Diimine ligand, late transition metal polyethylene wax catalyst and preparation method and application of late transition metal polyethylene wax catalyst

Abstract

The invention provides a diimine ligand with a general formula structure as shown in a formula L. In the formula, R1-R8 are respectively and independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C12 aryl or halogen. The diimine ligand is prepared from a 1, 2-diketone compound with an isatin skeleton and large-steric-hindrance aromatic amine with an aniline skeleton through acid catalysis. The invention also provides a late transition metal polyethylene wax catalyst adopting coordination of the diimine ligand and a late transition metal salt, the catalyst has high catalytic activity in a wide temperature range and excellent high-temperature stability, the late transition metal polyethylene wax catalyst is applied to preparation of polyethylene wax, and the preparation cost of the polyethylene wax is greatly reduced. The product has the characteristics of narrow molecular weight distribution, low branching degree, good chemical and physical properties and the like. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of polyethylene wax preparation, in particular to a diimine ligand, a late transition metal polyethylene wax catalyst containing the ligand, and a preparation method of the diimine ligand. Background Art

[0002] Polyethylene wax (PE-wax) is a polymer material formed by the polymerization of ethylene monomers. It has a white granular / flaky structure and a molecular weight range of 1,000 to 10,000. The lower molecular weight gives polyethylene wax different properties from conventional polyethylene. Polyethylene wax has the characteristics of low viscosity, high softening point and high hardness, which makes it widely used in the field of plastic processing. In addition, polyethylene wax has the characteristics of non-toxicity, thermal stability and low volatility, which expands the application of polyethylene wax in extreme environments such as low temperature and high heat. Finally, polyethylene wax has excellent dispersing ability for pigments, which not only promotes the uniform distribution of pigments, but also enhances the external lubricity of the material, provides excellent lubrication effect inside the material, and significantly improves the production efficiency of dye processing. Therefore, polyethylene wax has become a high-end material in polyethylene products.

[0003] At present, the following three methods are mainly used in the industry to prepare polyethylene wax: by-product refining, polyethylene cracking, and direct polymerization of ethylene. Among them, the by-product refining process is to purify and separate the oligomer components in the previous polyethylene production, while the polyethylene cracking process is to obtain polyethylene wax by cracking high molecular weight polyethylene through catalytic degradation. The polyethylene wax products obtained by the above two methods have a wide molecular weight distribution, many impurities, and poor performance, which is difficult to meet the needs of modern high-end fields. Only the various indicators of polyethylene wax generated by polymerization can meet the needs, and the polymerization method also meets the requirements of modern chemical industry for efficient atomic utilization and green production. However, the generation of polyethylene wax from ethylene is a polymerization reaction, and its reaction degree is difficult to control. The catalyst is the core of the polymerization reaction, and it is necessary to design and prepare catalysts with better catalytic activity for production.

[0004] Late transition metal catalysts are metal organic catalysts formed by the coordination of late transition metals such as Fe, Co, Ni, Pd and ligands containing elements such as N, O, P, etc. They are prone to undergo β-H elimination reactions to produce low molecular weight polymers. Therefore, compared with Ziegler-Natta (ZN) catalysts that mainly produce high-molecular polyethylene and metallocene catalysts with high costs, late transition metal catalysts have unique catalytic properties for ethylene polymerization and are catalysts with industrial potential for the preparation of polyethylene wax.

[0005] At present, it is difficult to balance the catalytic activity and thermal stability of late transition metal catalysts in the production process of polyethylene wax. Increasing the temperature can accelerate the reaction rate, but as the reaction temperature increases, the late transition metal catalyst will lose its activity. The document "Mechanistic Studies of Pd(II)-α-Diimine-Catalyzed Olefin Polymerizations [J]. J Am Chem Soc, 2000, 122 (28): 6686-6700" proposes that the reason for the poor thermal stability of late transition metal catalysts is that the NC bond in the ligand rotates, causing the metal active center to deactivate. Based on this deactivation mechanism, people mainly focus on improving the rigid structure and steric hindrance of the ligand to improve its thermal stability. Patent CN110092744A discloses a highly thermally stable transition metal complex containing tert-butyl asymmetric diiminopyridine for preparing polyethylene wax. The complex can be used as an ethylene polymerization catalyst, has a single catalytic active center, high catalytic activity and good thermal stability. However, the molecular weight distribution of the obtained polyethylene wax is relatively wide, especially the amount of co-catalyst used is large (Al / Fe≥1000), which hinders its practical application.

[0006] How to design and synthesize a late transition metal catalyst with a stable rigid structure, which can improve thermal stability without reducing catalytic activity, and be used for ethylene polymerization to produce high-quality polyethylene wax products still requires further research. Summary of the invention

[0007] The present invention aims to provide a diimine ligand, a late transition metal polyethylene wax catalyst containing the ligand, a preparation method of the diimine ligand, and application of the diimine ligand in the preparation of polyethylene wax, so as to solve the above-mentioned defects existing in the background technology.

