Authors
Aleksi Vähäkangas, Scott Collins, Mikko Linnolahti
Published in
Dalton transactions (Cambridge, England : 2003). Aug 17, 2026. Epub Aug 17, 2026.
Abstract
Theoretical calculations involving new sheet models (MeAlO)16(Me3Al)7 (16,7) show these aluminoxane-based activators function to activate metallocene catalysts by [Me2Al]+ abstraction. However, this process involves more steps than the conventional methide abstraction. Based on MN15/def2-TZVP calculations, the formation of outer-sphere ion-pairs (OSIP) [rac-Me2Si(η5-indenyl)2ZrMe2AlMe2][16,6] ([SBIZrMe2AlMe2][16,6] 2) would be favorable in toluene. These outer-sphere ion-pairs are favored by the Me3Al-dissociation equilibrium to the extent that detecting contact ion-pairs SBIZrMe-μ-Me-16,6 (1) would be rather difficult, in disagreement with many spectroscopic experiments. This discrepancy can be explained by invoking competing catalyst activation that involves 16,7 sheets vs. other reactive components of MAO that function via methide abstraction (neutral sheets like 16,6 or especially large cages like 23,7). The key difference however, is that the ion-pairs formed via methide abstraction would have to be largely unreactive to olefin insertion, and this is certainly true of either sheet 16,6 or cage 23,7. Contact ion-pairs SBIZrMe-μ-Me-16,6 (1) derived from 16,7 sheets have very different reactivities towards monomer insertion; we explore the ramifications of this two-state behavior in the context of propagation competing with dormant vs. active ion-pair interconversion.
PMID:
42606921
Bibliographic data and abstract were imported from PubMed on 18 Aug 2026.
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