Solution Structure and Reactivity with Metallocenes of AlMe2F: Mimicking Cation–Anion Interactions in Metallocenium–Methylalumoxane Inner‐Sphere Ion Pairs

• Published in: Angewandte Chemie International Edition Vol. 56; no. 45; pp. 14227 - 14231
• Main Authors: Oliva, Leone, Oliva, Patrizia, Galdi, Nunzia, Pellecchia, Claudio, Sian, Leonardo, Macchioni, Alceo, Zuccaccia, Cristiano
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 06-11-2017
• Edition: International ed. in English
• Subjects: aluminum fluoride; Amine oxidase (flavin-containing); Ion pairs; Metallocenes; methylalumoxane; Mimicry; NMR; NMR spectroscopy; Nuclear magnetic resonance; olefin polymerization; Polymerization; Zirconium
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201707194

The solution structure of AlMe2F and its reactivity with a prototypical ansa‐metallocene have been investigated by advanced NMR techniques, in an attempt to indirectly shed some light on the structure and working principles of methylalumoxane (MAO) mixtures in olefin polymerization. In solution, AlMe2F gives rise to a complex equilibrium of oligomeric species, including a heterocubane [(Me2Al)4F4] tetramer, resembling the behavior of MAO. This complex mixture reacts with (ETH)ZrMe2 (ETH=rac‐[ethylenebis(4,5,6,7‐tetrahydro‐1‐indenyl)]) to afford [(ETH)ZrMeδ+(μ‐F)(AlMe2F)nAlMe3δ−] inner‐sphere ion pairs through successive insertions/deinsertions of AlMe2F units into the Zr⋅⋅⋅(μ‐F) bond.
One after the other: AlMe2F mimics the behavior of AlMeO units in methylalumoxane (MAO) mixtures and can thus be used to simulate metallocene/MAO interactions in [metalloceniumδ+⋅⋅⋅MAOδ−] polymerization catalysts. Mixtures of AlMe2F and metallocenes contain several inner‐sphere ion pairs that equilibrate via successive insertions/deinsertions of AlMe2F units into the Zr⋅⋅⋅(μ‐F) bonds.