Abstract
Despite their promising potential, e.g., as ditopic, cooperatively binding Lewis acids, 9,10-dihydro-9,10-dialuminaanthracenes (DAA-R(2); R: terminal Al-bonded substituent) have remained unexplored for long due to the challenges in synthesizing the ligand-free species. We demonstrate that DAA-Me(2) is accessible via the reaction of 1,2-(Me(3)Sn)(2)C(6)H(4) with AlMe(3), producing volatile SnMe(4) as the sole byproduct. In non-coordinating solvents and in the solid state, DAA-Me(2) exists as a dimer (DAA-Me(2))(2). Treatment of (DAA-Me(2))(2) with 4 equiv. AlBr(3) cleaves the dimer, leads to quantitative Me/Br exchange, and forms the double AlBr(3) adduct DAA-Br(2)·(AlBr(3))(2). Removal of AlBr(3) with 2,2'-bipyridine gives free DAA-Br(2), which also dimerizes in the absence of bases to form (DAA-Br(2))(2). (DAA-Me(2))(2) and (DAA-Br(2))(2) readily react with mono- (e.g., pyridine) or ditopic Lewis bases (e.g., potassium pyrazolide) to afford trans-diadducts or triptycene-type frameworks. Upon addition of [nBu(4)N]Br, DAA-Br(2)·(AlBr(3))(2) undergoes selective cleavage of Al-C bonds to produce the Br(-) chelate complex of 1,2-(Br(2)Al)(2)C(6)H(4), a valuable synthon for 1,2-dideprotonated benzenes.