CATALYSTS

INTRODUCTION

[0001] The present invention relates to catalysts. More specifically, the present invention relates to particular metallocene catalysts, and the use of such catalysts in polyolefin polymerization reactions. Even more specifically, the present invention relates to unsymmetrical metallocene catalysts, and the use of such catalysts in ethylene polymerization reactions.

BACKGROUND OF THE INVENTION

[0002] It is well known that ethylene (and a-olefins in general) can be readily polymerized at low or medium pressures in the presence of certain transition metal catalysts. These catalysts are generally known as Zeigler-Natta type catalysts.

[0003] A particular group of these Ziegler-Natta type catalysts, which catalyse the polymerization of ethylene (and a-olefins in general), comprise an aluminoxane activator and a metallocene transition metal catalyst. Metallocenes comprise a metal bound between two rf-cyclopentadienyl type ligands. Generally the rf-cyclopentadienyl type ligands are selected from rf-cyclopentadienyl, if -indenyl and if -fluorenyl.

[0004] It is also well known that these rf-cyclopentadienyl type ligands can be modified in a myriad of ways. One particular modification involves the introduction of a linking group between the two cyclopentadienyl rings to form ansa-metallocenes.

[0005] Numerous ansa-metallocenes of transition metals are known in the art. However, there remains a need for improved ansa-metallocene catalysts for use in polyolefin polymerization reactions. In particular, there remains a need for new metallocene catalysts with high polymerization activities/efficiencies.

[0006] There is also a need for catalysts that can produce polyethylenes with particular characteristics. For example, catalysts capable of producing linear high density polyethylene (LHDPE) with a relatively narrow dispersion in polymer chain length are desirable. Moreover, there is a need for catalysts that can produce polyethylene copolymers having good co- monomer incorporation and good intermolecular uniformity of polymer properties.

[0007] WO201 1/051705 discloses ansa-metallocene catalysts based on two rf -indenyl ligands linked via an ethylene group. [0008] There remains a need for ansa-metallocene catalysts having improved polymerization activity. Moreover, due to the high value that industry places on such materials, there is also a need for ansa-metallocene catalysts capable of polymerizing a- olefins to high molecular weights, without compromising polydispersity. It is even further desirable that such catalysts can be easily synthesized.

[0009] The present invention was devised with the foregoing in mind.

SUMMARY OF THE INVENTION

[0010] According to a first aspect of the present invention there is provided a composition comprising a solid methyl aluminoxane support material and a compound of formula (I) defined herein.

[0011] According to a second aspect of the present invention, there is provided a use of a composition as defined herein as a polymerisation catalyst for the preparation of a polyethylene homopolymer or a copolymer comprising polyethylene.

[0012] According to a third aspect of the present invention, there is provided a process for forming a polyethylene homopolymer or a polyethylene copolymer which comprises reacting olefin monomers in the presence of a composition as defined herein.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0013] The term "alkyl" as used herein includes reference to a straight or branched chain alkyl moieties, typically having 1 , 2, 3, 4, 5 or 6 carbon atoms. This term includes reference to groups such as methyl, ethyl, propyl (n-propyl or isopropyl), butyl (n-butyl, sec-butyl or tert- butyl), pentyl (including neopentyl), hexyl and the like. In particular, an alkyl may have 1 , 2, 3 or 4 carbon atoms.

[0014] The term "alkenyl" as used herein include reference to straight or branched chain alkenyl moieties, typically having 2, 3, 4, 5 or 6 carbon atoms. The term includes reference to alkenyl moieties containing 1 , 2 or 3 carbon-carbon double bonds (C=C). This term includes reference to groups such as ethenyl (vinyl), propenyl (allyl), butenyl, pentenyl and hexenyl, as well as both the c/ ^' s and trans isomers thereof.

[0015] The term "alkynyl" as used herein include reference to straight or branched chain alkynyl moieties, typically having 2, 3, 4, 5 or 6 carbon atoms. The term includes reference to alkynyl moieties containing 1 , 2 or 3 carbon-carbon triple bonds (C≡C). This term includes reference to groups such as ethynyl, propynyl, butynyl, pentynyl and hexynyl.

[0016] The term "alkoxy" as used herein include reference to -O-alkyl, wherein alkyl is straight or branched chain and comprises 1 , 2, 3, 4, 5 or 6 carbon atoms. In one class of embodiments, alkoxy has 1 , 2, 3 or 4 carbon atoms. This term includes reference to groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, hexoxy and the like.

[0017] The term "aryl" as used herein includes reference to an aromatic ring system comprising 6, 7, 8, 9 or 10 ring carbon atoms. Aryl is often phenyl but may be a polycyclic ring system, having two or more rings, at least one of which is aromatic. This term includes reference to groups such as phenyl, naphthyl and the like.

[0018] The term "carbocyclyl" as used herein includes reference to an alicyclic moiety having 3, 4, 5, 6, 7 or 8 carbon atoms. The group may be a bridged or polycyclic ring system. More often cycloalkyl groups are monocyclic. This term includes reference to groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, bicyclo[2.2.2]octyl and the like.

[0019] The term "heterocyclyl" as used herein includes reference to a saturated (e.g. heterocycloalkyl) or unsaturated (e.g. heteroaryl) heterocyclic ring moiety having from 3, 4, 5, 6, 7, 8, 9 or 10 ring atoms, at least one of which is selected from nitrogen, oxygen, phosphorus, silicon and sulphur. In particular, heterocyclyl includes a 3- to 10-membered ring or ring system and more particularly a 5- or 6-membered ring, which may be saturated or unsaturated.

[0020] A heterocyclic moiety is, for example, selected from oxiranyl, azirinyl, 1 ,2- oxathiolanyl, imidazolyl, thienyl, furyl, tetrahydrofuryl, pyranyl, thiopyranyl, thianthrenyl, iso- benzofuranyl, benzofuranyl, chromenyl, 2 - -pyrrolyl, pyrrolyl, pyrrolinyl, pyrrolidinyl, imidazolyl, imidazolidinyl, benzimidazolyl, pyrazolyl, pyrazinyl, pyrazolidinyl, thiazolyl, isothiazolyl, dithiazolyl, oxazolyl, isoxazolyl, pyridyl, pyrazinyl, pyrimidinyl, piperidyl, piperazinyl, pyridazinyl, morpholinyl, thiomorpholinyl, especially thiomorpholino, indolizinyl, isoindolyl, 3 - -indolyl, indolyl, benzimidazolyl, cumaryl, indazolyl, triazolyl, tetrazolyl, purinyl, 4 - -quinolizinyl, isoquinolyl, quinolyl, tetrahydroquinolyl, tetrahydroisoquinolyl, decahydroquinolyl, octahydroisoquinolyl, benzofuranyl, dibenzofuranyl, benzothiophenyl, dibenzothiophenyl, phthalazinyl, naphthyridinyl, quinoxalyl, quinazolinyl, quinazolinyl, cinnolinyl, pteridinyl, carbazolyl, β-carbolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl, furazanyl, phenazinyl, phenothiazinyl, phenoxazinyl, chromenyl, isochromanyl, chromanyl and the like. [0021] The term "heteroaryl" as used herein includes reference to an aromatic heterocyclic ring system having 5, 6, 7, 8, 9 or 10 ring atoms, at least one of which is selected from nitrogen, oxygen and sulphur. The group may be a polycyclic ring system, having two or more rings, at least one of which is aromatic, but is more often monocyclic. This term includes reference to groups such as pyrimidinyl, furanyl, benzo[b]thiophenyl, thiophenyl, pyrrolyl, imidazolyl, pyrrolidinyl, pyridinyl, benzo[b]furanyl, pyrazinyl, purinyl, indolyl, benzimidazolyl, quinolinyl, phenothiazinyl, triazinyl, phthalazinyl, 2H-chromenyl, oxazolyl, isoxazolyl, thiazolyl, isoindolyl, indazolyl, purinyl, isoquinolinyl, quinazolinyl, pteridinyl and the like.

[0022] The term "halogen" or "halo" as used herein includes reference to F, CI, Br or I. In a particular, halogen may be F or CI, of which CI is more common.

[0023] The term "substituted" as used herein in reference to a moiety means that one or more, especially up to 5, more especially 1 , 2 or 3, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents. The term "optionally substituted" as used herein means substituted or unsubstituted.

[0024] It will, of course, be understood that substituents are only at positions where they are chemically possible, the person skilled in the art being able to decide (either experimentally or theoretically) without inappropriate effort whether a particular substitution is possible. For example, amino or hydroxy groups with free hydrogen may be unstable if bound to carbon atoms with unsaturated (e.g. olefinic) bonds. Additionally, it will of course be understood that the substituents described herein may themselves be substituted by any substituent, subject to the aforementioned restriction to appropriate substitutions as recognised by the skilled person.

Catalytic compositions

[0025] As discussed hereinbefore, the present invention provides a composition comprising a solid methyl aluminoxane support material and a compound of the formula (I) shown below:

(I)

wherein:

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ and R ₄ are each independently hydrogen or (1 -4C)alkyl, or R ₃ and R ₄ are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, halo, amino, nitro, cyano, (1 -6C)alkylamino, [(1 -6C)alkyl] ₂ amino and -S(0) ₂ (1 - 6C)alkyl;

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, halo, amino, nitro, cyano, (1 -6C)alkylamino, [(1 -6C)alkyl] ₂ amino and -S(0) ₂ (1 - 6C)alkyl;

Q is a bridging group comprising 1 , 2 or 3 bridging atoms selected from C, N, O, S, Ge, Sn, P, B, or Si, or a combination thereof, and is optionally substituted with one or more groups selected from hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl;

X is selected from zirconium, titanium or hafnium; and each Y group is independently selected from halo, hydride, a phosphonated, sulfonated or borate anion, or a (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl or aryloxy group which is optionally substituted with one or more groups selected from (1 - 6C)alkyl, halo, nitro, amino, phenyl, (1 -6C)alkoxy, -C(0)NR _x R _y or Si[(1 -4C)alkyl] ₃ ;

wherein R _x and R _y are independently (1 -4C)alkyl;

with the proviso that:

i) when R ₃ and R ₄ are hydrogen or (1 -4C)alkyl, R ₅ and R ₆ are not linked to form a fused 6-membered aromatic ring that is substituted with four methyl groups; and

ii) when R ₅ and R ₆ are hydrogen or (1 -4C)alkyl, R ₃ and R ₄ are not linked to form a fused 6-membered aromatic ring that is substituted with four methyl groups.

