Hydrogen Bonding Network: Stabilization of the Pentazolate Anion in Two Nonmetallic Energetic Salts

Pentazolate anion (cyclo-N5–) containing compounds have attracted wide interest in recent years. In this work, we report the new syntheses, single-crystal structures, and thermal stabilities of two nonmetallic salts (C4H9N10+)­(N5–)·3H2O (4) and (C5H9N10+)2(Cl–)­(N5–)·3.5H2O (5). Single crystal X-ray diffraction shows that compounds 4 and 5 have layer-by-layer stacking and three-dimensional (3D) structures constructed of hydrogen bonding networks, in which the 2D and 3D hydrogen bonding networks are formed to stabilize cyclo-N5– anions. The two cyclo-N5– salts are stable at room temperature and thermal analyses indicate their onset decomposition temperatures of 95.35 °C for 4 and 98.52 °C for 5. Hirshfeld surface analyses showed that the following factors could improve the thermal stability of cyclo-N5–: NH···N hydrogen bonds are better than OH···N hydrogen bonds; 3D hydrogen bonding network is superior to 2D hydrogen bonding network. These findings will enhance the future prospects for the design and synthesis of cyclo-N5– containing energetic salts