PREPARATIONS, X-RAY CRYSTAL-STRUCTURES, AND FT-RAMAN SPECTRA OF M3CL3ASF6 (M=S, SE) CONTAINING THE NOVEL SULFUR-CHLORINE AND SELENIUM-CHLORINE CATIONS CIS+(CL)SSCL AND CLSE+(CL)SESECL

During the past decade we have discovered the rich chemistry of the su lfur/selenium iodine and sulfur/selenium bromine cations, examples of which include S7I+, (S7I)2I3+, M2I4(2+), 1 (Se6I+)n, Se6I2(2+),S7Br+, Se2Br5+, and M3Br3+2(M = S,Se)3. These cations maximize positive charg e delocalization giving rise to thermodynamically stable pi bonds and have in many cases cluster-like geometries.3 In contrast, except for M Cl3+ (M = S, Se),4,5 the only example of a sulfur/selenium chlorine ca tion to be unambiguously characterized is Se9Cl+,6 although Raman evid ence has been presented for the unstable S7Cl+ cation.7 In addition, S 2Cl3+ and Se2Cl3+ have been claimed in solution8a and SCl+ has been cl aimed in the solid state.8b The evidence suggested that lower sulfur a nd selenium/chlorine cations were less stable than their bromo and iod o analogues and might only exist as reactive intermediates. However, w e have succeeded in preparing S3-Cl3AsF6 and Se3Cl3AsF6, containing th e first example of M3Cl3+ cations, by the reaction of MCl3AsF6 and M ( M = S, Se) using sulfur dioxide as solvent. The syntheses and the char acterizations of these cations are the subject of this brief communica tion. The salt Se3Cl3AsF6 was prepared according to eq 1 by the reacti on of SeCl3AsF6 (0.466 g, 1.24 mmol) and selenium (0.197 g, 2.44 mmol) in liquid sulfur dioxide, SO2 (5.67 g), in a two-bulb glass vessel.9 After 6 h of stirring at room temperature, addition of sulfuryl chlori de fluoride, SO2ClF (0.8 g), and slow removal Reactions of stoichiomet ric quantities of SCl3AsF6 and sulfur, or SeCl3AsF6 and selenium, in l iquid sulfur dioxide lead to the quantitative syntheses of crystalline ClM+(Cl)MMCl(AsF6-) (M = S, Se), containing the first M3Cl3+ cations. The compounds were characterized by single-crystal X-ray diffraction and FT-Raman spectroscopy.