A catalyst for the catalytic syndiotactic polystyrene

Abstract

The application provides a catalyst for catalyzing syndiotactic polystyrene, which comprises a rare earth complex having a structure shown in formula I. The application provides that the catalytic polymerization of styrene by a catalyst combination can realize high activity and high syndiotactic polymerization of styrene, and the monomer conversion rate can reach 100% at most, the activity range is between 520-19980 kgmol Ln ‑1 h ‑1 , the syndiotacticity is between 80-100%, the number average molecular weight of the prepared syndiotactic polystyrene is adjustable between 8.4-935,000 with the change of the molar ratio of styrene monomer to catalyst, the molecular weight distribution is narrow, the lowest can reach 1.21, the melting point is in the range of 266-273 DEG C, and the catalyst has good adaptability in the polymerization temperature range of-20-60 DEG C.

Description

Technical Field

[0001] This invention relates to a catalyst for catalyzing syndiotactic polystyrene, and to the field of syndiotactic polystyrene preparation technology. Background Technology

[0002] In addition to possessing all the advantages of atactic polystyrene, syndiotactic polystyrene also exhibits high elastic modulus, high heat resistance, strong solvent resistance, and chemical resistance, comparable to engineering plastics. Furthermore, it possesses properties such as low density and low dielectric constant, which are not found in other engineering plastics. It has broad application prospects in fields such as electrical components in the automotive industry, consumer electronics, and industrial films. The preparation of syndiotactic polystyrene is also one of the research hotspots in this field.

[0003] In 1985, Ishihara et al. in Japan successfully synthesized syndiotactic polystyrene for the first time. Its melting point is as high as 270℃, and its crystallization rate is extremely fast (two orders of magnitude faster than isotactic polystyrene). In addition to possessing all the advantages of atactic polystyrene, syndiotactic polystyrene also exhibits high elastic modulus, high heat resistance, strong solvent resistance, and chemical resistance, comparable to engineering plastics. Furthermore, it possesses properties not found in other engineering plastics, such as low density and low dielectric constant. It has broad application prospects in automotive electrical components, consumer electronics, and industrial films. Therefore, the preparation of syndiotactic polystyrene has attracted widespread research interest. Simple monocyclic titanium oxide catalysts were the earliest catalysts used to effectively catalyze the syndiotactic polymerization of styrene. With further research, rare earth metals have been found to be effective catalysts for the polymerization of syndiotactic polystyrene, helping to improve the catalytic activity of styrene. Therefore, this invention provides a catalyst for syndiotactic polystyrene, mainly comprising a rare earth complex, which has advantages such as high monomer conversion rate, high activity, high syndiotacticity, and tunable molecular weight. Summary of the Invention

[0004] This invention provides a catalyst for catalyzing syndiotactic polystyrene, which has the advantages of high monomer conversion, high activity, high syndiotacticity, and adjustable molecular weight.

[0005] A first aspect of the present invention provides a catalyst for catalyzing syndiotactic polystyrene, the catalyst comprising a rare earth complex having a structure represented by Formula I:

[0006]

[0007] In Formula I, R1 is selected from one of cyclopentadienyl and its derivatives, indenyl and its derivatives, and fluorenyl and its derivatives. Cyclopentadienyl and its derivatives refer to a group having the structure shown in Formula II or a derivative obtained by substituting at least one H atom in the group. Indenyl and its derivatives refer to a group having the structure shown in Formula III or a derivative obtained by substituting at least one H atom in the group. Fluorenyl and its derivatives refer to a group having the structure shown in Formula IV or a derivative obtained by substituting at least one H atom in the group.

[0008]

[0009] R2 and R3 are each independently selected from one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl, and 2,6-ditert-butylphenyl;

[0010] R4 is one of the following C1-C20 alkyl, C1-C20 alkylsilyl, C1-C20 alkylamine, borohydride, and allyl groups. C1-C20 alkyl groups refer to aliphatic hydrocarbons with 1-20 carbon atoms, such as methyl, ethyl, and isopropyl. The general structural formula for C1-C20 alkylsilyl groups is -SiX3, where X is an alkyl group and the total number of carbon atoms is 1-20. C1-C20 alkylamine groups refer to alkyl groups with an amino terminal group and the number of carbon atoms in the alkyl group is 1-20. Borohydride is represented by -BH4. The molecular structure of allyl includes a double bond and a propyl group.

[0011] Ln is one of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; E is one of C, Si, and Ge; Y is one of tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether, and toluene; m = 1 or 2; n = 0, 1, or 2.

