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

Abstract

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 π(Ar) → σ*(SF₆) charge-transfer excitation of a preformed R₃P⋯SF₆ 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.