Phosphonosulfonic acid compounds, nickel catalysts for phosphonosulfonic acid compounds, and methods of making and using the same

Abstract

The disclosure provides a phosphine sulfonic acid compound, a nickel phosphine sulfonic acid catalyst and a preparation method and application thereof, and belongs to the technical field of polyolefin catalysts. The phosphine sulfonic acid compound has a structure as shown in formula (I): formula (I); wherein M1 has a structure as shown in formula (M-1); formula (M-1); M2 has the same structure as M1 or has a structure as shown in formula (M-2): formula (M-2); wherein * represents a connection position; R1, R2, R3 and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, a benzene ring, a C1-C8 alkyl-substituted benzene ring and a C1-C8 alkoxy-substituted benzene ring; and R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, a benzene ring, a C1-C8 alkyl-substituted benzene ring and a nitro group.

Description

Technical Field

[0001] This disclosure relates to the field of polyolefin catalyst technology, and in particular to a phosphonic acid compound, a nickel phosphonic acid catalyst, a preparation method thereof, and its application. Background Technology

[0002] In the exploration of efficient catalysts for olefin polymerization, nickel-based catalysts have consistently attracted widespread attention due to their cost advantages over traditional Ziegler-Natta and metallocene catalysts, their potential tolerance to polar monomers, and their ability to generate polyethylene materials with unique branched structures. Since the breakthrough of Brookhart-type α-diimine nickel catalysts, efforts have been made to overcome the bottlenecks commonly faced by such systems, such as rapid activity decay at high temperatures (e.g., 80°C) and limitations on polymer molecular weight, in order to develop novel catalytic structures with more stable performance and more precise control. Against this backdrop, phosphine-oxygen chelate nickel catalysts, as an important emerging class, have shown significant development potential due to their high flexibility in ligand design and precise control over the electronic / steric environment of the metal center. However, in practical applications, they suffer from poor thermal stability, easy deactivation, and low molecular weight of the polymers prepared. Summary of the Invention

[0003] In view of the above, in order to at least partially solve at least one of the aforementioned technical problems, this disclosure provides a phosphonic acid compound, a nickel phosphonic acid catalyst, a method for preparing the same, and its application. The technical solution provided by this disclosure is as follows.

[0004] As a first aspect of this disclosure, a phosphonic acid compound is provided having a structure as shown in formula (I):

[0005] Formula (I);

[0006] M1 has the structure shown in equation (M-1);

[0007] Formula (M-1);

[0008] M2 has the same structure as M1, or has a structure as shown in equation (M-2):

[0009] Formula (M-2);

[0010] Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

[0011] R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and nitro.

[0012] As a second aspect of this disclosure, a method for preparing a phosphonic acid compound is provided, comprising:

[0013] Compounds M1-X and M2-X react with metallic magnesium to give compounds M1-MgX or M2-MgX, respectively.

[0014] Compounds M1-MgX and M2-MgX react with phosphorus trichloride to give compound M1-PCl-M2.

[0015] In the presence of tert-butyllithium, compound M1-PCl-M2 reacts with benzenesulfonic acid to obtain a phosphonic acid compound with the structure shown in formula (I);

[0016] Formula (I);

[0017] M1 has the structure shown in equation (M-1);

[0018] Formula (M-1);

[0019] M2 has the same structure as M1, or has a structure as shown in equation (M-2):

[0020] Formula (M-2);

[0021] Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

[0022] R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, C1-C8 alkoxy-substituted benzene ring, nitro; X ​​is a halogen.

[0023] As a third aspect of this disclosure, a nickel phosphonate catalyst is provided having a structure as shown in formula (II):

[0024] Formula (II);

[0025] M1 has the structure shown in equation (M-1);

[0026] Formula (M-1);

[0027] M2 has the same structure as M1, or has a structure as shown in equation (M-2):

[0028] Formula (M-2);

[0029] Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

[0030] R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and nitro group;

[0031] R6 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

[0032] As a fourth aspect of this disclosure, a method for preparing a nickel phosphonate sulfonate catalyst is provided, comprising: reacting a phosphonate sulfonic acid compound with a divalent nickel halide in the presence of a reducing agent to obtain a nickel phosphonate sulfonate catalyst; wherein the divalent nickel halide is selected from any one of (DME)NiBr2, [Ni(PPh3)2PhCl], and (Ph)2Ni(C5H5N)Cl.

[0033] As a fifth aspect of this disclosure, an application of a nickel phosphonate catalyst in a polymerization reaction is provided, comprising: catalyzing the polymerization reaction of ethylene with ethylene, α-olefins, polar monomers or co-polar monomers in the presence of a nickel phosphonate catalyst and a co-catalyst.

[0034] Based on the above technical solutions, the phosphonic acid compound, nickel phosphonic acid catalyst, preparation method and application disclosed herein have at least one of the following beneficial effects:

[0035] (1) In the technical solution disclosed herein, the unique electronic structure and steric hindrance of phosphonic acid ligands are utilized to effectively suppress chain transfer reactions during polymerization, thereby significantly improving catalytic activity, achieving efficient polymerization of ethylene under milder conditions, obtaining high molecular weight products, and reducing production costs. In addition, in the nickel phosphonic acid catalyst, the sulfonic acid functional group, due to its unique hydrophilicity, can suppress poisoning caused by polar functional groups or impurities, making the catalytic system more stable and overcoming the problem of easy poisoning of phosphonic acid catalysts in the current ethylene polymerization process.

[0036] (2) In the technical solution disclosed herein, the branching degree, molecular weight and distribution of the polymerization product can be precisely controlled by the electronic synergistic effect between the phosphonic acid ligand and the nickel metal center, thereby achieving the directional design of material properties; in particular, when the nickel phosphonic acid catalyst has an asymmetric structure, the electronic asymmetry on both sides of its nickel center can significantly promote the insertion reaction of the comonomer, thereby exhibiting excellent copolymerization activity and catalytic efficiency. Attached Figure Description

[0037] Figure 1 Infrared spectra of the polar polyethylene prepared in Test Example 7 and the non-polar polyethylene prepared in Test Example 4 of this disclosure;

[0038] Figure 2 The above is the 1H NMR spectrum of the nickel phosphonate catalyst of formula (II-1) obtained in Example 1 of this disclosure. Detailed Implementation

[0039] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0041] In this disclosure, “each independently” means that when there are multiple subjects, they may be the same or different from each other.

