyst displays good activity and stability in the metathesis of propene. Very importantly, solid state NMR spectroscopy allows observation of the propagating alkylidene as well as stable metallacyclobutane intermediates. These species have the same reactivity as the initial surface complex [([triple bond]SiO)W([triple bond]NAr)(=CHtBu)(2,5-Me(2)NC(4)H(2))], which shows that they are the key intermediates of alkene metathesis.
authors: Institut de Chimie de Lyon, Ecole Supérieure Chimie Physique Electronique de Lyon/Centre National de la Recherche Scientifique/Université Lyon 1, Villeurbanne, France.
authors: Frédéric
authors: F
authors: Blanc
authors: Romain
authors: R
authors: Berthoud
authors: Christophe
authors: C
authors: Copéret
authors: Anne
authors: A
authors: Lesage
authors: Lyndon
authors: L
authors: Emsley
authors: Rojendra
authors: R
authors: Singh
authors: Thorsten
authors: T
authors: Kreickmann
authors: Richard R
authors: RR
authors: Schrock