Synthesis and structure of fluorosilicic acid compounds with 4-aminobenzoic acid and with 4-aminobenzenesulfonamide: The role of H-bonding in crystal structure formation

Preparation and characterization of the ammonium hexafluorosilicate salts, 2[R]+[SiF6]2− (R = 4-(aminosulfonyl)benzenammonium) (1), and 2[R]+[SiF6]2−.4H2O (R = 4-carboxybenzenammonium), (2), are described. These salts, prepared from the reaction of the 4-aminobenzenesulfonamide or the 4-aminobenzoic acid with fluorosilicic acid, were characterized by IR, mass spectrometry and X-ray diffraction. 1 and 2 crystallize in monoclinic crystal system (space group P21/c and P21/n, respectively), with Z = 2 in both cases. Compounds exhibit an extensive system of hydrogen bonding.