Axially chiral [(C6F5)(3)PF][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.