α-Diimine ligand compound, nickel complex, composite complex and preparation method and application thereof

Abstract

The present invention provides an α-diimine ligand compound, a nickel complex, a composite complex and a preparation method and application thereof, belonging to the technical field of catalytic olefin polymerization. The α-diimine ligand compound has a structure shown in formula (I): #imgabs0# Formula (I); X 1 With X 2 Same, X 1 and X 2 Any one selected from halogen; R 1 With R 3 Same, R 2 With R 4 Same, R 1 , R 2 , R 3 and R 4 They are respectively selected from any one of hydrogen, substituted or unsubstituted C1~C5 alkyl, and substituted or unsubstituted C6~C12 aryl; wherein, when there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of C1~C5 alkyl and C6~C12 aryl.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic olefin polymerization, and in particular to an alpha-diimine ligand compound, a nickel complex, a composite complex, and a preparation method and application thereof. Background Art

[0002] Bimodal polyethylene is an important specialty polyolefin. This type of material combines the superior properties of a low molecular weight portion (stiffness, processing performance, etc.) and a high molecular weight portion (mechanical strength, melt strength, etc.), and has a wide range of uses, wherein the molecular weight of the low molecular weight portion is lower than that of the high molecular weight portion. In the related art, the preparation method of bimodal polyethylene is relatively cumbersome, for example, using an olefin polymerization catalyst to react in multiple series reactors using different process parameters. Summary of the invention

[0003] In view of this, the present invention provides an α-diimine ligand compound, a nickel complex, a composite complex, and a preparation method and application thereof.

[0004] According to an embodiment of one aspect of the present invention, there is provided an α-diimine ligand compound, wherein the α-diimine ligand compound has a structure shown in formula (I):

[0005] Formula (I);

[0006] X1 and X2 are the same, and X1 and X2 are selected from any one of halogen;

[0007] R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl;

[0008] When there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group.

[0009] According to another embodiment of the present invention, an α-diimine nickel complex is provided, wherein the α-diimine nickel complex has a structure shown in formula (II):

[0010] Formula (II);

[0011] R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl;

[0012] Wherein, when there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group;

[0013] R5 is the same as R6, and R5 and R6 are selected from any one of halogen, C1~C6 alkyl, phenyl and substituted phenyl;

[0014] The substituent of the substituted phenyl group includes any one of a C1-C6 alkoxy group, a trifluoromethyl group and a C1-C6 alkyl group.

[0015] According to another embodiment of the present invention, there is provided a composite complex, the composite complex comprising a first complex and a second complex respectively having structures shown in formula (II);

[0016] Formula (II);

[0017] R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl;

[0018] When there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group;

[0019] R5 is the same as R6;

[0020] Wherein, in the above first complex, R5 and R6 are selected from any one of halogens;

[0021] In the above second complex, R5 and R6 are selected from any one of C1~C6 alkyl, phenyl and substituted phenyl, and the substituent of the above substituted phenyl includes any one of C1~C6 alkoxy, trifluoromethyl and C1~C6 alkyl.

[0022] According to another embodiment of the present invention, there is provided a method for preparing the above-mentioned composite complex, comprising the following steps:

[0023] reacting a compound having a structure represented by formula (I) with a divalent nickel salt to obtain a first complex;

[0024] The first complex is subjected to coupling reaction with a Grignard reagent to obtain the composite complex.

[0025] According to another embodiment of the present invention, a method for synthesizing bimodal polyethylene is provided, wherein the composite complex is used as a catalyst to catalyze the polymerization reaction of ethylene monomer to obtain bimodal polyethylene;

[0026] Wherein, the composite complex is the composite complex in the above embodiment or the composite complex prepared by the above composite complex preparation method.

[0027] According to another embodiment of the present invention, there is provided a use of the above-mentioned α-diimine nickel complex or the above-mentioned composite complex as a catalyst in olefin polymerization.

[0028] According to an embodiment of the present invention, on the one hand, the halogen substituent is a coupling reaction site, and on the other hand, the halogen substituent is located at the ortho position of the imine group. When replaced with other substituents through a coupling reaction, the steric hindrance effect of the new substituent can be more directly reflected in the polymerization process.