[0012] The rare earth complex with the structure shown in Formula I provided by this invention is an eta5-coordinated rare earth complex, a compound with a restricted geometric configuration. Due to the presence of eta5 coordination of cyclopentadienyl (cyclopentadienyl and its derivatives, indenyl and its derivatives, and fluorenyl and its derivatives) and the electron-withdrawing effect of the nitrogen-containing aromatic ring, as well as the presence of oxygen atoms coordinating to the central metal, which restricts the space of the central metal, it can selectively insert styrene monomers during the catalytic polymerization of syndiotactic styrene. Furthermore, by changing the feed amount, syndiotactic polystyrene with different molecular weights can be obtained. Experimental results show that the catalyst and catalyst combination provided by this invention can achieve highly active, highly syndiotactic polymerization of styrene, with a monomer conversion rate of up to 100% and an activity range of 520-19980 kgmol.Ln - 1 h -1 Between, the highest can reach 19980 kgmol Ln -1 h -1 The syndiotacticity is between 80-100%, and can reach up to 100%. The number-average molecular weight of the prepared syndiotactic polystyrene is adjustable between 84,000 and 935,000 depending on the molar ratio of styrene monomer to catalyst. The molecular weight distribution is relatively narrow (1.21-1.52), and can reach as low as 1.21. The melting point is in the range of 266-273℃. The catalyst has good adaptability in the polymerization temperature range of -20-60℃.

[0013] To further optimize the rare earth complex, R1 is selected from one of indene and its derivatives, fluorenyl and its derivatives, and more specifically, R1 is selected from fluorenyl and its derivatives. This invention does not have any particular limitation on cyclopentadienyl derivatives, indene derivatives, or fluorenyl derivatives, and any derivatives well known to those skilled in the art can be used.

[0014] R2 and R3 are each independently selected from one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl, and 2,6-di-tert-butylphenyl; further, R2 and R3 are each independently selected from one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, and 2,6-di-tert-butylphenyl.

[0015] Ln is selected from one of Sc, Y, La, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; furthermore, Ln is selected from one of Sc, Y, La, Nd, Gd, Er, Tm, and Lu.

[0016] R4 is selected from one of C1-C20 alkyl, C1-C20 alkylsilyl, borohydride, and allyl; furthermore, R4 is selected from one of C1-C20 alkylsilyl, borohydride, and allyl.

[0017] Y stands for tetrahydrofuran; n = 0 or 1.

[0018] The present invention does not impose any particular limitation on the selection and combination of substituents in the rare earth complexes having the structure of Formula I. The selection and combination methods known to those skilled in the art are acceptable. In addition, the present invention provides compounds represented by Formulas 1-20 (see Table 1), wherein the complexes represented by Formulas 1-12 are alkylsilyl or alkylamine rare earth complexes, the complexes represented by Formulas 13-17 are allyl rare earth complexes, and the complexes represented by Formulas 18-20 are borohydride rare earth complexes.

[0019] The present invention also provides a method for preparing a rare earth complex having the structure shown in Formula I, which, in one specific embodiment, includes the following steps:

[0020] Step 1: Under anhydrous and oxygen-free conditions, a ligand having the structure shown in Formula V, alkyl lithium, and an organic solvent are mixed and reacted to obtain the first reaction product.

[0021]

[0022] In Formula V, R1 is selected from one of cyclopentadienyl and its derivatives, indenyl and its derivatives, and fluorenyl and its derivatives; R2 and R3 are independently selected from one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl, and 2,6-ditert-butylphenyl; E is one of C, Si, and Ge; m = 1 or 2. This invention does not impose any particular limitation on the source of the ligand having the structure shown in Formula V, and it can be prepared using synthetic methods well known to those skilled in the art. For example, it can be prepared with reference to the following literature: H.Miao, S.Wang, S.Zhou, Y.Wei, Z.Zhou, H.Zhu, S.Wu, H.Wang, Inorganica Chimica Acta, 2010, 363, 1325-1331.

[0023] The alkyllithium refers to an alkyl derivative of lithium, with the general formula RLi, where R is alkyl, cycloalkyl, or aryl. Further, R is one of methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, silanylamino, dimethylamino, diethylamino, dipropylamino, N,N-dimethylaminophenyl, trimethylsilylmethyl, bistrimethylsilylmethyl, o-methylmercaptophenyl, o-dimethylphosphinophenyl, tetrahydroboryl, methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, sec-butoxy, and tert-butoxy. Even further, R is n-butyl, N,N-dimethylaminophenyl, trimethylsilylmethyl, or bistrimethylsilylmethyl. Even further, R is n-butyl. The organic solvent is a conventional solvent in the art, specifically one or more of tetrahydrofuran, pyridine, n-hexane, and ethylene glycol dimethyl ether. Even further, the organic solvent is tetrahydrofuran.

[0024] The molar ratio of alkyllithium to ligands having the structure shown in Formula V is (1-1.2):1, and further, the molar ratio of alkyllithium to ligands having the structure shown in Formula V is (1:1.15):1; the volume ratio of organic solvent to ligands having the structure shown in Formula V is (4-6) L:1 mol, and further, the volume ratio of organic solvent to ligands having the structure shown in Formula V is (4.5-5.5) L:1 mol;

[0025] The reaction temperature of the ligand having the structure shown in Formula V and the alkyllithium is -78°C to 40°C, further, the reaction temperature is -50°C to 30°C, further, -10°C to 20°C, and the reaction time is 0.8 to 1.5 hours, further, the reaction time is 0.8 to 1.2 hours, and further, 1 hour.

[0026] To stabilize the reaction process, the ligand having the structure shown in Formula V and the alkyl lithium can be dissolved separately in an organic solvent. Then, the two organic solvents are mixed and the reaction is carried out under anhydrous and oxygen-free conditions. In the alkyl lithium solution, the concentration of alkyl lithium is 1.0-2.0 mol / L, and more specifically, the concentration of alkyl lithium is 1.2-1.8 mol / L.

