American Chemical Society
ja1061505_si_002.cif (26.82 kB)

C−H Bond Activation of Benzene by Unsaturated η2-Cyclopropene and η2-Benzyne Complexes of Niobium

Download (26.82 kB)
posted on 2010-10-13, 00:00 authored by Cédric Boulho, Pascal Oulié, Laure Vendier, Michel Etienne, Véronique Pimienta, Abel Locati, Fabienne Bessac, Feliu Maseras, Dimitrios A. Pantazis, John E. McGrady
We report the synthesis of a niobium cyclopropyl complex, TpMe2NbMe(c-C3H5)(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 η2-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 η2-alkene complexes but is favored in this case by the strain in the C3 ring which prevents the decomposition of the key intermediate via loss of cyclopropene.