The present invention i elates to novel cyclooctatetraendiyl complexes of Group IV metals and to then use as olefin polymerisation catalysts

Tiaditional oletϊn polvmensation catalysts have been based on transition metal salts of Gt oup I V to VI I I metals in combination with base metal alkyls of S Group 1 to III metals Such catalysts known as Ziegler-Natta catalysts have been used to poiymense olefins m solution, slurry and gas phase processes Another catalyst system used toi polymensation of olefins is based on chromium oxide and is often referred to as Phillips-type catalyst system

Catalysts based on metalloce e complexes have also been widely used for 0 the polymerisation oi olefins These complexes are used in catalyst systems comprising a bιs(cγclυpeπtadιenyl) transition metal and a cocatalyst Such bis (Cp) transition metal complexes ai e typically based on titanium or zirconium metals and when used ai e cocatalvsed with aluminium compounds such as aluminoxanes When used in gas phase pi ocesses such bis (Cp) systems may be supported on silica

Other complexes having a single cyclopentadienvl ring ligand and a hetero atom bonded to the metal atom may also be used in conjunction with aluminoxanes Such complexes ai e referred to as 'constrained geometry' complexes and ai e descnbed in EP 420436 and EP 416815 0 Similai catalyst systems ai e taught in EP 418044 and WO 92/00333 but which have a non-cooi d ating anion as the activating cocatalyst In these systems the catalyst is pi epared as the pi oduct of a mono(cyclopentadιenyl) heteroatom metal complex and an ionic activatoi compound and such systems have been referred to as ionic mono(cyclopentadιenyl) catalysts Typical ionic activators for S such systems may be exemplified by boi ates oi boranes

More recently EP 672676 and EP 757996 describe novel Group IV or V metal complexes comprising cyclooctatetraendiyl ligands which are useful as olefin polymerisation catalysts

We have now found that certain bridged complexes comprising the cyclooctatetraendiyl ligand may be prepared and have been found to be particularly suitable as components of catalyst systems useful for the polymerisation of olefins.

Thus according to the present invention there is provided a complex suitable for use in a catah st system for the polymerisation of olefins comprising a transition metal complex having formula I

I wherein

M is zirconium, hafnium oi titanium,

Y is an aniomc ligand foi example halide oi hydride or a hydrocarbyl group having from I to 20 carbon atoms and

Z is a C l to C4 alkylene l dical oi a dialkyl germanium or dialkyl silicon or an alkyl phosphine or amtne l dical oi bts-dialkylsilyl- or bis-dialkyl germanyl- containmg hydrocarbyl groups having 1 -4 carbon atoms bridging the cyclopentadienyl and cycloctatetraene nuclei, R = hydrogen, alkyl, oi silvl, and may be the same or different n = 1 -7

R ¹ = hydrogen, alkyl oi silvl and may be the same or different or two or more R ^l groups togethei form a fused nng m = 1 -4 The cyclopentadienyl I ing may optionally be substituted for example by alkyl groups or by sustituents which form a condensed ring e g indenyl Examples of silyl substituents ai e dialkysilyl or trialkylsilyl The cyclooctateti aene nng is pi eferably substituted by trimethylsilyl groups, most preferably in the 1 , 4 - position i

The anionic groups suitable for use as the y ligand include hydride, halogen, alkyl etc

Preferred complexes according to the present invention are those wherein Z is a dimethylsilyl bridging group and Y is a halogen

The preferred complexes are those wherein M is zirconium.