[0026] In an embodiment, the compound has a structure according to formula (I) wherein

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ and R ₄ are each independently hydrogen or (1 -4C)alkyl, or R ₃ and R ₄ are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, halo, amino, nitro, cyano, (1 -6C)alkylamino, [(1 -6C)alkyl] ₂ amino and -S(0) ₂ (1 - 6C)alkyl;

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, halo, amino, nitro, cyano, (1 -6C)alkylamino, [(1 -6C)alkyl] ₂ amino and -S(0) ₂ (1 - 6C)alkyl;

Q is a bridging group comprising 1 , 2 or 3 bridging atoms selected from C, N, O, S, Ge, Sn, P, B, or Si, or a combination thereof, and is optionally substituted with one or more groups selected from hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl;

X is selected from zirconium, titanium or hafnium; and each Y group is independently selected from halo, hydride, a phosphonated, sulfonated or borate anion, or a (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl or aryloxy group which is optionally substituted with halo, nitro, amino, phenyl, -C(0)NR _x R _y , (1 -6C)alkoxy, or Si[(1 -4C)alkyl] ₃ ;

wherein R _x and R _y are independently (1 -4C)alkyl;

with the proviso that:

i) when R ₃ and R ₄ are hydrogen or (1 -4C)alkyl, R ₅ and R ₆ are not linked to form a fused 6-membered aromatic ring that is substituted with four methyl groups; and

ii) when R ₅ and R ₆ are hydrogen or (1 -4C)alkyl, R ₃ and R ₄ are not linked to form a fused 6-membered aromatic ring that is substituted with four methyl groups.

[0027] In another embodiment, the compound has a structure according to formula (I) wherein

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ and R ₄ are each independently hydrogen or (1 -4C)alkyl, or R ₃ and R ₄ are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, halo, amino, nitro, cyano, (1 -6C)alkylamino, [(1 -6C)alkyl] ₂ amino and -S(0) ₂ (1 - 6C)alkyl;

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a 6-membered fused aromatic ring optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy, halo, amino, nitro, cyano, (1 -6C)alkylamino, [(1 -6C)alkyl] ₂ amino and -S(0) ₂ (1 - 6C)alkyl;

Q is a bridging group comprising 1 , 2 or 3 bridging atoms selected from C, N, O, S, Ge, Sn, P, B, or Si, or a combination thereof, and is optionally substituted with one or more groups selected from hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl; X is selected from zirconium, titanium or hafnium; and

at least one Y group is an aryloxy group which is optionally substituted with one or more groups selected from (1 -6C)alkyl, and the other Y group is independently selected from halo, hydride, a phosphonated, sulfonated or borate anion, or a (1 -6C)alkyl, (2-6C)alkenyl, (2- 6C)alkynyl, (1 -6C)alkoxy, aryl or aryloxy group which is optionally substituted with one or more groups selected from (1 -6C)alkyl, halo, nitro, amino, phenyl, -C(0)NR _x R _y , (1 -6C)alkoxy, or Si[(1 -4C)alkyl] ₃ ;

wherein R _x and R _y are independently (1 -4C)alkyl;

with the proviso that:

i) when R ₃ and R ₄ are hydrogen or (1 -4C)alkyl, R ₅ and R ₆ are not linked to form a fused 6-membered aromatic ring that is substituted with four methyl groups; and

ii) when R ₅ and R ₆ are hydrogen or (1 -4C)alkyl, R ₃ and R ₄ are not linked to form a fused 6-membered aromatic ring that is substituted with four methyl groups.

[0028] Having regard to the proviso outlined above, it will be understood that the particular motifs not covered by the scope of the appended claims are as follows:

[0029] It will be appreciated that the structural formula (I) presented above is intended to show the substituent groups in a clear manner. A more representative illustration of the spatial arrangement of the groups is shown in the alternative representation below:

[0030] It will also be appreciated that when substituents R ₃ and R ₄ are not identical to substituents R ₅ and R ₆ respectively, the compounds of the present invention may be present as meso or rac isomers, and the present invention includes both such isomeric forms. A person skilled in the art will appreciate that a mixture of isomers of the compound of formula (!) may be used for catalysis applications, or the isomers may be separated and used individually {using techniques well known in the art, such as, for example, fractional crystallization).

[0031] The compositions of the invention exhibit superior catalytic performance when compared with current metallocene compounds/compositions used in the polymerisation of a- oiefins. In particular, when compared with analogous silica-supported methyl aluminoxane (SSMAO) and layered double hydroxide-supported methyl aluminoxane (LDHMAO) catalyst compositions, the solid MAO compositions of the invention exhibit significantly increased catalytic activity in the homopolymerisation and copolymerisation of a-olefins. Moreover, polymers produced by a-olefin polymerization in the presence of compositions of the invention are typically of a higher molecular weight than polymers prepared using other catalysts, without an attendant increase in polydispersity. Such materials are highly valued by industry. Furthermore, polyethylene copolymers produced by a-oiefin polymerization in the presence of compositions of the invention demonstrate good co-monomer incorporation in polyethylene, with good inter-molecular uniformity.

[0032] Solid methyl aluminoxane (MAO) (often referred to as poiymethyla!uminoxane) is distinguished from other methyl aluminoxanes (MAOs) as it is insoluble in hydrocarbon solvents and so acts as a heterogeneous support system. Any suitable solid MAO support may be used.

[0033] In an embodiment, the solid MAO support is insoluble in toluene and hexane.

[0034] In another embodiment, the solid MAO support is in particulate form. Suitably, the particles of the solid MAO support are spherical, or substantially spherical, in shape.

[0035] In a particularly suitable embodiment, the solid MAO support is as described in US2013/0059990 and obtainable from Tosoh Finechem Corporation, Japan.

[0036] In an embodiment, the solid MAO support is prepared according to the following protocol:

Benzoic acid Heat HEAT

AIMe ₃ Aluminoxane MAO *■ Solid MAO

precursor

15 °C 80 100 °C

+ CH ₄

30 min 14 h

SUBSTITUTE SHEET RULE 26 The properties of the solid MAO support can be adjusted by altering one or more of the processing variables used during its synthesis. For example, in the above-outlined protocol, the properties of the solid MAO support may be adjusted by varying the Al:0 ratio, by fixing the amount of AIMe ₃ and varying the amount of benzoic acid. Exemplary Ai:0 ratios are 1 :1 , 1.1:1 , 1.2:1 , 1.3:1, 1.4:1 and 1.6:1. Suitably the Al:0 ratio is 1.2:1 or 1.3:1. Alternatively, the properties of the solid MAO support may be adjusted by fixing the amount of benzoic acid and varying the amount of AIMe ₃ .

[0037] In another embodiment, the solid MAO support is prepared according to the following protocol:

Step 1 Step 2 Step 3

Benzoic acid » , . Heat HE—AT

A!uminoxane ^ MAO — →■ Solid MAO

0.5 h precursor _{2Q h 14 h}

15 °c ^{+ CH} 4 100 °C

In the above protocol, steps 1 and 2 may be kept constant, with step 2 being varied. The temperature of step 2 may be 70-100°C (e.g. 70°C, 80°C, 90°C or 100°C). The duration of step 2 may be from 12 to 28 hours (e.g. 12, 20 or 28 hours).

[0038] The compound of formula (I) may be immobilized on the solid MAO support by one or more ionic or covalent interactions.

[0039] In an embodiment, the composition further comprises one or more suitable activators. Suitable activators are well known in the art and include organo aluminium compounds (e.g. alkyi aluminium compounds). Particularly suitable activators include aluminoxanes (e.g. methylaluminoxane (MAO)), triisobutylaluminium (TIBA), diethy!aluminium (DEAC) and triethylaluminium (TEA).

[0040] In another embodiment, the solid MAO support comprises additional compound selected from M(C ₆ F5) ₃ , wherein M is aluminium or boron, or M'R ₂ , wherein M' is zirconium or magnesium and R is (1-10C)alkyl (e.g. metyl or octyl).

[0041] In an embodiment, R ₃ and R ₄ are each independently hydrogen or (1-4C)alkyl, or R ₃ and R ₄ are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6-membered aromatic ring optionally substituted with one or more groups selected from (1-4C)alkyi, (2-4C)alkenyi, (2-4C)atkynyl, (1-4C)alkoxy, aryi,

SUBSTITUTE SHEET RULE 26 heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 - 4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino, nitro, cyano, (1 - 4C)alkylamino, [(1 -4C)alkyl] ₂ amino and -S(0) ₂ (1 -4C)alkyl; and

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6- membered aromatic ring optionally substituted with one or more groups selected from (1 - 4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino, nitro, cyano, (1 -4C)alkylamino, [(1 -4C)alkyl] ₂ amino and -S(0) ₂ (1 - 4C)alkyl.

[0042] In another embodiment, R ₃ and R ₄ are each independently hydrogen or (1 -4C)alkyl, or R3 and R4 are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6-membered aromatic ring optionally substituted with one or more groups selected from (1 -4C)alkyl, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro; and

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6- membered aromatic ring optionally substituted with one or more groups selected from (1 - 4C)alkyl, aryl, heteroaryl, carbocyclic and heterocyclic, wherein each aryl, heteroaryl, carbocyclic and heterocyclic group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro.

[0043] In another embodiment, R ₃ and R ₄ are each independently hydrogen or (1 -4C)alkyl, or R3 and R4 are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6-membered aromatic ring optionally substituted with one or more groups selected from (1 -4C)alkyl, aryl and heteroaryl, wherein each aryl and heteroaryl group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2- 4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro; and

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6- membered aromatic ring optionally substituted with one or more groups selected from (1 - 4C)alkyl, aryl and heteroaryl, wherein each aryl and heteroaryl group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 - 4C)alkoxy, halo, amino and nitro.

