alanes

Alanes, also known as alanes, are a family of aluminum hydride compounds with the general formula AlH3 and related oligomeric and donor-stabilized derivatives. They are of interest primarily in inorganic and materials chemistry due to their unusual bonding, reactivity, and potential applications.

Structure and properties

In the solid state, alanes typically form polymeric or oligomeric networks in which aluminum centers are bridged by hydride ligands. In contrast, adducts formed by coordinating a Lewis base (such as an amine or ether) to AlH3 yield donor-stabilized species (for example, AlH3·amine or AlH3·ether) that can be more volatile and easier to handle. Gas-phase species can differ from the condensed-phase structures, with monomeric AlH3 or small clusters observed under certain conditions. Alanes are highly reactive toward moisture and oxygen, and many compounds hydrolyze to aluminum hydroxides with release of hydrogen.

Preparation

Alanes are typically prepared or accessed via reactions involving aluminum trihalides, aluminum alkyls, or other aluminum hydride precursors in the presence of hydride donors. Adducts with Lewis bases are prepared by combining AlH3 with the appropriate donor ligand in inert solvents. Due to their reactivity, many alane formulations are generated and handled under strictly anhydrous, inert atmosphere conditions.

Applications and research

Alanes are studied for fundamental bonding and structural chemistry and as potential hydrogen storage materials, owing to their ability to release hydrogen upon decomposition. Donor-stabilized alanes are used in research as precursors for aluminum-containing materials and in specialized synthetic contexts where aluminum hydride delivery is desired. Their practical use is often limited by sensitivity to air and moisture and by handling challenges compared with more robust hydride reagents.

Safety

Alanes are moisture- and air-sensitive. Hydrolysis or contact with water releases hydrogen gas and heat, and many alane formulations can be reactive or pyrophoric under certain conditions. They should be stored and handled under inert atmospheres with appropriate protective equipment.