METALLOCENE CATALYSTS COMPRISING MONOCYCLIC SILOXY SUBSTITUTED CYCLOPENTADIENYL GROUP(S) FOR THE POLYMERISATION OF OLEFINS

Abstract: The invention provides a metallocene procatalyst compound comprising a group 3 to 7 transition metal eta -liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group. Such compounds may be used together with a cocatalyst, e.g. an alumoxane, for olefin polymerization.

Description: METALLOCENE CATALYSTS COMPRISING MONOCYCLIC SILOXY SUBSTITUTED CYCLOPENTADIENYL GRUOUP(S) FOR THE POLYMERISATION OF OLEFINS This invention relates to catalysts for olefin 5 polymerisation, in particular to catalyst compounds containing metals η-bonded by siloxycyclopentadienyl ligands, and their use in olefin polymerisation. In olefin polymerization, it has long been known to use as a catalyst system the combination of a 10 metallocene procatalyst and an alumoxane co-catalyst. By "metallocene" is here meant an η-ligand metal complex, e.g. an "open sandwich" or "half sandwich" compound in which the metal is complexed by a single η- ligand, a "sandwich" compound in which the metal is 15 complexed by two or more η-ligands, a "handcuff" compound" in which the metal is complexed by a bridged bis-η-ligand or a "scorpionate" compound in which the metal is complexed by an η-ligand linked by a bridge to a σ-ligand. 20 Alumoxanes are compounds with alternating aluminium and oxygen atoms generally compounds of formula I or II R 2 A1- (0-Al ) p -0-AlR 2 (I) (II) where each R, which may be the same or different, is a i-i o alkyl group, and p is an integer having a value between 0 and 40) . These compounds may be prepared by 30 reaction of an aluminium alkyl with water. The production and use of alumoxanes is described in the patent literature, especially the patent applications of Texas Alkyls, Albemarle, Ethyl, Phillips, Akzo Nobel, Exxon, Idemitsu Kosan, Witco, BASF and Mitsui. - - 35 Traditionally, the most widely used alumoxane is methylalumoxane (MAO) , an alumoxane compound in which the R groups are methyls. MAO however is poorly 2characterised and relatively expensive and efforts have been made to use alumoxanes other than MAO. Thus, for example 098/32775 (Borealis) proposes the use of metallocene procatalysts with alumoxanes in which R is a C 2 _ 10 alkyl group, eg hexaisobutylalumoxane (HIBAO) . However, such metallocenes generally have poor catalyst activities with non-MAO alumoxanes. We have now surprisingly found that metallocenes in which the metal is η-liganded by a siloxy-, homo or heterocyclic cyclopentadienyl group, i.e. a cyclic η 5 -ligand substituted by a siloxy group but not carrying a fused ring, have surprisingly high activity with non- MAO alumoxanes . Thus viewed from one aspect the invention provides a metallocene procatalyst compound comprising a group 3 to 7 transition metal η-liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group . By group 3 (etc) metal is meant a metal in group 3 of the Periodic Table of the Elements, namely Sc, Y, etc . Viewed from a further aspect the invention provides an olefin polymerisation catalyst system comprising or produced by reaction of (i) a metallocene procatalyst compound comprising a group 3 to 7 transition metal η- liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group and (ii) a co- catalyst, eg an aluminium alkyl compound, in particular an alumoxane, especially an aluminium alkyl compound comprising alkyl groups containing at least two carbon atoms . Viewed from a still further aspect the invention provides a process for olefin polymerisation comprising polymerising an olefin in the presence of a metallocene compound comprising a group 3 to 7 transition metal η- liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group. Viewed from a yet further aspect the invention provides a process for the preparation of a metallocene procatalyst, said process comprising metallating with a group 3 to 7 transition metal a ligand comprising a siloxy-substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group. Viewed from a further aspect the invention provides the use of a metallocene compound comprising a group 3 to 7 transition metal η-liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group in olefin polymerization, especially ethylene or propylene, more especially ethylene, polymerisation or copolymerisation. Viewed from a yet further aspect the invention provides an olefin polymer produced by a polymerisation catalysed by a metallocene compound comprising a group 3 to 7 transition metal η-liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group. By "monocyclic" it is meant that the η 5 ring of the cyclopentadienyl group is not fused to another ring, ie it cannot be a part of an indenyl or fluorenyl multi- ring structure. The η 5 ring however may be substituted by cyclic groups or cyclic group containing substituents and the metal may be liganded by other η-ligands which are acyclic or multicyclic. The η 5 -ligand with which the group 3 to 7 metal is complexed typically is a compound of formula IV where X, Y and T are ring carbons or ring heteroatoms (e.g. N, B or P atoms) , preferably two or three of X, Y and T being ring carbons; each R', which may be the same or different is a R + , OR + , SR + , NR + 2 or PR + 2 group where each R + is a C λ . 16 hydrocarbyl group, a group or a tri-C 1 _ 8 hydrocarbylsiloxy group, preferably R' being a C^ 12 hydrocarbyl group, eg a C τ _ 8 alkyl or alkenyl group; each R", which may be the same or different is a ring substituent which does not form a bond to a metal η-bonded by the C 2 XYT ring and is other than a ring fused to the C 2 XYT ring, eg it may be a R + , OR + , SR + , NR + 2 or PR + 2 group where each R + is a C x _ 16 nydrocarbyl group, a hydrocarbylsilyl group or a group; n is zero or a positive integer, eg having a value of 1, 2, 3 or 4, n preferably being non-zero; m is zero or 1, at least one of n and m preferably being non zero; and R"' is an η-ligand linked to the C 2 XYT ring by a 1 to 3 atom bridge, and optionally substituted, eg by R" groups . Besides the η-ligand of formula IV, the group 3 to 7 transition metal may be η-liganded by one or two further η ligands. These may be cyclic or acyclic and may carry cyclic groups fused to an η 5 or η 4 cyclic or acyclic structure and may be bridged bis-η ("handcuff") ligands or bridged η-σ ("scorpion") ligands. Thus for example such an η 5 or η 4 ligand group may be a homo- or heterocyclic cyclopentadienyl, indenyl or fluorenyl group, or an acyclic η 5 C 5 , η 5 -C 3 N 2 or η 4 C 2 N 2 group optionally carrying cyclic groups fused to the η 5 or η 4 skeleton. Such further η ligands may optionally be substituted, eg by groups R" . Particular examples of such further η-ligands include cyclopentadienyl, indenyl and fluorenyl ligands, especially siloxy substituted (eg ' 3 SiO-substituted) cyclopentadienyl or indenyl ligands. Examples of such further η-ligands abound in the patent literature relating to metallocene and pseudo metallocene olefin polymerization (pro) catalysts, in particular that deriving from Exxon, Hoechst, Phillips, Dow, Chisso, Mitsui, Fina, BASF, Mitsubishi, Mobil, Targor, DSM and Borealis, eg WO96/23010, WO98/49208, W099/12981, W099/19335, WO97/28170 , EP-A-423101, EP-A- 537130, etc. as well as "Metallocenes" Vol. 1, Togni and Halterman (Eds.) Wiley-VCH, 1998. Besides η-ligands, the group 3 to 7 metal in the procatalyst of the invention may be coordinated by hydrogen atoms, hydrocarbyl σ-ligands (eg optionally substituted C 1 _ 12 hydrocarbyl groups, such as C 1 _ 12 alkyl, alkenyl or alkynyl groups optionally substituted by fluorine and/or aryl (eg phenyl) groups) , by silane groups (eg Si(CH 3 ) 3 ), by halogen atoms (eg chlorine), by C ± . B hydrocarbylheteroatom groups, by tri-C^ 8 hydrocarbylsilyl groups, by bridged bis-σ-liganding groups, by amine (eg N(CH 3 ) 2 ) or imine (eg N=C or N=P groups, eg R 3 P=N- wherein each R can be independently the same or different, aliphatic or aromatic hydrocarbyl with 1 to 12 C atoms, or by other σ-ligands known for use in metallocene (pro) catalysts . By a σ-ligand moiety is meant a group bonded to the metal at one or more places via a single atom, eg a hydrogen, halogen, silicon, carbon, oxygen, sulphur or nitrogen atom. Thus for example the metallocene pro catalyst of the invention may conveniently be a compound of formula V where X, Y, T, R', R", R"', n and m are as defined above; q is 1, 2 or 3, generally being 1 when m is 1; M is a group 3 to 7 transition metal L is a further η-ligand (eg as discussed above) ; r is zero, 1 or 2 ; Z is a σ-ligand (eg as discussed above) ; and s is zero or a positive integer having a value of up to 3 depending on the values of m, q and r and the oxidation state of metal M. The metal M