[0044] In another embodiment, R ₃ and R ₄ are each independently hydrogen or (1 -4C)alkyl, or R3 and R4 are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6-membered aromatic ring optionally substituted with one or more groups selected from (1 -4C)alkyl and phenyl, wherein each phenyl group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro; and

R ₅ and R ₆ are each independently hydrogen or (1 -4C)alkyl, or R ₅ and R ₆ are linked such that, when taken in combination with the atoms to which they are attached, they form a fused 6- membered aromatic ring optionally substituted with one or more groups selected from (1 - 4C)alkyl and phenyl, wherein each phenyl group is optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro.

[0045] In another embodiment:

i) when R ₃ and R ₄ are hydrogen or (1 -4C)alkyl, and R ₅ and R ₆ are linked to form a fused 6-membered aromatic ring, said ring is optionally substituted with one or two substituents as defined herein; or

ii) when R ₅ and R ₆ are hydrogen or (1 -4C)alkyl, and R ₃ and R ₄ are linked to form a fused 6-membered aromatic ring, said ring is optionally substituted with one or two substituents as defined herein.

[0046] In another embodiment, Ri is methyl and R2 is methyl or ethyl.

[0047] In another embodiment, Q is a bridging group comprising 1 , 2 or 3 bridging atoms selected from C, B, or Si, or a combination thereof, and is optionally substituted with one or more groups selected from hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl;

[0048] In another embodiment, Q is a bridging group comprising 1 , 2 or 3 bridging atoms selected from C, Si, or a combination thereof, and is optionally substituted with one or more groups selected from hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl.

[0049] In another embodiment, Q is a bridging group selected from -[C(R _a )(Rb)-C(R _c )(Rd)]- and -[Si(R _e )(Rf)]-, wherein R _a , Rt>, R _c , Rd, R _e and Rf are independently selected from hydrogen, hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl. Suitably, R _a , R _b , R _c and Rd are each hydrogen, and R _e and Rf are each independently (1 -6C)alkyl, (2-6C)alkenyl or phenyl. More suitably, R _a , Rt _> , _c and Rd are each hydrogen, and R _e and Rf are each independently (1 -4C)alkyl, (2-4C)alkenyl or phenyl.

In an embodiment, Q is a bridging group having the formula -[Si(R _e )(Rf)]-, wherein R _e and Rf are each independently selected from methyl, ethyl, propyl, allyl or phenyl. Suitably, Q is a bridging group having the formula -[Si(R _e )(Rf)]-, wherein R _e and Rf are each independently selected from methyl, ethyl, propyl and allyl. More suitably, R _e and Rf are each methyl.

[0050] In another embodiment, each Y group is independently selected from halo, hydride, a phosphonated, sulfonated or borate anion, or a (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 - 6C)alkoxy, aryl or aryloxy group which is optionally substituted with one or more groups selected from (1 -6C)alkyl, halo, nitro, amino, phenyl, (1 -6C)alkoxy, -C(0)NR _x R _y or Si[(1 - 4C)alkyl] ₃ , wherein R _x and R _y are independently (1 -4C)alkyl;

[0051] In another embodiment, each Y is independently selected from halo or a (1 -2C)alkyl or aryloxy group which is optionally substituted with one or more substituents selected from (1 -6C)alkyl, halo, phenyl, or Si[(1 -4C)alkyl] ₃ . Suitably, each Y is halo. More suitably, each Y is CI.

[0052] In another embodiment, one Y group is a phenoxy group optionally substituted with 1 , 2 or 3 groups independently selected from (1 -3C)alkyl, and the other Y group is halo.

[0053] In another embodiment, each Y is independently selected from halo or a (1 -2C)alkyl group which is optionally substituted with halo, phenyl, or Si[(1 -4C)alkyl] ₃ . Suitably, each Y is halo. More suitably, each Y is CI.

[0054] In another embodiment, X is zirconium or hafnium. Suitably, X is zirconium.

[0055] In another embodiment, the compound of formula (I) has any of formulae (II), (III) or (IV) shown below:

(IV) wherein:

Ri , R ₂ , R3, R4, R5, Re, Q, X and Y are each independently as defined in any of the paragraphs hereinbefore;

each R ₇ , Rs and R ₉ is independently selected from any of the ring substituents defined in any of the paragraphs hereinbefore (e.g. any of the substituents present on 6-membered aromatic rings formed when either or both of (i) R ₃ and R ₄ , and (ii) R ₅ and R ₆ , are linked); n, m and o are independently 0, 1 , 2, 3 or 4.

[0056] Suitably, n, m and o are independently 0, 1 , or 2. More suitably, n, m and o are independently 0, 1 or 2. [0057] In another embodiment, in formulae (II), (III) or (IV), each R ₇ , Rs and R ₉ is independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2- 4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro.

[0058] Suitably, in formulae (II), (III) or (IV), each R ₇ , Rs and R ₉ is independently selected from hydrogen, methyl, n-butyl, tert-butyl and unsubstituted phenyl.

[0059] In another embodiment, in formula (II), (III) or (IV), Ri is methyl and R2 is methyl or ethyl.

[0060] In another embodiment, in formula (II), (III) or (IV), Q is a bridging group selected from -[C( R _a )( Rb)-C(Rc)(Rd)]- and -[Si(R _e )( Rf)]-, wherein R _a , R _b , R _c , Rd, R _e and R _f are independently selected from hydrogen, hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl. Suitably, Q is a bridging group -[Si(R _e )( Rf)]-, wherein R _e and Rf are independently selected from hydrogen, hydroxyl and (1 -6C)alkyl. More suitably, Q is a bridging group - [Si( R _e ) (Rf)]-, wherein R _e and Rf are independently selected from (1 -6C)alkyl (e.g. methyl, ethyl, propyl or allyl).

[0061] In a particular embodiment, the compound of formula (I) has any of formulae (II), (III) or (IV), wherein

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro;

n, m and o are each independently 1 or 2;

Q is a bridging group selected from -[C( R _a ) (Rb)-C(R _c ) (R _d )]- and -[Si(R _e )(Rf)]-, wherein R _a , R _b , Rc, Rd, R _e and Rf are independently selected from hydrogen, hydroxyl, (1 -6C)alkyl, (2- 6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl;

each Y is independently selected from halo or a (1 -2C)alkyl group which is optionally substituted with halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0062] In another particular embodiment, the compound has any of formulae (II), (III) or (IV), wherein

Ri and R ₂ are each independently (1 -2C)alkyl; R ₃ , FU, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro;

n, m and o are each independently 1 or 2;

Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from hydrogen, hydroxyl and (1 -6C)alkyl;

each Y is independently selected from halo, (1 -2C)alkyl, or an aryloxy group which is optionally substituted with one or more substituents selected from (1 -4C)alkyl, halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0063] In another particular embodiment, the compound has any of formulae (II), (III) or (IV), wherein

Ri is methyl and R2 is methyl or ethyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro;

n, m and o are each independently 1 or 2;

Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from hydrogen, hydroxyl and (1 -6C)alkyl;

each Y is independently selected from halo, (1 -2C)alkyl, or an aryloxy group which is optionally substituted with one or more substituents selected from (1 -4C)alkyl, halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0064] In another particular embodiment, the compound has any of formulae (II), (III) or (IV), wherein

Ri is methyl and R2 is methyl or ethyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl; R ₇ , Rs and R ₉ are each independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro;

n, m and o are each independently 1 or 2;

Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from (1 - 6C)alkyl;

each Y is independently selected from halo, (1 -2C)alkyl, or an aryloxy group which is optionally substituted with one or more substituents selected from (1 -4C)alkyl, halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0065] In another embodiment, the compound of formula (I) has any of formulae (V), (VI) or (VII) shown below:

wherein

Ri , R ₂ , R3, R5, Re, Q, X and Y are each independently as defined in any of the paragraphs hereinbefore;

R ₇ , Rs and R ₉ are each independently as defined in any of the paragraphs hereinbefore; and

R ₄ is as defined in any of the paragraphs hereinbefore. Suitably, R ₄ is hydrogen.

[0066] Suitably, each R ₇ , Rs and R ₉ in formulae (V), (VI) or (VII) is independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro. [0067] Suitably, each R ₇ , Rs and R ₉ in formulae (V), (VI) or (VII) is independently selected from hydrogen, methyl, n-butyl, tert-butyl and unsubstituted phenyl.

[0068] In another embodiment, in formulae (V), (VI) or (VII), Q is a bridging group selected from -[C(R _a )(Rb)-C(Rc)(Rd)]- and -[Si(R _e )(R _f )]-, wherein R _a , R _b , R _c , Rd, R _e and R _f are independently selected from hydrogen, hydroxyl, (1 -6C)alkyl, (2-6C)alkenyl, (2-6C)alkynyl, (1 - 6C)alkoxy and aryl. Suitably, Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from hydrogen, hydroxyl and (1 -6C)alkyl. More suitably, Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from (1 -6C)alkyl (e.g. methyl, ethyl, propyl or allyl).

[0069] In another embodiment, in formula (V), (VI) or (VII), Ri is methyl and R2 is methyl or ethyl.

