title: Directing aryl-I versus Aryl-Br bond activation by nickel via a ring walking process.
abstract: Activation of a strong aryl-Br bond of a halogenated vinylarene by nickel(0) is demonstrated in the presence of aryl-I containing substrates. eta2-Coordination of Ni(PEt3)2 to the C=C moiety of halogenated vinylarenes is kinetically preferable and is followed by an intramolecular aryl-halide bond activation process. This "ring-walking" process is quantitative and proceeds under mild reaction conditions in solution. Mechanistic studies indicate that the metal insertion into the aryl-halide bond is not the rate-determining step. The reaction obeys first-order kinetics in the eta2-coordination complexes with almost identical activation parameters for Br and I derivatives. The ring-walking process is kinetically accessible as shown by density functional theory (DFT) calculations at the PBE0/SDB-cc-pVDZ//PBE0/SDD level of theory.
authors.affiliation: Departments of Organic Chemistry and Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Olena V
authors.initials: OV
authors.lastname: Zenkina
authors.forename: Amir
authors.initials: A
authors.lastname: Karton
authors.forename: Dalia
authors.initials: D
authors.lastname: Freeman
authors.forename: Linda J W
authors.initials: LJ
authors.lastname: Shimon
authors.forename: Jan M L
authors.initials: JM
authors.lastname: Martin
authors.forename: Milko E
authors.initials: ME
authors.lastname: van der Boom