Topic
Pentazole
About: Pentazole is a research topic. Over the lifetime, 110 publications have been published within this topic receiving 2883 citations.
Papers published on a yearly basis
Papers
TL;DR: Five metal pentazolate hydrate complexes are synthesized and characterized that exhibit good thermal stability with onset decomposition temperatures greater than 100 °C and the N5− ion can coordinate to the metal cation through either ionic or covalent interactions, and is stabilized through hydrogen-bonding interactions with water.
Abstract: Metal complexes of the pentazole anion exhibit multiple coordination modes, through ionic, covalent and hydrogen-bonding interactions, and good thermal stability with onset decomposition temperatures greater than 100 °C. Polynitrogen compounds can decompose to N2 with an extraordinarily large energy release, which makes them promising candidate materials for explosives but difficult to produce in a stable form. Compounds containing five-membered all-nitrogen rings have attracted particular interest in the search for a stable polynitrogen molecule. Yuangang Xu et al. report five metal complexes containing the pentazole anion, cyclo--N5−, four of which exhibit good thermal stability and a range of different bonding interactions for stabilization. Given their energetic properties and stability, and the adaptability of the cyclo-N5− species in terms of its bonding interactions, these complexes might lead to the development of a new class of high-energy-density materials and of other unusual polynitrogen complexes. Singly or doubly bonded polynitrogen compounds can decompose to dinitrogen (N2) with an extremely large energy release. This makes them attractive as potential explosives or propellants1,2,3, but also challenging to produce in a stable form. Polynitrogen materials containing nitrogen as the only element exist in the form of high-pressure polymeric phases4,5,6, but under ambient conditions even metastability is realized only in the presence of other elements that provide stabilization. An early example is the molecule phenylpentazole, with a five-membered all-nitrogen ring, which was first reported in the 1900s7 and characterized in the 1950s8,9. Salts containing the azide anion (N3−)10,11,12 or pentazenium cation (N5+)13 are also known, with compounds containing the pentazole anion, cyclo-N5−, a more recent addition14,15,16. Very recently, a bulk material containing this species was reported17 and then used to prepare the first example of a solid-state metal–N5 complex18. Here we report the synthesis and characterization of five metal pentazolate hydrate complexes [Na(H2O)(N5)]·2H2O, [M(H2O)4(N5)2]·4H2O (M = Mn, Fe and Co) and [Mg(H2O)6(N5)2]·4H2O that, with the exception of the Co complex, exhibit good thermal stability with onset decomposition temperatures greater than 100 °C. For this series we find that the N5− ion can coordinate to the metal cation through either ionic or covalent interactions, and is stabilized through hydrogen-bonding interactions with water. Given their energetic properties and stability, pentazole–metal complexes might potentially serve as a new class of high-energy density materials19 or enable the development of such materials containing only nitrogen20,21,22,23. We also anticipate that the adaptability of the N5− ion in terms of its bonding interactions will enable the exploration of inorganic nitrogen analogues of metallocenes24 and other unusual polynitrogen complexes.
399 citations
TL;DR: The increment scheme also provides estimates of the strain energies of polynitrogen compounds, e.g., tetraazatetrahedrane, octaazacubane, and N(20) (27, 294.6 kcal/mol), and is useful in searching for new high-energy-high-density materials.
Abstract: Polynitrogen molecules have been studied systematically at high levels of ab initio and density functional theory (DFT). Besides N2, the thermodynamically most stable Nn molecules, located with the help of a newly developed energy increment system, are all based on pentazole units. The geometric, energetic, and magnetic criteria establish pentazole (2) and its anion (3) to be as aromatic as their isoelectronic analogues, e.g., furan, pyrrole, and the cyclopentadienyl anion. The bond lengths in 2 and 3 are equalized; both have large aromatic stabilization energies (ASE) and also substantial magnetic susceptibility exaltations (Λ). The Cs symmetric azidopentazole (14), a candidate for experimental investigation, is the lowest energy N8 isomer but is still 196.7 kcal/mol higher in energy than four N2 molecules. Octaazapentalene (12) with 10 π electrons also is aromatic. The D2d symmetric bispentazole (21) is the lowest energy N10 minimum but is 260 kcal/mol higher in energy than five N2 molecules. For strain...
241 citations
TL;DR: A detailed introduction to cyclo-N5- is provided and recent studies are summarized to improve the understanding of polynitrogen chemistry while supporting further research into its potential application as an efficient, safe, and environmentally friendly HEDM.
Abstract: 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.
145 citations
TL;DR: Sodium pentazolates NaN5 and Na2N5, new high energy density materials, are discovered during first principles crystal structure search for the compounds of varying amounts of elemental sodium and nitrogen as mentioned in this paper.
140 citations
TL;DR: A solvent-free pentazolate complex, AgN5, and a 3D energetic-framework, [Ag(NH3)2]+[Ag3(N5)4]− 3D framework, constructed from silver and cyclo-N5ˉ are reported, constituting a major advance in pentazole chemistry.
Abstract: The pentazolate anion, as a polynitrogen species, holds great promise as a high-energy density material for explosive or propulsion applications. Designing pentazole complexes that contain minimal non-energetic components is desirable in order to increase the material’s energy density. Here, we report a solvent-free pentazolate complex, AgN5, and a 3D energetic-framework, [Ag(NH3)2]+[Ag3(N5)4]ˉ, constructed from silver and cyclo-N5ˉ. The complexes are stable up to 90 °C and only Ag and N2 are observed as the final decomposition products. Efforts to isolate pure AgN5 were unsuccessful due to partial photolytical and/or thermal-decomposition to AgN3. Convincing evidence for the formation of AgN5 as the original reaction product is presented. The isolation of a cyclo-N5ˉ complex, devoid of stabilizing molecules and ions, such as H2O, H3O+, and NH4+, constitutes a major advance in pentazole chemistry. The pentazolate anion shows great promise for high energy density materials, but has only been isolated alongside non-energetic counter ions that impede its energetic properties. Here, the authors synthesize a silver cyclo-N5-complex devoid of stabilizing ions, as well as a complementary [Ag(NH3)2]+[Ag3(N5)4]− 3D framework.
137 citations
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Performance Metrics
| Year | Papers |
|---|---|
| 2022 | 1 |
| 2021 | 12 |
| 2020 | 3 |
| 2019 | 8 |
| 2018 | 10 |
| 2017 | 8 |