Synthesis of ultra-high purity trialkylgallium MOVPE precursors. Crystal structures of triethylgallium and triisopropylgallium adducts with macrocyclic tertiary amines

A synthesis and purification route has been developed for base-free trialkylgallium compounds which avoids the use of traditional ether solvents. The R₃Ga compound (R = Et, Pr(i)) is synthesised in triethylamine, NEt₃, which leads to the adducts R₃Ga(NEt₃). The NEt₃ ligand can be readily displaced by the addition of low volatility bidentate, tetradentate or hexadentate tertiary amines to give adducts of the type (R₃Ga)(x)L (x= 2, 4, 6), from which base-free R₃Ga compounds are obtained by mild thermal dissociation. The synthesis and characterisation of these adducts are described and crystal structures reported for the adducts between R₃Ga (R = Et, Pr(i)) and the multidentate macrocyclic amines 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane and 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane. These are the first reported structural studies of the Et₃Ga and Pr(i)₃Ga molecules in the solid state.