Symmetrical alpha-diimine nickel complex for synthesizing thermoplastic polyethylene elastomer, intermediate and preparation method and application of symmetric alpha-diimine nickel complex

Abstract

The invention discloses a symmetric alpha-diimine nickel complex for synthesizing a thermoplastic polyethylene elastomer, an intermediate as well as a preparation method and application of the symmetric alpha-diimine nickel complex. The symmetric alpha-diimine nickel complex has a single catalytic activity center, and the molecular weight and branching degree of a polymer can be regulated and controlled by changing the structure of the symmetric alpha-diimine nickel complex; the thermoplastic polyethylene elastomer prepared by the method has the advantages of high catalytic activity, low cost and excellent thermal stability, especially the ultimate tensile strength of polyethylene prepared at 100 DEG C is up to 10.3 Mpa, the maximum fracture strain is 1863%, the strain recovery rate after 10 cycles is up to 55% under the condition that the fixed strain is 300%, and the thermoplastic polyethylene elastomer is potential thermoplastic polyethylene elastomer.

Description

Technical Field

[0001] This invention belongs to the field of polyolefin catalysts, specifically relating to a catalyst for synthesizing polyethylene elastomers, and more particularly to a symmetrical α-diimine nickel complex for synthesizing thermoplastic polyethylene elastomers. It also relates to intermediates and methods for preparing the symmetrical α-diimine nickel complex, and the application of the symmetrical α-diimine nickel complex. Background Technology

[0002] Polyethylene (PE) has become the world's fastest-growing, largest-volume, and most widely used synthetic resin due to its good chemical resistance, low price, and excellent mechanical properties. It is widely applied in many fields, including industry, agriculture, military, and medicine. Among these applications, polyethylene elastomers represent a significant development direction for high-end polyethylene. Their unique molecular structure endows them with excellent mechanical properties, rheological properties, aging resistance, and good low-temperature toughness, making them a high-performance, high-value-added new elastomer material. However, my country relies heavily on imports for polyethylene elastomers. Therefore, developing high-end polyethylene elastomers has become a major research direction in the field of polyethylene materials, and the catalysts used in the polyethylene production process are a key element in ethylene polymerization research.

[0003] To date, the catalysts for industrialized ethylene polymerization mainly include: Ziegler-Natta type catalysts (CN116410360A(2023); CN115043961A(2022); Angew. Chem., 955, 67, 426-427), metallocene catalysts (CN115003707A(2022); CN114249775A(2022); Angew. Chem. Int. Ed., 1980, 19, 390), post-transition metal catalysts (CN105461757A (2014); CN104059180B (2013); J. Am. Chem. Soc., 120(16), 4049-4050), and α-diimine-type post-transition metal catalysts (CN107698699A (2017); Dalton T., 2022, 51, 14375-14407). Among them, the α-diimine-type post-transition metal catalyst can catalyze the production of high molecular weight polyethylene elastomers from ethylene, which has attracted the attention and great interest of researchers.

[0004] In particular, Brookhart reported in 1995 that α-diimine nickel and palladium complexes catalyzed ethylene polymerization to obtain high molecular weight, highly branched polyethylene. Its unique chain-walking characteristics, unlike metallocene and Ziegler-Natta catalysts, allow for the adjustment of polyethylene branching and structure solely from the ethylene feedstock. Therefore, it exhibits unprecedented catalytic performance in polyethylene conformational control, leading to its widespread application in ethylene polymerization. Especially recently, structural modifications to α-diimine nickel catalysts have provided exceptionally high activity in ethylene polymerization and offer significant control over polymer properties such as molecular weight, dispersion index, and microstructure. However, as a novel catalyst system, it still faces challenges and limitations hindering its industrialization.

[0005] For many years, Professor Sun Wenhua's research group in China has been dedicated to the design, development, and research of polyethylene elastomer catalysts. They have developed a series of asymmetric α-diimine nickel catalysts for ethylene polymerization. For example, CN104250270A discloses an asymmetric diphenylmethyl α-diimine nickel complex, its preparation method, and its application. This complex exhibits a catalytic activity as high as 1.24 × 10⁻⁶ for catalyzing ethylene polymerization. 7 g·mol -1 (Ni)·h -1 Furthermore, the obtained polymer not only has a high molecular weight but also exhibits a bimodal distribution. CN115701435A teaches a trifluoromethoxy-modified asymmetric diimine nickel complex, intermediates, and their preparation methods and applications. This complex, using MAO as a co-catalyst, maintains a molecular weight of 1.76 × 10⁻⁶ at a reaction temperature of 90 °C. 6 g·mol -1 (Ni)·h -1 The high activity of the catalyst resulted in polyethylene elastomers with high molecular weight, narrow distribution, and high branching. These findings underscore the need for further catalyst tuning. The limited thermal stability of the catalyst prompts further investigation into the industrial application of α-diimine nickel catalysts in ethylene polymerization, aiming to achieve enhanced catalytic performance at high temperatures. Summary of the Invention

[0006] In order to obtain a catalyst that still has high catalytic activity for ethylene polymerization at high temperatures, the inventors of this invention have conducted extensive research on α-diimine-based catalysts and obtained a highly thermally stable symmetrical α-diimine nickel complex. This complex has a single catalytic active center, and its structure can be modified to control the molecular weight and branching degree of the polymer. At the same time, it also has high catalytic activity, low cost and excellent thermal stability.

[0007] To achieve the above objectives, a first aspect of the present invention provides a symmetrical α-diimine nickel complex for synthesizing thermoplastic polyethylene elastomers, having the following structural formula (I):

[0008]

[0009] Wherein, R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C6 alkyl, C5-C6 alkyl, C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 aryloxy group;

[0010] X is selected from halogens.

[0011] The symmetrical α-diimine nickel complex of this invention possesses a single catalytic active center. The molecular weight and branching degree of the polymer can be controlled by altering the ligand structure. Furthermore, it exhibits high catalytic activity, low cost, and high thermal stability. In particular, when this symmetrical α-diimine nickel complex is used as a catalyst in the preparation of polyethylene, its catalytic activity reaches 1.48 × 10⁻⁶. 7 g·mol -1 (Ni)·h -1 Especially under reaction conditions of 100℃, its catalytic activity can still be maintained at 2.51×10⁻⁶. 6 g·mol -1 (Ni)·h -1 Furthermore, the weight-average molecular weight (Mw) of the prepared polyethylene is as high as 3.98 × 10⁻⁶. 5 g·mol -1 The molecular weight fluctuates between 1.5 and 2.0, exhibiting strong control over the molecular weight of polyethylene. The obtained polyethylene has a high degree of branching. Mechanical property tests show that its ultimate tensile strength is 10.3 MPa, the maximum breaking strain is 1863%, and the strain recovery rate is as high as 55% after 10 cycles when the strain is fixed at 300%. It is a potential thermoplastic polyethylene elastomer.

[0012] Preferably, in the above-described symmetrical α-diimine nickel complex, the substituted C1-C6 alkyl, C1-C6 alkoxy, C3-C... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 The aryloxy group may optionally be substituted by one or more identical or different R2 groups, wherein the R2 group is selected from halogens (such as F, Cl, Br, I), C1-C6 alkyl groups, C1-C6 alkoxy groups, C3-C6 alkyl groups, and C4-C6 alkoxy groups. 10cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0013] Preferably, in the above-described symmetrical α-diimine nickel complex, R is selected from H, halogens, or unsubstituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0014] More preferably, in the above-mentioned symmetrical α-diimine nickel complex, R is selected from halogen, C1-C6 alkyl or C1-C6 alkoxy, particularly preferably halogen or C1-C3 alkyl, such as methyl, ethyl, n-propyl, isopropyl, and most particularly preferably chlorine, methyl, ethyl, isopropyl.

[0015] Preferably, in the above-described symmetrical α-diimine nickel complex, the halogen is fluorine, chlorine, bromine, or iodine, with fluorine, chlorine, and / or bromine being particularly preferred. Preferably, in the above-described symmetrical α-diimine nickel complex, X is selected from chlorine or bromine.

[0016] More particularly preferably, in the above-mentioned symmetrical α-diimine nickel complex, R is selected from methyl, ethyl, isopropyl, chlorine, and X is selected from chlorine or bromine.

[0017] Most preferably, the symmetrical α-diimine nickel complex has the structure shown in formulas (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7), or (I-8):

[0018]

[0019]

[0020]

[0021] In other words, as an example, the symmetrical α-diimine nickel complex of formula (I) can be selected from complexes having the following group definitions:

[0022] C1: R = Me (methyl); X = Br (bromine);

[0023] C2: R = Et (ethyl); X = Br (bromine);

[0024] C3: R = i-Pr (isopropyl); X = Br (bromine);

[0025] C4: R = Cl (chlorine), X = Br (bromine);

[0026] C5: R = Me (methyl); X = Cl (chlorine);

[0027] C6: R = Et (ethyl); X = Cl (chlorine);

[0028] C7: R = i-Pr (isopropyl); X = Cl (chlorine);

[0029] C8: R = Cl (chlorine), X = Cl (chlorine).

[0030] To overcome the limitations of existing α-diimine-based transition metals, such as limited thermal stability and poor controllability, this invention introduces steric hindrance at the axial position of the metal center. This strategy, by altering the steric hindrance at adjacent sites, provides an effective way to counteract catalyst decomposition at higher temperatures. Furthermore, the symmetrical axial shielding results in relatively high activity, a higher polymer molecular weight, and a significant increase in branching within polyethylene. Consequently, the symmetrical α-diimine nickel complex of formula (I) obtained in this invention exhibits high catalytic activity and good thermal stability when applied to the catalytic reaction of ethylene polymerization; even at 100°C, its catalytic activity remains at 2.51 × 10⁻⁶. 6 g·mol -1 (Ni)·h -1 .

[0031] According to a second aspect of the present invention, an intermediate for preparing the above-described symmetrical α-diimine nickel complex is provided, having the structure of formula (II):

[0032]

[0033] Wherein, R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C6 alkyl, C5-C6 alkyl, C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0034] Preferably, in the above intermediate, the substituted C1-C6 alkyl, C1-C6 alkoxy, C3-C 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 The aryloxy group may optionally be substituted by one or more identical or different R2 groups, wherein the R2 group is selected from halogens (such as F, Cl, Br, I), C1-C6 alkyl groups, C1-C6 alkoxy groups, C3-C6 alkyl groups, and C4-C6 alkoxy groups. 10cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0035] Preferably, in the above intermediate, R is selected from H, halogens, or unsubstituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0036] More preferably, in the above intermediate, R is selected from halogens, C1-C6 alkyl groups or C1-C6 alkoxy groups, particularly preferably halogens or C1-C3 alkyl groups, such as fluorine, chlorine, bromine, iodine, methyl, ethyl, n-propyl, isopropyl, and most particularly preferably chlorine, methyl, ethyl, isopropyl.

