Synthesis and Reactivity of Amidoaluminum Hydride Compounds as Potential Precursors to AlN

Abstract

A new series of amidoaluminum hydride complexes H n Al[N(SiHMe2)2]3−n⋅NMe3 (1, n=2; 2, n=1), Al[N(SiHMe2)2]3 (3), and [H2AlN(SiHMe2)2]2 (4) were prepared by the metallation of tetramethyldisilazane (Me2HSi)2NH with either H3Al⋅NMe3 or H3Al⋅2OEt2. The molecular structures of 1 and 2 were shown by X-ray crystal structure determination to be monomeric Lewis acid-base adducts with four coordinate aluminum centers and terminal amido groups. The molecular structure of 4 was found to be a dimer with bridging disilylamides in the solid state. Attempts to obtain crystals of [H2AlN(SiMe3)2]2, a bulkier analogue of 4, led to the isolation of the unusual alumoxane μ2-(Me3Si)2 N-(AlH2)2-μ3-O-Al(H)N(SiMe3)2⋅OEt2 (6) in moderate yields. Thermolysis of 1 and 2 resulted only in the formation of ligand exchange and decomposition products, whereas thermolysis of 4 at 80°C afforded 1 equivalent of Me2SiH2 and a new species formulated as the imide complex [HAlNSiMe2H] n (7). Thermolysis of 4 in the presence of AlH3⋅NMe3 gave Me2SiH2 and 7 at a higher reaction rate even at a lower temperature.