VARIATION OF POLY(PROPYLENE) MICROTACTICITY BY CATALYST SELECTION

The polymerization of propylene with use of soluble catalysts derived from rac-(1,2-ethylenebis(eta-5-3-alkylcyclopentadienyl))zirconium dichlorides (rac-1) and their corresponding meso isomers (meso-1), in combination with methylaluminoxane cocatalyst, was studied. The polymerization activity of catalysts derived from compounds rac-1 and meso-1 was somewhat lower than that reported for the well-studied catalysts of this structural type rac-(ethylenebis(eta-5-indenyl)))zirconium and rac-(ethylenebis(eta-5-tetrahydroindenyl))zirconium dichlorides (2 and 3, respectively); however, the degree of microtacticity of the poly(propylene) produced was higher, as determined by C-13 NMR spectroscopy. The polymerization activity of the meso compounds (meso-1) was lower than that of their racemic counterparts. Finally, meso-(ethylenebis(eta-5-tetrahydroindenyl))zirconium dichloride (4) was isolated in pure form as a minor product from the preparation of the racemic isomer. This compound is less active than its racemic diastereomer 3 and produces atactic poly(propylene). Compound 4 was characterized by a single-crystal X-ray diffraction analysis: space group P2(1)/c; Z = 4; a = 12.051 (2) angstrom, b = 15.184 (3) angstrom, c = 9.939 (2) angstrom, beta = 92.94 (1)degrees; V = 1816.3 (5) angstrom 3; R = 0.0256, R(W) = 0.0299 for 2784 unique reflections with I > 3-sigma(I).