[0037] Most preferably, the intermediate has the structure shown in formula (II-1), (II-2), (II-3), or (II-4):

[0038]

[0039]

[0040] In other words, as an example, the intermediate of the structure of formula (II) can be selected from substances having the following group definitions:

[0041] L1: R = Me (methyl);

[0042] L2: R = Et(ethyl);

[0043] L3: R = i-Pr (isopropyl);

[0044] L4: R = Cl (chlorine).

[0045] According to a third aspect of the present invention, a method for preparing an intermediate of the structure of formula (II) above is provided, comprising the following steps:

[0046] Preparation of aniline with (S1) formula (IV): Diphenylmethanol and ortho-substituted aniline with (III) formula are mixed into a homogeneous liquid state, and then a mixture of zinc chloride and hydrochloric acid is added. After mixing evenly, the temperature of the reaction system is raised to above 150°C under stirring, and the reaction is carried out at this temperature for 0.5-4 hours to make the entire reaction system into a solid state, thus obtaining aniline with (IV) formula.

[0047] Preparation of intermediate product with structure (S2) of formula (V): Under stirring conditions, the product obtained in step (S1), acenaphthoquinone and zinc chloride are dissolved in acetic acid. The mixture is then heated under reflux. The reaction system gradually turns into a red solution until a solid is formed. The reaction is then continued at this temperature for 6-36 hours. After solid-liquid separation and washing, the intermediate product with structure (V) can be obtained.

[0048] Preparation of the intermediate of formula (II) (S3): The intermediate of formula (V) was dissolved in an organic solvent and mixed with an aqueous solution of potassium oxalate. The resulting system was reacted at room temperature with stirring for 0.5-3 h. The organic layer was then separated and washed with water, dried with anhydrous sodium sulfate, and subjected to solid-liquid separation. Finally, after removing the organic solvent, the mixture was purified to obtain an orange solid, which is the intermediate of formula (II).

[0049] The structure of the ortho-substituted aniline of formula (III) is as follows:

[0050]

[0051] The structure of aniline of formula (IV) is as follows:

[0052]

[0053] The structure of the intermediate product of formula (V) is as follows:

[0054]

[0055] In formulas (III), (IV), and (V), R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0056] The preparation process of the intermediate of the structure of formula (II) of the present invention is simple. First, the ortho-substituted aniline of structure (III) is reacted with diphenylmethanol to generate aniline of structure (IV). Then, the aniline of structure (IV), acenaphthoquinone and zinc chloride are prepared in a one-pot method to prepare the intermediate product of structure (V), namely the zinc complex. Finally, the obtained zinc complex is reacted with potassium oxalate to obtain the intermediate of the present invention. During the preparation of the zinc complex, the reaction system gradually turns into a red solution, and as the reaction proceeds, solids are gradually generated. In order to ensure the complete reaction, the reaction needs to continue.

[0057] In this invention, aniline of formula (IV), intermediate of formula (V) and intermediate of formula (II) can all be prepared in large quantities in advance for later use. Of course, they can also be synthesized in advance through other synthetic routes in the prior art. Therefore, the preparation process of intermediate of formula (II) of this invention is not limited to the preparation process disclosed in this invention.

[0058] Preferably, in formulas (III), (IV), and (V), the substituted C1-C6 alkyl, C1-C6 alkoxy, C3-C 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy groups may optionally be replaced by one or more identical or different R groups, either independently of each other. 2 Substitution, the group R 2 Selected from halogens (such as F, Cl, Br, I), C1-C6 alkyl, C1-C6 alkoxy, C3-C 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0059] Preferably, in formulas (III), (IV), and (V), R is selected from H, halogens, or unsubstituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C14 aryloxy.

[0060] More preferably, in formulas (III), (IV) and (V), R is selected from halogens, C1-C6 alkyl or C1-C6 alkoxy, particularly preferably halogens or C1-C3 alkyl, such as fluorine, chlorine, bromine, iodine, methyl, ethyl, n-propyl, isopropyl, and most particularly preferably chlorine, methyl, ethyl, isopropyl.

[0061] In other words, as an example, the ortho-substituted aniline of formula (III) is 2-methylaniline, 2-ethylaniline, 2-isopropylaniline, or 2-chloroaniline. Correspondingly, as an example, the aniline of formula (IV) obtained in step (S1) is:

[0062] E1: R = Me (methyl), i.e., 2,4-bis(diphenylmethyl)-6-methylaniline;

[0063] E2: R = Et(ethyl), i.e., 2,4-bis(diphenylmethyl)-6-ethylaniline;

[0064] E3: R = i-Pr(isopropyl), i.e., 2,4-bis(diphenylmethyl)-6-isopropylaniline;

[0065] E4: R = Cl (chlorine), i.e., 2,4-bis(diphenylmethyl)-6-chloroaniline.

[0066] Preferably, in the method for preparing the intermediate of formula (II) above, in step (S1), the diphenylmethanol and the ortho-substituted aniline of formula (III) need to be heated to above 110°C, preferably 110-130°C, to melt the diphenylmethanol, and then mixed with the ortho-substituted aniline of formula (III) to form a uniform liquid state. Alternatively, the mixture of diphenylmethanol and the ortho-substituted aniline of formula (III) can be heated to above 110°C, preferably 110-130°C, and mixed evenly to form a uniform liquid state.

[0067] Preferably, in the method for preparing the intermediate of formula (II) above, the molar ratio of the ortho-substituted aniline of formula (III) to diphenylmethanol in step (S1) is 1:(2-2.4). Since at least 2 equivalents of diphenylmethanol are required for 1 equivalent of the ortho-substituted aniline of formula (III) to generate the target product aniline of formula (IV), the molar ratio of the ortho-substituted aniline of formula (III) to diphenylmethanol is limited to 1:(2-2.4) to ensure the complete progress of the reaction.

[0068] Preferably, in the method for preparing the intermediate of the structure of formula (II) described above, the mixture of zinc chloride and hydrochloric acid in step (S1) requires that the zinc chloride be dissolved in hydrochloric acid beforehand to obtain a homogeneous mixed solution. In this invention, dissolving the zinc chloride in hydrochloric acid facilitates subsequent operations and makes it easier to add zinc chloride as a catalyst to the reaction system.

[0069] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, the mass fraction of hydrochloric acid used in the mixture of zinc chloride and hydrochloric acid in step (S1) is 36.0-38.0%, that is, commercially available concentrated hydrochloric acid.

[0070] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, the mass fraction of zinc chloride in the mixture of zinc chloride and hydrochloric acid in step (S1) is 35-60%.

[0071] Preferably, in the method for preparing the intermediate of the structure of formula (II) described above, the mixture of zinc chloride and hydrochloric acid in step (S1) is added to the solution of diphenylmethanol and ortho-substituted aniline of formula (III) at a constant rate to ensure a smooth reaction. More preferably, the addition rate of the mixture of zinc chloride and hydrochloric acid is 0.02-5 mL / s. If the addition rate is too fast, the reaction will be incomplete, while if the addition rate is too slow, a large amount of impurities will be generated.

[0072] Preferably, in the method for preparing the intermediate of formula (II) above, the molar ratio of zinc chloride to ortho-substituted aniline of formula (III) in step (S1) is (0.2-0.5):1, preferably 0.4:1.

[0073] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, after obtaining the solid product in step (S1), the reaction product needs to be washed with an alcohol solvent such as methanol, ethanol, propanol, or butanol to remove impurities.

[0074] Preferably, in the method for preparing the intermediate of formula (II) above, the molar ratio of the product obtained in step (S1) of step (S2) to acenaphthoquinone is (2-3):1, more preferably (2.5-3):1, and most preferably 2.7:1. The aniline of formula (IV) reacts with acenaphthoquinone in a molecular ratio of 2:1, but to ensure sufficient reaction of acenaphthoquinone, a slight excess of aniline of formula (IV) is required.

[0075] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, the molar ratio of zinc chloride to acenaphthoquinone in step (S2) is (1-1.4):1, more preferably 1.14:1.

[0076] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, the acetic acid used in step (S2) is of analytical grade, that is, commercially available acetic acid.

[0077] Preferably, in the method for preparing the intermediate of formula (II) above, in step (S2), when aniline, acenaphthoquinone, and zinc chloride of formula (IV) are dissolved in acetic acid before the reaction, the molar ratio of acetic acid to acenaphthoquinone is 90:1 or more, more preferably 90-120:1, and even more preferably 90-100:1, which ensures that the reactants are completely dissolved in acetic acid and avoids the waste of acetic acid.

[0078] Preferably, in the method for preparing the intermediate of the structure of formula (II) described above, the reflux temperature in step (S2) is 130-140°C to ensure that acetic acid is fully refluxed.

[0079] It is clear that in the above method for preparing the intermediate of formula (II), the reaction is carried out under stirring conditions to ensure the homogeneity of the reaction system. The stirring rate is only required to ensure the homogeneity of the system and is not particularly limited. More preferably, the stirring rate under the stirring conditions is 400 rpm or more to ensure the homogeneity of the reaction system.

[0080] In the method for preparing the intermediate of the structure of formula (II) above, the solid-liquid separation method in step (S2) is not strictly limited and can be any method that can separate the solid and the liquid, such as filtration, centrifugation, etc., as long as the purpose of solid-liquid separation is achieved.

[0081] Preferably, in the above method for preparing the intermediate of formula (II), the washing in step (S2) requires washing with acetic acid several times, such as 3 times, 4 times, etc., and then removing the residual glacial acetic acid with n-hexane to remove unreacted raw materials. The purity of the glacial acetic acid and n-hexane used is analytical grade or higher. The intermediate of formula (II) obtained by the present invention has a slightly orange-red color after washing, which is easy to distinguish.

[0082] Preferably, in the method for preparing the intermediate of the structure of formula (II) described above, the molar ratio of the intermediate of formula (V) in step (S3) to potassium oxalate is 1:(1-1.5), more preferably 1:1.2.

