Pentafluorophenyl-bis(pentafluorophenylthio)sulfonium hexafluoroarsenate, [(C6F5S)2SC6F5][AsF6], was prepared by the reaction of (C6F5)2S2 and AsF5 in liquid SO2 at room temperature. The compound has been characterized by single-crystal X-ray and powder diffraction, and IR and FT-Raman spectroscopy. Crystals of [(C6F5S)2SC6F5][AsF6] are orthorhombic, space group P212121 (cell dimensions measured at room temperature in brackets): a = 13.132(3) [13.157(2)] Å, b = 21.477(4) [21.575(3)] Å, c = 8.770(2) [8.775(1)] Å, α = ß = γ = 90.00°; V = 2473.3(9) Å3, Z = 4, temperature = 181 ± 1 K. The structure consists of [AsF6]- anions and [(C6F5S)2SC6F5]+ cations that have a different structure than the related [X2MMMX]+ cations (M = S, Se; X = Cl, Br), which contain a trichalcogen chain with a pronounced chalcogen-chalcogen bond alternation. Ab initio calculations suggest the observed [(C6F5S)2SC6F5]+ geometry is due to steric and solid state effects. Comparison of the Raman spectra of [(C6F5)S2SC6F5][AsF6], [Cl2SSSCl][AsF6], and [(CH3)2ClS3]+ implies that [(CH3)2ClS3]+ has a structure with equal sulfur-sulfur distances, and therefore the structure is likely [(CH3S)2SCl]+ and probably not the previously reported [(CH3)2SSSCl]+.Key words: [R3X3]+ cations, X-ray crystal structure, FT-Raman spectroscopy, [(C6F5S)2SC6F5]+, pentafluorophenyl-bis(pentafluorophenylthio)sulfonium cation, hexafluoroarsenate.
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