[0027] The present invention does not impose any particular restrictions on the anhydrous and oxygen-free reaction conditions, and can be carried out using operations well known to those skilled in the art. For example, an inert gas can be introduced to obtain anhydrous and oxygen-free conditions, specifically nitrogen gas.

[0028] Step 2: React the first reaction product with a rare earth halide to obtain the second reaction product;

[0029] Rare earth halides have the general structural formula LnX3, where Ln represents a rare earth element, specifically one of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Further, the rare earth element is one of Y, La, Gd, Er, and Lu; X represents a halogen, specifically one of F, Cl, Br, and I.

[0030] The first reaction product obtained in step 1 is reacted with a rare earth halide to obtain a second reaction product. The molar ratio of the rare earth halide to the ligand shown in formula V is (1-1.2):1, further, the molar ratio is (1.05-1.15):1, the reaction temperature can be -78-40℃, the reaction time is 3-5 hours, further, the reaction time is 3.5-4.5 hours, and even further, the reaction time is 4 hours.

[0031] Step 3: React the second reaction product with a substituent-containing compound to obtain a rare earth complex having the structure shown in Formula I;

[0032] The substituent-containing compound refers to a compound including an R4 group. Compounds containing C1-C20 alkyl groups can be C1-C20 alkane compounds; compounds containing C1-C20 alkylsilyl groups can be C1-C20 silanes; compounds containing C1-C20 alkylamine groups can be C1-C20 aliphatic amines; compounds containing borohydride groups can be sodium borohydride; compounds containing allyl groups can be allyl Grignard reagents or allyl derivative Grignard reagents. For example, the allyl Grignard reagent is selected as C3H5MgCl, and the allyl derivative Grignard reagent is preferably C3H5MgCl2. n R5MgCl, where n is 3 or 4, and R5 is a C1-C20 aliphatic group, a C1-C20 alicyclic group, a substituted or unsubstituted phenyl group. The substituted group on the phenyl group can be one of a C1-C20 aliphatic group, a C1-C20 alicyclic group, or an aromatic group.

[0033] The molar ratio of the substituent compound to the ligand having the structure shown in Formula V is (2-2.4):1, and further, the molar ratio of the two is (2-2.2):1.

[0034] Step 3 has no particular limitation on the reaction temperature and can be carried out at room temperature. Further, the reaction temperature is 20-30℃ and the reaction time is 10-14 hours. Further, the reaction time is 11-13 hours and even further, 12 hours. After the reaction is completed, the solvent is removed and the mixture is extracted and concentrated with toluene to obtain the compound shown in Formula I.

[0035] In another specific embodiment, the compound with the structure shown in Formula I can also be prepared by the following steps: under anhydrous and oxygen-free conditions, a ligand having the structure shown in Formula V, a rare earth alkyl compound, and an organic solvent are mixed and reacted to obtain a rare earth complex having the structure shown in Formula I. Specifically:

[0036] The ligands having the structure shown in Formula V are prepared in the same way as described above, and will not be repeated here;

[0037] Rare earth alkyl compounds include compounds containing rare earth elements and alkyl groups, wherein the alkyl group is selected from one of C1-C20 alkyl groups, C1-C20 alkylsilyl groups, and C1-C20 alkylamine groups, and further, the alkyl group is selected from one of -CH3, -CH2CH3, -CH(CH3)2, -C(CH3)3, -CH2SiMe2, -CH(SiMe3)2, and -CH2(o-C6H4(NMe2)); the organic solvent can be tetrahydrofuran, diethyl ether, toluene, pyridine, or ethylene glycol dimethyl ether.

[0038] The rare earth complex with the structure shown in Formula I prepared according to the above steps can be mixed with a co-catalyst and an organic solvent under anhydrous and oxygen-free conditions, and then styrene monomer can be added to carry out a polymerization reaction to obtain syndiotactic polystyrene.

[0039] The co-catalyst is one of the following: an aluminoxane compound, a composition of an aluminoxane compound and an alkylaluminum compound, or a composition of an organoboron salt and an alkylaluminum compound. Specifically:

[0040] The aluminum oxane compound is a modified or unmodified alkyl aluminum oxane, such as one of methyl aluminum oxane, trimethyl aluminum oxane, ethyl aluminum oxane, n-propyl aluminum oxane, and n-butyl aluminum oxane; the molar ratio of the aluminum oxane compound to the rare earth complex with the structure shown in Formula I is (1-2000):1, further, the molar ratio of the two is (1-100):1, and even further, the molar ratio of the two is (5-50):1.