[0042] Phosphine-based oxygen-chelated nickel catalysts (such as phosphonophenols and phosphononsulfonates) have shown significant development potential due to their highly flexible ligand design and precise control over the electronic / steric environment of the metal center. In particular, phosphononsulfonic acid ligands, with their unique P=O / S=O bifunctional structure, can stabilize the nickel center through strong chelation, effectively suppressing side reaction pathways such as β-H elimination that lead to deactivation. Furthermore, their tunable coordination mode provides ample design space for optimizing catalytic activity, increasing polymer molecular weight, controlling polyethylene branching, and even achieving copolymerization with functionalized monomers. However, existing nickel phosphononsulfonate catalysts, due to the strong electrophilicity of their nickel (Ni) center metal, easily form dormant species in complexes at high temperatures (e.g., 60°C), leading to decreased stability and deactivation at temperatures above 60°C. Simultaneously, the high chain transfer rate of these catalysts easily generates low-molecular-weight polymers, making them unsuitable for preparing ultra-high molecular weight polymers (number average molecular weight ≥ 1.0 × 10⁻⁶). 6 g / mol) polyethylene.

[0043] In view of this, this disclosure provides a phosphonic acid compound, a nickel phosphonic acid catalyst, its preparation method, and its applications. Utilizing the unique electronic structure and steric hindrance of the phosphonic acid ligand, chain transfer side reactions are suppressed, and catalytic activity and thermal stability are enhanced, enabling efficient polymerization of ethylene under milder conditions (e.g., 70-80°C). Simultaneously, through the synergistic effect of the phosphonic acid ligand and the nickel center, the degree of branching, molecular weight, and distribution of the polymer can be precisely controlled, thereby meeting the diverse application requirements of the material.

[0044] As a first aspect of this disclosure, a phosphonic acid compound is provided having a structure as shown in formula (I): Equation (I); where M1 has the structure shown in Equation (M-1); Equation (M-1); M2 has the same structure as M1, or has the structure shown in Equation (M-2): Formula (M-2); where * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring; R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and nitro.

[0045] According to embodiments of this disclosure, the choice of R4 affects the electronic properties and spatial configuration of the phosphonic acid compound. Specifically, when R4 is a C1-C8 alkyl or alkoxy group, this type of electron-donating group can moderately enhance the electron cloud density of the benzene ring while introducing a certain steric hindrance, causing the phosphonic acid compound to exhibit overall electron-donating properties. When R4 is selected from a benzene ring or an alkoxy-substituted benzene ring, its extended conjugated system further increases the steric hindrance of the phosphonic acid compound and modulates the electronic distribution characteristics of the phosphonic acid compound through the electronic effects of the aromatic ring. When R4 is a nitro group, the strong electron-withdrawing effect reduces the electron cloud density of the phosphorus atom at the center of the ligand, changing the electronic properties of the ligand. Thus, these substituents, through the synergistic effect of steric hindrance and electronic effects, jointly affect the configurational stability and electronic properties of the phosphonic acid compound, laying the foundation for subsequent metal coordination.

[0046] In some embodiments, M1 has the structure shown in formula (M-1), and M2 has the structure shown in formula (M-2), wherein R4 in formula (M-2) is selected from hydrogen, C1-C8 alkyl, and C1-C8 alkoxy. Preferably, R4 is selected from tert-butyl, isopropyl, and methoxy.

[0047] In some embodiments, M1 and M2 both have the structure shown in formula (M-1), and the R1 and R2 substituents in M1 and M2 may be the same or different. For example, R1 in both M1 and M2 is tert-butyl, and R2 in both M1 and M2 is methyl or phenyl.

[0048] According to embodiments of this disclosure, in the phosphonic acid compound, R1, R2, R3, and R5 are each independently selected from C1-C8 alkyl groups, benzene rings, C1-C8 alkyl-substituted benzene rings, and C1-C8 alkoxy-substituted benzene rings; R4 is selected from C1-C8 alkyl groups, C1-C8 alkoxy groups, benzene rings, C1-C8 alkyl-substituted benzene rings, and C1-C8 alkoxy-substituted benzene rings.

[0049] According to embodiments of this disclosure, in phosphonic acid compounds, if R1, R2, R3, R4, and R5 are completely identical, the electron cloud of the phosphonic acid compound is symmetrically distributed, and the molecular rigidity is enhanced, which is beneficial to improving the thermal stability of the catalyst, but will weaken its copolymerization effect; if R1, R2, R3, R4, and R5 are not completely identical, the electron cloud distribution on both sides of the phosphonic acid compound will be different, making it more compatible with different monomers, thereby significantly improving the copolymerization ability of the catalyst with polar monomers.

[0050] According to embodiments of this disclosure, R1, R2, R3, and R5 are each independently selected from any one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, methoxy, ethoxy, isopropoxy, phenyl, 2-methylphenyl, 3,5-dimethylphenyl, 2,4,6-trimethylphenyl, 2-methoxyphenyl, and 4-ethylphenyl; R4 is selected from any one of hydrogen, methyl, isopropyl, tert-butyl, methoxy, phenyl, 4-methylphenyl, and nitro.

[0051] In some embodiments, the phosphonic acid compounds are not limited to those with the structures shown in formulas (I-1)-(I-4), but also include other combinations of phosphonic acid compounds of M1 and M2, which will not be described in detail here.

[0052] , , ,

[0053] .

[0054] As a second aspect of this disclosure, a method for preparing a phosphonic acid compound is provided, comprising: reacting compounds M1-X and M2-X with metallic magnesium, respectively, to obtain compounds M1-MgX or M2-MgX; reacting compounds M1-MgX and M2-MgX with phosphorus trichloride to obtain compound M1-PCl-M2; and reacting compound M1-PCl-M2 with benzenesulfonic acid in the presence of tert-butyllithium to obtain a phosphonic acid compound with the structure shown in formula (I).

[0055] Specifically, the preparation method of phosphonic acid compounds includes: steps A1-A3.

[0056] Step A1: Under the protection of an inert gas, M1-X and M2-X are reacted with metallic magnesium in a first organic solvent to obtain compounds M1-MgX or M2-MgX.

[0057] Step A2: Compounds M1-MgX and M2-MgX react with phosphorus trichloride in the first organic solvent to obtain compound M1-PCl-M2.

[0058] Step A3: Under inert gas protection, M1-PCl-M2 is dissolved in a second organic solvent and cooled. A solution of n-butyllithium is added dropwise and the reaction is carried out. After the reaction is completed, benzenesulfonic acid is added dropwise to continue the reaction, thereby obtaining the phosphonic acid compound with the structure shown in formula (I).