in the metallocene procatalysts of the invention is a group 3 to 7 transition metal, preferably a group 4 to 6 transition metal, eg a metal selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W. However the metal is preferably Cr, Ti, Zr or Hf, particularly Cr if M is η-liganded by a single η-ligand group or Ti, Zr or Hf if M is η-liganded by one or more η-ligand groups In the metallocene procatalysts of the invention, the siloxycyclopentadienyl η-ligand is especially preferably a ligand of formula VI where R' is as defined above; Y' is P, B, CH or C-CH 3 ; R* is H or CH 3 ; and R"" is H, CH 3 or Bg-ETA where Bg is a one or two atom bridge (particularly a (CH 2 ) 2 or Si(CH 3 ) 2 bridge) and ETA is a cyclopentadienyl, indenyl, tetrahydroindenyl , fluorenyl , tetrahydrofluorenyl or octahydrofluorenyl or other closed ring η-ligand group. In the compounds of formula VI, the ETA ligand may be substituted or unsubstituted and the η 5 ring may be the homo or heterocyclic, eg incorporating P, B or N ring heteroatoms . Examples of suitable R' 3 SiO groups in the metallocene procatalysts of the invention include Thus typical examples of ligands of formula IV include Typical examples of the metallocene procatalysts of the invention thus include: where each R'*, which may be the same or different, is an up to C 12 hydrocarbyl, e.g. a aromatic or aliphatic hydrocarbyl; each R** which may be the same or different, is H or CH 3 ; each X is CH, CCH 3 , P or B; each Y is CH if X is P or B or is CR** if X is CH or CCH 3 ; and R' is as hereinbefore defined. Examples of particular siloxy-η-ligands usable according to the invention include: triisopropylsiloxycyclopentadieny] . 1-triisopropylsiloxy-3-methyl-cyclopentadienyl, l-triisopropylsiloxy-3, 4-dimethyl-cyclopentadienyl, l-triisopropylsiloxy-2, 3 , 4-trimethyl-cyclopentadienyl , (dimethyltertbutylsiloxy) -cyclopentadienyl, 1- (dimethyltertbutylsiloxy) -3-methylycyclopentadienyl , 1- (dimethyltertbutylsiloxy) - 3,4- dimethylcyclopentadienyl , 1- (dimethyltertbutylsiloxy) -2 , 3 , 4-trimethyl- cyclopentadienyl, l-triisopropylsiloxy-2-phospholyl, l-triisopropylsiloxy-3 -phospholyl, l-dimethyltertbutylsiloxy-2 -phospholyl, l-dimethyltertbutylsiloxy-3 -phospholyl, l-triisopropylsiloxy-2 -borolyl, l-triisopropylsiloxy-3 -borolyl, l-dimethyltertbutylsiloxy-2 -borolyl, l-dimethyltertbutylsiloxy-3 -borolyl, 1- (dimethyloct-l-en-8-ylsiloxy) -3 -methyl- cyclopentadienyl, 1- (dimethyloct-l-en-8-ylsiloxy) -3 , 4 -dimethyl- cyclopentadienyl , ethylene-bis- (2-triisopropylsiloxy-cyclopentadienyl) , ethylene-bis (2- (dimethyltertbutylsiloxy) - cyclopentadienyl) , dimethylsilylbis- (2-triisopropylsiloxy- cyclopentadienyl) , dimethylsilylbis- (2 - (dimethyltertbutylsiloxy) - cyclopentadien- 1 -yl ) , dimethylsilyl -bis - (2 -dimethyltertbutylsiloxy- 4 , 5 - dimethylcyclopentadienyl ) , dimethylsilyl (2 - (dimethyltertbutylsiloxy) - cyclopentadienyl ) (3 - (dimethyltertbutylsiloxy) -phosphol - 4 -yl , dimethylsilyl (2- (dimethyltertbutylsiloxy) - cyclopentadienyl) (3- (dimethyltertbutylsiloxy) -borol-4- yl), dimethylsilyl (2- triisopropylsiloxycyclopentadienyl) (indenyl) , and dimethylsilyl (2- triisopropylsiloxycyclopentadienyl) (fluorenyl) . Examples of particular further η-ligands are well known from the technical and patent literature relating to metallocene olefin polymerization catalysts, e.g. EP-A- 35242 (BASF) , EP-A-129368 (Exxon) , EP-A-206794 (Exxon) , PCT/FI97/00049 (Borealis), EP-A-318048, EP-A-643084, EP- A-69951, EP-A-410734, EP-A-128045, EP-B-35242 (BASF) , EP-B-129368 (Exxon) and EP-B-206724 (Exxon) . These include cyclopentadienyl, indenyl , fluorenyl , octahydrofluorenyl , methylcyclopentadienyl , 1, 2-dimethylcyclopentadienyl, penta ethylcyclopentadienyl , pentyl-cyclopentadienyl, 2 -dimethyl, tertbutylsiloxy-inden-1-yl, n-butylcyclopentadienyl , 1, 3 -dimethylcyclopentadienyl, 4, 7-dimethylindenyl, 1 , -ethyl-2-methylcyclopentadienyl , tetrahydroindenyl , and methoxycyclopentadienyl . Examples of σ-ligands include: halogenides (e.g. chloride and fluoride), hydrogen, triC 1 _ 12 hydrocarbyl-silyl or -siloxy (e.g. trimethylsilyl) , triC. 6 hydrocarbylphosphimido (e.g. triisopropylphosphimido) , c ι-ι 2 hydrocarbyl or hydrocarbyloxy (e.g. methyl, ethyl, phenyl , benzyl and methoxy) , diCi.g hydrocarbylamido (e.g. dimethylamido and diethylamido) , and 5 to 7 ring membered heterocyclyl (eg pyrrolyl, furanyl and pyrrolidinyl) . The siloxy cyclopentadienyl η-ligands used according to the invention may be prepared by reaction of a corresponding siloxycyclopentadiene with an appropriate base, e.g. an organolithium compound, such as methyllithium or butyllithium. Particular bases of use in this regard include t-BuLi, n-BuLi, lithium diisopropylamide, t-BuOK, trialkylamines, dialkyl- magnesium, alkylmagnesium chloride, alkyl CuLi and dialkyl zinc which may be used in conjunction with a suitable solvent. If necessary, a donor such as dimethoxyethane may be added to the reaction medium containing the siloxycyclopentadiene prior to addition of the base. The ligand can be metallated conventionally, eg by reaction with a halide of the metal M, preferably in an organic solvent, eg a hydrocarbon or a hydrocarbon/ether mixture. Bridged siloxy-cyclopentadienyl ligands may be constructed by reacting a siloxy-monocyclopentadienyl ligand with a bridging agent (eg Si(CH 3 ) 2 Cl 2 ) or with a bridging agent and a further η-ligand (eg a different cyclopentadienyl ligand or with an indenyl, fluorenyl, etc ligand) . An alternative approach to the complexes is also envisaged where the siloxycyclopentadiene is reacted with Zr(NMe 2 ) 4 or Zr(CH 2 Ph) 4 followed by Me 3 SiCl to yield the complex directly. Also, trimethylsilyl (siloxy) cyclopentadiene reacts with ZrCl 4 to afford the complex directly. σ-ligands other than chlorine may be introduced by displacement of chlorine from an η-ligand metal chloride by reaction with appropriate nucleophilic reagent (e.g. methyl lithium or methylmagnesium chloride) or using, instead of a metal halide, a reagent such as tetrakisdimethylamidotitanium or metal compounds with mixed chloro and dimethylamido ligands. As mentioned above, the olefin polymerisation catalyst system of the invention comprises (i) a siloxycyclopentadienyl metallocene and (ii) an aluminium alkyl compound, or the reaction product thereof. While the aluminium alkyl compound may be an aluminium trialkyl (eg triethylaluminium (TEA) ) or an aluminium dialkyl halide (eg diethyl aluminium chloride (DEAC) ) , it is preferably an alumoxane, particularly an alumoxane other than MAO, most preferably an isobutylalumoxane, eg TIBAO (tetraisobutylalumoxane) or HIBAO (hexaisobutylalumoxane) . Alternatively however the alkylated (eg methylated) metallocene procatalysts of the invention (e.g. compounds of formula V wherein Z is alkyl ) may be used with other cocatalysts , eg boron compounds such as B (C 6 F 5 ) 3 , C 6 H 5 N (CH 3 ) 2 H : B (C 6 F 5 ) 4 , (C 6 H 5 ) 3 C : B (C 6 F 5 ) 4 or Ni (CN) 4 [B (C 6 F 5 ) 3 ] 4 2 - . The metallocene procatalyst and cocatalyst may be introduced into the polymerization reactor separately or together or, more preferably they are pre-reacted and their reaction product is introduced into the polymerization reactor. If desired the procatalyst, procatalyst/cocatalyst mixture or a procatalyst/cocatalyst reaction product may be used in unsupported form, i.e. metallocene and MAO can be precipitated without an actual carrier material and used as such. However the metallocene procatalyst or its reaction product with the cocatalyst is preferably introduced into the polymerization reactor in supported form, eg impregnated into a porous particulate support . The particulate support material used is preferably an organic or inorganic material, e.g. a polymer (such as for example polyethylene, polypropylene, an ethylene- propylene copolymer, another polyolefin or polystyrene or a combination thereof) . Such polymeric supports may be formed by precipitating a polymer or by a prepolymerization, eg of monomers used in the polymerization for which the catalyst is intended. However, the support is especially preferably a metal or pseudo metal oxide such as silica, alumina or zirconia or a mixed oxide such as silica-alumina, in particular silica, alumina or silica-alumina. Particularly preferably, the support material is acidic, e.g. having an acidity greater than or equal to silica, more preferably greater than or equal to silica-alumina and even more preferably greater than or equal to alumina. The acidity of the support material can be studied and compared using the TPD (temperature programmed desorption of gas) method. Generally the gas used will be ammonia. The more acidic the support, the higher will be its capacity to adsorb