title: Bimetallic oxidative addition involving radical intermediates in nickel-catalyzed alkyl-alkyl Kumada coupling reactions.
abstract: Many nickel-based catalysts have been reported for cross-coupling reactions of nonactivated alkyl halides. The mechanistic understanding of these reactions is still primitive. Here we report a mechanistic study of alkyl-alkyl Kumada coupling catalyzed by a preformed nickel(II) pincer complex ([(N2N)Ni-Cl]). The coupling proceeds through a radical process, involving two nickel centers for the oxidative addition of alkyl halide. The catalysis is second-order in Grignard reagent, first-order in catalyst, and zero-order in alkyl halide. A transient species, [(N2N)Ni-alkyl(2)](alkyl(2)-MgCl), is identified as the key intermediate responsible for the activation of alkyl halide, the formation of which is the turnover-determining step of the catalysis.
authors.affiliation: Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, ISIC-LSCI, BCH 3305, Lausanne, CH 1015, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Breitenfeld
authors.forename: Jesus
authors.initials: J
authors.lastname: Ruiz
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Wodrich
authors.forename: Xile
authors.initials: X
authors.lastname: Hu