[0041] The alkylaluminum compound is one of alkylaluminum, aluminum hydride, and alkylaluminum chloride, such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum, triphenylaluminum, tri-p-tolylaluminum, tribenzylaluminum, ethyl dibenzylaluminum, ethyl di-p-tolylaluminum, diethylbenzylaluminum, dimethylaluminum hydride, diethylaluminum hydride, di-n-propylaluminum hydride, di-n-butylaluminum hydride, diisopropylaluminum hydride, diisobutylaluminum hydride, dipentylaluminum hydride, dihexylaluminum hydride, dicyclohexylaluminum hydride, dioctylaluminum hydride, diphenylaluminum hydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride, ethyl benzylaluminum hydride, ethyl p-tolylaluminum hydride, dimethylaluminum chloride, etc. The aluminum compound is selected from the following: aluminum chloride, diethylaluminum chloride, di-n-propylaluminum chloride, di-n-butylaluminum chloride, diisopropylaluminum chloride, diisobutylaluminum chloride, dipentylaluminum chloride, dihexylaluminum chloride, dicyclohexylaluminum chloride, dioctylaluminum chloride, diphenylaluminum chloride, di-p-tolylaluminum chloride, dibenzylaluminum chloride, ethylbenzylaluminum chloride, and ethyl-p-tolylaluminum chloride; further, the alkylaluminum compound is methylaluminum, trimethylaluminum, triethylaluminum, triisobutylaluminum, diisobutylaluminum hydride, or diethylaluminum chloride; the molar ratio of the alkylaluminum compound to the rare earth complex with the structure shown in Formula I is (1-2000):1, further, the molar ratio of the two is (1-100):1, and even further, the molar ratio of the two is (5-50):1.

[0042] The organoboron salt is selected from one of [Ph3C][B(C6F5)4], [Ph3C][BPh4], [PhNMe2H][BPh4], [PhNMe2H][B(C6F5)4], BPh3, and B(C6F5)3. Further, the organoboron salt is selected from one of [Ph3C][B(C6F5)4], BPh3, and [Ph3C][BPh4]. The molar ratio of the organoboron salt to the rare earth complex with the structure shown in Formula I is (0.5-10.0):1. Further, the molar ratio of the two is (1.0-5.0):1. Even further, the molar ratio of the two is (1.0-3.0):1.

[0043] The organic solvent is a conventional solvent in this field, and can be a C5-C8 hydrocarbon solvent, specifically one or more of pentane, hexane, toluene, and xylene.

[0044] Under anhydrous and oxygen-free conditions, a rare earth complex with the structure shown in Formula I, a co-catalyst, and an organic solvent are mixed, and then styrene monomer is added to carry out a polymerization reaction to obtain syndiotactic polystyrene. In the catalyst, the molar concentration of the rare earth complex with the structure shown in Formula I is 0.2-2.0 mmol / L, and further, the molar concentration of the rare earth complex with the structure shown in Formula I is 0.5-1.8 mmol / L. The molar ratio of styrene monomer to the rare earth complex with the structure shown in Formula I is (200-10000):1, and further, the molar ratio is (500-8000):1. The polymerization temperature is -60-80℃, and further, the polymerization temperature is -30-50℃. The reaction time is 1-30 minutes, and further, the reaction time is 1-10 minutes. After the reaction is completed, syndiotactic polystyrene is obtained.

[0045] The rare earth complex with the structure shown in Formula I provided by this invention is an eta5-coordinated rare earth complex, a compound with a restricted geometric configuration. Due to the presence of eta5 coordination of cyclopentadienyl (cyclopentadienyl and its derivatives, indenyl and its derivatives, and fluorenyl and its derivatives) and the electron-withdrawing effect of the nitrogen-containing aromatic ring, as well as the presence of oxygen atoms coordinating to the central metal, which restricts the space of the central metal, it can selectively insert styrene monomers during the catalytic polymerization of syndiotactic styrene. Furthermore, by changing the feed amount, syndiotactic polystyrene with different molecular weights can be obtained. Experimental results show that the catalyst and catalyst combination provided by this invention can achieve highly active, highly syndiotactic polymerization of styrene, with a monomer conversion rate of up to 100% and an activity range of 520-19980 kgmol. Ln - 1 h -1 Between, the highest can reach 19980 kgmolLn -1 h -1 The syndiotacticity is between 80-100%, and can reach up to 100%. The number-average molecular weight of the prepared syndiotactic polystyrene is adjustable between 84,000 and 935,000 depending on the molar ratio of styrene monomer to catalyst. The molecular weight distribution is relatively narrow (1.21-1.52), and can reach as low as 1.21. The melting point is in the range of 266-273℃. The catalyst has good adaptability in the polymerization temperature range of -20-60℃. Attached Figure Description

[0046] Figure 1 The nuclear magnetic resonance hydrogen spectrum of the rare earth complex provided in Example 5 of this invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0048] Example 1

[0049] The rare earth complex provided in this embodiment has the structure shown in Formula 1.

[0050] The method for preparing rare earth complexes provided in this embodiment includes:

[0051] Under anhydrous and oxygen-free conditions, 0.5 mmol of the ligand with the structure shown in Formula V (R1 is indenyl, E is C, R2 and R3 are hydrogen, m = 1) and 0.5 mmol of Y(CH2SiMe3)2(THF)2 were stirred in tetrahydrofuran for 12 hours. The solvent was removed to obtain a rare earth complex (0.22 g) with the structure shown in Formula 1.

[0052] Example 2

[0053] The rare earth complex provided in this embodiment has the structure shown in Formula 2.

