Solution Structure and Reactivity with Metallocenes of AlMe2 F: Mimicking Cation-Anion Interactions in Metallocenium-Methylalumoxane Inner-Sphere Ion Pairs.

The solution structure of AlMe2 F 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, AlMe2 F gives rise to a complex equilibrium of oligomeric species, including a heterocubane [(Me2 Al)4 F4 ] 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)ZrMe(δ+) (μ-F)(AlMe2 F)n AlMe3(δ-) ] inner-sphere ion pairs through successive insertions/deinsertions of AlMe2 F units into the Zr⋅⋅⋅(μ-F) bond.