[0083] Preferably, in the method for preparing the intermediate of the structure of formula (II) described above, the molar volume ratio of the product obtained in step (S2) of step (S3), i.e., the intermediate of the structure of formula (V), to the organic solvent is 2 mmol:(30-60) mL, preferably 3 mmol:(30-50) mL, more preferably 4 mmol:(40-50) mL. If less solvent is added, it will affect the solubility of the reactants in the solvent.

[0084] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, the mass fraction of potassium oxalate in the potassium oxalate aqueous solution in step (S3) is 2-10%. The mass percentage of this potassium oxalate solution is not strictly limited; it is sufficient to ensure that the potassium oxalate is fully dissolved in water. Furthermore, in this invention, the potassium oxalate aqueous solution is prepared by dissolving commercially available potassium oxalate monohydrate in water, but it can also be prepared by other methods.

[0085] Preferably, in the method for preparing the intermediate of the structure of formula (II) above, the organic solvent in step (S3) is one or more of dichloromethane, dichloroethane, tetrahydrofuran, toluene or xylene, more preferably dichloromethane.

[0086] In the method for preparing the intermediate of the structure of formula (II) described above, the method for separating the organic layer in step (S3) can be any known method, such as standing, and is not strictly limited; the number of times the organic layer is washed with water can be multiple times, such as 2 times, 3 times, 4 times, etc., and is not limited, as long as the purpose of removing unreacted potassium oxalate is achieved; the method of solid-liquid separation is also not strictly limited, and can be any method that can separate the solid and liquid, such as filtration, centrifugation, etc., as long as the purpose of solid-liquid separation is achieved; the method of removing the organic solvent is also... There are no strict limitations; any method that can remove organic solvents, such as distillation or adsorption, is acceptable. The purification method can also be any suitable purification method, such as recrystallization. There are no strict limitations, but based on the simplicity and convenience of recrystallization, it is preferred to use dichloromethane and n-hexane for recrystallization to purify the intermediate of the structure of formula (II). More preferably, the crude solid product obtained after removing the organic solvent is first dissolved in dichloromethane, and then n-hexane is added for recrystallization to purify the solid product. The volume ratio of dichloromethane to n-hexane is 1:15-50, and more preferably 1:15-20.

[0087] In this invention, the intermediate of the structure of formula (II) can be prepared in large quantities in advance, or it can be obtained commercially or prepared through other means, and is not limited to the preparation methods described above.

[0088] According to a fourth aspect of the present invention, a method for preparing the above-described symmetrical α-diimine nickel complex is provided, comprising reacting an intermediate of the structure of formula (II) with a nickel-containing compound (e.g., a complexation reaction) to obtain a symmetrical α-diimine nickel complex of formula (I).

[0089] Clearly, during the reaction, the N atom provides lone pairs of electrons, and the metal provides empty orbitals, so there is a weak coordination bond between N and the metal. Therefore, the preparation process of the symmetrical α-diimine nickel complex is simple and does not require stringent process conditions, which provides a promising prospect for subsequent industrial applications.

[0090] Preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the nickel-containing compound is selected from nickel-containing halides, such as (DME)NiBr2 (nickel bromide activated by ethylene glycol dimethyl ether), NiCl2·6H2O (nickel chloride hexahydrate), or NiBr2 (nickel bromide). Most preferably, (DME)NiBr2 and NiCl2·6H2O are readily available and facilitate the formation of complexes between the nickel halide and the ligands, which is beneficial for subsequent ethylene polymerization.

[0091] Preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the reaction process is carried out under anaerobic conditions, such as an inert gas (e.g., nitrogen, helium, etc.). During this preparation process, oxygen and water readily undergo an oxidation reaction, destroying the (DME)NiBr2 and NiCl2·6H2O structures, thereby preventing the formation of nickel halide complexes.

[0092] Preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the molar ratio of the intermediate of the structure of formula (II) to the nickel-containing compound is 1:(0.8-1.4), preferably 1:(0.9-1.1).

[0093] Preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the reaction conditions are: temperature of 30-100℃, preferably 30℃; reaction time of 8-36 hours, preferably 12-36 hours, more preferably 14-24 hours.

[0094] Preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the reaction is carried out in an organic solvent, which may be selected from one or more of haloalkanes (such as dichloromethane, dichloroethane) and alcohol solvents (such as methanol, ethanol, propanol), preferably dichloromethane, dichloroethane, or ethanol.

[0095] More preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the reaction is carried out in an organic solvent, and the molar volume ratio of the nickel-containing compound to the organic solvent is 0.38 mmol:(8-20) mL, preferably 0.38 mmol:(9-20) mL, and more preferably 0.38 mmol:(10-20) mL. If too little organic solvent is added, it will affect the dissolution of the reactants in the solvent, resulting in incomplete reaction, less product and more impurities; if too much solvent is added, it will affect the activity of the ligand with (DME)NiBr2 and NiCl2·6H2O.

[0096] Preferably, in the method for preparing the above-mentioned symmetrical α-diimine nickel complex of the present invention, the symmetrical α-diimine nickel complex of formula (I) needs to be further purified. The purification process is to add diethyl ether to the solution obtained after the reaction to precipitate the complex, and then wash with diethyl ether by stirring to remove impurities. After removing diethyl ether, the α-diimine nickel complex of formula (I) is obtained.

[0097] According to a fifth aspect of the present invention, a catalyst composition is provided, the catalyst composition comprising a main catalyst and a co-catalyst, wherein the main catalyst is the above-described symmetrical α-diimine nickel complex.

[0098] The catalyst composition of the present invention uses the symmetrical α-diimine nickel complex of the present invention as the main catalyst, and is activated by a co-catalyst for ethylene polymerization.

[0099] Preferably, in the above catalyst composition, the co-catalyst is selected from one or more of aluminoxane and alkylaluminum chloride.

[0100] More preferably, in the above catalyst composition, the aluminum oxane is selected from methylaluminoxane (MAO) and / or triisobutylaluminum modified methylaluminoxane (MMAO).

[0101] More preferably, in the above catalyst composition, the alkylaluminum chloride is selected from one or two of diethylaluminum chloride (Et2AlCl), dimethylaluminum chloride (Me2AlCl), and sesquialuminum (EASC).

[0102] Preferably, in the above catalyst composition, when the co-catalyst is selected from one or more of aluminoxane, alkylaluminum, and alkylaluminum chloride, the molar ratio of metal Al in the co-catalyst to the central metal Ni of the symmetrical α-diimine nickel complex of formula (I) is (200-3000):1, preferably (400-2000):1, for example, it can be 200:1, 300:1, 350:1, 400:1, 450:1, 500:1, 600:1, 1000:1, 1500:1, 1750:1, 2000:1, 2250:1, or 3000:1.

[0103] Preferably, in the above catalyst composition, when the co-catalyst is methylaluminoxane (MAO), the molar ratio of metal Al in the methylaluminoxane (MAO) to the central metal Ni of the symmetrical α-diimine nickel complex of formula (I) is (1000-3000):1, and more preferably the molar ratio is 1750:1.

[0104] Preferably, in the above catalyst composition, when the co-catalyst is triisobutylaluminum-modified methylaluminoxane (MMAO), the molar ratio of metal Al in the triisobutylaluminum-modified methylaluminoxane (MMAO) to the central metal Ni of the symmetrical α-diimine nickel complex of formula (I) is (1000-3000):1, and more preferably the molar ratio is 1750:1.

[0105] Preferably, in the above catalyst composition, when the co-catalyst is diethylaluminum chloride (Et2AlCl), the molar ratio of metallic Al in the diethylaluminum chloride (Et2AlCl) to the central metallic Ni of the symmetrical α-diimine nickel complex of formula (I) is (200-1000):1, more preferably (200-600):1, for example, it can be 200:1, 300:1, 350:1, 400:1, 450:1, 500:1 or 600:1.

[0106] Preferably, in the above catalyst composition, when the co-catalyst is dimethylaluminum chloride (Me2AlCl), the molar ratio of metallic Al in the dimethylaluminum chloride (Me2AlCl) to the central metallic Ni of the symmetrical α-diimine nickel complex of formula (I) is (200-800):1, more preferably (200-600):1, for example, it can be 200:1, 300:1, 350:1, 400:1, 450:1, 500:1 or 600:1.

[0107] In this invention, the catalyst composition can store the main catalyst and the co-catalyst separately and use them in proportion when needed, or the main catalyst and the co-catalyst can be directly mixed and packaged so that they can be used directly without mixing.

[0108] It is particularly noteworthy that in the catalyst composition of the present invention, the ratio of the main catalyst to the co-catalyst can be adjusted according to the specific application scenario and the requirements of the product. The ratio limit in the present invention is a relatively general range, and the specific ratio limit needs to be set by the user.

[0109] According to a sixth aspect of the invention, the use of the symmetrical α-diimine nickel complex of formula (I) and / or the catalyst composition described above is provided as a catalyst for catalyzing olefin polymerization. Particularly preferred is the use of the symmetrical α-diimine nickel complex of formula (I) and the catalyst composition described above as a catalyst for catalyzing ethylene polymerization.

[0110] The symmetrical α-diimine nickel complex of this invention possesses a single catalytic active center. The molecular weight and branching degree of the polymer can be controlled by altering the ligand structure. Furthermore, it exhibits high catalytic activity, low cost, and high thermal stability. In particular, when this symmetrical α-diimine nickel complex is used as a catalyst in ethylene polymerization, its catalytic activity reaches 1.48 × 10⁻⁶. 7 g·mol -1 (Ni)·h -1 Especially under reaction conditions of 100℃, its catalytic activity can still be maintained at 2.51×10⁻⁶. 6 g·mol -1 (Ni)·h-1 Furthermore, the weight-average molecular weight (Mw) of the prepared polyethylene is as high as 3.98 × 10⁻⁶. 5 g·mol -1 The molecular weight fluctuates between 1.5 and 2.0, exhibiting strong control over the molecular weight of polyethylene. It can be used to prepare ultra-high molecular weight polyethylene, especially polyethylene prepared at 100°C, which has an ultimate tensile strength of 10.3 MPa and a maximum breaking strain of 1863%. With a fixed strain of 300%, the strain recovery rate after 10 cycles is as high as 55%, making it a potential thermoplastic polyethylene elastomer. It should be clarified that the amount of the symmetrical α-diimine nickel complex of formula (I) and the above-mentioned catalyst composition used as catalysts for olefin polymerization is the conventional amount of catalyst used in olefin polymerization in the art. However, those skilled in the art can adjust it according to the actual application scenario and the desired performance requirements such as the molecular weight and molecular weight distribution of the polymer.

