ETHERATE FORMATION IN ORGANOALUMINUM COMPOUNDS . COMPLEX-FORMATION TENDENCY IN A SERIES OF TRIALKYLALUMINUM DIALKYLALUMINUM CHLORIDE ALKYLALUMINUM DICHLORIDE AND ALUMINUM CHLORIDE ARYL ETHERATES

Cryoscopic measurements in benzene at 5° have been used to study etherate formation within the series R3Al, R2AlCl, RAlCl2, and AlCl3 (R = Me, Et, n-Pr, n-Bu, and i-Bu). In Ph2O, PhSMe, and PhOMe systems, the order of increasing complex formation is R2AlCl < R3Al < RAlCl2 < AlCl3. Some of the etherates of RAlCl2 and all AlCl3 etherates show an apparent intermolecular association. For a given complex type, increasing etherate dissociation occurs as the length of the alkyl group bound to aluminum increases. The phenomena are explained in terms of Lewis acid-base effects. Neither Ph2O nor PhOMe forms a complex with (i-Bu)2AlH.