Isolable radical cation and dication of dialumene

Alkenes are known to undergo successive oxidation to form alkene-derived radical cations and dications, which have found applications across various fields. As the aluminum analogues of alkenes, dialumenes likewise have the potential to lose one or two π-bonding electrons, forming dialumene-derived radical cations or dications. To date, however, these species have remained elusive, most likely due to the intrinsic electron deficiency imposed by both the positive charge and the pronounced electrophilicity of aluminum. Here, we present the synthesis of a stable aluminum-centered radical cation and dication through the combination of bulky silyl substituents and electron-donating carbene ligands. Further studies reveal that these aluminum complexes can switch between their neutral, radical cationic, and dicationic states, thus establishing a redox-reversible system. Furthermore, the dication exhibits multiple modes of reactivity, acting as a Lewis acid while also mediating both deoxygenation reactions and isocyanide homologation.