ammonia gas. After being saturated with ammonia, the sample of support material is heated in a controlled fashion and the quantity of ammonia desorbed is measured as a function of temperature . Especially preferably the support is a porous material so that the metallocene may be loaded into the pores of the support, e.g. using a process analogous to those described in W094/14856 (Mobil) , W095/12622 (Borealis) and WO96/00243 (Exxon) . The particle size is not critical but is preferably in the range 5 to 200 μm, more preferably 20 to 80 μm. Before loading, the particulate support material is preferably calcined, ie heat treated, preferably under a non-reactive gas such as nitrogen. This treatment is preferably at a temperature in excess of 100°C, more preferably 200°C or higher, e.g. 200-800°C, particularly about 300°C. The calcination treatment is preferably effected for several hours, e.g. 2 to 30 hours, more preferably about 10 hours. The support may be treated with an alkylating agent before being loaded with the metallocene. Treatment with the alkylating agent may be effected using an alkylating agent in a gas or liquid phase, e.g. in an organic solvent for the alkylating agent. The alkylating agent may be any agent capable of introducing alkyl groups, preferably C x _ 6 alkyl groups and most especially preferably methyl groups. Such agents are well known in the field of synthetic organic chemistry. Preferably the alkylating agent is an organometallic compound, especially an organoaluminium compound (such as trimethylaluminium (TMA) , dimethyl aluminium chloride, triethylaluminium) or a compound such as methyl lithium, dimethyl magnesium, triethylboron, etc. The quantity of alkylating agent used will depend upon the number of active sites on the surface of the carrier. Thus for example, for a silica support, surface hydroxyls are capable of reacting with the alkylating agent. In general, an excess of alkylating agent is preferably used with any unreacted alkylating agent subsequently being washed away. Where an organoaluminium alkylating agent is used, this is preferably used in a quantity sufficient to provide a loading of at least 0.1 mmol Al/g carrier, especially at least 0.5 mmol Al/g, more especially at least 0.7 mmol Al/g, more preferably at least 1.4 mmol Al/g carrier, and still more preferably 2 to 3 mmol Al/g carrier. Where the surface area of the carrier is particularly high, lower aluminium loadings may be used. Thus for example particularly preferred aluminium loadings with a surface area of 300-400 m 2 /g carrier may range from 0.5 to 3 mmol Al/g carrier while at surface areas of 700-800 m 2 /g carrier the particularly preferred range will be lower. Following treatment of the si^port material with the alkylating agent, the support is preferably removed from the treatment fluid and any excess treatment fluid is allowed to drain off. The optionally alkylated support material is loaded with the procatalyst, preferably using a solution of the procatalyst in an organic solvent therefor, e.g. as described in the patent publications referred to above. Preferably, the volume of procatalyst solution used is from 50 to 500% of the pore volume of the carrier, more especially preferably 80 to 120%. The concentration of procatalyst compound in the solution used can vary from dilute to saturated depending on the amount of metallocene active sites that it is desired be loaded into the carrier pores . The active metal (ie. the metal of the procatalyst) is preferably loaded onto the support material at from 0.1 to 4%, preferably 0.5 to 3.0%, especially 1.0 to 2.0%, by weight metal relative to the dry weight of the support material . After loading of the procatalyst onto the support material, the loaded support may be recovered for use in olefin polymerization, e.g. by separation of any excess procatalyst solution and if desired drying of the loaded support, optionally at elevated temperatures, e.g. 25 to 80°C. Alternatively, a cocatalyst, e.g. an alumoxane or an ionic catalyst activator (such as a boron or aluminium compound, especially a fluoroborate) may also be mixed with or loaded onto the catalyst support material . This may be done subsequently or more preferably simultaneously to loading of the procatalyst, for example by including the cocatalyst in the solution of the procatalyst or, by contacting the procatalyst loaded support material with a solution of the cocatalyst or catalyst activator, e.g. a solution in an organic solvent . Alternatively however any such further material may be added to the procatalyst loaded support material in the polymerization reactor or shortly before dosing of the catalyst material into the reactor. In this regard, as an alternative to an alumoxane it may be preferred to use a fluoroborate catalyst activator, especially a B(C 6 F 5 ) 3 or more especially a Θ B(C 6 F 5 ) 4 compound, such as C 6 H 5 N(CH 3 ) 2 H:B (C 6 F 5 ) 4 or (C 5 H 5 ) 3 C:B (C 6 F 5 ) 4 . Other borates of general formula (cation) a (borate) b where a and b are positive numbers, may also be used. Where such a cocatalyst or catalyst activator is used, it is preferably used in a iuole ratio to the metallocene of from 0.1:1 to 10000:1, especially 1:1 to 50:1, particularly 1:2 to 30:1. More particularly, where an alumoxane cocatalyst is used, then for an unsupported catalyst the aluminium:metallocene metal (M) molar ratio is conveniently 2:1 to 10000:1, preferably 50:1 to 1000:1. Where the catalyst is supported the Al :M molar ratio is conveniently 2:1 to 10000:1 preferably 50:1 to 400:1. Where a borane cocatalyst (catalyst activator) is used, the B:M molar ratio is conveniently 2:1 to 1:2, preferably 9:10 to 10:9, especially 1:1. When a neutral triarylboron type cocatalyst is used the B:M molar ratio is typically 1:2 to 500:1, however some aluminium alkyl would normally also be used. When using ionic tetraaryl borate compounds, it is preferred to use carbonium rather than ammonium counterions or to use B:M molar ratio 1:1. Where the further material is loaded onto the procatalyst loaded support material, the support may be recovered and if desired dried before use in olefin polymerization. The olefin polymerized in the method of the invention is preferably ethylene or an alpha-olefin or a mixture of ethylene and an α-olefin or a mixture of alpha olefins, for example C 2 _ 20 olefins, e.g. ethylene, propene, n-but-1-ene, n-hex-1-ene, 4-methyl -pent-1-ene, n-oct-1-ene- etc. The olefins polymerized in the method of the invention may include any compound which includes unsaturated polymerizable groups. Thus for example unsaturated compounds, such as C 6 _ 20 olefins (including cyclic and polycyclic olefins (e.g. norbornene) ) , and polyenes, especially C 6 _ 20 dienes, may be included in a comonomer mixture with lower olefins, e.g. C 2 _ 5 α- olefins . Diolefins (ie. dienes) are suitably used for introducing long chain branching into the resultant polymer. Examples of such dienes include α,ω linear dienes such as 1, 5-hexadiene, 1, 6-rιeptadiene, 1,8- nonadiene, 1, 9-decadiene, etc. In general, where the polymer being produced is a homopolymer it will preferably be polyethylene or polypropylene. Where the polymer being produced is a copolymer it will likewise preferably be an ethylene or propylene copolymer with ethylene or propylene making up the major proportion (by number and more preferably by weight) of the monomer residues. Comonomers, such as C 4 _ 6 alkenes, will generally be incorporated to contribute to the mechanical strength of the polymer product. Usually metallocene catalysts yield relatively narrow molecular weight distribution polymers; however, if desired, the nature of the monomer/monomer mixture and the polymerization conditions may be changed during the polymerization process so as to produce a broad bimodal or multimodal molecular weight distribution (MWD) in the final polymer product. In such a broad MWD product, the higher molecular weight component contributes to the strength of the end product while the lower molecular weight component contributes to the processability of the product, e.g. enabling the product to be used in extrusion and blow moulding processes, for example for the preparation of tubes, pipes, containers, etc. A multimodal MWD can be produced using a catalyst material with two or more different types of active polymerization sites, e.g. with one such site provided by the metallocene on the support and further sites being provided by further catalysts, e.g. Ziegler catalysts, other metallocenes, etc. included in the catalyst material . Polymerization in the method of the invention may be effected in one or more, e.g. 1, 2 or 3, polymerization reactors, using conventional polymerization techniques, e.g. gas