ИСТИНА

A catalyst comprising (i) an asymmetric complex of formula (I) wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R'2C-, -R'2C-CR'2-, -R'2Si-, -R'2Si-SiR'2-, -R'2Ge-, wherein each R' is independently a hydrogen atom, Cl-C20-alkyl, tri(Cl- C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl; R2 and R2' are each independently linear C1-10 hydrocarbyl; R5 and R5' are each independently hydrogen or a CI -20 hydrocarbyl group; R6 and R6' are each independently hydrogen or a CI -20 hydrocarbyl group; R7 is hydrogen or a CI -20 hydrocarbyl group or is ZR3; Z is O or S, preferably O; R3 is a Cl-10 hydrocarbyl group; Ar is an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R8; Ar' is an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R8'; R8 and R8' are each independently is a CI -20 hydrocarbyl group; with the proviso that at least one of R6 or R7 is not H; and (ii) a cocatalyst comprising a compound of a group 13 metal, e.g. boron.