Calcium Amidoborane Ammoniate-Synthesis, Structure, and Hydrogen Storage Properties

A new type of hydrogen storage material-namely, calcium amidoborane ammoniate (Ca(NH2BH3)(2)center dot 2NH(3))-is synthesized by reacting calcium amide and ammonia borane in a molar ratio of 1:2. Structural analyses show that this newly developed complex has a orthorhombic structure (space group Pna21) with unit-cell parameters of a = 18.673(3) angstrom, b = 5.2283(8) angstrom, c 8.5748(12) angstrom, and V = 873.16(22) angstrom(3). The presence of NH3 in the crystal lattice facilitates the formation of dihydrogen bonding between BH center dot center dot center dot HN, which is considerably shorter than that in calcium amidoborane (Ca(NH2BH3)(2)). As a consequence, the bond lengths of B-H and N-H are increased comparatively. Our experimental results show that more than 8 wt % hydrogen can be released from Ca(NH2BH3)(2)center dot 2NH(3) without borazine emission at 150 degrees C.