Lewis-Base Stabilization of the Parent Al(I) Hydride under Ambient Conditions

Aluminum­(III) is inherently electron deficient and therefore acts as a prototypical Lewis acid. Conversely, Al­(I) is a rare, nucleophilic variant of aluminum that is thermodynamically unstable under ambient conditions. While attempts to stabilize and isolate Al­(I) species have become increasingly successful, the parent Al­(I) (i.e, Al–H) remains accessible only under extreme temperatures/pressures or matrix conditions. Here, we report the isolation of the parent Al­(I) hydride under ambient conditions via the reduction of a Lewis-base-stabilized alkyldihaloalane. Computational and spectroscopic analyses indicate that the ground-state electronic configuration of this monomeric aluminum species is best described as an Al­(I) hydride with non-negligible open-shell Al­(III) singlet diradical character. These findings are also supported by reactivity studies, which reveal both the p-centered lone pair donating ability and the hydridic nature of the parent aluminene.