Synthesis and Structure of a Novel Lewis Acid−Base Adduct, (H3C)3SiN3·GaCl3, en Route to Cl2GaN3 and Its Derivatives:  Inorganic Precursors to Heteroepitaxial GaN

The formation of a novel Lewis acid−base complex between the silyl azide Si(CH3)3N3 and GaCl3 having the formula (H3C)3SiN3·GaCl3 (1) is demonstrated. The X-ray crystal structure of 1 shows that the electron-donating site is the nitrogen atom directly bonded to the organometallic group. Compound 1 crystallizes in the orthorhombic space group Pnma, with cell dimensions a = 15.823(10) Å, b = 10.010(5) Å, c = 7.403(3) Å, and Z = 4. Low-temperature decomposition of 1 via loss of (H3C)3SiCl yields Cl2GaN3 (2), which serves as the first totally inorganic (C,H-free) precursor to heteroepitaxial GaN by ultrahigh-vacuum chemical vapor deposition. A volatile monomeric Lewis acid−base adduct of 2 with trimethylamine, Cl2GaN3·N(CH3)3 (3), has also been prepared and utilized to grow high-quality GaN on Si and basal plane sapphire substrates. The valence bond model is used to analyze bond lengths in organometallic azides and related adducts.