Syntheses and reactions of fluoroorganic acyclic thiocarbenium ions.
Arsenic pentafluoride oxidizes (F3CS)4C (1) but not (F3CS)2C:C(SCF3)2 (2) to yield the stable salt (F3CS)3C+ AsF6- (3). It reacts with halide ions to form (F3CS)3CX (3a-c, X = F, Cl, Br). Iodide is oxidized to iodine with formation of (F3CS)3CC(SCF3)3 (4) which reacts with nitrogen dioxide to give (F3CS)3CNO2 (3e). (F3CS)3C+ ASF6- (3) removes from 2,2,4-trifluoro-4-(trifluoromethylthio)-1,3-dithietane (5a) a ring-bound fluorine atom to afford (F3CS)3CF and 2,2-difluoro-4-(trifluoromethylthio)-1,3-dithietane hexafluoroarsenate (5). When (F3CS)3CCl (3b) is treated with AsF5, 3 and [(F3CS)2CCl]+ AsF6- (6) are formed in a 2:1 molar ratio. The latter reacts with F- or Cl- to give (F3CS)2CClX (6a,b; X = F, Cl). AsF5 is capable of abstracting a fluoride ion from (F3CS)3-nClnCF only if n = 0 or 1. For n = 2 no similar reaction takes place, but with AlCl3 in BCl3 halogen exchange to F3CSCCl3 (7b) is obsd. Alkylation of (F3CS)2C:S (8) with HCF/AsF5 yields [(F3CS)2CSCH3]+ AsF6- (9), which adds a fluoride ion to give (F3CS)2(H3CS)CF (9a). The mol. structures of (F3CS)2C:C(SCF3)2 (2) and (F3CS)3CC(SCF3)3 (4) have been detd. by x-ray diffraction methods.
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