Hydrolysis of Trimesitylgallium and Trimesitylaluminum:  Structures Along a Reaction Pathway

Hydrolyses of trimesitylgallium and -aluminum were monitored by 1 H 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, (Mes 3 Ga·OH 2 )·2THF, 1 . Elimination of mesitylene leads to the dimeric hydroxide (Mes 2 GaOH) 2 ·THF, 2 . Excess of water gives Mes 6 Ga 6 O 4 (OH) 4 ·4THF, 3 . As a result of this reaction course the corresponding hydrolysis of trimesitylaluminum leads to (Mes 3 Al·OH 2 )· n THF, 4 and (Mes 2 AlOH) 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.