School of Chemical Engineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing 210094, Jiangsu, China.
Chem Soc Rev. 2018 Oct 15;47(20):7522-7538. doi: 10.1039/c8cs00372f.
The pentazolate anion, or cyclo-N5-, which is a five-membered ring composed solely of nitrogen atoms, has a unique structure among polynitrogen compounds. Cyclo-N5- is receiving ever-increasing levels of attention because of its potential ability to store large amounts of energy compared to the azide ion, its environmentally friendly decomposition products, and its carbon- and hydrogen-free composition, which are promising characteristics for advancing the field of high-energy-density materials (HEDMs), that include explosives, oxidisers, and propellants in closed environments. In this review, we provide a detailed introduction to cyclo-N5- and cover the following topics: (1) substituted pentazoles as precursors of cyclo-N5-, with a focus on the syntheses and stabilities of substituted pentazole derivatives; (2) routes to cyclo-N5- through cleavage of C-N bonds in substituted pentazoles, during which competitive reactions between pentazole decomposition and C-N bond cleavage need to be considered to ensure a successful outcome; (3) complexes of cyclo-N5-, summarising recent progress toward producing cyclo-N5--based complexes through the assembly of isolated cyclo-N5- with both metallic and nonmetallic components; and (4) interactions between cyclo-N5- and metal cations and non-metal species, as well as factors that influence the stability of these complexes; in particular, the thermal stabilities of prepared cyclo-N5- salts are discussed. This review summarises recent studies and is intended to improve the understanding of polynitrogen chemistry while supporting further research into its potential application as an efficient, safe, and environmentally friendly HEDM.
五氮阴离子，或环-N5-，由纯氮原子组成的五元环，在多氮化合物中具有独特的结构。由于与叠氮离子相比，其潜在的储能能力、环境友好的分解产物以及无碳和无氢的组成，环-N5-正受到越来越多的关注，这是推进高能量密度材料（HEDM）领域的有前途的特性，包括爆炸物、氧化剂和推进剂在封闭环境中。在这篇综述中，我们详细介绍了环-N5-，并涵盖了以下主题：（1）作为环-N5-前体的取代五唑，重点介绍取代五唑衍生物的合成和稳定性；（2）通过取代五唑中 C-N 键的断裂制备环-N5-的途径，在此过程中需要考虑五唑分解和 C-N 键断裂之间的竞争反应，以确保成功；（3）环-N5-的配合物，总结了通过孤立的环-N5-与金属和非金属成分组装来制备基于环-N5-的配合物的最新进展；（4）环-N5-与金属阳离子和非金属物种的相互作用，以及影响这些配合物稳定性的因素；特别是，讨论了制备的环-N5-盐的热稳定性。这篇综述总结了最近的研究，旨在提高对多氮化学的理解，同时支持进一步研究其作为高效、安全和环境友好的 HEDM 的潜在应用。