[0054] The method for preparing rare earth complexes provided in this embodiment includes:

[0055] Under anhydrous and oxygen-free conditions, 0.5 mmol of the ligand with the structure shown in Formula V (R1 is indenyl, E is C, R2 and R3 are hydrogen, m = 1) was stirred with 0.5 mmol of Lu(CH2SiMe3)2(THF)2 in tetrahydrofuran for 12 hours. The solvent was removed to obtain a rare earth complex (0.26 g) with the structure of Formula 2.

[0056] Example 3

[0057] The rare earth complex provided in this embodiment has the structure shown in Formula 3.

[0058] The method for preparing rare earth complexes provided in this embodiment includes:

[0059] Under anhydrous and oxygen-free conditions, 0.5 mmol of the ligand with the structure shown in Formula V (R1 is indenyl, E is C, R2 and R3 are hydrogen, m = 1) and 0.5 mmol Er(CH2SiMe3)2(THF)2 were stirred in tetrahydrofuran for 12 hours. The solvent was removed to obtain a rare earth complex (0.26 g) with the structure of Formula 3.

[0060] Example 4

[0061] The rare earth complex provided in this embodiment has the structure shown in Formula 4.

[0062] The method for preparing rare earth complexes provided in this embodiment includes:

[0063] Under anhydrous and oxygen-free conditions, 0.5 mmol of the ligand with the structure shown in Formula V (R1 is indenyl, E is C, R2 and R3 are hydrogen, m = 1) and 0.5 mmol of Gd(CH2SiMe3)2(THF)2 were stirred in tetrahydrofuran for 12 hours. The solvent was removed to obtain a rare earth complex (0.23 g) with the structure of Formula 4.

[0064] Example 5

[0065] The rare earth complex provided in this embodiment has the structure shown in Formula 5.

[0066] The method for preparing rare earth complexes provided in this embodiment includes:

[0067] Under anhydrous and oxygen-free conditions, 0.5 mmol of the ligand with the structure shown in Formula V (R1 is fluorenyl, E is C, R2 and R3 are hydrogen, m = 1) and 0.5 mmol of Y(CH2SiMe3)2(THF)2 were stirred in tetrahydrofuran for 12 hours. The solvent was removed to obtain a rare earth complex (0.25 g) with the structure of Formula 5.

[0068] The prepared rare earth complexes were analyzed by proton nuclear magnetic resonance spectroscopy, such as... Figure 1 As shown.

[0069] Example 6

[0070] The rare earth complex provided in this embodiment has the structure shown in Formula 6.

[0071] The method for preparing rare earth complexes provided in this embodiment includes:

[0072] Under anhydrous and oxygen-free conditions, 0.5 mmol of the ligand with the structure shown in Formula V (R1 is fluorenyl, E is C, R2 and R3 are hydrogen, m = 1) and 0.5 mmol of Lu(CH2SiMe3)2(THF)2 were stirred in tetrahydrofuran for 12 hours. The solvent was removed to obtain a rare earth complex (0.27 g) with the structure of Formula 6.

[0073] Example 7

[0074] The rare earth complex provided in this embodiment has the structure shown in Formula 7.

[0075] The method for preparing rare earth complexes provided in this embodiment includes:

[0076] Step 1: Under anhydrous and oxygen-free conditions, a tetrahydrofuran solution of 0.5 mmol of the ligand with the structure shown in Formula V (R1 is indenyl, E is C, R2 and R3 are methyl, m=1) was reacted with n-butyllithium (0.32 mL, 1.6 M n-hexane solution) at 0 °C for 1 hour to obtain the lithium salt of the ligand in the first reaction mixture.

[0077] Step 2: At room temperature, the above lithium salt tetrahydrofuran solution was added dropwise to a tetrahydrofuran suspension of LaCl3 (0.5 mmol), and the reaction was carried out for 4 hours to obtain the second reaction product;

[0078] Step 3: Add 1.0 mmol Li(O-CH2C6H4NMe2) to the second reaction product and react for 12 hours. After removing the solvent and extracting and concentrating with toluene, a rare earth complex with the structure of Formula 7 (0.24 g) is obtained.

[0079] Example 8

[0080] The rare earth complex provided in this embodiment has the structure shown in Formula 8.

[0081] The preparation method of the rare earth complex provided in this embodiment can be referred to in Embodiment 7, except that R1 in the ligand of the structure shown in Formula V is an indenyl group, and a rare earth complex with the structure of Formula 8 (0.27 g) is obtained.

[0082] Example 9

[0083] The rare earth complex provided in this embodiment has the structure shown in Formula 9.

[0084] The method for preparing the rare earth complex provided in this embodiment can be referred to in Example 7, except that R1 in the ligand of the structure shown in Formula V is 3,6-di-tert-butylfluorenyl, and R2 and R3 are hydrogen, so as to obtain a rare earth complex (0.25g) with the structure of Formula 9.

[0085] Example 10

[0086] The rare earth complex provided in this embodiment has the structure shown in Formula 10.

[0087] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 7, except that R1 in the ligand of the structure shown in Formula V is fluorenyl and E is Si; in step 2, it is reacted with a tetrahydrofuran suspension of YCl3 to obtain a rare earth complex (0.24g) with the structure of Formula 10.

[0088] Example 11

[0089] The rare earth complex provided in this embodiment has the structure shown in Formula 11.

