ORGANOMETALLIC COMPLEXES HAVING OXOBENZOYL LIGANDS
This application claims priority on Provisional Application Serial No. 60/007,321 filed on November 6, 1995.
Field of the Invention
The present invention relates to an organometallic complex having didentate alkoxo ligands that is useful as a catalyst in the polymerization of olefins. The present invention is also directed to a method for preparing the organometallic complex and the use thereof as a catalyst in the polymerization of olefins.
Background of the Invention
The Lewis acidity of early transition metals having high oxidation states and the coordinative unsaturation of transition metal complexes, as well as structural rigidity of the complex, are important characteristics of many catalytically active complexes.
Further, the "sites" of coordinate unsaturation
(two reducible ligands or vacant coordination sites) must be in a cis-position to one another around the transition metal ion to obtain the insertion step that is required in many transition metal catalyzed reactions .
Therefore, an objective of the present invention is to synthesize coordinatively unsaturated organometallic complexes of Group IV metals with few or no d orbital electrons, since this characteristic is necessary to facilitate metal-centered reactivity in olefin polymerization, and where the halide ligands of a metal halide are replaced with di- or higher dentate alkoxo ligands so that the remaining halide ligands of the complex are in a cis-position to one another.
Summary of the Invention
An object of the present invention is to provide a novel Group IV metal complex of didentate alkoxo ligands .
A further object of the present invention is to provide a novel Group IV metal complex of oxobenzoyl ligands .
An object of the present invention is to further provide a novel Group IV metal complex of oxo-cbutyl- methylbenzoyl ligands. Another object of the present invention is to provide a method for preparing the novel Group IV metal complexes .
Another objective of the present invention is to provide a method of using the novel complexes as a catalyst in the polymerization of olefins.
Detailed Description
The inventors have found that a Group IV metal complex of didentate alkoxo ligands having the formula (I)
X4-nMYn (I)
wherein Y represents a didentate alkoxo ligand; M representε a Group IV metal; X represents a halogen, an alkoxy group or an
alkyl group; and n represents an -integer of 1- 2 can be used as a catalyst in the polymerization of olefins. The didentate alkoxo ligand Y is any oxobenzoyl ligand, and is preferably a ligand derived from a salicylaldehyde precursor or a derivative thereof, wherein the phenyl and carbonyl moieties of the salicylaldehyde precursor may be substituted with one or more straight, branched or cyclic hydrocarbon or aromatic having 1 to 20 carbon atoms, which may be the same or different, and the subtituents on the phenyl group may be at the ortho and para positions relative to the hydroxy moiety of the salicylaldehyde precursor. The Group IV metal of the complex is any Group IV metal, such as titanium, zirconium or hafnium. Preferably the Group IV metal is titanium or zirconium. X is any halogen group, such as fluorine, chlorine, bromine or iodine, an alkoxy group having 1 to 4 carbon atoms, or a straight or branched alkyl having 1 to 7 carbon atoms. Preferably X represents a chlorine atom.
The Group IV metal complex may have one or two didentate alkoxo ligands Y in the complex. Preferably the Group IV metal complex has two didentate alkoxo ligands Y therein when M represents titanium, and one or two didentate alkoxo ligands Y therein when represents zirconium. When there is only one didentate alkoxo ligand attached to the zirconium complex, a solvent molecule, such as tetrahydrofuran, may be weakly coordinated thereto since deprotonation of the ligand occurs in the solvent . The solvent molecule does not affect the molar ratios of other ligands or the polymerization property of the complex. The halide ligands of the complexes are in the cis-position, and one oxygen atom of the didentate alkoxo ligand is coordinated anionically to the Group IV metal and another oxygen atom through a lone electron pair.
