title: A mechanistic investigation of carbon-hydrogen bond stannylation: synthesis and characterization of nickel catalysts.
abstract: The complex ((i)Pr(3)P)Ni(η(2)-Bu(3)SnCH=CH(2))(2) (1a) was characterized by NMR spectroscopy and was identified as the active species for catalytic C-H bond stannylation of partially fluorinated aromatics, for example in the reaction between pentafluorobenzene and Bu(3)SnCH=CH(2), which generates C(6)F(5)SnBu(3) and ethylene. The crystalline complex ((i)Pr(3)P)Ni(η(2)-Ph(3)SnCH=CH(2))(2) (1b) provides a more easily handled analogue, and is also capable of catalytic stannylation with added Ph(3)SnCH=CH(2) and C(6)F(5)H. Mechanistic studies on 1b show that the catalytically active species remains mononuclear. The rate of catalytic stannylation is proportional to [C(6)F(5)H] and inversely proportional to [Ph(3)SnCH=CH(2)]. This is consistent with a mechanism where reversible Ph(3)SnCH=CH(2) dissociation provides ((i)Pr(3)P)Ni(η(2)-Ph(3)SnCH=CH(2)), followed by a rate-determining reaction with C(6)F(5)H to generate the stannylation products. Kinetic competition reactions between the fluorinated aromatics pentafluorobenzene, 1,2,4,5-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene and 1,3-difluorobenzene all suggest significant Ni-aryl bond formation in the rate-determining step under catalytic conditions. Labelling studies are consistent with an insertion of the hydrogen of the arene into the vinyl group, followed by β-elimination or β-abstraction of the SnPh(3) moiety.
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada. sjohnson@uwindsor.ca
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Johnson
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Doster
authors.forename: Jacob
authors.initials: J
authors.lastname: Matthews
authors.forename: Manar
authors.initials: M
authors.lastname: Shoshani
authors.forename: Michelle
authors.initials: M
authors.lastname: Thibodeau
authors.forename: Amanda
authors.initials: A
authors.lastname: Labadie
authors.forename: Jillian A
authors.initials: JA
authors.lastname: Hatnean