Solvent-free photochemical decomposition of sulfur hexafluoride by phosphines: formation of difluorophosphoranes as versatile fluorination reagents

The chemical activation of SF6 has garnered considerable attention because of its possible utilization as a cheap and safe reagent in chemical synthesis. Such a process becomes particularly attractive when combined with the disposal of the potent greenhouse gas after its technical application. Herein, we report on the photochemical reaction of SF6 with phosphines, which selectively produces difluorophosphoranes and phosphine sulfides. Computational and experimental studies show that the pi(Ar) -> sigma*(SF6) charge-transfer excitation of a preformed R3PMIDLINE HORIZONTAL ELLIPSISSF6 complex is the initial activation step. Using triphenylphosphine, the decomposition of SF6 was carried out in a solvent-free, scalable process, giving a 3 : 1 mixture of difluorotriphenylphosphorane and triphenylphosphine sulfide (TPP-Fluor), which was utilized for the deoxyfluorination of alcohols and carboxylic acids and for the preparation of common hexafluorophosphate salts.