phase, solution phase, slurry or bulk polymerization. In general, a combination of slurry (or bulk) and at least one gas phase reactor is often preferred, particularly with the reactor order being slurry (or bulk) then one or more gas phase . For slurry reactors, the reaction temperature will generally be in the range 60 to 110°C (e.g. 85-110°C) , the reactor pressure will generally be in the range 5 to 80 bar (e.g. 50-65 bar), and the residence time will generally be in the range 0.3 to 5 hours (e.g. 0.5 to 2 hours) . The diluent used will generally be an aliphatic hydrocarbon having a boiling point in the range -70 to +100°C. In such reactors, polymerization may if desired be effected under supercritical conditions. For gas phase reactors, the reaction temperature used will generally be in the range 60 to 115°C (e.g. 70 to 110°C) , the reactor pressure will generally be in the range 10 to 25 bar, and the residence time will generally be 1 to 8 hours. The gas used will commonly be a non-reactive gas such as nitrogen together with monomer (e.g. ethylene). For solution phase reactors, the reaction temperature used will generally be in the range 130 to 270°C, the reactor pressure will generally be in the range 20 to 400 bar and the residence time will generally be in the range 0.005 to 1 hour. The solvent used will commonly be a hydrocarbon with a boiling point in the range 80-200°C. Generally the quantity of catalyst used will depend upon the nature of the catalyst, the reactor types and conditions and the properties desired for the polymer product. Conventional catalyst quantities, such as described in the publications referred to herein, may be used. All publications referred to herein are hereby incorporated by reference . The invention will now be illustrated further by reference to the following non-limiting Examples and to the accompanying drawings in which: Figure 1 is a plot of catalyst activity for homopolymerisation of polyethylene using the procatalysts of Examples 3 to 5 and MAO or HIBAO. Ligand and complex synthesis All operations are carried out in an argon or nitrogen atmosphere using standard Schlenk, vacuum and drybox techniques. Ether, tetrahydrofuran (THF) and toluene solvents were dried with potassium benzophenone ketyl and distilled under argon prior to use. Other solvents were dried using " 13X+13A molecular sieves. All other chemicals were used as commercially available. NMR spectra were recorded using a JEOL JNM-EX270 MHz FT-NMR spectrometer with trimethylsilane (TMS) as an internal reference . Direct inlet mass spectra were recorded using a VG TRIO 2 quadruple mass spectrometer in electron impact ionization mode. (70eV) . GC-MS analysis was performed using a Hewlett Packard 6890/5973 Mass Selective Detector in electron impact ionization mode (70eV) , equipped with a silica capillary column (30m x 0.25 mm i.d) . Ligands and unbridged complexes were prepared using one of the following reaction schemes : The cyclopentanones required for step 2 were prepared using a procedure (step 1) described in Bull. Soc. Chim. Fr. 2981-2991 (1970) . The siloxylation of step 2 followed the description in Organometallics 15_:5066-5086 (1996). Ligand activation and complexation were carried out using standard known procedures . Polymerization Reactions (i) Ethylene homopolymerization in slurry with unsupported catalyst Polymer was produced by ethylene homopoly erisation in a Bύchi 2L stirred autoclave reactor 1200 ml of n- pentane was added to the reactor whereafter procatalyst and cocatalyst in solution in toluene were added to the reactor. MAO (30wt% in toluene) and HIBAO (70 wt% in toluene) , both from Albermarle were used in this regard. The temperature was raised to 80°C and continuous ethylene feed was begun. The temperature was maintained at 80 °C and ethylene pressure was maintained at 10 bar for 30 minutes after which the reaction was terminated by stopping ethylene flow to the reactor and releasing the reactor overpressure. (ii) Ethylene homopolymerization with hydrogen Polymer was prepared as in (i) above except that hydrogen (0.5 bar) was introduced from a 677 mL container together with the ethylene. (iii) Ethylene homopolymerization using a supported catalyst Polymer was prepared as in (i) above except that isobutane was used as the polymerisation medium and the catalyst was added as a dried powder prepared by adding a toluene solution of procatalyst and cocatalyst to silica (Sylopol 55SJ from Grace, activated at 600°C) , stirring for 30 minutes and drying under nitrogen flow. (iv) Ethylene/hexene copolymerisation with unsupported catalyst Polymer was produced as in (i) above but with 30ml of hex-1-ene being added to the reactor before the ethylene. (v) Ethylene/hexene copolymerization with hydrogen Polymer was produced as in (iv) above except that hydrogen (0.3 bar (v. a.) or 0.5 bar (v.b) ) was introduced from a 677 mL container together with the ethylene . (vi) Ethylene/hexene copolymerisation using a supported catalyst Polymer was produced as (iii) above but with 30ml of hex-1-ene being added to the reactor before the ethylene . (vii) Propylene homopolymerization using a supported catalyst MAO (30wt% in toluene from Albemarle) and procatalyst were mixed inside a glove box to give an Al:M molar ratio of 550. To 0.65ml of this solution was added 0.5g silica (2104 from Grace, activated at 600°C) and the two were mixed for about 10 minutes, then dried at ambient temperature by nitrogen flushing. About 100 mg of supported catalyst was added as a dry powder to a 2L reactor equipped with a stirrer. Propylene (650ml at 15°C) was added and the stirrer was activated. After 8 minutes of polymerisation the temperature was raised to 70°C over 2 minutes and maintained there for about 60 minutes . Polymerisation was terminated by depressurizing the reactor and the polymer powder was vacuum dried. (viii) Propylene homopolymerisation using unsupported catalyst MAO (3ml 30wt% in toluene from Albemarle) and 0.5 ml of the MAO/metallocene solution prepared in (vii) above was mixed in a syringe and added to a 2L reactor equipped with a stirrer. Polymerisation was then effected as in (viii) above. Elemental Analysis Elemental analyses for carbon, hydrogen and nitrogen were carried out simultaneously with a CHNO- RAPID Analyzer from Elementar Analysensysteme GmbH working in principle as in Method C of ASTM 5291-92. The substance is combusted under an oxygen amosphere at 950°C. The combustion product gas stream, after full oxidation of the component gases, is passed with helium as carrier gas over heated copper to remove excess oxygen and reduce nitrogen oxides to N 2 gas . The gases are then passed through a heatable chromatographic column to separate and elute N 2 , C0 2 , and H 2 0, in that order. The individual eluted gases are measured by a thermal conductivity detector. Chlorine determinations were performed by the oxygen flask method (e.g. DIN 53474). In this method the substance is wrapped in a piece of ash-free filter paper and burned in an oxygen filled flask, containing diluted sodium hydroxide solution as absorbent. Chlorine is then measured electrometrically by titration with standard AgN0 3 in the acidified solution. When handling air sensitive compounds, they are weighed under inert atmosphere in small gelatine capsules . Aluminum, chromium, and titanium were determined after destroying the organic matter by wet oxidation using sulfuric and nitric acid. Aluminum and chromium are measured by atomic absorption and titanium photometrically by means of the peroxodisulfatotitanic acid complex. Silicon analysis was done by atomic absorption from an alkaline solution after fusing the substance with sodium peroxide. Zirconium analysis was by ignition of the sample and weighing the oxide formed. Example 1 Bis (trimethylsiloxycyclopentadienyl) zirconium dichloride 9.1 g (111.0 mmol) of cyclopent-2-en-l-one (Fluka 29827), 11.31 g (111.8 mmol) of triethylamine dried with molecular sieves and 300 ml of dry pentane are mixed at room temperature. Over 13 minutes 24.75 g (111.4 mmol) of trimethylsilyltrifluoromethylsulfonate (Fluka 91741) is added to the mixture. After stirring for 2.5 hours the supernatant pentane fraction is separated, solvent removed under reduced pressure and the remainder distilled under reduced pressure resulting in an isomer mixture of trimethylsiloxycyclopentadienes . 10.0 g of trimethylsiloxycyclopentadiene (64.8 mmol) (prepared analogously to the prior art procedures mentioned above or according to Example 2) is dissolved in 200 ml of pentane at room temperature. At -20°C 43.2 ml (64.8 mmol) of 1.5 M t-butyllithium solution in pentane is added. Temperature is increased to 20°C during 15 hours while stirring. The resulted solid product is separated by filtration and washed with 2 x 100 ml of pentane. The trimethylsiloxycyclopentadienyl lithium is isolated by removing any remaining solvent under reduced pressure . 