[0111] According to a seventh aspect of the present invention, a method for preparing polyethylene is provided, wherein the symmetrical α-diimine nickel complex of formula (I) and / or the above-described catalyst composition are used as catalysts to catalyze the polymerization of ethylene.

[0112] The symmetrical α-diimine nickel complex of formula (I) of the present invention introduces steric hindrance at the axial position of the metal center, providing an effective strategy to counteract catalyst decomposition at higher temperatures, wherein the symmetrical axial shielding results in relatively high activity, higher polymer molecular weight, and significantly increased branching in polyethylene.

[0113] Preferably, in the method for preparing polyethylene of the present invention, the polymerization reaction conditions are: temperature of 30-100°C, for example, 30°C, 40°C, 60°C or 80°C; time of 5-60 min, for example, 5 min, 10 min, 15 min, 45 min or 60 min; and pressure of 0.5-10 atm, for example, 1 atm, 5 atm or 10 atm.

[0114] Generally, the state of the catalyst in the reaction system changes with the polymerization temperature, and the changes become more drastic as the temperature increases. High temperatures can lead to catalyst deactivation, so the higher the temperature, the lower the catalytic activity. However, the catalyst of this invention has high thermal stability, and its catalytic activity is still as high as 2.51 × 10⁻⁶ under reaction conditions of 100°C. 6 g·mol -1 (Ni)·h -1 Therefore, polyethylene can be prepared at higher temperatures, shortening the reaction time and improving production efficiency.

[0115] Preferably, in the method for preparing polyethylene of the present invention, the solvent for the polymerization reaction is selected from one or more of the following: aromatic solvents such as toluene, chloroalkane solvents such as dichloromethane, alcohol solvents such as ethanol, ether solvents such as tetrahydrofuran, and alkane solvents such as hexane or cyclohexane.

[0116] Preferably, in the method for preparing polyethylene of the present invention, the polymerization reaction is carried out under an ethylene atmosphere.

[0117] Preferably, in the method for preparing polyethylene of the present invention, the polymerization reaction process involves dissolving the symmetrical α-diimine nickel complex of catalyst formula (I) of the present invention and / or the above catalyst composition as catalysts in an organic solvent, heating to 30-100°C, introducing ethylene, and polymerizing at a pressure of 0.5-10 atm for 5-60 min to obtain polyethylene.

[0118] The symmetrical α-diimine nickel complex and / or the above-mentioned catalyst composition of this invention, when used as catalysts for ethylene polymerization, yield polyethylene with a melting temperature of 71-130°C. This indicates that the obtained polyethylene has a wide range of applications in terms of temperature range, and it also has a high degree of branching and good mechanical properties. Mechanical property tests show that its ultimate tensile strength is 10.3 MPa, the fracture strain reaches 1386%, and the elastic recovery rate is as high as 55% after 10 cycles at a fixed strain of 300%. It is a potential thermoplastic polyethylene elastomer with great prospects for industrial application.

[0119] According to an eighth aspect of the invention, the use of an intermediate of the structure of formula (II) for preparing a symmetrical α-diimine nickel complex of the structure of formula (I) is provided. The process for preparing the symmetrical α-diimine nickel complex of formula (I) from the intermediate of the structure of formula (II) is as described above.

[0120] The terms used above and below will be clarified here. They are well known to those skilled in the art and have the specific meanings set forth below:

[0121] The term “C1-C6 alkyl” should be understood to mean a linear or branched saturated monovalent hydrocarbon group having 1, 2, 3, 4, 5 or 6 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl or their isomers. In particular, the group has 1, 2, 3 or 4 carbon atoms (“C1-C4 alkyl”), such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl, and more particularly, the group has 1, 2 or 3 carbon atoms (“C1-C3 alkyl”), such as methyl, ethyl, n-propyl or isopropyl.

[0122] The term "C3-C" 10 "Cycloalkyl" should be understood to refer to a saturated monovalent monocyclic or bicyclic hydrocarbon ring having 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. The C3-C... 10 Cycloalkyl groups can be monocyclic hydrocarbon groups, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, or cyclodecyl, or bicyclic hydrocarbon groups such as decahydronaphthalene ring.

[0123] The term "C6-C" 14 "Aryl" should be understood to preferably represent a monovalent aromatic or partially aromatic monocyclic, bicyclic, or tricyclic hydrocarbon ring ("C") having 6, 7, 8, 9, 10, 11, 12, 13, or 14 carbon atoms. 1-14 Aryl), particularly a ring with 6 carbon atoms (“C6 aryl”), such as phenyl; or biphenyl, or a ring with 9 carbon atoms (“C9 aryl”), such as indenyl or indenyl, or a ring with 10 carbon atoms (“C9 aryl”). 10 Aryl groups, such as tetrahydronaphthyl, dihydronaphthyl, or naphthyl, or rings with 13 carbon atoms (“C3 aryl”), such as fluorene, or rings with 14 carbon atoms (“C4 aryl”). 14 Aryl), for example, anthracene.

[0124] The term "alkoxy" refers to an alkyl group bonded by an oxygen atom, the term "cycloalkyloxy" refers to a cycloalkyl group bonded by an oxygen atom, and the term "aryloxy" refers to an aryl group bonded by an oxygen atom.

[0125] When the basic structure is replaced by "one or more groups"—selected from a series of groups or groups as defined in general—it includes, in various cases, being replaced by multiple identical and / or structurally different groups simultaneously.

[0126] The term "halogen" refers to, for example, fluorine, chlorine, bromine, or iodine. If the term is used for a group, "halogen" refers to, for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom.

[0127] Compared with the prior art, the present invention has the following beneficial technical effects:

[0128] 1. The symmetrical α-diimine nickel complex of the present invention has a single catalytic active center, and the molecular weight and branching degree of the polymer can be controlled by changing the ligand structure and polymerization conditions.

[0129] 2. The symmetrical α-diimine nickel complex of the present invention has the advantages of high catalytic activity, low cost and outstanding thermal stability when used as a catalyst, and the preparation method is mild, short cycle and simple operation.

[0130] 3. The symmetrical α-diimine nickel complex of the present invention exhibits high catalytic activity (up to 1.48 × 10⁻⁶) when used as a catalyst for ethylene polymerization. 7 g·mol -1 (Ni)·h -1 It exhibits good thermal stability, and even under reaction conditions at 100℃, its catalytic activity remains at 2.51 × 10⁻⁶. 6 g·mol -1 (Ni)·h -1 It meets the operating temperature requirements for industrial production.

[0131] 4. The polyethylene prepared by using the symmetrical α-diimine nickel complex of the present invention as a catalyst for ethylene polymerization has a high weight-average molecular weight (Mw) of 3.98 × 10⁻⁶. 5 g·mol -1 With a molecular weight distribution between 1.5 and 2.0, it exhibits strong control over the molecular weight of polyethylene, and the obtained polyethylene has a high degree of branching and excellent elastic properties. Mechanical property tests show that its ultimate tensile strength is 10.3 MPa, the maximum breaking strain reaches 1863%, and the strain recovery rate after 10 cycles is as high as 55%, making it a potential thermoplastic polyethylene elastomer. Attached Figure Description

[0132] Figure 1 Synthetic pathway diagrams of the symmetrical α-diimine nickel complexes of formula (I) prepared in Examples 1-8 of the present invention;

[0133] Figure 2A schematic diagram of the crystal structure of the symmetrical α-diimine nickel complex prepared in Example 1 of the present invention;

[0134] Figure 3 A schematic diagram of the crystal structure of the symmetrical α-diimine nickel complex prepared in Example 5 of the present invention;

[0135] Figure 4 The high-temperature carbon NMR spectrum of polyethylene prepared in Application Example 30 of the present invention;

[0136] Figure 5 The high-temperature carbon NMR spectrum of polyethylene prepared in Application Example 37 of the present invention;

[0137] Figure 6 The tensile stress-strain curves of polyethylene prepared in Application Examples 1 and 11-14 of the present invention are shown.

[0138] Figure 7 The stress-strain recovery curve of polyethylene prepared for application example 37 of the present invention.

[0139] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings above are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. It should be noted that these drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0140] To make the technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described more clearly and completely below with reference to the embodiments and accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0141] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0142] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0143] Unless otherwise specified, all concentrations in the following examples are molar concentrations. The hydrochloric acid used was commercially available concentrated hydrochloric acid, purchased from Xilong Scientific Co., Ltd., with a mass fraction between 36.0% and 38.0%. The potassium oxalate aqueous solution used in the following examples was prepared by dissolving potassium oxalate monohydrate in water.

[0144] The molecular weight and molecular weight distribution of the polymers obtained in the following ethylene polymerization examples were determined by conventional high-temperature GPC methods, and the melting points were determined by conventional DSC methods. The polymerization activity of the polymers was calculated using the following formula: Polymerization activity = Polymer yield / (Catalyst dosage × Polymerization time). In this invention, catalytic activity and polymerization activity are the same concept, both used to evaluate the catalytic ability of the catalyst.

[0145] All the synthesized compounds were confirmed by NMR, IR and elemental analysis. NMR was performed using a Bruker DMX 400MHz instrument, elemental analysis was performed using a Flash EA 1112 microanalyzer, and IR analysis was performed using a PerkinElmerSystem 2000FT-IR spectrometer.

[0146] The intermediate preparation example uses the structure of formula (II) to prepare the intermediate of the above-mentioned symmetrical α-diimine nickel complex.

[0147] This invention first uses diphenylmethanol and ortho-substituted aniline of formula (III) to prepare aniline of formula (IV), then reacts it with acenaphthoquinone and zinc chloride to prepare an intermediate product of formula (V), and finally reacts the intermediate product with potassium oxalate to prepare an intermediate of formula (II) of this invention.

[0148] The structure of the intermediate in equation (II) is as follows:

[0149]

[0150] The structure of the ortho-substituted aniline of formula (III) is as follows:

[0151]

[0152] The structure of aniline of formula (IV) is as follows:

[0153]

[0154] The structure of the intermediate product of formula (V) is as follows:

[0155]

[0156] In formulas (II), (III), (IV), and (V), R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C14 Aryl, C6-C 14 Aryloxy group.

[0157] Preferably, in formulas (II), (III), (IV), and (V), the substituted C1-C6 alkyl, C1-C6 alkoxy, C3-C... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 The aryloxy group may optionally be substituted by one or more identical or different R2 groups, wherein the R2 group is selected from halogens (such as F, Cl, Br, I), C1-C6 alkyl groups, C1-C6 alkoxy groups, C3-C6 alkyl groups, and C4-C6 alkoxy groups. 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C14 aryloxy.

