Halides of Hexavalent Chalcogens

It has not been possible yet to prepare chalcogen(VI) hexahalides with the heavy halogens. The chemistry of hexavalent chalcogen compounds with bonds to chlorine, bromine, and iodine is essentially restricted to the mixed-ligand molecules SCIF5, SBrFs, SeClFs, TeClFs, TeBrFs, and derivatives thereof. By far the largest proportion of published papers refers to the sulfur compounds. 

SCIF5 and SBrFs are important in organic synthesis because they add to a variety of olefins in a simileur manner as the sulfenide halides. 

SeClFs is prepared together with SeF4 and CI2 from the reaction of SeF4 with CIF at 350°C in an autoclave 74,400) or in high yield from the reaction 400) 

TeClFs and the rather unstable TeBrFs have been prepared in low yield by the reaction of F2, diluted with N2, with TeCU or TeBr4 at 25°C (242). Another convenient method condenses CIF onto TeF4, TeCU, or Te02 and warms the reaction mixture to room temperature (270). From NMR spectra (57) and the analysis of the microwave spectrum (272) a C4V structure was proposed, and from the vibrational spectrum a detailed normal coordinate analysis was undertaken (57). TeClFs is also formed if TeBrFs is reacted photochemically with CI2, which also converts PF3 to PCI2F3 and PCIF4. Both TeClFs and TeBrFs undergo photochemical reactions with olefins at 25°C (242). 

Bersuker, I. B., The Jahn-Teller Effect and Vibronic Interactions in Modem Chemistry. Plenum Press, New York and London, 1984. 

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