[0008] The present invention is achieved by adopting the following technical solutions:

[0009] The first aspect of the present invention relates to a diimide ligand having a general structure as shown in Formula L, wherein R1 to R8 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen.

[0010] The C1-C6 alkyl group includes a linear or branched alkyl group, such as but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl or hexyl, preferably methyl, isopropyl or tert-butyl.

[0011] The C1-C6 alkoxy group includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, pentyloxy or hexyloxy.

[0012]

[0013] The C6-C 12 Aryl is a monovalent aromatic carbocyclic ring system having at least one aromatic ring or multiple condensed rings in which at least one ring is aromatic, for example, it can be selected from phenyl, naphthyl or biphenyl.

[0014] As a preferred technical solution, at least one of R1 to R5 is an electron donating group, specifically selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl; further preferably, among R1 to R5, at least one of R1, R2, R5 is selected from C1-C6 alkyl, and the rest are H.

[0015] As a preferred technical solution, at least one of R6, R7, and R8 is an electron-donating group, specifically selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl.

[0016] Furthermore, when R6 is an electron-donating group, it is preferably methyl, isopropyl or methoxy; when R7 is an electron-donating group, it is preferably methyl, isopropyl or methoxy; and when R8 is an electron-donating group, it is preferably methyl, isopropyl or tert-butyl.

[0017] As a preferred embodiment of the present invention, the diimine ligand is selected from any one of the following diimine ligand compounds of Formula L1 to Formula L10:

[0018]

[0019]

[0020]

[0021] The diimine ligand of the formula L structure of the present invention uses indigo carmine and its derivatives as the skeleton. Indigo carmine has a six-membered ring and an N-hetero five-membered ring structure, which has a certain rigidity and improves the thermal stability of the late transition metal catalyst when coordinated with the metal to form a catalyst. In addition, indigo carmine has an N-hetero five-membered ring, and the N atom has a stronger electronegativity than the C atom, and the lone pair of electrons on the N atom can be conjugated with the benzene ring and the diimine structure to further optimize the electronic structure of the catalyst.

[0022] The second aspect of the present invention relates to a method for preparing the above-mentioned diimine ligand, specifically, the diimine ligand is prepared by acid catalysis using a 1,2-diketone compound of the general structure shown in Formula I and a large sterically hindered aromatic amine of the general structure shown in Formula II as raw materials. The specific reaction formula is as follows:

[0023]

[0024] The 1,2-diketone compound has isatin as the skeleton, and R1 to R5 can be the same or different groups, independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen. Preferably, at least one of R1 to R5 is an electron donating group, specifically selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl. Further preferably, among R1 to R5, at least one of R1, R2, and R5 is an electron donating group, and the rest are H. More preferably, R2 is an electron donating group, and the rest are H. As a preferred embodiment, the 1,2-diketone compound is an isatin derivative in which the R2 substituent is methyl, methoxy or isopropyl, and R1, R3, R4, and R5 are H.

[0025] The bulky hindered aromatic amines have aniline as the skeleton, including but not limited to benzidine, naphthylamine, anthraceneamine, condensed ring aromatic amines and other similar structures. R6 to R8 can be the same or different groups, independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen. Preferably, the bulky sterically hindered aromatic amine is aniline, or an aniline derivative in which at least one of R6, R7, and R8 is not H. Further preferably, at least one of R6, R7, and R8 is an aniline derivative in which at least one of the electron-donating groups is selected, i.e., at least one of R6, R7, and R8 is selected from C1-C6 alkyl, C1-C6 alkoxy, or phenyl. More preferably, R6 is methyl, isopropyl, or methoxy, and / or R7 is methyl, isopropyl, or methoxy, and / or R8 is methyl, isopropyl, or tert-butyl.

[0026] As a preferred technical solution, the preparation method of the diimine ligand of the present invention comprises the following steps: the 1,2-diketone compound and the bulky sterically hindered aromatic amine are dissolved in an organic non-protonic polar solvent at a molar ratio of 1:2-2.5, a non-oxidizing organic strong acid is added as a catalyst, and the mixture is fully reacted at 100-200°C, and the solvent is removed from the reaction mixture and purified to obtain the diimine ligand.

[0027] The organic aprotic polar solvent can be a commonly used solvent in the art, such as a mixture of toluene and DMSO. The non-oxidizing organic strong acid can be a commonly used solvent organic strong acid substance in the art, such as p-toluenesulfonic acid. The reaction temperature is preferably 120-160° C., and the reaction time is generally between 12-36 hours. The solvent can be removed by conventional methods in the art, such as rotary evaporation. The product can be purified by conventional methods in the art, such as by recrystallization.

