KR0164286B1 - Process for preparing metalloceme catalyst for polymerizing olefin - Google Patents

Abstract

The present invention relates to a method for producing a metallocene catalyst for olefin polymerization.

More specifically, the present invention relates to a process capable of producing a high activity neutral group and cationic form Group 4 metal metallocene catalyst for olefin synthesis by a simple process. The method for preparing a metallocene catalyst of the present invention comprises the steps of reacting a metal halide compound with 2 to 2.2 equivalents of a lithium compound in the presence of an organic solvent to produce a dialkyl halide compound; Reacting the dialkyl metal halide compound obtained in the above process with a ligand having a double anion to prepare a metallocene catalyst in the form of a cation; And reacting the metallocene catalyst in the cation form obtained in the above process with hydrogen chloride gas or an amine hydrochloride in the presence of an organic solvent to produce the metallocene catalyst in the neutral form. It has been confirmed by the production method of the present invention that the metallocene catalyst in the cation form and the metallocene catalyst in the neutral form, which are useful as catalysts for olefin polymerization, can be produced in a high yield by a simple process.

Description

Method for producing a metallocene catalyst for olefin polymerization.

The present invention relates to a method for producing a metallocene catalyst for olefin polymerization.

More specifically, the present invention relates to a process for producing a high activity neutral group and cationic form Group 4 metal metallocene catalyst for olefin polymerization in a simple process by high yield.

For homogeneous metallocene catalysts used in olefin polymerization, dicyclo-pentadienytitanium dichloride (Cp ₂ TiCl ₂ ) is used as a catalyst for ethylene polymerization by low pressure. Since it has been reported that many researchers have studied metallocene catalysts, which were first described in order to understand the reaction mechanism of catalysts, metallocenes, first published by Kaminsky and Sinn, etc. in 1980, It has been found that when methylaluminoxane (MAO) is used as a catalyst in the catalyst, it exhibits high activity.

Also, in 1985, Kaminsky and Brintzinger rac-ethylenebis (tetrahydroindenyl) zirconium dichloride, a racemic compound having a C ₂ -symmetry, rac-ethylenebis Isotactic PP using the -Et (THI) ₂ ZrCl ₂ ] catalyst and Cs-symmetry by Ewen in 1988, isopropylcyclo Pentadienylfluorenyl Syndiotactic PP was synthesized using a zirconium dichloride, i-Pr (CpFlu) ZrCl ₂ ] catalyst, and a cationic metallocene catalyst without the MAO was foamed by Jordan et al.

The most important feature of the above-described metallocene catalyst is that it is possible to control the physical properties of the olefin polymer through the structure change of the catalyst, the molecular weight distribution of the resulting polymer is narrow and the comonomer composition and distribution of the copolymer during copolymerization Is uniform. In addition, when the above-described metallocene catalyst is used, it exhibits high catalytic activity even for olefins having high steric hindrance, such as higher order α-olefins or cyclic olefins, and polymerization of some polar vinyl monomers is also possible. Done.

In general, the Group 4 metal metallocene catalyst used for the olefin polymerization described above is a neutral type metallocene catalyst of the form R ((CpRn) (CpR'm) MX ₂ which is a bicomponent catalyst using MAO as a promoter. It is classified into a cationic metallocene catalyst of the form R ((CpRn) (CpR'm) MX ₂ which is a single component catalyst that can be used alone for polymerization without the need for a cocatalyst.

It is known that a polymer having high activity and stereoregularity can be prepared when olefin polymerization is carried out using a bicomponent catalyst composed of a neutral metallocene catalyst and a catalyst of MAO among the metallocene catalysts described above. MAO, a co-catalyst for the polymerization of olefins, is used in an amount of about 15000 times that of the Group 4 metallocene catalyst, and the co-catalyst itself is a very expensive compound. there was.

Therefore, a series of attempts have been made to solve the above-mentioned disadvantages of the neutral metallocene catalyst. As part of such an attempt, a cationic group 4 metal metal capable of polymerizing olefins alone without using a co-catalyst MAO is used. Research into making sen has been underway. As a result, in the olefin polymerization, the cationic form of Group 4 metal can be prepared to produce a polymer having almost the same level of activity and stereoregularity as the case of using the medium form Group 4 metallocene and MAO binary catalyst. Rosene catalysts have been developed.

