Regeneration of aluminium hydride using dimethylethylamine

Abstract

Aluminium hydride is a compound that is well known for its high gravimetric and volumetric hydrogen densities and favorable hydrogen storage properties. Tertiary amine–aluminium hydride complexes have gained interest due to their application as chemical reducing agents and in aluminium thin-film deposition. Various complexes of these amine alane compounds have been created and studied previously, but these compounds were not formed directly using pressurized hydrogen. Here, we demonstrate the direct reaction of catalyzed aluminium, a tertiary amine, and hydrogen in a common solvent proceeds to form an amine alane adduct at moderate pressures and temperatures. A complex of aluminium hydride has been formed with dimethylethylamine by this technique. A vibrational analysis of the product of these reactions by Raman and infrared spectroscopy is presented, including experimental and theoretical data. The results clarify the molecular and vibrational structure of amine alane complexes formed by direct hydrogenation and are compared with previously determined experimental information. In addition, we demonstrate a new method for the formation of triethylamine alane using the direct hydrogenation of dimethylethylamine and catalyzed aluminium followed by transamination with triethylamine. Finally, we propose a new low energy method to regenerate AlH₃ from catalyzed aluminium and hydrogen gas.