Lewis base complexes of sila[2]aluminocenophanes

Several new sila[2]aluminocenophane Lewis base complexes are described, which were synthesized directly from the corresponding sila[2]magnesocenophane and AlX₃·base precursors. The compounds are stable at room temperature for weeks, and were characterized in solution by multinuclear NMR spectroscopy and in the solid state by single crystal X-ray diffraction. In all cases, a dynamic structure was observed in solution, due to rapid sigmatropic rearrangements. Bonding energies of the Lewis base ligands to the aluminium center were calculated to be 162.9-213.3 kJ mol^-1.