IL121402A - A novel homogeneous catalyst system for the polymerization of alpha-olefins and a method of preparing same - Google Patents

Description

121402/3 1 A NOVEL HOMOGENEOUS CATALYST SYSTEM FOR THE POLYMERIZATION OF a-OLEFINS AND A METHOD OF PREPARING SAME 121402/3 2 The present invention relates to homogeneous catalyst system, useful for the polymerization of a-olefms. More particularly, the invention relates to novel homogeneous catalyst system, which comprises an octahedral transition metal complex, free of cyclopentadiene ligands, and an anion of an acid, and to a method of preparing same.

BACKGROUND OF THE INVENTION.

The polymerization of α-olefms with the known Ziegler-Natta catalysts is well-known in the chemical industry and used at a large extent. Nevertheless, there are still many publications and patents describing various improvements which will impart a better control over their molecular weight and molecular weight distribution. Moreover, a very great advance would be obtained, if the stereo-regularity of each polymeric chain could be controlled, by physical means. According to a recent review (the present inventor being a co-author), which appears in the Journal of Organometallic Chemistry 503 (1995) 307-14, a series of Bis(rrimethyl-silyl)benzamidine zirconium dichlorides are suggested as active catalysts for ethylene polymerization. It is concluded that the polymerization activity increases drastically with an increase in pressure and temperature, but decreases when electron-releasing groups are attached to the aromatic ring.

In U.S. Patent Number 5,330,948, (the present inventor being a co-inventor) homogeneous catalysts for stereoregular olefin polymerization are disclosed. According to this patent, by using a catalyst having a chiral substituent, selected from neomenthyl, menthyl and phenylmenthyl, in the presence of a cocatalyst, a better control over the desired properties of the resulting polymer are achieved.

In Israeli Patent Application No. 113,936 of the inventor novel bridged transition metal complexes are disclosed. Heterolytic activation of these 121402/3 3 complexes in the presence of a strong Lewis acid in a solvent leads to the formation of cationic complexes useful for the polymerization and copolymerization of olefins.

The synthesis of stereoregular polymers has been reported with the use of chiral organo-group IV (Ti, Zr, Hi) catalysts having an approximative C2 symmetry. It is claimed that such catalysts produce an isospecific polymerization of a-olefins. However, only in a few cases the isotacticities of the polymeric products at a useful level were obtained.

The obtaining of a chiral metal catalyst relies on the design of the appropriate ligands which create an asymmetric environment around the metal center. On the other hand, the design of a racemate is based on non-chiral ligands which arrange themselves, and would produce a mixture of enantiomeric metal catalysts.

It is an object of the present invention to provide a new family of chiral and racemic octahedral transition metal complexes and a method for the manufacture thereof. It is another object of the present invention to provide a catalyst system for the polymerization of alpha-olefins, which comprises the transition metal complexes described above and a cocatalyst, and which provides for an improved control over the molecular weight distribution of the resulting polymers, permits a better control of the desired chemical or physical properties in the resulting polymers and permits a stereoregular control determination on each chain selectively by changing a physical property with a rated frequency.

BRIEF DESCRIPTION OF THE INVENTION.

The present invention relates to a homogeneous catalyst system for the polymerization of alpha-olefins comprising (a) a cationic form of a chiral octahedral transition metal complex comprising 1, 2 or 3 bidentate chelating ligands and no cyclopentadienyl ligands and having symmetry selected from the group consisting of C\, C2 and C3 symmetries; and an anion of an acid selected from the group consisting of a Lewis acid and a Bransted acid. 121402/3 4 The present invention also relates to a method of preparing a homogenous catalyst system including the catalyst complex by preparing a chiral octahedral transition metal complex comprising 1, 2 or 3 bidentate chelating ligands and no cyclopentadienyl ligands and having symmetry selected from the group consisting of d, C2 and C3 symmetries by reacting a chiral heteroallylic ligand with a compound having the general formula MX4, wherein M is selected from Ti, Zr and Hf and X is a halogen atom selected from CI, Br, I, in a polar or non-polar solvent; and adding to the complex a Lewis acid or a Bronsted acid co-catalyst.

