Synthesis, reactivity, and structures of dialuminum complexes containing linked ketiminate ligands

Linked bis(ketimine) (1) can be prepared with the reaction of excess 2,4-pentanedione and 4,4′-methylene-bis(2,6-diisopropylaniline) in methanol in the presence of catalytic amount of formic acid. The dialuminum alkyl complexes containing the linked bis(ketiminate) dianionic ligands, [OC(Me)CHC(Me)N(2,6-iPr2C6H2-4)AlR2]2CH2 (2, R = Me; 3, R = Et), were prepared by a reaction of 2 equiv AlR3 with [OC(Me)CHC(Me)NH(2,6-iPr2C6H2-4)]2CH2 in methylene chloride. Reactions of 2 with 2 and 4 equiv of I2 gave corresponding aluminum iodo complexes 4 and 5, respectively. Treatment of 5 with 2 equiv of AgBF4, however, gave a diboron complex, [OC(Me)CHC(Me)N(2,6-iPr2C6H2-4)BF2]2CH2 (6), in 18% isolated yield. All new complexes have been characterized by 1H and 13C NMR spectroscopy and complexes 2, 3, and 6 are also confirmed by X-ray diffraction.