NOVEL TRANSITION METAL COMPLEXES

Abstract: Novel transition metal complexes having pentalene ligands are described. The complexes are suitable for use in the polymerisation of olefins in the presence of suitable activators. Typical complexes are, for example: (I) or (II).

Description: NOVEL TRANSITION METAL COMPLEXES The present invention relates to novel transition metal complexes and in particular to novel transition metal complexes comprising pentalene ligands and to their use as catalyst components for the polymerisation of olefins. The use of metallocene based olefin polymerisation catalysts is now well established. Examples of such catalysts may be found in EP 129368, EP 206794 and EP 260130. Typically the catalyst compositions comprise a metallocene complex for example a bis(cyclopentadienyl) zirconium dichloride together with an activator for example methyl aluminoxane. More recently another type of transition metal complex having a constrained geometry configuration has been used for the polymerisation of olefins. Examples of these complexes may be found in EP 420436 and EP 416815. Such contrained geometry complexes may also be used in the presence of aluminoxanes but may also be used together with boron activators. Another type of transition metal complex suitable for use as a catalyst component is described in EP 672672. The complexes described therein comprise cyclooctatetraene ligands and may also be used for the polymerisation of olefins. The majority of these transition metal complexes comprise at least one cyclopentadienyl ligand together with the transition metal We have now found a novel class of transition metal complex comprising a pentalene ligand which may be used as a catalyst component for the polymerisation of olefins. Thus according to the present invention there is provided a novel transition metal complex having the general formula' LpM Y Xz wherein M is a Group IVA transition metal (Cotton and Wilkinson 2 nα Edition) X is an anionic ligand Y = cyclopentadienyl L is a neutral donor eg THF, amine and L, X or Y may be connected to the pentalene ligand, R is hydrogen, alkyl, aryl, silyl, alkylsilyl or similar and may be the same or different n is 0-6 p = 0 or 1 y = 1 or 2 and when y = 1 , z or x = 0, 1 or 2 when y = 2, z and x = 0. Preferred complexes are those wherein y is 1 , M is zirconium or titanium, X is halogen and Y is cyclopentadienyl. Suitable X ligands include hydride, halogen, alkyl, aryl or oxygen or nitrogen containing ligands. The cyclopentadienyl ligand Y when present may be substituted with alkyl. Alternatively two substituents may be joined together to form a ring eg indenyl. When substituted the pentalene ligand is most suitably substituted in the 1,5- position for example with trimethylsilyl groups. Preferred complexes according to the present invention are represented by the formula: TMS = trimethylsilyl When a X, Y or L group is connected to the pentalene ligand it may be bridged via the group (J 2 Z) n wherein Z is carbon, silicon, germanium or boron and J is hydrogen or hydrocarbyl and n is 1-8. Preferred complexes are: (cyclopentadienyl)[l,5-di(trirnethylsilyl) pentalene] zirconium chloride, (cyclopentadienyl)[l,5-di(trimethylsilyl) pentalene] titanium chloride, (pentamethylcyclopentadienyl)[l,5-di(trimethylsilyl) pentalene] zirconium chloride, bis [l,5-di(isopropylsilyl)pentalene] zirconium. When used as components of catalyst compositions for the polymerisation of olefins the complexes are used in the presence of a suitable activator. Thus according to another aspect of the present invention there is provided a catalyst composition suitable for the polymerisation of olefins comprising: (a) a transition metal complex as described above, and (b) an activator. The preferred activator is an organoaluminium oxy compound for example an aluminoxane. A most preferred activator is methyl aluminoxane. Other activators may also be suitable for use in the catalyst compositions according to the present invention for example boron compounds. Suitable boron activators include tris(pentafluorophenyl) boron or trialkylammonium tetrakis (pentafluorophenyl) borates or N,N-dialkylanilinium tetrakis (pentafluorophenyl) borates. The molar ratio of transition metal to activator is in the range 1 :0.1 to 1 : 10,000 and most preferably in the range 1 : 1 to 1 :2,000. The catalyst