The reversible synthesis of bis(quinuclidine) alane

Aluminum hydride is a material that is well known for its high gravimetric and volumetric hydrogen densities and thus is an attractive hydrogen storage compound; however, it is thermodynamically unstable at room temperature requiring 7 × 103 bar pressure to reform the hydride from Al and H2. An alternate method of AlH3 formation is possible using a reversible organometallic synthesis employing catalyzed Al powder, H2, and quinuclidine, or another tertiary amine, as an intermediate step. Additionally, many tertiary amines are known to react directly with AlH3 to form adducts. Previous work indicates that two polymorphs of quinuclidine alane exist, formed using an irreversible process that requires expensive starting materials (e.g. LiAlH4). The conditions of reversible adduct formation are detailed herein, as well as an analysis of quinuclidine alane by Fourier transform infrared spectroscopy and X-ray diffraction.

Research highlights▶ Synthesis of quinuclidine alane by direct hydrogenation of Al and quinuclidine. ▶ Hydrogenation occurs at low pressure in the presence of Ti catalyst. ▶ Product is bis(quinuclidine alane). ▶ Hydrogenation reaction is reversible.