Conventional methods for preparing neutralized metallocene catalysts among the aforementioned metallocene catalysts have been disclosed in the following literatures;

EP 530908A discloses the polymerization of neutral metallocene catalysts and olefins using them.

In addition, several papers by HH Brintzinger, S. Collins, Kaminsky, SL Buchwald, and F. Piemontesi have also prepared neutral metallocene catalysts. A method is disclosed. H. H. Brintzinger, JOMC, 232: 233 (1982); H. H. Brintzinger, JOMC, 322: 65 (1987); S, Collins, JOMC, 342: 21 (1988); S. Collins, Organometallics, 11: 2115 (1992); W, Kaminsky, Angew, Chem, Int, Et. Engl., 24: 507 (1985); S. L. Buchwald, Organometallics, 10: 1501 (1991); F, Piemontesi, Organometallics, 14; 1256 (1995).

In the above-mentioned prior art, the neutral-type Group 4 metallocene catalyst synthesizes ansasa ligand by connecting two ligands of cyclopentadienes to a bridging group as shown in the following scheme. After the anion ligand was double anioned and reacted with a halogenated Group 4 metal compound in the form of MX ₄ , the Group 4 metal metallocene catalyst in the cationic form was a metallocene catalyst in the neutral form. Prepared by alkylation with alkyllithium;

Where

R represents a bridging group,

CpRn and CpR 'm represent ligands,

M represents a Group 4 metal of Ti, Zr or Hf,

X represents Cl or Br, and

RLi represents alkyllithium.

However, the method for preparing the neutral metallocene catalyst has a disadvantage of low reproducibility and low yield among the aforementioned conventional production methods, and the method for preparing the metallocene catalyst in the form of cation is alkylation reaction of the neutral metallocene catalyst. It is not possible to produce cationic metallocene catalysts with high yields due to the deligand reaction of commercially neutralized metallocene catalysts, and a complicated preparation process is required to prepare the desired cationic metallocene catalysts. Therefore, there was a problem that it is not possible to manufacture a metallocene catalyst economically.

Therefore, there has been a constant demand for the development of a process for producing a metallocene catalyst having a neutral form and a cationic form for olefin polymerization in a high yield by a simple process, but there are almost no satisfactory research results. It is true.

After all, the main object of the present invention is to provide a method for producing a cationic metallocene catalyst in a high yield by a simple process.

It is another object of the present invention to provide a method for preparing a neutral form metallocene catalyst in high yield.

Hereinafter, a method for preparing a metallocene catalyst according to the present invention will be described in detail for each process.

Step 1: Preparation of Dialkyl Metal Halide Compound

As in the following Reaction Formula (1), the metal halide compound represented by the following General Formula (I) is reacted with 2 to 2.2 equivalents of the lithium compound represented by the following General Formula (II) in the presence of an organic solvent. To prepare a dialkyl halide metal compound.

Where

M represents a Group 4 metal of Ti, Zr or Hf, or a Group 5 or 6 metal in which the oxidation state is tetravalent, preferably a Group 4 metal of Ti, Zr or Hf;

X represents F, Cl, Br or I, preferably Cl or Br; And,

R * represents a C ₂ -C ₂₀ linear or branched alkyl or aryl group, preferably methyl, n-butyl, t-butyl or phenyl group.

In this case, as the organic solvent, a polar aprotic solvent such as tetrahydrofuran (THF), a hydrocarbon solvent such as toluene, and chloride such as dichloromethane may be used. In addition, it is preferable to use the lithium compound of the general formula (II) as a solution in which alkyllithium or aryllithium is dissolved in a solvent such as diethyl ether, and the reaction is -100 to -20 占 폚, preferably,- Preference is given to performing at low temperatures of 80 to -50 ° C. In addition, since the dialkyl metal halide compound produced in the present step is decomposed by external light or heat, it is preferable to maintain the temperature at -80 to -50 ° C while blocking the light.

Second Step: Preparation of Cationic Metallocene Catalyst

As shown in the following reaction formula (2), the dialkyl halide compound represented by the following general formula (III) prepared in the first step described above is reacted with a ligand having a double anion represented by the following general formula (IV) A metallocene catalyst in the cation form represented by formula (V) is prepared.