[0070] In a particular embodiment, the compound of formula (I) has any of formulae (V), (VI) or (VII), wherein

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, (1 -4C)alkyl and phenyl, said phenyl group being optionally substituted with one or more groups selected from (1 -4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1 -4C)alkoxy, halo, amino and nitro;

Q is a bridging group selected from -[C(R _a )(Rb)-C(R _c )(R _d )]- and -[Si(R _e )(Rf)]-, wherein R _a , R _b , Rc, Rd, R _e and Rf are independently selected from hydrogen, hydroxyl, (1 -6C)alkyl, (2- 6C)alkenyl, (2-6C)alkynyl, (1 -6C)alkoxy and aryl;

each Y is independently selected from halo or a (1 -2C)alkyl group which is optionally substituted with halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0071] In another particular embodiment, the compound of formula (I) has any of formulae (V), (VI) or (VII), wherein

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, methyl, n-butyl, tert-butyl and unsubstituted phenyl; Q is a bridging group selected from -[C(R _a )(Rb)-C(R _c )(R _d )]- and -[Si(R _e )(Rf)]-, wherein R _a , R _b , Rc and Rd are each hydrogen, and R _e and Rf are each independently (1 -6C)alkyl, (2- 6C)alkenyl or phenyl;

each Y is independently selected from halo or a (1 -2C)alkyl group which is optionally substituted with halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0072] In another particular embodiment, the compound has any of formulae (V), (VI) or (VII), wherein

Ri and R ₂ are each independently (1 -2C)alkyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, methyl, n-butyl, tert-butyl and unsubstituted phenyl;

Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from hydrogen, hydroxyl and (1 -6C)alkyl;

each Y is independently selected from halo, (1 -2C)alkyl, or an aryloxy group which is optionally substituted with one or more substituents selected from (1 -4C)alkyl, halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium.

[0073] In another particular embodiment, the compound has any of formulae (V), (VI) or (VII), wherein

Ri is methyl and R2 is methyl or ethyl;

R ₃ , R4, R5 and R ₆ are each independently hydrogen or (1 -4C)alkyl;

R ₇ , Rs and R ₉ are each independently selected from hydrogen, methyl, n-butyl, tert-butyl and unsubstituted phenyl;

Q is a bridging group -[Si(R _e )(Rf)]-, wherein R _e and Rf are independently selected from hydrogen, hydroxyl and (1 -6C)alkyl;

each Y is independently selected from halo, (1 -2C)alkyl, or an aryloxy group which is optionally substituted with one or more substituents selected from (1 -4C)alkyl, halo, phenyl, or Si[(1 -4C)alkyl] ₃ ; and

X is zirconium or hafnium. [0074] in another particular embodiment, the compound has any of formulae (V), (VI) or (VII), wherein

R is methyl and R ₂ is methyl or ethyl;

R3, R4, R5 and R ₆ are each independently hydrogen or (1-4C)alkyl;

R ₇ , R ₈ and R ₉ are each independently selected from hydrogen, (1-4C)alky! and phenyl, said pheny! group being optionally substituted with one or more groups selected from (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, halo, amino and nitro;

n, m and o are each independently 1 or 2;

Q is a bridging group -[Si(R _e )(R _f )]-, wherein R _e and R _f are independently selected from (1- 6C)alkyl;

each Y is independently selected from halo, (1 -2C)alkyI, or an aryloxy group which is optionally substituted with one or more substituents selected from (1-4C)alkyl, halo, phenyl, or Si[(1-4C)aikyl] ₃ ; and

X is zirconium or hafnium.

[0075] In another embodiment, the compound of formula I has any of the following structures:

[0076] In another embodiment, the compound of formula (I) has the following structure:

SUBSTITUTE SHEET RULE 26

[0077] In another aspect, the present invention provides a compound of formula (I) as defined hereinbefore.

Synthesis

[0078] The compounds forming part of the present invention may be synthesised by any suitable process known in the art. Particular examples of processes for the preparing compounds forming part of the present invention are set out in the accompanying examples.

[0079] Suitably, a compound of the present invention is prepared by:

(i) reacting a compound of formula A:

(wherein Ri , R ₂ , R3, R4, R5, Re and Q are each as defined hereinbefore and M is Li, Na or K)

with a compound of the formula B:

X(Y') ₄

B (wherein X is as defined hereinbefore and Y' is halo (particularly chloro or bromo)) in the presence of a suitable solvent to form a compound of formula (la):

la and optionally thereafter:

(ii) reacting the compound of formula la above with MY" (wherein M is as defined above and Y" is a group Y as defined herein other than halo), in the presence of a suitable solvent to form the compound of the formula (lb) shown below

lb

[0080] Suitably, M is Li in step (i) of the process defined above.

[0081] Suitably, the compound of formula B is provided as a solvate. In particular, the compound of formula B may be provided as X(Y') ₄ .THFp, where p is an integer (e.g. 2).

[0082] Any suitable solvent may be used for step (i) of the process defined above. A particularly suitable solvent is toluene or THF. [0083] If a compound of formula (I) in which Y is other than halo is required, then the compound of formula (la) above may be further reacted in the manner defined in step (ii) to provide a compound of formula (lb).

[0084] Any suitable solvent may be used for step (ii) of the process defined above. A suitable solvent may be, for example, diethyl ether, toluene, THF, dicloromethane, chloroform, hexane DMF, benzene etc.

[0085] Compounds of formula A, in which Q is -[Si(R _e )(R _f )]-, may generally be prepared by:

(i) Reacting a compound of formula D

D

(wherein M is lithium, sodium, or potassium ; and Ri and R ₂ are as defined hereinbefore) with one equivalent of a compound having formula E shown below:

E

(wherein R _e and Rf are as defined hereinbefore)

to form the compound of the formula F shown below:

F

(ii) Reacting the compound of formula F with a compound of formula G shown below:

G

(wherein R ₃ , FU, R5 and Re are as defined hereinbefore, and M is lithium, sodium or potassium).

[0086] Compounds of formulae D and G can be readily synthesized by techniques well known in the art.

[0087] Any suitable solvent may be used for step (i) of the above process. A particularly suitable solvent is THF.

[0088] Similarly, any suitable solvent may be used for step (ii) of the above process. A suitable solvent may be, for example, toluene, THF, DMF etc.

[0089] A person of skill in the art will be able to select suitable reaction conditions (e.g. temperature, pressures, reaction times, agitation etc.) for such a synthesis.

[0090] Compounds of formula A, in which Q is -CH2-CH2-, may generally be prepared by:

(i) Reacting a compound of formula D

D

(wherein M is lithium, sodium, or potassium ; and Ri and R ₂ are as defined hereinbefore) with an excess of BrCH ₂ CH ₂ Br to form a compound of the formula H shown below:

H

(wherein Ri and R ₂ are as defined hereinbefore); and

Reacting the compound of formula H with a compound of formula G shown below:

G

(wherein R ₃ , R4, R5 and Re are as defined hereinbefore, and M is lithium, sodium or potassium)

[0091 ] Compounds of formulae D and G can be readily synthesized by techniques well known in the art.

[0092] Any suitable solvent may be used for step (i) of the above process. A particularly suitable solvent is THF.

[0093] Similarly, any suitable solvent may be used for step (ii) of the above process. A suitable solvent may be, for example, toluene, THF, DMF etc.

[0094] A person of skill in the art will be able to select suitable reaction conditions (e.g. temperature, pressures, reaction times, agitation etc.) for such a synthesis.

Applications

[0095] As previously indicated, the compositions of the present invention are extremely effective as catalysts in polyethylene homopolymerization and copolymerisation reactions. [0096] As discussed hereinbefore, the compositions of the invention exhibit superior catalytic performance when compared with current metallocene compounds used in the polymerisation of a-olefins. In particular, when compared with analogous silica-supported methyl aluminoxane (SSMAO) and layered double hydroxide-supported methyl aluminoxane (LDHMAO) catalyst compositions, the solid MAO compositions of the invention exhibit significantly increased catalytic activity in the homopolymerisation and copolymerisation of a- olefins. Moreover, polymers produced by a-olefin polymerization in the presence of compositions of the invention are typically of a higher molecular weight than polymers prepared using other catalysts, without an attendant increase in polydispersity. Such materials are highly valued by industry. Furthermore, polyethylene copolymers produced by a-olefin polymerization in the presence of compositions of the invention demonstrate good co-monomer incorporation in polyethylene, with good inter-molecular uniformity.

[0097] Thus, as discussed hereinbefore, the present invention also provides the use of a composition defined herein as a polymerization catalyst, in particular in the preparation of polyethylene.

[0098] In one embodiment, the polyethylene is a homopolymer made from polymerized ethene monomers.

[0099] In another embodiment, the polyethylene is a copolymer made from polymerized ethene monomers comprising 1 -10 wt% of (4-8C) α-olefin (by total weight of the monomers). Suitably, the (4-8C) α-olefin is 1 -butene, 1 -hexene, 1 -octene, or a mixture thereof.

[00100] In another embodiment, the polyethylene is a polyethylene wax. Polyethylene wax will be understood by one of skill in the art as being low molecular weight polyethylene, typically having an average molecular weight of 1000-15,000 Da. Suitably, the polyethylene wax has an average molecular weight of 1000-6000 Da.

[00101 ] As discussed hereinbefore, the present invention also provides a process for forming a polyolefin (e.g. a polyethylene) which comprises reacting olefin monomers in the presence of a composition defined herein.

[00102] In another embodiment, the olefin monomers are ethene monomers.

[00103] In another embodiment, the olefin monomers are ethene monomers comprising 1 -10 wt% of (4-8C) α-olefin (by total weight of the monomers). Suitably, the (4-8C) α-olefin is 1 - butene, 1 -hexene, 1 -octene, or a mixture thereof.

[00104] In another embodiment, the polyolefin is a polyethylene wax, which is formed by reacting ethene monomers and H ₂ in the presence of a composition as defined herein. Optionally, quantities of 1 -butene may be included together with the ethene monomers and H ₂ .

[00105] A person skilled in the art of olefin polymerization will be able to select suitable reaction conditions (e.g. temperature, pressures, reaction times etc.) for such a polymerization reaction. A person skilled in the art will also be able to manipulate the process parameters in order to produce a polyolefin having particular properties.

[00106] In a particular embodiment, the polyolefin is polyethylene.

EXAMPLES

[00107] Examples of the invention will now be described, for the purpose of reference and illustration only, with reference to the accompanying figures, in which:

Fig. 1 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of pro-ligand

[EB( ^tBu2 Flu,l ^* )H ₂ ].

Fig. 2 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of pro-ligand

Fig. 3 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of pro-ligand

Fig. 4 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of pro-ligand

[Me,Propyl _S j(| _nd* ) _C |]_

Fig. 5 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of pro-ligand

[SB(Flu,l ^* )H ₂ ].