[0028] The third aspect of the present invention relates to a late transition metal polyethylene wax catalyst, specifically a coordination compound formed by the diimine ligand having the general structure shown in Formula L and a late transition metal salt.

[0029] The late transition metal is selected from Fe, Co, Ni or Pd. The late transition metal salt can be a halide of the late transition metal, such as a chloride or a bromide, including but not limited to ferric chloride, cobalt chloride, nickel bromide, nickel chloride, and the like.

[0030] The inventors have found that the late transition metal polyethylene wax catalyst obtained by using indigo carmine as the skeleton unexpectedly has high catalytic activity in a wide temperature range, especially excellent high temperature stability. The polyethylene wax product prepared by using this catalyst has the characteristics of narrow molecular weight distribution, low branching degree, good chemical and physical properties, etc. The specific mechanism is not very clear at present, which may be due to the following reasons: on the one hand, the benzene ring structure of indigo carmine can produce a conjugated effect with aniline compounds to improve the electronic structure of the catalyst; on the other hand, compared with other aromatic compounds, indigo carmine has an N-hetero five-membered ring, and the N atom has a different electronegativity from the C atom, which further improves the electronic structure of the catalyst; in addition, the indigo carmine structure is rigid, which hinders the rotation of the NC bond to a certain extent, and can improve the thermal stability of the catalyst.

[0031] Preferably, the late transition metal polyethylene wax catalyst is a nickel metal polyethylene wax catalyst having the general structure shown in Formula C:

[0032]

[0033] Wherein X is chlorine or bromine.

[0034] The late transition metal polyethylene wax catalyst can be prepared by a conventional method for synthesizing coordination compounds. Taking the nickel metal polyethylene wax catalyst of the general structure shown in Formula C as an example, the following method can be used:

[0035] Under anhydrous and oxygen-free conditions, the diimine ligand and anhydrous nickel salt are added to a reaction vessel in which a solvent is added, and the reaction is carried out at 15-80° C. for 12-36 hours, wherein the molar ratio of the diimine ligand to the anhydrous nickel salt is 2-3:1. After the reaction is completed, the nickel metal polyethylene wax catalyst is obtained by post-treatment. The reaction formula of the above synthesis is as follows:

[0036]

[0037] The solvent is not particularly limited, for example, ultra-dry acetonitrile is used. The nickel salt is nickel chloride or nickel bromide, preferably nickel chloride. The post-treatment includes cooling the product to room temperature, concentrating by reduced evaporation, filtering out the solvent, and washing with dry n-hexane for multiple times.

[0038] The late transition metal polyethylene wax catalyst of the present invention is used for producing polyethylene wax by ethylene polymerization. Under the action of a co-catalyst, polyethylene wax is obtained at a relatively low pressure and with high catalytic activity. The obtained polyethylene wax has a narrow distribution, a low degree of branching, and excellent chemical and physical properties and can meet the requirements.

[0039] When producing polyethylene wax, the ethylene pressure is 0.1-10 MPa, preferably, the ethylene pressure is 0.1-2 MPa; more preferably, the ethylene pressure is 0.1-0.5 MPa.

[0040] The selected co-catalyst is mainly alkylaluminoxane, and more preferably methylaluminoxane, modified methylaluminoxane or isobutylaluminoxane as the co-catalyst. The molar ratio of the late transition metal polyethylene wax catalyst to the co-catalyst is 1:400-600.

[0041] The solvent used in the polymerization process is mainly an inert solvent, mainly including chain alkanes and cycloalkanes with a boiling point not exceeding 120° C. and benzene aromatic derivatives. Preferably, benzene aromatic derivatives that are liquid at room temperature, have low viscosity, a boiling point not exceeding 110° C. and low solubility in polyethylene wax are used, such as toluene, xylene, chlorobenzene, etc. as solvents.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention designs and synthesizes a diimine ligand with indigo carmine as a skeleton, thereby obtaining a late transition metal catalyst containing the diimine ligand. The indigo carmine skeleton has higher rigidity and more suitable electron cloud density than the traditional 1,2-diketone structure, which can greatly improve the catalytic performance and stability of the catalyst. The synthesized late transition metal catalyst can have high catalytic activity in a wide range of 45-120°C, especially excellent high temperature stability. When the reaction temperature is 120°C, the catalyst still has a catalytic activity of 6.35×10 6 g / mol·h catalytic activity. When used to prepare polyethylene wax, the polyethylene wax product has the characteristics of narrow molecular weight distribution (PDI <1.5), low branching degree (<50 / 1000C), good chemical and physical properties, etc. DETAILED DESCRIPTION