Where

R *, M and X are as defined above;

R is C ₁ -C ₁₂ linear or cyclic alkyl, aryl, alkenyl, silialkenyl having 1 to 2 Si, or hetero atoms of Si, Ge, S, O or N, preferably , Ethyl, 2-butenyl, o-xylene or silalkenyl; And CpRn and CpR'm have a substituent of cyclopentadienyl, indenyl, tetrahydroindenyl, or fluorenyl, or a substituent of alkyl, aryl, phosphine, amine, alkylether or arylether to the aforementioned ligand. Or a ligand of two or more substituted ligands, preferably cyclopentadienyl, indenyl, tetrahydroindenyl or fluorenyl.

At this time, the ligand having a double anion represented by the general formula (IV) may be prepared by a conventional manufacturing method, the ligand represented by R (CpRn) (CpR 'm) in the presence of an organic solvent and- It can be prepared by reacting at 78 ℃ to 0 ℃, the lower the reaction temperature is preferable, it is preferable to use an aprotic solvent such as tetrahydrofuran, ether, hexane and toluene as the organic solvent. At this time, the ligand represented by R (CpRn) (CpR 'm) can be prepared by a known production method for linking two ligands including cyclopentadiene [see; S. Collins, Organometallics, 11: 2115 (1992)], wherein the Rn and R'm substituents are independently linear or branched hydrocarbyl groups of 1 to 20 carbon atoms, or are bonded to a cyclopentadiene ring to 4 carbon atoms It is a cyclic hydrocarbylene group having a carbon number capable of forming from six to six bonds.

At this time, examples of the Rn and R'm substituent is a hydrocarbyl group include methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl or phenyl group, Rn And examples of the R'm substituent being a hydrocarbylene group include ethylene, propylene and butylene groups, and preferably, a ring capable of combining with cyclopentadiene to form an indenyl, tetrahydroindenyl or fluorenyl group. Type hydrocarbylene groups can be used. In this production process, a solution in which a ligand having a double anion represented by the general formula (IV) is dissolved in a suspension of the dialkyl halide compound represented by the general formula (III) when preparing a metallocene catalyst in the form of a cation. It is preferable to add little by little, and the reaction temperature is maintained at -80 to 0 ° C, preferably -60 to -10 ° C for activation of the reaction, suppression of side reactions and control of stereospecificity of the product. In addition, as an organic solvent, a polar aprotic solvent such as tetrahydrofuran, a hydrocarbon solvent such as toluene, chloride such as undichloromethane, and the like can be used. Preference is given to using a solvent.

Third Step: Preparation of Neutral Metallocene Catalyst

As shown in the following Reaction Formula (3), the metallocene catalyst of the cationic type represented by the following general formula (V) prepared in the second step described above is represented by hydrogen chloride gas or the following general formula (VI) in the presence of an organic solvent. It is reacted with an amine hydrochloride to prepare a metallocene catalyst of neutral form represented by the following general formula (VII).

Where

R, CpRn, CpR'm M and R * are as defined above; And,

R represents a C ₁ -C ₁₀ alkyl or aryl group, preferably methyl, ethyl, propyl or phenyl group.

In this case, as the organic solvent, polar aprotic solvents such as tetrahydrofuran, hydrocarbon solvents such as toluene and chlorides such as methane dichloride can be used. The organic solvents described above are dehydrated and distilled prior to use. Preference is given to using.

In the above production method, the compound obtained for each fixed is separated and purified according to the methods commonly used in the art, such as distillation, recrystallization and chromatography, depending on the physical properties of each compound, the solvent used for recrystallization Any single or mixed solvent system in which the rosene compound can be dissolved may be used, but a single or mixed polar aprotic solvent such as hydrocarbons such as toluene and hexane, chlorides such as chloroform and methane dichloride or diethyl ether may be used. It is preferable. In addition, the identification of the compound obtained by each process is performed using ¹ H-NMR, a mass spectrometer, etc.

The metallocene catalyst prepared by the present invention is capable of carrying out homopolymerization and copolymerization of linear α-olefins, homogeneity of cyclic olefins and copolymerization of linear α-olefins and cyclic olefins without involving ring opening. In particular, polyethylene, isotactic flopropylene and syndiotactic polypropylene can be polymerized with high activity.

