Synthesis, X-ray crystal structure, and stability of novel trialkylalane-triorganylbismuthane adducts

Reactions of trialkylalanes AlR3 (R = Me, Et, tBu) and triorganylbismuthane s BiR ' (3) (R ' = iPr, SiMe3) were performed and the products investigated both in solution and in the solid state. Et3Al-Bi(SiMe3)(3) (2), tBu(3)Al- Bi(SiMe3)(3) (3), and tBu(3)Al-Bi(iPr)(3) (6) are stable Lewis acid-base ad ducts in pure form while only 3 and 6 are adducts in solution, Their dissoc iation enthalpies, as determined by temperature-dependent NMR spectroscopy, were estimated to 6.3 (3) and 6.9 kcal/mol (6). In contrast, Me3Al-Bi(SiMe 3)(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 (H-1, C-13), mass spectrometry, and elemen tal analysis. In addition, the crystal structures of 2 and 6 were determine d by single-crystal X-ray diffraction. Compounds 2 and 6 are the first stru cturally characterized alane-triorganylbismuthane Lewis acid-base adducts.