compositions according to the present invention may also be used in the supported form. Typical supports include inorganic oxides for example silica, alumina. Other supports include magnesium chloride or polyethylene. When supported the catalyst composition may be prepared by conventional means. The novel transition metal complexes according to the present invention may be prepared for example from cyclooctatetraene. Full experimental details of the preparation are given in the accompanying examples. The present invention also provides a process for the production of polyolefins, in particular homopolymers of ethylene and copolymers of ethylene with minor amounts of at least one C3 to CIO, preferably C3 to C8 alpha-olefin. The process comprises contacting the monomer or monomers, optionally in the presence of hydrogen, with the catalyst composition according to the invention at a temperature and pressure sufficient to initiate the polymerisation reaction. Suitably the alpha olefin may be propylene, butene-1, hexene-1, 4-methyl pentene-1 and octene-1. The olefin polymerisation catalyst compositions according to the present invention may be used to produce polymers using solution polymerisation, slurry polymerisation or gas phase polymerisation techniques. Methods and apparatus for effecting such polymerisation reactions are well known and described in, for example, Encyclopaedia of Polymer Science and Engineering published by John Wiley and Sons, 1987, Volume 7, pages 480 to 488 and 1988, Volume 12, pages 504 to 541. The catalysts of the present invention are particularly suitable for use in the gas phase. The catalyst according to the present invention can be used in similar amounts and under similar conditions to known olefin polymerisation catalysts. The polymerisation may optionally be carried out in the presence of hydrogen. Hydrogen or other suitable chain transfer agents may be used to control the molecular weight of the produced polyolefin. The present invention will now be further illustrated by reference to the following examples. Example 1 Synthesis of K,rCκH 4 f Si'Pr^-l.S^l (a) Cyclooctatetraene (11.3 gm, 0.108 mol) in a slow stream (1.5 cm 3 min "1 at STP) of dinitrogen was passed through a quartz tube at 615 ± 1°C under a controlled dynamic vacuum of 1.0 ± 0.05 mbar over a period of 24 hours in a FVP apparatus; the resultant mixture of dihydropentalenes was collected in a trap at - 78°C. The latter was then dissolved in precooled (-78°C) hexane (100 cm 3 ) and dimethyl ether (DME) (23 cm 3 , 0.22 mol) added, followed by LiBu" (2.5M in hexanes, 88 cm 3 , 0.22 mol) dropwise with stirring, which resulted in the precipitation of white [Li(DME)] 2 [C 8 H 6 ]. After warm up to room temperature, the latter was isolated by filtration on a frit, washed with hexane (3 x 50 cm 3 ), and dried under vacuum. Yield 27.8 gm, 87% based on cyclooctatetraene. (b) To a stirred solution of [Li(DME)] 2 [C 8 H 6 ] (2.95 gm, 10 mmol) in THF (100 cm 3 ) at -78°C was added tri(isopropylsilyl) triflate (6.12 gm, 20 mmol) dropwise; the mixture was then allowed to warm to 0°C and the solvent removed in vacuo at this temperature. The resultant white solids were extracted with pentane (3 x 100 cm 3 ), filtered and the pale yellow filtrates concentrated and cooled to -40°C to afford white crystals of [C 8 H 6 Si i Pr 3 -l,5) 2 ], These were collected and washed with pentene (2 x 10 cιτr) at -78°C. Total yield (two crops) 3.2 gm, 77%. (c) To a stirred, solid mixture of [CgH 6 (Si'Pr 3 -l ,5) 2 ] (2.08 gm, 5 mmol) and [KMe] (0.54 gm, 10 mmol) in a -78°C bath was added diethyl ether, precooled to - 78°C, and the mixture allowed to warm to room temperature overnight. The orange solution was then filtered from small amounts of insoluble material and evaporated to dryness in vacuo to afford off-white K 2 [C 8 H (Si'Pr 3 -l,5) 2 ] in essentially quantitative yield. Example 2 ZrCl 4 and K 2 [C H 4 (Si'Pr 3 -l,5) 2 ] prepared in Example 1 were reacted in Et 2 O overnight and then pumped to dryness followed by extraction with pentane, filtered, concentrated and cooled to -40°C to give orange crystals. Mass spectroscopy indicated [Zr{C 8 H4(Si'Pr -l,5) 2 }2]; and nmr indicated a mixture of isomers. Example 3 Polymerisation Ethylene was polymerised in toluene at 10 bar and at room temperature in the presence of an aliquot (20 mg) of [Zr{C 