[0158] Preferably, in formulas (II), (III), (IV), and (V), R is selected from H, halogens, or unsubstituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

[0159] More preferably, in formulas (II), (III), (IV) and (V), R is selected from halogens, C1-C6 alkyl or C1-C6 alkoxy, particularly preferably halogens or C1-C3 alkyl, such as fluorine, chlorine, bromine, iodine, methyl, ethyl, n-propyl, isopropyl, and most particularly preferably chlorine, methyl, ethyl, isopropyl.

[0160] As an example, the ortho-substituted aniline of formula (III) is 2-methylaniline, 2-ethylaniline, 2-isopropylaniline, or 2-chloroaniline. Correspondingly, as an example, the aniline of formula (IV) obtained in step (S1) is:

[0161] E1: R = Me (methyl), i.e., 2,4-bis(diphenylmethyl)-6-methylaniline;

[0162] E2: R = Et(ethyl), i.e., 2,4-bis(diphenylmethyl)-6-ethylaniline;

[0163] E3: R = i-Pr(isopropyl), i.e., 2,4-bis(diphenylmethyl)-6-isopropylaniline;

[0164] E4: R = Cl (chlorine), i.e., 2,4-bis(diphenylmethyl)-6-chloroaniline.

[0165] Correspondingly, the intermediate of the structure of formula (II) has the structure shown in formulas (II-1), (II-2), (II-3), or (II-4):

[0166]

[0167] In other words, the intermediates of formula (II) prepared in Examples 1-4 below are substances having the following defined groups:

[0168] L1: R = Me (methyl);

[0169] L2: R = Et(ethyl);

[0170] L3: R = i-Pr (isopropyl);

[0171] L4: R = Cl (chlorine).

[0172] The products of the following intermediate preparation examples are obtained through 1 H NMR, 13 Characterized by C NMR, infrared analysis and elemental analysis.

[0173] Preparation of intermediates: Example 1 Preparation of intermediates with the structure of formula (II-1)

[0174] Preparation of aniline with formula (IV): 36.2 mmol diphenylmethanol and 18.1 mmol 2-methylaniline were mixed under stirring, and the mixture was heated to 120 °C and stirred at this temperature for 30 minutes to obtain a homogeneous liquid. Then, a homogeneous mixture of 7.24 mmol zinc chloride and 1.5 mL concentrated hydrochloric acid was added at a dropping rate of 1 drop per second. After mixing, the temperature of the reaction system was raised to 160 °C under stirring and reacted at this temperature for 4 hours to make the entire reaction system a solid. Then, 200 mL of ethanol was added to wash three times to remove impurities to obtain aniline with formula (IV).

[0175] Preparation of the intermediate product of formula (V): 7.13 mmol of aniline of formula (IV) obtained in step (S1), 2.64 mmol of acenaphthene, and 3.0 mmol of zinc chloride were dissolved in 15 mL of acetic acid at a stirring rate of 500 rpm. The mixture was then heated to 135 °C and refluxed. The reaction system gradually turned into a red solution. After 20 min, a slightly reddish solid was formed. The reaction was continued for 6 hours and then cooled to room temperature. The slightly orange-red precipitate was then filtered and washed three times with 100 mL of acetic acid to remove impurities. Finally, the residual acetic acid was removed with 200 mL of n-hexane to obtain the intermediate product of formula (V).

[0176] Preparation of the intermediate of formula (II): 2.6 mmol of the intermediate of formula (V) was dissolved in 30 mL of dichloromethane and mixed with 30 mL of 2% potassium oxalate monohydrate aqueous solution at a stirring rate of 700 rpm. The resulting system was reacted at room temperature and a stirring rate of 700 rpm for 2 h. The organic layer was then separated and washed three times with 100 mL of water. The organic layer was dried with anhydrous sodium sulfate, filtered, and the solvent was removed. Finally, the solid product was dissolved in 30 mL of dichloromethane and then recrystallized in 600 mL of n-hexane to obtain an orange solid, which is the intermediate of formula (II), denoted as L1. The product mass was 3.0 g, and the yield was 97.7%. Its structural formula is shown in formula (II-1).

[0177] The structural characterization data of the product are as follows:

[0178] 1 H NMR (CDCl3, 400MHz, TMS): δ7.60 (d, J = 8.2Hz, 2H, An-H), 7.36-7.17 (m, 16H, Ph-H), 7.16-7.00 (m, 16H, Ph-H), 6.97-6.90 (m, 4H, Ph-H), 6.80-6.72 (m, 4H,Ph-H),6.67(d,J=1.9Hz,2H,An-H),6.37-6.21(m,4H,Ph-H),6.15-6.0 0(m,2H,An-H),5.68(s,2H,2×CH),5.51(s,2H,2×CH),2.21(s,6H,2×CH3).

[0179] 13C NMR (CDCl3, 100MHz, TMS): δ163.05,147.43,144.36,143.33,141.39,139.78,138.82,133.03,129.75,129.60,129.43,129.32,129. 26,129.06,128.86,128.19,128.14,127.84,127.16,126.83,126.15,126.11,125.84,125.10,124.82,122.42,56.25,52.38,18.02.

[0180] FT-IR (KBr, cm -1 ):3088(w),3059(m),3024(s),2940(w),2914(w),2869(w),1667(ν(C=N) ,s),1638(ν(C=N),m),1597(s),1495(s),1467(m),1453(m),1436(m),128 1(w),1246(w),1204(w),1183(w),1157(w),1132(w),1081(m),1034(m),9 26(w),897(w),832(w),779(m),748(m),736(m),700(s),634(w),618(w).

[0181] Elemental analysis: C 78 H 60 Theoretical N2 (1025.35): C, 91.37; H, 5.90; N, 2.73. Experimental: C, 91.25; H, 5.80; N, 2.67.

[0182] Preparation of intermediates according to formula (II-2) in Example 2

[0183] The intermediate of formula (II-2) was prepared according to the preparation process in Example 1 of intermediate preparation, except that 2-methylaniline was replaced with 2-ethylaniline. The product obtained was denoted as L2, and its structural formula was as shown in formula (II-2). The product mass was 2.82 g, and the yield was 91.0%.

[0184] The structural characterization data of the product are as follows:

[0185] 1H NMR (400MHz, CDCl3, 7.26ppm): δ7.59 (d, J=8.2Hz, 2H, An-H), 7.35-7.19 (m, 16H, Ph-H), 7.19 -6.88(m,16H,Ph-H),6.85-6.73(m,4H,Ph-H),6.65(d,J=2.0Hz,2H,An-H),6.31(t,J=7.6Hz, 4H,Ph-H),6.22(d,J=7.2Hz,4H,4Ph-H),6.16-6.01(m,2H,An-H),5.68(s,2H,2×CH),5.53(s ,2H,2×CH),2.71(dq,J=15.1,7.6Hz,4H,2×CH2CH3),2.43(dq,J=15.0,7.5Hz,6H,2×CH2CH3).

[0186] 13 C NMR (101MHz, CDCl3, 77.16ppm): δ162.92,147.00,144.45,144.38,143.51,141.41,138.92,132.85,130.87,129.68,129.41,129.32,129.1 2,128.80,128.17,128.12,128.07,127.82,127.27,127.19,126.69, 126.13,126.09,125.82,124.85,122.80,77.22,56.36,24.15,13.97.

[0187] FTIR(KBr,cm -1 ):3087(w),3057(m),3026(m),2961(w),2928(w),2875(w),1681(ν(C=N),m),1659(ν(C=N),m),1597(s),1497(s),1448(m),1267 (w),1208(w),1183(w),1155(w),1132(w),1085(m),1034(m),926(w),895(w),834(w),781(m),740(m),700(s),632(w),622(w).

[0188] Elemental analysis: C 80 H 64 Theoretical values ​​for N2 (1053.41): C, 91.22; H, 6.12; N, 2.66. Experimental values: C, 91.30; H, 6.18; N, 2.69.

[0189] Preparation of intermediates according to formula (II-3) in Example 3

[0190] The intermediate of formula (II-3) was prepared according to the preparation process in Example 1 of intermediate preparation, except that 2-methylaniline was replaced with 2-isopropylaniline. The product obtained was denoted as L3, and its structural formula was as shown in formula (II-3). The product mass was 1.76 g and the yield was 80%.

[0191] The structural characterization data of the product are as follows:

[0192] 1 H NMR (400MHz, CDCl3, 7.26ppm): δ7.57 (d, J = 8.2Hz, 2H, An-H), 7.39-7.19 (m, 16H, Ph-H), 7.18-6.90 ( m,16H,Ph-H),6.79-6.71(m,4H,Ph-H),6.64(d,J=1.9Hz,2H,An-H),6.32(t,J=7.5Hz,4H,Ph-H),6.1 9(d,J=7.1Hz,4H,Ph-H),6.12(t,J=7.4Hz,2H,An-H),5.64(s,2H,2×CH),5.54(s,2H,2×CH),3.13(p ,J=6.9Hz,2H,2×CH(CH3)2),1.23(d,J=6.8Hz,6H,2×CH(CH3)2),1.03(d,J=6.9Hz,6H,2×CH(CH3)2).

[0193] 13 C NMR (101MHz, CDCl3, 77.16ppm): δ163.13,146.40,144.49,144.45,143.65,141.35,139.04,135.67,132.62,129.64,129.37,129.33,129.2 9,129.21,128.68,128.14,128.11,128.09,127.81,127.29,126.46, 126.11,126.08,125.80,124.92,123.31,56.47,28.04,24.21,23.39.

[0194] FTIR(KBr,cm -1):3088(w),3063(m),3024(m),2963(m),2932(w),2871(w),1681(ν(C=N),m),1661(ν(C=N),s),1600(m),1494(s),1448(s),1383(w), 1369(w),1273(w),1248(w),1204(w),1183(w),1130(w),1079(m),1032(m),924(w),832(w),779(m),740(m),702(s),632(w),620(w).

[0195] Elemental analysis: C 82 H 68 Theoretical values ​​for N2 (1081.46): C, 91.07; H, 6.34; N, 2.59. Experimental values: C, 91.23; H, 6.37; N, 2.62.

[0196] Preparation of intermediates according to formula (II-4) in Example 4

[0197] The intermediate of formula (II-4) was prepared according to the preparation process in Example 1 of intermediate preparation, except that 2-methylaniline was replaced with 2-chloroaniline. The product obtained was denoted as L4, and its structural formula was as shown in formula (II-4). The product mass was 3.30 g, and the yield was 95%.

