Reversible dissociation of (Se6I2)(AsF6)(2) in SO2(I)

The dissociation of (Se6I2)(AsF6)(2) in SO2(1) has been investigated by Se- 77 NMR spectroscopy at -80 degreesC involving both a natural-abundance samp le as well as that containing selenium enriched in the Se-isotope (enrichme nt 92 %). In addition to the previously characterized cations Se6I22+, SeI3 +, 1,1,4.4-Se4I42+, Se-10(2+), Se-8(2+), and Se-4(2+), the NMR spectra of t he equilibrium solution exhibited additional resonances the assignment of w hich has been carried out by Se-77-Se-77 COSY, selective irradiation experi ments, and spectral simulation. Combining this information with the trends in the chemical shifts as well as with iodine, selenium, and charge balance s that were calculated from quantitative integrated intensities, the presen ce of cyclic cations Se7I+ and 1,4-Se7I22+, as well as acyclic Se2I+, anti 1,1,6,6-Se6I42+(two rotamers) could be inferred. Upon evaporation of the so lvent only Se6I22+ was found to be present in the solid state.