8 H 4 (Si'Pr 3 -l,5) 2 } 2 ] prepared in Example 2 and 1000 equivalents of methyl aluminoxane. The reaction proceeded exothermically (up to 50°C) and 2.5 gm polyethylene were produced after 1 hr. Example 4 Preparation of complexes used in Examples 5-17 (a) Cp*Zr(pent")Cl Li2pent" (0.70g, 2.69 mmol) was added to Cp*ZrCl3 (0.895g, 2.69 mmol) suspended in cold toluene (40ml, -80 degC). The mixture was allowed to warm up to room temperature and then stirred overnight. The solvent was removed in vacuo and the residue extracted with pentane (100 + 30 ml). Concentration of the resulting clear yellow solution and standing overnight resulted in yellow prisms of the product which were isolated by decantation and washed (2 times 10 ml cold pentane (-40 deg C)) and dried in vacuo. Yield 0.41 g, 30% (b) CpZr(pent")Cl was prepared in a similar way using CpZrC as a starting material. (c) CpTi(pent")Cl Cp2TiC12 (0.41g, 1.65 mmol) was mixed with Zn dust (0.107g, 1.65 mmol) and THF (30 ml) added. The solution was stirred for 3 hr, during which time it turned dark green. This was cooled (-80 deg C) and K2pent" (0.53g, 1.65 mmol) added dropwise as a solution in THF (30 ml). The mixture was allowed to warm up to room temperature and stirred overnight to give a purple solution. The solvent was removed in vacuo and the product extracted with pentane. The resulting purple oil was sublimed (80 deg 1 * 10-5 mbar). The oil was dissolved in pentane and 1 equiv of , C1CH2CH2C1 added. The solution immediately turned deep red and was stirred overnight. The solvent was removed in vacuo and the resulting material sublimed (130 deg 1 *10-5 mbar) to yield CpTi(pent")Cl as a red oil. Yield 0.26g, 0.66 mmol 40%. NB. Cp* = (pentamethyl)cyclopentadienyl; pent" = l,5-di(trimethylsilyl) pentalene. Example 5 Pentalene(TMS)2cyclopentadienyl titanium chloride co-impregnated with MAO on ES70X silica Silica (0.477g, Crosfield ES70, calcined at 700°C under flowing N 2 ) was placed in a Schlenk tube. To this was added a solution of MAO (2.3ml of 1.78M MAO in toluene) and Pentalene(TMS) 2 cyclopentadienyl zirconium chloride (8.5mg). The slurry was allowed to stand with occassional shaking for 90 minutes at room temperature. The catalyst was dried under vacuum at room temperature. Example 6 Pentalene(TMS)?cvclopentadienyl zirconium chloride co-impregnated with MAO on ES70X silica Silica (lg, Crosfield ES70, calcined at 700°C under flowing N 2 ) was placed in a Schlenk tube. To this was added a solution of MAO (5.7ml of 1.5M MAO in toluene) and Pentalene(TMS) 2 cyclopentadienyl zirconium chloride (20mg) in toluene (10ml). The slurry was allowed to stand with occassional shaking for 90 minutes at room temperature. The catalyst was dried under vacuum at room temperature. Polymerisations The reagents used in the polymerisations were Ethylene Grade 3.5 (Supplied by Air Products), 1-hexene (Supplied by Aldrich) distilled over sodium/nitrogen, trimethylaluminium (2M in hexanes, Supplied by Aldrich) and triisobutylauminium (1M in hexanes, Supplied by Aldrich). Example 7 Pentalene(TMS)2Cyclopentadienyl titanium chloride co-impregnated with MAO on ES70X silica Gas Phase, Copolymerisation A 3 litre reactor was heated under flowing nitrogen for 1 hour at 77°C before sodium chloride (300g, predried under vacuum, 160°C, >4 hours) was added. Trimethyl aluminium (3ml, 2M in hexanes) was added to the reactor and allowed to scavenge the reactor of poisons for Vτ hour. After this period of time the alkyl aluminium was vented from the reactor using 4*4 bar nitrogen purges. The gas phase was composed with 0.1 bar 1-hexene and 8 bar ethylene at 77°C prior to catalyst injection. After the catalyst (0.203g) prepared in Example 5 had been injected, under nitrogen the temperature was adjusted to 80°C. The ratio of hexene to ethylene during the polymerisation was keep constant by monitoring the gas phase composition by mass spectrometer and adjusting the flow rate of 1- hexene as required via a HPLC pump. The polymerisation was allowed to continue for 1 hour before being terminated by purging the reactants from the reactor with nitrogen and reducing the temperature to < 30°C. The polymer was washed with water to remove the sodium chloride, then with acidified methanol (50ml HC1/2.5L methanol) and finally with water/ethanol (4: 1 v/v). The polymer was dried under vacuum, at 40°C, for 