Ionic Ferrocene-Based Burning-Rate Catalysts with Polycyano Anions: Synthesis, Structural Characterization, Migration, and Catalytic Effects during Combustion

Alkylferrocene-based burning-rate (BR) catalysts, have a high tendency to migrate during curing and storage due to their neutral and nonpolar nature. To overcome these drawbacks, fifteen novel ionic compounds, 1-(ferrocenylmethyl)imidazolium paired with polycyano anions, were synthesized and characterized. The structures of eleven of the compounds were confirmed by single-crystal X-ray diffraction. Compound 1 crystallizes in the tetragonal space group I4(1)/a; 2, 12 and 15 crystallize in the monoclinic space group P2(1)/c, and 3 in the monoclinic space group P2(1)/n; 4, 6-8, 13 and 14 crystallize in the triclinic space group P (1) over bar. Cyclic voltammetry investigations suggested that most of the compounds exhibit quasireversible redox systems. Compounds 1-10 have high thermal stability (>190 degrees C). Migration studies revealed that these compounds are low-migratory materials. The thermal degradation of ammonium perchlorate (AP), hexogen (RDX), and octogen (HMX) catalyzed by these compounds was evaluated by differential scanning calorimetry (DSC) and by thermogravimetric (TG) techniques. The results show that the decomposition peak temperature of AP shifts downwards dramatically and that the released heat of AP increases significantly with the new compounds as additives (5 wt.-%). Moreover, the ionic compounds exhibit significant effects on the thermal decomposition of RDX. The catalytic activities of the new compounds are higher than those of their nitrate and picrate analogues, which supports the conclusion that high nitrogen content in a ferrocene-based BR catalyst is favorable for its combustion catalytic activity.