Catalysts

1. A complex of formula (Ia)

wherein:

M is Hf or Zr;

each X is a sigma ligand;

L is:

a bridge of formula —SiR 8 2 , where each R 8 is independently a C 1 -C 10 -hydrocarbyl or C 6 -C 10 -aryl group;

or

an alkylene group;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or different and are a linear or branched C 1 -C 6 -alkyl group or C 6-20 aryl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

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 1-6 -alkyl group, C 3-8 cycloalkyl group, or C 6-10 aryl group;

Each R 3 is a —CH 2 —, —CHRx- or C(Rx) 2 - group, wherein Rx is C 1-4 alkyl and where m is 2-6;

R 5 is a linear or branched C 1 -C 6 -alkyl group, C 7-20 arylalkyl, C 7-20 alkylaryl group, or C 6 -C 20 -aryl group;

R 6 is a C(R 10 ) 3 group, with R 10 being a linear or branched C 1 -C 6 alkyl group; and

R 7 and R 7′ are H.

2. The complex according to claim 1 , wherein the complex is of formula (II)

wherein:

M is Hf or Zr;

X is a sigma ligand;

L is:

an alkylene bridge or

a bridge of the formula —SiR 8 2 —, wherein each R 8 is independently C 1 -C 6 -alkyl, C 3-8 cycloalkyl or C 6 -aryl group;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or different and are a linear or branched C 1 -C 6 -alkyl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

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 1-6 -alkyl group;

R 5 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 a linear or branched C 1 -C 6 alkyl group.

3. The complex according to claim 1 , wherein the complex is of formula (III)

wherein:

M is Hf or Zr;

each X is a sigma ligand;

L is —SiR 8 2 —, wherein each R 8 is C 1-6 alkyl or C 3-8 cycloalkyl;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or different and are a linear or branched C 1 -C 6 -alkyl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

R 5 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 a linear or branched C 1 -C 6 alkyl group.

4. The complex according to claim 1 , wherein the complex is of formula (IV)

wherein:

M is Hf or Zr;

each X is a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group;

L is —SiR 8 2 —, wherein each R 8 is C 1-4 alkyl or C 5-6 cycloalkyl;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or can be different and are a linear or branched C 1 -C 6 -alkyl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

R 5 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 a linear or branched C 1 -C 6 alkyl group.

5. The complex according to claim 1 , wherein the complex is of formula (V)

wherein

M is Hf or Zr;

X is a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group;

L is —SiMe 2 ;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or can be different and are a linear or branched C 1 -C 6 -alkyl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

R 5 is a linear or branched C 1 -C 4 -alkyl group; and

R 6 is a C(R 10 ) 3 group, with R 10 being a linear or branched C 1 -C 4 alkyl group.

6. The complex according to claim 1 , wherein the complex is of formula (VI)

wherein

M is Hf or Zr;

X is a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group;

L is —SiMe 2 ;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or different and are a linear or branched C 1 -C 6 -alkyl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

R 5 is a linear C 1 -C 4 -alkyl group such as methyl; and

R 6 is tert butyl.

7. The complex according to claim 1 , wherein the complex is of formula (VII)

wherein:

M is Hf or Zr;

X is a hydrogen atom, a halogen atom, C 1-6 alkoxy group, C 1-6 alkyl, phenyl or benzyl group, especially chlorine;

L is —SiMe 2 ;

each n is independently 1 or 2;

R 1 and R 1′ are each independently the same or can be different and are a linear or branched C 1 -C 4 -alkyl group, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

R 5 is methyl; and

R 6 is tert butyl.

8. The complex according to claim 1 , wherein the complex is of formula (VIII)

wherein:

M is Hf or Zr;

X is Cl;

L is —SiMe 2 ;

each n is independently 1 or 2;

R 1 and R 1′ are each independently methyl or tert butyl, wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl or 4-(tert-butyl)-phenyl;

R 5 is methyl; and

R 6 is tert butyl.

9. The complex according to claim 1 , wherein at least one of the C(4) or C(4′) phenyl rings is 3,5-dimethyl phenyl.

10. The complex according to claim 1 , wherein at least one of the C(4) or C(4′) phenyl rings is 4-(tert-butyl)-phenyl.

11. The complex according to claim 1 , wherein R 1 , R 1′ and each value of n are selected such that the C(4) or C(4′) phenyl rings are 3,5-dimethyl phenyl, 3,5-ditertbutylphenyl and/or 4-(tert-butyl)-phenyl.

12. A catalyst system comprising:

(i) the complex according to claim 1 ; and

(ii) a cocatalyst.

13. The catalyst system according to claim 12 , wherein the cocatalyst comprises a boron containing cocatalyst, an Al cocatalyst, or both Al and B cocatalysts.

14. The catalyst system as claimed in claim 12 , wherein the catalyst system is in solid form.

15. The catalyst system as claimed in claim 14 , wherein the catalyst system is supported on silica.

16. A process for the manufacture of the catalyst system as claimed in claim 12 , said catalyst system comprising obtaining the complex (i) as claimed in claim 11 and the cocatalyst (ii);

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

17. The process as claimed in claim 16 , the process further comprising off line prepolymerisation of the catalyst.

18. A process for the preparation of a polypropylene homopolymer, a propylene-ethylene copolymer, or a propylene C4-10 alpha olefin copolymer the process comprising polymerising propylene, propylene and ethylene or propylene and a C4-10 alpha olefin, in the presence of the catalyst system according to claim 12 .

19. A process for the preparation of a heterophasic polypropylene copolymer comprising:

(I) polymerising propylene in bulk in the presence of the catalyst system as claimed in claim 12 to form a polypropylene homopolymer matrix;

(II) in the presence of said matrix and said catalyst system and in the gas phase, polymerising propylene and ethylene to form a heterophasic polypropylene copolymer comprising a homopolymer matrix and an ethylene propylene rubber (EPR).

20. A process for the preparation of a heterophasic polypropylene copolymer comprising:

(I) polymerising propylene in bulk in the presence of the catalyst system as claimed in claim 12 to form a polypropylene homopolymer;

(II) in the presence of said homopolymer and said catalyst and in the gas phase, polymerising propylene to form a polypropylene homopolymer matrix;

(III) in the presence said matrix and said catalyst system and in the gas phase, polymerising propylene and ethylene to form a heterophasic polypropylene copolymer comprising a homopolymer matrix and an ethylene propylene rubber (EPR).

21. The process as claimed in claim 19 , wherein which the EPR component is fully soluble in xylene at room temperature.

22. The process as claimed in claim 19 , wherein the iV of the EPR is above 2.0 dL/g when measured in decaline.

23. The process as claimed in claim 19 , wherein the Mw/Mn of the polypropylene homopolymer matrix component, as measured by GPC, is broader than 3.5.

24. The process as claimed in claim 19 , wherein the Mw/Mn of the polypropylene homopolymer matrix component, as measured by GPC, is 4.0 to 8.0.