Synthesis, characterization, and comparison of explosive hexaamminecobalt(III) and nitropentamminecobalt(III) cyclopentazolate (cyclo‐N5−) salts

Abstract

AbstractMetal pentazolate hydrates have attracted attention because of the unique stabilization mechanisms of cyclo‐N5− anions during crystal stacking. However, coordinated H2O molecules influence the stability of cyclo‐N5− anion‐containing salts, and the structure‐property relationship of high‐valent cobalt pentazolate salts has not been previously reported. Werner‐type cobalt(III) cations that trap cyclo‐N5− anions, a novel class of cyclo‐N5−‐based materials, were prepared and characterized by infrared spectroscopy, elemental analysis, electrospray ionization mass spectrometry, and thermogravimetry with differential scanning calorimetry. The [Co(NH3)5(NO2)]2+ cation was also introduced via metathesis reactions to compare the intermolecular interactions in its intriguing structures. Single‐crystal X‐ray diffraction revealed extensive hydrogen bonding networks in hexaamminecobalt(III) and nitropentamminecobalt(III) cyclo‐N5− salts between cyclo‐N5− anions and NH3 ligands or nitro groups. In addition, [Co(NH3)6(N5)3] (1) and [Co(NH3)5(NO2)](N5)2 (2) exhibited relatively high nitrogen contents of 79.2 % and 67.9 %, respectively, and the impact sensitivities of 1 (IS=5 J) and 2 (IS=4 J) are comparable to that of lead azide.