Review of the Current Synthesis and Properties of Energetic Pentazolate and Derivatives Thereof

The latest member of the azole family, the pentazolate or cyclo-N-5-, has received increased attention since its first mass-spectral detection by Christe et al. in 2002. As it is carbon- and hydrogen-free, the pentazolate anion can release large amounts of energy while simultaneously decomposing to environmentally friendly nitrogen gas. Due to these attractive qualities, cyclo-N-5- and related compounds are essential in the advancement of high-energy-density materials (HEDMs) research. This review aims to provide a consolidated report on all research done on cyclo-N-5-, with a focus on pentazoles as energetic materials and on their experimental synthesis. Included in this review are the following: (1) the historical significance of cyclo-N-5-; (2) precursors of cyclo-N-5-; (3) synthesis routes of cyclo-N-5- with a focus on arylpentazole precursors; (4) factors affecting the stability of cyclo-N-5-; (5) energetic performances of current energetic cyclo-N-5- -containing compounds; and (6) future possible experimental research. This review is a comprehensive summary of the current understanding of cyclo-N-5-, in an effort to further understand the potential of this anion for adoption as a powerful and environmentally friendly next-generation explosive. (C) 2020 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company.