Energetic High-Nitrogen Compounds: 5‑(Trinitromethyl)‑2H‑tetrazole and -tetrazolates, Preparation, Characterization, and Conversion into 5‑(Dinitromethyl)tetrazoles

A convenient access to 5-(trinitromethyl)-2H-tetrazole (HTNTz) has been developed, based on the exhaustive nitration of 1H-tetrazole-5-acetic acid, which was prepared from ethyl cyanoacetate and HN3 in a 1,3-dipolar cycloaddition reaction, followed by basic hydrolysis. HTNTz was converted into the ammonium, guanidinium, rubidium, cesium, copper, and silver 5-(trinitromethyl)-2H-tetrazolates. In addition, the ammonia adducts of the copper and silver salts were isolated. The reaction of HTNTz with hydrazine and hydroxylamine resulted in the formation of hydrazinium 5-(dinitromethyl)­tetrazolate and hydroxylammonium 5-(dinitromethyl)-1H-tetrazolate, respectively. Acid treatment of both 5-(dinitromethyl)­tetrazolates resulted in the isolation of 5-(dinitromethylene)-4,5-dihydro-1H-tetrazole, which was converted into potassium 5-(dinitromethyl)-1H-tetrazolate by reaction with K2CO3. All prepared compounds were fully characterized by 1H, 13C, 14N, and 15N NMR spectroscopy and X-ray crystal structure determination. Initial safety testing (impact, friction, and electrostatic sensitivity) and thermal stability measurements (differential thermal analysis, DTA) were also carried out. The 5-(trinitromethyl) and 5-(dinitromethyl)­tetrazoles are highly energetic materials that explode upon impact or heating.