The crystal structure of potassium fluorosulphate

Abstract

Crystals of potassium fluorosulphate, KSO₃F, are orthorhombic, a= 8·62, b= 5·84, c= 7·35 Å, Z= 4, space-group Pnma. The structure was determined with three-dimensional Mo–K_α scintillation counter data by comparison with isostructural compounds, and refined by least-squares methods, the final R being 0·069 for 411 observed reflexions.

The fluorosulphate anion is arranged in the crystal in a disordered fashion, so that it has apparently C_2ν symmetry. On the assumption that the symmetry of the isolated anion is C_3ν, it is possible to derive the dimensions (after correction for rotational oscillation affects): S–O = 1·43 ± 0·01 Å, S–F = 1·58 ± 0·02 Å, ∠ O–S–O = 112·9°, ∠ F–S–O = 105·8°. These values are qualitatively consistent with 67% double-bond character for the S–O bonds, and with an S–F single bond. The crystal structure is similar to that of BaSO₄; the K⁺ ion has twelve oxygen and fluorine neighbours in the range 2·81–3·55 Å.