Catalyst compositions for the preparation of olefin (co) polymers

The invention relates to a catalyst preparation which can be obtained by mixing a metal complex (A) wherein the substituents have the following meaning: M means chromium, molybdenum or wolframium; Z means fluorine, chlorine, bromine, iodine, hydrogen or C1 - C20 alkyl; R to R independently mean hydrogen, C1 - C10 alkyl, C3 to C7 cycloalkyl unsubstituted or substituted by C1 - C10 alkyl, C6 - C18 aryl, and substituted C6 - C18 aryl and 2 adjacent radicals can jointly mean saturated or unsaturated cyclic groups with 4 to 18 C atoms, or Si(R )3 with R6 meaning independently C1 - C10 alkyl, C3 to C10 cycloalkyl or C6 - C18 aryl, Y means independently C1 - C20 alkyl, C3 to C10 cycloalkyl, C6 - C18 aryl or aralkyl with 1 to 10 C atoms in the alkyl radical and 6 to 18 C atoms in the aryl radical; and a metallocene-ion forming compound (B) in an inert liquid reaction medium.