DESCRIPTION OF THE FIGURES.

FIGURE 1, illustrates a rigid chiral ligand template, arrayed in a symmetrical manner around the metal coordination sphere (M) and a mixture of racemic symmertrical array of octahedral complexes (B).

FIGURE 2„ illustrates the cationic chiral and racemic complexes according to the present invention, wherein M is a transition metal, preferably selected from Zr, Hfand Ti; L, is a substituted or unsubstituted ligand selected from the group consisting of a halogen atom (e.g., CI, Br, I), alkyl, aryl, hydrocarbon, amide, amine, an oxygen atom, a boron atom, phosphine, silyl and an organometallic moiety thereof.

A, is a counter ion from either a Lewis acid or a Bronsted base, obtained by a reaction with the neutral catalyst.

Q, T, and Y, can be the same or different and each is independently selected from the group consisting of oxygen, nitrogen, carbon, sulfur, silicon, boron and phosphor, wherein Z and R1-R4 can be the same or different, each being independently hydrogen, and a fragment containing one or more atoms selected from boron, carbon, silicon, nitrogen, oxygen and phosphor, wherein one or more of R1-R4 may form a ring with L or one with the other.

Preferably each of Rp * is independently selected from the group consisting of a hydrocarbon and a silyl group containing between 1 to 20 carbon atoms. A, is 121402/3 a counter ion obtained from either a Lewis acid or a Bronsted base after a reaction with a neutral catalyst.

In figure 1, the R* group is a natural chiral ligand, such as menthyl, a-phenethyl, neomenthyl, myrtanyl, etc. which renders the two enantiomers of A2 and A3 diasteromeric and thus enables a means of separation. Furthermore, the use of non-chiral ligands arranged in an octahedral symmetry around a metal, will produce a racemic mixture and therefore no separation will be required. In this manner, the above ligands and their arrangements are very simple to be obtained.

DETAILED DESCRIPTION OF THE INVENTION.

For a chiral ligand, a heteroallylic octahedral complex having a chiral substituent, such as menthyl, myrtanyl or phenethyl (R*) is obtained by reacting a chiral amine with a chemical substance containing a group such as alkyl, aryl and trimethylsilyl halide, which can easily react with the chiral amine, in a high-boiling polar solvent such as tetrahydrofuran (THF). As can be noticed from both Figures 1 and 2, the resulted chiral amine substance, combined with an alkyl lithium complex, or other organometallic moiety, and further with a nitrile group in a polar solvent selected from dimethylsulfoxide, dimethyl ether, dimethyl formamide or tetrahydrofuran, will produce the chiral heteroallylic lithium salt of the ligand (R^R^CCNR'XNR^M', wherein: M' is selected from, for example, Li, Na, Cs and K (group I in the periodic table), or any metal of group II (in the periodic table), while each of R', R1 and R2 is independently selected from an alkyl having 1-20 carbon atoms, an aryl, a silicon containing group, oxygen containing group, and perfluroalkyl containing group, whereby R 1 is a substituent of R 2.

The required chiral complex is produced by reacting the chiral heteroallylic ligand with a compound having the general formula MX4, wherein M is selected from Ti, Zr and Hf, while X is a halogen atom selected from CI, Br, I and MX4, preferably being zirconium chloride (ZrCl4), in a polar or non polar solvent. Such polar solvents are selected from THF, DME, Diethyl ether, 121402/3 6 pentane, toluene. Depending on the amount of the ligand, the obtained chiral complex has the formula (R1-R2)C(NR')(N *)4-nMXn, wherein n is between 1 and 3.