[0044] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only used as examples, but are not used to limit the scope of the present invention. Those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalent solutions, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0045] The instruments or reagents in the examples of the present invention that do not indicate the manufacturer are all conventional commercial instruments or reagents. The main reagents used in the examples are as follows (taking R1-methyl substituted Dianhong as an example, it means that R1 is methyl and the other R2 to R5 groups are all H):

[0046] R1-Methyl substituted Dianhong (CAS:2058-74-4Sigma-Aldrich)

[0047] R2-Methyl substituted Dianhong (CAS: 1127-59-9 Leyan Reagent)

[0048] R5-Methyl substituted Dianhong (CAS:1127-59-9Mecklin)

[0049] R2-isopropyl substituted isatin (CAS: 66232-59-5)

[0050] Sodium sulfate (CAS:7757-82-6Sigma-Aldrich)

[0051] Chloral hydrate (CAS:302-17-0Sigma-Aldrich)

[0052] Hydroxylamine sulfate (CAS:10039-54-0Sigma-Aldrich)

[0053] Concentrated hydrochloric acid (CAS:7647-01-0Sigma-Aldrich)

[0054] m-Isopropylaniline (CAS:108-44-1Aladdin)

[0055] R6-Methyl substituted aniline (CAS: 87-62-7 Sigma-Aldrich)

[0056] R6-Bromo-substituted aniline (CAS:608-3-0Sigma-Aldrich)

[0057] R6-Isopropyl substituted aniline (CAS:24544-04-5Sigma-Aldrich)

[0058] R7-Methyl substituted aniline (CAS:108-69-0Sigma-Aldrich)

[0059] R8-Methyl substituted aniline (CAS:106-49-0Sigma-Aldrich)

[0060] 2,6-Diacetylpyridine (CAS:1129-30-2Sigma-Aldrich)

[0061] Salicylaldehyde (CAS:90-02-8Sigma-Aldrich)

[0062] Bis(triphenylphosphine)nickel(II) chloride (CAS:14264-16-5Sigma-Aldrich)

[0063] Tetrahydrofuran (CAS:109-99-9Sigma-Aldrich)

[0064] n-Hexane (CAS:110-54-3Sigma-Aldrich),

[0065] Ether (CAS: 60-29-7 Aladdin)

[0066] Concentrated sulfuric acid (CAS:7664-39-9Aladdin)

[0067] Toluene (CAS:108-88-3Sigma-Aldrich)

[0068] Dimethyl sulfoxide (CAS: 67-68-5 Sigma-Aldrich)

[0069] Ethanol (CAS: 64-17-5 Sigma-Aldrich)

[0070] Acetonitrile (CAS:75-05-8Sigma-Aldrich)

[0071] p-Toluenesulfonic acid (CAS:6192-52-5Sigma-Aldrich)

[0072] Unless otherwise specified, all solvents involved in the present invention need to be treated to remove water.

[0073] Among them, the synthesis steps and reaction formula of R2-isopropyl substituted isatin are as follows:

[0074]

[0075] A mixture of sodium sulfate (0.915 mol), distilled water (120 ml), chloral hydrate (0.109 mol), hydroxylamine sulfate (0.079 mol), 8.6 ml concentrated hydrochloric acid (37%) and m-isopropylaniline (0.1 mol) dissolved in 60 ml distilled water was mixed and gradually heated to 70 ° C. Subsequently, 100 ml of ethanol was added and the mixture was heated to reflux. After reacting for 1 h, the mixture was poured into ice water, and the solid of 3-isopropylisonitrosoacetanilide was collected by filtration and washed with water. The final yield of 3-isopropylisonitrosoacetanilide was 81%. Subsequently, 3-isopropylisonitrosoacetanilide (17 mmol) was slowly added to concentrated sulfuric acid (9 ml) under magnetic stirring at room temperature. After reacting for 15 minutes, the reaction mixture was poured into crushed ice and filtered to obtain a mixture of products 1 and 2. Subsequently, the crystallization method was used to purify the product 2: the mixture of products 1 and 2 was dissolved in a very small amount of DMSO, and the DMSO was slowly dripped into a large amount of n-hexane solution. Due to the difference in polarity, the solid product 1 was precipitated. The filtration was repeated many times, and finally the product 2 dissolved in n-hexane was rotary evaporated and washed with distilled water. The final yield of R2-isopropyl substituted isatin was 45%.

[0076] Examples 1-10

[0077] Preparation of ligands L1-L10.

[0078] Ligands L1-L10 were prepared according to the 1,2-diketone compounds and bulky sterically hindered aromatic amines listed in Table 1.