[0059] Equation (I); where M1 has the structure shown in Equation (M-1). Equation (M-1); M2 has the same structure as M1, or has the structure shown in Equation (M-2): Formula (M-2).

[0060] Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring; R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, C1-C8 alkoxy-substituted benzene ring, and nitro; X ​​is a halogen, preferably Br.

[0061] In the embodiments of this disclosure, compounds M1-X and M2-X are used as raw materials to prepare corresponding Grignard reagents (M1-MgX or M2-MgX) by reacting them with metallic magnesium. Subsequently, the obtained Grignard reagents are subjected to a substitution reaction with phosphorus trichloride to obtain compound M1-PCl-M2. Finally, M1-PCl-M2 undergoes a nucleophilic substitution reaction with benzenesulfonic acid to obtain the target phosphine sulfonic acid compound. By selecting the same or different M1-X and M2-X to react with metallic magnesium to prepare Grignard reagents, and then reacting them with phosphorus trichloride, the same or different substituents (M1 and M2) can be introduced onto the phosphine atom. This method can systematically adjust the electronic effects and steric hindrance of the phosphine sulfonic acid compound to optimize its catalytic performance. The phosphine sulfonic acid compound of this disclosure exhibits good functional group tolerance, and its preparation method has the advantages of mild reaction conditions and simple operation.

[0062] According to an embodiment of this disclosure, in step A1, the inert gas is nitrogen; the mass ratio of M1-X or M2-X to magnesium shavings is 1:1; the first organic solvent is tetrahydrofuran; the reaction temperature is 30-50°C, preferably 40°C; and the reaction time is 2-4 hours. After the Grignard reaction is completed, the mixture is used directly in the next step without any further treatment.

[0063] According to embodiments of this disclosure, in step A2, the first organic solvent is tetrahydrofuran; the mass ratio of phosphorus trichloride to M1-MgX or M2-MgX is 1:1; the cooling temperature is -20℃ to 0℃, preferably -10℃; the heating temperature is 15-35℃, preferably 25℃; and the reaction continues for 4-8 hours. After the substitution reaction is completed, dilute hydrochloric acid is added to quench the reaction, and the mixture is then extracted and dried to obtain compound M1-PCl-M2.

[0064] According to an embodiment of this disclosure, in step A3, the inert gas is nitrogen; the mass ratio of M1-PCl-M2 to n-butyllithium and benzenesulfonic acid is 1:1:1; the second organic solvent is tetrahydrofuran; the reaction temperature is -78°C; and the reaction time is 1-2 hours. After the reaction is complete, the resulting reaction solution is purified by column chromatography to obtain a phosphonic acid compound.

[0065] As a third aspect of this disclosure, a nickel phosphonate catalyst is provided having a structure as shown in formula (II): Equation (II); wherein, M1 has the structure shown in Equation (M-1); Equation (M-1); M2 has the same structure as M1, or has the structure shown in Equation (M-2): Formula (M-2); where * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring; R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and nitro; R6 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

[0066] In the embodiments of this disclosure, the unique hydrophilicity of the sulfonic acid functional group effectively inhibits the poisoning of the active center of the nickel phosphonate sulfonate catalyst caused by the adsorption of polar functional groups or impurities, thereby maintaining the long-term stability of the nickel catalytic center. Simultaneously, the phosphonic acid ligand, with its unique electronic structure and steric hindrance effect, can significantly suppress chain transfer reactions during polymerization, effectively improving the overall activity of the catalytic system and thus contributing to the acquisition of polymer products with higher molecular weights. Specifically, substituent R4 can directly affect the electron cloud density of the phosphine atom through its electron-withdrawing or electron-donating ability, and thus indirectly regulate the electronic properties of the central nickel atom through electron transfer via the P-Ni bond. Substituent R6, with its more direct spatial or electronic relationship with the nickel center, can directly affect the electronic properties and coordination microenvironment of the nickel center. The electronic effects of substituents R4 and R6 are transferred to the nickel center through different pathways, jointly affecting the activity, selectivity, and polymerization ability of the nickel phosphonate sulfonate catalyst.

[0067] According to embodiments of this disclosure, R1, R2, R3, R5, and R6 are each independently selected from any one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, methoxy, ethoxy, isopropoxy, phenyl, 2-methylphenyl, 3,5-dimethylphenyl, 2,4,6-trimethylphenyl, 2-methoxyphenyl, and 4-ethylphenyl; R4 is selected from any one of hydrogen, methyl, isopropyl, tert-butyl, methoxy, phenyl, 4-methylphenyl, and nitro.

[0068] According to embodiments of this disclosure, the influence of substituents R1, R2, R3, and R5 on the overall activity of the nickel phosphonate catalyst mainly stems from their steric hindrance effect, while the electronic effect is relatively weak. Through reasonable stereochemical design, the aforementioned groups can provide suitable steric protection for the catalytic active center, effectively suppressing possible deactivation or side reactions during the reaction process, thereby improving the tolerance and lifespan of the catalytic system to a certain extent.

[0069] According to embodiments of this disclosure, R4 and R6 are preferably electron-donating groups, such as methyl, isopropyl, methoxy, etc. When R4 is one of the above-mentioned electron-donating groups, the electron cloud density of the phosphine atom can be enhanced through the electron-donating effect, thereby strengthening the electron supply capability of the phosphine atom to the nickel center and forming an electron-rich nickel metal center. This electronic effect helps to improve the stability of the catalyst, effectively suppress the decomposition of the active center during the reaction process, and thus extend the service life of the catalyst.

[0070] According to embodiments of this disclosure, in the nickel phosphonate catalyst, M1 has a structure as shown in formula (M-1), and M2 has a structure as shown in formula (M-2). When M1 and M2 are groups with different structures, an inherent electronic environment asymmetry can be formed on both sides of the nickel metal center. This difference in electronic effect can effectively regulate the charge distribution of the metal center, significantly promoting the insertion reaction of the comonomer during the polymerization process, thereby exhibiting superior copolymerization activity and catalytic efficiency.

[0071] According to embodiments of this disclosure, in the nickel phosphonate catalyst, M1 and M2 both have the structure shown in formula (M-1), and the substituents R1 and R2 in M1 and M2 are the same or different; R1, R2, R3, and R5 are each independently selected from C1-C8 alkyl, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring; R4 is selected from C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

[0072] According to embodiments of this disclosure, when both M1 and M2 have the structure shown in formula (M-1), the large steric hindrance provided by their diphenylmethyl structure can suppress the chain transfer rate of the polymer and strengthen the structural rigidity of the Ni metal active center, thereby improving the thermal stability of the nickel phosphonate catalyst. When M1 has the structure shown in formula (M-1) and M2 has the structure shown in formula (M-2), in addition to the above-mentioned effects, the asymmetric nickel phosphonate catalyst can also achieve unbalanced regulation of steric and electronic effects through its asymmetric steric hindrance difference, thereby improving the performance of the catalyst in the copolymerization reaction.

