Synthesis and Characterization of High-Energy Anti -Perovskite Compounds Cs 3 X [B 12 H 12 ] Based on Cesium Dodecahydro- Closo -Borate with Molecular Oxoanions ( X - = [NO 3 ] - , [ClO 3 ] - and [ClO 4 ] - ).

Three novel anti -perovskite compounds, formulated as Cs3 X [B12 H12 ] ( X- = [NO3 ]- , [ClO3 ]- , and [ClO4 ]- ), were successfully synthesized through the direct mixing of aqueous solutions containing Cs2 [B12 H12 ] and Cs X ( X- : [NO3 ]- , [ClO3 ]- , [ClO4 ]- ), followed by isothermal evaporation. All three compounds crystallize in the orthorhombic space group Pnma , exhibiting relatively similar unit-cell parameters (e.g., Cs3 [ClO3 ][B12 H12 ]: a = 841.25(5) pm, b = 1070.31(6) pm, c = 1776.84(9) pm). The crystal structures were determined using single-crystal X-ray diffraction, revealing a distorted hexagonal anti -perovskite order for each. Thermal analysis indicated that the placing oxidizing anions X - into the 3 Cs+ + [B12 H12 ]2- blend leads to a reduction in the thermal stability of the resulting anti -perovskites Cs3 X [B12 H12 ] as compared to pure Cs2 [B12 H12 ], so thermal decomposition commences at lower temperatures, ranging from 320 to 440 °C. Remarkably, the examination of the energy release through DSC studies revealed that these compounds are capable of setting free a substantial amount of energy, up to 2000 J/g, upon their structural collapse under an inert-gas atmosphere (N2 ). These three compounds represent pioneering members of the first ever anti -perovskite high-energy compounds based on hydro- closo -borates.