[0029] According to an embodiment of the present invention, a halogen group is introduced into the α-diimine skeleton, and the halogen group is reacted with a Grignard reagent through a coupling reaction, thereby partially converting the first complex into a second complex, and the content ratio of the first complex and the second complex is controlled by the feed equivalent of the Grignard reagent, thereby preparing a composite complex including the first complex and the second complex.

[0030] According to an embodiment of the present invention, a composite complex including a first complex and a second complex is used to catalyze the polymerization reaction of ethylene monomer to synthesize bimodal polyethylene. The operation process is simple and efficient, which is conducive to large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The single crystal structure of the α-diimine nickel complex provided in Example 1 of the present invention is shown;

[0032] Figure 2 Shown are gel permeation chromatography graphs of polyethylene provided in Examples 8 to 11 of the present invention;

[0033] Figure 3 The gel permeation chromatography curves of the polyethylene provided in Examples 8, 12 to 14 of the present invention are shown. DETAILED DESCRIPTION

[0034] Below, embodiments of the present invention will 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 present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0035] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0036] In the related art, the preparation method of bimodal polyethylene can be, for example, using an olefin polymerization catalyst to synthesize in multiple series reactors using different process parameters, which is a relatively complicated process.

[0037] The present invention is devoted to studying a simple and efficient method for preparing bimodal polyethylene. In the process of realizing the concept of the present invention, it is found that by using an α-diimine skeleton and matching a specific substituent, a halogen group is introduced, and the halogen group can react with a Grignard reagent through a coupling reaction, thereby partially converting the initial catalyst into another catalyst, thereby realizing the in-situ preparation of bimodal polyethylene using one catalyst.

[0038] Specifically, according to an embodiment of one aspect of the present invention, an α-diimine ligand compound is provided, and the α-diimine ligand compound has a structure shown in formula (I):

[0039] Formula (I);

[0040] X1 and X2 are the same, and X1 and X2 are selected from any one of halogen;

[0041] R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl;

[0042] When there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1 to C5 alkyl group and a C6 to C12 aryl group.

[0043] According to an embodiment of the present invention, the substituted or unsubstituted group may be any one of a substituted or unsubstituted C1-C5 alkyl group and a substituted or unsubstituted C6-C12 aryl group.

[0044] Specifically, when there is a substituent on the substituted or unsubstituted C1-C5 alkyl group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group. When there is a substituent on the substituted or unsubstituted C6-C12 aryl group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group.

[0045] According to an embodiment of the present invention, an aniline compound having a structure shown in formula (A) and diacetyl can be dissolved in a methanol solvent, a small amount of formic acid is added, and refluxed for 0.5 to 2 days. After the reaction is completed, the α-diimine ligand compound having a structure shown in formula (I) is obtained by filtration;

[0046] Formula (A).

[0047] According to an embodiment of the present invention, the term "alkyl" refers to a saturated aliphatic hydrocarbon group having a specified number of carbon atoms, either branched or straight. For example, C1 to C5, as defined in "C1 to C5 alkyl", includes groups having 1, 2, 3, 4 or 5 carbon atoms in a straight or branched structure. For example, "C1 to C5 alkyl" specifically includes methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, tert-pentyl, etc.

[0048] According to an embodiment of the present invention, the term "aryl" refers to any stable 6- to 10-membered monocyclic or bicyclic aromatic group, such as phenyl, naphthyl, and the like.

[0049] According to an embodiment of the present invention, when there are substituents on the C1-C5 alkyl group, the number of the substituents may be 1-5.

[0050] According to an embodiment of the present invention, when there are substituents on the C6-C12 aryl group, the number of the substituents may be 1-5.

[0051] According to an embodiment of the present invention, according to an embodiment of the present invention, on the one hand, the halogen substituent is a coupling reaction site, and on the other hand, the halogen substituent is located at the ortho position of the imine group. When replaced by other substituents through a coupling reaction, the steric hindrance effect of the new substituent can be more directly reflected in the polymerization process.

[0052] According to an embodiment of the present invention, R1, R2, R3 and R4 are respectively selected from any one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl and diphenylmethyl;

[0053] X1 and X2 are selected from any one of chlorine, bromine and iodine.

