The CN₇⁻ Anion

Several salts containing the CN₇⁻ anion were prepared by deprotonation of 5-azido-1H-tetrazole (1). The highly explosive compounds hydrazinium (2), ammonium (3), aminoguanidinium (4), guanidinium (5), lithium (6), sodium (7), potassium (8), cesium (9), and calcium (10) azidotetrazolate were characterized by low temperature single X-ray diffraction. Other analytic methods, such as IR and Raman spectroscopy, multinuclear NMR spectroscopy, mass spectrometry, and differential scanning calorimetry were performed when possible since some of the metal salts explode spontaneously. 2 contains the highest nitrogen content (87.48%) of all known tetrazole salts. The impact, friction, and electrical spark sensitivity of 2, 3, 4, and 5 were measured, resulting in values which belong to primary explosives. In addition, the heats of formation of 2, 3, and 4 were calculated using the CBS-4M level of quantum mechanical theory. These, in turn, were used to estimate detonation pressure p_C-J and velocity D_det as well as the specific impulse I_sp.