(Perfluoralkyl)(dimethylamino)sulfonium‐hexafluoroarsenate

(Perfluoroalkyl)(dimethylamino)sulfonium Hexafluoroarsenates MeN = S(CF 3 ) 2 ( 5 ) is alkylated by Me 3 O ⊕ AsF ⊖ 6 to Me 2 N‐S(CF 3 ) ⊕ 2 AsF ⊖ 6 ( 4 ). From 5 and MeOSO ⊕ AsF ⊖ 6 ( 6 ) MeOS(O)‐N(Me)S(CF 3 ) ⊕ 2 AsF ⊖ 6 ( 7 ) is formed as a relatively stable primary product. Decomposition of 7 gives the expected 4 only in poor yield. Nucleophilic substitution of the sulfur‐bonded fluorine in CF 3 SF ⊕ 2 AsF ⊖ 6 ( 8 ) by Me 3 SiNMe 2 yields CF 3 S(NMe 2 ) ⊕ 2 AsF ⊖ 6 ( 9 ). Similarly, (CF 3 ) 2 CFSF ⊕ 2 AsF ⊖ 6 ( 10 ) reacts with dimethyl(trimethylsilyl)amine to give (CF 3 ) 2 CFS(NMe 2 ) ⊕ 2 AsF ⊖ 6 ( 11 ). The structures of 4 and 9 are elucidated by X‐ray analyses, and the influence of the substituents on the bonding is discussed.