[0054] According to an embodiment of the present invention, when R1, R2, R3 and R4 are selected from the above groups, it is beneficial to react with the Grignard reagent to convert into different catalysts, thereby regulating the synthesis of bimodal polyethylene.

[0055] According to an embodiment of the present invention, the α-diimine ligand compound has a structure shown in any one of Formula (I-1) to Formula (I-7):

[0056] , ,

[0057] , ,

[0058] ,

[0059] ,

[0060] .

[0061] In the process of realizing the concept of the present invention, it is found that the above-mentioned α-diimine ligand compound can be used to prepare a composite complex including a first complex and a second complex. The composite complex is used as a catalyst to catalyze the polymerization reaction of ethylene monomer to produce bimodal polyethylene.

[0062] According to another aspect of the present invention, there is provided a composite complex, the composite complex comprising a first complex and a second complex respectively having structures represented by formula (II);

[0063] Formula (II);

[0064] R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl;

[0065] When there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group;

[0066] R5 is the same as R6;

[0067] Wherein, in the first complex, R5 and R6 are selected from any one of halogens;

[0068] In the second complex, R5 and R6 are selected from any one of a C1-C6 alkyl group, a phenyl group and a substituted phenyl group, and the substituent of the substituted phenyl group includes any one of a C1-C6 alkoxy group, a trifluoromethyl group and a C1-C6 alkyl group.

[0069] According to an embodiment of the present invention, in the second complex, the number of substituents of the substituted phenyl group may be 1 to 5.

[0070] According to an embodiment of the present invention, R1, R2, R3 and R4 are respectively selected from any one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl and diphenylmethyl;

[0071] In the first complex, R5 and R6 are selected from any one of chlorine, bromine and iodine.

[0072] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned composite complex, comprising the following steps:

[0073] reacting an α-diimine ligand compound having a structure represented by formula (I) with a divalent nickel salt to obtain a first complex;

[0074] The first complex is coupled with a Grignard reagent to obtain a composite complex.

[0075] Formula (I);

[0076] X1 and X2 are the same, and X1 and X2 are selected from any one of halogens.

[0077] According to an embodiment of the present invention, the above-mentioned reaction of the α-diimine ligand compound having the structure shown in formula (I) with a divalent nickel salt to obtain the first complex may include:

[0078] The α-diimine ligand compound having the structure shown in formula (I) and the divalent nickel salt are dissolved in an organic solvent and reacted at room temperature for a period of time to obtain a first complex.

[0079] According to an embodiment of the present invention, a halogen group is introduced into an α-diimine skeleton and the halogen group is reacted with a Grignard reagent through a coupling reaction, thereby partially converting the first complex into a second complex, wherein the second complex has a structure different from that of the first complex, and the content ratio of the first complex and the second complex is controlled by the feed equivalent of the Grignard reagent, thereby preparing a composite complex including the first complex and the second complex.

[0080] Specifically, the α-diimine ligand compound having the structure shown in formula (I) and ethylene glycol dimethyl ether nickel bromide are dissolved in dichloromethane and stirred at room temperature for 12 hours to obtain the first complex.

[0081] According to an embodiment of the present invention, coupling reaction of the first complex with a Grignard reagent to obtain a composite complex comprises:

[0082] The first complex and the coupling catalyst are dissolved in a solvent, and a Grignard reagent having a structure represented by formula (III) or formula (IV) is added to react to obtain a composite complex;

[0083] R5MgY formula (III);

[0084] R6MgY formula (IV);

[0085] R5 is the same as R6, and R5 and R6 are selected from any one of a C1-C6 alkyl group, a phenyl group, and a substituted phenyl group, wherein the substituent of the substituted phenyl group includes any one of a C1-C6 alkoxy group, a trifluoromethyl group, and a C1-C6 alkyl group;

[0086] Y is selected from any one of chlorine and bromine.

[0087] According to an embodiment of the present invention, the number of substituents of the substituted phenyl group may be 1 to 5.

