Catalysts

1. 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′ 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, C 1-20 -hydrocarbyl, tri(C 1-20 -alkyl)silyl, C 6-20 -aryl, C 7-20 -arylalkyl or C 7-20 -alkylaryl;

R 2 and R 2 ′ are each independently a C 1-20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16;

R 5′ is Z′R 3′ wherein Z′ is O or S; and R 3′ is a C 1-10 hydrocarbyl group optionally substituted by one or more halo groups;

R 6 and R 6′ are each independently hydrogen or a C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;

R 7 and R 7′ are each independently hydrogen or C 1-20 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 R 1 ;

Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;

each R 1 is a C 1-20 hydrocarbyl group or two R 1 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 R 4 ; and

each R 4 is a C 1-20 hydrocarbyl group.

2. The complex of claim 1 being a racemic anti isomer.

3. The complex of claim 1 , in which R 7 and R 7′ are hydrogen and R 2 and R 2′ are the same.

4. The complex of claim 1 , wherein Ar and Ar′ are different.

5. The complex of claim 1 of formula (II′) or (II);

wherein

M is zirconium or hafnium;

each X is a sigma ligand;

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, C 1-20 alkyl, C 3-10 cycloalkyl, tri(C 1-20 -alkyl)silyl, C 6-20 -aryl, C 7-20 arylalkyl or C 7-20 alkylaryl;

each R 2 or R 2′ is a C 1-10 alkyl group;

R 5′ is a Z′R 3′ group;

R 6 is hydrogen or a C 1-10 alkyl group;

R 6′ is a C 1-10 alkyl group or C 6-10 aryl group;

R 7 is hydrogen, a C 1-6 alkyl group or ZR 3 group;

R 7′ is hydrogen or a C 1-10 alkyl group;

Z and Z′ are independently O or S;

R 3′ is a C 1-10 alkyl group, or a C 6-10 aryl group optionally substituted by one or more halo groups;

R 3 is a C 1-10 -alkyl group;

n is 0 to 4, e.g. 0, 1 or 2;

and each R 1 is a C 1-20 hydrocarbyl group, e.g. C 1-10 alkyl group.

6. The complex of claim 1 of formula (III′) or (III):

M is zirconium or hafnium;

each X is a sigma ligand;

L is a divalent bridge selected from —R′ 2 C— or —R′ 2 Si— wherein each R′ is independently a hydrogen atom, C 1-20 alkyl or C 3-10 cycloalkyl;

R 6 is hydrogen or a C 1-10 alkyl group;

R 6′ is a C 1-10 alkyl group or C 6-10 aryl group;

R 7 is hydrogen, C 1-6 alkyl or OC 1-6 alkyl;

Z′ is O or S;

R 3′ is a C 1-10 alkyl group, or C 6-10 aryl group optionally substituted by one or more halo groups;

n is 0 to 4, e.g. 0, 1 or 2; and

each R 1 is a C 1-10 alkyl group.

7. The complex of claim 1 of formula (IV′) or (IV)

M is zirconium or hafnium;

each X is a sigma ligand;

each R′ is independently a hydrogen atom, C 1-20 alkyl or C 3-7 cycloalkyl;

R 6 is hydrogen or a C 1-10 alkyl group;

R 6′ is a C 1-10 alkyl group or C 6-10 aryl group;

R 7 is hydrogen, C 1-6 alkyl or OC 1-6 alkyl;

Z′ is O or S;

R 3′ is a C 1-10 alkyl group, or C 6-10 aryl group optionally substituted by one or more halo groups;

n is 0, 1 to 2; and

each R 1 is a C 3-8 alkyl group.

8. The complex of claim 1 of formula (V) or (V′)

wherein each X is a sigma ligand;

R′ is independently a C 1-6 alkyl or C 3-10 cycloalkyl;

R 1 is C 3-8 alkyl;

R 6 is hydrogen or a C 3-8 alkyl group;

R 6′ is a C 3-8 alkyl group or C 6-10 aryl group;

R 3′ is a C 1-6 alkyl group, or C 6-10 aryl group optionally substituted by one or more halo groups; and

n is 0, 1 or 2.

9. A catalyst comprising (i) a complex of formula (I) as claimed in claim 1 and (ii) a cocatalyst comprising a compound of a group 13 metal.

10. The catalyst of claim 9 obtainable by a process in which

(a) a liquid/liquid emulsion system is formed, said liquid/liquid emulsion system comprising a solution of the catalyst components (i) and (ii) dispersed in a solvent so as to form dispersed droplets; and

(b) solid particles are formed by solidifying said dispersed droplets.

11. A process for the manufacture of the catalyst as defined in claim 9 , comprising obtaining a complex of formula (I) and a cocatalyst as defined in claim 9 ;

forming a liquid/liquid emulsion system, which comprises a solution of catalyst components (i) and (ii) dispersed in a solvent, and solidifying said dispersed droplets to form solid particles.

12. A process for the polymerisation of at least one olefin comprising reacting said at least one olefin with the catalyst as claimed in claim 9 .

13. The complex of claim 5 , wherein each X is independently a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group.

14. The complex of claim 6 , wherein each X is independently a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group.

15. The complex of claim 7 , wherein each X is independently a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group.

16. The complex of claim 8 , wherein each X is independently a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group.

17. The catalyst of claim 9 , wherein the cocatalyst is a compound of aluminum or boron.

18. The process of claim 12 , wherein the olefin is propylene.