A metallocene complex of formula (I): each X is a sigma-ligand; in the group R2Si— at least one R is methyl or ethyl, and the other R is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl or isobutyl, pentyl, hexyl, cyclohexyl and phenyl; each R1 independently is the same or can be different and are a CH2—R7 group, with R7 being H or linear or branched C1-6-alkyl group, C3-8 cycloalkyl group, or C6-10 aryl group; each R2 is independently a —CH═, —CY═, —CH2—, —CHY— or —CY2— group, wherein Y is a C1-6 hydrocarbyl group and where n is 2-6; each R3 and R4 are independently the same or can be different and are hydrogen, a linear or branched C1-6-alkyl group, a C7-20 arylalkyl, C7-20 alkylaryl group, C6-20 aryl group, or an —OY group, wherein Y is a is a C1-6 hydrocarbyl group; R5 is a linear or branched C1-6-alkyl group, C7-20 arylalkyl, C7-20 alkylaryl group or C6-20-aryl group; and R6 is a C(R8)3 group, with R8 being a linear or branched C1-6 alkyl group; (A) wherein at least one R3 per phenyl group and at least one R4 is not hydrogen, and wherein at least one R3 per phenyl group and at least one R4 is hydrogen; or (B) wherein one R3 is an —OY group, wherein Y is a is a C1-6 hydrocarbyl group, in 4 position of each phenyl group and the two other R3 groups are tert-butyl groups; and/or (C) wherein one R4 is an —OY group, wherein Y is a is a C1-6 hydrocarbyl group, in 4-position of the phenyl ring and the two other R4 groups are tert-butyl groups.