Trifluoromethanesulfonic anhydride reacts with superacidic solutions AF/SbF5 (A = H, D) to form their corresponding salts CF3SO3A2+SbF6–, which are protonated forms of trifluoromethanesulfonic acid and CF3SO2F as by‐product. The salts have been characterized by vibrational spectroscopy and single‐crystal structural analysis. CF3SO3H2+SbF6– crystallizes in the triclinic space group P$\bar {1}$ with two formula units in the unit cell: a = 709.29(5) pm, b = 763.46(5) pm, c = 882.15(6) pm; α = 71.884(6)°, β = 72.488(6)°, γ = 84.509(6)°; V = 432.97(5) Å3. The cations are linked with two strong hydrogen bonds to SbF6– anions to form chains. The experimental data were also compared to quantum chemical calculations for the CF3SO3H2(HF)2+ cation.

The reactions of acetonitrile, propionitrile, butyronitrile, N,N-dimethylaminoacetonitrile, benzonitrile, o-tolunitrile and 1,4-dicyanobenzene with HF/AsF5 or HF/SbF5 in anhydrous HF result in protonation of the nitrile. The obtained nitrilium ions were isolated as [AsF6](-), [SbF6](-) and [Sb2F11](-) salts and characterized by multinuclear NMR and vibrational spectroscopy, and their X-ray crystal structures.

Trimethylsilylcyanide reacts with superacidic solutions AF/MF 5 (A = H, D; M = As, Sb) to form their corresponding salts [ACNA] + [MF 6 ] À , which are protonated forms of hydrogen cyanide and Me 3 SiF as by-product. The salts have been characterized by vibrational spectroscopy and a single-crystal X-ray structure analysis.[DCND] + [AsF 6 ] À crystallizes in the triclinic space group P-1 with one formula unit in the unit cell. The disordered cations are linked with two strong hydrogen bonds to [SbF 6 ] À anions to form chains. The crystal structure and the vibrational spectra are compared to the quantum-chemically calculated (PBE1PBE/6-311 + +G(3df,3dp)) [HCNH(HF) 2 ] + and [DCND (HF) 2 ] + units which simulate the H···F hydrogen bridges found in the solid state. The vibrational modes of the [DCND] + cation are strongly mixed. For their discussion 13 C and 15 N isotopomers have been prepared by the reaction of KCN isotopomers with the superacidic solution AF/AsF 5 .

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 P2(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 HF hydrogen bridges found in the solid state.