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Stepwise Synthesis of Carboxyalumoxanes through Well-Defined Organoaluminum and Organogallium Carboxylatohydroxides Obtained by Controlled Hydrolysis

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Alumoxanes are compounds of composition (R 2 AlOAlR 2 ) n and (RAlO) n that are traditionally obtained by controlled hydrolysis of aluminum trialkyls, although nonhydrolytic approaches to alumoxanes are also used. To reduce the reactivity of alumoxanes in contact with air, in the 1990s, researchers attempted to replace alkyl groups with other substituents, leading to the synthesis of carboxyalumoxanes with bulky alkyl groups. In this paper, we report on the study of carboxy methylalumoxane synthesis and structural characterization. We present a two-step synthesis of carboxyalumoxane containing the ( t -Bu 2 Al) 2 OAlMe 2 alumoxane unit. The method involves the synthesis of carboxylatoaluminum hydroxides by the reaction of t -Bu 3 Al with carboxylic acid and water with a molar ratio of reagents of 2:1:1 in the first step, followed by the reaction with Me 3 Al. On the other hand, the one-step reaction of Me 3 Al with carboxylic acid and water in a molar ratio of 3:1:1 leads to the formation of a carboxy methylalumoxane incorporating a neutral Me 6 Al 4 O 2 scaffold trapped by two carboxylate units. The reaction of carboxylatogallium hydroxides with Me 3 Al occurred with the exchange of t -Bu 2 Ga groups for Me 2 Al, leading to the formation of carboxyalumoxanes with a Me 6 Al 4 O 2 scaffold. The molecular and crystal structures of the compounds were determined via single-crystal X-ray diffraction (SCXRD) crystallography.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.5c00367