Contributions to bis(perfluoroalkyl) chalkogenide chemistry: preparation of (R-f)(2)SeO [R-f = C2F5, (CF3)(2)CF, n-C(4)F9], (R-f ')(2)TeX2 [X = F, Cl: R-f ' = n-C3F7, (CF3)(2)CF, n-C4F9; X = Br: R-f ' = n-C3F7, n-C4F9], (CF3)(2)Te(NSO)(2) and (C2F5)(2)Te(OH)NO3

The reaction between perfluoroalkyl iodides with a threefold excess of a 1 : 1 molar mixture of Se and Cu is a new method for the preparation of corre sponding monoselenides (la-c) and diselenides (2a-d). They are oxidised wit h HOF without a solvent to bis(perfluoroalkyl) selenium(IV) oxides (3a-d). Halogenation of (R-f)(2)Te with XeF2, Cl-2 or Br-2 yielded (R-f)(2)TeF2(7a- c), (R-f)(2)TeCl2 (8a-c) and (R-f')(2)TeBr2 (9a, 9c). Oxidation of (C2F5)(2 )Te with cone. HNO3 gave (C2F5)(2)TeCOH)NO3 (4). When (CF3)(2)TeCl2 is trea ted with AgNSO metathesis took place forming (CF3)(2)Te(NSO)(2), (6). Two ( C6F5)(2)Te(VI) derivatives with the general formula (C6F5)(2)TeX4. with X = CF3C(O)O (5) and F are made from (C6F5)(2)TeO2 and CF3C(O)OH or SP4, respe ctively. The monotelluride (n-C6F13)(2)Te was synthesised similarly from n- C6F13I, Te and Cu. X-ray structures for 3d, 8a, and 8b are provided. (C) 20 00 Elsevier Science S.A. All rights reserved.