[0090] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 7, except that R1 in the ligand of the structure shown in Formula V is fluorenyl, and R2 and R3 are hydrogen; in step 2, it is reacted with the tetrahydrofuran suspension of YCl3 to obtain a rare earth complex (0.25g) with the structure of Formula 11.

[0091] Example 12

[0092] The rare earth complex provided in this embodiment has the structure shown in Formula 12.

[0093] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 7. The difference is that R1 in the ligand of the structure shown in Formula V is fluorenyl, and R2 and R3 are hydrogen. In step 2, it is reacted with a tetrahydrofuran suspension of LuCl3 to obtain a rare earth complex (0.27g) with the structure of Formula 12.

[0094] Example 13

[0095] The rare earth complex provided in this embodiment has the structure shown in Formula 13.

[0096] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 7, except that R1 in the ligand with the structure shown in Formula V is fluorenyl, E is C, and R2 and R3 are hydrogen; in step 2, it reacts with the tetrahydrofuran suspension of YCl3; in step 3, CH2CHCH2MgBr is added to the second reaction product to obtain the rare earth complex with the structure of Formula 13 (0.16g, Yield: 69%).

[0097] Example 14

[0098] The rare earth complex provided in this embodiment has the structure shown in Formula 14.

[0099] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 13. The difference is that R1 in the ligand with the structure shown in Formula V is an indenyl group, and in step 2, it is reacted with a tetrahydrofuran suspension of GdCl3 to obtain a rare earth complex (0.11g) with the structure of Formula 14.

[0100] Example 15

[0101] The rare earth complex provided in this embodiment has the structure shown in Formula 15.

[0102] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 13. The difference is that R1 in the ligand with the structure shown in Formula V is an indenyl group, and in step 2, it is reacted with a tetrahydrofuran suspension of LaCl3 to obtain a rare earth complex (0.19g) with the structure of Formula 15.

[0103] Example 16

[0104] The rare earth complex provided in this embodiment has the structure shown in Formula 16.

[0105] The preparation of the rare earth complex provided in this embodiment can be referred to in Example 13, except that R1 in the ligand with the structure shown in Formula V is an indenyl group, and in step 2 it is reacted with a tetrahydrofuran suspension of YCl3 to obtain a rare earth complex (0.17g) with the structure of Formula 16.

[0106] Example 17

[0107] The rare earth complex provided in this embodiment has the structure shown in Formula 17.

[0108] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 13. The difference is that in the ligand with the structure shown in Formula V, R1 is an indenyl group, and in step 2, it is reacted with a tetrahydrofuran suspension of LuCl3 to obtain a rare earth complex (0.20 g) with the structure of Formula 17.

[0109] Example 18

[0110] The rare earth complex provided in this embodiment has the structure shown in Formula 18.

[0111] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 7. The difference is that in the ligand with the structure shown in Formula V, R1 is fluorenyl, and R2 and R3 are hydrogen. In step 2, it is reacted with a tetrahydrofuran suspension of YCl3. In step 3, NaBH4 is added to the second reaction product to obtain a rare earth complex (0.12g) with the structure of Formula 18.

[0112] Example 19

[0113] The rare earth complex provided in this embodiment has the structure shown in Formula 19.

[0114] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 18. The difference is that in the ligand with the structure shown in Formula V, R1 is tetramethylcyclopentadienyl. In step 2, it is reacted with a tetrahydrofuran suspension of TbCl3 to obtain a rare earth complex (0.08g) with the structure of Formula 19.

[0115] Example 20

[0116] The rare earth complex provided in this embodiment has the structure shown in Formula 20.

[0117] The preparation method of the rare earth complex provided in this embodiment can be referred to in Example 18. The difference is that in the ligand with the structure shown in Formula V, R1 is tetramethylcyclopentadienyl. In step 2, it is reacted with a tetrahydrofuran suspension of LaCl3 to obtain a rare earth complex (0.16g) with the structure of Formula 20.

[0118] The structural formulas of the rare earth complexes involved in Examples 1-20 are shown in Table 1:

[0119] Table 1. Structural formulas of the rare earth complexes provided in Examples 1-20

[0120]

[0121]

[0122] Catalysts were prepared from the rare earth complexes provided in Examples 1-20:

[0123] Preparation of catalyst combination 1: At 25°C, 10 μmol of the rare earth complex shown in Formula 1, 10 μmol of [Ph3C][B(C6F5)4], 50 μmol of triisobutylaluminum, and toluene solvent were added to a 25 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 2.0 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 1.

[0124] Preparation of catalyst combination 2: At 25°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 2 was obtained.

[0125] Preparation of catalyst combination 3: At 0°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 3 was obtained.

[0126] Preparation of catalyst combination 4: At -60℃, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 4 was obtained.

[0127] Preparation of catalyst combination 5: At 40°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 5 was obtained.

[0128] Preparation of catalyst combination 6: At 80°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 6 was obtained.

[0129] Preparation of catalyst combination 7: At 25°C, 10 μmol of the rare earth complex shown in Formula 2, 20 μmol of dry methylaluminoxane, 100 μmol of trimethylaluminum, and xylene solvent were added to a 25 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 7 was obtained.

