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-iPr2C6H3) with AlMe3 and AlEt3 yielded the aluminum dimethyl complex (LH)AlMe2 (1) and the radical (L•)AlEt2 (2; L• = [ArNC(Me)C(Me)NAr]•–), respectively. Treatment of 2 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 (3; L* = [ArN═C(Me)C(CH2)NAr]−) and (L*)Al(TEMPO)(Et) (4). In contrast, the reaction of 2 with iodine resulted in the iodination of the Al–C bonds and yielded the radical (L•)AlI2 (5). Reaction of 2 with BCl3 led to electron transfer between the α-diimine radicals with the formation of the aluminum cation [(L0)AlCl2]+[AlCl4]− (6; L0 = ArN═C(Me)(Me)C═NAr) and the diazaborole LBCl (7). The structures of compounds 2, 3, and 7 have been determined by X-ray single-crystal diffraction, and the paramagnetic species 2 has been characterized by EPR measurements.