Fig. 6 shows the Molecular structure of [SB( ^tBu 2Flu, )H ₂ ], 50% ellipsoids, hydrogen atoms omitted for clarity; black: carbon, pink: silicon. Selected bond lengths (A) and angle (°), Si- CH ₃ 1 .863(3), 1 .868(3), Si-CH _Ru : 1 .939(2), Si-CHm _d : 1 .926(2) and HC _F i _u -Si-CHind: 1 1 1 .34(12).

Fig. 7 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of

[SB( ^tBu 2Flu,l*)ZrCI ₂ ].

Fig. 8 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of

[SB( ^tBu 2Flu,l ^* )HfCI ₂ ].

Fig. 9 shows the molecular structure of [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ]. Fig. 10 shows the molecular structure of [SB( ^tBu 2Flu,l ^* )HfCI ₂ ]. Fig. 1 1 shows polymerisation productivity (Kg(PE)g(Cat) ^~1 h ^~1 ) vs time (sec) for the homopolymerisation of ethylene using Solid MAO supported catalytic systems: (a) rac- [(EBI ^* )ZrCI ₂ ], (b) meso-[(EBr)ZrCI ₂ ], (c) rac-[(SBI ^* )ZrCI ₂ ], and (d) [SB( ^tBu2 Flu,r)ZrCI ₂ ].

Polymerisation conditions: 5 mL heptane, P _e th _y iene = 120 psi, 7=70 °C and n _(T EA) = 10 μηιοΙ.

Fig. 12 shows polymerisation productivity (Kg(PE)g(Cat) ^~1 h ^_1 ) vs time (sec) for the homopolymerisation of ethylene using Solid MAO supported catalytic systems: (a) rac- [(EBI ^* )ZrCI ₂ ], (b) meso-[(EBI ^* )ZrCI ₂ ], (c) rac-[(SBI ^* )ZrCI ₂ ], and (d) [SB( ^tBu2 Flu,l ^* )ZrCI ₂ ].

Polymerisation conditions: 5 mL heptane, Pethyiene = 120 psi, 7=80 °C and n _(T EA) = 10 μηιοΙ.

Fig. 13 shows activity vs time for the copolymerisation of ethylene and 1 -hexene using Solid MAO supported catalytic systems: (a) rac-[(EBI ^* )ZrCI ₂ ], (b) meso-[(EBI ^* )ZrCI ₂ ] (c) rac- [(SBI ^* )ZrCI ₂ ], (d) [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ]. Polymerisation conditions: 5 mL heptane, Pethyiene = 120 psi, 7= 70 °C, [Hexene]feed = 5 vol%, and n _(T EA) = 15 μηιοΙ.

Fig. 14 shows activity vs time for the copolymerisation of ethylene and 1 -hexene using Solid MAO supported catalytic systems with variation of the 1 -hexene feed. Polymerisation conditions: 5 mL heptane, P ethylene 120 psi, 7= 70 °C, and n _(TE A) = 15 μηιοΙ.

Fig. 15 shows activity vs time for the copolymerisation of ethylene and 1 -hexene using Solid MAO supported catalytic systems with variation of the 1 -hexene feed. Polymerisation conditions: 5 mL heptane, P ethylene 80 psi, 7= 70 °C, and n _(T EA) = 15 μηιοΙ.

Fig. 16 shows the molecular structure of ^Et2 SB( ^tBu 2Flu,l ^* )ZrCI ₂ .

Fig. 17 shows the molecular structure of ^{Me Prop} SB( ^tBu 2Flu,r)ZrCI ₂ .

Fig. 18 shows the molecular structure of SB( ^tBu 2Flu,r- ^{3 ethyl} )ZrCI ₂ .

Fig. 19 shows the molecular structure of SB(Cp,l ^* )ZrCI ₂ .Fig. 20 shows

Fig. 20 shows the molecular structure of SB(Cp,l ^* )HfCI ₂ .

Fig. 21 shows the molecular structure of SB(Cp,r)ZrCI(0-2,6-Me ₂ -C ₆ H ₃ ).

Fig. 22 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of

E ^t2 SB( ^tBu 2Flu,l ^* )ZrCI ₂ .

Fig. 23 shows the ¹ H NMR spectroscopy (chloroform-cd , 298 K, 400 MHz) of

Me,Prop _{S B} (tBu _2F | _u J _* ) _ZrC | ₂ _

Fig. 24 shows the ¹ H NMR spectroscopy (chloroform-c/i, 298 K, 400 MHz) of SB( ^tBu 2Flu,r- ³ -

Fig. 25 shows the ¹ H NMR spectroscopy (chloroform-c/i, 298 K, 400 MHz) of SB(Cp,l ^* )ZrCI ₂ . Fig. 26 shows the ¹ H NMR spectroscopy (chloroform-οΊ , 298 K, 400 MHz) of SB(Cp,l ^* )HfCI ₂ .

Fig. 27 shows the ¹ H NMR spectroscopy (chloroform-c/i, 298 K, 400 MHz) of

SB(Cp,r)ZrCI(0-2,6-Me ₂ -C ₆ H ₃ ).

Fig. 28 shows activity vs time of polymerisation of ethylene using solid MAO supported/ SB( ^tBu2 Flu, l ^* )ZrCI ₂ (square), solid MAO supported/ SB^FIuJ'^^ZrCfe (circle), solid MAO supported/ ^Et2 SB( ^tBu2 Ru,l ^* )ZrCI ₂ (triangle), solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ (inverted triangle) and solid MAO supported/ ^Me - ^Pr ° ^P SB( ^tBu 2Flu,r)ZrCI ₂ (diamond). Polymerisation conditions: 10 mg of catalyst, 50 mL hexanes, 2 bar, 70 °C, and [TIBA] ₀ /[Zr] ₀ = 1000.

Fig. 29 shows activity vs temperature of polymerisation of ethylene using solid MAO supported/ SB( ^tBu2 Flu,l ^* )ZrCI ₂ (square), solid MAO supported/ SB( ^tBu2 Flu,r- ^{3 Ethyl} )ZrCI ₂ (circle), solid MAO supported/ ^Et2 SB( ^tBu 2Flu,l ^* )ZrCI ₂ (triangle), solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ (inverted triangle) and solid MAO supported/ ^{Me Prop} SB( ^tBu2 Flu,r)ZrCI ₂ (diamond).

Polymerisation conditions: 10 mg of catalyst, 50 mL hexanes, 2 bar, 0.5 h, and [TIBA] ₀ /[Zr] ₀ = 1000.

Fig. 30 shows activity vs time of polymerisation of ethylene using solid MAO supported/ SB( ^tBu 2Flu,l ^* )ZrCI ₂ (square) and solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ (circle). Polymerisation conditions: 10 mg of catalyst, 50 mL hexanes, 2 bar, 70 °C, and [TIBA] ₀ /[Zr] ₀ = 1000.

Fig. 31 shows SEM pictures of a) solid MAO supported/ ^Et2 SB( ^tBu2 Flu,l ^* )ZrCI ₂ , b) solid MAO supported/ ^{Me Pr} ° ^P SB( ^tBu2 Flu,r)ZrCI ₂ , c) solid MAO supported SB( ^tBu2 Flu,l ^* )ZrCI ₂ , d) solid MAO supported SB( ^tBu 2Flu,l ^* )HfCI ₂ , e) solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ and f) solid MAO supported/ SB( ^tBu2 Flu,l ^* ' ^{3 Ethyl} )ZrCI ₂ . Polymerisation conditions: 10 mg of catalyst, 50 mL hexanes, 2 bar, 70 °C, 0.5 h and [TIBA] ₀ /[Zr] ₀ = 1000.

Fig. 32 shows activity vs time of polymerisation of ethylene using 3% H ₂ used as co-feed using solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ , solid MAO supported/ ( ^nBu Cp) ₂ ZrCI ₂ and solid MAO supported/ (lnd) ₂ ZrCI ₂ . Polymerisation conditions: 25 mg of catalyst, 1000 mL hexanes, 8 bar, 80 °C, and [TEA] ₀ /[Zr] ₀ = 300.

Fig. 33 shows activity and molecular weight vs H ₂ content used as co-feed using solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ . Polymerisation conditions: 0.05 mg of catalyst, 5 mL heptane, 8 bar and 80 °C.

Fig. 34 shows activity and molecular weight vs H ₂ content as co-feed using solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ . Polymerisation conditions: 25 mg of catalyst, 1000 mL hexanes, 8 bar, 80 °C, and [TEA] ₀ /[Zr] ₀ = 300. Fig. 35 shows activity of homopolymerisation of ethylene and copolymerisation of ethylene and 1 -hexene using solid MAO supported/ ^Et2 SB( ^tBu2 Flu,r)ZrCI ₂ , solid MAO supported/ SB(Cp,r)ZrCI ₂ , solid MAO supported/ ^Me - ^Pr ° ^P SB( ^tBu2 Flu,r)ZrCI ₂ , solid MAO supported

SB( ^tBu2 Flu,r)ZrCI ₂ , solid MAO supported/ SB^FIuJ'^^ZrCfe, solid MAO supported SB( ^tBu 2Flu,l ^* )HfCI ₂ , and solid MAO supported/ SB(Cp,l ^* )HfCI ₂ . Polymerisation conditions: 0.05 mg of catalyst, 5 mL heptane, 8 bar and 80 °C.