[0130] Preparation of catalyst combination 8: At 25°C, 10 μmol of the rare earth complex shown in Formula 3, 10 μmol of [PhNMe2H][B(C6F5)4], 200 μmol of triethylaluminum, and toluene solvent were added to a 25 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1After reacting for 2 minutes, catalyst combination 8 was obtained.

[0131] Preparation of catalyst combination 9: At -40℃, 10 μmol of the rare earth complex shown in Formula 4, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 50 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 9 was obtained.

[0132] Preparation of catalyst combination 10: At 25°C, 10 μmol of the rare earth complex shown in Formula 5, 100 μmol of methylaluminoxane, 100 μmol of triethylaluminum, and toluene solvent were added to a 250 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 10.

[0133] Preparation of catalyst combination 11: At 25°C, 10 μmol of the rare earth complex shown in Formula 5, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 50 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.5 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 11 was obtained.

[0134] Preparation of catalyst combination 12: At 60°C, 10 μmol of the rare earth complex shown in Formula 6, 10 μmol of [PhNMe2H][B(C6F5)4], 1 mmol of triisobutylaluminum, and toluene solvent were added to a 25 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 12 was obtained.

[0135] Preparation of catalyst combination 13: At 0°C, 10 μmol of the rare earth complex shown in Formula 7, 20 μmol of methylaluminoxane, and pentane solvent were added to 100 ml of anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 13 was obtained.

[0136] Preparation of catalyst combination 14: At 25°C, 10 μmol of the rare earth complex shown in Formula 8, 1000 μmol of methylaluminoxane, 300 μmol of trimethylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹.–1 The reaction was carried out for 2 minutes to obtain catalyst combination 14.

[0137] Preparation of catalyst combination 15: At 40°C, 10 μmol of the rare earth complex shown in Formula 9, 50 μmol of trimethylaluminoxane, 10 mmol of triisobutylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 15.

[0138] Preparation of catalyst combination 16: At 25°C, 10 μmol of the rare earth complex shown in Formula 10, 10 μmol of [Ph3C][BPh4], 10 mmol of triisobutylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 16.

[0139] Preparation of catalyst combination 17: At 0°C, 10 μmol of the rare earth complex shown in Formula 11, 20 μmol of [PhNMe2H][BPh4], 5 mmol of triisobutylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 17 was obtained.

[0140] Preparation of catalyst combination 18: At 80°C, 10 μmol of the rare earth complex shown in Formula 12, 10 μmol of B(C6F5)3, 100 μmol of triisobutylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 18.

[0141] Preparation of catalyst combination 19: At 25°C, 10 μmol of the rare earth complex shown in Formula 13, 10 mmol of methylaluminoxane, 500 μmol of triethylaluminum, and xylene solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.33 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 19 was obtained.

[0142] Preparation of catalyst combination 20: At 0°C, 10 μmol of the rare earth complex shown in Formula 14, 10 μmol of [Ph3C][B(C6F5)4], 500 μmol of triisobutylaluminum, and xylene solvent were added to a 50 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 20.

[0143] Preparation of catalyst combination 21: At 40°C, 10 μmol of the rare earth complex shown in Formula 15, 10 μmol of [PhNMe2H][B(C6F5)4], 1 mmol of trimethylaluminum, and toluene solvent were added to a 50 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.33 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 21 was obtained.

[0144] Preparation of catalyst combination 22: At 25°C, 10 μmol of the rare earth complex shown in Formula 16, 10 μmol of B(C6F5)3, 10 mmol of trimethylaluminum, and xylene solvent were added to a 25 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 22 was obtained.

[0145] Preparation of catalyst combination 23: At –60°C, 10 μmol of the rare earth complex shown in Formula 17, 10 μmol of [Ph3C][BPh4], 1 mmol of triisobutylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 23 was obtained.

[0146] Preparation of catalyst combination 24: At 80°C, 10 μmol of the rare earth complex shown in Formula 17, 10 μmol of [Ph3C][BPh4], 1 mmol of triisobutylaluminum, and toluene solvent were added to 100 ml of anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 24.

[0147] Preparation of catalyst combination 25: At 0°C, 10 μmol of the rare earth complex shown in Formula 18, 100 μmol of methylaluminoxane, 5 mmol of trimethylaluminum, and pentane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1The reaction was carried out for 2 minutes to obtain catalyst combination 25.

[0148] Preparation of catalyst combination 26: At 25°C, 10 μmol of the rare earth complex shown in Formula 18, 100 μmol of methylaluminoxane, 5 mmol of trimethylaluminum, and hexane solvent were added to a 50 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 26.

[0149] Preparation of catalyst combination 27: At 80°C, 10 μmol of the rare earth complex shown in Formula 18, 10 μmol of [Ph3C][B(C6F5)4], 20 μmol of diisobutylaluminum hydride, and toluene solvent were added to a 25 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 27.

[0150] Preparation of catalyst combination 28: At 60°C, 10 μmol of the rare earth complex shown in Formula 18, 10 μmol of BPh3, 200 μmol of diethylaluminum chloride, and toluene solvent were added to a 25 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.5 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 28.

[0151] Preparation of catalyst combination 29: At 25°C, 10 μmol of the rare earth complex shown in Formula 19, 20 μmol of [Ph3C][BPh4], 200 μmol of diethylaluminum chloride, and hexane solvent were added to a 25 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.28 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 29 was obtained.