[0079] Table 1 Raw materials and structural formulas of ligands L1 to L10

[0080]

[0081]

[0082]

[0083] Taking ligand L1 as an example, the synthesis steps and reaction formula are as follows:

[0084]

[0085] In a 250ml three-necked flask, add 100ml of mixed organic solvent (mixture of toluene and DMSO, wherein V 甲苯 :V DMSO =9:1), then R1-methyl substituted isatin (10 mmol) and aniline (21 mmol) were added and mixed evenly, then catalytic p-toluenesulfonic acid (10 μmol) was added, and the mixture was refluxed at 120°C for 24 hours. After the reaction, the mixture was depressurized and distilled to remove the solvent, and then the product was recrystallized and purified using an ethanol solution to obtain ligand L1 with a final yield of 87%. (1 H 300MHz, DMSO): 7.62-6.81 (m, 14H, Ar-H), 3.55 (s, 3H, CH3). C 21 H 17 N3: Elemental analysis calculated value (%): C, 81.00; H, 5.50; N, 13.49. Experimental determination value (%): C, 81.24; H, 5.52; N, 13.41.

[0086] Ligand L2

[0087] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-methyl substituted Dianhong (10 mmol) and aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L2 with a final yield of 81%. ( 1 H 300MHz, DMSO): 11.11 (s, 1H, NH), 7.55-6.82 (m, 13H, Ar-H), 2.75-1.88 (m, 3H, CH3). C 21 H 17 N3: Elemental analysis calculated value (%): C, 81.00; H, 5.50; N, 13.49. Experimental determination value (%): C, 81.15; H, 5.54; N, 13.47.

[0088] Ligand L3

[0089] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R5-methyl substituted Dianhong (10 mmol) and aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L3 with a final yield of 85%. ( 1 H 300MHz, DMSO): 11.24 (s, 1H, NH), 7.45-6.02 (m, 13H, Ar-H), 2.83-1.95 (m, 3H, CH3). C 21 H 17 N3: Elemental analysis calculated value (%): C, 81.00; H, 5.50; N, 13.49. Experimental determination value (%): C, 81.07; H, 5.62; N, 13.53.

[0090] Ligand L4

[0091] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-isomethyl substituted Dianhong (10 mmol) and aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L4 with a final yield of 77%. ( 1 H 300MHz, DMSO): 10.96 (s, 1H, NH), 7.56-6.90 (m, 13H, Ar-H), 3.05-2.08 (m, 7H, CH (CH3) 2). C 23 H 21 N3: Elemental analysis calculated value (%): C, 81.38; H, 6.24; N, 12.38. Experimental determination value (%): C, 81.46; H, 6.39; N, 12.40.

[0092] Ligand L5

[0093] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-tert-butyl substituted Dianhong (10 mmol) and aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L5 with a final yield of 72%. ( 1 H 300MHz, DMSO): 11.23(s,1H,NH), 7.61-6.75(m,13H,Ar-H), 2.95-1.05(m,9H,C(CH3)3). C 24 H 23 N3: Elemental analysis calculated value (%): C, 81.55; H, 6.56; N, 11.89. Experimental determination value (%): C, 81.58; H, 6.59; N, 11.90.

[0094] Ligand L6

[0095] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-isopropyl substituted Dianhong (10 mmol) and R6-methyl substituted aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L6 with a final yield of 82%. ( 1 H 300MHz, DMSO): 11.40(s,1H,NH), 7.44-6.92(m,9H,Ar-H), 3.11-2.38(m,19H,CH(CH3)2). C 27 H 29 N3: Elemental analysis calculated value (%): C, 81.99; H, 7.39; N, 10.62. Experimental determination value (%): C, 82.06; H, 7.49; N, 10.57.

[0096] Ligand L7

[0097] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-isopropyl substituted Dianhong (10 mmol) and R6-bromo substituted aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L7 with a final yield of 80%. ( 1 H 300MHz, DMSO): 11.27(s,1H,NH), 7.60-6.81(m,9H,Ar-H), 3.31-1.48(m,7H,CH(CH3)2). C 23 H 17 N3Br4: Elemental analysis calculated value (%): C, 42.17; H, 2.62; N, 6.42; Br, 48.79. Experimental determination value (%): C, 42.16; H, 2.69; N, 6.47; Br, 48.77.

[0098] Ligand L8

[0099] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-isopropyl substituted isatin (10 mmol) and R6-isopropyl substituted aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the mixture was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L8 with a final yield of 77%. ( 1 H 300MHz, DMSO): 11.15(s,1H,NH), 7.77-6.92(m,9H,Ar-H), 3.19-1.35(m,35H,CH(CH3)2). C 35 H 45 N3: Elemental analysis calculated value (%): C, 82.79; H, 8.93; N, 8.28. Experimental determination value (%): C, 82.86; H, 8.97; N, 8.47.

