EPR Identification of Zr(III) Complexes Formed upon Interaction of (2-PhInd)2ZrCl2 and rac-Me2Si(1-Ind)2ZrCl2 with MAO and MMAO

✍ Scribed by Oleg Y. Lyakin; Konstantin P. Bryliakov; Valentina N. Panchenko; Nina V. Semikolenova; Vladimir A. Zakharov; Evgenii P. Talsi

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 196 KB
• Volume: 208
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200700066

✦ Synopsis

Abstract

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.

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