[0152] Preparation of catalyst combination 30: At 40°C, 10 μmol of the rare earth complex shown in Formula 20, 100 μmol of dry methylaluminoxane, 500 μmol of diisobutylaluminum hydride, and toluene solvent were added to a 25 ml anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.5 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 30.

[0153] Preparation of catalyst combination 31: At 0°C, 10 μmol of the rare earth complex shown in Formula 20, 10 μmol of [Ph3C][B(C6F5)4], 500 μmol of triisobutylaluminum, and pentane solvent were added to a 50 ml polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, coordination catalysis system 31 was obtained.

[0154] Preparation of catalyst combination 32: At -60℃, 10 μmol of the rare earth complex shown in Formula 20, 10 μmol of [PhNMe2H][BPh4], 2 mmol of trimethylaluminum, and pentane solvent were added to a 50 ml polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 32 was obtained.

[0155] Syndiotactic polystyrene was prepared by catalytic synthesis of styrene monomer using catalyst combination 1-32. The catalytic method included: placing styrene monomer (St) and 5 ml of toluene solution (Ln) of catalyst combination in a polymerization flask that had been treated to be anhydrous and oxygen-free according to the molar ratio shown in Table 2; carrying out the polymerization reaction at the polymerization temperature shown in Table 2; after the polymerization time was completed, adding 2 ml of ethanol solution with a volume concentration of 10% hydrochloric acid to terminate the polymerization reaction; and pouring the reaction solution into 100 ml of methanol for precipitation to obtain syndiotactic polystyrene.

[0156] The obtained syndiotactic polystyrene was dried in a vacuum drying oven for 48 hours to obtain syndiotactic polystyrene of constant weight. The weight was then calculated, and the conversion rate (%) was calculated. Conversion rate (%) = polymer produced / total monomers. The polymerization activity (mol) was also calculated. Y ·h) –1 = Amount of polymer / catalyst generated, measured by carbon NMR (carbon NMR) 1 The syndiotacticity of syndiotactic polystyrene was obtained by ¹³C NMR analysis, and the molecular weight and molecular weight distribution of syndiotactic polystyrene were obtained by GPC analysis. w / M n The melting point (°C) of syndiotactic polystyrene was obtained by DSC analysis.

[0157] The syndiotactic polystyrene obtained by catalyst combination 1-32 was tested using the above method, and the test results are shown in Table 2:

[0158] Table 2 shows the catalytic reaction parameters provided by catalyst combinations 1-32 and the test results of the catalytic product, syndiotactic polystyrene.

[0159]

[0160]

[0161] As shown in Table 2, the catalyst combination provided by this invention can achieve highly active, highly syndiotactic polymerization of styrene, with a monomer conversion rate of up to 100% and an activity range of 520-19980 kgmol. Ln -1 h -1 Between, the highest can reach 19980 kgmol Ln -1 h -1 The syndiotacticity is between 80-100%, and can reach up to 100%. The number-average molecular weight of the prepared syndiotactic polystyrene is adjustable between 84,000 and 935,000 depending on the molar ratio of styrene monomer to catalyst. The molecular weight distribution is relatively narrow (1.21-1.52), and can reach as low as 1.21. The melting point is in the range of 266-273℃. The catalyst has good adaptability in the polymerization temperature range of -20-60℃.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A catalyst for catalyzing syndiotactic polystyrene, characterized in that, The catalyst comprises a rare earth complex having the structure shown in Formula I: Formula I In Formula I, R1 is selected from one of cyclopentadienyl and its derivatives, indenyl and its derivatives, and fluorenyl and its derivatives; R2 and R3 are independently selected from one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl, and 2,6-ditert-butylphenyl; R4 is selected from one of C1-C20 alkyl, C1-C20 alkylsilyl, C1-C20 alkylamino, borohydrin, and allyl; Ln is selected from one of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; E is one of C, Si, and Ge; Y is selected from one of tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether, and toluene; m = 1 or 2; n = 0, 1, or 2. The catalyst further includes a co-catalyst, which is one or more of the following: an aluminoxane compound, a composition of an aluminoxane compound and an alkylaluminum compound, or a composition of an organoboron salt and an alkylaluminum compound; The catalyst further includes an organic solvent, wherein the organic solvent is a C5-C8 hydrocarbon organic solvent; In the catalyst, the molar concentration of the rare earth complex is 0.2-2.0 mmol / L.

2. The catalyst according to claim 1, characterized in that, R1 is selected from one or more of indene and its derivatives, fluorene and its derivatives.

3. The catalyst according to claim 1, characterized in that, R2 and R3 are each independently selected from one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl, and 2,6-ditert-butylphenyl.

4. The catalyst according to claim 1, characterized in that, The Ln is one of Sc, Y, La, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

5. The catalyst according to claim 1, characterized in that, R4 is a C1-C20 alkyl, C1-C20 alkylsilyl, borohydride, or allyl group.

6. The catalyst according to claim 1, characterized in that, Y stands for tetrahydrofuran.

7. The catalyst according to claim 1, characterized in that, In the catalyst, the molar concentration of the rare earth complex is 0.5-1.8 mmol / L.

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