[0100] Ligand L9

[0101] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-isopropyl substituted Dianhong (10 mmol) and R7-methyl substituted aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L9 with a final yield of 72%. ( 1 H 300MHz, DMSO): 11.29(s,1H,NH), 7.45-6.93(m,9H,Ar-H), 3.34-1.55(m,19H,CH(CH3)2). C 27 H 29 N3: Elemental analysis calculated value (%): C, 81.99; H, 7.39; N, 10.62. Experimental determination value (%): C, 82.02; H, 7.47; N, 10.66.

[0102] Ligand L10

[0103] 100 ml of mixed organic solvent (V toluene: V DMSO = 9: 1) was added to a 250 ml three-necked flask, and then R2-isopropyl substituted Dianhong (10 mmol) and R8-methyl substituted aniline (21 mmol) were added to the flask and mixed evenly, and then a catalytic equivalent of p-toluenesulfonic acid (10 μmol) was added, and the reaction was refluxed at 120°C for 24 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the product was recrystallized and purified using an ethanol solution to obtain ligand L10 with a final yield of 89%. ( 1 H 300MHz, DMSO): 11.50(s,1H,NH), 7.52-6.88(m,11H,Ar-H), 3.16-1.37(m,13H,CH3 CH(CH3)2). C 25 H 25 N3: Elemental analysis calculated value (%): C, 81.71; H, 6.96; N, 11.43. Experimental determination value (%): C, 81.78; H, 7.02; N, 11.59.

[0104] Examples 11-13

[0105] Preparation of ligands L1'~L3'.

[0106] Ligands L1' to L3' are not based on indigo carmine as the skeleton, and are prepared by the following methods:

[0107] The synthesis steps of L1' are as follows:

[0108] In a 250ml three-necked flask, 2,3-butanedione (10mmol) and aniline (22mmol) were dissolved in 100ml toluene solution, and catalytic p-toluenesulfonic acid (10μmol) was added. Water was separated and refluxed at 100℃ for 24h. After the reaction was completed, the solvent toluene was removed by vacuum distillation, and the solid product was recrystallized with hot ethanol solution, with a final yield of 86%. The reaction formula is as follows:

[0109]

[0110] The synthesis steps of L2' are as follows:

[0111] Add 3 mmol of 2,6-diacetylpyridine and 3.4 mmol of aniline to a 150 ml three-necked flask, then add 50 ml of toluene, stir and heat under reflux. After half an hour of reaction, add a catalytic amount of p-toluenesulfonic acid (10 μmol) and continue the reaction for 12 hours. Cool to room temperature and remove the solvent by rotary evaporation. Then perform column chromatography elution in an alkaline alumina column (the eluent is a mixture of petroleum ether and ethyl acetate, V 石油醚 :V 乙酸乙酯 =100:1) to finally obtain the pyridine diimine ligand with a yield of 48%. The reaction formula is as follows:

[0112]

[0113] The synthesis steps of L3' are as follows:

[0114] Under argon protection, add salicylaldehyde (0.2 mol) and 60 ml of anhydrous ethanol to a 250 ml three-necked flask. Add aniline (0.02 mol) to the flask using a constant pressure dropping funnel, and then add formic acid (0.5 ml). Heat to 80 ° C and react for 2 hours. Cool to room temperature and distill under reduced pressure. Cool to precipitate the product. The final product yield is 88%. The reaction formula is as follows:

[0115]

[0116] Examples 14-23

[0117] Preparation of catalysts C1-C10:

[0118] Under anhydrous and oxygen-free conditions, 100 ml of ultra-dry acetonitrile was added to a three-necked flask, and ligands L1-L10 (8.4 mmol) and anhydrous NiC12 (4 mmol) were added respectively. The reaction temperature was controlled to 55°C and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature, concentrated by reduced evaporation, the solvent was filtered out, washed with dry n-hexane for several times, and dried to obtain catalysts C1-C10 respectively.

[0119] Examples 24-26

[0120] Preparation of Catalysts C1'-C3'.

[0121] Catalysts C1'-C3' are prepared by the following method using ligands L1'-L3' as ligands respectively:

[0122] Synthesis of catalyst C1':

[0123] Add the synthesized ligand (5 mmol) and anhydrous NiCl2 (11 mmol) to a single-necked flask, followed by anhydrous acetonitrile. Pump nitrogen three times and reflux at 55°C for 24 hours. After the reaction is completed, cool to room temperature, concentrate under reduced pressure, filter to obtain a solid, and wash with n-hexane. The final yield is 77%. The reaction formula is as follows:

[0124]

[0125] Synthesis of catalyst C2':

[0126] The prepared pyridine diimine ligand (1 mmol) and FeCl2·4H2O (1.2 mmol) were added to a 50 ml single-necked flask. Then nitrogen was pumped in three times to create an anhydrous and oxygen-free environment. Then, redistilled anhydrous ethanol was added and stirred at room temperature. After reacting for 12 hours, it was filtered and washed with ether. The final product yield was 95%. The reaction formula is as follows:

