Substitution at a Coordinatively Saturated Aluminum Center Stabilized by Imidazolidin-2-imine

In this article, the coordination chemistry of the imidazolidin-2-imine ligand (1) toward aluminum has been delineated. We commenced our investigation by preparing dimeric aluminum dihydride {μ-LAlH2}2 (2) from the reaction of 1 with AlH3. Substitution of the hydride with methyl (3), chloride (4), and bromide (7) was achieved from the reaction of 2 with BH3·SMe2, BHCl2·SMe2, and Br2/H2O, respectively. The reaction with BH3·THF afforded a 1 → BH3 adduct (5) with simultaneous elimination of AlH3. An unprecedented spirocyclic aluminate anion with imidazolidin-2-iminium cation (6) resulted from a reaction with PhB­(OH)2. While sulfur undergoes insertion reaction into the Al–H bonds (8), the reactions with diselenides and ditellurides conveniently install unusual functionalities such as −SePh (10) and −TePh (11) onto alane.