title: CH Bond Activation of Methane by a Transient η(2)-Cyclopropene/Metallabicyclobutane Complex of Niobium.
abstract: This study challenges the problem of the activation of a CH bond of methane by soluble transition metal complexes. High pressure solution NMR, isotopic labeling studies, and kinetic analyses of the degenerate exchange of methane in the methyl complex [Tp(Me2)NbCH3(c-C3H5)(MeCCMe)] (1) are reported. Stoichiometric methane activation by the mesitylene complex [Tp(Me2)Nb(CH2-3,5-C6H3Me2)(c-C3H5) (MeCCMe)] (2) giving 1 is also realized. Evidence is provided that these reactions proceed via an intramolecular abstraction of a β-H of the cyclopropyl group to form either methane or mesitylene from 1 or 2, respectively, yielding the transient unsaturated η(2)-cyclopropene/metallabicyclobutane intermediate [Tp(Me2)Nb(η(2)-c-C3H4) (MeCCMe)] A. This is followed by its mechanistic reverse 1,3-CH bond addition of methane yielding the product.
authors.affiliation: CNRS , LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP44099, F-31077 Toulouse Cedex 4, France.|Université de Toulouse , INSA-CNRS-UPS, LPCNO, 135 Avenue Rangueil, F-31077 Toulouse, France.
authors.forename: Chen
authors.initials: C
authors.lastname: Li
authors.affiliation: CNRS , LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP44099, F-31077 Toulouse Cedex 4, France.|Université de Toulouse , UPS, INPT, LCC, F-31077 Toulouse Cedex 4, France.
authors.forename: Chiara
authors.initials: C
authors.lastname: Dinoi
authors.affiliation: CNRS , LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP44099, F-31077 Toulouse Cedex 4, France.|Université de Toulouse , UPS, INPT, LCC, F-31077 Toulouse Cedex 4, France.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Coppel
authors.affiliation: CNRS , LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP44099, F-31077 Toulouse Cedex 4, France.|Université de Toulouse , UPS, INPT, LCC, F-31077 Toulouse Cedex 4, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Etienne