10.0 mmol of trimethylsiloxycyclopentadienyl lithium is added to a mixture of 50 ml of diethylether and 50 ml of pentane at 25°. At -75°C, 1.27 g of ZrCl 4 (5.0 mmol) is added to the mixture. The reaction mixture is slowly warmed up to 25°C during 15 hours while stirring. Solvent is removed under reduced pressure and crude bis (trimethylsiloxycyclopentadienyl) -zirconium dichloride is isolated by pentane extraction and subsequent solvent removal . Example 2 Trimethylsiloxycyclopentadiene Trimethylsiloxycyclopentadiene can also by synthesised according to the description in Acta. Chem. Scandinavica, 43, 1989, 188-92. 1.74 g of LiBr (20 mmol, dried under vacuum at 400°C) is dissolved in 5.55 g of THF (77 mmol) . At -15°C 1.54 g of chlorotrimethylsilane (15 mmol), 1.23 g of cyclopent-2- en-1-one (15 mmol) and 1.51 g of trimethylamine (15 mmol, dry) are added to the solution. After 1 hour at -15°C and 24 hours at +40°C the crude product is isolated by low temperature aqueous NaCl/NaHC0 3 and pentane extractions. The crude trimethylsiloxycyclopentadienes are purified by distillation under reduced pressure. Example 3 Bis ( l- (t-butyldimethylsiloxy) -3 -methylcyclopentadienyl ) zirconium dichloride Method (A) : 1- (Tertbutyldimethylsiloxy) -3 - methylcyclopentadiene was prepared analogously to Example 4 (using commercially available 3- methylcyclopent-2-en-l-one (Fluka 66545)) as starting material. Yield 43%. The product was characterised by GC/MS (several isomers showing M + at m/z 210) . Bis (1- (tertbutyldimethylsiloxy) -3- methylcyclopentadienyl) zirconium dichloride was prepared analogously to Example 4 resulting in a mixture of meso type and racemic type complexes. X H-NMR (CDC1 3 ) :δ 5.82-5.29 (6 multiplets, total 3H) , 2.17 (s, 3H) , 0.96 (s, 9H) , 0.22 (s, 6H) . Method (B) : 1- (Tert . butyldimethylsiloxy) -3 -methylcyclopentadiene 8.00 ml (5.79 g, 57 mmol) diisopropylamine in 25 ml THF are placed in a heated 250 ml Schlenk flask and cooled to -70° C. 21.8 ml (3.498 g, 55 mmol) n-butyllithium (23% in hexane) are added dropwise over 10 minutes via a dropping funnel. After stirring for 30 minutes at - 70°C, a pale-yellow suspension is obtained which is then mixed within 25 minutes with a solution of 5.00 g (52 mmol) 3-methylcyclopentenone in 25 ml THF. The clear, yellow solution is stirred at -70° C for 90 minutes before 10.19 g (68 mmol) tert.butyl dimethylsilyl chloride in 15 ml THF is added rapidly (< 1 minute) . The reaction mixture is allowed to warm to ambient temperature within 60 minutes and is diluted with 25 ml each of hexane and diethylether. The organic phase is agitated with 100 ml 5% NaHC0 3 solution and 100 ml NH 4 C1 solution and is then dried over MgS0 4 . After filtering and centrifuging off of the solvents (40° C bath temperature, 100 mbar) a clear fluid is obtained as a raw product which is purified by vacuum distillation (Boiling point: 58 - 61° C at 1.5 - 2 mbar). Yield: 3.82 g (34 . 9% ) . ^- MR (CDC1 3 ) : δ = 0 . 13 ppm (s , 6H, 2 x Si -CH 3 ) , 0 . 95 ( s , 9H , Si - tBu) , 1 . 95 (m, 3H, CH 3 ) , 2 . 7 (m, 2H, CH 2 ) , 4 . 9 (m, IH , H olef ) , 5 , 78 (m, IH, H olef ) . 1- (tert .butyldimethylsiloxy) -3 -methylcyclopentadienyl lithium 2.96 ml (6.80 mmol) n-butyllithium in hexane (2.3 mol/1) is added dropwise at ambient temperature to a solution of 1.43 g (6.80 mmol) 1- (tert .butyldimethylsiloxy) -3- methylcyclopentadiene in 35 ml THF. A red solution is firstly obtained which turns yellow after a short while. After stirring for 60 hrs at ambient temperature, the solvent is completely removed in a high vacuum. The yellow, oily residue is taken up in 25 ml hexane. After vigorous stirring, a beige suspension is formed which is filtered. The colourless solid is washed with hexane and dried in a high vacuum. Yield: 0.912 g (62.0%) . Bis (1- (t-butyldimethylsiloxy) -3 -methylcyclopentadienyl) - zirconium dichloride 0.912 g (4.22 mmol) 1- (tert .butyldimethylsiloxy) -3 - methylcyclopentadienyl lithium and 0.491 g (2.11 mmol) zirconium tetrachloride are suspended in 80 ml toluene and stirred for 48 hrs at ambient temperature. Following this, the yellow reaction mixture is filtered and the solvent is removed completely. The solid is taken up in 25 ml hexane and crystallised at -30° C. The precipitated light-yellow crystals are filtered off and dried in a high vacuum. Yield: 0.574 g (46.9%) . Mass 580.900 g/mol . ^- MR (CDC1 3 ) : δ = 0.20 ppm (s, 12H, 4 x Si-CH 3 ) , 0.95 (s, 18H, 2 x Si-tBu), 2.16 (m, 6H, 2 x CH 3 ) , 5.27, 5.33, 5.44, 5.48, 5.72, 5.81 (6 x m, 6H, Cp-H) . Example 4 Bis (1- (t-butyldimethylsiloxy) 3 ,4- dimethylcyclopentadienyl) zirconium dichloride 40. Og (465 mmol) of crotonic acid (Fluka 28010), 25.1 g (418 mmol) of isopropanol (Merck 1.09634.2500), 200 ml of benzene, 4.2 g of cone. H 2 S0 4 and 2.1 g of para- toluene sulfonic acid was charged to a 500 ml flask equipped with magnetic stirrer bar and Dean-Stark water separator. The mixture was refluxed until water formation ceased. 200 ml of ether was added to the mixture, which was then washed with several portions of NaHC0 3 (aq. , sat.) until acids were neutralised. Organic solution was separated, dried with MgS0 and filtered. Solvent was removed under reduced pressure and the remainder distilled at 95°C (bath at 160°C) to give 30.5 g of isopropylcrotonate. Yield 57%. X H-NMR (CDC1 3 ) :δ 6.95 (dq, IH) , 5.82 (d, IH) , 5.05 (sept, IH) , 1.88 (d, 3H) , 1.25 (d, 6H) . 811 g of polyphosphoric acid (Fluka 81340) was loaded to a round bottomed flask equipped with a reflux condenser and a magnetic stirrer bar and heated to 100°C. 104 g (810 mmol) of isopropylcrotonate was added to the flask and the mixture was stirred for 2 hours at 100 °C. The resultant mixture was poured onto about 1.5 kg of crushed ice . At room temperature the mixture was saturated with NH 4 C1 and extracted with 4 x 100 ml of ether. The combined ether fractions were dried with MgS0 4 and filtered. Solvent was removed under reduced pressure and the remainder distilled (0.2 mbar, 33°C, bath 90°C) to give 47.99 g of 3,4- dimethylcyclopentenone. Yield 54%. X H-NMR (CDCI 3 ) :δ 5.86 (s, IH) , 2.80 (m, IH) , 2.64 (dd, IH) , 2 . 07 ( s , 3H) , 2 . 00 (dd , IH) , 1 . 18 (d , 3H) . 12.23 g (111.0 mmol) of 3, 4 -dimethylcyclopentenone, 11.31 g (111.8 mmol) of triethylamine dried with molecular sieves and 300 ml of dry pentane were mixed at room temperature. Over 13 minutes 29.44 g (111.4 mmol) of t-butyldimethylsilyltrifluoromethylsulfonate (Fluka 97742) was added to the mixture. After stirring for 2.5 hours the supernatant pentane fraction was separated, solvent removed under reduced pressure and the remainder distilled (0.03 mbar, 34-40°C, bath 100°C) resulting in 19.74 g of an isomer mixture of t-butyldimethylsiloxy- 3 , 4 -dimethylcyclopentadienes . Yield 79%. The product was characterised by GC/MS technique, which showed the presence of three components (GC) each showing M + peak at 224 (MS) . 10 g (44.6 mmol) of the isomer mixture of t- butyldimethylsiloxy-3 , 4-dimethylcyclopentadienes was mixed with 200 ml of pentane at room temperature. At -20°C, 28.4 ml (44.6 mmol) of 1.57 M t-butyllithium solution in hexanes (Acros 18128-0900) was added. Temperature was increased to 20 °C over 15 hours with stirring. The resultant solid product was separated by filtration and washed with 2 x 100 ml of pentane. Remaining solvent was removed under reduced pressure. 7.07 g of t-butyldimethylsiloxy-3 , 4- dimethylcyclopentadienyl lithium was isolated. Yield 69%. ^-NMR (THF-d 8 ) :δ 4.88 (s, 2H) , 1.95 (s, 6H) , 0.95 (s, 9H) , 0.08 (s, 6H) . 