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Published April 12, 2004 | Supplemental Material
Journal Article Open

Highly Stereoregular Syndiotactic Polypropylene Formation with Metallocene Catalysts via Influence of Distal Ligand Substituents


Highly stereoregular syndiotactic polypropylene is obtained with the catalyst systems Ph_2C(Oct)(C_5H_4)ZrCl_2/MAO (8/MAO) (Oct = octamethyloctahydrodibenzofluorenyl; MAO = methylaluminoxane) and Me_2C(Oct)(C_5H_4)ZrCl_2/MAO (12/MAO). The syndiotactic polypropylenes obtained are largely devoid of stereoerrors by ^(13)C NMR analysis ([r] > 98%), and melting temperatures as high as 153 or 154 °C (from 8 and 12, respectively) are found for the thermally quenched polymers (without annealing). A related hafnium catalytic system, Ph_2C(Tet)(C_5H_4)HfCl_2/MAO (11/MAO) (Tet = tetramethyltetrahydrobenzofluorenyl), was found to be the most syndioselective of the hafnocenes tested (T_m = 141 °C). The metallocene dichloride precatalysts represent the first examples of transition metal complexes containing the Oct or Tet ligands. Reported are the solid state crystal structures of 8, the diprotio ligand precursor of 8(Ph_2C(OctH)(C_5H_5)), and the zirconium analogue of 11, Ph_2C(Tet)(C_5H_4)ZrCl_2 (10). Distal ligand influences are thus demonstrated to have a dramatic effect on polymer stereochemistry.

Additional Information

© 2004 American Chemical Society. Received May 6, 2003. Publication Date (Web): March 18, 2004. This work has been funded by the USDOE Office of Basic Energy Sciences (Grant No. DE-FG03-88ER13431) and by a DOD National Defense Science and Engineering Fellowship awarded to S.M. The authors thank Dr. Michael Day and Mr. Lawrence Henling for obtaining the X-ray crystal structures. The authors also thank Dr. Terry Burkhardt at ExxonMobil for providing molecular weight data. Dr. Luigi Resconi at Montell Polyolefins (now Basell Polyolefins) kindly provided polymer analysis of the sample from entry 15.

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