[0127]

[0128] Synthesis of catalyst C3':

[0129] Add 40ml of freshly steamed THF, NaH (4mmol) to a 100ml three-necked flask and pump nitrogen three times. Then slowly drip the salicylaldehyde imine ligand into the flask with a constant pressure dropping funnel and stir at room temperature for 3h. Filter to remove unreacted NaH. Finally, add 40ml of toluene and (Ph3)2PhNiCl (1.5mmol) and stir at room temperature for 12h, concentrate the filtrate, and slowly add n-hexane solution until crystals precipitate. Finally, recrystallize with toluene and n-hexane solution, and the final product yield is 70%. The reaction formula is as follows:

[0130]

[0131] Application Examples

[0132] The catalysts C1-C10 and C1'-C3' obtained above, and the catalyst C4' (metallocene catalyst titanocene dichloride, CAS: 1271-19-8) were used to prepare polyethylene wax and their performance was tested.

[0133] The reaction conditions are as follows: a 250 ml stainless steel reactor is heated under vacuum at 150°C for 2 hours, and then cooled to ambient temperature. The reactor is then pressurized to 1.2 atm with ethylene, and then vented and pressurized again with ethylene, and repeated three times to ensure that the reactor is filled with ethylene atmosphere. The cocatalyst MAO (1 mmol) is then dissolved in 100 ml of dry toluene and injected into the reactor, and stirred continuously for 5 minutes under 1.2 atm of ethylene pressure. Finally, 50 ml of a toluene dilution of the catalyst (any one of C1-C10, C1'-C4') (containing 2 μmol of catalyst) is added to the reactor with a syringe and stirred evenly. Gaseous ethylene was continuously added during the entire reaction process, and the ethylene pressure was maintained at 10 atm. In the polymerization experiment, the reaction temperature was controlled at 45-120°C. The polymerization process was completed after 1 hour of reaction. During post-treatment, acidic methanol (ethanol / hydrochloric acid in a mass ratio of 95:5) was added to inactivate the catalyst. The resulting precipitated polymer was collected, separated by rotary evaporation, and dried in a vacuum at 40°C to a fixed weight to obtain a polyethylene wax sample.

[0134] 1. The catalytic activity of each catalyst at different reaction temperatures was tested. The catalytic activity was calculated based on the yield of the polyethylene wax sample, in g polyethylene wax / (mol catalyst×h), as shown in Table 2.

[0135] Table 2 Catalytic activity of different catalysts at different temperatures (10 6 g PE / mol cat·h)

[0136]

[0137]

[0138] Note: “--” means not performed.

[0139] As shown in Table 2, the late transition metal catalysts C1-C10 obtained by using isatin as the skeleton of the diimide structure have higher catalytic activity at 45-120°C, and the activity of the electron-donating group catalyst is better than that of the electron-withdrawing group catalyst (catalyst C7). From the catalyst structure, when the substituents on R2 and R6 have certain steric hindrance effects and electron-donating effects, the two interact with each other. For example, catalyst C8 has the best catalytic activity, and the catalytic activity at 75°C can reach 11.45×10 6 g PE / mol cat·h, and still has a value of 6.35×10 6 The catalytic activity of PE / mol cat·h is much higher than that of other non-indigo framework late transition metal catalysts.

[0140] 2. Polyethylene wax sample performance test

[0141] Some polyethylene wax samples were selected for further performance testing and analysis. The selected samples E1-E8 are as follows:

[0142] The polyethylene wax sample obtained by polymerization of catalyst C1 at 45°C is denoted as E1;

[0143] The polyethylene wax sample obtained by polymerization of catalyst C2 at 60°C is denoted as E2;

[0144] The polyethylene wax sample obtained by polymerization of catalyst C3 at 75°C is denoted as E3;

[0145] The polyethylene wax sample obtained by polymerization of catalyst C5 at 60°C is denoted as E4;

[0146] The polyethylene wax sample obtained by polymerization of catalyst C6 at 75°C is denoted as E5;

[0147] The polyethylene wax sample obtained by polymerization of catalyst C7 at 60°C is denoted as E6;

[0148] The polyethylene wax sample obtained by polymerization of catalyst C8 at 75°C is denoted as E7;

[0149] The polyethylene wax sample obtained by polymerization of catalyst C10 at 45°C is denoted as E8.

[0150] For comparison, some comparison samples E1'~E5' are selected, as follows:

[0151] The polyethylene wax sample obtained by polymerization of catalyst C1' at 60°C is denoted as E1';

[0152] The polyethylene wax sample obtained by polymerization of catalyst C2' at 45°C is denoted as E2';

[0153] The polyethylene wax sample obtained by polymerization of catalyst C3' at 75°C is denoted as E3';

[0154] The polyethylene wax sample obtained by polymerization of catalyst C4' at 75°C is denoted as E4'.

