Synthesis and Reactions of a Redox-Active α‑Diimine Aluminum Complex

The reaction of the ene-diamine LH₂ (L = [ArNC­(Me)­C­(Me)­NAr]^2–, Ar = 2,6-<i>i</i>Pr₂C₆H₃) with AlMe₃ and AlEt₃ yielded the aluminum dimethyl complex (LH)­AlMe₂ (<b>1</b>) and the radical (L^•)­AlEt₂ (<b>2</b>; L^• = [ArNC­(Me)­C­(Me)­NAr]^•–), respectively. Treatment of <b>2</b> with O₂ and TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) led to hydrogen abstraction from the methyl group at the ligand backbone to give the diamagnetic species (L*)­AlEt₂ (<b>3</b>; L* = [ArNC­(Me)­C­(CH₂)­NAr]⁻) and (L*)­Al­(TEMPO)­(Et) (<b>4</b>). In contrast, the reaction of <b>2</b> with iodine resulted in the iodination of the Al–C bonds and yielded the radical (L^•)­AlI₂ (<b>5</b>). Reaction of <b>2</b> with BCl₃ led to electron transfer between the α-diimine radicals with the formation of the aluminum cation [(L⁰)­AlCl₂]⁺[AlCl₄]⁻ (<b>6</b>; L⁰ = ArNC­(Me)­(Me)­CNAr) and the diazaborole LBCl (<b>7</b>). The structures of compounds <b>2</b>, <b>3</b>, and <b>7</b> have been determined by X-ray single-crystal diffraction, and the paramagnetic species <b>2</b> has been characterized by EPR measurements