Synthesis and Characterization of Novel Siloxyalanes

The siloxyalanes [(Et3SiOAlH2)2AlH3]n (1), [tBuMe2SiOAlH2]2 (2), [(tBuMe2SiO)2AlH]2 (3), and [(tBuMe2SiO)5Al2H] (4) have been synthesized and characterized by IR and NMR spectroscopic means. By X-ray diffraction studies on single crystals it was established that molecule 1 is a coordination polymer in the solid state with tetrameric units [Et3SiOAlH2]4 (almost linear Al···Al···Al···Al arrangement) interlinked by Al2H6 groups to form a one-dimensional chain (formal description with neutral building blocks). Compound 3 is dimeric through Al−O contacts with a cis orientation of the hydride ligands with respect to the central Al2O2 cycle. Compound 4 may be described as a double adduct between the two Lewis acid−base compounds (tBuMe2SiO)2AlH and Al(OSiMe2tBu)3. The bulkiness of the substituents on the silicon atoms plays an important role in the aggregation of the compounds. Hydride bridging between molecules or within the molecular entities is only observed in compound 1.