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 cheap and safe reagent in chemical synthesis. Such a process becomes particularly attractive when combined...

Activation of SF5CF3 by the N-Heterocyclic Carbene SIMes

“…Analytical data for 11 : 31 P NMR (121.5 MHz, C 6 D 6 ): δ = 42.28 (s)., ESI-MS (CD 3 CN): calculated ( m / z ) for [11 + 2Na + + H − ] + : 341.05, experimental ( m / z ) for [11 + 2Na + + H − ] + : 341.05. The obtained NMR data are consistent with those in the literature [ 13 , 23 ].…”

“…For the thermal activation of SF 5 CF 3 , a comparable transformation can be imagined, although electron transfer can be hampered by a kinetic barrier. In this regard, an incipient transition state or pre-interaction of the nucleophilic carbene with SF 5 CF 3 seems to be conceivable [ 8 , 23 , 38 , 39 ]. It should be noted that an ion flow tube study shows that OH − reacts with SF 5 CF 3 , yielding CF 3 OH and SF 5 − [ 40 ].…”

“…Irradiation at a wavelength of 375 nm led to the formation of only small amounts of phosphorane 12, and only traces of α,α,α-trifluorotoluene-d 5 . No thermal activation of SF 5 CF 3 in toluene- d 8 could be achieved via heating the reaction solution at 100 °C for 9 h. Notably, Buß et al reported on the thermal activation of SF 6 using strongly basic phosphines [ 8 ], but could not observe the thermal activation of SF 6 with PPh 3 , due to the lower nucleophilicity of the latter [ 23 ].…”

“…The CF 3 radical reacts with the solvent C 6 D 6 , yielding α,α,α-trifluorotoluene-d 5 and, presumably, DF, possibly via the re-oxidation of a cyclohexadienyl radical cation with PPh 3 + , and subsequent deprotonation with fluoride . It should be noted that Dielmann et al also proposed, for the photochemical activation of SF 6 with triphenylphosphine, a mechanism based on DFT calculations, in which an electron is initially transferred from a π orbital of an arene moiety of PPh 3 to the delocalized σ* orbital of SF 6 [ 23 ].…”

“…Rotering et al demonstrated that triphenylphosphine can be utilized to activate SF 6 under irradiation to yield Ph 3 PF 2 and Ph 3 P=S in a ratio of 3:1. The latter mixture was used in situ for the deoxyfluorination of carboxylic acids [ 23 ]. For both processes, SF 6 was presumably initially reduced to give SF 6 − .…”