54 PC17FI96/00592
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The Group IV metal complex of the present invention is prepared by first reacting a didentate alkoxo ligand precursor that is dissolved in a solvent, such as diethylether or tetrahydrofuran, with an alkali metal source, such as n-butyl lithium or metallic sodium, to obtain a alkali metallated didentate alkoxo ligand precursor. For example, if n-butyl lithium is used as the alkali metal, the n-butyl lithium is added to a solution of the didentate alkoxo ligand precursor and solvent at about -78°C, and warmed to about room temperature and stirred for 2-3 hours. The solvent is the evaporated and the alkali metallated didentate alkoxo ligand precursor obtained therefrom. If metallic sodium is used as the alkali metal, the didentate alkoxo ligand precursor may be added in solid form to a mixture of metallic sodium and a solvent, such as tetrahydrofuran, which is refluxed for 2-6 hours until there is no metallic sodium in the mixture. Thereafter, the solvent is evaporated and the alkali metallated didentate alkoxo ligand precursor obtained therefrom.
The alkali metallated didentate alkoxo ligand precursor is then dissolved in a solvent, such as toluene or dichloromethane, and cooled to about -78°C.
A solid Group IV metal halide compound, such as titanium tetrachloride, titanium tetrabromide, titanium tetrafluoride, zirconium tetrachloride, zirconium tetrabromide or zirconium tetrafluoride may be added to the solution of alkali metallated didentate alkoxo ligand precursor, or the Group IV metal halide compound may be dissolved in a solvent, such as toluene or dichloromethane, cooled to -78°C and added dropwise to the solution of alkali metallated didentate alkoxo ligand precursor, to obtain a reaction mixture that is then warmed to about room temperature to 25°C and allowed to react for two to three hours, whereby the halide from the metal tetrahalide compound is displaced by the didentate alkoxo ligand from the alkali
metallated didentate alkoxo ligand precursor. The alkali metal halide is removed from the reaction mixture and the solvent is evaporated. The resultant solid is dissolved in a solvent, such as toluene, and the Group IV metal complex of the present invention is crystallized from the solution by the diffusion method at about -20°C or by adding 16 to 100 cm3 pentane to the solution of product.
The molar ratio of the didentate alkoxo ligand precursor to alkali metal used to obtain the alkali metallated didentate alkoxo ligand precursor is about 1:1-1.5, and is preferably about 1:1.
The molar ratio of the alkali metallated didentate alkoxo ligand precursor to the Group IV metal halide compound is about 1-2:1. Preferably the molar ratio is about 1:1 when M represents titanium, and about 1:1 when zirconium is used as the Group IV metal to obtain a complex having one didentate alkoxo ligand or 2:1 when zirconium is used as the Group IV metal to obtain a complex having two didentate alkoxo ligands. The same titanium complex is obtained when the molar ratio of the alkali metallated didentate alkoxo ligand precursor to titanium is 2:1 and 1:1.
The amount of solvent used to dissolve the metallated didentate alkoxo ligand precursor may be about 100 cm3- Preferably the amount of solvent used should dissolve the alkali metallated didentate alkoxo ligand precursor.
The novel Group IV metal complex of didentate alkoxo ligands of the present invention may be used to polymerize or copolymerize olefin monomers, such as ethylene, propene and hexene in the presence of an aluminum cocatalyst, such as methylaluminumoxane . The amount of Group IV metal in the complex required for olefin polymerization is from 1 to 100 μmol; while the molar ratio of aluminum in the cocatalyst to Group IV metal in the complex is from about 25 to 5,000, and is
preferably about 1,000, for example, when" the Group IV metal is zirconium. The partial pressure of olefin monomer is from about 1 to 50 bar, and the polymerization temperature ranges from about 0 to 150°C. Pentane, isobutane, propane, heptane and toluene may be used as the polymerization solvent. The activity of the Group IV complex ranges from about 8 to 800 kg polyolefin per gram Group IV metal per hour, depending upon the polymerization conditions. The weight average molecular weight and molecular weight distribution of the polyolefin can be controlled by varying the process conditions, and ranges from about 600,000 to 1,500,000 and preferably from about 1,000,000 to 1,200,000 and about 10-20 and preferably from about 14-17, respectively.