[0198] The structural characterization data of the product are as follows:

[0199] 1 H NMR (400MHz, CDCl3, 7.26ppm): δ7.63 (d, J=8.3Hz, 2H, An-H), 7.38-7.20 (m, 16H, Ph-H), 7.19-7.04 (m, 16H, Ph-H), 6.97 (t, J=4.5Hz, 4H, Ph-H), 6.8 4(d,J=7.5Hz,4H,Ph-H),6.77(d,J=2.0Hz,2H,An-H),6.41-6.22(m,4H,Ph-H),6.03(t,J=7.4Hz,2H,An-H),5.72(s,2H,2×CH),5.51(s,2H,2×CH).

[0200] 13C NMR (101MHz, CDCl3, 77.16ppm): δ164.29,145.36,143.57,143.46,142.35,14 0.50,140.30,140.19,136.13,129.97,129.55,129.34,129.29,129.27,128. 60,128.45,128.38,128.35,128.21,127.99,127.49,126.90,126.48,126.45,126.12,125.01,122.69,122.30,55.99,52.61,31.59,30.96,22.66,14.14.

[0201] FTIR(KBr,cm -1 ):3089(w),3061(m),3026(s),2955(w),2920(w),2873(w),1671(ν(C=N),s),165 5(ν(C=N),m),1597(s),1551(m),1497(s),1444(s),1410(m),1361(w),1328(w), 1279(m),1267(m),1248(m),1234(m),1212(w),1183(w),1155(w),1114(w),1083 (m),1034(m),924(w),885(w),859(w),824(w),778(m),742(m),702(s),618(m).

[0202] Elemental analysis: C 76 H 54 Theoretical values ​​for Cl2N2 (1066.18): C, 85.62; H, 5.11; N, 2.63. Experimental values: C, 85.74; H, 5.26; N, 2.65.

[0203] Preparation of symmetrical α-diimine nickel complexes of formula (I)

[0204] The specific structure of the symmetrical α-diimine nickel complex of formula (I) of the present invention is as follows:

[0205]

[0206] in,

[0207] R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C6 alkyl, C5-C6 alkyl, C6 ... 10 cycloalkyl, C3-C 10Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 aryloxy group;

[0208] X is selected from halogens.

[0209] As preferred embodiments, the symmetrical α-diimine nickel complexes prepared in the following complex preparation examples have the structures shown in formulas (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7), or (I-8):

[0210]

[0211]

[0212]

[0213] In other words, the symmetrical α-diimine nickel complexes prepared in the following preparation examples can be selected from complexes having the following group definitions:

[0214] C1: R = Me (methyl); X = Br (bromine);

[0215] C2: R = Et (ethyl); X = Br (bromine);

[0216] C3: R = i-Pr (isopropyl); X = Br (bromine);

[0217] C4: R = Cl (chlorine), X = Br (bromine);

[0218] C5: R = Me (methyl); X = Cl (chlorine);

[0219] C6: R = Et (ethyl); X = Cl (chlorine);

[0220] C7: R = i-Pr (isopropyl); X = Cl (chlorine);

[0221] C8: R = Cl (chlorine), X = Cl (chlorine). The products from the preparation examples described below were characterized by infrared and elemental analysis.

[0222] Preparation of Complexes Example 1: Preparation of symmetric α-diimine nickel complexes of formula (I-1)

[0223] Under a nitrogen atmosphere, 0.24 mmol of product L1 and 0.23 mmol of (DME)NiBr2 were dispersed in 10 mL of dichloromethane and stirred at 30 °C for 24 hours. The solvent was then removed, and 10 mL of diethyl ether was added to precipitate the complex. The precipitate was washed with diethyl ether (3 times × 10 mL). After removing the diethyl ether, the symmetrical α-diimine nickel complex (I-1) was obtained, denoted as C1, with a product mass of 0.24 g and a yield of 79%.

[0224] The structural characterization data of the product are as follows:

[0225] FTIR(KBr,cm -1 ):3083(w),3063(m),3028(s),2955(w),2918(w),2872(w),1648(ν(C=N),m),1 622(ν(C=N),m),1600(s),1583(s),1495(s),1471(w),1453(s),1422(w),1295 (w),1257(w),1242(w),1230(w),1208(w),1189(w),1159(w),1140(w),1079(m ),1032(m),920(w),897(w),832(w),779(m),746(m),702(s),636(w),620(w).

[0226] Elemental analysis: C 78 H 60 Theoretical values ​​for Br2N2Ni (1243.85): C, 75.32; H, 4.86; N, 2.25. Experimental values: C, 75.26; H, 4.80; N, 2.20.

[0227] Its crystal structure is shown in Figure 2 .

[0228] Preparation of Complexes Example 2: Preparation of symmetric α-diimine nickel complexes of formula (I-2)

[0229] A symmetrical α-diimine nickel complex with the structure of formula (I-2) was prepared according to the preparation process in Example 1 of the complex preparation. The only difference was that intermediate L1 was replaced with L2. The obtained product was denoted as C2, and its structural formula was as shown in formula (I-2). The product mass was 0.20 g, and the yield was 66%.

[0230] The structural characterization data of the product are as follows:

[0231] FTIR(KBr,cm -1):3087(w),3061(m),3026(s),2971(w),2932(w),2877(w),1646(ν(C=N ),m),1624(ν(C=N),m),1600(s),1583(s),1495(s),1457(s),1420(w), 1338(w),1293(w),1263(w),1224(w),1195(w),1142(w),1081(m),1034 (m),921(w),897(w),830(w),778(m),745(m),702(s),638(w),622(w).

[0232] Elemental analysis: C 80 H 64 Theoretical values ​​for Br2N2Ni (1271.91): C, 75.55; H, 5.07; N, 2.20. Experimental values: C, 75.45; H, 5.03; N, 2.22.

[0233] Preparation of Complexes Example 3: Preparation of symmetric α-diimine nickel complexes of formula (I-3)

[0234] A symmetrical α-diimine nickel complex with the structure of formula (I-3) was prepared according to the preparation process in Example 1 of the complex preparation. The only difference was that intermediate L1 was replaced with L3. The obtained product was denoted as C3, and its structural formula was as shown in formula (I-3). The product mass was 0.25 g, and the yield was 83%.

[0235] The structural characterization data of the product are as follows:

[0236] FTIR(KBr,cm -1 ):3087(w),3063(m),3030(s),2963(w),2928(w),2871(w),1642(ν(C=N),m),1 624(ν(C=N),m),1602(s),1581(m),1495(s),1455(s),1420(w),1385(w),1369 (w),1344(w),1295(w),1259(w),1226(w),1194(w),1130(w),1079(m),1048(w ),1032(m),955(w),902(w),832(w),777(m),742(s),702(s),638(w),622(w).

[0237] Elemental analysis: C 82 H 68Theoretical values ​​for Br2N2Ni (1299.96): C, 75.76; H, 5.27; N, 2.15. Experimental values: C, 75.66; H, 5.28; N, 2.16.

[0238] Preparation of Complexes Example 4: Preparation of symmetric α-diimine nickel complexes of formula (I-4)

[0239] A symmetrical α-diimine nickel complex of formula (I-4) was prepared according to the preparation process in Example 1 of the complex preparation, the only difference being that intermediate L1 was replaced with L4. The obtained product is denoted as C4, and its structural formula is as shown in formula (I-4). The product mass is 0.29 g, and the yield is 96%.

[0240] The structural characterization data of the product are as follows:

[0241] FTIR(KBr,cm -1 ):3087(w),3063(m),3028(s),2961(w),2927(w),2875(w),1651(ν(C=N ),m),1628(ν(C=N),m),1597(s),1557(w),1500(s),1442(m),1424(w), 1297(w),1263(w),1228(w),1187(w),1157(w),1128(w),1079(m),1036 (m),928(w),889(w),832(w),777(m),744(m),702(s),632(w),618(w).

[0242] Elemental analysis: C 76 H 54 Theoretical values ​​for Br2Cl2N2Ni (1284.68): C, 71.06; H, 4.24; N, 2.18. Experimental values: C, 70.98; H, 4.17; N, 2.13.

[0243] Preparation of Complexes Example 5: Preparation of symmetric α-diimine nickel complexes of formula (I-5)

[0244] A symmetrical α-diimine nickel complex of formula (I-5) was prepared according to the preparation process in Example 1 of the complex preparation, the only difference being that (DME)NiBr2 was replaced with NiCl2·6H2O. The obtained product is denoted as C5, and its structural formula is as shown in formula (I-5). The product mass is 0.16 g, and the yield is 72%.

[0245] The structural characterization data of the product are as follows:

[0246] FTIR(KBr,cm -1):3085(w),3057(m),3025(m),2960(w),2925(w),2870(w),1648(ν(C=N),m),1623(ν(C=N),m),1583(s),1493(s),1470(m),1444 (w),1291(w),1246(w),1228(w),1193(w),1155(w),1078(w),1031(m),925(w),832(w),775(m),744(m),695(s),630(w),619(w).

[0247] Elemental analysis: C 78 H 60 Theoretical values ​​for Cl2N2Ni (1154.95): C, 81.12; H, 5.24; N, 2.43. Experimental values: C, 81.10; H, 5.19; N, 2.38.

[0248] Its crystal structure is shown in Figure 3 .

[0249] Preparation of Complexes Example 6: Preparation of symmetric α-diimine nickel complexes of formula (I-6)

[0250] A symmetrical α-diimine nickel complex of formula (I-2) was prepared according to the preparation process in Example 2 of the complex preparation. The only difference was that (DME)NiBr2 was replaced with NiCl2·6H2O2. The obtained product was denoted as C6, and its structural formula was as shown in formula (I-6). The product mass was 0.10 g, and the yield was 45%.

[0251] The structural characterization data of the product are as follows:

[0252] FTIR(KBr,cm -1 ):3085(w),3057(m),3024(m),2970(w),2938(w),2873(w),1647(ν(C=N),m),1623(ν(C=N),m),1583(m),1493(s),1446(w), 1342(w),1291(w),1255(w),1185(w),1154(w),1074(w),1030(m),906(w),827(w),773(m),737(m),694(s),633(w),621(w).

[0253] Elemental analysis: C 80 H 64Theoretical values ​​for Cl2N2Ni (1183.00): C, 81.22; H, 5.45; N, 2.37. Experimental values: C, 81.16; H, 5.42; N, 2.30.