According to one embodiment, the halogen atom (X) may be replaced by various fragments, having between 1 and 20 atoms. Preferred fragments include, for example, alkyl groups, optionally interrupted or substituted by one or more phosphine groups and/or nitrogen containing groups (e.g., amine or amide) and/or any other group containing an element from groups XI to XVII in the periodic table, and/or the respective organometallic moieties thereof, obtained by the addition of an alkylating agent such as RLi, RMgX or MgR2 in a non-polar solvent.

A Lewis acid co-catalyst, such as alumoxane or B(C6F5)3 or any other perfluoroarylboranes, can be added to the complexes described above, so as to produce a homogeneous catalyst system, which efficiently catalyzes a-olefins. Another co-catalyst which may be used in the catalyst system of the present invention is a Bronsted acid, having the general formula ΗΎ^Ζ" wherein is a fragment containing an element from group XV or XVI in the periodic table, optionally substituted by one or more alkyl groups having 1-20 carbon atoms (e.g., a fragment in the form of N^R], R2, R3), wherein Rb R2) and R3 are alkyl groups), and Z" is a fragment containing an element of group XIII in the periodic table (e.g., boron or alluminium). Typical examples of such acids being suitable as co-catalysts may be selected from HN+(CH3)3[B(C6F5)4]", HN+(CH3)3[A1(C6F5)4]", HP+(CH3)3[B(C6F5)4]-.

According to another embodiment, it is also possible to use a carbodiimide with an alkyl lithium salt, thus obtaining a racemic mixture of the heteroallylic ligands (R1-R2-R)C(NR*)(NR")M' wherein: Each of R1, R2, R' and R" is independently selected from an alkyl having 1-20 carbon atoms, aryl, halide, silicon containing group, oxygen-containing group, perfluoroalkyl or perfluoroalkyl containing group, whereby 121402/3 7 R is a substituent of R , which in turn is a substituent of R, such that (R -R -R) reprsents one substituent of C; M' is selected from, for example, Li, Na, Cs and K (metals of group I of the periodic table) or any metal from group II in the periodic table.

The above heteroallylic ligand is reacted with MX4, wherein M is selected from Ti, Zr, Hf and X is selected from CI, Br and I, amide, or amine, in a polar or non-polar solvent such as THF, DME, diethyl ether, pentane and toluene, thus yielding, depending to the amount of ligand, the complex: [(R1-R2-R)C(NR*)(NR")]4-n MXn (n being between 1 and 3).

The most preferred MX4 is ZrCl4.

As is described above, the halogen atom (X) may be replaced by various fragments, having between 1 and 20 atoms. Preferred fragments include, for example, alkyl groups, optionally interrupted or substituted by one or more phosphine groups and/or nitrogen containing groups (e.g., amine or amide) and/or any other group containing an element from groups XI to XVII in the periodic table, and/or the respective organometallic moieties thereof, obtained by the addition of an alkylating agent such as RLi, RMgX or MgR2 in a non-polar solvent.

As is further described above, such a racemic complex, together with a cocatalyst such as alumoxane, or B(C6F5)3, or other perfluoroarylboranes, form a homogeneous catalyst system for the polymerization of a-olefms such as propylene.

In a similar procedure, a carbondiimide can be used with an alkyl lithium salt, in order to obtain a racemic mixture of a heteroallylic ligand (R1-R2)C(NR')(NR)"M', wherein M' = Li, Na, Cs, K or a metal of group II in the periodic table and each of R1, R2, R' and R" is independently an alkyl having 1-20 carbon atoms, aryl, silicon containing group, perfluoroalkyl or perfluoroaryl containing group, whereby R1 is a substituent of R2.

The invention will be hereafter illustrated by a number of Examples, being understood that these are presented only for a better understanding of the 121402/3 8 invention without limiting the scope of the invention as covered by the appended Claims.

All manipulations of air-sensitive materials were performed with the rigorous exclusion of oxygen and moisture in flamed Schlenk-type glassware on a dual manifold Schlenk line, or interfaced to a high vacuum (10~5 torr) line, or in a nitrogen filled Vacuum Atmospheres glove box with a medium capacity recirculator (1-2 ppn O2).

