Proton transfer reactions of hydrazine-boranes

Abstract

Hydrazine-borane and hydrazine-diborane contain, respectively, 15.4 and 16.9 wt% of hydrogen and are potential materials for hydrogen storage. In this work we present the gas-phase complexation energies, acidities, and basicities of hydrazine-borane and hydrazine-bisborane calculated at MP2/6-311 + G(d,p) level. We also report the release of dihydrogen from both protonated complexes (ΔGhydrazine-borane = −20.9 kcal/mol and ΔGhydrazine-bisborane = −27.2 kcal/mol) which is much more exergonic than from analogues amine-boranes. The addition of the first BH3 to the hydrazine releases 17.1 kcal/mol, and the second addition releases 15.8 kcal/mol. The attachment of BH3 also increases the N―H acidity of hydrazine by 46.3 kcal/mol. It was found that the B―H deprotonation leads to intramolecular rearrangement. The basicity values for hydrazine-borane and -bisborane are 180 and 172.8 kcal/mol, respectively. For both complexes the protonation centres are located at the boron moiety. The protonated structure of hydrazine-bisborane is cyclic and can be described as H2 captured between a negatively charged B―H hydrogen and positive boron (B―H••H2••B). Atoms in molecules analysis are used to investigate bond paths in concerning structures. Copyright © 2015 John Wiley & Sons, Ltd.