[0073] As a fourth aspect of this disclosure, a method for preparing a nickel phosphonic sulfonate catalyst is provided, comprising: reacting a phosphonic sulfonate compound with a divalent nickel halide in the presence of a reducing agent to obtain a phosphonic sulfonate catalyst; wherein the divalent nickel halide is selected from any one of (DME)NiBr2, [Ni(PPh3)2PhCl], and (Ph)2Ni(C5H5N)Cl.

[0074] According to embodiments of this disclosure, by selecting a nickel precursor with a well-defined structure, side reactions can be effectively suppressed, significantly improving the specificity of catalyst synthesis and product purity. By controlling the electronic properties of the nickel precursor, the electron cloud density of the central nickel metal can be further optimized, thereby effectively enhancing the activity and selectivity of the catalyst in olefin polymerization reactions.

[0075] According to embodiments of this disclosure, a phosphonic acid compound reacts with a divalent nickel halide in a third organic solvent, wherein the third organic solvent is selected from tetrahydrofuran; the mass ratio of the phosphonic acid compound, reducing agent, and divalent nickel halide is 1:1.1:1; the reducing agent is preferably sodium hydride; and the reaction time is 24 hours. After the reaction is complete, the reaction solution is filtered, washed, and dried to obtain a nickel phosphonic acid sulfonate catalyst.

[0076] As a fifth aspect of this disclosure, an application of a nickel phosphonate catalyst in a polymerization reaction is provided, comprising: catalyzing the polymerization reaction of ethylene with ethylene, α-olefins, polar monomers or co-polar monomers in the presence of a nickel phosphonate catalyst and a co-catalyst.

[0077] In one specific embodiment, the nickel phosphononsulfonate catalyst exhibits excellent catalytic performance in polymerization reactions. This catalyst can prepare ultra-high molecular weight polyethylene and can directly catalyze the copolymerization of ethylene with polar monomers (e.g., undecenoic acid) or α-olefins (e.g., 1-hexene), and shows good tolerance to polar functional groups without prior protection.

[0078] According to embodiments of this disclosure, the auxiliary catalyst is selected from any one of alkylaluminum, alkylaluminum chloride, alkylaluminoxane, alkylzinc, borates, and organoboranes. Specifically, the alkylaluminum is selected from trimethylaluminum, triethylaluminum, and trioctylaluminum; the alkylaluminoxane is selected from methylaluminoxane; the alkylaluminum chloride is selected from dichloroethylaluminum; the alkylzinc is selected from any one of diethylzinc and dimethylzinc; the borate is selected from any one of triphenylcarbazo(pentafluorophenyl)borate and N,N-di(hexadecyl)phenylammonium tetra(pentafluorophenyl)borate; and the organoborane is selected from tri(pentafluorophenyl)borane.

[0079] According to embodiments of this disclosure, the polar monomer is selected from olefinic acids and olefinic esters, including but not limited to any one of acrylic acid, methacrylic acid, methyl acrylate, n-butyl acrylate, and methyl methacrylate; the α-olefin is selected from C3-C4.10 The α-olefins include, but are not limited to, any one of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and styrene; the copolymer polar monomer is selected from the copolymer monomers of alkyl aluminum and acrylic acid, wherein the alkyl aluminum includes, but is not limited to, any one of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum chloride, and methylaluminoxane, preferably diethylaluminum chloride.

[0080] According to embodiments of this disclosure, the polymerization temperature is 50-70°C, and the polymerization pressure is 1.0-1.5 MPa. Under mild conditions, polyethylene materials meeting ultra-high molecular weight standards and with controllable molecular weight distribution can be efficiently prepared, effectively avoiding catalyst deactivation that may be caused by high temperature and high pressure (such as temperatures greater than 70°C or pressures greater than 1.5 MPa), thus facilitating the acquisition of polyolefin products with excellent mechanical properties.

[0081] In summary, nickel phosphonic acid ligand catalysts exhibit several technological advantages through the unique design of their ligands: the hydrophilicity of the sulfonic acid functional groups in the phosphonic acid ligands effectively inhibits the poisoning of the catalyst's active center by polar impurities, enhancing its stability in complex reaction environments; simultaneously, the significant steric hindrance effect introduced by the M1 and M2 groups in the phosphonic acid ligands effectively suppresses chain transfer side reactions such as β-H elimination, thereby improving the selectivity of the polymerization reaction. This allows the polymerization reaction to proceed efficiently and stably under relatively mild temperature and pressure conditions, reducing energy consumption and safety risks in the production process and contributing to the acquisition of polymer products with higher molecular weights. Furthermore, through the electronic synergistic effect between the phosphonic acid ligands and the nickel metal center, the degree of branching, molecular weight, and distribution of the polymer products can be precisely controlled, enabling the directional design of material properties.

[0082] The present disclosure will be described in detail below with reference to specific embodiments. It should be noted that the described embodiments are merely some, not all, of the embodiments of the present disclosure. Other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative effort are all within the scope of protection of the present disclosure.

[0083] The following examples are provided to illustrate the content of this disclosure, and the specific data given include the synthesis of phosphonic acid ligands, the preparation of nickel phosphonic acid sulfonate catalysts, and the methods and results of ethylene homopolymerization or copolymerization reactions. All operations were performed under anhydrous and oxygen-free conditions. Substances sensitive to air and moisture were stored in glove boxes. All solvents used underwent rigorous drying and dehydration treatment, and ethylene gas was purified using a dehydration and deoxygenation purification column before use. Unless otherwise stated, the raw materials and reagents used in the examples are commercially available products and are directly used in this disclosure.

[0084] The polymerization activity of this embodiment is calculated by the mass of polymer produced per gram of catalyst per hour; the polymer melt index is determined according to GB / T 3682.1-2018 standard; the polar monomer insertion ratio is obtained by nuclear magnetic resonance hydrogen spectroscopy analysis; the viscosity-average molecular weight is determined according to GB / T 1632-2023 standard; the elongation at break is determined according to GB / T 1040.1-2018 standard; and the impact strength is determined according to GB / T 1043.1-2019 standard.