10 ml of ether and 10 ml of pentane were added to 1.36 g (5.90 mmol) of t-butyldimethylsiloxy-3 , 4- dimethylcyclopentadienyl lithium at -40 °C. Temperature was decreased to -75°C and 0.687 g (2.95 mmol) of ZrCl 4 (Strem Chemicals 93-4045) was added. Temperature was increased to 20°C over 24 hours with stirring. Solvent was removed under reduced pressure and the product was isolated by extracting the solid residue with 2 x 15 ml of pentane. Pentane removal resulted in a light yellow crude product, which was recrystallised in pentane to afford 800 mg of yellow crystalline bis(t- butyldimethylsiloxy-3 , 4-dimethylcyclopentadienyl) zirconium dichloride. Yield 44%. *H-NMR (C 5 D 6 ) :δ 5.71 (s, 2H) , 2.17 (s, 6H) , 1.00 (s, 9H) , 0.15 (s, 6H) . Elemental analysis: 51.47% wt . C (calc. 51.28), 7.79% wt. H (calc. 7.61), 11.45% wt . Cl (calc. 11.64), 15.17% wt. Zr (calc. 14.98), 9.40% wt . Si (calc. 9.22). Example 5 Bis (1-t-butyldimethylsiloxy) -2,3,4- trimethylcyclopentadienyl) zirconium dichloride Method (A) : 1- (t-Butyldimethylsiloxy) -3 , 4 , 5-trimethylcyclopentadiene was prepared analogously to Example 4. The product was characterised by GC/MS (2 main isomers showing M + at m/z 238) . Bis (t-butyldimethylsiloxy-3 ,4,5- trimethylcyclopentadienyl) zirconium dichloride was prepared analogously to Example 4 resulting in a mixture of meso type and racemic type complexes. ^-NMR (CDC1 3 ) :δ 5.46, 5.10 (2 singlets, =1H) , 2.03-1.89 (6 singlets, ~9 H) , 1.00 (s, 9H) , 0.24-0.05 (5 singlets, =6H) . The product was also characterised by mass spectroscopy (M + at m/z 637) . Method (B) : 1- (tert .butyldimethylsiloxy) -3 ,4 , 5-trimethyl- cyclopentadiene 15 ml diisopropylamine (11.1 g, 0.11 mol) and 100 ml THF were placed in a heated 250 ml three-neck flask, provided with a magnetic stirring rod, thermometer, dropping funnel, cooler and protective gas. The colourless clear solution was cooled to -60°C and then 40 ml butyllithium (23% in hexane, 0.1 mol) were added within 15 minutes, whereupon the solution became red- brown coloured. After stirring for a further 15 minutes at -60° C to -50° C, the colour of the reaction mixture changed to blue. Then a solution of 12.6 g trimethylcyclopentenone (98.3%, 0.1 mol) in THF were added within 11 minutes, following which a clear green solution resulted. Then the mixture was stirred again at -60° C to -50° C for 1.5 hours, and a solution of 19.6 g t-butyldimethylsilyl chloride (0.13 mol) in 30 ml THF was added dropwise within 14 minutes. After heating to ambient temperature, a green-brown clear solution was obtained which was then heated further to 40° C and stirred for 20 hours at 40° C, whereupon a white precipitate resulted. The progress of the reaction was followed by means of GC. For working up, 50 ml diethylether, 50 ml hexane and 100ml water were placed in a 500 ml separating funnel, then the reaction mixture was added, briefly agitated and then the lower aqueous phase was separated off. The organic phase was dried over 15 mg magnesium sulphate and concentrated in a rotation evaporator at 40° C bath temperature and lOOmbar. The residue was distilled over a short packed column. The product distilled over at 80° C head temperature and 1.9 mbar. Yield: 84.7% ' • H-NMR (CDC1 3 ) : δ = 0.18 ppm (s, 6H, 2 x Si-CH 3 ) , 1.00 (s, 9H, Si-tBu), 1.03 (d, 3H, aliph. CH 3 , J = 5.8 Hz), 1.70 (s, 3H, olef. CH 3 ) , 1.80 (s, 3H, olef. CH 3 ) , 2.65 (m, IH, H aliph ), 5.14 (s, IH, H olef ) . 1- (tert .butyldimethylsiloxy) -2 , 3 , 4-trimethylcyclopentadienyl lithium 9.12 ml (20.97 mmol) n-butyllithium in hexane (2.3 mol/1) are added dropwise to a solution of 1- (tert .butyldimethylsiloxy) -3,4, 5-trimethylcyclopentadiene in 100 ml hexane in approximately 10 minutes. A colourless suspension results which is stirred for 60 hrs at ambient temperature. The suspension is filtered, and the colourless solid is washed with 30 ml hexane and is then dried in a high vacuum. Yield: 4.44 g (86.7%) Bis (1- (tert .butyldimethylsiloxy) -2,3,4- trimethylcyclopentadienyl) zirconium dichloride 0.750 g (3.07 mmol) 1- (tert .butyldimethylsiloxy) -2 , 3 , 4- trimethylcyclopentadienyl lithium and 0.238 g (1.02 mmol) zirconium tetrachloride are suspended in 50 ml toluene and stirred for 12 hrs at ambient temperature. Then the reaction mixture is filtered and the solvent is completely removed. The solid remaining is taken up in 8 ml hexane and crystallised at -30° C. The precipitated yellow crystals are filtered off and dried in a high vacuum. Yield: 0.226 g (34.7%). Mass 637.008 g/mol . ^-NMR (CDC1 3 ) : δ = 0.07 ppm (s, 6H, 2 x Si-CH 3 ) , 0.18 ppm (s, 6H, 2 x Si-CH 3 ) , 0.98 (s, 18H, 2 x Si-tBu), 1.87, 1.97, 2.02 (3 x (s, 6H, CH 3 ) ) , 5.08 (s, 2H, 2 x Cp-H) . Example 6 Bis (triisopropylsiloxycyclopentadienyl) zirconium dichloride Triisopropylsiloxycyclopentadiene was prepared analogously to Example 4 using triisopropylsilyltrifluoromethylsulfonate (Fluka 91746) and cyclopent-2-enone (Fluka 29827) as starting materials. It was not isolated and analysed but lithiated immediately to avoid spontaneous Diels-Alder dimerisation. Lithiation was performed analogously to Example 4 and afforded triisopropylsiloxycyclopentadienyl lithium in 81% yield. X H-NMR (THF-d 8 ) :δ 5.22 (m, 2H) , 5.17 (m, 2H) , 1.11 (m, 3H) , 1.04 (d, 18H) . Bis (triisopropylsiloxycyclopentadienyl) zirconium dichloride was prepared analogously to Example 4 and afforded a mixture of isomers. UV treatment and subsequent recrystallisation resulted in the title compound in 26% yield. X H-NMR (CDC1 3 ) :δ 6.21 (m, 2H) , 5.61 (m, 2H) , 1.22 (m, 3H) , 1.09 (d-like, 18H) . M + -43 ( isopropyl ) is visible on MS . Example 7 Rac-diτnethylsilanediylbis (3- triisopropylsiloxycyclopentadienyl) zirconium dichloride 0.77 g (5.97 mmol) of dichlorodimethylsilane (Fluka 40150) and 70 ml of THF were mixed and cooled to -70°C. 2.92 g (11.95 mmol) of trisopropylsiloxycyclopentadienyl lithium was dissolved in 150 ml of THF and the resultant solution was added to silane/THF over 20 minutes at -70°C. Temperature was increased to room temperature over 20 hours with stirring. Solvent was removed under reduced pressure and the residue extracted with 2 x 50 ml of pentane. 2.91 g of dimethylbis (3 , 3 ' - (1- triisopropylsiloxycyclopentadienyl) ) silane was isolated upon removal of the solvent. Yield 91%. Product was characterised by GC/MS technique (one peak at GC, M + at m/z 532) . Dimethylsilanediylbis (1,1'- (3- triisopropylsiloxycyclopentadienyl) dilithium was prepared analogously to Example 4 using 2 equivalents of base. Yield 40%. ^-NMR (THF-d 8 ) : δ 5.53 (m, «2H) , 5.44 (m, ~2H) , 5.32 (m, *2H) , 1.16 (m, ~6H) , 2.05 (d-like, -36), 0.13 (s, 6H) . rac-Dimethylsilanediylbis (1,1'- (3- triisopropylsiloxycyclopentadienyl) zirconium dichloride was prepared analogously to Example 4 using 1 equivalent of the dilithium salt. The pentane insolubles were extracted using toluene to afford the title compound (rac.-meso>20 :1) in 18% yield. X H-NMR (CDC1 3 ) : δ 6.19 (m, 2H) , 5.47 (m, 2H) , 5.15 (m, 2H) , 1.22 (m, ~6H) , 1.06 (m, ~36H) , 0.60 (s, 6H) . M + -46 ( isopropyl ) found . Example 8 Meso-dimethylsilanediylbis (3- triisopropylsiloxycyclopentadienyl) zirconiumdichloride meso-Dimethylsilanediylbis (1, 1 ' - (3- triisopropylsiloxycyclopentadienyl) zirconium dichloride was isolated by recrystallisation of the pentane solubles of the crude product of Example 7 in pentane. Yield of the title compound 18%, rac :meso«l : 5. X H-NMR (CDC1 3 ) : δ 6.03 (m, 2H) , 5.65 (m, 2H) , 5.02 (m, 2H) , 1.22 (m, ~6H) , 1.06 (m, *36H) , 0.61 (s, 3H) , 0.60 (s, 3H) . M + -46 (isopropyl ) found . Example 9 Rac-dimethylsilanediyl-bis (1-t-butyldimethylsiloxy) -3,4- dimethyl-cyclopentadien-5-yl) zirconium dichloride Dimethylbis (1,1'- (2-tertbutyldimethylsiloxy-4, 5- dimethylcyclopentadienyl) silane was prepared analogously to Example 7. Yield 97%. The product was characterised by GC/MS (main peak in GC curve had M + at m/z 504) . rac-Dimethylsilanediylbis (l-tertbutyldimethylsiloxy-3 , 4- dimethylcyclopentadienyl) zirconium dichloride was prepared analogously to Example 7 without isolating the dilithium salt. The title compound was isolated by double crystallisation in pentane. Yield 3%. X H-NMR (C 6 D 6 ) : 6 . 30 ( s , 2H) , 2 . 29 (s , 3H) , 2 . 99 ( s , 3H) , 0 . 95 ( s , 18H) , 0 . 86 ( s , 6H) , 0 . 29 ( s , 6H) , 0 . 19 ( s , 6H) . Example 10 Dimethylsilanediyl (3-triisopropylsiloxy) -cyclopentadien- 1-yl) - (9-fluorenyl) zirconium dichloride Method (A) : 20.0 g (120.3 mmol) of fluorene (Fluka 46880) and 150 ml of toluene were mixed at room temperature. 90.0 ml (135 mmol) of 1.50 M solution of t-BuLi in hexanes was added over 10 minutes with stirring. After 15 hours the mixture was filtered and toluene insolubles washed with 2 x 100 ml of toluene. 12.7 g of fluorenyl lithium was isolated upon drying under reduced pressure. Yield 61%. X H-NMR (DMSO-d 6 ) : δ 7.85 (d, 2H) , 7.23 (d, 2H) , 6.79 (t, 2H) , 6.40 (t, 2H) , 5.87 (s, IH) . Method (B) : 20g (120 mmol) fluorene (Fluka 46880) and 150 ml of toluene were mixed at room temperature. 77.6 ml (135 mmol) of 1.74 M solution of t-BuLi in hexanes was added during 10 minutes while stirring. After 18 hours the mixture was filtered and toluene insolubles washed with 50 ml of toluene and 2x50 ml of pentane. 20.4 g of fluorenyl lithium was isolated upon drying under reduced pressure. Yield 98%. ^- MR (DMSO-d 6 ) : 7.85 (d, 2H),7.23 (d, 2H) , 6.79 (t, 2H) , 6.40 (t, 2H) , 5.87 (s, IH) . Method (A) : 26 g (ca. 200 mmol) of dichlorodimethylsilane was mixed with 10 ml of THF. 5.0 g (29 mmol) of fluorenyl lithium was dissolved in 30 ml of THF and the solution was added to silane/THF at 60 °C over 30 seconds with stirring. After 50 minutes at 60 °C the solvent was removed under reduced pressure and the residue was extracted with 50 ml of pentane. 