title: Pyridinium-phosphonium dications: highly electrophilic phosphorus-based Lewis acid catalysts.
abstract: Using commercially available 2-pyridyldiphenylphosphine (o-NC5H4)PPh2, a family of electrophilic phosphonium cations [(o-NC5H4)PFPh2](+) (2) and dications [(o-MeNC5H4)PRPh2](2+) (R = F (4); Me (5)) were prepared. The Lewis acidity of these pyridinium-phosphonium dications was probed in Friedel-Crafts dimerization, hydrodefluorination, hydrosilylation, dehydrocoupling and hydrodeoxygenation reactions. The influence of the counterion on the catalytic activity of the electrophilic phosphonium cations is also discussed.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6. dstephan@chem.utoronto.ca.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Bayne
authors.forename: Michael H
authors.initials: MH
authors.lastname: Holthausen
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Stephan