Hydrolysis of Trimesitylgallium and Trimesitylaluminum: Structures Along a Reaction Pathway

Hydrolyses of trimesitylgallium and -aluminum were monitored by 1H NMR spectroscopy in the temperature range −60 °C to room temperature using deuterated THF as solvent. The first intermediate of the reaction using water and trimesitylgallium is the monomeric water adduct, (Mes3Ga·OH2)·2THF, 1. Elimination of mesitylene leads to the dimeric hydroxide (Mes2GaOH)2·THF, 2. Excess of water gives Mes6Ga6O4(OH)4·4THF, 3. As a result of this reaction course the corresponding hydrolysis of trimesitylaluminum leads to (Mes3Al·OH2)·nTHF, 4 and (Mes2AlOH)2·2THF, 5. The molecular structures of compounds 1, 2, and 5 have been determined by low temperature X-ray structure analysis. The Lewis acidities of the mesityl containing hydroxides are discussed and compared with those of known aryl- and alkyl aluminum and gallium hydroxides.