Abstract: Process for the preparation of a catalyst component for the polymerization and copolymerization of ethylene to give ultrahigh-molecular-weight ethylene polymers. Reaction of a Grignard compound with a halogenating agent, a titanium compound, a perhalogen compound and an electron-donor compound and subsequent comminution of the resultant solid to a mean particle size of from 0.5 to 5 .mu.m gives a catalyst component which, together with an organoaluminum compound, results, in the polymerization and copolymerization of ethylene, in ultrahigh-molecular-weight ethylene polymers having a mean particle diameter of from 50 to 200 .mu.m and a viscosity index of greater than 2,000 cm.sup.3 /g. The mean particle diameter can be adjusted by means of the catalyst particle diameter and by means of the catalyst productivity.

Abstract: The present invention relates to a metallocene compound of the formula I which is suitable for olefin polymerization ##STR1## where M is a metal of group IVb, Vb or VIb of the Periodic Table.X are each a hydrogen atom, a halogen atom or a C.sub.1 -C.sub.40 -radical OR.sup.4 or NR.sup.4.sub.2, where R.sup.4 are a C.sub.1 -C.sub.20 hydrocarbon radicalm and p are 1, 2 or 3,n is 1 or 2,L each a .pi. ligand which coordinates to the central atom M,M.sup.2 are each a silicon atom, a germanium atom or a tin atom,R.sup.1 are a C.sub.1 -C.sub.20 -radical,R.sup.2 are a C.sub.1 -C.sub.20 -radical or a .pi. ligand which coordinates to the central atom M,A are each a bidentate C.sub.1 -C.sub.40 -hydrocarbon group,Z are each a boron atom, a silicon atom, a germanium atom or a tin atom,R.sup.3 are each a hydrogen atom or a C.sub.1 -C.sub.20 -radical,o is zero, 1 or 2,Hal are each a halogen atom, andwhere n is 1 if R.sup.2 is a .pi. ligand which coordinates to the central atom M and n is 2 if R.sup.2 is a C.sub.1 -C.sub.