Monoammoniate of Calcium Amidoborane: Synthesis, Structure, and Hydrogen-Storage Properties

The monoammoniate of calcium amidoborane, Ca­(NH2BH3)2·NH3, was synthesized by ball milling an equimolar mixture of CaNH and AB. Its crystal structure has been determined and was found to contain a dihydrogen-bonded network. Thermal decomposition under an open-system begins with the evolution of about 1 equivalent/formula unit (equiv.) of NH3 at temperatures 2BH3)2 to release hydrogen. In a closed-system thermal decomposition process, hydrogen is liberated in two stages, at about 70 and 180 °C, with the first stage corresponding to an exothermic process. It has been found that the presence of the coordinated NH3 has induced the dehydrogenation to occur at low temperature. At the end of the dehydrogenation, about 6 equiv. (∼ 10.2 wt %) of hydrogen can be released, giving rise to the formation of CaB2N3H.