In addition, the production process of the metallocene catalyst is improved not only by the production method of the present invention, but also unlike the conventional production method of preparing a metallocene catalyst in the form of a cationic form through an alkylation reaction, without a cation without undergoing an alkylation reaction. Formation of metallocene catalysts is possible.

Hereinafter, the present invention will be described in more detail with reference to Examples.

These examples are only for illustrating the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples according to the gist of the present invention.

Example 1

Preparation of rac-o-Xyl (Ind) ₂ ZrMe ₂

Dissolve 5 mL of indene in 200 mL of anhydrous tetrahydrofuran, add 29.5 mL (1.1 equiv) of butyllithium (n-BuLi, 1.6 M in hexane) at 78 ° C., and warm the solution to 25 ° C. over 2 hours and 30 minutes. It was changed to red.

After 30 minutes of reaction at 25 ° C, 8.2 mL (1.1 equiv) of hexamethylphosphoamide (HMPA) was added to change the color of the solution to dark reddish brown. After the reactor was cooled to -78 ° C, 5.66 g (0.5 equiv) of α, α'-dibromo-o-xylene was dissolved in 30 mL of anhydrous tetrahydrofuran. The solution was added dropwise for 30 minutes to change the color of the solution to purple, and then the reaction temperature was raised to 25 ° C. for 11 hours. When the reaction was stopped with saturated aqueous ammonium chloride solution, the color of the reaction solution changed to yellow momentarily.

The organic layer was extracted using diethyl ether, washed twice with saturated solution of copper (II) sulfate [copper (II) sulfate], dried over anhydrous magnesium sulfate (magnesiumsulfate) and filtered. The filtrate was concentrated and washed three times with hexane (n-hexane), and then recrystallized with methane dichloride / hexane (CH ₂ Cl ₂ / n-hexane) to give a white solid, bis (indenyl) -o-xylene. 12.9 g of [bis (indenyl) -o-xylene] was obtained. (Yield: 90%)

0.6 g (1.8 mmol) of bis (indenyl-o-xylene) prepared above was dissolved in 40 mL of anhydrous tetrahydrofuran, cooled to -78 ° C, and 2.5 mL (2.2 equivalents) of n-butyllithium (1.6 M in hexane). The reaction mixture was added dropwise to form a light yellow suspension as a ligand having a double anion in light red, and the temperature of the reaction solution was increased to 25 ° C. over 2 hours. In a separate vessel, 0.42 g (1 equivalent) of zirconium chloride (IV) was added in a glove box, and 60 mL of anhydrous tetrahydrofuran was added to dissolve the reaction vessel. The temperature was cooled to -78 ° C, 2.55 mL (2.2 equivalents) of methyllithium (1.5 M in diethylether) was added dropwise, and then reacted at -78 ° C for 30 minutes to prepare dimethyllithium chioride. Bis (indenyl) -o- The double anion of silane was added dropwise over 15 minutes, and the color of the reaction mixture was momentarily changed to dark red The temperature of the reaction vessel was raised to 25 ° C. over 2 hours and then reacted for 13 hours. The filtrate was concentrated and extracted with methane / diethyl ether, and then the filtrate was concentrated and washed with diethyl ethyr (10 mL × 3 times) to dry the white solid, followed by racemic-o-xylenyl-bis (indenyl) zirconium. 0.64 g of a 3: 1 mixture of dimethyl [rac-Xyl (Ind) ₂ ZrMe ₂ ] and meso-o-xylenyl-bis (indenyl) zirconium dimethyl [meso-Xyl (Ind) ₂ ZrMe ₂ ] was obtained (yield) : 78%) The mixture was separated by fractional recrystallization at -20 ° C using a mixed solution of methane dichloride / n-hexane.

rac-Xyl (Ind) ₂ ZrMe ₂

Example 2

Preparation of rac-Xyl (Ind) ₂ ZrMe ₂

0.6 g (1.3 mmol) of rac-Xyl (Ind) ₂ ZrMe ₂ prepared in Example 1 was dissolved in 40 mL tetrahydrofuran, passed through dried hydrogen chloride (HCI) gas for 30 seconds, and the solvent was dried to give a yellow solid. Phosphorus racemic-o-xylenyl-bis (indenyl) zirconium dichloride [rac-Xyl (Ind) ₂ ZrMe ₂ ] compound was prepared.

