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EPR Identification of Zr(III) Complexes Formed upon Interaction of (2‐PhInd) 2 ZrCl 2 and rac ‐Me 2 Si(1‐Ind) 2 ZrCl 2 with MAO and MMAO
Author(s) -
Lyakin Oleg Y.,
Bryliakov Konstantin P.,
Panchenko Valenti.,
Semikolenova Nina V.,
Zakharov Vladimir A.,
Talsi Evgenii P.
Publication year - 2007
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200700066
Subject(s) - electron paramagnetic resonance , zirconium , chemistry , monomer , catalysis , diamagnetism , crystallography , polymer chemistry , stereochemistry , medicinal chemistry , inorganic chemistry , polymer , nuclear magnetic resonance , organic chemistry , magnetic field , physics , quantum mechanics
Reactions of 1 and 2 with MAO and MMAO were monitored by EPR. It was found that MMAO is a stronger reducing agent than MAO. 1 is more prone to reduction than 2 . The reduction of Zr IV to Zr III seems to be the essential pathway of some zirconocene catalysts' deactivation. Zr III species with the following proposed structures can be identified in the 1 /MMAO system: (2‐PhInd) 2 Zr III ( i Bu), (2‐PhInd) 2 Zr III ( µ ‐Cl) 2 Al i Bu 2 , (2‐PhInd) 2 Zr III ( µ ‐Cl)( i Bu)Al i Bu 2 , and [(2‐PhInd) 2 Zr III ] + [Me‐MAO] − . The degree of reduction of Zr IV species determined by EPR in the catalytic system 2 /MMAO can be masked by the formation of diamagnetic Zr III /Zr III dimers. Addition of monomers to the 2 /MAO system promotes reduction ot the zirconium species.