[0085] Example 1: Synthesis of the nickel phosphonate catalyst shown in formula (II-1)

[0086] Step 1: Synthesis of intermediate A1

[0087]

[0088] Under a nitrogen atmosphere, 1 eq of magnesium shavings was added to anhydrous tetrahydrofuran. The mixture was heated to 40°C, and then 1 eq of diphenylmethyl bromide was slowly added dropwise. Heating was immediately stopped after the addition was complete to prevent coupling reaction, and the mixture was refluxed for 2-4 hours to prepare a Grignard reagent solution. Subsequently, 1 eq of phosphorus trichloride was dissolved in anhydrous tetrahydrofuran, cooled to -10°C, and slowly added dropwise to the prepared Grignard reagent solution with stirring. After the addition was complete, the mixture was reacted at -10°C for 2-3 hours, then naturally heated to 25°C and reacted for another 4-8 hours. After the reaction was complete, dilute hydrochloric acid was added to quench the reaction. The quenched reaction solution was transferred to a separatory funnel, extracted with dichloromethane, and the organic phase was collected and dried to obtain intermediate A1.

[0089] Step 2: Prepare intermediate P1 from intermediate A1

[0090]

[0091] Under a nitrogen atmosphere, 1.2 eq-1.5 eq of aluminum trichloride and dichloromethane were added to a 100 mL round-bottom flask, and stirring was started. A mixed solution of 1 eq of intermediate A1 and 1 eq of 1,3,5-trimethylbenzene ring was slowly added dropwise to the reaction system. After the addition was complete, the reaction was carried out at 70-80 °C for 12 h. After the reaction was completed, the reaction solution was slowly poured into a beaker containing ice water, stirred until the solid was completely dissolved, allowed to stand and separate into layers, and the organic phase was separated. The aqueous phase was extracted with dichloromethane, and the organic phases were combined and washed successively with 10% dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine (2 × 30 mL). The organic phase was dried over anhydrous magnesium sulfate for 30 min and then filtered. The solvent was removed from the filtrate under reduced pressure to obtain intermediate P1, which was a brownish-yellow oily substance.

[0092] Step 3: Prepare the phosphonic acid compound as shown in formula (I-1) from intermediate P1.

[0093]

[0094] Under a nitrogen atmosphere, 1 eq of intermediate P1 was dissolved in anhydrous tetrahydrofuran and cooled to -78°C. After complete dissolution, 1 eq of n-butyllithium (n-BuLi) solution was slowly added dropwise, and the resulting suspension was stirred at -78°C for 1-2 h. Subsequently, 1 eq of benzenesulfonic acid was slowly added dropwise to the reaction system to obtain the phosphonic acid compound shown in formula (I-1).

[0095] Step 4: Prepare nickel phosphonate catalyst as shown in formula (II-1) from phosphonic acid compounds as shown in formula (I-1).

[0096]

[0097] Under nitrogen protection, 1 eq of the phosphonic acid compound as shown in formula (I-1), 1.1 eq of sodium hydride, and 1 eq of diphenyl (pyridine)nickel chloride (II) ((Ph)2Ni(C5H5N)Cl) were added to 50 mL of anhydrous tetrahydrofuran, and the mixture was reacted at room temperature for 24 h to obtain a deep red suspension. After the reaction was completed, the reaction solution was washed three times with dichloromethane, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The resulting solid was dried to obtain a yellow powder, which was washed with a hexane / toluene mixed solvent at a volume ratio of 3:1 to obtain the nickel phosphonate catalyst as shown in formula (II-1). Its 1H NMR spectrum is shown below. Figure 2 As shown.

[0098] Example 2: Synthesis of the nickel phosphonate catalyst shown in formula (II-2)

[0099] Step 1: Synthesis of intermediate P2

[0100]

[0101] Under a nitrogen atmosphere, 2 eq of magnesium shavings were added to anhydrous tetrahydrofuran. The mixture was heated to 40°C, and then 2 eq of a tetrahydrofuran solution of 1-((4-isopropylphenyl)bromomethyl)-4-methylbenzene was slowly added dropwise. Heating was immediately stopped after the addition was complete to prevent coupling reaction, and the mixture was refluxed for 2-4 hours to prepare a Grignard reagent solution. 1 eq of phosphorus trichloride was dissolved in anhydrous tetrahydrofuran, cooled to -10°C, and then slowly added dropwise to the prepared Grignard reagent solution with stirring. The reaction was then carried out at -10°C for 2-3 hours, followed by natural heating to 25°C for another 4-8 hours. After the reaction was complete, dilute hydrochloric acid was added to quench the reaction. The quenched reaction solution was transferred to a separatory funnel, extracted with dichloromethane, and the organic phase was collected and dried to obtain intermediate P2.

[0102] Step 2: Prepare phosphonic acid compounds as shown in formula (I-2) from intermediate P2.

[0103]

[0104] Under a nitrogen atmosphere, 1 eq of intermediate P2 was dissolved in anhydrous tetrahydrofuran and cooled to -78°C. After complete dissolution, 1 eq of n-butyllithium (n-BuLi) solution was slowly added dropwise, and the resulting suspension was stirred at -78°C for 1-2 h. Subsequently, 1 eq of benzenesulfonic acid was slowly added dropwise to the reaction system to obtain the phosphonic acid compound as shown in formula (I-2).

[0105] Step 3: Prepare nickel phosphonate catalyst as shown in formula (II-2) from phosphonic acid compounds as shown in formula (I-2).

[0106]

[0107] Under nitrogen protection, 1 eq of the phosphonic acid compound as shown in formula (I-2), 1.1 eq of sodium hydride, and 1 eq of diphenyl (pyridine) nickel chloride (II) were added to 50 mL of anhydrous tetrahydrofuran and reacted at room temperature for 24 h to obtain a dark red suspension. After the reaction was completed, the reaction solution was washed three times with dichloromethane, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained solid was dried to obtain a yellow powder, which was washed with a hexane / toluene mixed solvent at a volume ratio of 3:1 to obtain the nickel phosphonic acid sulfonate catalyst as shown in formula (II-2).

[0108] Example 3: Synthesis of the nickel phosphonate catalyst shown in formula (II-3)

[0109] Step 1: Synthesis of intermediate P3

[0110]

[0111] Under a nitrogen atmosphere, 2 eq of magnesium shavings were added to anhydrous tetrahydrofuran. The mixture was heated to 40°C, and then 2 eq of a tetrahydrofuran solution of 4-((4-isopropylphenyl)bromomethyl)-1,1'-biphenyl was slowly added dropwise. Heating was immediately stopped after the addition was complete to prevent coupling reaction, and the mixture was refluxed for 2-4 hours to prepare a Grignard reagent solution. 1 eq of phosphorus trichloride was dissolved in anhydrous tetrahydrofuran and cooled to -10°C. This solution was then slowly added dropwise to the prepared Grignard reagent solution with stirring. The reaction was continued at -10°C for 2-3 hours after the addition was complete, followed by natural heating to 25°C for another 4-8 hours. After the reaction was complete, dilute hydrochloric acid was added to quench the reaction. The quenched reaction solution was transferred to a separatory funnel, extracted with dichloromethane, and the organic phase was collected and dried to obtain intermediate P3.

