Safe Stockpiling of the MTX-1 Primary Explosive in Alkali or Alkaline Earth Metal Complexes and Coordination Polymers

The safe stockpiling of high-energy combustible and explosive materials is important for environmental and human population protection, particularly in mining and military areas. MTX-1 (2-(tetrazol-5-yl-diazenyl)guanidine) is used in percussion primer compositions that react rapidly with the hydroxides of alkali or alkaline earth metals to form complexes of diverse composition. These are insensitive to mechanical stimuli and to intense heat under high confinement. The most stable complexes were found to be those with ions having the smallest effective ion radii (Mg²⁺ and Ca²⁺), followed by Li⁺. These complexes form discrete mononuclear (Mg²⁺ and Ca²⁺) or dimeric (Li⁺) structures in the solid state. One-dimensional (1D) (Na⁺, Sr²⁺, and Ba²⁺), 2D (K⁺ and Rb⁺), and 3D (Cs⁺) coordination polymeric structures were found for the remaining complexes with larger ions. Detailed topological analysis of the electron density and quantitative estimation of π-π stacking interactions were performed. Complexes could be used for intense flame coloring in pyrotechnics. Upon thermal treatment of complexes over ∼200 °C, water is lost from the coordination sphere of the metal ion, which leads to materials that are slightly sensitive and rehydrate in moist air. Recovery of insoluble MTX-1 is possible when these complexes are treated with an aqueous acid.