Raman spectroscopy halogen cations

During the past 20 y numerous other highly coloured halogen cations have been characterized by Raman spectroscopy. X-ray crystallography, and other techniques, as summarized in Table 17.18. Typical preparative routes involve direct oxidation of the halogen (a) in the absence of solvent, (b) in a solvent which is itself the oxidant (e.g. AsFs) or (c) in a non-reactive solvent (e.g. SO2). Some examples are listed below ... 

Schrobilgen, Christe, and co-workers have recently carried out the first detailed structural characterization of the XF6+ cations (X = Cl, Br, I) as their SbjFj 1 salts.856 The XF6+ cations have octahedral geometries with average bond lengths of 1.550 A (Cl—F), 1.666 A (Br-F), and 1.779 A (I-F) measured at -130°C and -173°C. The cations have 13-16 interionic F—F contacts to the neighboring anions and six F—X contacts between the fluorine atoms of the anions and the central halogen atoms. Additional studies (NMR characterization of the central X atoms, Raman spectroscopy, and calculations) were also performed. 

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