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.