Heterometallic aluminates: alkali metals trapped by an aluminium aryloxide claw

Abstract

A series of heterometallic aluminium–alkali metal species [AlMMe₂{2,6-(MeO)₂C₆H₃O}₂]_n have been isolated for lithium, sodium and potassium. These compounds can be generated by the reaction of [AlMe₂{2,6-(MeO)₂C₆H₃O}]₂ with the metallated phenol [M{2,6-(MeO)₂C₆H₃O}]_n or through the reaction of the mixture of AlMe₃ and the appropriate alkali metal alkyl base with two equivalents of 2,6-dimethoxyphenol. In the heterometallic species obtained, the {AlMe₂{2,6-(MeO)₂C₆H₃O}₂}⁻ moiety is observed and could be described as a claw which fixes the alkali ion by the phenoxide oxygen atoms while the methoxy groups help to stabilize their coordination sphere. All compounds have been characterized by NMR spectroscopy and X-ray diffraction methods. Catalytic studies reveal that these compounds are active in ring-opening polymerization of L-lactide.