A metallocene corresponding to the formula wherein M is a group 4 transition metal, each Y is, independently, selected from the group of halogen, hydrocarbyl and hydrocarbyloxy, R1, R4 are, independently, selected from the group of hydrogen, hydrocarbyl, hydrocarbyloxy, R2, R3, R5, R6, R7, R8 are, independently, selected from the group of hydrogen, hydrocarbyl, hydrocarbyloxy, with the provision that, respectively, R2 and R3, R5 and R6, R7 and R8 can be linked to each other. A process for the preparation of metallocenes comprising the following steps: (a) contacting, in a solvent, a transition metal halide of formula MX4 with an organometallic compound of formula M′Rm, wherein M is a group 4 transition metal, X is a halogen, M′ is an element chosen from the groups 1, 2 and 13 of the periodic table, R is hydrogen, an alkyl, aryl, alkenyl or alkynyl group containing up to 20 carbon atoms, m=1 when M′ is a group 1 element, m=2 when M′ is a group 2 element, m=3 when M′ is a group 13 element, in order to reduce M, which leads to a subvalent transition metal halide, (b) purifying the subvalent transition metal halide and (c) contacting the subvalent transition metal halide with at least one fulvene compound.