Base-promoted decarboxylative gem-diazo-C-coupling: Synthesis, characterization and performance of nitrotriazolylformazans

Formazans, containing the characteristic chain of atoms –NN-CRN–NH- (R ​= ​–CN or tetrazyl) are nitrogen-rich and conjugated compounds exhibiting unique properties. In this work, new cyano and tetrazylformazans and their series of nitrogen-rich energetic salts were synthesized via base-promoted gem-diazo coupling reaction. The resulting derivatives were well characterized, and their performances were further investigated. The experimental results indicated that the decomposition temperatures of 1–12 lie between 159 ​°C and 279 ​°C. All of them are much less impact sensitive (≥20 ​J) than trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). They have relatively high positive heats of formation between 987.7 and 1457.3 ​kJ ​mol-1, which are much higher than those of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), RDX and HMX. The calculated detonation pressures (p) range between 23.2 and 30.2 ​GPa and calculated detonation velocities (D) between 7480 and 8274 ​m ​s-1. Interestingly, compound 4 shows excellent laser ignition combustion performance.