In addition, meso-o-xylenyl-bis (indenyl) zirconium difluoride from meso-o-Xyl (Ind) ₂ ZrMe ₂ using the same method as the above [meso-o-Xy (Ind) ₂ ZrCl ₂ ) A compound was prepared.

Example 3

Preparation of rac-1,4-Bis (indenyl) -2-buteneZrMe ₂

Cis in the same manner as in Example 1, except that 2.0 mL of indene and 0.9 mL (0.5 equiv) of cis-1,4-dichloro-2-butene were used. 2.10 g of -1,4-bis (indenyl) -2-butene (cis-1,4-bis (indenyl-2-butene) was obtained (yield: 89%)

0.645 g (2.26 mmol) of cis-1,4-dichloro-2-butene prepared above was subjected to double anionization in the same manner as in Example 1 while raising the reaction temperature from -78 ° C to -20 ° C. It was reacted with the dialkyl halide compound in the same manner as in Example 1. After completion of the reaction, the reaction solvent was dried and the reaction residue was washed with anhydrous nucleic acid. The residue was extracted with a mixed solvent of diethyl ether / methane dichloride, then filtered and the solvent was removed and washed with diethyl ether. The obtained white solid was dissolved in this methane chloride, diethyl ether was added and recrystallized to give 0.612 g of cis-1,4-dichloro-2-butene-zirconium dimethyl [1,4-bis (indenyl) -2-buteneZrMe ₂ ]. Was prepared (yield: 67% rac / meso = 2/1) and washed repeatedly with hexane to obtain pure racemic-1,4-bis (indenyl) -2-butene-zirconium dimethyl [1,4-bis ( indenyl) -2-buteneZrMe ₂ ].

Example 4

Preparation of rac-1,4-bis (indenyl) -2-buteneZrCl ₂

1,4-bis (indenyl) -2- was carried out in the same manner as in Example 2, except that the 1,4-bis (indenyl) -2-buteneZrMe ₂ mixture prepared in Example 3 was used. A butene-zirconium dichloride [1,4-bis (indenyl) -2-buteneZrCl ₂ ] mixture was prepared. The mixture was recrystallized using a methane dichloride / ether mixed solvent to give racemic-1,4-bis (indenyl) -2-butene-zirconium dichloride [rac-1,4-bis (indenyl) -2-buteneZrCl ₂ ] compound and meso-1,4-bis (indenyl) -2-butene-zirconium dichloride [meso-1,4-bis (indenyl) -2-buteneZrCl ₂ ] were prepared separately.

rac-1,4-bis (indenyl) -2-buteneZrCl ₂

meso-1,4-bis (indenyl) -2-buteneZrCl ₂

Example 5

Preparation of rac-Et (Ind) ₂ ZrMe ₂

Bis (indenyl) ethane [bis was carried out in the same manner as in Example 1, except that 2.0 mL of indene and 0.73 mL (0.5 equivalent) of 1,2-dibromoethane were used. (indenyl) ethane] 1.382g was prepared (yield: 70%)

0.6 g (2.3 mmol) of bis (indenyl) ethane prepared above was double anionized in the same manner as in Example 1, and then reacted with a dialkyl halide compound in the same manner as in Example 1. After the reaction was completed, the solvent was dried, extracted and filtered with methane dichloride / ether, and then the filtrate was concentrated, washed three times with ether and dried to give ethylene bis (indenyl) zirconium dimethyl white (Et (Ind) ₂ ZrMe). ₂ ] 0.56 g of a mixture was obtained (yield: 66%, rac / meso = 3/1), and the electrical mixture was recrystallized at -20 ° C to obtain pure racemic-ethylenebis (indenyl) zirconium dimethyl [rac-Et (Ind). ) ₂ ZrMe ₂ ] and meso-ethylenebis (indenyl) zirconium dimethyl [meso-Et (Ind) ₂ ZrMe ₂ ].

rac-Et (Ind) ₂ ZrMe ₂

meso-Et (Ind) ₂ ZrMe ₂

Example 6

Preparation of rac-Et (Ind) ₂ ZrCl ₂

The Et (Ind) ₂ ZrMe ₂ mixture prepared in Example 5 was dissolved in tetrahydrofuran and injected with dried HCI gas, and then the solvent was dried to give racemic-ethylenebis (indenyl) zirconium dichloride [rac A mixture of -Et (Ind) ₂ ZrCl ₂ ] and meso-ethylenebis (indenyl) zirconium dichloride [meso-Et (Ind) ₂ ZrCl ₂ ] was prepared. The mixture was recrystallized from a methane dichloride / ether mixed solvent to separately prepare each compound.

