Axially Chiral, Electrophilic Fluorophosphonium Cations: Synthesis, Lewis Acidity, and Reactivity in the Hydrosilylation of Ketones

Axially chiral [(C₆F₅)₃PF]­[B­(C₆F₅)₄] analogues based on dihydrophosphepines with a binaphthyl backbone were prepared and structurally characterized by X-ray diffraction analysis. Computational calculations of FIA and GEI values attest that these new fluorophosphonium cations have a higher Lewis acidity compared to the ubiquitous B­(C₆F₅)₃. Furthermore, application of these highly electrophilic compounds in the catalytic hydrosilylation of ketones and an investigation of the mechanism lead to a refined picture of the role of highly electrophilic fluorophosphonium cations.