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.

Oxalic acid forms in superacidic solutions HF/MF5 (M = As, Sb) its corresponding mono‐ and diprotonated salts [HOOCC(OH)2][MF6] and [(HO)2CC(OH)2][MF6]2 (M = As, Sb). The number of protonations is strongly dependent on the stoichiometric ratio of the Lewis acid with regard to oxalic acid. Mono‐ and diprotonated salts were characterized by vibrational spectroscopy and in the case of [HOOCC(OH)2][AsF6] (1) and [(HO)2CC(OH)2][SbF6]2 (4) by a single‐crystal X‐ray structure analysis. The salts crystallize in the monoclinic space groups P21/c and P21/n with eight, respectively four, formula units per unit cell. The vibrational spectra were compared to quantum chemical calculations of the cations [HOOCC(OH)2]+ and [(OH)2CC(OH)2]2+⋅4HF. In addition to this, an MEP analysis together with the NPA charges of [(OH)2CC(OH)2]2+, [(OH)2CC(OH)2]2+⋅6HF and oxalic acid were calculated to locate the positive charge. The protonation of oxalic acid does not lead to a remarkable change of the C‐C bond length, which is discussed for the entire series of the oxalic skeleton, starting with the dianion and ending with the tetrahydroxy dication.

The homogeneous mixture of anhydrous hydrogen fluoride aHF and antimony pentafluoride AsF5 is known as a superacidic system. The high acidity is derived from the formation of [H2F](+) [AsF6](-). No experimental evidence exists for the existence of the free acid molecule HAsF6. The reaction of trimethylsilyl N,N-dimethylcarbamate in the binary system aHF/AsF5 led to decomposition of trimethylsilyl N,N-dimethylcarbamate at -50 °C to dimethylammonium hexafluoridoarsenate and cocrystallization of HAsF6. The single-crystal X-ray structure displays an HAsF6 molecule involved in an asymmetric hydrogen bridge to the hexafluoridoarsenate anion. As a result of the incalculable situation in the crystal lattice, the molecular structure of HAsF6 is calculated by quantum chemical structure optimization of the extreme cases of [FHF-AsF5](-) (strong hydrogen bond) and HAsF6 (no hydrogen bond) at the PBE1PBE/6-311G(3df,3pd) level of theory.

Acetamide and thioacetamide react with the superacid solutions HF/MF 5 (M = As, Sb) under formation of the corresponding salts [H 3 CC(OH)NH 2 ] + MF 6 and [H 3 CC(SH)NH 2 ] + MF 6 -(M = As, Sb), respectively. The reaction of DF/AsF 5 with acetamide and thioacetamide lead to the corresponding deuterated salts [H 3 CC(OD)ND 2 ] + AsF 6 and [H 3 CC(SD)ND 2 ] + AsF 6 -, respectively . The salts are characterized by vibrational and NMR spectroscopy, and in the case of [H 3 CC(OH)NH 2 ] + AsF 6 and [H 3 CC(SH)NH 2 ] + AsF 6 also by singlecrystal X-ray analyses. The [H 3 CC(OH)NH 2 ] + AsF 6 -(1) salt crys-* Prof. Dr. A. Kornath

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 .