EP1019421A1

EP1019421A1 - Transition metal compound, a process for its preparation and its use as a catalyst component

Info

Publication number: EP1019421A1
Application number: EP96943384A
Authority: EP
Inventors: Gerhard Edwin Herberich; Bernd Schmidt; Andreas Schmitz; Johannes Antonius Maria Van Beek
Original assignee: DSM NV
Current assignee: Koninklijke DSM NV
Priority date: 1995-12-22
Filing date: 1996-12-20
Publication date: 2000-07-19
Also published as: AU1212697A; DE19549352A1; JP2000502678A; WO1997023493A1

Abstract

The present invention relates to a compound having the formula (I): LnAmMXk, wherein L is a boratabenzene ligand of formula (II), wherein the radicals R are identical or different and are each a hydrogen atom, a C1-C10-group, A is a π-ligand such as cyclopentadienyl, M is a metal of group 3 or 5 of the Periodic System of the Elements and X is a hydrogen atom, a C1-C40-group, an OH group, a halogen atom or NR22, n is 1 or 2, m is 0 or 1 and k is an integer from 1 to 4, where the sum of n+m+k is from 3 to 5. The present invention also relates to a process for preparing the transition metal compound and to its use as a catalyst component during the preparation of polyolefins.

Description

TRANSITION METAL COMPOUND, A PROCESS FOR ITS PREPARATION AND ITS USE AS A CATALYST COMPONENT

The present invention relates to a transition metal compound and a process for its preparation and also to its use as a catalyst component in the preparation of polyolefins.

The literature discloses the preparation of polyolefins using soluble metallocene compounds in combination with aluminoxanes or other cocatalysts which, owing to their Lewis acidity, can convert the neutral transition metal compound into a cation and stabilize it (EP-A-129 368, EP-A-351 392).

Metallocenes and semi-sandwich compounds are of great interest not only for the polyme ization or oligomerization of olefins. They can also be used as hydrogenation, epoxidation, isomerization and C-C coupling catalysts (Chem. Rev. 1992, 92, 965-994).

Of great interest are transition metal compounds which have sufficient activity in respect of the above-described fields of application. It is an object of the present invention to provide a transition metal compound and an economical and environmentally friendly process for its preparation.

This object is achieved by a compound having the formula I

L„A_mMX_k (I),

wherein L is a boratabenzene ligand of the formula II

wherein the radicals R are identical or different and are each a hydrogen atom, a C^-C^-group such as a C_x- C₁₀-alkyl group or a C₆-C₁₀-aryl group and two adjacent radicals R together with the atoms connecting them can form a ring system, and Y is a hydrogen atom, a Ci-CiQ- roup such as a Ci-C₁₀-alkyl group or a C₆-C₁₀-aryl group, a halogen atom, an -NR² ₂ or -PR² ₂ radical, wherein R² is a halogen atom or a Ci-C₁₀-group such as a ^c _ι-C₁₀-alkyl group or a C₆-C₁₀-aryl group, A is a π-ligand such as for instance cyclopentadienyl, which can be either substituted or unsubstituted, and adjacent substituents on the cyclopentadienyl ligand can form a ring, M is a metal of group 3 or 5 of the Periodic System of the Elements and

X is a hydrogen atom, a Ci-C₄₀-group such as a Cι-C₂₀- alkyl group, a Ci-C₁₀-alkoxy group, a C₆-C₂₀-aryl group, a C₂-C₁₂-alkenyl group, a C₇-C₄₀-arylalkyl group, a C₇- C₄₀-alkylaryl group, an OH group, a halogen atom or -NR² ₂, n is 1 or 2, m is 0 or 1 and k is an integer from 1 to 4, where the sum of n+m+k is from 3 to 5. The present invention accordingly provides a transition metal compound which contains as a ligand at least one substituted or unsubstituted boratabenzene group, as is described by formula I.

The Periodic System of the Elements is the Periodic System that can be found on the inside of the cover of the Handbook of Chemistry and Physics, 70th edition, 1989/1990 (new notation).