Nomenclature

[00108] The nomenclature used herein will be readily understood by the skilled person having regard to the relevant structural formulae. Various abbreviations used throughout are expanded below:

SB means (Me) ₂ Si-bridged. Similarly, ^Et2 SB means (Et) ₂ Si-bridged

EB means ethylene-bridged

Ind* or I* means per-methyl indenyl

Flu means fluorenyl

tBu means tert-butyl

Me means methyl

Pr means propyl

iPr means isopropyl

Ph means phenyl

General Methodology

[00109] All organometallic manipulations were performed under an atmosphere of N ₂ using standard Schlenk line techniques or a MBraun UNIlab glovebox, unless stated otherwise. All organic reactions were carried out under air unless stated otherwise. Solvents used were dried by either reflux over sodium-benzophenone diketyl (THF), or passage through activated alumina (hexane, Et ₂ 0, toluene, CH ₂ CI ₂ ) using a MBraun SPS-800 solvent system. Solvents were stored in dried glass ampoules, and thoroughly degassed bypassage of a stream of N ₂ gas through the liquid and tested with a standard sodium-benzophenone-THF solution before use. Deuterated solvents for NMR spectroscopy of oxygen or moisture sensitive materials were treated as follows: C ₆ D ₆ was freeze-pump-thaw degassed and dried over a K mirror; d ⁵ - pyridine and CDCI ₃ were dried by reflux over calcium hydride and purified by trap-to-trap distillation; and CD2CI2 was dried over 3 A molecular sieves.

[00110] ¹ H and ¹³ C NMR spectroscopy were performed using a Varian 300 MHz spectrometer and recorded at 300 K unless stated otherwise. ¹ H and ¹³ C NMR spectra were referenced via the residual protio solvent peak. Oxygen or moisture sensitive samples were prepared using dried and degassed solvents under an inert atmosphere in a glovebox, and were sealed in Wilmad 5mm 505-PS-7 tubes fitted with Young's type concentric stopcocks.

[00111 ] Mass spectra were using a Bruker FT-ICR-MS Apex III spectrometer.

[00112] For Single-crystal X-ray diffraction in each case, a typical crystal was mounted on a glass fibre using the oil drop technique, with perfluoropolyether oil and cooled rapidly to 150 K in a stream of N ₂ using an Oxford Cryosystems Cryostream ¹ . Diffraction data were measured using an Enraf-Nonius KappaCCD diffractometer (graphite-monochromated MoKa radiation, λ = 0.71073 A). Series of ω-scans were generally performed to provide sufficient data in each case to a maximum resolution of 0.77 A. Data collection and cell refinement were carried out using DENZO-SMN ² . Intensity data were processed and corrected for absorption effects by the multi-scan method, based on multiple scans of identical and Laue equivalent reflections using SCALEPACK (within DENZO-SMN). Structure solution was carried out with direct methods using the program SIR92 ³ . within the CRYSTALS software suite ⁴ . In general, coordinates and anisotropic displacement parameters of all non-hydrogen atoms were refined freely except where this was not possible due to the presence of disorder. Hydrogen atoms were generally visible in the difference map and were treated in the usual manner ⁵ .

[00113] High temperature gel permeation chromatography were performed using a Polymer Laboratories GPC220 instrument, with one PLgel Olexis guard plus two Olexis 30 cm x 13 μηι columns. The solvent used was 1 ,2,4-trichlorobenzene with anti-oxidant, at a nominal flow rate of 1 .0 mLmin ^-1 and nominal temperature of 160 0. Refractive index and Viscotek differential pressure detectors were used. The data were collected and analysed using Polymer Laboratories "Cirrus" software. A single solution of each sample was prepared by adding 15mL of solvent to 15mg of sample and heating at 190 °C for 20 minutes, with shaking to dissolve. The sample solutions were filtered through a glass-fibre filter and part of the filtered solutions were then transferred to glass sample vials. After an initial delay of 30 minutes in a heated sample compartment to allow the sample to equilibrate thermally, injection of part of the contents of each vial was carried out automatically. The samples appeared to be completely soluble and there were no problems with either the filtration or the chromatography of the solutions. The GPC system was calibrated with Polymer Laboratories polystyrene calibrants. The calibration was carried out in such a manner that combined GPC- viscosity could be used to give 'true' molecular weight data and conventional GPC could also be applied. For the conventional GPC results, the system is calibrated with linear polyethylene or linear polypropylene. This correction has previously been shown to give good estimates of the true molecular weights for the linear polymers.

Synthesis of Unsymmetrical Pro-ligands

Synthesis of ethylene-bridged [EB( ^tBu2 Flu.r)H _P l

[001 14] Having regard to Scheme 1 shown below, reaction of one equivalent of [(lnd ^# )H] with an excess of 1 ,2-dibromoethane afforded [(lnd*)CH ₂ CH ₂ Br] which was reacted with one equivalent of [( ^tBu 2Flu)Li] to afford the new ethylene-bridged pro-ligand, [EB( ^tBu 2Flu, )H ₂ ], as a colourless solid in good yield. Figure 1 provides the ¹ H NMR spectrum for EB( ^tBu 2Flu, )H ₂ ].

[EB( ^,Bu2 Flu,l*)H ₂ 3

Scheme 1 - Synthesis of [EB( ^tBu 2Flu, l*)H ₂ ] ethylene-bridged pro-ligand

[001 15] Having regard to Scheme 2 shown below, various silicon-bridged unsymmetrical pro-ligands were accessed using the silane synthon, [ ^{R R'} Si(lnd*)CI]. Figures 2, 3 and 4 show the Ή NMR spectra for [ ^Me 2Si(lnd*)CI], [ ^iPr 2Si(lnd*)CI] and [ ^{Me Pr} Si(lnd*)CI] respectively.

E<lnd ^# )i_il [ ^RR, Si(ind*)Ci]

Scheme 2 - synthesis of [ ^R' Si(lnd ^* )CI]

[00116] Having regard to Scheme 3 shown below, the synthesised silane synthon [ ^Me 2Si(lnd ^* )CI] was separately reacted with one equivalent of [( ^tBu 2Flu)Li], [(Flu)Li], and

[( ^Me ' ^Ph lnd)Li] to afford the new Si-bridged pro-ligands [SB( ^tBu 2Flu,r)H ₂ ], [SB(Flu,l ^* )H ₂ ] and [SB( ^Me ' ^Ph lnd,l*)H ₂ ] respectively as colourless solids in very good yields. Fig. 5 shows the ¹ H NMR spectrum for [SB(Flu,l ^* )H ₂ ]. Fig. 6 shows the X-ray crystallographic structure for

[SB( ^M6 _' ^Ph fnd,r)H ₂ ]

Scheme 3 - Synthesis of [SB( ^tBu 2Flu,l ^* )H ₂ ], [SB(Flu,l ^* )H ₂ ] and [SB( ^{Me Ph} lnd,l ^* )H ₂ ] Si-bridged pro-ligands Synthesis of unsymmetrical pro-catalysts

Synthesis of rSB( ^tBu 2Flu,nZrCI _? l and [SB( ^tBu 2Flu,r)HfCI _? l

[00117] Having regard to Scheme 4 shown below, stoichiometric reactions of [SB( ^tBu 2Flu, )Li ₂ ] with MCU (M = Zr and Hf) were carried out in benzene at room temperature overnight to afford [SB( ^tBu 2Flu, )MCI ₂ ] as bright orange solids in good yields. Figs. 7 and 8 show the ¹ H NMR spectra of [SB( ^tBu 2Flu,r)ZrCI ₂ ] and [SB( ^tBu 2Flu,r)HfCI ₂ ] respectively. Single crystals of [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ] and [SB( ^tBu 2Flu,l ^* )HfCI ₂ ] suitable for X-ray crystallography were obtained by crystallisation in n-hexane solution at -30 °C. Figs. 9 and 10 show the X-ray crystallographic structures for [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ] and [SB( ^tBu 2Flu,l ^* )HfCI ₂ ] respectively

[SB{ ^48u2 Fiu,r)ZrCia]

Scheme 4 - synthesis of [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ] and [SB( ^tBu 2Flu,l ^* )HfCI ₂ ] Si-bridged pro-catalysts

Synthesis of ^Et2 SB( ^tBu 2Flu.nZrCI ₂ and ^Me - ^Pr ° ^P SB( ^tBu 2Flu.nZrCI _?

[00118] Having regard to Scheme 5 outlined below, ^Et2 SB( ^tBu 2Flu,l ^* )ZrCI ₂ and Me,Prop _{S B} (tBu _2F | _u j*) _ZrC | ₂ si-bridged Zr pro-catalysts were prepared in 18% and 41 % yields respectively.

Scheme 5 - synthesis of ^Et2 SB( ^tBu 2Flu,r)ZrCI ₂ and ^Me ' ^Pr ° ^P SB( ^tBu 2Flu,r)ZrCI ₂ Si-bridged pro- catalysts

Synthesis of SB( ^tBu 2Flu.r- ^{3 Ethyl} )ZrCI _?

[00119] Having regard to Scheme 6 outlined below, SB( ^tBu 2Flu,r- ^{3 Ethyl} )ZrCl2 Si-bridged Zr pro-catalyst was prepared.

Scheme 6 - synthesis of SB( ^tBu 2Flu,r' ^{3 Ethyl} )ZrCI ₂ Si-bridged pro-catalyst

Synthesis of SBfCp.nZrCI?

[00120] Having regard to Scheme 7 below, toluene (40 ml) was added to a LiCp (246 mg, 3.41 mmol) and lnd ^* SiMe ₂ CI (1 g, 3.41 mmol) in a Schlenk tube, dissolved in -5 °C THF (50 mL) and left to stir for two hours. "BuLi (4.7 mL, 1 .6 M in hexanes, 7.51 mmol) was added, dropwise, over 30 minutes and the reaction left to stir for 12 hours. The solvent was removed in vacuo and the residue washed with pentane (3 x 40 mL) and dried to afford a grey powder. One equivalent of ZrCI ₄ (796 mg, 3.41 mmol) was added and the mixture dissolved in benzene and left to stir for sixty hours. The solution changed colour from green, to orange and finally red/brown. The solvent was removed under vacuum and the product extracted with pentane (3 x 40 mL) and filtered through Celite. The filtrate was concentrated in vacuo and stored at -34 °C. This yielded SB(Cp,l*)ZrCl2 as an orange/brown precipitate in 23% yield (365 mg, 0.76 mmol). Orange crystals, suitable for single crystal X-ray diffraction, were grown from a concentrated solution in hexanes at -34 °C.

