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Probing the Coordinative Unsaturation and Local Environment of Ti 3+ Sites in an Activated High‐Yield Ziegler–Natta Catalyst
Author(s) -
Morra Elena,
Giamello Elio,
Van Doorslaer Sabine,
Antinucci Giuseppe,
D'Amore Maddalena,
Busico Vincenzo,
Chiesa Mario
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201412052
Subject(s) - catalysis , degree of unsaturation , yield (engineering) , electron paramagnetic resonance , chemistry , hyperfine structure , ziegler–natta catalyst , reactivity (psychology) , olefin fiber , molecule , olefin polymerization , quadrupole , polymer chemistry , materials science , nuclear magnetic resonance , organic chemistry , physics , ethylene , atomic physics , medicine , alternative medicine , pathology , metallurgy
The typical activation of a fourth generation Ziegler–Natta catalyst TiCl 4 /MgCl 2 /phthalate with triethyl aluminum generates Ti 3+ centers that are investigated by multi‐frequency continuous wave and pulse EPR methods. Two families of isolated, molecule‐like Ti 3+ species have been identified. A comparison of the experimentally derived g tensors and 35,37 Cl hyperfine and nuclear‐quadrupole tensors with DFT‐computed values suggests that the dominant EPR‐active Ti 3+ species is located on MgCl 2 (110) surfaces (or equivalent MgCl 2 terminations with tetra‐coordinated Mg). O 2 reactivity tests show that a fraction of these Ti sites is chemically accessible, an important result in view of the search for the true catalyst active site in olefin polymerization.