New energetic materials: functionalized 1-ethyl-5-aminotetrazoles and 1-ethyl-5-nitriminotetrazoles

Alkylation of 5-aminotetrazole (1) with 2-chloroethanol leads to a mixture of the N-1 and N-2 isomers of (2-hydroxyethyl)-5-aminotetrazole. Treatment of 1-(2-hydroxyethyl)-5-aminotetrazole (2) with SOCl(2) yielded 1-(2-chlorethyl)-5-aminotetrazole (3). 1-(2-Azidoethyl)-5-aminotetrazole (4) was generated by the reaction of 3 with sodium azide. Nitration of 2, 3, and 4 with HNO(3) (100%) yielded in the case of 2 and 3 1-(2-hydroxyethyl)-5-nitriminotetrazole (5) and 1-(2-chloroethyl)-5-nitriminotetrazole (6). In the case of 4, 1-(2-nitratoethyl)-5-nitriminotetrazole monohydrate (7) was obtained. 1-(2-Azidoethyl)-5-nitriminotetrazole (8) could be obtained by nitration of 4 with NO(2)BF(4) via the formation of potassium 1-(2-azidoethyl)-5-nitriminotetrazolate (9). The reaction of 6 with NaN(3) resulted in the formation of the salt sodium 1-(2-chloroethyl)-5-nitriminotetrazolate (10 a). The deprotonation reaction of 6 was further investigated by the formation of the ammonium salt (10 b). The protonation of 2 and 4 with dilute nitric acid led to 1-(2-hydroxyethyl)-5-aminotetrazolium nitrate (11) and 1-(2-azidoethyl)-5-aminotetrazolium nitrate (12), respectively. Similarly, protonation of 4 with perchloric acid led to 1-(2-azidoethyl)-5-aminotetrazolium perchlorate monohydrate (13). Since 5-nitrimino-tetrazoles can be used as bidentate ligands, the coordination abilities of 5, 6, and 8 were tested by the reaction with copper nitrate trihydrate, yielding the copper complexes trans-[diaquabis{1-(2-hydroxyethyl)-5-nitriminotetrazolato-kappa(2)N(4),O(5)}copper(II)] (14), trans-[diaquabis{1-(2-chloroethyl)-5-nitriminotetrazolato-kappa(2)N(4),O(5)}copper(II)] dihydrate (15), and [diaquabis{1-(2-azidoethyl)-5-nitriminotetrazolato-kappa(2)N(4),O(5)}copper(II)] (16). All compounds were characterized by low-temperature single-crystal X-ray diffraction. In addition, comprehensive characterization (IR, Raman, and multinuclear NMR spectroscopy ((1)H, (13)C), elemental analysis, mass spectrometry, DSC) was performed. The heats of formation of selected compounds were computed by using heats of combustion obtained by bomb calorimetry or calculated by the atomization method. With these values and the densities determined from X-ray crystallography, several detonation parameter were calculated by the EXPLO5 program. Finally, the sensitivities towards impact and friction were determined using a BAM drop hammer and friction tester.