Lewis Base Adduct Stabilized Organogallium Azides: Synthesis and Dynamic NMR Spectroscopic Studies of Novel Precursors to Gallium Nitride and Role of Ammonia as Reactive Carrier Gas

Abstract

The organogallium azides (N3)2-a(R)aGa[(CH2)3NMe2]1-a (1a-c: R = CH3, tBu; a = 0, 1), (Et)(N3)2Ga (2a), and (Et)(N3)2Ga·L (2b−d: L = thf, H2NtBu, py, NC7H13) are quantitatively synthesized by salt metathesis from the chloro species (Cl)2-a(R)aGa[(CH2)3NMe2]1-a (a = 0, 1) or EtGaCl2 and sodium azide. The preferential ammonolysis of Ga−N3 bonds for [Et2Ga(N3)]3 (4) and 1 and 2 is demonstrated; e.g. the dimer Et2Ga(μ-NH2)(μ-N3)GaEt2 (3) was obtained. The characterization of these compounds by means of elemental analysis, 1H-, 13C-, 14N-, and 15N-NMR, MS, and infrared ν(N3) data is reported. The dynamics of the intramolecular Ga−N donor−acceptor bonded heterocycle and the azide group is discussed on the basis of variable-temperature NMR data. The barrier of activation of the bimolecular azide exchange process for (N3)2Ga[(CH2)3NMe2] (1c) amounts about 50 kJ·mol-1. The role of ammonia as reactive carrier gas for low-pressure metal organic chemical vapor deposition (MOCVD) of GaN with 1c as precursor is discussed.