1.9 g of chlorodimethylfluorenylsilane slightly contaminated by dimethylbisfluorenylsilane was isolated upon solvent removal. Sublimation (100°C, 0.03 mbar) resulted in chlorodimethylfluoren-9-ylsilane. Calculated yield after sublimation 17%. X H-NMR (DMSO-d 6 ) : δ 8.00 (d, 2H) , 7.64 (d, 2H) , 7.38 (m, 4H) , 4.35 (s, IH) , 0.25 (s, 6H) . Method (B) : 56.2 g (435 mmol) of dichlorodimethylsilane was added as one batch to a mixture of 150 ml of pentane and 15.0 g (87.1 mmol) of fluorenyl lithium at -70°C. The mixture was stirred for 18 hours while warming up to 20°C. Filtration, extraction by pentane and sublimation resulted in 14.8 g of chlorodimethylfluoren- 9-ylsilane. Yield 66% . U-NMR (DMSO-d 6 ) : 8.00 (d, 2H) , 7.64 (d, 2H) , 7.38 (m, 4H) , 4.35 (s, IH) , 0.25 (s, 6H) . X H-NMR (CDC1 3 ) : 7.85 (d, 2H) , 7.66 (d, 2H) , 7.35 (m, 4H) , 4.09 (s, IH) , 0.16 (s, 6H) . Elemental analysis: 69.67%-wt.C (calc. 69.61), 5.76%- wt.H (calc. 5.84), 13.90%-wt.Cl (calc. 13.70), 10.69%- wt.Si (calc. 10.85) . Method (A) : 1.00 g (3.86 mmol) of chlorodimethylfluoren-9-ylsilane was dissolved in 20 ml of THF. 0.94 g (3.86 mmol) of triisopropylsiloxycyclopentadienyl lithium was dissolved in 20 ml of THF and the solution was added to silane/THF over 20 minutes with stirring. After 18 hours solvent was removed under reduced pressure and the residue was extracted with 40 + 5 ml of pentane. 1.39 g of (3- triisopropylsiloxycyclopentadien 1-yl) (fluoren-9- yl) dimethylsilane was isolated upon solvent removal. Yield 78%. The product was characterised by CG/MS (main peak on GC curve had M + at m/z 460) . Method (B) : 5.10 g (19.3 mmol) of chlorodimethylfluoren-9-ylsilane was dissolved in 100 ml of THF. 4.72 g (19.3 mmol) of triisopropylsiloxycyclopentadienyl lithium dissolved in 100 ml of THF was added to the silane/THF during 25 minutes at 20 °C while stirring. After 18 hours solvent was removed under reduced pressure and the remainder was extracted with 250 ml of pentane, 8.8 g of (3- triisopropylsiloxycyclopentadien-1-yl) (9- fluorenyl) dimethylsilane was isolated upon solvent removal. Yield 99%. The product was characterised by CG/MS (main peak on GC curve had M + at m/z=460) . Method (A) : Dimethylsilanediyl (3-triisopropylsiloxycyclopentadien-l- yl) (fluoren-9-yl) zirconium dichloride was prepared analogously to Example 9. It was isolated by double crystallisation (toluene, dichloromethane) in 9% yield. ' ■ H-N R (CDC1 3 ) : δ 8.16 (d, 2H) , 7.65-7.45 (2 multiplets partly overlapping each other, tot. 4H) , 7.28 (m, 2H) , 5.80 (m, IH) , 5.40 (m, IH) , 5.02 (m, IH) . 1.20-0.9 (several signals partly overlapping each other, tot. 27H) . Method (B) : At 20°C, 23.9 ml (38.2 mmol) of t-BuLi in hexanes was added to 8.8 g (19.1 mmol) of (3 -triisopropylsiloxy- cyclopentadien-1-yl) (9-fluorenyl) dimethylsilane dissolved in 100 ml of pentane. After 18 hours, filtration, washing with pentane and solvent removal resulted in 8.7 g (18.4 mmol) of dimethylsilanediyl (9- fluorenyl) (3-triisopropylsiloxycyclopentadien-l- yl) dilithium. Yield 95%. 50 ml of pentane and 50 ml of diethylether were added to 5.0 g (10.6 mmol) of dimethylsilanediyl (9-fluorenyl) (3- triisopropylsiloxycyclopentadien-1-yl) dilithium. 2.47 g (10.58 mmol) of ZrCl 4 was added as a solid at -50°C. After 18 hours at 20 °C solvent was removed under reduced pressure, the crude product was washed with pentane, extracted with CH 2 C1 2 and recrystallised from CH 2 C1 2 to afford 1.36 g (2.19 mmol) of dimethylsilanediyl (3- triisopropylsiloxycyclopentadien-1-yl) (9- fluorenyl) zirconium dichloride. Yield 21%. X H-NMR (CDCL 3 ) : 8.16 (d, 2H) , 7.65-7.45 (2 multiplets partly overlapping each other, tot. 4H),7.28 (m, 2H) , 5.80 (m, IH) , 5.40 (m, IH) , 5.02 (m, IH) . 1.20-0.9 (several signals partly overlapping each other, tot. 27H) . Example 11 Bis (t-butyldimethylsiloxy-3 , 4- dimethylcyclopentadienyl) zirconium dimethyl 1.00 g (1.64 mmol) of bis (t-butyldimethylsiloxy-3 , 4- dimethylcyclopentadienyl) zirconium dichloride was dissolved 10 ml of diethylether. 1.9 ml (3.28 mmol) of 1.7 "M methyllithium solution in ether (Fluka 67740) was added at -40°C with stirring. After 20 hours at room temperature solvent was removed under reduced pressure . The residue was extracted with 2 x 10 ml of pentane. Pentane removal resulted in 0.93 g of bis(t- butyldimethylsiloxy-3 , 4- dimethylcyclopentadienyl) zirconium dimethyl. Yield 100%. ^-N R (C 6 D 6 ) : 5.49 (s, 4H) , 2.16 (s, 12H) , 1.12 (s, 18H) , 0.29 (s, 12H) , 0.09 (s, 6H) . Example 12 Dimethylsilanediyl (3-trimethylsiloxycyclopentadien-l-yl) (fluoren-9-yl) zirconium dichloride 1.00 g (3.86 mmol) of chlorodimethylfluoren-9-ylsilane (synthesised as described in Example 10) is dissolved in 20 ml of THF. 3.86 mmol of trimethylsiloxycyclopentadienyl lithium or trimethylsiloxycyclopentadiene activated by some other way is dissolved in 20 ml of THF and the solution is added to silane/THF during 20 minutes while stirring. After 18 hours solvent is removed under reduced pressure and the remainder is extracted with appropriate solvent followed by separation to afford (3-trimethylsiloxy- cyclopentadien-1-yl) (fluoren-9-yl) di ethylsilane . (3-trimethylsiloxycyclopentadien-l-yl) (fluoren-9- yl) dimethylsilane is dissolved in pentane at room temperature and the reaction mixture cooled to -20°C before 2 equivalents of t-BuLi in pentane is added. Temperature is increased to 20°C over 15 hours whilst stirring. The product is washed with pentane and isolated after removal of the solvent in vacuo. Complex formation (3-trimethylsiloxycyclopentadien-l-yl) (fluoren-9- yl) dimethylsilane lithium is added to a 1:1 pentane/ether mixture. At -75°C, 0.5 equivalents of ZrCl 4 is added and the mixture warmed to 25°C over 15 hours. The solvent is removed in vacuo to yield the title compound. Example 13 Dimethylsilanediyl (2-triisopropylsiloxycyclopentadien-l- yl) (9-fluorenyl) zirconium dichloride Dimethylsilanediyl (2-triisopropylsiloxycyclopentadien-l- yl) (9-fluorenyl) zirconium dichloride was isolated as a minor isomer from the crude product of Example 10 by recrystaliisation. X H-NMR (CDC1 3 ) : 8.12 (d, 2H) , 7.66 (t, 2H) , 7.57 (t, 2H) , 7.25 (m, 2H, overlapping with solvent), 6.23 (m, IH) , 6.12 (m, IH) , 5.33 (m, IH) , 1.28-1.04 (several signals in one group, 27H) . Example 14 Dimethylsilanediyl (2- (t-butyldimethylsiloxy) -4,5- dimethylcyclopentadien-1-yl) (9-fluorenyl) zirconium dichloride 4.0 g (15.45 mmol) of chlorodimethylfluoren-9-ylsilane was dissolved in 80 ml of THF and added to 3.56 g (15.45 mmol) of 1- (t-butyldimethylsiloxy) -3, 4- dimethylsiloxycyclopentadienyl lithium dissolved in 80 ml of THF at 60°C during 30 minutes. After 1.5 hours at 60°C, solvent was removed under reduced pressure and the product was extracted from the solid residue with pentane. 3.06 g of (2- (t-butyldimethylsiloxy) -4, 5- dimethylcyclopentadien-1-yl) (9-fluorenyl) dimethylsilane was isolated upon solvent removal. Yield 44%. The product was characterised by CG/MS (main peak on GC curve had m/z=446 (M + ) ) . At 20°C, 6.1 ml (59.0 mmol) of dimethoxyethane and 16.8 ml (26.8 mmol) of t-BuLi in hexanes was added to 6.00 g (13.4 mmol) of (2- (t-butyldimethylsiloxy) -4, 5- dimethylcyclopentadien-1-yl) (9-fluorenyl) dimethysilane dissolved in 100 ml of heptane. After 18 hours at 20°C and 2 hours at 70°C the mixture was filtered and the crude product washed with 3x50 ml of pentane to afford 8.0 g of a mixture of dimethylsilanediyl (9-fluorenyl) (2- (t-butyldimethylsiloxy) -4, 5-dimethyleyelopentadien-1- yl) )dilithium (78 %-wt.) and dimethoxyethane (22%-wt.). Yield 100%. ^-NMR (THF-d 8 ) : 7.82 (m, 4H) , 6.77 (m, 2H) , 6.39 (m, 4H) , 4.96 (s, IH) , 3.44 (s, 9H) , 3.29 (s, 13H) , 1.81 (s, 6H) , 1.10 (s, 9H) , 0.69 (s, 6H) , 0.28 (s, 6H) . 50 ml of toluene and 5 ml of THF were added to 3.86 g (6.55 mmol of the salt) of the mixture of dimethylsilanediyl (9-fluorenyl) (2- (t-butyldimethyl- siloxy) -4, 5-dimethylcyclopentadien-1-yl) dilithium (78 %-wt.) and dimethoxyethane (22%-wt.). 1.53 g (6.55mmol) of ZrCl 4 was added as a solid to the mixture at -78°C. The mixture was warmed up to 20 °C over 10 hours and, after 56 hours at 20 °C, solvent was removed under reduced pressure. The solid crude produce was washed with 50 ml of pentane and then extracted with 50 ml of CH 2 C1 2 to afford 2.5 g (4.1 mmol) of dimethylsilanediyl- (2- (t-butyldimethylsiloxy) -4, 5-dimethylcyclopentadien-l- yl) (9-fluorenyl) zirconium dichloride as CH 2 C1 2 solubles. Yield 63%. ^Η-NMR (CHC1 3 ) : 8.07 (d, 2H) , 7.7-7.54 (2 multiplets partly overlapping each other, tot. 4H) , 7.25-7.12 (m, 2H) , 5.76 (s, IH) , 1.98 (s, 3H) , 1.88 (s, 3H) , 1.28 (s, 3H) , 1.25 (s, 3H) , 0.97 (s, 9H) , 0.22 (s, 3H) , 0.19 (s, 3H) . Example 15 HDPE Polmyerisations Polyethylene was prepared using the procatalysts of Examples 3, 4, 5, 6, 7, 9 and 10. The quantities of procatalyst used, the co-catalyst used, the polymerisation techniques used, the catalyst activities, the polymer yields, and polymer properties are set out in Table 1 below. TABLE 1 CO c CD CO 10 m co m m 73 c 15 m ro 20 1. 