Free Aluminylenes: An Emerging Class of Compounds

Aluminylenes (R-Al) are aluminium analogs of carbenes. In contrast to isolable carbenes, aluminylenes are extremely rare species. In the past years, pioneered by Schnöckel, Roesky and Power, a few free aluminylenes and their complexes have been reported. Such compounds have the aluminium atom in the oxidation state +I, which contrasts with classical organoaluminium derivatives that contain the element in the +III oxidation state. Aluminylenes, either in their free state or in the coordination sphere of a Lewis base, are capable of coordinating to transition metals and activating inert chemical bonds. Free aluminylenes are emerging as potent synthetic platforms for unusual aluminium species.