[0112] Step 2: Prepare phosphonic acid compounds as shown in formula (I-3) from intermediate P3.

[0113]

[0114] Under a nitrogen atmosphere, 1 eq of intermediate P3 was dissolved in anhydrous tetrahydrofuran and cooled to -78°C. After complete dissolution, 1 eq of n-butyllithium (n-BuLi) solution was slowly added dropwise, and the resulting suspension was stirred at -78°C for 1-2 h. Subsequently, 1 eq of benzenesulfonic acid was slowly added dropwise to the reaction system to obtain a phosphonic acid compound as shown in formula (I-3).

[0115] Step 3: Prepare nickel phosphonate catalyst as shown in formula (II-3) from phosphonic acid compounds as shown in formula (I-3).

[0116]

[0117] Under nitrogen protection, 1 eq of the phosphonic acid compound as shown in formula (I-3), 1.1 eq of sodium hydride, and 1 eq of diphenyl (pyridine) nickel chloride (II) were added to 50 mL of anhydrous tetrahydrofuran and reacted at room temperature for 24 h to obtain a dark red suspension. After the reaction was completed, the reaction solution was washed three times with dichloromethane, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained solid was dried to obtain a yellow powder, which was washed with a hexane / toluene mixed solvent at a volume ratio of 3:1 to obtain the nickel phosphonic acid sulfonate catalyst as shown in formula (II-3).

[0118] Example 4: Synthesis of the nickel phosphonate catalyst shown in formula (II-4)

[0119] Step 1: Synthesis of intermediate A2

[0120]

[0121] Under a nitrogen atmosphere, 1 eq of magnesium shavings was added to anhydrous tetrahydrofuran. The mixture was heated to 40°C, and then 1 eq of a tetrahydrofuran solution of 4,4'-(bromomethylene)bis(tert-butylbenzene) was slowly added dropwise. Heating was immediately stopped after the addition was complete to prevent coupling reaction, and the mixture was refluxed for 2-4 hours to prepare a Grignard reagent solution. 1 eq of phosphorus trichloride was dissolved in anhydrous tetrahydrofuran, cooled to -10°C, and then slowly added dropwise to the prepared Grignard reagent solution with stirring. The reaction was then carried out at -10°C for 2-3 hours, followed by natural heating to 25°C for another 4-8 hours. After the reaction was complete, dilute hydrochloric acid was added to quench the reaction. The quenched reaction solution was transferred to a separatory funnel, extracted with dichloromethane, and the organic phase was collected and dried to obtain intermediate A2.

[0122] Step 2: Prepare intermediate P4 from intermediate A2

[0123]

[0124] Under a nitrogen atmosphere, 1.3 eq of aluminum trichloride and dichloromethane were added to a 100 mL round-bottom flask, and stirring was started. A mixed solution of 1 eq of intermediate A2 and 1 eq of 1,3,5-trimethylbenzene ring was slowly added dropwise to the reaction system. After the addition was complete, the reaction was carried out at 70-80 °C for 12 h. After the reaction was completed, the reaction solution was slowly poured into a beaker containing ice water, stirred until the solid was completely dissolved, allowed to stand and separate into layers, and the organic phase was separated. The aqueous phase was extracted with dichloromethane, and the organic phases were combined and washed successively with 10% dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine (2 × 30 mL). The organic phase was dried over anhydrous magnesium sulfate for 30 min and then filtered. The solvent was removed from the filtrate under reduced pressure to obtain intermediate P4.

[0125] Step 3: Prepare phosphonic acid compounds as shown in formula (I-4) from intermediate P4.

[0126]

[0127] Under a nitrogen atmosphere, 1 eq of intermediate P4 was dissolved in anhydrous tetrahydrofuran and cooled to -78°C. After complete dissolution, 1 eq of n-butyllithium solution (n-BuLi) was slowly added dropwise, and the resulting suspension was stirred at -78°C for 1-2 h. Subsequently, 1 eq of benzenesulfonic acid was slowly added dropwise to the reaction system to obtain the phosphonic acid compound as shown in formula (I-4).

[0128] Step 4: Prepare nickel phosphonate catalyst as shown in formula (II-4) from phosphonic acid compounds as shown in formula (I-4).

[0129]

[0130] Under nitrogen protection, 1 eq of the phosphonic acid compound as shown in formula (I-4), 1.1 eq of sodium hydride, and 1 eq of (4-methoxyphenyl)(phenyl)(pyridine)nickel chloride (II) were added to 50 mL of anhydrous tetrahydrofuran and reacted at room temperature for 24 h to obtain a dark red suspension. After the reaction was completed, the reaction solution was washed three times with dichloromethane, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent. The obtained solid was dried to obtain a yellow powder, which was washed with a hexane / toluene mixed solvent at a volume ratio of 3:1 to obtain the nickel phosphonic acid sulfonate catalyst as shown in formula (II-4).

[0131] Example 5: Synthesis of the nickel phosphonate catalyst shown in formula (II-5)

[0132] Example 5 uses the same method as Example 1 to synthesize nickel phosphonate catalyst, except that the 1,3,5-trimethylbenzene ring in the second step is replaced with 3,5-dimethyl-1-methoxybenzene, and other conditions remain unchanged, to obtain nickel phosphonate catalyst as shown in formula (II-5).

[0133] Example 6: Synthesis of the nickel phosphononsulfonate catalyst shown in formula (II-6)

[0134] Example 6 uses the same method as Example 1 to synthesize nickel phosphonate catalyst, except that the 1,3,5-trimethylbenzene ring in the second step is replaced with 3,5-dimethylbiphenyl, and other conditions remain unchanged, to obtain nickel phosphonate catalyst as shown in formula (II-6).

[0135] Example 7: Synthesis of the nickel phosphononsulfonate catalyst shown in formula (II-7)

[0136] Example 7 uses the same method as Example 1 to synthesize nickel phosphonate catalyst, except that the 1,3,5-trimethylbenzene ring in the second step is replaced with 1,3-dimethyl-5-nitrobenzene, and other conditions remain unchanged, to obtain nickel phosphonate catalyst as shown in formula (II-7).

