Syntheses and Structural Characterization of a LAl(N₃)N[μ-Si(N₃)(<i>t</i>Bu)]₂NAl(N₃)L and a Monomeric Aluminum Hydride Amide LAlH(NHAr) (L = HC[(CMe)(NAr)]₂, Ar = 2,6-<i>i</i>Pr₂C₆H₃)

Reactions between the aluminum(I) monomer LAl (L = HC[(CMe)(NAr)]2, Ar = 2,6-iPr2C6H3) and organic azides (RN3, R = C10H15 (adamantyl), Ph3Si; tBuSi(N3)3) are reported. LAl reacted with the bulky azide RN3 in toluene in a temperature range of −50 to 25 °C, resulting in the compound LAl[(NR)2N2] (R = C10H15 (1), Ph3Si (2)) instead of the expected AlN multiple bond species, while the reaction with tBuSi(N3)3 gave LAl(N3)N[(μ-Si(N3)(tBu)]2NAl(N3)L (3). Compounds 1−3 have been fully characterized by mass spectrometry and IR and multinuclear NMR spectroscopy (1H, 13C, and 29Si) as well as by single-crystal X-ray crystallography. The structural analysis of 1 and 2 reveals an AlN4 planar five-membered ring compound, suggesting a [2 + 3] cycloaddition of the AlN multiple bond species with a molecule of RN3 despite the steric bulk of the L and R substituents. Compound 3 shows a bonding of the N3 group to the Al and a formation of the N2Si2 central core, implying the migration of N3 and a [2 + 2] cycloaddition in the reaction sequence. In addition, the solvent-free reaction of an aluminum dihydride LAlH2 with ArNH2 was also investigated at elevated temperatures (150−290 °C), and a monomeric aluminum hydride amide, LAlH(NHAr) (4), was obtained as the only isolable product. The Al−H and N−H groups of 4 are shown in the IR and 1H NMR spectra. The corresponding X-ray structural analysis exhibits the Al−H and N−H bonds that are nearly arranged in position trans to the Al−NNHAr bond.