[0254] Preparation of Complexes Example 7: Preparation of symmetric α-diimine nickel complexes of formula (I-7)

[0255] A symmetrical α-diimine nickel complex of formula (I-7) was prepared according to the preparation process in Example 3 of the complex preparation. The only difference was that (DME)NiBr2 was replaced with NiCl2·6H2O. The obtained product was denoted as C7, and its structural formula was as shown in formula (I-7). The product mass was 0.11 g, and the yield was 48%.

[0256] The structural characterization data of the product are as follows:

[0257] FTIR(KBr,cm -1 ):3085(w),3058(m),3024(m),2964(w),2926(w),2869(w),1648(ν(C=N),m),1622(ν(C=N),m),1582(m),1493(s),1445(w),1347 (w),1293(w),1254(w),1184(w),1129(w),1076(w),1029(m),955(w),910(w),827(w),774(m),741(m),695(s),632(w),620(w).

[0258] Elemental analysis: C 82 H 68 Theoretical values ​​for Cl2N2Ni(1211.05): C, 81.33; H, 5.66; N, 2.31. Experimental values: C, 81.28; H, 5.59; N, 2.25.

[0259] Preparation of Complexes Example 8: Preparation of symmetric α-diimine nickel complexes of formula (I-8)

[0260] A symmetrical α-diimine nickel complex of formula (I-8) was prepared according to the preparation process in Example 4 of the complex preparation. The only difference was that (DME)NiBr2 was replaced with NiCl2·6H2O. The obtained product was denoted as C8, and its structural formula was as shown in formula (I-8). The product mass was 0.15 g, and the yield was 66%.

[0261] The structural characterization data of the product are as follows:

[0262] FTIR(KBr,cm -1):3083(w),3058(m),3024(m),2964(w),2924(w),2869(w),1665(ν(C=N), m),1628(ν(C=N),m),1596(m),1551(w),1493(s),1442(m),1408(w),1271 (w),1255(w),1231(w),1179(w),1155(w),1113(w),1076(w),1029(m),10 06(w),921(w),885(w),823(w),771(m),739(m),694(s),629(w),618(w).

[0263] Elemental analysis: C 76 H 54 Theoretical values ​​for Cl4N2Ni (1195.78): C, 76.34; H, 4.55; N, 2.34. Experimental values: C, 76.32; H, 4.66; N, 2.35.

[0264] Application Examples: Preparation of Polyethylene

[0265] In the following application examples, the symmetrical α-diimine nickel complex of formula (I) prepared in the coordination preparation examples is used as the main catalyst, and a co-catalyst is used to catalyze the polymerization of ethylene to prepare polyethylene. The differences in the following application examples are only in the type or amount of catalyst, polymerization time, polymerization temperature, or polymerization pressure.

[0266] Application Example 1

[0267] After evacuating and backfilling with nitrogen twice in a 250 mL stainless steel reactor, ethylene was backfilled once to maintain an ethylene atmosphere in the reactor. The reactor temperature was then stabilized at 30 °C. 2 μmol of the main catalyst Cl was dissolved in 20 mL of toluene, and 0.4 mL of the co-catalyst Et2AlCl (2.0 M / n-hexane solution, where the molar ratio of metallic Al to the central metal Ni of the main catalyst Cl is Al:Ni = 400) and toluene were added to bring the total reaction volume to 100 mL. Ethylene gas was then continuously introduced to maintain the ethylene pressure at 10 atm, and the mixture was stirred and reacted at 30 °C for 30 min. The ethylene inlet was then stopped, and the remaining gas was vented from the reactor. The obtained polyethylene was then rapidly cooled in an ethanol solution acidified with 10% hydrochloric acid and dried to constant weight at room temperature. The resulting polyethylene was denoted as EC1-1.

[0268] Application Examples 2, 3, and 4

[0269] Polyethylene was prepared according to the preparation process in Application Example 1, with the only difference being that 0.4 mL of the co-catalyst Et2AlCl (2.0 M / n-hexane solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 400) was replaced with 0.89 mL of Me2AlCl (0.9 M / n-heptane solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 400), 1.34 mL of MAO (1.5 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 1000), and 0.77 mL of MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 1000), respectively. The resulting products were designated as EC1-2, EC1-3, and EC1-4, respectively.

[0270] Application Examples 5, 6, 7, 8, 9, 10

[0271] Polyethylene was prepared according to the preparation process in Application Example 1, except that the amount of the co-catalyst Et2AlCl (2.0M / n-hexane solution, Al:Ni = 400) was replaced with 0.20mL, 0.30mL, 0.35mL, 0.45mL, 0.50mL, and 0.60mL, respectively. That is, the molar ratio of metal Al in the co-catalyst to the central metal Ni of the main catalyst Cl was 200:1, 300:1, 350:1, 450:1, 500:1, and 600:1, respectively. The obtained products were designated as EC1-5, EC1-6, EC1-7, EC1-8, EC1-9, and EC1-10, respectively.

[0272] Application Examples 11, 12, 13, and 14

[0273] Polyethylene was prepared according to the preparation process in Application Example 1, except that the polymerization temperature of 30°C was replaced with 40°C, 60°C, 80°C, and 100°C, respectively. The resulting products were denoted as EC1-11, EC1-12, EC1-13, and EC1-14, respectively.

[0274] Application Examples 15, 16, 17, 18, 19

[0275] Polyethylene was prepared according to the preparation process in Application Example 1, except that the polymerization time of 30 min was replaced with 5 min, 10 min, 15 min, 45 min, and 60 min. The products obtained were denoted as EC1-15, EC1-16, EC1-17, EC1-18, and EC1-19, respectively.

[0276] Application Examples 20 and 21

[0277] Polyethylene was prepared according to the preparation process in Application Example 1, except that the polymerization pressure of 10 atm was replaced with 5 atm and 1 atm, and the resulting products were denoted as EC1-20 and EC1-21, respectively.

[0278] Application Examples 22, 23, 24, 25, 26, 27, 28

[0279] Polyethylene was prepared according to the preparation process in Application Example 1, except that the main catalyst C1 was replaced with C2, C3, C4, C5, C6, C7, or C8. The products obtained were denoted as EC2-22, EC3-23, EC4-24, EC5-25, EC6-26, EC7-27, and EC8-28, respectively.

[0280] Application Examples 29, 30, 31, 32, 33

[0281] Polyethylene was prepared according to the preparation process in Application Example 4, except that 0.77 mL MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 1000) was replaced with 1.15 mL MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 1500:1), 1.35 mL MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 1750:1), 1.54 mL MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 2000:1), and 1.73 mL MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 2000:1), and 1.73 mL MMAO (2.6 M / toluene solution, where the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst C1 is Al:Ni = 2000:1). The products obtained by mixing MMAO (2.6M / toluene solution, with the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst Cl Al:Ni = 2250:1) and 1.92 mL MMAO (2.6M / toluene solution, with the molar ratio of metal Al in the co-catalyst to the central metal Ni in the main catalyst Cl Al:Ni = 2500:1) are respectively designated as EC1-29, EC1-30, EC1-31, EC1-32, and EC1-33.

[0282] Application Examples 34, 35, 36, and 37

[0283] Polyethylene is prepared according to the preparation process in Application 30, the only difference being that the polymerization temperature of 30℃ is replaced with 40℃, 60℃, 80℃, and 100℃, and the obtained products are respectively denoted as EC1-34, EC1-35, EC1-36, and EC1-37.

[0284] Application Examples 38, 39, 40, 41, 42

[0285] Polyethylene was prepared according to the preparation process in Application Example 27, except that the polymerization time of 30 min was replaced with 5 min, 10 min, 15 min, 45 min, and 60 min. The products obtained were denoted as EC7-38, EC7-39, EC7-40, EC7-41, and EC7-42, respectively.

[0286] Application Examples 43 and 44

[0287] Polyethylene was prepared according to the preparation process in Application Example 27, except that the polymerization pressure of 10 atm was replaced with 5 atm and 1 atm, and the resulting products were denoted as EC7-43 and EC7-44, respectively.

[0288] Application Examples 45, 46, 47, 48, 49, 50, 51

[0289] Polyethylene was prepared according to the preparation process in Application Example 30, except that the main catalyst C1 was replaced with C2, C3, C4, C5, C6, C7, or C8, and the resulting products were designated as EC2-45, EC3-46, EC4-47, EC5-48, EC6-49, EC7-50, and EC8-51, respectively.

[0290] Performance Test Examples

[0291] Performance Testing Example 1: Polymerization Activity, M w PDI, T m Test

[0292] The polymerization activity, weight-average molecular weight (Mw), molecular weight distribution (PDI), and melting point (Tm) of the polyethylene products prepared in Application Examples 1-51 were tested respectively. The weight-average molecular weight and molecular weight distribution were determined by conventional high-temperature GPC method, and the melting point was determined by conventional DSC method. The polymerization activity of the polymer was calculated according to the following formula: Polymer activity = Polymer yield / (Catalyst dosage × Polymerization time). The test results are shown in Table 1 below.

[0293] Table 1 Polymerization activity, M w PDI, T m Test results

[0294]

[0295]

[0296] Note: "--" indicates extremely high branching degree, with no specific melting point.

[0297] In the preparation of polyethylene, when Et2AlCl is used as a co-catalyst (i.e., Application Examples 1, 5-10), when the molar ratio of metallic Al in the co-catalyst to the central metallic Ni of the symmetrical α-diimine nickel complex of formula (I) of the present invention, i.e., the aluminum-nickel ratio, is different, it can be seen that as the aluminum-nickel ratio increases, the polymerization activity first increases and then decreases, and the molecular weight of polyethylene first increases and then decreases; as the polymerization temperature gradually increases (i.e., Application Examples 1, 11-14), the polymerization activity and the molecular weight of the polymer gradually decrease. The melting point of polyethylene is in the range of 68-107°C, indicating that at higher temperatures, the branching increases, leading to the formation of amorphous polymers; as the polymerization time prolongs (i.e., Application Examples 1, 15-19), the catalytic activity of the catalyst changes differently from the change in the molecular weight of polyethylene, with the catalytic activity gradually decreasing and the molecular weight of polyethylene gradually increasing; as the polymerization pressure increases (i.e., Application Examples 1, 20, 21), the catalytic activity of the catalyst increases linearly, and the molecular weight of polyethylene increases with the increase in polymerization pressure. In different thermally stable symmetrical α-diimine nickel complexes of formula (I) of the present invention as the main catalyst (i.e., in Examples 1, 22-28), the interaction of the adjacent space constraint not only improves the catalytic activity of the catalyst, but also has a positive effect on the molecular weight of the prepared polymer. When MMAO is used as a cocatalyst (i.e., in Examples 4, 29-33), the aluminum-nickel ratio specific activity is similar to that when Et2AlCl is used as a cocatalyst. The catalytic activity first increases and then decreases with increasing MMAO concentration. Furthermore, the order of change in polymer molecular weight relative to the increasing aluminum-nickel ratio is consistent with the catalyst system using Et2AlCl as a cocatalyst, also showing a trend of first increasing and then decreasing. At different polymerization temperatures (i.e., in Examples 4, 34-37), the trends in polymerization activity and molecular weight are very similar to those of the catalyst system using Et2AlCl as a cocatalyst. Moreover, with prolonged reaction time (i.e., in Examples 27, 38-42), the polymer yield and molecular weight both increase, while the activity decreases with further time. The activity decreases with increasing N-aryl unit volume. In summary, compared to Et2AlCl as a cocatalyst, MMAO as a cocatalyst exhibits superior catalytic performance with the thermally stable symmetrical α-diimine nickel complex of formula (I) of this invention, and provides better control over the molecular weight, distribution, and melting temperature of the prepared polymer during the preparation of polyolefins.

