0000000001284788
AUTHOR
Gary Schrobilgen
77Se NMR Spectroscopic, DFT MO, and VBT Investigations of the Reversible Dissociation of Solid (Se6I2)[AsF6]2•2SO2 in Liquid SO2 to Solutions Containing 1,4-Se6I22+ in Equilibrium with Sen2+ (n = 4, 8, 10) and Seven Binary Selenium Iodine Cations: Preliminary Evidence for 1,1,4,4-Se4Br42+ and cyclo-Se7Br+
The composition of a complex equilibrium mixture formed upon dissolution of (Se6I2)[AsF6]2·2SO2 in SO2(l) was studied by 77Se NMR spectroscopy at −70 °C with both natural-abundance and enriched 77Se-isotope samples (enrichment 92%). Both the natural-abundance and enriched NMR spectra showed the presence of previously known cations 1,4-Se6I22+, SeI3+, 1,1,4,4-Se4I42+, Se102+, Se82+, and Se42+. The structure and bonding in 1,4-Se6I22+ and 1,1,4,4-Se4I42+ were explored using DFT calculations. It was shown that the observed Se−Se bond alternation and presence of thermodynamically stable 4pπ−4pπ Se−Se and 4pπ−5pπ Se−I bonds arise from positive charge delocalization from the formally positively c…
NMR Spectroscopic Evidence for the Intermediacy of XeF3– in XeF2/F– Exchange, Attempted Syntheses and Thermochemistry of XeF3– Salts, and Theoretical Studies of the XeF3– Anion
The existence of the trifluoroxenate(II) anion, XeF3−, had been postulated in a prior NMR study of the exchange between fluoride ion and XeF2 in CH3CN solution. The enthalpy of activation for this exchange, ΔH⧧, has now been determined by use of single selective inversion 19F NMR spectroscopy to be 74.1 ± 5.0 kJ mol−1 (0.18 M) and 56.9 ± 6.7 kJ mol−1 (0.36 M) for equimolar amounts of [N(CH3)4][F] and XeF2 in CH3CN solvent. Although the XeF3− anion has been observed in the gas phase, attempts to prepare the Cs+ and N(CH3)4+ salts of XeF3− have been unsuccessful, and are attributed to the low fluoride ion affinity of XeF2 and fluoride ion solvation in CH3CN solution. The XeF3− anion would rep…