Aluminium hydride

Aluminium hydride (also known as alane and alumane) is an inorganic compound with the formula AlH₃. Alane and its derivatives are part of a family of common reducing reagents in organic synthesis based around group 13 hydrides. In solution—typically in ethereal solvents such tetrahydrofuran or diethyl ether—aluminium hydride forms complexes with Lewis bases, and reacts selectively with particular organic functional groups (e.g., with carboxylic acids and esters over organic halides and nitro groups), and although it is not a reagent of choice, it can react with carbon-carbon multiple bonds (i.e., through hydroalumination). Given its density, and with hydrogen content on the order of 10% by weight, some forms of alane are, as of 2016, active candidates for storing hydrogen and so for power generation in fuel cell applications, including electric vehicles. As of 2006 it was noted that further research was required to identify an efficient, economical way to reverse the process, regenerating alane from spent aluminium product.

Solid aluminium hydride, or alane, is colorless and nonvolatile, and in its most common reagent form it is a highly polymerized species (i.e., has multiple AlH₃ units that are self-associated); it melts with decomposition at 110 °C. While not spontaneously flammable, alane solids and solutions require precautions in use akin to other highly flammable metal hydrides, and must be handled and stored with the active exclusion of moisture. Alane decomposes on exposure to air (principally because of adventitious moisture), though passivation — here, allowing for development of an inert surface coating — greatly diminishes the rate of decomposition of alane preparations.