Quantum-chemical modeling of dehydrogenation of a sodium borohydride molecule in water

Abstract

The successive elimination of Н₂ from a NaBH₄ molecule surrounded by a few (up to eight) water molecules has been modeled in the framework of the cluster approach with the use of the 6-31G* basis set and hybrid density functional (B3LYP). Computations show that the elimination of the hydrogen molecule from the NaBH₄ · nH₂O complex occurs through the coupling of Н^– and Н⁺ ions from BH₄⁻ and Н₂О, respectively, to form intermediate ВН₃ and ОН^– species separated by water molecules. Proton transfer occurs along a hydrogen bond chain through a relay mechanism. The elimination of the remaining hydrogen atoms to convert the BH₄⁻ anion into B(OH)₄⁻ proceeds analogously but with lower barriers.