Abstract
Reactions of AF (A = K, Rb, Tl) with excess liquid SbF~5~ in anhydrous HF (or SO~2~) at room temperature give products having the composition ASb~2~F~11~. The reaction between CsF and a small excess of SbF~5~ in anhydrous HF (0.76 mmol of CsF + 4.19 mmol of SbF~5~ in 4 mL of aHF) yields CsSb~2~F~11~, whereas the reaction with a large excess of SbF~5~ (0.79 mmol of CsF + 23 mmol of SbF~5~ in 10 mLof aHF) yields the salt CsSb~3~F~16~. Efforts to prepare similar compounds using the monofluorides of Li and Na led only to the already known ASbF~6~ compounds. Reactions of AF (A = Na, K, Rb, Cs) with liquid SbF~5~ at 85 °C in the absence of solvents yield the products NaSbF~6~, ASb~2~F~11~ (A = K, Rb) and CsSb~3~F~16~, respectively. A single‐crystal X‐ray diffraction study on the salt KSb~2~F~11~ [orthorhombic, at 250 K, Pbca, with a = 1141.65(8), b = 1279.96(9), c = 3948.5(3) pm, V = 5.7699(7) nm^3^ and Z = 24] has shown it to be isostructural with AgSb~2~F~11~. CsSb~2~F~11~, on the other hand, is monoclinic at 250 K [__P__2~1~/n, with a = 774.10(14), b = 1425.41(17)m, c = 951.30(15) pm, β = 113.226(6)°, V = 0.9646(3) nm^3^ and Z = 4]. RbSb~2~F~11~ and TlSb~2~F~11~ belong to yet a third structural type. Crystals of CsSb~3~F~16~ are orthorhombic at 200 K [Pca__2~1~, with a = 2207(3), b = 772.6(11), c = 1605(3) pm, V = 2.737(8) nm^3^ and Z = 8]. The vibrational spectra of Sb~2~F~11~^–^ salts are consistent with the above crystallographic assignments, showing that Sb~2~F~11~^–^ anions deviate strongly from D~4__h~ symmetry in having no symmetry at all (point group C~1~). The vibrational spectra of CsSb~3~F~16~ confirm the presence of Sb~3~F~16~^–^ anions, which adopt a cis‐fluorine‐bridged geometry consistent with the crystal structure.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)