Quantum mechanics investigation on initial decomposition of ammonia borane in glyme

Abstract

AbstractThe chemical kinetics of ammonia borane (AB) in glyme solution is studied using quantum mechanics (QM) based calculations along with experimental results available in the literature. The primary objective of this study is to propose a detailed reaction mechanism that explains the formation of species observed during AB decomposition for temperatures ranging from 323 to 368 K. The quantum mechanics investigation uses transition state theory to identify the relevant reaction pathways. Intrinsic reaction coordinate calculations use the identified transition‐state structure to link the reactants to the products. These calculations were performed using the Gaussian 09 program package, including the solvation model based on density (SMD) with acetonitrile as the solvent. Thermodynamic properties of species at equilibrium or at transition states were computed using the G4(MP2) compound method. Sensitivity analysis was performed using a species conservation model to identify reactions and species that play a critical role. This study confirms the previous experimental observation regarding the initiation of decomposition of AB in glyme. It also elucidates the role of DADB, ammonium borohydride salt ([BH4]−[NH4]+) and BH2NH2 in hydrogen release and intermediates formed during initial phase of AB decomposition. This work shows how QM calculations along with experimental results can contribute to our understanding of the complex chemical kinetics involved during AB dehydrogenation.