The ligands A can be chosen from the ligands described above and can be mutual identical or different ligands. The ligands X can be chosen from the groups described above and can be mutual identical or different ligands.

A preferred embodiment of the invention is a compound in which the radicals R are identical and are each a hydrogen atom, a Ci-C -alkyl group or a C₆-C₁₀- aryl group and Y is a Ci-C₄-alkyl group or -NR² ₂, wherein R² is a Ci-C₄-alkyl group.

A preferred embodiment of the invention is a compound in which A is a substituted cyclopentadienyl, indenyl or fluorenyl ligand.

A preferred embodiment of the invention is a compound in which X is -NR² ₂, where R² is a Ci-C₄-alkyl group, a C₆-C₁₀-aryl group or a halogen atom, in particular chlorine.

A preferred embodiment of the invention is a compound in which m = 0 or 1 when n = 1 and m = 0 when n = 2.

Preference is given to compounds of the formula I in which the X-ligands are identical and are each a halogen atom, in particular chlorine.

Particular preference is given to compounds of the formula I in which L is a boratabenzene ligand of the formula II and the radicals R are preferably identical and are each a hydrogen atom and Y is preferably a Ci~C₄-alkyl group such as methyl, ethyl, propyl, isopropyl or butyl, or -NR² ₂ in which R² is a Ci-C₄-alkyl group such as methyl, ethyl, propyl, isopropyl or butyl. When m is 1, A is preferably a cyclopentadienyl ligand such as cyclopentadienyl, methylcyclopentadienyl, pentamethylcyclopentadienyl or indenyl. Preference is also given to compounds of the formula I in which the X-ligands are identical and are each a Ci-C₄-alkyl group, in particular methyl, or a C₇- C₄₀-alkylaryl group, in particular benzyl or a halogen atom, in particular chlorine, and n is 1 or 2 and m is 0 or 1 when n is 1 and m is 0 when n is 2 and the sum of n+m+k can be 3, 4 or 5.

Examples of transition metal compounds of the invention are:

(1-methylboratabenzene) (pentamethylcyclopentadienyl) niobium dichloride, (1-methylboratabenzene) (pentamethylcyclopentadienyl)- vanadium chloride,

[l-(dimethylamino)boratabenzene] (cyclopentadienyl)- tantalum dichloride, bis(1-methylboratabenzene)niobium dichloride, bis(1-methylboratabenzene)vanadium chloride, (l-methylboratabenzene)niobium tetrachloride, (1-methylboratabenzene)niobium t ichloride, (1-methylboratabenzene)vanadium dichloride, (1-methylboratabenzene)vanadium trichloride, (1-methylboratabenzene) (indenyl)niobium dichloride, [1-(dimethylamino)boratabenzene] (indenyl)vanadium, chloride, di-(μ-chloro)-tetra[h.⁶-(l-methylborata- benzene)] discandium, di-(μ-chloro)-tetra[h,⁶-(l-methyl- boratabenzene) ]-digadolinium, {[ Y[⁶-(1-methylboratabenzene) ]tantalum tetrachloride}_z. The invention provides a process for preparing the novel transition metal compounds having the formula (I). The process is illustrated by the synthesis scheme below for compounds of the formulae IV, V and VI. In these formulae, M¹ is a metal of group 1 of the Periodic System and R³ is a Ci-C₂₀-hydrocarbon radical such as a Ci-C₁₀-alkyl group or a C₆-C_ι0-aryl group. In a process for preparing a compound having the formula (I), a compound having the formula (III) reacts with MX_X where 1 is an integer from 3 to 5.

In an alternative process for preparing a compound having the formula (I), a compound having the formula (V) reacts with A^"M¹⁺.

The compounds of the formula III can be prepared by methods known from (Organometallics 1995, 14, 471). The conversion of the compounds of the formula III into the desired transition metal complexes is known in principle. For this purpose, the monoanion of the formula III is reacted in an inert solvent with the corresponding metal halide. A^" is an anionic ligand such as cyclopentadienyl, indenyl or fluorenyl which can each be either substituted or unsubstituted.

