1‐(Azidomethyl)‐5H‐Tetrazole: A Powerful New Ligand for Highly Energetic Coordination Compounds

Abstract

Highly energetic 1‐(azidomethyl)‐5H‐tetrazole (AzMT, 3) has been synthesized and characterized. This completes the series of 1‐(azidoalkyl)‐5H‐tetrazoles represented by 1‐(azidoethyl)‐5H‐tetrazole (AET) and 1‐(azidopropyl)‐5H‐tetrazole (APT). AzMT was thoroughly analyzed by single‐crystal X‐ray diffraction experiments, elemental analysis, IR spectroscopy and multinuclear (1H, 13C, 14N, 15N) NMR measurements. Several energetic coordination compounds (ECCs) of 3d metals (Mn, Fe, Cu, Zn) and silver in combination with anions such as (per)chlorate, mono‐ and dihydroxy‐trinitrophenolate were prepared, giving insight into the coordination behavior of AzMT as a ligand. The synthesized ECCs were also analyzed by X‐ray diffraction experiments, elemental analysis, and IR spectroscopy. Differential thermal analysis for all compounds was conducted, and the sensitivity towards external stimuli (impact, friction, and ESD) was measured. Due to the high enthalpy of formation of AzMT (+654.5 kJ mol−1), some of the resulting coordination compounds are extremely sensitive, yet are able to undergo deflagration‐to‐detonation transition (DDT) and initiate pentaerythritol tetranitrate (PETN). Therefore, they are to be ranked as primary explosives.

1-(Nitratomethyl)-5H-tetrazole: A Highly Sensitive Ligand with Improved Oxygen Balance for Laser-Ignitable Coordination Compounds

“…Therefore, the overall low thermal stability of 1 is inherited to the resulting ECC. On the other hand, the more balanced (2:1) ligand to metal salt ratio of compounds 6–8 leads to stabilization of the low thermal stability of 1 by the nitroaromatic anions, which is contrary to previous findings. ,, While a stabilizing effect was previously observed for some cases, it was never as significant as it is in this study. The drastic increase in thermal stability is most likely due to the low thermal stability of 1 , resulting in high relative differences between the pure ligand and the resulting ECCs.…”

“…As displayed in Figure , the trinitrophloroglucinate anions form intermolecular hydrogen bonds between the two hydroxy groups and the para-positioned nitro group, which is hence nearly perfectly planar with the aromatic ring. This ultimately leads to a rotation of the two remaining nitro groups out of plane, positioning them in an orientation disfavoring a coordination of the metal center by the nitro groups, as is observed in comparable compounds …”

“…The crude isomeric mixture of 1-and 2-(hydroxymethyl)-5Htetrazole was synthesized according to the literature. 11 The isomeric mixture was added to a stirring mixture of acetic anhydride and fuming nitric acid precooled to 5 °C. Preliminary separation of the isomers is not necessary due to a complete decomposition of the 2N isomer during nitration.…”

“…The synthesis of 1-NAMT ( 1 ) is shown in Scheme . The crude isomeric mixture of 1- and 2-(hydroxymethyl)-5 H -tetrazole was synthesized according to the literature . The isomeric mixture was added to a stirring mixture of acetic anhydride and fuming nitric acid precooled to 5 °C.…”

“…Furthermore, the sensitivities of the pure ligand should be approximately in the range that is desired for intended use of the resulting ECC. As the formation of ECCs most often leads to an increase in sensitivity, 9 it is easily possible to overstate the sensitivities of the resulting ECCs as seen in the work on 1-amino-5Htetrazole 10 (1-AT) or 1-azidomethyl-5H-tetrazole 11 (AzMT). Among the nitrogen-rich heterocyclic compounds, those based on the 1,5H-tetrazole (Figure 1) moiety are promising substances to be applied as ligands.…”