Methylaluminoxane, commonly called MAO, is a mixture of
organoaluminium compounds with the approximate formula (Al(CH3)O)n.[1] It is usually encountered as a solution in (
aromatic)
solvents, commonly
toluene but also
xylene,
cumene, or
mesitylene,[2] Used in large excess, it activates precatalysts for alkene polymerization.[3][4]
MAO serves multiple functions in the activation process. First it alkylates the metal-chloride pre-catalyst species giving Ti/Zr-methyl intermediates. Second, it abstracts a ligand from the methylated precatalysts, forming an electrophilic, coordinatively unsaturated catalysts that can undergo ethylene insertion. This activated catalyst is an
ion pair between a cationic catalyst and an weakly basic MAO-derived anion. [10] MAO also functions as
scavenger for protic impurities.
^Chen, E. Y.-X.; Marks, T. J. (2000). "Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure-Activity Relationships". Chem. Rev.100 (4): 1391–1434.
doi:
10.1021/cr980462j.
PMID11749269.
^Kaminsky, Walter (1998). "Highly active metallocene catalysts for olefin polymerization". Journal of the Chemical Society, Dalton Transactions (9): 1413–1418.
doi:
10.1039/A800056E.
^Lacramioara Negureanu; Randall W. Hall; Leslie G. Butler & Larry A. Simeral (2006). "Methyaluminoxane (MAO) Polymerization Mechanism and Kinetic Model from Ab Initio Molecular Dynamics and Electronic Structure Calculations". J. Am. Chem. Soc.128 (51): 16816–16826.
doi:
10.1021/ja064545q.
PMID17177432.
^Harlan, C. Jeff; Mason, Mark R.; Barron, Andrew R. (1994). "Tert-Butylaluminum Hydroxides and Oxides: Structural Relationship between Alkylalumoxanes and Alumina Gels". Organometallics. 13 (8): 2957–2969.
doi:
10.1021/om00020a011.
^Mason, Mark R.; Smith, Janna M.; Bott, Simon G.; Barron, Andrew R. (1993). "Hydrolysis of tri-tert-Butylaluminum: The First Structural Characterization of Alkylalumoxanes [(R2Al)2O]n and (RAlO)n". Journal of the American Chemical Society. 115 (12): 4971–4984.
doi:
10.1021/ja00065a005.
^A. Andresen; H.G. Cordes; J. Herwig; W. Kaminsky; A. Merck; R. Mottweiler; J. Pein; H. Sinn; H.J. Vollmer (1976). "Halogen-free Soluble Ziegler-Catalysts for the Polymerization of Ethylene". Angew. Chem. Int. Ed.15 (10): 630.
doi:
10.1002/anie.197606301.