Probing the Coordinative Unsaturation and Local Environment of Ti super(3+)Sites in an Activated High-Yield Ziegler-Natta Catalyst

The typical activation of a fourth generation Ziegler-Natta catalyst TiCl sub(4)/MgCl sub(2)/phthalate with triethyl aluminum generates Ti super(3+)centers that are investigated by multi-frequency continuous wave and pulse EPR methods. Two families of isolated, molecule-like Ti super(3+)species have...

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Bibliographic Details
Published in:Angewandte Chemie 2015-04, Vol.127 (16), p.4939-4942
Main Authors: Morra, Elena, Giamello, Elio, VanDoorslaer, Sabine, Antinucci, Giuseppe, D'Amore, Maddalena, Busico, Vincenzo, Chiesa, Mario
Format: Article
Language:English
Subjects:
Accessibility
Activation
Aluminum
Olefins
Polymerization
Searching
Tensors
Terminations
Ziegler-Natta catalysts
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Summary:The typical activation of a fourth generation Ziegler-Natta catalyst TiCl sub(4)/MgCl sub(2)/phthalate with triethyl aluminum generates Ti super(3+)centers that are investigated by multi-frequency continuous wave and pulse EPR methods. Two families of isolated, molecule-like Ti super(3+)species have been identified. A comparison of the experimentally derived gtensors and super(35,37)Cl hyperfine and nuclear-quadrupole tensors with DFT-computed values suggests that the dominant EPR-active Ti super(3+)species is located on MgCl sub(2)(110) surfaces (or equivalent MgCl sub(2) terminations with tetra-coordinated Mg). O sub(2) reactivity tests show that a fraction of these Tisites is chemically accessible, an important result in view of the search for the true catalyst active site in olefin polymerization.Original Abstract: Ausgekluegelte EPR-Experimente wurden verwendet, um die Koordinationsumgebung der Ti super(3+)-Zentren in einem aktivierten MgCl sub(2)-fixierten industriellen Ziegler-Natta(ZN)-Katalysator zu ermitteln. Die Ergebnisse liefern die erste detaillierte Charakterisierung potenzieller katalytisch aktiver Zentren in einem industriellen ZN-Katalysator. Gruen=Cl super(-), gelb=Mg super(2+).
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201412052