Synthesis and reactions of a redox-active α-diimine aluminum complex

Article abstract of DOI:10.1021/om300920y

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)AlCl ₂]⁺[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.