rac-Et (Ind) ₂ ZrCl ₂

meso-Et (Ind) ₂ ZrCl ₂

Example 7

Preparation of rac- [Me ₂ Si (Ind) ₂ ZrMe ₂ ]

50 mL of dried tetrahydrofuran was added to a 250 mL Schlenk flask connected with a bubbler, and 2.0 mL (1.72 × 10 ⁻² mol) of indene was injected into the syringe. After the reaction vessel was cooled to -78 ° C, 11.8 mL (1.05 equivalent, 1.53 M in hexane) of butyllithium (n-BuLi) was slowly added dropwise into an orange suspension, which was heated to room temperature for 2 hours. To a solution, 30 mL of tetrahydrofuran was added to a separate 250 mL Schlenk flask and 1.04 mL (0.5 equiv, 0.86 × 10 ⁻² mol) of dichlorodimethylsilane (Me ₂ SiCl ₂ ) was injected, red at room temperature. The double anion solution was slowly added dropwise to the dichlorodimethyl silane solution, reacted for 10 hours, and 50 mL of a saturated ammonium chloride (NH ₄ Cl) solution with distilled water was added to stop the reaction. The reaction solution was extracted with diethyl ether, the extract was dried over anhydrous magnesium sulfate, filtered, and the solvent was removed using a rotary evaporator. Separation by column chromatography using hexane / methane dichloride (30/1, v / v) gave 2.24 g of an isomer mixture of bis (indenyl) dimethylsilane (Me ₂ Si (Ind) ₂ ] (yield: 74%)

0.62 g of a mixture of Me ₂ Si (Ind) ₂ ZrMe ₂ was obtained in the same manner as in Example 1 using 0.52 g (1.82 mmol) of the bisdenyl dimethyl cellulose prepared above (yield: 87.1%, rac / meso = 1/2), the above mixture was fractionated and recrystallized at -20 ° C to prepare rac-Me ₂ Si (Ind) ₂ ZrMe ₂ and meso-Me ₂ Si (Ind) ₂ ZrMe ₂ compounds.

rac-Me ₂ Si (Ind) ₂ ZrMe ₂

meso-Me ₂ Si (Ind) ₂ ZrMe ₂

As described and demonstrated in detail above, it was confirmed that the cationic form metallocene catalyst and the neutral form metallocene catalyst useful as the catalyst for olefin polymerization can be produced in a high yield by a simple process by the preparation method of the present invention. It became.

Claims (1)

(i) The metal halide compound represented by the general formula (I) is reacted with 2 to 2.2 equivalents of the lithium compound represented by the general formula (II) in the presence of an organic solvent, to react with the general formula (III). Preparing a dialkyl metal halide compound represented by; And (ii) reacting the dialkyl halide compound represented by the general formula (III) obtained by electrofixing with a ligand having a double anion represented by the general formula (IV) as shown in the following scheme (2). Method for preparing a metallocene catalyst comprising the step of preparing a metallocene catalyst of the cationic form represented by: Wherein M represents a Group 4 metal of Ti, Zr or Hf, or a Group 5 or 6 metal in which the oxidation state is tetravalent, preferably a Group 4 metal of Ti, Zr or Hf; X represents F, Cl, Br or I, preferably Cl or Br; R * represents a C ₂ -C ₂₀ linear or branched alkyl or aryl group, preferably methyl, n-butyl, t-butyl or phenyl group; R is C ₁ -C ₁ 2 linear or cyclic alkyl, aryl, alkenyl, silyl alkenyl having 1 to 2 Si, or hetero atoms of Si, Ge, S, O or N, preferably ethyl 2-butenyl, o-xylene or silialkenyl; CpRn and CpR'm are ligands of cyclopentadienyl, indenyl, tetrahydroindenyl or fluorenyl, or one or two substituents of alkyl, aryl, phosphine, amine, alkylether or arylether to the aforementioned ligand. Ligands substituted above are preferably ligands of cyclopentadienyl, indenyl, tetrahydroindenyl or fluorenyl.