Examples of the Group IV metal complex of the present invention are cis-dichloro-bis (3-oxo-4-tbutyl-6- methylbenzoyl) titanium(IV) , cis-dichloro-bis (3-oxo-4- •^butyl-e-methylbenzoyl) zirconium(IV) and -ner-trichloro- (3-oxo-4-tbutyl-6-methylbenzoyl) (tetrahydrofuran) zirconium(IV) , which are represented by Figures 1-3 attached hereto and described below.
Synthesis of cis-dichloro-bis (3-oxo-4-
tbutyl-6- methylbenzoyl) titanium(IV)
methylbenzaldehyde was metallated with 0.48 g (0.0208 mol) of sodium. The resultant yellow solid was dissolved in 100 cm
3 CH
2C1
2, cooled to -78°C and added dropwise to a stirred and cooled (-78°C) solution of 1.2 cm
3 (0.0104 mol) TiCl
4 and CH
2C1
2. A deep red mixture was obtained and warmed slowly to room temperature (@ 25°C) and was then stirred over night . The reaction mixture was filtered through Celite to remove NaCl . The dichloromethane was then evaporated and the deep red crude product was dissolved in toluene. The product was filtered again. A part of the product was crystallized
by the diffusion method and the rest of the product was crystallized by adding pentane to the toluene solution of the product (1:6) . The resultant deep red solid was recrystallized twice from pentane-toluene solution. The yield of crystalline cis-dichloro-bis(3-oxo-4-
tbutyl-6- methylbenzoyl) titanium(IV) was 3.5g (68%) .
The deep red crystalline cis-dichloro-bis (3-oxo-4- 'butyl-e-methylbenzoyl) titanium(IV) complex is relatively sensitive in air. However, observable decomposition did not occur for several hours after exposure to air. The deep red crystalline complex decomposed immediately in moist solvents, and is readily soluble in ethers and chlorinated solvents and soluble in aromatics. The resultant complex is insoluble in alkanes. The complex is a deep red crystalline solid at room temperature.
Synthesis of cis-dichloro-bis (3-oxo-4-tbutyl-6- methylbenzoyl) zirconium(IV)
3 g (0.016 mol) of 3-hydroxy-4-tbutyl-6- methylbenzaldehyde was metallated with 10 cm3 (0.016 mol) n-butyl lithium. The resultant pale yellow solid was dissolved in dichloromethane and cooled to -20°C. This solution was added to a stirred and cooled (-20°C) suspension of 1.9 g (0.008 mol) ZrCl4 and dichloromethane. The reaction mixture was allowed to warm to room temperature (@ 25°C) and was stirred over night. The mixture was then filtered through Celite to remove LiCl. The solvent was evaporated. The crude product was dissolved in toluene and filtered again. The volume of toluene was reduced to 1/3 and the product was crystallized at -20°C. Pale yellow crystals were obtained. The product was recrystallized once from toluene-dichloromethane (6:1) . Yield: 3.1 g (70%) .
The pale yellow crystalline cis-dichloro-bis (3-oxo- 4-''butyl-ό-methylbenzoyl) zirconium(IV) complex is relatively sensitive in air. However, observable
decomposition did not occur for several- hours after exposure to air. The pale yellow crystalline complex decomposed immediately in moist solvents, and is readily soluble in ethers and chlorinated solvents and soluble in aromatics. The resultant complex is insoluble in alkanes. The complex is a pale yellow crystalline solid at room temperature.
Synthesis of mer-trichloro (3 -oxo-4-tbutyl-6- me hylbenzoyl) (tetrahydrofuran) zirconium(IV) 5.0 g (0.026 mol) of 3-hydroxy-4-cbutyl-6- methylbenzaldehyde was alkalimetallated with 0.6 g
(0.026 mol) of sodium. The resultant yellow solid was dissolved in dichloromethane and cooled to -78°C. 6.0 g ZrCl4 (0.027 mol) was added to the solution in solid form. The reaction mixture was allowed to warm to room temperature and was stirred over night. The solution was then filtered through Celite. The volume of solvent was reduced to 1/3 and the product was crystallized at -20°C. The yield of the complex was 11.1 g (75%) . Theyellowcrystallinemer- richloro(3-oxo-4-cbutyl- 6-methylbenzoyl) (tetrahydrofuran) zirconium(IV) complex is relatively sensitive in air. However, observable decomposition did not occur for several hours after exposure to air. The yellow crystalline complex hydrolyzed immediately in moist solvents, and is readily soluble in ethers and chlorinated solvents and soluble in aromatics. The resultant complex is insoluble in alkanes. The complex is a yellow crystalline solid at room temperature.
