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Oxygen‐Containing, Asymmetric “Dual‐Side” Zirconocenes: Investigations on a Reversible Chain Transfer to Aluminum
Author(s) -
Kukral Jürgen,
Lehmus Petri,
Klinga Martti,
Leskelä Markku,
Rieger Bernhard
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200206)2002:6<1349::aid-ejic1349>3.0.co;2-7
Subject(s) - chemistry , dimethylsilane , ethylenedioxy , zirconium , monomer , catalysis , polymer chemistry , chain transfer , polymerization , propene , oxygen , polymer , chain termination , inorganic chemistry , organic chemistry , radical polymerization , alkyl
A series of new oxygen‐substituted, asymmetric zirconocene dichlorides ( rac ‐{1‐[5,6‐(ethylenedioxy)‐2‐methyl‐1‐η 5 ‐indenyl]‐2‐(9‐η 5 ‐fluorenyl)ethane}zirconium dichloride ( 3a ), rac {1‐[5,6‐(ethylenedioxy)‐2‐methyl‐1‐η 5 ‐indenyl]‐2‐(9‐η 5 ‐fluorenyl)ethane}dimethylzirconium ( 3b ) and rac ‐{[5,6‐ethylenedioxy)‐2‐methyl‐1‐η 5 ‐indenyl](9‐η 5 ‐fluorenyl)dimethylsilane}zirconium dichloride ( 3c )} have been prepared and their polymerization behavior was investigated in dependence of monomer concentration, temperature and catalyst activation. The presence of oxygen substituents on the indenyl ring results in a strong increase of polymerization activities and also of polymer molecular weights with decreasing Al/Zr ratio. Significantly higher molecular masses and activities were found for the dimethyl complex 3b after activation with [(C 6 H 5 ) 3 C + ][(C 6 F 5 ) 4 B − ] deriving from the absence of chain transfer to aluminum and higher concentration of active catalyst species. The mechanism of stereoerror formation of the oxygen‐containing C 1 ‐symmetric catalyst was investigated by deuterium labeling studies on propene monomers. The results are discussed on the basis of a reversible chain transfer to aluminum.