Synthesis and structural characterisation of alkylaluminium and alkylgallium pinacolates

The influence of the steric repulsion of ligands on the structure of alkylaluminium and alkylgallium 2,3-dimethylbutane-2,3-diolates (pinacolates) has been studied. Reaction of Me3Al and pinacol afforded the compound Me5Al3[OC(CH3)2C(CH3)2O]2 (1) possessing two diolate ligands. The treatment of pinacol with the more sterically hindered tBu3Al resulted in the formation of aluminium tripinacolate tBu3Al3[OC(CH3)2C(CH3)2O]3 (2) as the only product. In contrast, the reaction of the less reactive tBu3Ga with pinacol stopped at the stage of the compound tBu3Ga2[OC(CH3)3C(CH3)2O] [OC(CH3)3C(CH3)2OH] (3), which is an intermediate product of the reaction of 1,2-diols with group 13 trialkyls. Compounds 1, 2 and 3 were crystallographically characterised.

Graphical abstractThe treatment of pinacol with tBu3Al resulted in the formation of aluminium tripinacolate tBu3Al3[OC(CH3)2C(CH3)2O]3 (2) as the only product. In contrast, the reaction of the less reactive tBu3Ga with pinacol stopped at the stage of the compound tBu3Ga2[OC(CH3)3C(CH3)2O] [OC(CH3)3C(CH3)2OH] (3), which is an intermediate product of the reaction of 1,2-diols with group 13 trialkyls.Figure optionsDownload full-size imageDownload as PowerPoint slide