Synthesis, Clarifying Properties and Refining Structures of Single-Crystal Magnesium Borohydride Di- and Triammine Complexes

The magnesium borohydride complexes with ammonia, Mg(BH4)2•2NH3 (MA-2) and Mg(BH4)2•3NH3 (MA-3), were obtained in a single crystal form and their structures were determined by the X-ray diffraction analysis. According to the powder X-ray diffraction and IR spectroscopy results, the data in some published works, where the MA-3 was positioned as an individual compound, were shown to contain additional reflections that are in good agreement with those for Mg(BH4)2•6NH3 (MA-6). The study of the thermolysis process of the individual MA-3 by DSC-TGA-MS showed that the heating of the triammine to a temperature of 600 °C leads to the release of ammonia and hydrogen in a molar ratio H2: NH3 = 8: 1, with a total yield of H2 reaching 12 wt.