Interaction of hexafluorosilicic acid with sulfa drugs. Bis(sulfathiazolium) hexafluorosilicate: Spectral data and crystal structure

Interaction of hexafluorosilicic acid with sulfa drugs sulfathiazole (stz) and sulfalen (2-sulfanilamido-3-methoxypyrazine, sl) results in the crystalline salts of the compositions [stzH]2[SiF6] (I) and [4-H2NO2SPhNH3]2[SiF6] (II). Complex I is characterized by IR, mass spectrometry data and single crystal X-ray diffraction. The crystal structure of I is stabilized by a network of charge-assisted hydrogen bonding. The relationship between the solubility and H-bonding system in I, II and related “onium” hexafluorosilicates is discussed. The formation of complex II, previously reported as an interaction product of hexafluorosilicic acid with 4-aminobenzenesulfonamide (sulfanilamide), is the result of cleavage of the C–N bond in sulfalen in acidic medium.