A particularly preferred complex is

The complexes according to the pi esent invention may be used in catalyst systems in the presence of suitable cocatalysts, for example organometallic compounds having a metal from Group I A, II A, IIB or IIIB of the Periodic Table Such cocataiysts are known for their use in the polymerisation of olefins and include organoaluminium compounds such as trialkyl, alkyl hydride, alkyl halo and alkyl alkoxy aluminium compounds and alumoxanes, the latter being preferred A preferred co-catalyst is methyl aluminoxane (MAO) and commercial materials known as modified MAO (MMAO)

Other suitable cocatalysts are boron compounds for example boranes such as tris (pentafluorophenyl) boron or borates such as trialkylammonium tetraphenylborates or N,N-dialkyl anilinium tetraphenylborates Such activating cocatalysts are particularly suitable with complexes having anionic Y ligands comprising alkyl ligands for example methyl ligands

The co-catalyst may be mixed with the complex optionally on an inorganic support Alternatively, the co-catalyst may be added to the polymerisation medium along with the complex The co-catalyst e g MAO may also be prepared in-situ by pretreating the support with for example trimethyl aluminium or other alkyl aluminium Suitably, the amount of co-catalyst mixed with complex may be such as to provide an atom ratio of M from the complex to the metal in the co-catalyst of 1 to 10,000 10,000 to 1 for aluminoxanes and 1 to 100 100 to 1 otherwise.

The complex may suitably be supported on a suitable inorganic support material

Any suitable inorganic support may be used for example, inorganic oxides such as silica, alumina Equally suitable inorganic halides may be used Suitable hahdes include Group IIA halides e g magnesium chloride

A preferred inorganic support is silica

The complex may be impregnated onto the support material under anhydrous conditions and under an inert atmosphere The impregnation can be conducted using an inert solvent, in which case the solvent may then be evaporated under reduced pi essui e The impregnated support may then be heated to remove any remaining solvent The complex and co-cataiyst may be dissolved in the inert solvent Suitable inert solvents include aromatic hydrocarbons such as toluene The solution of complex and co-catalyst may then be added to the inorganic support material Other suitable means of foi ming a supported polymerisation catalyst may also be used

Thus according to anothei aspect of the present invention there is provided a catalyst composition suitable for the polymerisation of olefins comprising (A) a complex as disclosed above and (B) an activating cocatalyst The olefin polymerisation catalysts according to the present invention may be used to produce polymers using solution, slurry or gas phase polymerisation processes Methods and appai tus tor effecting such polymerisation reactions are well known The catalysts according to the present invention can be used in similar amounts and undei similai conditions to known olefin polymerisation catalysts The complexes according to the present invention may also be used in the presence of conventional polymerisation catalysts e g Ziegler catalysts or metailocenes

Complexes according to the pi esent invention may be suitably prepared from l ,4-bιs(trιmethylsιlyl) cyclooctatetraene as shown in the accompanying Figure 1 which repi esents prepai ative l outes to complexes of Formula I

The following examples illusti te the preparation of complexes according to the pi esent invention In the examples COT and COT" represent the cyclooctateti aene and bιs(tπmethvlsιlyl) cyclooctatetraene iigands respectively -Examples Exmnnle 1

Preparation of precursor ICOT" - SiMe,l - Cn (H)

A high pressure ampoule ( 100 ml) was charged with 1,4-bis (trimethylsilyl) cyclooctatetraene ( 1 14g, 4 62 mmol) HMe2SiCl (0 55 ml, 4 85 mmol) and Pt

(CγHjrjb (0 0 I6g, 0 033 mmol) The system was closed under argon ( 1 atm) The reaction was stirred for

18 hours The excess of H e2SiCl was removed in vacuo (short time). The resulting dark brown oil was diluted with 10 ml of diethyl ether The solution of

[COT"-SiMe2Cl] in diethyl ether was added via cannula to a suspension at -78°C of Na(C5H5) (0 40 g, 4 67 mmol) in diethyl ether The temperature was allowed to warm up to room temperature, while stirring for 50 5 hours The solution was filtered through glass filter paper and the solvent was removed in vacuo leading to

1 1 l g of an orange oil

Example 2

Preparation of ICOT" - SilV^ Cpl ZrCl To a solution of [COT" - SiMe ₂ - Cp(H)] (0 23g, 0 61 mmol) prepared according to Example 1 diethyl ether ( 1 5 ml, -90°C) was added 1 30 ml ( 1.82 mmol) of MeLi ( 1 ,4M in diethyl ether) via syringe The reaction was allowed to warm up to + 10°C over 1 5 hours The resulting lithium salt [Li2 COT" - SiMβ2 -

