Syntheses and structural characterization of a LAl(N₃)N[μ- Si(N₃)tBu]₂NAl(N₃)L and a monomeric aluminum hydride amide LAlH(NHAr) (L = HC[(CMe)(NAr)]₂, Ar = 2,6-iPr ₂C₆H₃)

Reactions between the aluminum(I) monomer LA1 (L = HC[(CMe)(NAr)] ₂, Ar = 2,6-iPr₂C₆H₃) and organic azides (RN₃, R = C₁₀H₁₅ (adamantyl), Ph ₃Si; tBuSi(N₃)₃) are reported. LA1 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 AI=N multiple bond species, while the reaction with tBuSi(N₃) ₃ gave LAl(N₃)N[(μSi-(N₃)(tBu)] ₂NAl(N₃)L (3). Compounds 1-8 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 A1N₄ 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 N ₃ 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 LA1H₂ with ArNH₂ was also investigated at elevated temperatures (150-290°C), and a monomeric aluminum hydride amide, LA1H-(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-N_NHAr bond.