[0137] Example 8: Synthesis of the nickel phosphononsulfonate catalyst shown in formula (II-8)

[0138] Example 8 uses the same method as Example 1 to synthesize nickel phosphonate catalyst, except that: in step 4, diphenyl (pyridine) nickel chloride (II) is replaced with (4-methylphenyl)(phenyl)(pyridine) nickel chloride (II) (that is, the benzene ring in ((Ph)2Ni(C5H5N)Cl) is replaced with 4-methylphenyl), and other conditions remain unchanged, to obtain nickel phosphonate catalyst as shown in formula (II-8).

[0139] Example 9: Synthesis of the nickel phosphonate catalyst shown in formula (II-9)

[0140] Example 9 uses the same method as Example 1 to synthesize nickel phosphonate catalyst, except that diphenyl (pyridine) nickel chloride (II) in step 4 is replaced with (4-biphenyl)(phenyl)(pyridine) nickel chloride (II), and other conditions remain unchanged, to obtain nickel phosphonate catalyst as shown in formula (II-9).

[0141] The structures of the nickel phosphonate catalysts in Examples 1-9 above are as follows:

[0142] , , , , , ,

[0143] , , .

[0144] Ethylene polymerization activity test

[0145] Test Example 1

[0146] 1.6 L of chromatographic grade heptane was added to a 2.5 L high-pressure reactor and purged with nitrogen. The reaction temperature was then adjusted to 70 °C and the reaction pressure to 0.5 MPa. Ethylene flow was controlled using a flow meter, with the flow rate set to 6000 mL / min. 6 mL of diethylaluminum chloride (DEAC) was added as a co-catalyst, and stirring was started. Subsequently, 40 mg of nickel phosphonate catalyst as shown in formula (II-1) was weighed, dissolved in 3 mL of dichloromethane, and added to the reactor to begin the polymerization reaction, which lasted for 30 min.

[0147] Test Example 2

[0148] Test Example 2 uses the same method as Test Example 1 to test the activity of ethylene polymerization, except that the reaction temperature is changed to 60℃, while other conditions remain the same.

[0149] Test Example 3

[0150] Test Example 3 uses the same method as Test Example 1 to test the activity of ethylene polymerization, except that the reaction temperature is changed to 50℃, while other conditions remain the same.

[0151] Test Example 4

[0152] Test Example 4 uses the same method as Test Example 1 to test the activity of ethylene polymerization, except that the reaction pressure is changed to 1.0 MPa, while other conditions remain the same.

[0153] Test Example 5

[0154] Test Example 5 uses the same method as Test Example 1 to test the activity of ethylene polymerization, except that the reaction pressure is changed to 1.5 MPa, while other conditions remain the same.

[0155] Test Example 6

[0156] Test Example 6 uses the same method as Test Example 1 to test the activity of ethylene polymerization, except that 5 mL of undecenoic acid is added at the beginning of the reaction, while other conditions remain unchanged.

[0157] Test Example 7

[0158] Test Example 7 uses the same method as Test Example 1 to test the ethylene polymerization activity, except that 5 mL of 0.5 M polar comonomer (triethylaluminum-undecenoic acid) is added at the beginning of the reaction, while other conditions remain unchanged.

[0159] Test Example 8

[0160] Test Example 8 uses the same method as Test Example 1 to test the ethylene polymerization activity, except that 5 mL of 1-hexene is added initially, while other conditions remain unchanged.

[0161] Furthermore, infrared spectroscopy tests were performed on the polar polyethylene prepared in Test Example 7 and the non-polar polyethylene prepared in Test Example 4. The specific test results are as follows: Figure 1 As shown.

[0162] Figure 1 Infrared spectra of the polar polyethylene prepared in Test Example 7 and the non-polar polyethylene prepared in Test Example 4 of this disclosure.

[0163] like Figure 1 As shown, at 1701cm -1 The presence of a distinct carbonyl peak indicates that the polar comonomer has entered, demonstrating that the nickel phosphonate catalyst shown in formula (II-1) has a good copolymerization effect.

[0164] Comparative Example 1

[0165] Comparative Example 1 was tested for ethylene polymerization activity using the same method as in Test Example 1, except that the nickel phosphonate catalyst shown in Formula (II-2) was used, while other conditions remained unchanged.

[0166] Comparative Example 2

[0167] Comparative Example 1 was tested for ethylene polymerization activity using the same method as in Test Example 1, except that: the nickel phosphonate catalyst shown in Formula (II-2) was used, and 5 mL of 0.5 M polar comonomer (triethylaluminum-undecenoic acid) was added at the beginning of the reaction, while other conditions remained unchanged.

[0168] The relevant data of the ethylene polymerization reaction obtained from the above tests are shown in Table 1 below.

[0169] Table 1 Ethylene Polymerization

[0170]

[0171] Table 1 shows that the synthesized nickel phosphononsulfonate catalyst exhibits extremely high catalytic activity. As the reaction temperature increases, the catalytic activity rises, but the molecular weight of the resulting polymer decreases accordingly. However, increasing the reaction pressure not only further enhances the catalytic activity but also simultaneously increases the molecular weight of the polymer, with all products meeting the standard for ultra-high molecular weight polyethylene (Mv > 1 million). Most importantly, the catalyst exhibits excellent resistance to poisoning, directly catalyzing the copolymerization of ethylene with polar monomers such as undecenoic acid or α-olefins such as 1-hexene without prior protection of the polar functional groups. A comparison between Test Example 1 and Comparative Example 1 reveals that the asymmetric nickel phosphononsulfonate catalyst significantly outperforms the symmetric catalyst in terms of polymerization activity and polar monomer insertion rate.

[0172] Asymmetric catalysts exhibit significant advantages over symmetrical catalysts in terms of catalytic performance and polar monomer insertion rate due to the electronic and spatial asymmetry induced by the ligand structure. In symmetrical nickel phosphononsulfonate catalysts, the symmetrical electronic and spatial environment of the nickel center results in a uniform electron cloud distribution, which is unfavorable for the effective activation of ethylene molecules. However, in asymmetric nickel phosphononsulfonate catalysts, the two different substituents (such as one strong electron donor and one weak electron donor, or steric hindrance differences) break this symmetry, causing polarization of the nickel center electron cloud and forming a unique asymmetric reaction cavity. This structure not only optimizes the interaction between nickel and the ethylene π bond and lowers the insertion energy barrier, thereby increasing the chain growth rate and overall catalytic activity, but also enhances its tolerance to polar monomers and copolymerization ability.