CpLi] was added dropwise to a suspension of ZrCl4(THF)2 (0 23 g, 0 61 mmol) in diethyl ether (<-90°C) The solution was stirred for 15 5 hours while the reaction was allowed to warm up to loom temperature After the solvent was removed in vacuo, the resulting compound was dissolved in petroleum ether 40/60 and the solution was filtrated through C elite The removal of the solvent in vacuo resulted in a dark brown oily solid Example 3 and 4

Polymerisation - Slurry Phase

Catalyst Evaluation

Catalyst evaluation was carried out in a stirred 3 L autoclave operated in slurry mode using isobutane solvent Agitation was carried out using a paddle stirrer and heat exchange carried out via the autoclave jacket Temperature was controlled using a cascade controller and data logging was carried out using a HP

Vectra QS20 compute!

Before catalyst evaluation, the autoclave was cleaned, assembled and baked

^• out by heating the autoclave to 95°C and purging the vessel with dray O ₂ free N ₂ ( 0 5L/mιn) for 1 hour The vessel was then cooled down under N ₂ to about 40°C

and the manifold checked for tightness The autoclave was then pressure tested and sealed under N ₂ at atmospheric pressure N ₂ was then purged through the catalyst injection system until load-up

Data logging was started and the catalyst injection system purged with N ₂ . Catalyst solutions were then injected into the autoclave using N ₂ overpressure (5 bar(g) above reactor contents) Polymerisation was allowed to continue, ethylene being taken up upon demand (via a constant pressure mass flow controller) After the test period, the ethylene gas was isolated, the reactor cooled, depressured and the polymer unloaded Example 3

Ethylene was polymerised at 30°C in isobutane A solution containing 1 l mg dissovled in 1 7 2 ml MAO ( I 55 in toluene) and 4 8 ml toluene was prepared 2ml of this solution (2mg catalyst, 4 03 lnicromol) were added to the slurry reactor and after first 5h another 2ml 18 7g poiyethyiene were obtained after 1 h The Mw was very high 1 1 50000, Mn 447000, PD 2 4 Example 4

Ethylene was polymei ised at 75°C using a similar catalyst solution this time using 3 injections of catalyst - 2 3ml (0 5 mg catalyst), 2 3 mis after 15 mins and 4 6 is after a funhei 30 mm 10 4g polyethylene was isolated after 1 5 hrs MΛV 444000, Mn 165000, PD 2 7

The results f i Examples 3 and 4 are given below in Table 1

TABLE 1

Example 5 Polymerisation

Ethylene was polymerised in the presence of 10 mg [COT" - SiMe2-Cp] ZrCl prepared in Example 2 and methyl aluminoxane ( 1 ml, 2M in toluene) diluted in toluene (30 ml) and ethylene (7 bar) The temperature (23°C) increased to 38°C during the reaction After 1 min 2 6g of polyethylene was obtained Example 6 Polymerisation

Propylene was polymerised m the presence of 10 mg [COT" - SiMe2 Cp] ZrCl prepared in Example 2 and methyl aluminoxane (20 ml, 2M in toluene) diluted in toluene (30 ml) and propylene ( 7 bar) The temperature (20°C) increased to 44°C during the reaction After 10- 1 min 4 5 g polypropylene was obtained Example 7

A solution of MAO in toluene (Witco, 7ml, 2. 13M, 15mmol Al) was added by syringe to a schlenk tube containing [COT" - SiMe2 Cp] ZrCl (49.5 mg, 0 l mmol) under N2 An additional 3 ml of toluene was added to the solution The solution was then added by cannula wire to a rapidly stirring ES70 silica (2g, previously calcinated at 800°C and further dehydroxylated by trimethylaluminium treatment) under N2 at 20°C This slurry was stii red for 1 hour at 20°C, then the

toluene was removed in vaccuo at 40°C for 3 hours to give a free flowing off-white solid.

