Functionalized Fluorophosphonium Ions.

Efforts to prepare an elusive donor-free phosphenium ion, [R2 P]+ , led us to synthesize functionalized fluorophosphonium cations of the type [R2 P(F)X]+ (X=SiEt3 , H, F), which were obtained from the related neutral fluorophosphines R2 PF and R2 PF3 upon protonation and reaction with solvated [Et3 Si]+ ions (R=2,6-Mes2 C6 H3 ). The hypothetical reductive elimination of [R2 P(F)SiEt3 ]+ and [R2 P(F)H]+ affording [R2 P]+ , Et3 SiF and HF, respectively, was calculated to be endothermic by 40.1 and 190.6 kJ mol-1 .