Crystals of the 1:2 adduct formed by BrF5 and SbF5 consist of infinite chains of discrete BrF4 + and Sb2Fn~ions coupled by relatively weak fluorine bridges and, accordingly, should be formulated as [BrF4+] [Sb2Fn-]. This is the first direct evidence for the existence of the BrF4+ ion. The crystals are monoclinic with the most probable space group P24/a, lattice constants a = 14.19 ± 0.03, b = 14.50 ± 0.03, c = 5.27 ± 0.01 Á, ß = 90.6 ± 0.1°, and four formula units per unit cell; the calculated density is 3.72 g cm-3. The structural parameters were refined by the method of least-squares with visually estimated Weissenberg photographic intensity data. The final value of the conventional agreement index R was 0.14 for 773 reflections having |F0| greater than (| ,|).

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The 1:l adducts between ClF, and the LEWIS acids BF,, PE;, AsF, and SbF, were ini-estigated. The existence of these complexes in the ionic form, in both the solid form and In solvents, such as JF5 and ClF,, was proven by I R , conductivity measurements, conductometric titration, and freezing point depression. It could be shown that the difluorochlorinium cation is bent and not linear.

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