title: Hydrosilylation of ketones, imines and nitriles catalysed by electrophilic phosphonium cations: functional group selectivity and mechanistic considerations.
abstract: The electrophilic phosphonium salt, [(C6 F5 )3 PF][B(C6 F5 )4 ], catalyses the efficient hydrosilylation of ketones, imines and nitriles at room temperature. In the presence of this catalyst, adding one equivalent of hydrosilane to a nitrile yields a silylimine product, whereas adding a second equivalent produces the corresponding disilylamine. [(C6 F5 )3 PCl][B(C6 F5 )4 ] and [(C6 F5 )3 PBr][B(C6 F5 )4 ] are also synthesised and tested as catalysts. Competition experiments demonstrate that the reaction exhibits selectivity for the following functional groups in order of preference: ketone>nitrile>imine>olefin. Computational studies reveal the reaction mechanism to involve initial activation of the Si-H bond by its interaction with the phosphonium centre. The activated complex then acts cooperatively on the unsaturated substrate.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6 (Canada).
authors.forename: Manuel
authors.initials: M
authors.lastname: Pérez
authors.forename: Zheng-Wang
authors.initials: ZW
authors.lastname: Qu
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Caputo
authors.forename: Vitali
authors.initials: V
authors.lastname: Podgorny
authors.forename: Lindsay J
authors.initials: LJ
authors.lastname: Hounjet
authors.forename: Andreas
authors.initials: A
authors.lastname: Hansen
authors.forename: Roman
authors.initials: R
authors.lastname: Dobrovetsky
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Stephan
keywords: homogeneous catalysis; hydrosilylation; phosphonium; reaction mechanisms; selectivity