Catalysts

A racemic 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, C1-20-hydrocarbyl, tri(C1-20-alkyl)silyl, C6-20-aryl, C7-20-arylalkyl or C7-20-alkylaryl;
• R2 and R2′ are each independently a C1-20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16;
• R5′ is Z′R3′ wherein Z′ is O or S;
• and R3′ is a C1-10 hydrocarbyl group optionally substituted by one or more halo groups;
• R6 and R6′ are each independently hydrogen or a C1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;
• R7 and R7′ are each independently hydrogen or C1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;
• Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R1;
• Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R1;
• each R1 is a C1-20 hydrocarbyl group or two R1 groups on adjacent carbon atoms taken together to form a fused 5 or 6 membered non aromatic ring with the Ar group, said ring being itself optionally substituted with one or more groups R4;
• and
• each R4 is a C1-20 hydrocarbyl group.