Argon and nitrogen were purified by passage through a MnO oxygen-removal column and a Davidson 4A molecular sieve column. Ether solvents were distilled under argon from benzophenone ketyl. Hydrocarbon solvents (toluene-d8, C6D6, hexane) and TMEDA (tetramethylethylenediamine) were distilled under nitrogen from Na/K alloy. All solvents for vacuum line manipulations were stored in vacuo over Na/K alloy in resealable bulbs. Nitrile compounds (Aldrich) were degassed and freshly distilled under argon.

LiN(TMS)2,C6H5C(NSiMe3)2Li*TMEDA,C6H5C[NC(i-Pr)2Li C6H5CrNC(C6H11)2Li*TMEDA were prepared as known in the art. 121402/3 9 EXAMPLE 1. Synthesis of 4-CH,CsH4C(NSiMe,)2-TMEDA. .86 g (0.095 mol) of LiN(trimethylsilyl)2 were stirred in a hexane suspension (180 ml) at 0°C and then 11.1 g (0.095 mol) of 4-methylbenzonitrile were slowly added. The temperature of the mixture was slowly raised to about 50° C and stirred for three additional hours.

After cooling to room temperature, an amount of 14.48 g (0.123 mol) of TMEDA were added and the solution stirred for about one hour.

During the addition of the TMEDA, the color of the solution turned to brown-red and after several minutes, a large amount of the above product precipitated. The solution stood overnight at about -50°C and was filtered while cold. The separated precipitate was dried under a high vacuum, obtaining 31.6 g of a white crystalline product (yield 83%).

EXAMPLE 2. Synthesis of Dichloro-bis(Njy-dimethvIsilyl)-4-methyI-benzamidinato)titanium(IV .

To a solution of 5.27 g (15.8 mmol) of TiCl4(THF)2 in 130 mis of THF, a solution of 12.7 g (31.6 mmol) of Li{4-CH3C6H4-C(NsiMe3)2} in 100 ml of THF was added under stirring. The reaction mixture was stirred overnight at room temperature and the solvent removed by vacuum. The residue obtained was extracted with 80 ml of toluene and the precipitated LiCl was removed by filtration through a thin layer of Celite filter-aid.

The clear filtrate was evaporated to dryness, washed with 20 - 30 mis of hexane and dried under vacuum for about 12 hours, obtaining 8.06 g of a red product (the yield being 76%).

EXAMPLE 3. Synthesis of Dichloro-bis(N.N'-diisopropyl-benzamidinato)zirconium(IV).

To a solution of 7.54 g (20.0 mmol) ZrCl4(THF)2 in 130 ml THF, a solution of 8.41 g (40.0 mmol) of Li[C6H5C(NC3H7)2] in 100 ml of THF, was added dropwise at room temperature over a period of 15 minutes. The reaction mixture was stirred overnight at room temperature. The solvent was removed 121402/3 under vacuum, and the residue extracted with 80 ml of toluene and the precipitated LiCl was removed by filtration through a thin layer of Celite filter-aid. The clear filtrate was evaporated to dryness, washed with hexane (20 - 30 ml) and dried under vacuum, for about 12 hours, thus obtaining 6.78 g (60%) of a pale yellow, crystalline powder.

EXAMPLE 4. Synthesis of Dichloro-bisfNJ -dicvclohexyl-benzamidinato)titanium(IV) To a solution of 5.27 g (15.8 mmol) TiCl4(THF)2 in 130 ml THF, a solution of 9.97 g (34.3 mmol) in 100 ml THF was added dropwise. The reaction mixture was stirred overnight at room temperature. The solvent was removed in vacuum and the residue extracted with 80 ml of toluene and the precipitated LiCl was removed by filtration through a thin layer of Celite filter-aid.

