Abstract: Metallocenes of the formula ##STR1## where M is a metal selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta or an element selected from the group of the lanthanides, X.sub.1 and X.sub.2 are each an alkyl, alkoxy, aryl, aryloxy, alkenyl, arylalkyl, alkylaryl or arylalkenyl group, hydrogen or halogen and L.sub.1 and L.sub.2 are each a hydrocarbon which can form a sandwich structure with M, where at least L.sub.1 or L.sub.2 is substituted by or condensed with a ferrocene or ruthenocene radical. R.sub.1 is C, Si, Ge or Sn or the whole bridge A(R.sub.1).sub.n B is a biphenylene radical which is unsubstituted or substituted by A and/or B, A and B have the meanings of X.sub.1 and X.sub.2, n is an integer from 0 to 4.