(VI) Suitable solvents are aliphatic or aromatic solvents such as hexane or toluene, ether solvents such as tetrahydrofuran or diethyl ether or halogenated hydrocarbons such as methylene chloride or halogenated aromatic hydrocarbons such as o-dichlorobenzene.

The invention provides for the use of the compound having the formula I as a catalyst component in the polymerization of olefins. The present invention accordingly provides a process for preparing a polyolefin by polymerization of one or more olefins in the presence of a transition metal compound of the formula I. For the purposes of the invention, the term polymerization refers to both homopolymerization and copolymerization. In the process of the invention, preference is given to polymerizing one or more olefins of the formula

R^a-CH=CH-R^b

where R^a and R^b are identical or different and are each a hydrogen atom or a hydrocarbon radical having from 1 to 20 carbon atoms, in particular from 1 to 10 carbon atoms, or R^a and R^b together with the atoms connecting them form one or more rings. Examples of such olefins are 1-olefins having 1-20 carbon atoms, for example ethylene, propene, 1-butene, 1-pentene, 1-hexene, 4- methyl-1-pentene or 1-octene, styrene, cyclic or acyclic dienes such as 1,3-butadiene, isoprene, 1,4- hexadiene, norbornadiene, vinylnorbornene, 5- ethylidenenorbornene or cyclic monoolefins such as norbornene or tetracyclododecene. In the process of the invention, preference is given to homopolymerizing ethylene or propylene or copolymerizing ethylene with one or more acyclic 1-olefins having from 3 to 20 carbon atoms, for example propylene, and/or one or more dienes having from 4 to 20 carbon atoms, for example 1,3-butadiene.

The polymerization is preferably carried out at a temperature of from -60 to 250°C, particularly preferably from 50 to 20°C. The pressure is preferably from 0.5 to 2000 bar, particularly preferably from 5 to 64 bar.

The polymerization can be carried out in solution, in bulk, in suspension or in the gas phase, continuously or batchwise, in one or more stages. The catalyst used in the process of the invention preferably comprises a transition metal compound according to formula I. It is also possible to use mixtures of two or more transition metal compounds or mixtures with metallocenes, for example for preparing polyolefins having a broad or multimodal molecular weight distribution.

In principle, a suitable cocatalyst in the process of the invention is any compound which, owing to its Lewis acidity, can convert the neutral transition metal compound into a cation and stabilize the latter ("labile coordination"). Furthermore, the cocatalyst or the anion formed therefrom should undergo no further reactions with the cation formed (EP-A- 427 697). The cocatalyst used is preferably an aluminium compound or magnesium compound such as aluminoxane and/or an aluminium alkyl or a magnesium alkyl.

Boron compounds can also be used as a cocatalyst. The boron compound preferably has the formula R⁵ _XNH₄__XBR⁶ ₄, R⁵ _XPH₄__XBR⁶ ₄, R⁵ ₃CBR⁶ ₄ or BR⁶ ₃, where x is from 1 to 4, preferably 3, and the radicals R^s are identical or different, preferably identical, and are ^cι-Cι₀-alkyl or C₆-Cι₈-aryl or two radicals R⁵ together with the atoms connecting them form a ring, and the radicals R⁶ are identical or different, preferably identical, and are C₆-C₁₈-aryl which may be substituted by alkyl, haloalkyl or fluorine. In particular R⁵ is ethyl, propyl, butyl or phenyl and R⁶ is phenyl, penta- fluorophenyl, 3,5-bis(trifluoromethyl)phenyl, mesityl, xylyl or tolyl (EP-A-277 003, EP-A-277 004 and EP-A-426 638).

