Energetic coordination compounds of late 3d metals with 1N-(Nitromethyl)-5H-tetrazole, a ligand with astonishing properties from the rare class of N-nitromethyl azoles

Abstract

The hardly accessible N-nitromethyl moiety is introduced onto the 1,5H-tetrazole scaffold, representing the fourth and fifth ever synthesized N-nitromethyl azoles. Both compounds 1-(Nitromethyl)-5H-tetrazole (2a) and 2-(Nitromethyl)-5H-tetrazole (2b) are thoroughly analyzed by low-temperature single-crystal X-ray diffraction experiments, complemented by elemental analysis, multinuclear (1H, 13C, 14N, 15N) NMR as well as IR spectroscopy. Sensitivity measurements towards external stimuli revealed two highly insensitive compounds. Additionally, 2a was applied as ligand for energetic coordination compounds of 3d transition metals (e.g. Cu, Fe, Ni, and Zn) in combination with oxidizing nitrate, chlorate and perchlorate anions. The synthesized ECCs were analyzed by low-temperature single-crystal X-ray diffraction experiments, elemental analysis and IR spectroscopy. The thermal behavior of all compounds was investigated by differential thermal analysis and the sensitivities towards impact and friction was measured. Due to the lack of information about the properties of N-nitromethyl azoles, the complete insensitivity towards external stimuli of 2a and 2b supports first hints of a sensitivity decreasing influence of the N-nitromethyl moiety, which is highly desired when designing new high explosives. Additionally, the functional group is able to introduce meltability into molecular scaffolds.