Collect. Czech. Chem. Commun. 2003, 68, 1119-1130

Polymerization of Propene with Modified Constrained Geometry Complexes. Double-Bond Isomerization in Pendant Alkenyl Groups Attached to Cyclopentadienyl Ligands

Oetze K. B. Staala, Dirk J. Beetstraa, Andries P. Jekela, Bart Hessena,*, Jan H. Teubena,*, Petr Štěpničkab, Róbert Gyepesb, Michal Horáčekc, Jiří Pinkasc and Karel Machc,*

a Centre for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry and Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
b Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
c J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8, Czech Republic


Polymerization of propene with dimethylsilylene-bridged (amidocyclopentadienyl)dichlorotitanium(IV) complexes [TiCl25-1-(t-BuSiMe2N-κN)-2,3,4-Me3-5-R-C5}], where R = Me (1), H (2), Ph (3), 4-fluorophenyl (4), but-2-en-2-yl (5), and butyl (6), combined with excess methylaluminoxane revealed a moderate effect of the substituent R on the catalyst activity and the molecular weight of polypropene. The asymmetric substitution in the position adjacent to the bridging carbon atom resulted in polymer yields decreasing in the order 1 > 6 > 35 > 4 > 2 while polymers with the molecular weights (Mw) close to 2.5 × 105 for 1, 3, and 4, 1.5 × 105 for 5 and 6, and 7.5 × 104 for 2 were obtained. The 13C NMR analysis of the polymers has shown that atactic polypropene is slightly enriched with syndiotactic triads for all the catalysts. Investigation of the crystal structure of 5 by X-ray crystallography revealed that the double bond in but-3-en-2-yl had shifted to an internal position to give the isomeric, but-2-en-2-yl-substituted complex. Likewise, the spectroscopic data for complex 7 prepared from the ligand containing but-3-en-1-yl substituent, indicate the absence of terminal double bond.

Keywords: Titanium; CGC catalysts; Propene polymerization; Substituent effects; Double-bond isomerization; X-Ray diffraction; NMR spectroscopy; Half-sandwich complexes.

References: 24 live references.