Synthesis, X-ray Crystal Structure, and Stability of Novel Trialkylalane−Triorganylbismuthane Adducts

Abstract

Reactions of trialkylalanes AlR3 (R = Me, Et, tBu) and triorganylbismuthanes BiR′3 (R′ = iPr, SiMe3) were performed and the products investigated both in solution and in the solid state. Et3Al−Bi(SiMe3)3 (2), tBu3Al−Bi(SiMe3)3 (3), and tBu3Al−Bi(iPr)3 (6) are stable Lewis acid−base adducts in pure form while only 3 and 6 are adducts in solution. Their dissociation enthalpies, as determined by temperature-dependent NMR spectroscopy, were estimated to 6.3 (3) and 6.9 kcal/mol (6). In contrast, Me3Al−Bi(SiMe3)3 (1), Et3Al−Bi(SiMe3)3 (2), Me3Al−Bi(iPr)3 (4), and Et3Al−Bi(iPr)3 (5) are fully dissociated in solution. Compounds 1−6 were characterized by multinuclear NMR spectroscopy (1H, 13C), mass spectrometry, and elemental analysis. In addition, the crystal structures of 2 and 6 were determined by single-crystal X-ray diffraction. Compounds 2 and 6 are the first structurally characterized alane−triorganylbismuthane Lewis acid−base adducts.