16 hours. The weight of polymer was 0.6g Example 8 Pentalene(TMS)?cvclopentadienyl zirconium chloride co-impregnated with MAO on ES70X silicaGas Phase, Copolymerisation A 3 litre reactor was heated under flowing nitrogen for 1 hour at 78°C before sodium chloride (300g, predried under vacuum, 160°C, >4 hours) was added. Trimethyl aluminium (3ml, 2M in hexanes) was added to the reactor and allowed to scavenge the reactor of poisons for 1 ' _ hours. After this period of time the alkyl aluminium was vented from the reactor using 4*4 bar nitrogen purges. The gas phase was composed with 0.1 bar 1 -hexene and 8 bar ethylene at 78°C prior to catalyst injection. After the catalyst (0.23g) prepared in Example 6 had been injected, under nitrogen the temperature was adjusted to 80°C. The ratio of hexene to ethylene during the polymerisation was keep constant by monitoring the gas phase composition by mass spectrometer and adjusting the flow rate of 1- hexene as required via a HPLC pump. The polymerisation was allowed to continue for 1 hour before being terminated by purging the reactants from the reactor with nitrogen and reducing the temperature to < 30°C. The polymer was washed with water to remove the sodium chloride, then with acidified methanol (50ml HC1/2 5L methanol) and finally with water/ethanol (4: 1 v/v). The polymer was dried under vacuum, at 40°C, for 16 hours. The weight of polymer was 9.4g Example 9 Pentalene(TMS ?cyclopentadienyl zirconium chloride co-impregnated with MAO on ES70X silica Gas Phase, Copolymerisation A 3 litre reactor was heated under flowing nitrogen for 1 hour at 78°C before sodium chloride (300g, predried under vacuum, 160°C, >4 hours) was added. Trimethyl aluminium (4ml, 2M in hexanes) was added to the reactor and allowed to scavenge the reactor of poisons for lhour. After this period of time the alkyl aluminium was Vented from the reactor using 4*4 bar nitrogen purges. The reactor was cooled to below 30°C and trimethyl aluminium (2ml of 2M in hexanes) was added to the reactor. The reactor was heated to 78°C and the gas phase composed 0.1 bar 1 -hexene and 8 bar ethylene at 78°C prior to catalyst injection. After the catalyst (0.173g) prepared in Example 6 had been injected, under nitrogen the temperature was adjusted to 80°C. The ratio of hexene to ethylene during the polymerisation was keep constant by monitoring the gas phase composition by mass spectrometer and adjusting the flow rate of 1 -hexene as required via a HPLC pump. The polymerisation was allowed to continue for 1 hour before being terminated by purging the reactants from the reactor with nitrogen and reducing the temperature to < 30°C. The polymer was washed with water to remove the sodium chloride, then with acidified methanol (50ml HC1/2.5L methanol) and finally with water/ethanol (4: 1 v/v). The polymer was dried under vacuum, at 40°C, for 16 hours. The weight of polymer was 6.2g Example 10 Pentalene(ΥMSV2cyclopentadienyl zirconium chloride co-impregnated with MAO on ES70X silica Gas Phase, Copolymerisation, TiBA present A 3 litre reactor was heated under flowing nitrogen for 1 hour at 78°C before sodium chloride (300g, predried under vacuum, 160°C, >4 hours) was added. Trimethyl aluminium (4ml, 2M in hexanes) was added to the reactor and allowed to scavenge the reactor of poisons for lhour. After this period of time the alkyl aluminium was vented from the reactor using 4*4 bar nitrogen purges. The reactor was cooled to below 30°C and triisobutyl aluminium (2ml of 1M in hexanes) was added to the reactor. The reactor was heated to 78°C and the gas phase composed 0.1 bar 1 -hexene and 8 bar ethylene at 78°C prior to catalyst injection. After the catalyst (0.220g) prepared in Example 6 had been injected, under nitrogen the temperature was adjusted to 80°C. The ratio of hexene to ethylene during the polymerisation was keep constant by monitoring the gas phase composition by mass spectrometer and adjusting the flow rate of 1 -hexene as required via a HPLC pump. The polymerisation was allowed to continue for 1 hour before being terminated by purging the reactants from the reactor with nitrogen and reducing the temperature to < 30°C. The polymer was washed with water to remove the sodium chloride, then with acidified methanol (50ml HC1/2.5L methanol) and finally with water/ethanol (4: 1 v/v). The polymer was dried under vacuum, at 