[0155] The polyethylene wax sample E5' was prepared by initiating free radicals. The specific preparation method was as follows: the polymerization reaction pressure was increased from 10 atm to 100 atm, the catalyst was replaced with 5 μmol of dibenzoyl peroxide (BPO), and the polymerization reaction was carried out at 85° C. to obtain a product.

[0156] Samples E1-E8 and samples E1'-E5' were tested by the following method:

[0157] 1. Molecular weight determination

[0158] Molecular weight determination includes weight average molecular weight (Mw) and number average molecular weight (Mn): determined by gel permeation chromatography in accordance with GB / T27843-2011 "Determination of low molecular weight component content of polymers in chemicals - Gel permeation chromatography (GPC)". The molecular weight distribution index (PDI) of polyethylene wax is determined by the ratio of the measured weight average molecular weight to the number average molecular weight.

[0159] 2. Determination of branching degree

[0160] The degree of branching of polyethylene wax was calculated by H-NMR spectrum.

[0161] 3. Drop melting point viscosity determination

[0162] The drop melting point is determined in accordance with GB / T 8026-2014 “Determination of drop melting point of petroleum waxes and petroleum fats”.

[0163] The specific test results are shown in Table 3.

[0164] Table 3 Polyethylene wax sample performance determination

[0165] M PDI Degree of branching ( / 1000C) Drop melting point(℃) E1 7840 1.36 47 115 E2 5170 1.33 24 84 E3 5430 1.48 35 86 E4 6820 1.32 21 94 E5 6510 1.27 27 92 E6 5190 1.44 36 85 E7 5750 1.12 11 89 E8 3860 1.40 37 57 E1’ 11540 1.72 68 125 E2’ 38700 1.92 132 136 E3’ 15600 1.85 144 129 E4’ 7420 1.31 49 96 E5’ 1970 4.65 38 33

[0166] As can be seen from Table 3, the weight average molecular weight of the polyethylene wax obtained by the present invention is 3800-8000, the molecular weight distribution is between 1.1-1.5, the branching degree is low (<50 / 1000C), and it is a polyethylene wax with excellent performance. Compared with other types of polyethylene waxes obtained by late transition metal catalysts, the molecular weight is moderate, the molecular weight distribution is tight, and the branching degree is small, which can meet the market demand. The performance of the E4' sample prepared by using the commonly used metallocene catalyst dichlorotitacenes (high cost, poor high temperature resistance, and inability to polar solvents) is comparable, while the molecular weight distribution index of other comparative samples (E1', E2', E3', E5') is higher, and the consistency of the products is poor.

[0167] It should be understood by those skilled in the art that the above embodiments are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functions and principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be modified or altered in any way without departing from the principles.

Claims

1. A diimine ligand having the general structure shown in Formula L: in, R1 to R8 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen.

2. The diimine ligand according to claim 1, characterized in that At least one of R1 to R5 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl, and / or at least one of R6, R7, R8 is selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl.

3. The diimine ligand according to claim 2, characterized in that: Among R1 to R5, at least one of R1, R2 and R5 is selected from C1-C6 alkyl, and the rest are H.

4. The diimine ligand according to claim 2, characterized in that: R6 is methyl, isopropyl or methoxy, and / or R7 is methyl, isopropyl or methoxy, and / or R8 is methyl, isopropyl or tert-butyl.

5. The diimine ligand according to claim 1, characterized in that: The diimine ligand is selected from any one of the following diimine ligand compounds of Formula L1 to Formula L10:

6. The method for preparing the diimine ligand according to any one of claims 1 to 5, characterized in that: The diimine ligand is prepared by acid catalysis using a 1,2-diketone compound of the general structure shown in Formula I and a large sterically hindered aromatic amine of the general structure shown in Formula II as raw materials. The specific reaction formula is as follows:

7. The method according to claim 6, characterized in that The 1,2-diketone compound is an isatin derivative in which the R2 substituent is methyl, methoxy or isopropyl, and R1, R3, R4 and R5 are H.

8. A late transition metal polyethylene wax catalyst, characterized in that The invention is a coordination compound formed by the diimine ligand described in any one of claims 1 to 5 and a late transition metal salt.

9. The late transition metal polyethylene wax catalyst according to claim 8, characterized in that The late transition metal polyethylene wax catalyst is a nickel metal polyethylene wax catalyst having a general structure shown in Formula C: Wherein X is chlorine or bromine.

10. Use of the late transition metal polyethylene wax catalyst according to claim 8 or 9 in the preparation of polyethylene wax.

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