¹ H NMR (de-benzene): δ 6.59 (2H, dm, CpH), 5.60 (2H, dm, CpH), 2.52 (3H, s, ArMe), 2.48 (3H, s, ArMe), 2.26 (3H, s, ArMe), 2.15 (3H, s, ArMe), 2.05 (3H, s, ArMe), 1 .97 (3H, s, ArMe), 0.72 (3H, s, SiMe), 0.64 (3H, s, SiMe).

¹³ C{ ¹ H} NMR (de-benzene): δ 135.65 (Ar), 135.13 (Ar), 134.86 (Ar), 131 .1 1 (Ar), 131 .50 (Ar), 131 .15 (Ar), 129.16 (Ar), 126.35 (Ar), 125.92 (ArSi), , 1 15.87 (CpH), 106.49 (CpH), 84.01 (CpSi), 21 .69 (ArMe), 17.91 (ArMe), 17.64 (ArMe), 17.16 (ArMe), 16.92 (ArMe), 15.97 (ArMe), 5.59 (SiMe), 3.26 (SiMe).

MS (El): Predicted: m/z 482.0372. Observed: m/z 482.0371 . IR (KBr) (cm ¹ ): 2961 , 2925, 1543, 1260, 1029, 809, 668.

CHN Analysis (%): Expected: C 54.74, H 5.85, Found: C 54.85, H 5.94.

23% yteki

Scheme 7 - synthesis of SB(Cp, )ZrCI ₂ Si-bridged pro-catalyst

Synthesis of SB(Cp,l ^* )HfClp

[00121 ] Having regard to Scheme 8 below, SB(Cp,l ^* )Li ₂ (1 g, 2.99 mmol) and HfCU (958 mg, 2.99 mmol) were added to a Schlenk tube. Benzene (100 mL) was added and the reaction was left to stir for 60 hours. The solution changed colour from brown to yellow. The solvent was the removed under vacuum and the product was extracted with pentane (3 x 40 mL) and filtered through Celite. The filtrate was concentrated in vacuo and stored at -34 °C yielding SB(Cp,l ^* )HfCl2 as yellow crystals, suitable for single crystal X-ray diffraction, in 24% yield (360 mg, 0.632 mmol).

¹ H NMR (cfe-benzene): δ 6.54 (3H, dm, CpH), 5.53 (3H, dm, CpH), 2.57 (3H, s, ArMe), 2.56 (3H, s, ArMe), 2.25 (3H, s, ArMe), 2.20 (3H, s, ArMe), 2.09 (3H, s, ArMe), 2.03 (3H, s, ArMe), 0.65 (3H, s, SiMe), 0.57 (3H, s, SiMe). ¹³ C{ ¹ H} NMR (de-benzene): δ 134.55 (Ar), 134.18 (Ar), 133.51 (Ar), 131 .73 (Ar), 131 .05 (Ar), 129.64 (Ar), 126.23 (Ar), 125.18 (Ar), 124.38 (Ar), 1 13.33 (C _P H), 107.32 (C _P H), 82.33 (C _p Si), 21 .53 (ArMe), 17.68 (ArMe), 17.37 (ArMe), 16.77 (ArMe), 16.64 (ArMe), 15.51 (ArMe), 5.00 (SiMe), 3.00 (SiMe).

MS (El): Predicted: m/z 570.0785. Observed: m/z 570.0701 . IR (KBr) (cm ¹ ): 2960, 2923, 1542, 1262, 1028, 812, 670.

CHN Analysis (%): Expected: C 46.36, H 4.95, Found: C 46.52, H 5.04.

5B(Cp,S*}U ₂

24% yield

Scheme 8 - synthesis of SB(Cp, )HfCI ₂ Si-bridged pro-catalyst

Synthesis of SB(CpJ ^* )ZrCI(0-Mep-C _fi H ₃ )

[00122] Having regard to Scheme 9 below, SB(Cp,l ^* )ZrCI ₂ (100 mg, 0.207 mmol) and 2,6-dimethyl potassium phenoxide (66 mg, 0.414 mmol) were added to a Schlenk tube, dissolved in benzene (20 mL), and left to stir for sixteen hours. The solvent was removed in vacuo and the product extracted with pentane (2 x 20 mL). The ¹ H NMR spectra showed resonances corresponding to a mixture of two isomers. Thin, yellow crystals of isomer (a), suitable for single crystal X-ray diffraction were obtained when the solution was concentrated and stored in a -34 °C freezer. Purity was 94% by ¹ H NMR spectroscopy and crystals were obtained in 15% yield (16 mg, 0.028 mmol).

Isomer (a):

¹ H NMR (cfe-benzene): δ 7.06 (2H, dd, Ar _phe nH), 6.82 (1 H, t, Ar _phe nH), 6.26 (1 H, m, CpH), 6.13 (1 H, m, CpH), 5.93 (1 H, m, CpH), 5.61 (1 H, m, CpH), 2.34 (3H, s, ArMe), 2.24 (3H, s, ArMe), 2.22 (6H, s, Ar _phe nMe), 2.19 (3H, s ,ArMe), 2.18 (3H, s, ArMe), 2.15 (3H, s, ArMe), 1 .99 (3H, s, ArMe), 0.81 (3H, s, SiMe), 0.75 (3H, s, SiMe).

Isomer (b): ¹ H NMR (cfe-benzene): δ 6.88 (2H, dd, Ar _phe nH), 6.69 (1 H, t, Ar _phe nH), 6.51 (1 H, m, CpH), 6.02 (1 H, m, CpH), 5.88 (1 H, m, CpH), 5.80 (1 H, m, CpH), 2.61 (3H, s, ArMe), 2.42 (6H, s, ArphenMe), 2.40 (3H, s, ArMe), 2.08 (3H, s, ArMe), 1 .99 (3H, s, ArMe), 1 .64 (3H, s, ArMe), 1 .48 (3H, s, ArMe), 0.64 (3H, s, SiMe), 0.61 (3H, s, SiMe).

Scheme 9 - synthesis of SB(Cp,r)ZrCI(0-2,6-Me ₂ -C ₆ H ₃ ) Si-bridged pro-catalysts

Synthesis of Supported Catalyst Systems

Synthesis of solid MAO/[SB( ^tBu 2Flu,r)ZrCI _? l catalyst system

[00123] Toluene (40 ml) was added to a Schlenk tube containing solid aluminoxane (solid MAO) (produced by TOSOH, Lot no. TY130408) (400 mg) and [SB( ^tBu2 Ru,r)ZrCI ₂ ] (shown below) (13.6 mg) at room temperature. The slurry was heated to 60 °C and left, with occasional swirling, for one hour during which time the solution turned colourless and the solid colourised dark green. The resulting suspension was then left to cool down to room temperature and the toluene solvent was carefully filtered and removed in vacuo to obtain solid MAO/ [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ] catalyst as a grey, free-flowing powder in 85% yield (352 mg).

Synthesis of solid MAO/rac-[(EB )ZrCI ₂ l catalyst system (comparative example)

[00124] Toluene (40 ml) was added to a Schlenk tube containing solid MAO (produced by TOSOH; Lot no. TY1 30408) (400 mg) and rac-[(EBI ^* )ZrCI ₂ ] (shown below) (8.6 mg) at room temperature. The slurry was heated to 60 °C and left, with occasional swirling, for one hour during which time the solution turned colourless and the solid colourised dark green. The resulting suspension was then left to cool down to room temperature and the toluene solvent was carefully filtered and removed in vacuo to obtain solid MAO/ [SB( ^tBu 2Flu, )ZrCI ₂ ] catalyst as a grey, free-flowing powder in 85% yield (352 mg). Synthesis of solid MAO/meso-[(EBnZrClp1 catalyst system (comparative example)

[00125] Toluene (40 ml) was added to a Schlenk tube containing solid MAO (produced by TOSOH; Lot no. TY130408) (400 mg) and meso-[(EBI ^* )ZrCI ₂ ] (shown below) (8.6 mg) at room temperature. The slurry was heated to 60 °C and left, with occasional swirling, for one hour during which time the solution turned colourless and the solid colourised dark green. The resulting suspension was then left to cool down to room temperature and the toluene solvent was carefully filtered and removed in vacuo to obtain solid MAO/ [SB( ^tBU2 Flu,l ^* )ZrCl2] catalyst as a grey, free-flowing powder in 85% yield (352 mg).

Synthesis of solid MAO/rac-[(SBI ^* )ZrClp1 catalyst system (comparative example)

[00126] Toluene (40 ml) was added to a Schlenk tube containing solid MAO (produced by TOSOH; Lot no. TY1 30408) (400 mg) and rac-[(SBI ^* )ZrCI ₂ ] (shown below) (9.1 mg) at room temperature. The slurry was heated to 60 °C and left, with occasional swirling, for one hour during which time the solution turned colourless and the solid colourised dark green. The resulting suspension was then left to cool down to room temperature and the toluene solvent was carefully filtered and removed in vacuo to obtain solid MAO/ [SB( ^tBU2 Flu, )ZrCI ₂ ] catalyst as a grey, free-flowing powder in 85% yield (352 mg).

rac-[(EBI*) ₂ ZrCI ₂ ] meso-[(EBI*) ₂ ZrCI ₂ ] rac-[(SBI*) ₂ ZrCI ₂ ] SB( ^tBu2 Flu,l*)ZrCI ₂

Ethylene Polymerisation Studies

Homopolymerisation of ethylene

[00127] Solid MAO/[Zr-Complex] catalysts (Zr-Complex = rac-[(EBI ^* )ZrCI ₂ ], meso- [(EBI ^* )ZrCI ₂ ], rac-[(SBI ^* )ZrCI ₂ ], [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ]) were tested for their ethylene homopolymerisation activity under slurry conditions in the presence of tri(isobutyl)aluminium (TIBA), an aluminium-based scavenger. The reactions were performed under 2 bar of ethylene in a 200 mL ampoule, with 10 mg of the catalyst suspended in 50 mL of hexane. The reactions were run for 60 minutes controlled by heating in an oil bath. The resulting polyethylene was immediately filtered under vacuum through a dry sintered glass frit. The polyethylene product was then washed with pentane (2 χ 25 ml) and then dried on the frit for at least one hour. The tests were carried out at least twice for each individual set of polymerisation conditions.

