The Protonation of HSO 3 F: Preparation and Characterization of Fluorodihydroxyoxosulfonium Hexafluoroantimonate [H 2 SO 3 F] + [SbF 6 ] −

Sulfurtrioxide reacts with the superacidic solutions XF/SbF 5 (X=H, D) to form the corresponding salts [X 2 SO 3 F] + [SbF 6 ] − , which are the protonated forms of fluorosulfuric acid. The salts have been characterized by vibrational spectroscopy and a single‐crystal structure analysis. [H 2 SO 3 F] + [SbF 6 ] − crystallizes in the monoclinic space group P 2 1 / n (no. 14) with four formula units in the unit cell. The crystal structure possesses a distorted tetrahedral O 3 SF skeleton of the cations, which are linked with two strong hydrogen bridges to [SbF 6 ] − anions and forms a one‐dimensional chain. The crystal structure and the vibrational spectra are compared to the quantum‐chemical‐calculated free [H 2 SO 3 F] + cation. Additionally, an [H 2 SO 3 F(HF) 2 ] + unit was calculated at the RHF/6‐311 ++ G(d,p) level to simulate H⋅⋅⋅F hydrogen bridges found in the solid state.