o‑Carborane-Based and Atomically Precise Metal Clusters as Hypergolic Materials

Atomically precise o-carborane­alkynyl-protected clusters [Ag14(C4B10H11)12­(CH3CN)2]·2NO3 (CBA-Ag) and [Cu6Ag8­(C4B10H11)12Cl]­NO3 (CBA-CuAg) have been found to exhibit hypergolic activity, such that they are capable of spontaneous ignition and combustion upon contact with the white fuming nitric acid oxidizer. In particular, CBA-CuAg has a short ignition delay time of 15 ms, whereas the o-carborane­alkynyl ligand is hypergolically inert. Systematic investigation revealed that the metal cluster core catalyzed the hypergolic behavior of inert o-carborane­alkynyl ligand, and Cu doping further accelerated combustion catalysis. This work provides a new prospective in the rational design of novel metal cluster-based hypergolic fuels for propellant application.