[00128] Fig. 1 1 shows the polymerisation productivity (Kg(PE)g(Cat) ^~1 lr ¹ ) vs time (sec) for the polymerisation of ethylene using Solid MAO based catalysts at 70 °C. Fig. 12 shows the polymerisation productivity (Kg(PE)g(Cat) ^~1 h ^_1 ) vs time (sec) for the polymerisation of ethylene using Solid MAO based catalysts at 80 °C. The data demonstrate markedly superior activity for the solid MAO/[SB( ^tBu2 Flu, )ZrCI ₂ ] catalyst system of the invention, when compared with comparative examples solid MAO/rac-[(EB )ZrCI ₂ ], solid MAO/meso- [(EBI ^* )ZrCI ₂ ] and solid MAO/rac-[(SBI ^* )ZrCI ₂ ].

[00129] Table 1 below shows GPC results for the homopolymerisation of ethylene using Solid MAO/[complex] (complex = rac-[(EBI ^* )ZrCI ₂ ], meso-[(EBI ^* )ZrCI ₂ ], rac-[(SBI ^* )ZrCI ₂ ], [SB( ^tBu 2Flu,l ^* )ZrCI ₂ ]).

Table 1. GPC results for the homopolymerisation of ethylene using Solid MAO/ [complex].

Polymerisation conditions: 5 mL heptane, P _e th _y iene = 120 psi, and n _(T EA) = 10 μηιοΙ.

† Values underestimated due to incomplete sample elution. Note: maximum error is 10% on M,

[00130] Having regard to the data presented in Table 1 , unsymmetrical complex [SB( ^tBu 2Flu, )ZrCI ₂ ] is seen to afford polyethylene having a significantly higher molecular weight than that afforded by the comparator catalyst systems. Moreover, the increase in molecular weight is not accompanied by an increase in polydispersity. High molecular weight materials with low polydispersity are highly favoured by industry in special applications.

Copolymerisation of ethylene and 1 -hexene

[00131 ] Solid MAO/[Zr-Complex] catalysts (Zr-Complex = rac-[(EBI ^* )ZrCI ₂ ], meso- [(EBI ^* )ZrCI ₂ ], rac-[(SBI ^* )ZrCI ₂ ], [SB( ^tBu2 Flu,l ^* )ZrCI ₂ ]) were tested for their ethylene/1 -hexene copolymerisation activity under slurry conditions in the presence of tri(isobutyl)aluminium (TIBA), an aluminium-based scavenger. The reactions were performed under 2 bar of ethylene in a 200 mL ampoule, with 10 mg of the catalyst suspended in 50 mL of hexane. The reactions were run for 60 minutes controlled by heating in an oil bath. The resulting polyethylene was immediately filtered under vacuum through a dry sintered glass frit. The polyethylene product was then washed with pentane (2 χ 25 ml) and then dried on the frit for at least one hour. The tests were carried out at least twice for each individual set of polymerisation conditions.

[00132] Fig. 13 shows activity vs. time for the copolymerisation of ethylene and 1 -hexene using Solid MAO based catalyst. Fig. 14 shows activity vs time for the copolymerisation of ethylene and 1 -hexene using Solid MAO based catalyst with variation of the 1 -hexene feed, when Pethyiene = 120 PSI. Fig. 15 shows activity vs time for the copolymerisation of ethylene and 1 -hexene using Solid MAO based catalyst with variation of the 1 -hexene feed, when Pethyiene = 80 PSI. The data demonstrate superior copolymerisation activity for the solid MAO/[SB( ^tBu2 Flu, )ZrCI ₂ ] catalyst system of the invention, when compared with comparative examples solid MAO/rac-[(EBI ^* )ZrCI ₂ ], solid MAO/meso-[(EBI ^* )ZrCI ₂ ] and solid MAO/rac- [(SBI ^* )ZrCI ₂ ].

[00133] Table 2 below summarises activity results for the copolymerisation of ethylene and 1 -hexene using Solid MAO/ [complex].

Table 2 - Activity results for the copolymerisation of ethylene and 1 -hexene using Solid MAO/ [complex]. Polymerisation conditions: 5 mL heptane, 7=70 °C, P ethylene 120 psi, and n _(T EA) =

15 μηιοΙ.

[00134] The results presented in Table 2 demonstrate that the Solid MAO/ [SB( ^tBu 2Flu,l*)ZrCI ₂ ] catalytic complex of the invention exhibits markedly superior activity across a range of hexane concentrations, when compared with comparator catalytic complexes.

[00135] Tables 3 and 4 below shows GPC results for the copolymerisation of ethylene and 1 - hexene using Solid MAO/[complex] (complex = rac-[(EB )ZrCI ₂ ], meso-[{EB\ ^* )ZrC\ ₂ ], rac- [(SBI ^* )ZrCI ₂ ], [SB( ^tBu2 Flu,r)ZrCI ₂ ]).

Table 3 - GPC results for the copolymerisation of ethylene and 1 -hexene using Solid MAO/ [complex]. Polymerisation conditions: 5 mL heptane, 7=70 °C, P ethylene 120 psi, and n _(T EA) =

15 μηιοΙ.

†Values underestimated due to incomplete sample elution. Note: maximum error is 10% on M,

Table 4 - GPC results for the copolymerisation of ethylene and 1 -hexene using Solid MAO/ [complex]. Polymerisation conditions: 5 mL heptane, 7=70 °C, P ethylene 80 psi, and n _(T EA) =

15 μηιοΙ

[00136] Table 5 below illustrates the incorporation of 1 -hexene in the copolymerisation of ethylene and 1 -hexene by "Cf ¹ !!} NMR spectroscopy and crystallization elution fractionation analysis. Table 5 - ¹³ C{ ¹ H} NMR spectroscopy and CEF results of the incorporation of 1 -hexene in the copolymerisation of ethylene and 1 -hexene using Solid MAO/ [complex]. Polymerisation conditions: 5 mL heptane, 7=70 °C, P ethylene 120 psi, and n _(T EA) = 15 μηιοΙ.

[00137] The results outlined in Tables 3-5 point to a well-behaved copolymerization process with narrow inter-molecular co-monomer distribution, as analysed by GPC and CEF.

Further polymerisation studies

[00138] Table 6 below presents the activity results (kg _PE /gcAT/h) for the polymerisation of ethylene in slurry using SB(Cp, )ZrCI ₂ supported on Solid MAO. The activity of this complex is compared with that of ( ^nBu Cp) ₂ ZrCl2 and (lnd) ₂ ZrCl2, when supported on solid MAO, which are not encompassed by the invention.

Table 6. Activity results (kg _PE /gcAT/h) for the polymerisation of ethylene in slurry, complex supported on Solid MAO

[00139] Table 7 below presents the activity results (kg _PE /gcAT/h) and molecular weight (g/mol) for the polymerisation of ethylene in slurry using supported on Solid MAO/ SB(Cp,l ^* )ZrCI ₂ as a function of H ₂ feeding content. Table 7. Activity results (kg _PE /gcAT/h) and molecular weight (g/mol) for the polymerisation of ethylene in slurry using supported on Solid MAO/ SB(Cp, )ZrCI ₂ as a function of H ₂ feeding content.

[00140] Table 8 below presents the activity results (kg _PE /gcAT/h/bar), molecular weight (g/mol) and CEF value for the polymerisation of ethylene and co-polymerisation of ethylene and 1 -hexene in slurry using various compositions of the invention (supported on Solid MAO).

Table 8. Activity results (kg _PE /gcAT/h/bar), molecular weight (g/mol) and CEF value for the polymerisation of ethylene and co-polymerisation of ethylene and 1 -hexene in slurry using complexes supported on Solid MAO.

Polymerisation conditions: 80 °C, 8 bar, 5 mL Heptane

[00141 ] Figs. 28 and 29 demonstrate that the solid MAO supported SB( ^tBu2 Flu,l ^* )ZrCI ₂ and solid MAO supported SB(Cp,l ^* )ZrCI ₂ catalysts possess the highest activities. Changing the bridge to di-ethyl and methyl-propyl led to similar activities.

[00142] Fig. 30 shows that solid MAO supported SB( ^tBu2 Flu,l ^* )HfCI ₂ is 3 times faster than solid MAO supported SB(Cp,l ^* )HfCI ₂ but 25 % slower than its zirconium analogue (Fig. 26). [00143] Fig. 31 shows that good polyethylene morphology were obtained when solid MAO supported/ ^Et2 SB( ^tBu2 Flu,r)ZrCI ₂ and solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ were used as catalysts, which demonstrates monodisperse PE.

[00144] Fig. 32 shows that in similar conditions solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ is better controlled and affords a higher activity (3.2 kg _PE /gcAT/h/bar) than known industrial catalysts (solid MAO supported ( ^nBu Cp) ₂ ZrCl2 and solid supported (lnd) ₂ ZrCI ₂ with activities of 1 .2 and 1 .6 kg _PE /gcAT/h/bar respectively). This demonstrates the huge potential for solid MAO supported/ SB(Cp,l ^* )ZrCI ₂ to be used as catalyst for the formation of PE wax.

[00145] Figs. 33 and 34 show the decrease in activity and in molecular weight with increasing H ₂ content when used as co-feed.

[00146] Fig. 35 shows that most of the catalysts afforded a higher activity for the copolymerisation of ethylene and 1 -hexene than the just for the homopolymerisation of ethylene.

Synthesis of solid MAO

[00147] Various samples of solid MAO were prepared according to the below synthetic protocol:

Benzoic ad

AIMe ₃ ne MAO Solid MAO

r

[00148] The effect of varying Al:0 ratio on the BET surface area and ethylene polymerisation activity was investigated. The results are presented in Table 9 below:

Table 9. Effect of varying Al:0 ratio on the BET surface area and ethylene polymerisation activity of Me ₂ SB( ^tBu2 Flu, l ^* )ZrCI ₂ supported on solid MAO

TMA amount kept constant. Benzoic acid content varied.

[00149] While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.

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