Abstract: The novel metallocenes of the formula I ##STR1## in which, preferably, M.sup.1 is Zr or Hf, R.sup.1 and R.sup.2 are alkyl or halogen, R.sup.3 and R.sup.4 are hydrogen, R.sup.5 and R.sup.6 are alkyl or haloalkyl, --(CR.sup.8 R.sup.9).sub.m --R.sup.7 --(CR.sup.8 R.sup.9).sub.n -- is a single- or multi-membered chain in which R.sup.7 may also be a (substituted) hetero atom, and m+n is zero or 1, form, together with aluminoxanes as cocatalysts, a very effective catalyst system for the preparation of polyolefins of high molecular weight.

Abstract: A syndiotactic polyolefin is obtained in a high yield by polymerization or copolymerization of an olefin of the formula R.sup.a --CH.dbd.CH--R.sup.b in the presence of a catalyst consisting of a metallocene of the formula I ##STR1## and an aluminoxane. This polyolefin has a very high syndiotactic index. At a low polymerization temperature, a polyolefin having a low average molecular weight and narrow molecular weight distribution is obtained, and at a high polymerization temperature a polymer having a high average molecular weight and a wide molecular weight distribution is obtained.Shaped articles produced from the polymers are distinguished by a high transparency, flexibility, tear strength and excellent surface gloss.

Abstract: In the process according to the invention for the preparation of a polypropylene, a catalyst system is used which is based on the product of the reaction of a magnesium halide with an electron donor and a tetravalent titanium compound, a halogen-free organoaluminum compound and two different organosilicon compounds as stereo-regulator. Propylene homopolymers and copolymers having a very narrow molecular weight distribution and high isotacticity are obtained in high yields. The polymers are suitable, in particular, for injection molding.

Abstract: Polyolefin waxes are obtained in high yield by copolymerizing propylene with small amounts of other olefins in the presence of a catalyst composed of a metallocene of the formula I: ##STR1## and an alumoxane. The waxes are produced as compact, spherical particles having a narrow particle size distribution and high apparent density. In addition, the physical data of these waxes such as, for example, hardness, melting point, melt viscosity etc., are variable within wide limits.The polymer chains are noteworthy for a homogeneous and uniform structure, the comonomer units being predominantly arranged individually between polypropylene blocks.