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[(CH 2 ) 3 NMe 2 ] 1 - a ( 1a-c: R = CH 3, 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, NC 7 H 13 ) are quantitatively synthesized by salt metathesis from the chloro species (Cl) 2 - a (R) a Ga[(CH 2 ) 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(μ-NH 2 )(μ-N 3 )GaEt 2 ( 3 ) was obtained. The characterization of these compounds by means of elemental analysis, 1 H-, 13 C-, 14 N-, and 15 N-NMR, MS, and infrared ν(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[(CH 2 ) 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.