[0298] Performance Test Example 2: Mechanical Performance Testing

[0299] The mechanical properties of polyethylene prepared in Examples 1, 11, 12, 13, and 14, including tensile strength and elongation at break, were tested. The tests were conducted in accordance with the methods specified in GB / T1040.1-2018, and the results are shown in Table 2 below.

[0300] Table 2 Mechanical Performance Test Results

[0301] Tensile strength (MPa) Elongation at break (%) EC1-1 14.5 1137 EC1-11 11.0 1200 EC1-12 10.9 1235 EC1-13 8.9 1384 EC1-14 10.3 1863

[0302] The mechanical properties of polyethylene are largely influenced by polymer branching and molecular weight. EC1-1 prepared at 30°C has a molecular weight of 2.82 × 10⁻⁶ Mw. 5 g mol -1 The tensile stress was 14.5 MPa, and the highest strain at fracture was 1137%. The ultimate tensile strength of EC1-11 prepared at 40℃ decreased to 11.0 MPa, with an elongation at fracture of 1200%. Similarly, the ultimate tensile strengths of EC1-12, EC1-13, and EC1-14 prepared at 60℃, 80℃, and 100℃, respectively, initially decreased and then increased. This is due to the amorphous properties of the material caused by high branching content; the degree of branching and molecular weight differences led to the initial decrease followed by the increase in ultimate tensile strength. In particular, EC1-14 prepared at 100℃ had a molecular weight of 1.17 × 10⁻⁶. 5 g mol -1 The highest elongation at break was 1863%, indicating that tensile strength is affected by the molecular weight and branch content of polyethylene. Furthermore, the elastic recovery rate of EC1-14 after 10 cycles reached 54.9%, exhibiting typical thermoplastic polyolefin elastomer characteristics. However, the polymer melting point showed a consistent decreasing trend with increasing polymerization temperature, specifically 107–68℃ (EC1-1, EC1-11 to EC1-14) and 96–69℃ (EC1-30, EC1-34 to EC1-37), suggesting that higher reaction temperatures resulted in a greater number of branches. To accurately determine the number of branches in the polyethylene samples (EC1-30 and EC1-37), polyethylene samples (EC1-30 and EC1-37) prepared at 30℃ and 100℃ were tested at 110℃. 13High-temperature nuclear magnetic resonance (NMR) measurements showed that the polyethylene sample prepared at 30°C contained 56 carbons per 1000 carbons, with methyl (61.1%), 1,4-p-methyl (7.6%), 1,6-p-methyl (9.8%), ethyl (2.7%), propyl (3.3%), pentyl (4.9%), and long-branched (10.6%) being the main components. However, when the reaction temperature was 100°C, the number of branches in the polyethylene reached 123 per 1000 carbons, including methyl (61.1%), 1,4-p-methyl (9.1%), 1,6-p-methyl (6.5%), ethyl (2.6%), propyl (2.7%), butyl (7.7%), pentyl (1.6%), and long-branched (8.7%). Furthermore, it is clear that higher temperatures favor the formation of short branches during polymerization at 100°C. Therefore, polyethylene prepared at 100°C has a slightly higher number of short branches. This phenomenon may be due to the chain termination reaction (β-H elimination) being faster than chain propagation, resulting in a lower relative molecular mass of the polymer and a higher proportion of short branches.

[0303] In summary, the test results show that the novel symmetrical α-diimine nickel catalysts of this invention, with sterically hindered diphenylmethyl groups at the ortho and para positions on an N-aryl unit and in combination with other substituents, achieve the goal of controlling the molecular weight and branching degree of the polymer. Furthermore, the complexes possess advantages such as ease of preparation, high catalytic activity, low cost, and high thermal stability. Using these complexes as catalysts for ethylene polymerization can ultimately produce polyethylene elastomers with high molecular weight, narrow molecular weight distribution, high branching degree, and excellent mechanical properties. Therefore, the symmetrical α-diimine nickel catalysts of this invention have broad application prospects for the preparation of polyethylene elastomers.

[0304] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A symmetrical α-diimine nickel complex for synthesizing thermoplastic polyethylene elastomers, characterized in that, The structural formula is as follows (I): Wherein, R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C6 alkyl, C5-C6 alkyl, C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 aryloxy group; X is selected from halogens.

2. The symmetrical α-diimine nickel complex according to claim 1, characterized in that, The substituted C1-C6 alkyl, C1-C6 alkoxy, C3-C 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 The aryloxy group may optionally be substituted by one or more identical or different R2 groups, wherein the R2 group is selected from halogens (such as F, Cl, Br, I), C1-C6 alkyl groups, C1-C6 alkoxy groups, C3-C6 alkyl groups, and C4-C6 alkoxy groups. 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

3. The symmetrical α-diimine nickel complex according to claim 1, characterized in that, The halogen is fluorine, chlorine, bromine, or iodine, with fluorine and / or chlorine being particularly preferred. Preferably, R is selected from halogens, C1-C6 alkyl groups, or C1-C6 alkoxy groups, particularly preferably halogens or C1-C3 alkyl groups, such as methyl, ethyl, n-propyl, and isopropyl, and most particularly preferably chlorine, methyl, ethyl, and isopropyl. Preferably, R is selected from methyl, ethyl, isopropyl, and chlorine, and X is selected from chlorine or bromine. Most preferably, the symmetrical α-diimine nickel complex has the structure shown in formulas (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7), or (I-8):

4. An intermediate for preparing the symmetrical α-diimine nickel complex according to any one of claims 1-3, characterized in that, It has the structure of the following formula (II): Wherein, R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C6 alkyl, C5-C6 alkyl, C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

5. The intermediate according to claim 4, characterized in that, The substituted C1-C6 alkyl, C1-C6 alkoxy, C3-C 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 The aryloxy group may optionally be substituted by one or more identical or different R2 groups, wherein the R2 group is selected from halogens (such as F, Cl, Br, I), C1-C6 alkyl groups, C1-C6 alkoxy groups, C3-C6 alkyl groups, and C4-C6 alkoxy groups. 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 aryloxy group, Preferably, R is selected from H, halogens, or unsubstituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 aryloxy group, More preferably, R is selected from halogens, C1-C6 alkyl groups, or C1-C6 alkoxy groups, particularly preferably halogens or C1-C3 alkyl groups, such as fluorine, chlorine, bromine, iodine, methyl, ethyl, n-propyl, and isopropyl, most particularly preferably chlorine, methyl, ethyl, and isopropyl. Most preferably, the intermediate has a structure having the following formula (II-1), (II-2), (II-3), or (II-4):

6. A method for preparing the intermediate according to any one of claims 4-5, characterized in that, Includes the following steps: Preparation of aniline with (S1) formula (IV): Diphenylmethanol and ortho-substituted aniline with (III) formula are mixed into a homogeneous liquid state, and then a mixture of zinc chloride and hydrochloric acid is added. After mixing evenly, the temperature of the reaction system is raised to above 150°C under stirring, and the reaction is carried out at this temperature for 0.5-4 hours to make the entire reaction system into a solid state, thus obtaining aniline with (IV) formula. Preparation of intermediate product with structure (S2) of formula (V): Dissolve the product obtained in step (S1), acenaphthoquinone and zinc chloride in acetic acid, then stir the mixture and heat it under reflux until a solid is formed. Then continue the reaction at this temperature for 6-36 h, and then perform solid-liquid separation and washing to obtain the intermediate product with structure (V). Preparation of the intermediate of formula (II) (S3): The intermediate of formula (V) was dissolved in an organic solvent and mixed with an aqueous solution of potassium oxalate. The resulting system was reacted at room temperature with stirring for 0.5-3 h. The organic layer was then separated and washed with water, dried with anhydrous sodium sulfate, and subjected to solid-liquid separation. Finally, after removing the organic solvent, the mixture was purified to obtain an orange solid, which is the intermediate of formula (II). The structure of the ortho-substituted aniline of formula (III) is as follows: The structure of aniline of formula (IV) is as follows: The structure of the intermediate product of formula (V) is as follows: In formulas (III), (IV), and (V), R is selected from H, halogen, or unsubstituted or substituted groups of the following: C1-C6 alkyl, C1-C6 alkoxy, C3-C6 alkyl, C4-C5 alkyl, C6-C6 ... 10 cycloalkyl, C3-C 10 Cycloalkyloxy, C6-C 14 Aryl, C6-C 14 Aryloxy group.

7. The method according to claim 6, characterized in that, In step (S1), the molar ratio of ortho-substituted aniline of formula (III) to diphenylmethanol is 1:(2-2.4).

8. A method for preparing the p-shaped α-diimine nickel complex according to any one of claims 1-3, characterized in that, This includes reacting an intermediate of the structure of formula (II) with a nickel-containing compound to obtain a symmetrical α-diimine nickel complex of the structure of formula (I).

9. A catalyst composition, characterized in that, It includes a main catalyst and a co-catalyst, wherein the main catalyst is the symmetrical α-diimine nickel complex according to any one of claims 1-3.

10. Use of the symmetrical α-diimine nickel complex of any one of claims 1-3 and / or the catalyst composition of claim 9, characterized in that, It is particularly preferred as a catalyst for olefin polymerization, and for ethylene polymerization.

11. A method for preparing polyethylene, characterized in that, The symmetrical α-diimine nickel complex of formula (I) and / or the above-described catalyst composition are used as catalysts for the polymerization of ethylene.

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