Pentazole (HN₅) and its anion pentazolate (cyclo-N₅^–) have intriguing structures and potential applications in ultrahigh-performing explosives, propellants, or pyrotechnics.

Yuangang Xu, Qiuhan Lin, Pengcheng Wang, and Ming Lu, Nanjing University of Science and Technology, China, have synthesized a series of 3D metal-inorganic frameworks (MIFs) based on pentazolate using self-assembly. They combined metal cations with pentazolate, azide (N₃^–), or nitrate (NO₃^–) anions in water at room temperature. The products, [Cu(N₅)(N₃)]_n, [Ag(N₅)]_n, [Ba(N₅)(NO₃)(H₂O)₃]_n, and [NaBa₃(N₅)₆(NO₃)(H₂O)₃]_n, were characterized using single-crystal X-ray diffraction, scanning electron microscopy (SEM), infrared (IR) and Raman spectroscopy, elemental analysis, and thermal analysis.

The team found that cyclo-N₅^– could be stabilized in anhydrous metal–N₅^– frameworks. The multi-ligand frameworks have decomposition temperatures of 98.2–173.4 °C. [Ag(N₅)]_n has enhanced detonation performances compared to previous cyclo-N₅^–-based frameworks. The syntheses could provide inspiration for the development of metal–pentazolate frameworks and polynitrogen chemistry.

• Syntheses, Crystal Structures and Properties of a Series of 3D Metal-Inorganic Frameworks Containing Pentazolate Anion,
  Yuangang Xu, Qiuhan Lin, Pengcheng Wang, Ming Lu,
  Chem. Asian J. 2018.
  https://doi.org/10.1002/asia.201800476