The
employment of combustion catalysts is an effective
way to improve
ammonium perchlorate (AP) decomposition performance during the combustion
process of composite solid propellants. A classic half-sandwich iron
carbonyl complex was proposed as the leading structure for exploring
high-performance combustion catalysts, in which functionalized cyclobutadienes
(Cb) tune the thermal stability and catalytic activity. The thermolysis
of Fe2(CO)9 and substituted alkynes initiated
[2 + 2] cyclization of alkyne triple bonds and gave η4-cyclobutadiene iron(0) tricarbonyl complexes, CbR1,R2-Fe-CO (1–6), with decent yields.
A molecular structure analysis found that the conjugation of the aromatic
substituents aryl, ferrocenyl (Fc), and triazinyl (Tz) finely tuned
the coordination bonds around the Fe(0) center. The DSC/TG experiments
found a remarkable thermal stability of CbTz,R-Fe-CO (3–6) with characteristic thermolysis temperatures
(CTT) as high as 500 °C. The catalytic experiments demonstrated
that the CTT of Cb-Fe-CO (2-6) overlapped
with AP high-temperature decomposition (HTD). The thermal cross-coupling
of HTD of AP and CTT of CbTz,Fc-Fe-CO (6)
significantly augmented catalytic AP decomposition, resulting in a
maximum energy release as high as 2828 J/g.