40°C, for 16 hours. The weight of polymer was 7.3g Examples 11-17 Polymerisations Examples 11-17 were carried out in a 1 litre capacity autoclave using isobutane as the reaction medium. The reactor was heated to 85°C and thoroughly purged with nitrogen (2l/min) for 90 min. The temperature was then reduced to 50°C and the reactor charged with the chosen alkylaluminium scavenger and isobutane (500ml). The mixture was stirred (200rpm) at 75°C for a minimum of 120 min, the temperature was varied to the subsequent polymerisation temperature (T) and 10 bar overpressure of ethylene was then added. The metal complex (see belov ) and MAO were mixed together and then added to the reactor. Ethylene was added to maintain constant reactor pressure for the duration of the run. The run was terminated by rapidly venting the reactor and cooling to 20°C. Solid polymer product was washed with methanolic hydrogen chloride, rinsed with aqueous ethanol and dried (50°C, in vacuo, 16h). Details of the complexes and ds used are given in Table 1. The metal complexes were (cyclopentadienyl) (1,5 -d i(trimethylsilyl) pentalene) zirconium chloride or the titanium analogue or (pentamethyl cyclopentadienyl) zirconium (l,5-di(trimethylsilyl) pentalene) zirconium chloride. TABLE 1 i The comonomer incorporation (Example 15) xvas determined by 13C-NMR with 3.1Butyl branches per 1000 Carbon atoms. Cp* = (pentamcthvl) cyclopentadienyl ** = I-hcxene Mn = molecular weight PD = polydispersity

Claims: Claims: 1. A transition metal complex having the general formula: LpM Yx Xz wherein M is a Group IVA transition metal (Cotton and Wilkinson 2 ,n n d α Edition) X is an anionic ligand Y = cyclopentadienyl L is a neutral donor eg THF, amine and L, X or Y may be connected to the pentalene ligand, R is hydrogen, alkyl, aryl, silyl, alkylsilyl or similar and may be the same or different n is 0-6 p = 0 or 1 y = 1 or 2 and when y = 1, z or x = 0, 1 or 2 when y = 2, z and x = 0. 2. A complex according to claim 1 wherein y is 1, M is zirconium or titanium, X is halogen and Y is cyclopentadienyl. 3. A complex according to claim 1 chosen from the group (cyclopentadienyl)[l,5-di(trimethylsilyl) pentalene] zirconium chloride, (cyclopentadienyl)[l,5-di(trimethylsilyl) pentalene] titanium chloride, (pentamethylcyclopentadienyl)[l,5-di(trimethylsilyl) pentalene] zirconium chloride, or bis [l,5-di(isopropylsilyl)pentalene] zirconium. 4. A catalyst composition suitable for the polymerisation of olefins comprising: (a) a transition metal complex having the formula: LpM Yx Xz wherein M is a Group IVA transition metal (Cotton and Wilkinson 2n n d α Edition) X is an anionic ligand Y = cyclopentadienyl L is a neutral donor eg THF, amine and L, X or Y may be connected to the pentalene ligand, R is hydrogen, alkyl, aryl, silyl, alkylsilyl or similar and may be the same or different n is 0-6 p = 0 or 1 y == 1 or 2 and when y = 1, z or x = 0, 1 or 2 when y = 2, z and x = 0, and (b) an activator. 5. A catalyst composition according to claim 4 wherein the activator is an aluminoxane. 6. A catalyst composition according to claim 4 wherein the activator is tris(pentaflurophenyl) boron, a trialkylammonium tetrakis(pentafluorophenyl) borate or a N,N-dialkylanilinium tetrakis (pentafluorophenyl) borate. 7. A catalyst composition according to claim 6 wherein the molar ratio of transition metal to activator is in the range 1 :0.1 to 1 : 10,000. 8. A catalyst composition according to claim 7 wherein the molar ratio of transition metal to activator is in the range 1 : 1 to 1 :2,000. 9. A catalyst composition according to claims 4-8 also comprising a support. 10. A catalyst composition according to claim 9 wherein the support is silica. 11. A process for preparing homopolymer of ethylene or copolymers of ethylene and alpha-olefins comprising performing the polymerisation in the presence of a catalyst composition according to claims 4-10. 12. A process according to claim 1 1 carried out in the gas phase.

Inventors: CLOKE FREDERICK GEOFFREY NETHE, PARRY JULIAN STEPHEN, CLOKE, FREDERICK, GEOFFREY, NETHERSOLE, PARRY, JULIAN, STEPHEN
Applicants: BP CHEM INT LTD, CLOKE FREDERICK GEOFFREY NETHE, PARRY JULIAN STEPHEN, BP CHEMICALS LIMITED, CLOKE, FREDERICK, GEOFFREY, NETHERSOLE, PARRY, JULIAN, STEPHEN
Application year: 1998
Main classification: C07F17
IPC codes: C07F17, C08F4, C08F10, C08F110