| abstract |
A catalyst comprisingn (i) an asymmetric complex of formula (I) nn n n n n n n n n n n n wherein n M is zirconium or hafnium; n each X is a sigma ligand; n L is a divalent bridge selected from —R′ 2 C—, —R′ 2 C—CR′ 2 —, —R′ 2 Si—, —R′ 2 Si—SiR′ 2 —, —R′ 2 Ge—, wherein each R′ is independently a hydrogen atom, C1-C20-alkyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl; n R 2 and R 2′ are each independently linear C 1-10 hydrocarbyl; n R 5 and R 5′ are each independently hydrogen or a C1-20 hydrocarbyl group; n R 6 and R 6′ are each independently hydrogen or a C1-20 hydrocarbyl group; n R 7 is hydrogen or a C1-20 hydrocarbyl group or is ZR 3 ; n Z is O or S, preferably O; n R 3 is a C1-10 hydrocarbyl group; n Ar is an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 8 ; n Ar′ is an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 8′ ; and n R 8 and R 8′ are each independently is a C1-20 hydrocarbyl group; n with the proviso that at least one of R 6 or R 7 is not H; n and (ii) a cocatalyst comprising a compound of a group 13 metal, e.g. boron. |