An aluminoxane, is particular one of the formula Vila for the linear type and/or the formula Vllb for the cyclic type,

- 6 -

CECIo )

where, in the formulae Vila and Vllb, the radicals R⁴ are identical or different and are each hydrogen or a Cι-C₂o~hydrocarbon group such as a Ci-C₁₈-alkyl group, a C₆-C₁₈-aryl group or benzyl and p is an integer from 2 to 50, preferably from 10 to 35. The radicals R⁴ are preferably identical and are hydrogen, methyl, isobutyl, phenyl or benzyl, particularly preferably methyl.

If the radicals R⁴ are different, then they are preferably methyl and hydrogen or alternatively methyl and isobutyl, with hydrogen or isobutyl preferably being present in a proportion of from 0.01 to 40% by number (of the radicals R⁴).

The methods of preparing the aluminoxanes are known. The exact spatial structure of the aluminoxanes is not known (J. Am. Chem. Soc. (1993) 115, 4971). For example, it is conceivable that chains and rings can join to form larger two-dimensional or three- dimensional structures. Regardless of the method of preparation, all alu inoxane solutions have in common a varying content of unreacted aluminium starting compound which is present in free form or as adduct.

Magnesium compounds which can be used are preferably dialkylmagnesium compounds such as, for instance, dibutylmagnesium and butyloctylmagnesium. It is possible to preactivate the transition metal compound using a cocatalyst, in particular an aluminoxane, prior to use in the polymerization reaction. This significantly increases the polymerization activity. The preactivation of the transition metal compound is preferably carried out in solution. The transition metal compound is here preferably dissolved in a solution of the aluminoxane in an inert hydrocarbon. Suitable inert hydrocarbons are aliphatic or aromatic hydrocarbons. Preference is given to using toluene.

The concentration of the aluminoxane in the solution is in the range from about 1% by weight to the saturation limit, preferably from 5 to 30% by weight, in each case based on the total amount of solution. The transition metal compound can be used in the same concentration, but it is preferably used in an amount of from 10^~4 to 1 mol per mol of aluminoxane. The preactivation time is from 5 minutes to 60 hours, preferably from 5 to 60 minutes. The preactivation is carried out at a temperature of from -78 to 100°C, preferably from 0 to 70°C.

The transition metal compound is preferably used in a concentration, based on the transition metal, of from 10~³ to 10"⁸ mol, preferably from 10"⁴ to 10^"7 mol, of transition metal per dm³ of solvent or per dm³ of reactor volume. The aluminoxane is preferably used in a concentration of from 10^"6 to 10^"1 mol, preferably from 10^~5 to 10^~2, mol per dm³ of solvent or per dm³ of reactor volume. The other cocatalysts mentioned are used in approximately equimolar amounts to the transition metal compound. However, higher concentrations are also possible in principle.

To remove catalyst poisons present in the olefin, purification using an aluminium compound, preferably an aluminium alkyl such as trimethylaluminium, t iethylaluminium or trioctylaluminium, is advantageous. This purification can be carried out either in the polymerization system itself or the olefin is brought into contact with the aluminium compound and subsequently separated off again before addition to the polymerization system.

In the process of the invention, hydrogen can be added as a molecular weight regulator and/or to increase the catalyst activity. This enables low molecular weight polyolefins such as waxes to be obtained.

In the process of the present invention, the transition metal catalyst is preferably reacted with the cocatalyst outside the polymerization reactor in a separate step using a suitable solvent. Application to a support can also be carried out during this procedure. In the process of the invention, a prepolymerization can be carried out with the aid of the transition metal compound. For the prepoly- merization, preference is given to using the (or one of the) olefin(s) used in the polymerization.

The catalyst used in the process of the invention can be supported. Application to a support enables, for example, the particle morphology of the polyolefin prepared to be controlled. Here, the transition metal compound can be first reacted with the support and subsequently with the cocatalyst. The cocatalyst can also be supported first and subsequently reacted with the transition metal compound. It is also possible to support the reaction product of transition metal compound and cocatalyst. Suitable support materials are, for example, silica gels, aluminium oxides, solid aluminoxane or other inorganic support materials such as magnesium chloride. Another suitable support material is a polyolefin powder in finely divided form. The preparation of the supported cocatalyst can be carried out, for example, as described in EP-A-567 952.

