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

The organogallium azides (N-3)(2-a)(R)(a)Ga[(CH2)(3)NMe(2)](1-a) (1a-c: R = CH3, (t)Bu; a = 0, 1), (Et)(N-3)(2)Ga (2a), and (Et)(N-3)(2)Ga . L(2b-d: L = thf, H(2)N(t)Bu, py, NC7H13) are quantitatively synthesized by salt metathesis from the chloro species (Cl)(2-a)(R)(a)Ga[(CH2)(3)NMe(2)](1-a) (a = 0, 1) or EtGaCl(2) and sodium azide. The preferential ammonolysis of Ga-N-3 bonds for [Et(2)Ga(N-3)](3) (4) and 1 and 2 is demonstrated; e.g. the dimer Et(2)Ga(mu-NH2)(mu-N-3)GaEt(2) (3) was obtained. The characterization of these compounds by means of elemental analysis, H-1-, C-13-, N-14-, and N-15-NMR, MS, and infrared nu(N-3) 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 (N-3)(2)Ga[(CH2)(3)NMe(2)] (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.