A series of energetic metal pentazolate hydrates

Abstract

Singly or doubly bonded polynitrogen compounds can decompose to dinitrogen (N) with an extremely large energy release. This makes them attractive as potential explosives or propellants, 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 phases, 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 1900s and characterized in the 1950s. Salts containing the azide anion (N) or pentazenium cation (N) are also known, with compounds containing the pentazole anion, cyclo-N, a more recent addition. Very recently, a bulk material containing this species was reported and then used to prepare the first example of a solid-state metal-N complex. Here we report the synthesis and characterization of five metal pentazolate hydrate complexes [Na(HO)(N)]·2HO, [M(HO)(N)]·4HO (M = Mn, Fe and Co) and [Mg(HO)(N)]·4HO 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 N 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 materials or enable the development of such materials containing only nitrogen. We also anticipate that the adaptability of the N ion in terms of its bonding interactions will enable the exploration of inorganic nitrogen analogues of metallocenes and other unusual polynitrogen complexes.

Molecular perovskite high-energetic materials

“…To obtain a better explosive performance, an efficient strategy is to load unstable chemical bonds [1][2][3], as well as to combine fuel with oxidizer components in a proper ratio for achieving sufficient combustion and rapid detonation [4][5][6]. An effective way is to incorporate fuel and oxidizer properties into a single molecule [7], as demonstrated by a series of classical organic nitro group/nitrogen-rich molecules, such as trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), hexanitrohexaazaisowurtzitane (CL-20) and octanitrocubane (ONC) (Fig.…”

Amorphous polymerization of nitrogen in compressed cupric azide

“…The pentazolate anion cyclo ‐N is of great interest in recent studies due to its potential application in high‐energy‐density materials . It can be stabilized using several chemical strategies, including metal salts and metal‐inorganic frameworks . The application of high pressure provides another route to synthesize cyclo ‐N.…”

Self-assembled energetic coordination polymers based on multidentate pentazole cyclo-N5−

“…Unfortunately, owing to the unstable bonding interactions with other anions, further developments of N 5 + ion have been limited. The pentazole anion cyclo-N 5 -was first detected in 2002 via mass spectrometry (MS) [18,19] and was not adopted for bulk production until recently [20][21][22][23][24][25][26]. However, the anhydrous pentazole sample NaN 5 [21] and CsN 5 [22] were only observed under extreme high pressure and the metal-pentazole hydrates [24][25][26] decomposed in the range of 100-110°C.…”

“…Both high pressure preparing method and hydrates samples are the disadvantages in terms of their application. Fortunately, the cyclo-N 5 -anion shows good adaptability to take part in ionic, coordination, and hydrogen bonding interactions [24,27]. Furthermore, there is a possibility to form either energetic CPs or co-crystals by self-assembling, which is a new technology for modifying or enhancing the properties of existing energetic substances.…”