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.