A STEROID-SUBSTITUTED GROUP-4 BENT METALLOCENE SYSTEM - SYNTHESIS, STRUCTURAL FEATURES AND ITS USE IN CATALYTIC PROPENE POLYMERIZATION

3-Methoxyestra-1,3,5(10)-trien-16-one (6) was converted to the corresp onding fulvene (7). Methyllithium was added and the resulting (16alpha -methylestratrienyl)cyclopentadiene 8 separated by chromatography. Dep rotonation gave the (16alpha-methylestratrienyl-C5H4)Li reagent 9 that was added to 0.5 molar equivalents of ZrCl4(THF)2 to yield 5(10)-trie n-16beta-yll)cyclopentadienyl]-zirconium dichloride (10, 45%). Complex 10 was activated by treatment with an excess of methylalumoxane. The resulting homogeneous Ziegler-type catalyst was employed for stereosel ective propene polymerization. In the temperature range of -50 to -10- degrees-C partly isotactic polypropylene was obtained. A detailed anal ysis has revealed that stereocontrol is effected by a combination of e nantiomorphic site and chain-end control. Compounds 7 and 10 were char acterized by X-ray diffraction.