Stabilization of the Pentazolate Anion in Three Anhydrous and Metal‐Free Energetic Salts

According to previous reports, metal cations or water molecules are necessary for the stabilization of pentazolate anion (cyclo‐N5−) at ambient temperature and pressure. Seeking a new method to stabilize N5− is a big challenge. In this work, three anhydrous, metal‐free energetic salts based on cyclo‐N5− 3,9‐diamino‐6,7‐dihydro‐5 H‐bis([1,2,4]triazolo)[4,3‐e:3′,4′‐g][1,2,4,5] tetrazepine‐2,10‐diium, N‐carbamoylguanidinium, and oxalohydrazinium (oxahy+) pentazolate were synthesized and isolated. All salts were characterized by elemental analysis, IR spectroscopy, 1H, 13C, and (in some cases) 15N NMR spectroscopy, thermal analysis (TGA and DSC), and single‐crystal XRD analysis. Computational studies associated with heats of formation and detonation performance were performed by using Gaussian 09 and Explo5 programs, respectively. The sensitivity of the salts towards impact and friction was determined, and overall the real N5 explosives showed promising energetic properties. They come with a bang! Three nitrogen‐rich ionic derivatives of pentazolate anion (cyclo‐N5−) 3,9‐diamino‐6,7‐dihydro‐5 H‐bis([1,2,4]triazolo)[4,3‐e:3′,4′‐g][1,2,4,5]tetrazepine‐2,10‐diium, N‐carbamoylguanidinium, and oxalohydrazinium (oxahy+) pentazolate were synthesized and fully characterized. Single‐crystal X‐ray structure analyses revealed the stabilization mechanism of the cyclo‐N5− in anhydrous, metal‐free solid phase. Their physicochemical and energetic properties have also been studied.