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With the homogeneous Ziegler-Natta catalyst based on chiral metallocenes/methylalumoxane highly isotactic polypropylene could be prepared. The catalysts can be separated into the optical active enantiomers. Even longer chained α-olefins as butene-1, pentene-1, or hexene-1, give isotactic polymers. Among the polymer features molecular weight and molecular weight distribution, solubility in toluene, melting point, density, and x-ray crystallinity as well as macrotacticity have been examined. Except for polyhexene all polymers investigated arrange in a stable helical conformation. Oligomers of butene -1 and pentene-1 show an optical rotation.Among the great number of Ziegler-type catalysts, Vanden berg (1) examined at a very early stage the heterogeneous titanium trichloride system, especially for synthesizing isotactic polypropylene. Homogeneous systems have been preferentially studied in order to understand the elementary steps of the polymerization which is simpler in soluble systems than in heterogeneous ones. The situa tion has changed since in recent years a homogeneous cat alyst based on metallocene and aluminoxane was discovered which is very active and also interesting for industrial uses (2-3). In some cases special polymers could be syn thesized only with soluble catalysts (4).Breslow (5) discovered that bis(cyclopentadienyl)-titanium(IV) compounds which are well soluble in aromatic hydrocarbons, could be used instead of titanium tetra chloride as the transition metal compound together with aluminum alkyls for ethylene polymerization. Subsequent research on this and other systems with various alkyl

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