[0173] Test Example 9

[0174] The homopolymerization of methyl methacrylate (MMA) was carried out using the nickel phosphonate catalyst shown in formula (II-2).

[0175] Under nitrogen protection, 100 mL of toluene, 5 mg of nickel phosphonate catalyst of formula (II-2) and 3 mL of diethylaluminum chloride (DEAC) were added to a Schlenk flask. Methyl methacrylate (MMA) was then added to the system, and the molar ratio of MMA to nickel was controlled at 400:1-2500:1. After stirring at 20 °C for 3 h, methanol was added to quench the reaction. The mixture was filtered, and the solid product was repeatedly washed with methanol until the filtrate was colorless to obtain the polymer.

[0176] Test Case 10

[0177] The mechanical properties of the copolymers obtained in Test Example 1 and Comparative Example 1 were tested, and the test results are shown in Table 2 below:

[0178] Table 2 Mechanical property data

[0179]

[0180] As shown in Table 2, the polymer prepared using the asymmetric nickel phosphononsulfonate catalyst exhibits superior elongation at break and impact strength compared to the product prepared using the symmetric nickel phosphononsulfonate catalyst. This performance advantage is attributed to the effective control of the polymer microstructure by the asymmetric nickel phosphononsulfonate catalyst. Specifically, due to the non-uniform spatial structure of the ligands in the asymmetric catalyst, the active site environment of the nickel center can be more flexibly adjusted. The asymmetry of the electronic environment on both sides of the nickel center more easily promotes the insertion of ethylene during polymerization, forming a moderately branched structure. This structure results in longer polymer chains, allowing for more complete "slip and orientation" of chain segments under stress, thus leading to higher elongation at break. Simultaneously, the longer chains can better absorb impact energy, reducing brittle fracture, thus resulting in superior impact strength corresponding to asymmetric steric hindrance. Therefore, the asymmetric nickel phosphononsulfonate catalyst significantly improves the elongation at break and impact toughness of the material by controlling the polymerization process.

[0181] In summary, nickel phosphononsulfonate catalysts exhibit significant technical advantages in ethylene polymerization and copolymerization. The hydrophilicity of the sulfonic acid functional groups in the ligands effectively suppresses the poisoning of the catalyst's active site by polar impurities, significantly improving its stability in complex reaction environments. Regarding reaction selectivity control, the steric hindrance effect of the ligand skeleton plays a crucial role: by introducing bulky substituents, a specific spatial microenvironment is constructed at the metal center, effectively suppressing chain transfer side reactions such as β-H elimination, allowing the reaction to preferentially proceed in the chain growth direction. Simultaneously, by regulating the electronic properties of the substituents, the electron density of the nickel center can be adjusted, thereby influencing the monomer insertion behavior. This synergistic effect of electronic and steric effects enables the catalyst to precisely control polymer chain structural parameters (such as branching degree and molecular weight distribution), providing new possibilities for developing polyolefin materials with specific properties.

[0182] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A phosphonic acid compound having the structure shown in formula (I): Equation (I); in, M1 has the structure shown in equation (M-1); Formula (M-1); M2 has the same structure as M1, or has a structure as shown in equation (M-2): Formula (M-2); Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring. R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and nitro.

2. The phosphonic acid compound according to claim 1, wherein, Both M1 and M2 have the structure shown in formula (M-1), and the R1 and R2 substituents in M1 and M2 may be the same or different.

3. The phosphonic acid compound according to claim 1 or 2, wherein, R1, R2, R3, and R5 are each independently selected from C1-C8 alkyl, benzene rings, C1-C8 alkyl-substituted benzene rings, and C1-C8 alkoxy-substituted benzene rings; R4 is selected from C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

4. A method for preparing a phosphonic acid compound, comprising: Compounds M1-X and M2-X react with metallic magnesium to give compounds M1-MgX or M2-MgX, respectively. Compounds M1-MgX and M2-MgX react with phosphorus trichloride to give compound M1-PCl-M2. In the presence of tert-butyllithium, the compound M1-PCl-M2 reacts with benzenesulfonic acid to obtain a phosphonic acid compound with the structure shown in formula (I); Equation (I); M1 has the structure shown in equation (M-1); Formula (M-1); M2 has the same structure as M1, or has a structure as shown in equation (M-2): Formula (M-2); Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring. R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, C1-C8 alkoxy-substituted benzene ring, and nitro group; X is a halogen.

5. A nickel phosphonate catalyst having the structure shown in formula (II): Formula (II); in, M1 has the structure shown in equation (M-1); Formula (M-1); M2 has the same structure as M1, or has a structure as shown in equation (M-2): Formula (M-2); Wherein, * indicates the connection position; R1, R2, R3, and R5 are each independently selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring. R4 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and nitro group; R6 is selected from hydrogen, C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

6. The nickel phosphononsulfonate catalyst according to claim 1, wherein, Both M1 and M2 have the structure shown in formula (M-1), and the R1 and R2 substituents in M1 and M2 may be the same or different; R1, R2, R3, and R5 are each independently selected from C1-C8 alkyl, benzene rings, C1-C8 alkyl-substituted benzene rings, and C1-C8 alkoxy-substituted benzene rings; R4 is selected from C1-C8 alkyl, C1-C8 alkoxy, benzene ring, C1-C8 alkyl-substituted benzene ring, and C1-C8 alkoxy-substituted benzene ring.

7. A method for preparing a nickel phosphononsulfonate catalyst, comprising: In the presence of a reducing agent, the phosphonic acid compound as described in any one of claims 1-3 is reacted with a divalent nickel halide to obtain the nickel phosphonic acid catalyst as described in any one of claims 5-7; The divalent nickel halide is selected from any one of (DME)NiBr2, [Ni(PPh3)2PhCl], and (Ph)2Ni(C5H5N)Cl.

8. The application of a nickel phosphonate catalyst as described in any one of claims 5-6 in a polymerization reaction, comprising: Under the action of the nickel phosphonate catalyst and the auxiliary catalyst, the polymerization reaction of ethylene with ethylene, α-olefins, polar monomers or co-polar monomers is catalyzed.

9. The application according to claim 8, wherein: The polar monomers are selected from olefinic acids and olefinic esters; The α-olefin is selected from C3-C4. 10 α-olefins; The copolymer polar monomer is selected from the copolymer monomer of alkyl aluminum and the olefinic acid.

10. The application according to claim 8, wherein, The polymerization reaction is carried out at a temperature of 50-70℃ and a pressure of 1.0-1.5MPa.

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