Lewis Acidity of Organofluorophosphonium Salts: Hydrodefluorination by a Saturated Acceptor

The Pull of Phosphorus Lewis acidity is primarily associated with compounds like boranes that lack a full complement of electrons in their coordination sphere and therefore attract electron donors (Lewis bases) to fill the gap. Caputo et al. (p. 1374 ; see the Perspective by Gabbaï ) now show that a class of 4-coordinate phosphonium salts can act as surprisingly potent Lewis acids, despite their electronic saturation. The phosphorus cations, bearing fluorine and fluorinated aromatic substituents, can sever an alkyl carbon-fluorine bond by pulling away its fluoride—a process rendered catalytic through the use of a silane acceptor.