Ionic Ferrocenyl Compounds Containing Polycyano Anions. Synthesis, Structures, and Effects on Thermal Decomposition of Core Components of Solid Propellants

For lowering high migration tendency of alkyl-substituted ferrocenes as burning-rate catalysts in composite solid propellants, eight new ionic ferrocenyl compounds, [FcCH(2)N(CH3)(2)(CnH2n+1]X+(Fc = ferrocenyl; X- = 1,1,3,3-tetracyanopropenide; n = 3-10; consequently numbered as 1-8), were synthesized and characterized by H-1 NMR, C-13 NMR, FT-IR and UV/Vis spectroscopy as well as elementary analysis. In addition, the structures of 1, 3, and 5 were confirmed by single-crystal X-ray diffraction analysis and their cations were studied by density functional theory calculations (DFT). 1, 3, and 5 crystallize in the triclinic space group P (1) over bar. 1-6 show highly thermal stability (>166 degrees C), whereas compounds 7 and 8 exhibit volatility to a certain degree. Cyclic voltammetry studies suggested that each salt exhibits a quasi-reversible redox wave of the ferrocenyl group. The effects of the new compounds on thermal decomposition of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) were investigated by DSC technique. The results show that all the new compounds can catalyze thermal degradation of AP and RDX effectively and are higher in catalytic activity than the corresponding nitrates and picrates, verifying the prospect that relatively high nitrogen content in an ionic ferrocenyl compound is able to enhance its combustion catalytic efficiency.