Role of NH 3 in the dehydrogenation of calcium amidoborane ammoniate and magnesium amidoborane ammoniate: A first-principles study

Abstract

First-principles calculations show that [NH 3] molecules play crucial roles as both activator for the break-up of B-H bond and SUPPL.ier of protic H for the establishment of dihydrogen bonding, which could facilitate the dehydrogenation of Ca(NH 2BH 3) 2·2NH 3 or Mg(NH 2BH 3) 2·NH 3 occurring at lower temperatures compared to those of Ca(NH 2BH 3) 2 and Mg(NH 2BH 3) 2. Moreover, the calculations of Helmholtz Free energy and [NH 3] molecule removal energy evidence that coordination between [NH 3] and Mg cation is stronger than that between [NH 3] and Ca cation; therefore, Mg(NH 2BH 3) 2· NH 3 will undergo directly dehydrogenation rather than deammoniation at lower temperatures. © 2011 American Chemical Society.