169.3mg supported catalyst weight, i.e. activated complex 2. Al.Zr molar ratio = 500 25 3. Triisobutylalumoxane {97.5% - Albemarle) 4. Tris (pentafluorophenyl)boron (Alza, sublimated before use) 5. B:Zr molar ratio = 2 Example 16 LLDPE Polymerisations LLDPE was produced using the procatalysts of Examples 3 to 9 and 1-hexene as comonomer. The quantities of procatalyst used, the co-catalyst used, the polymerisation techniques used, the catalyst activities, the polymer yields, and polymer properties are set out in Table 2 below TABLE 2 CO c CD CO m co 10 m m c m ro 15 20 1. 107.7 mg on supported catalyst Example 17 Propylene polymerisations Propylene was polymerised using the procatalyst of Examples 9, 10, 13 and 14. The details of reaction and yield are set out in Table 3 below TABLE 3 CO c CD CO in o m co m m 10 c 1. mg supported catalyst m ro 2. Al:Zr molar ratio 10600 3. 6.7 mmol H 2 present during polymerisation 15 4. 0.49 mmol TEA present during polymerisation 5. MFR 2 , melt flow rate, ISO 1133, T=230°C, 2.16 kg load 6. XS, xylene solubles (wt-% fraction of polymer soluble in xylene) 7. Heating time plus time at 70°C 8. μmol procatalyst Polymerisation method A The complex rac-Me 2 Si (3-iPr 3 SiO-Cp) 2 ZrCl 2 , 9 mg, was dissolved in 1.8g of MAO solution (30 w% in toluene from Albermarle), and stirred for 30 minutes (Al :Zr=8200) . The 0.25g portion of the complex solution above (0.15 ml) and additional 3.0 ml MAO solution (30 w% in toluene) was charged to a 2 litre steel reactor, 650 ml liq propylene added. Prepolymerisation at 15°C for 8 minutes, and then rapid heat-up to 70°C, and continued for 60 minutes. Polymerisation was ended by depressurizing the reactor, and powder was vacuum dried. Polymerisation method B The complex rac-Me 2 Si (3-iPr 3 SiO-Cp) 2 ZrCl 2 , 9 mg, was dissolved in 1.8g of MAO solution (30 w% in toluene from Albermarle), and stirred for 30 minutes. A 1.55g portion of this solution was mixed with 1.112g silica (Grace Sylopol 2104 calcined at 800°C) , which corresponds to a porefilling of 1.20 ml/g carrier. The heterogenised catalyst was dried by nitrogen flushing for 60 minutes. Calculated metal content in catalyst is 0.06 w% Zr and 12.35 w% Al . Heterogenised catalyst was added as dry powder to an inert 2 litre reactor. Propylene (650 ml at 15°C) was added, and stirrer activated. Prepolymerisation at 15°C for 8 minutes, and then rapid heat-up to 70°C, and continuedfor 60 minutes. Polymerisation was ended by depressurizing the reactor, and powder was vacuum dried. In subsequent runs, triethyl aluminium and hydrogen was added, see results table. Polymerisation Method C Typically 4 mg of procatalyst is weighed to a septum flask in a glove box and a toluene solution of MAO (Albemarle, 15.5%-w of Al) is added to reach an Al : Zr molar ratio of 1000. The appropriate amount of the catalyst solution is injected into an addition vessel The reactor is evacuated and flushed with nitrogen several times at 70°C. At 15-17°C, 200 μl of 10%-wt. solution of triethylaluminum in pentane and 1.1 kg of liquid propene are added and stirring started. The catalyst is fed to the reactor and heating is started. After the appropriate period of time at run temperature the reactor is vented, flushed with nitrogen, opened and the polymer is isolated. Polymerisation method D A heterogenized catalyst is prepared by adding procatalyst and MAO to a calcined silica carrier (Sylopol 55SJ) to give a 0.2% wt . Zr content and an Al:Zr molar ratio of 200. The reactor is evacuated and flushed with nitrogen several times at 70°C. At 15-17°C, 200 μl of 10%-wt. solution of triethylaluminum in pentane and 1.1 kg of liquid propene are added and stirring started. The catalyst is fed to the reactor and heating is started. After the appropriate period of time at run temperature the reactor is vented, flushed with nitrogen, opened and the polymer is isolated. Example 18 (Comparative) Three metallocenes of similar structure to the compounds of the invention were similarly tested for catalyst activity using MAO and HIBAO cocatalysts. The compounds tested were rac-ethylene-bis (2- tertbutyldimethylsiloxyindenyl) zirconium dichloride (Compound A) , rac-ethylene-bisindenyl zirconium dichloride (Compound B) and bis (n-butylcyclopentadienyl) zirconium dichloride (Compound C) . The results, set out in Table 4 below demonstrate poor or relatively poor activity with HIBAO. TABLE 4 CO c CD CO m co I m m in in ^ 10 c as (i) but using 1.8L pentane as reaction medium, 70°C polymerization temperature and m ro 8.6 bar total pressure (ethylene partial pressure of 5 bar) as (i) but using 1.8L isobutane as reaction medium, 70°C polymerization temperature 15 and 15.8 bar total pressure (ethylene partial pressure of 5 bar)

Claims: CLAIMS : 1. A metallocene procatalyst compound comprising a group 3 to 7 transition metal η-liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group . 2. A compound as claimed in claim 1 being a complex of a group 3 to 7 transition metal and a ligand compound of formula IV where X, Y and T are ring carbons or ring heteroatoms; each R', which may be the same or different is a R + , OR + , SR + , NR + 2 or PR + 2 group where each R + is a C^g hydrocarbyl group, a hydrocarbylsiloxy group; each R", which may be the same or different, is a ring substituent which does not form a bond to a metal η- bonded by the C 2 XYT ring and is other than a ring fused to the C 2 XYT ring; n is zero or a positive integer; m is zero or 1; and R"' is an η-ligand linked to the C 2 XYT ring by a 1 to 3 atom bridge . 3. A compound as claimed in claim 2 wherein the ligand compound is of formula VI where R' is as defined in claim 2; Y' is P, B, CH or C- CH 3 ; R* is H or CH 3 ; and R"" is H, CH 3 or Bg-ETA where Bg is a linker group providing a one or two atom bridge between ETA and the C 4 Y' ring, and ETA is a cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, tetrahydrofluorenyl or octahydrofluorenyl or other closed ring η-ligand group. 4. A compound as claimed in either of claims 2 and 3 wherein R 3 'SiO- is t-butyl-Si (CH 3 ) 2 0- , (prop-2-yl) 3 SiO- or CH 2 =CH(CH 2 ) 6 Si(CH 3 ) 2 0-. 5. A compound as claimed in any one of the preceding claims wherein the metal is Cr, Ti, Zr or Hf . 6 . An olefin polymerisation catalyst system comprising or produced by reaction of (i) a metallocene procatalyst compound comprising a group 3 to 7 transition metal η- liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group and (ii) a cocatalyst, eg an aluminium alkyl compound, in particular an alumoxane, especially an aluminium alkyl compound comprising alkyl groups containing at least two carbon atoms . 7. A catalyst system as claimed in claim 6 wherein said cocatalyst is an alumoxane. 8. A catalyst system as claimed in either of claims 6 and 7 comprising a porous particulate support material impregnated with said metallocene compound and cocatalyst or the reaction product thereof. 9. A catalyst system as claimed in any one of claims 6 to 8 wherein said metallocene compound is a compound as claimed in any one of claims 2 to 5. 10. A process for olefin polymerisation comprising polymerising an olefin in the presence of a metallocene compound comprising a group 3 to 7 transition metal η- liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group. 11. A process for the preparation of a metallocene procatalyst, said process comprising metallating with a group 3 to 7 transition metal a ligand comprising a siloxy-substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group . 12. The use of a metallocene compound comprising a group 3 to 7 transition metal η-liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclo pentadienyl group in olefin polymerization, especially ethylene or propylene, more especially ethylene, polymerisation or copolymerisation. 13. An olefin polymer produced by a polymerisation catalysed by a metallocene compound comprising a group 3 to 7 transition metal η-liganded by a siloxy substituted, monocyclic, homo- or heterocyclic cyclopentadienyl group .

Inventors: ANDELL OVE, HOIKKA JOUNI, RAUTIO SOILE, ANDELL, OVE, HOIKKA, JOUNI, RAUTIO, SOILE
Applicants: ANDELL OVE, BOREALIS TECH OY, COCKBAIN JULIAN, HOIKKA JOUNI, RAUTIO SOILE, ANDELL, OVE, BOREALIS TECHNOLOGY OY, COCKBAIN, JULIAN, HOIKKA, JOUNI, RAUTIO, SOILE
Application year: 2001
Main classification: C08F10
IPC codes: C07F17, C08F4, C08F10, C08F110, C08F210