If the polymerization is carried out as a suspension or solution polymerization, an inert solvent customary for the Ziegler low-pressure process is used. For example, the polymerization is carried out in an aliphatic or cycloaliphatic hydrocarbon, for example propane, butane, hexane, heptane, isooctane, cydohexane or methylcyclohexane. A gasoline or a hydrogenated diesel oil fraction can also be used. It is also possible to use toluene. Preference is given to carrying out the polymerization in the liquid monomer.

Before addition of the catalyst, in particular the supported catalyst system (comprising the transition metal compound of the invention and a supported cocatalyst), another aluminium alkyl compound such as trimethylaluminium, triethylaluminium, triisobutylaluminium, trioctylaluminium or isoprenylaluminium can be introduced into the reactor to make the polymerization system inert (for example to remove catalyst poisons present in the olefin). This compound is added to the polymerization system in a concentration of from 100 to 0.01 mmol of Al per kg of reactor contents. Preference is given to triisobutylaluminium and triethylaluminium in a concentration of from 10 to 0.1 mmol of Al per kg of reactor contents. This enables the molar Al/M¹ ratio to be made small in the synthesis of the supported catalyst system.

If inert solvents are used, the monomers are preferably metered in in gaseous or liquid form. The specific transition metal compounds described in the present invention are suitable for the preparation of polyolefins. The latter are suitable, in particular, for producing shaped bodies such as films, plates or large hollow bodies (e.g. pipes) and can also be used as plasticizer and lubricant formulations, for melt adhesive applications, coatings, seals, insulation, filler compositions or sound insulation materials.

Use of hydrogen or increasing the polymerization temperature makes it possible to obtain polyolefins having a low molar mass, e.g. waxes, whose hardness or melting point can be varied by means of the comonomer content. Selection of the polymerization process and the type(s) of comonomer(s) , and also amount(s) of comonomer(s) , enables olefin copolymers having elastomeric properties to be prepared, for example ethylene-propylene-1,4-hexadiene terpolymers. Preparation and handling of organometallic compounds takes place with exclusion of air and moisture under protective argon gas (Schlenk technique). All solvents required are freed of air and moisture before use by boiling for a number of hours over a suitable desiccant and subsequent distillation under argon.

The AI/CH₃ ratio in the aluminoxane is determined by decomposing the sample with H₂S0₄ and determining the volume of the hydrolysis gases formed under standard conditions and by complexometric titration of the aluminium in the then completely dissolved sample by the Schwarzenbach method. The compounds are characterized using ^-NM , ¹³C-NMR and IR spectroscopy.

The invention will be further elucidated by the examples, without being restricted thereto.

Examples

Example I

Di ( μ-chloro )-tetra r |⁶- ( l-methylboratabenzene ) 1 - discandium

1 g (6.6 mmol) of scandium trichloride and 1.3 g (13.3 mmol) of (l-methylboratobenzene)lithium are suspended in 20 ml of toluene and stirred for 3 days at 110°C. Filtration of the orange reaction mixture to remove the salt formed and cooling the filtrate to - 30°C gives [Sc₂(_/j-Cl)₂( ⁶-C₅H₅BMe)₄] in the form of orange crystals. Further product can be obtained by evaporating the mother liquor under reduced pressure and again cooling to -30°C. Yield: 1 g (58 %)

Example II

Di(u-chloro)-tetrar ⁶-(l-methylboratabenzene) 1- diσadolinium

0.92 g (3.49 mmol) of gadolinium trichloride and 0.69 g (7.0 mmol) of (1-methylboratobenzene)lithium are suspended in 10 ml of toluene and stirred for 3 days at 110°C. Filtration of the yellow reaction mixture to remove the salt formed and cooling the filtrate to -30°C gives [Gd₂(μ-Cl)₂(ή⁶-C₅H_sBMe)₄] in the form of pale yellow crystals. Further product can be obtained by evaporating the mother liquor under reduced pressure and again cooling to -30°C. Yield: 0.78 g (60 %)

