Process for the preparation of an ethylene copolymer comprising polymerizing ethylene and a C 4-10 alpha-olefin comonomer in a high temperature solution process at a temperature greater than 100°C in the presence of a catalyst system comprising (i) a metallocene complex of formula wherein M is Zr X is chlorine or a methyl radical, L is a bridge of the formula -SiR 8 2 -, wherein each R 8 is independently a C 1 -C 20 -hydrocarbyl, tri(C 1 -C 20 -alkyl)silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl n is 0, 1 or 2 R 1 and R 1' are the same or can be different and can be a linear or branched C 1 -C 6 -alkyl group, R 2 and R 2' are the same or are different and are a CH 2 -R 9 group, with R 9 being H or linear or branched C 1 -C 6 -alkyl group R 5 and R 6 taken together form an unsubstituted 4-7 membered ring condensed to the benzene ring of the indenyl moiety; or R 5 is an OR group, wherein R is a linear or branched C 1 -C 6 -alkyl group, and R 6 is a C(R 10) 3 group, with R 10 being the same or different and R 10 can be H or a linear or branched C 1 -C 6 -alkyl group; and R 5' and R 6' taken together form an unsubstituted 4-7 membered ring condensed to the benzene ring of the indenyl moiety, with the proviso that if R 5 and R 6 as well as R 5' and R 6' taken together form an unsubstituted 5 membered ring condensed to the benzene ring of the indenyl moiety then R 2 and R 2' are not a C 1 -alkyl group; and R 7 and R 7' can be the same or are different and can be H or a linear or branched C 1 -C 6 -alkyl group (ii) an aluminoxane cocatalyst and (iii) a boron containing cocatalyst. (i) a metallocene complex of formula wherein M is Zr X is chlorine or a methyl radical, L is a bridge of the formula -SiR 8 2 -, wherein each R 8 is independently a C 1 -C 20 -hydrocarbyl, tri(C 1 -C 20 -alkyl)silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl n is 0, 1 or 2 R 1 and R 1' are the same or can be different and can be a linear or branched C 1 -C 6 -alkyl group, R 2 and R 2' are the same or are different and are a CH 2 -R 9 group, with R 9 being H or linear or branched C 1 -C 6 -alkyl group R 5 and R 6 taken together form an unsubstituted 4-7 membered ring condensed to the benzene ring of the indenyl moiety; or R 5 is an OR group, wherein R is a linear or branched C 1 -C 6 -alkyl group, and R 6 is a C(R 10) 3 group, with R 10 being the same or different and R 10 can be H or a linear or branched C 1 -C 6 -alkyl group; and R 5' and R 6' taken together form an unsubstituted 4-7 membered ring condensed to the benzene ring of the indenyl moiety, with the proviso that if R 5 and R 6 as well as R 5' and R 6' taken together form an unsubstituted 5 membered ring condensed to the benzene ring of the indenyl moiety then R 2 and R 2' are not a C 1 -alkyl group; and R 7 and R 7' can be the same or are different and can be H or a linear or branched C 1 -C 6 -alkyl group M is Zr X is chlorine or a methyl radical, L is a bridge of the formula -SiR 8 2 -, wherein each R 8 is independently a C 1 -C 20 -hydrocarbyl, tri(C 1 -C 20 -alkyl)silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl n is 0, 1 or 2 R 1 and R 1' are the same or can be different and can be a linear or branched C 1 -C 6 -alkyl group, R 2 and R 2' are the same or are different and are a CH 2 -R 9 group, with R 9 being H or linear or branched C 1 -C 6 -alkyl group R 5 and R 6 taken together form an unsubstituted 4-7 membered ring condensed to the benzene ring of the indenyl moiety; or R 5 is an OR group, wherein R is a linear or branched C 1 -C 6 -alkyl group, and R 6 is a C(R 10) 3 group, with R 10 being the same or different and R 10 can be H or a linear or branched C 1 -C 6 -alkyl group; and R 5' and R 6' taken together form an unsubstituted 4-7 membered ring condensed to the benzene ring of the indenyl moiety, with the proviso that if R 5 and R 6 as well as R 5' and R 6' taken together form an unsubstituted 5 membered ring condensed to the benzene ring of the indenyl moiety then R 2 and R 2' are not a C 1 -alkyl group; and R 7 and R 7' can be the same or are different and can be H or a linear or branched C 1 -C 6 -alkyl group (ii) an aluminoxane cocatalyst and (iii) a boron containing cocatalyst.