Synthesis and characterization of iron and ruthenium complexes with the hydrotris(3,5-dimethyl-pyrazolyl)borate ligand and application as burning rate catalysts for solid rocket motor propellant

Abstract

In this work, we reported two complexes [Tp*FeCp*] (1) and [Tp*RuCp*] (2) obtained from the reaction of respective pentamethylcyclopentadienyl metal precursors and [hydrotris(3,5-dimethyl-pyrazolyl)borate] (Tp*). Both complexes were characterized by 1H and 13C NMR, elemental analysis, FT-IR, UV–vis, and cyclic voltammetry. The synthesized complexes [Tp*MCp*] and analogous compounds [(Cp*)2M] (with M = Fe and Ru) were tested as catalysts on the thermal decomposition of ammonium perchlorate by a differential scanning calorimetry (DSC) technique. Compound 2 caused a decrease ammonium perchlorate’s decomposition temperature displacing it to 326 °C compared to compound 1 and [(Cp*)2M] species. However, compound 2 presented the lowest energy released compared to the complexes here reported (408 J·g−1). In addition, the results obtained from the cyclic voltammetry characterization evidenced that the electrochemically active species of compounds 1 and 2 exhibit noteworthy oxidation peaks. These results suggest that compounds 1 and 2 here presented are suitable and competitive alternatives to be used as a modifier for composite solid propellants.