The clear filtrate was evaporated to dryness, washed with hexane (20-30 ml) and dried under vacuum, for about 12 hours, thus obtaining 9.02 g (75%) of a red product.

EXAMPLE 5. Synthesis of DichIoro-bis(N,N,-diphenylbenzamidinato)zirconium (IV) To a solution of 6.49 g (17.2 mmol) ZrCl4(THF)2 in 130 ml THF, a solution of 9.53 g (34.3 mmol) Li[C6H5C(NC6H5)2] in 100 ml THF was added dropwise. The reaction mixture was stirred overnight at room temperature. The solvent was removed in vacuum and the residue extracted with 80 ml of toluene and the precipitated LiCl was removed by filtration through a thin layer of Celite filter-aid.

The clear filtrate was evaporated to dryness, washed with hexane (20-30 ml) and dried under vacuum for about 12 hours, thus obtaining 8.82 g (79%) of a pale yellow product. 121402/3 11 It is important to note that those portions of the specification which do not fall within the scope of the claims of this application do not belong to the invention.

Claims (13)

121402/3 12 CLAIMS:

1. A homogeneous catalyst system for the polymerization of alpha-olefins, the homogeneous catalyst system comprising: (a) a cationic form of a chiral octahedral transition metal complex comprising 1, 2 or 3 bidentate chelating ligands and no cyclopentadienyl ligands and having symmetry selected from the group consisting of Ci, C2 and C3 symmetries; and (b) an anion of an acid selected from the group consisting of a Lewis acid and a Bronsted acid.

2. The homogeneous catalyst system of claim 1 , wherein said symmetry is Ci symmetry.

3. The homogeneous catalyst system of claim 1 , wherein said symmetry is C2 symmetry.

4. The homogeneous catalyst system of claim 1 , wherein said symmetry is C3 symmetry.

5. The homogeneous catalyst system of claim 1 , wherein at least one of said ligands possesses a chiral substituent selected from menthyl, myrtanyl and phenetyl. 121402/3 13

6. A method of preparing the homogenous catalyst system of claim 1, the method comprising: preparing a chiral octahedral transition metal complex comprising 1 , 2 or 3 bidentate chelating ligands and no cyclopentadienyl ligands and having symmetry selected from the group consisting of Ci, C2 and C3 symmetries by reacting a chiral heteroallylic ligand with a compound having the general formula MX4, wherein M is selected from Ti, Zr and Hf and X is a halogen atom selected from CI, Br, I, in a polar or non-polar solvent; and adding to said complex a Lewis acid or a Bronsted acid co-catalyst.

7. The method of claim 6, wherein said solvent is selected from the group consisting of tetrahydrofuran, diethyl ether, pentane and toluene.

8. The method of claim 6, further comprising replacing at least one of said halogen atoms by at least one fragment having up to twenty atoms.

9. The method of claim 8, wherein said at least one fragment comprises alkyl, aryl, hydrocarbon, amide, amine, oxygen, boron, phosphine, silyl and/or an organometallic moiety thereof.

10. The method of claim 6, wherein said co-catalyst has the general formula HHT^Z", wherein Y+ is a fragment containing an element from group XV or XVI of the periodic table, optionally substituted by at least one alkyl group having 1- 121402/3 14 20 carbon atoms and Z is a fragment containing an element from group XIII of the periodic table.

11. The method of claim 10, wherein said co-catalyst is selected from the group consisting of HN+(CH3)3[B(C6F5)4]", HN+(CH3)3[A1(C6F5)4]", and HP+(CH3)3[B(C6F5)4]\

12. A new homogeneous catalyst system for the polymerization of alpha- olefins, substantially as described in the specification and claimed in any one of claims 1 to 5.

13. A method for the preparation of the catalyst system of claim 12, substantially as described in the specification and claimed in any one of claims 6-11. Patent Attorney G.E. Ehrlich (1995) Ltd. 11 Menachem Begin Street 52 521 Ramat Gan