Example III trh⁶-(l-methylboratabenzene) 1tantalum tetrachloridel. 0.8 g (2.23 mmol) of tantalum pentachloride is initially charged in 10 ml of toluene. 0.57 g (2.25 mmol) of l-methyl-6-(trimethylstannyl)-2,4- boracyclohexadiene is dissolved in 10 ml of toluene and added dropwise at room temperature. A deep red precipitate is immediately formed. The suspension obtained is stirred further for about one hour and then filtered. The deep red powder obtained is washed with 10 ml of toluene and with 10 ml of pentane. Yield: 0.83 g (90 %)

Example IV

A 1.3 1 steel reactor was charged with 500 ml hexane under nitrogen atmosphere. The temperature was held at 50°C and 0.05 MPa (0.5 bar) hydrogen was dosed untill a pressure of 0.7 MPa (7 bar). 20 mmol of the catalyst according to Example I was contacted with 40 mmol butyloctylmagnesium and thereafter dosed to the reactor. After 10 minutes the polymerisation was stopped. 6.3 g polyethylene was obtained.

Example V

Example IV was repeated as described above, but 0.2 MPa (2 bar) hydrogen was dosed instead of 0.05 MPa (0.5 bar). 7.1 g polyethylene was obtained.

Claims

1 . A compound having the f ormula I

L_nA_mMX_k ( I ) , wherein L is a boratabenzene ligand of the formula II

wherein the radicals R are identical or different and are each a hydrogen atom, a C₁-C₁₀-group such as a C₁-C₁₀-alkyl group or a C₆-C₁₀-aryl group and two adjacent radicals R together with the atoms connecting them can form a ring system, and Y is a hydrogen atom, a C₁-C₁₀-group such as a C₁-C₁₀- alkyl group or a C₆-C₁₀-aryl group, a halogen atom, an -NR² ₂ or -PR² ₂ radical, where R² is a halogen atom, a C₁-C₁₀-group such as a C₁-C₁₀-alkyl group or a C₆-C₁₀-aryl group,

A is a π-ligand such as cyclopentadienyl which can be either substituted or unsubstituted and

adjacent substituents on the cyclopentadienyl ligand can form a ring,

M is a metal of group 3 or 5 of the Periodic

System of the Elements and

X is a hydrogen atom, a C₁-C₄₀-group such as a C₁- C₂₀-alkyl group, a C₁-C₁₀-alkoxy group, a C₆-C₂₀- aryl group, a C₂-C₁₂-alkenyl group, a C₇-C₄₀- arylalkyl group, a C₇-C₄₀-alkylaryl group, an OH group, a halogen atom or -NR² ₂,

n is 1 or 2,

m is 0 or 1 and

k is an integer from 1 to 4,

where the sum of n+m+k is from 3 to 5.

2. A compound as claimed in claim 1 in which the

radicals R are identical and are each a hydrogen atom, a C₁-C₄-alkyl group or a C₆-C₁₀-aryl group and Y is a C₁-C₄-alkyl group or -NR² ₂, where R² is a C₁-C₄-alkyl group.

3. A compound as claimed in claim 1 or 2 in which A is a substituted cyclopentadienyl ligand.

4. A compound as claimed in one or more of claims 1 to 3 in which X is -NR² ₂, where R² is a C₁-C₄-alkyl group, a C₆-C₁₀-aryl group or a halogen atom, in particular chlorine.

5. A compound as claimed in any one of claims 1 to 4, wherein m = 0 or 1 when n = 1 and m = 0 when n = 2.

6. A process for preparing a compound having the

formula (I) as claimed in any one of claims 1 to 5, wherein a compound having the formula (III)

reacts with MX₁, wherein L is an integer from 3 to 5.

7. A process for preparing a compound having the formula (I) as claimed in any one of claims 1 to 5, wherein a compound having the formula (V)

reacts with A-M ¹⁺ 8. Use of the compound having the formula I as

claimed in any one of claims 1 to 5 as a catalyst component during the polymerization of olefins.