Crystal structure, vibrational and theoretical studies of bis(4-amino-1,2,4-triazolium) hexachloridostannate(IV)

X-ray structure of new hybrid organic–inorganic compound, bis(4-amino-1,2,4-triazolium) hexachloridostannate(IV), [1t(4at)]2SnCl6 (P  1¯ space group) was determined. Crystal structure of 4-amino-1,2,4-triazole (Pbca space group) was reinvestigated. Non-planar orientation of NH2 group was found. The geometry of the amino group does not significantly change upon protonation. The route of protonation of 4-aminotriazole and tautomer equilibrium constants for the cationic forms were theoretically studied by means of B3LYP/6-31G* method. The most stable monoprotonated species is 1H-trans-4-amino-1,2,4-triazole, 1t(4at)+, whereas the final product of the protonation route is 12(4at)2+. Potential Energy Distribution (PED) analysis was carried out for two conformers, 1c(4at)+ and 1t(4at)+. Very good agreement between theoretical and experimental frequencies was achieved due to very weak interactions existing in [1t(4at)]2SnCl6. Infrared and Raman bands were assigned on the basis of PED analysis. Comparison of vibrational spectra of [1t(4at)]2SnCl6 and [1t(4at)]Cl indicates significantly weaker intermolecular interactions in the former compound.

► X-ray structure of bis(4-amino-1,2,4-triazolium) hexachloridostannate was determined.
► Crystal structure of 4-amino-1,2,4-triazole was reinvestigated.
► Non-planar orientation of NH2 group was found.
► Route of protonation of 4at was theoretically studied.
► Weak interactions in the crystal structure allowed exact theoretical reproduction of vibrational spectra.