S8(AsF6)2 reacts with C2F4 in SO2 to form (C2F5)2Sx (x = 2 → 6), C2F5SXCF2C(O)F (x = 2 → 5), Sx(CF2C(O)F)2 (x = 2 → 4), CF3SxCF2C(O)F (x = 3, 4), CF3SxC2F5 (x = 3 → 5), and (CF3)2S3. Solid S8(AsF6)2 reacts with C3F6 to form (C3F7)2Sx (x = 2 → 5). In SO2 solution, the same reactants yield the additional products[Formula: see text]and related species incorporating the C(O)F moiety. Solid S4(Sb2F11)2 reacts with C2F4 to yield (C2F5)2Sx (x = 1 → 4),[Formula: see text]and with C3F6 to give (C3F7)2Sx(x = 1 → 3), and[Formula: see text]Solid Se4(AsF6)2 reacts with C2F4 to form (C2F5)2Sex(x = 1 → 3) and in SO2 solution, the species C2F5Se2CF2C(O)F, Se2(CF2C(O)F)2, CF3Se2CF2C(O)F, C2F5Se2CF3, and CF3Se2CF3 are also formed.Products were identified by mass spectroscopy and the major species were isolated by vpc and further characterized by 19F nmr. The mechanisms of these reactions are discussed.