Example 8

A solution of MMAO is toluene (Akzo type 4, 6.25 ml, 2.4M, 15mmol Al) was added by syringe to a schlenk tube containing [COT" - SiMe2 Cp] ZrCl (49.5 mg, 0. 1 mmol) under N2 An additional 2.5 ml of toluene was added to the solution This solution was then added by cannula wire to a rapidly stirring ES70 silica (2g, previously calcinated at 800°C and further dehydroxylated by trimethylaluminium treatment) under N2 at 20°C. This slurry was stirred for 1 hour at 20°C, then the toluene was removed in vaccuo at 40°C for 1 hour to give a free flowing off-white solid Polymerisations - Gas phase

A 3 litre autoclave was heated, whilst stirring, at 90°C for 1 hour with a flow of 1 -2 litre/min nitrogen purging the reactor. During this time the catalyst (normally 0 25g) was added, under nitrogen, to the catalyst injector constructed for a non return valve and a ball valve The catalyst was kept in a nitrogen atmosphere within the catalyst injector and attached to the reactor in such a way to purge any air from the couplings The reactor was cooled to below 50°C and 300 g of predried sodium chloride added under nitrogen atmosphere The NaCl (1mm diameter) was dried at 1 50°C under vacuum for more than 4 hours. TMA (3ml, 2M in hexane) was added to the reactor under nitrogen at 50°C. The reactor was boxed in nitrogen at 1 atmosphere and the temperature then increased to 80°C for greater than 20 minutes The reactor was purged with nitrogen at 80°C and then left with 1 bar nitrogen. The reactor was adjusted to 3°C below that which was to be used in the polymerisation Hydrogen was added to the autoclave, if required, at this point Ethylene and hexene were then added The catalyst was injected in the reactor at this steady state condition The pressure of the reactor normally increases by 0 3 bar during the injection After the catalyst has been added, the reactor temperature was raised to the reaction temperature. The catalyst was tested for intervals between 30 minutes and 2 hours

During the test ethylene was fed at the reo ired rate to keep the total pressure of the autoclave constant whilst any hexene- 1 comonomer or hydrogen addition was at a rate so as to keep the hexene- 1 /ethylene and hydrogen/ethylene -ratios constant The ratio were measured by the use of on line mass spectral analysis of the gaseous reactor contents

The reaction was terminated by venting off the reactant vapour, purging the autoclave with nitrogen and lowering the temperature of 40°C. The polymer was washed with water, to remove the salt, and then acidified methanol (50ml concentrated HCI) and finally ethanol/water ( 1 4 v/v). The washed polymer was dried in vaccuo at 40°C Results:

TABLE 2

The invention is further illustrated by the preparation of a mulisite catalyst prepared by combining a complex according to the present invention with a conventional Ziegler catalyst Example 9

[COT" - SιMe2 Cp] ZrCl (37 mg) was dissolved in toluene and added to Witco MAO solution in toluene (4 9 ml, 2 13M) This solution was added to I 80g of a silica supported catalyst prepared as follows.

ES70 silica was slurried in hexane and hexamethyldisilazane (0.8mM g Si02) added with stirring Dibutylmagnesium ( 1 5 mM/g Si02) was then added followed by t-butyl chloride (3mM/g Si02). Finally an equimolar mixture of titanium tetrachloride and titanium tetra-n-butoxide (0 1 + 0 15 mM/g Si02) were added before the slurry was dried under a flowing N2 stream.

The mixture of the supported catalyst and the [COT" - SiMe2 Cp] ZrCl]/MAO solution was stirred for I hour at room temperature before the toluene was removed under vacuum, the nominal composition of the catalyst was 1.03% w/w TiO.28% w/w Zr with an Al/Zr ratio of 140/ 1