Polymerization of Olefins
The reactivities of the cis-dichloro-bis (3-oxo-4- fcbutyl-6-methylbenzoyl) titanium(IV) , cis-dichloro-bis (3- oxo-4-tbutyl-6-methylbenzoyl) zirconium(IV) and mer- trichloro (3-oxo-4-""butyl-6-methylbenzoyl) (tetra-
hydrofuran) zirconium(IV) complexes were -evaluated in ethylene polymerization.
The polymerizations was performed in a 2 dm3 autoclave reaction (Buchi) . Pentane was charged under a nitrogen atmosphere into the evacuated autoclave at room temperature. A toluene solution of the Group IV metal complex of the present invention and methylaluminumoxane was mixed in a catalyst cylinder and introduced to the reactor. The temperature was raised to 80°C and ethylene (and comonomer) was fed to the reactor. The process was stopped by cooling and degassing the reaction. Polymerization conditions: partial pressure of ethylene: 10 bar; temperature: 80°C; solvent medium: pentane.
Run 1
5 mg cis-dichloro-bis ( 3 -oxo-4 -cbutyl -6 - methylbenzoyl) zirconium(IV)
5.75 mi 10% methylaluminumoxane Al/Zr=1000
10 bar partial pressure of ethylene 80°C
Runtime: 30 min.
Yield: 6.5 g
Activities: 1444 kg polyethylene/mol Zr h; 2.6 kg polyethylene/g complex h; 15.3 kg polyethylene/g Zr h.
Run 2
5 mg m e r - richloro ( 3 - oxo - 4 -'butyl - 6 - methylbenzoyl) (tetrahydrofuran) zirconium(IV)
5.75 ml 10% methylaluminumoxane Al/Zr=1000 10 bar partial pressure of ethylene 80°C
Runtime : 1 h Yield: 8.0 g
Activities: 727 kg polyethylene/mol Zr h; 1.6 kg polyethylene/g complex h; 8.1 kg polyethylene/g Zr h.
The reactivity of the cis-dichloro-bis (3-oxo-4- fcbutyl-6-methylbenzoyl) titanium(IV) was also evaluated in ethylene-1-hexene copolymerization and was found to have an activity of about 80 kg polyethylene/g Ti h. The comonomer content of the copolymer was about 3 mol% . The titanium and zirconium complexes of the present invention are highly active in the polymerization of ethylene and copolymerization of ethylene and hexene, when methylaluminumoxane is used as a cocatalyst. In general, the titanium complex cis-dichloro-bis (3-oxo-4- ""butyl-6-methylbenzoyl) titanium(IV) is more active than the zirconium complexes in ethylene polymerization, and the rate of copolymerization of ethylene and hexene is slightly slower than the rate of ethylene polymerization using the titanium complex.
The polymerization activity of the Group IV complex can be explained by the cis-configuration of the halide and didentate alkoxo ligands. Specifically, the halide ligand is easily displaced by the alkoxo ligand to provide a suitable reaction site for the ethylene molecule, where the stronger 7r-donating ability of the alkoxo oxygen compared to the halide, together with the chelation of the alkoxo ligand, makes the displacement of the halide markedly favored over the loss of the alkoxo ligand. The chelation of the alkoxo ligand also provide structural rigidity for the complex.
Broad polydispersity values, i.e., broad molecular weight distributions, indicate that the complexes of the present invention have more than one active site, which is surprising since the Group IV metal ion is quite heavily sterically crowded. One possible explanation for the broad polydispersity is that the polymerization temperature causes rearrangement of the didentate alkoxo
ligands that creates several active sites for the complex.