Maximization of the energy capability level in transition metal complexes through application of 1-amino- and 2-amino-5H-tetrazole ligands

Abstract

This comprehensive study features the synthesis, characterization and evaluation of new energetic coordination compounds (ECC) based on two of the most powerful neutral tetrazoles, which have great potential as lead-free primary explosives.

Comparison of 1‐Ethyl‐5H‐tetrazole and 1‐Azidoethyl‐5H‐tetrazole as Ligands in Energetic Transition Metal Complexes

“…Again these results contradict earlier observations. [32,33] Compounds 8-11 show comparable trends to external stimuli as in thermal experiments.C omplexes based on ligand 1 are more sensitive(8 and 10 are both ranked as extremely sensitive) than those of compound 2 (both sensitive) and the copper(II) chlorate complexes are less stable (11)o ra tl east show similar sensitivities (10)c ompared to the analogousp erchlorate ones (Figure 11), which is in accordance to our previous findings. [34] The nitroaromatic derivatives 12-14 possess one of the highest stabilities of all complexes toward friction,b ut due to their sensitivities toward impact, they are all ranked as very sensitive( Figure S17).…”

“…The relatively lowt hermal stabilities of the nitrato compound 3 (T exo = 152 8C), as well as the chlorate complexes,a re ak nown issue, resultingf rom the metal salt, the coordination compounds are based on and is already reportedi nl iterature. [32,33] Besides its low point of exothermic decomposition,t he nitrato complex (3)i st he only compound showing two endothermic signals (T endo1 = 94 8C, T endo2 = 121 8C), indicating melting, followed by the loss of coordinating aqua ligand (proofed by TGA). Other endothermic events of compounds 6 and 8-11 can also be assignedt ot heir respective melting points, which were also observedd uring heating of the respective compounds in hot plate tests.…”

“…1-methyl-or 1-amino-5H-tetrazole) have been described in literature, either having insufficient powero ra re wayt oo sensitive for practical use. [32,33] In order to maximize the performance, ligand 1 is appliedi nt he formation of new transition metal complexes, whereas the use of ligand 2 is ap romising opportunity for reaching the middle courseb etween both demands. The absence of acidic protons in both ligands allows their inclusion in neutral metal coordination compounds with oxidizing anions like nitrates,p erchlorates, picrates (PA), styphnates (TNR) or 2,4,6-trinitro-3,5-dihydroxyphenolates (H 2 TNPG).…”

“…The formation of as evenfolded coordination sphere is ab ehavior,a lready observed for 1H-substituted tetrazole derivatives in copper(II) nitrato complexes with similar bond lengthsa roundt he central metal. [33] The metal(II) perchlorate complexes 5, 6 and 8 all crystallize isotypically in the monoclinic space group P2 1 /c with similar cell parameters and densities. Unfortunately,c ompounds 6 and 8 could only be measured at r.t. and therefore the ethyl azide moieties are highly disordered.…”

“…[40,41] Based on latest results concerning the laser ignition of ECC, this work focused only on the colored compounds 3, 5 and 8-14. [33] Further information for the applieds etup can be found in the Supporting Information. All complexes showedr eaction toward laser irradiation ( Table 2), which strongly differed by the applied ligand and anion system.…”