Structure of methylaluminoxane (MAO): Extractable [Al(CH 3 ) 2 ] + for precatalyst activation

Methylaluminoxane (MAO) is used as a precatalyst activator for million ton-scale production of commercial polyolefins, but its precise structure and associated activation mechanisms have been a fundamental research puzzle for more than 40 years. We report here the crystallographic characterization o...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2024-06, Vol.384 (6703), p.1424-1428
Main Authors: Luo, Lubin, Younker, Jarod M, Zabula, Alexander V
Format: Article
Language:English
Subjects:
Aluminum
Aluminum compounds
Amine oxidase (flavin-containing)
Catalysts
Crystallization
Plastics industry
Polymerization
Quantum chemistry
Structural analysis
Two dimensional analysis
X-ray diffraction
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Summary:Methylaluminoxane (MAO) is used as a precatalyst activator for million ton-scale production of commercial polyolefins, but its precise structure and associated activation mechanisms have been a fundamental research puzzle for more than 40 years. We report here the crystallographic characterization of an active MAO component, which reveals a discrete two-dimensional sheet cluster [Al O (CH ) ][Al(CH ) ] featuring two trimethylaluminum units, Al(CH ) , coordinated to two unsaturated aluminum sites. Our structural data are consistent with the hypothesis that the active sites bear coordinated Al(CH ) and provide [Al(CH ) ] for precatalyst activation. Quantum chemical calculations revealed the most preferred sites for [Al(CH ) ] abstraction (a change in Gibbs free energy of 0.0 kilocalories per mole). Olefin polymerization tests on metallocenes activated with the crystallized MAO show higher activities than with the commercial MAO.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.adm7305