Unanticipated ionic ferrocenyl compounds based on 5,5′-bis(1-hydroxytetrazole). Molecular structures, anti-migration and burning rate catalytic performances

Abstract

Twenty-one ionic ferrocenyl ammonium (1–17) and 1,2,4-triazolium (18–21) compounds derived from 5,5′-bis(1-hydroxytetrazole) were synthesized and characterized by NMR, FT-IR, UV − Vis and elemental analysis, aiming at improving anti-migration ability of neutral ferrocene-based burning rate catalysts and reducing sensitivity of the ionic ferrocenyl compounds containing picrate anions. Six new compounds were additionally characterized by single-crystal X-ray diffraction. The characterization results showed that, by ion-exchange reactions, 1–10, 12, 15 and 17 are the anticipated compounds in their molecular structures, compounds 11, 13 and 16 were formed by C-N bond cleavage of the dinuclear ferrocenyl cation units and 18–21 were obtained by protonation of the divalent 5,5′-bis(1-hydroxytetrazolate) anion at one oxygen atom. Thermal gravimetry and anti-migration test indicated that the new compounds are highly thermally stable and show low volatility and low migration tendency. Cyclic voltammetry studies suggested that most of the novel salts are irreversible redox systems. The sensitivity tests towards impact revealed that compounds 1–17 are insensitive compounds. The catalytic tests implied that all compounds exhibit great effects on the thermal degradation of ammonium perchlorate and 1,3,5-trinitro-1,3,5-triazacyclohexane. Compounds 13–15 can be used as potential alternatives to catocene in the composite solid propellants.