Synthesis and characterisation of the novel energetic triazenide: PPN bis(1-methyl-3-nitro-1,2,4-triazol-5-yl)triazenide

Abstract. Conventional energetics rely primarily on the chemistry on C-, N- and O- nitrated compounds as well as azides. Progress in energetic materials chemistry now relies more heavily on the exploitation of hitherto underexplored explosophoric groups. One such group relates to the structural motif of the triazenyl (R-N=N-NR₂) or triazenido groups (R-N=N-N^(-)-R) to which only a narrow record is associated in the chemical literature. We report on an experimental investigation into the synthesis of novel triazenes and triazenides, followed by a brief assessment of their potential to function as both the basis for energetic materials, and as explosophoric ligands and proligands in the synthesis of novel energetic coordination compounds. The previously unreported bis(1-methyl-3-nitro-1,2,4-triazol-5-yl)triazene (H-B1M3NTT) was isolated as the hydrated 1 : 1 bis(triphenylphosphine) iminium salt, PPN (B1M3NTT) · 3H₂O. The crystal structure of PPN (B1M3NTT) · 3H₂O was determined. No interactions between PPN cation and B1M3NTT anion are present. Hydrogen bonds were found involving B1M3NTT and H₂O. PPN (B1M3NTT) · 3H₂O dehydrates between 80 to 100 ^oC, but is otherwise highly temperature stable, exceeding onset and peak decomposition temperatures of the analogous iminium bis(1-methyl-tetrazol-5-yl)triazenide salt PPN (B1MTT). Based on our estimates for crystal density and heat of formation, and methods used to approximate Q, D_CJ and p_CJ values, H-B1M3NTT is predicted to have higher density, greater heat of detonation, and higher detonation pressure than both H-B1MTT and the related bis(2-methyl-tetrazol-5-yl)triazene (H-B2MTT) - compounds previously investigated as nitrogen-rich candidate components of solid rocket propellants.