title: C-H bond activation of benzene by unsaturated η2-cyclopropene and η2-benzyne complexes of niobium.
abstract: We report the synthesis of a niobium cyclopropyl complex, Tp(Me2)NbMe(c-C(3)H(5))(MeCCMe), and show that thermal loss of methane from this compound generates an intermediate that is capable of activating both aliphatic and aromatic C-H bonds. Isotopic labeling, trapping studies, a detailed kinetic analysis, and density functional theory all suggest that the active intermediate is an η(2)-cyclopropene complex formed via β-hydrogen abstraction rather than an isomeric cyclopropylidene species. C-H activation chemistry of this type represents a rather unusual reactivity pattern for η(2)-alkene complexes but is favored in this case by the strain in the C(3) ring which prevents the decomposition of the key intermediate via loss of cyclopropene.
authors.affiliation: CNRS, Laboratoire de Chimie de Coordination, 205 Route de Narbonne, F-31077 Toulouse, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Boulho
authors.forename: Pascal
authors.initials: P
authors.lastname: Oulié
authors.forename: Laure
authors.initials: L
authors.lastname: Vendier
authors.forename: Michel
authors.initials: M
authors.lastname: Etienne
authors.forename: Véronique
authors.initials: V
authors.lastname: Pimienta
authors.forename: Abel
authors.initials: A
authors.lastname: Locati
authors.forename: Fabienne
authors.initials: F
authors.lastname: Bessac
authors.forename: Feliu
authors.initials: F
authors.lastname: Maseras
authors.forename: Dimitrios A
authors.initials: DA
authors.lastname: Pantazis
authors.forename: John E
authors.initials: JE
authors.lastname: McGrady