[0088] According to an embodiment of the present invention, the Grignard reagent can be, for example, phenylmagnesium bromide, 4-methoxy-phenylmagnesium bromide, 2-methoxy-phenylmagnesium bromide, 4-tert-butyl-phenylmagnesium bromide, phenylmagnesium chloride, 4-methoxy-phenylmagnesium chloride, 2-methoxy-phenylmagnesium chloride, 4-tert-butyl-phenylmagnesium chloride, etc.

[0089] According to an embodiment of the present invention, the coupling catalyst may include at least one of bis(tricyclohexylphosphine)nickel dichloride, 1,3-bis(diphenylphosphine propane)nickel dichloride, 1,2-bis(diphenylphosphine ethane)nickel dichloride and bis(triphenylphosphine)nickel dichloride.

[0090] Specifically, the first complex and the Kumuda coupling catalyst can be dissolved in a tetrahydrofuran solvent in a protective atmosphere (e.g., a nitrogen atmosphere), and the required equivalent of the Grignard reagent is added. After a certain reaction time, the solvent is evaporated, the mixture is dissolved with dichloromethane, and filtered to obtain a mixture solution including the first complex and the second complex.

[0091] According to an embodiment of the present invention, the molar equivalent ratio between the first complex and the Grignard reagent is not particularly limited and can be 1:1 to 1:10, for example, 1:2, 1:4, 1:6, 1:8, 1:10, etc.

[0092] According to another aspect of the present invention, a method for synthesizing bimodal polyethylene is provided, wherein the composite complex is used as a catalyst to catalyze the polymerization reaction of ethylene monomer to obtain bimodal polyethylene;

[0093] Wherein, the composite complex is the composite complex in the above embodiment or the composite complex prepared by the above composite complex preparation method.

[0094] According to an embodiment of the present invention, a simple and efficient bimodal polyethylene preparation technology is provided, which only needs to synthesize a halogen-containing α-diimine nickel complex, which can be partially converted into other α-diimine nickel complexes with different catalytic properties through Kumuda coupling reaction, thereby obtaining a mixture of catalysts to prepare bimodal polyethylene. This method is different from the conventional bimodal polyethylene preparation method, and the operation process is simple and efficient, and there is no need to change the process parameters during the polymerization process, nor is there a need to separate the two synthesized catalysts.

[0095] According to an embodiment of the present invention, the solvent can be first added into the reactor and sealed, and the air can be extracted and ethylene can be introduced while the temperature of the solvent in the reactor is raised to the reaction temperature of 20~120°C. Then, the co-catalyst can be injected into the reactor, and then the composite complex (for example, it can be a mixed solution including the first complex and the second complex obtained as described above) is added, and the ethylene raw material is introduced, and the polymerization reaction is carried out at a pressure of 8~20atm for 5~60min.

[0096] According to an embodiment of the present invention, the solvent for the polymerization reaction can be selected from one or more of toluene, tetrahydrofuran, n-hexane, n-heptane or mixed alkanes, preferably toluene.

[0097] According to an embodiment of the present invention, the co-catalyst may be selected from one or more of aluminoxane, alkylaluminum or alkylaluminum chloride, preferably diethylaluminum chloride.

[0098] According to an embodiment of the present invention, the molar ratio of Al in the co-catalyst to Ni in the composite complex is 50-3500:1, preferably 200.

[0099] According to an embodiment of the present invention, ethylene polymerization is carried out in an ethylene atmosphere, and the ethylene pressure is preferably 8 atm.

[0100] According to an embodiment of the present invention, a composite complex including a first complex and a second complex is used to catalyze the polymerization reaction of ethylene monomer to synthesize bimodal polyethylene. The operation process is simple and efficient, which is conducive to large-scale production and application.

[0101] According to another aspect of the present invention, an α-diimine nickel complex is provided. The α-diimine nickel complex has a structure shown in formula (II):

[0102] Formula (II);

[0103] R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl;

[0104] Wherein, when there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group;

[0105] R5 is the same as R6, and R5 and R6 are selected from any one of halogen, C1~C6 alkyl, phenyl and substituted phenyl;

[0106] The substituent of the substituted phenyl group includes any one of a C1-C6 alkoxy group, a trifluoromethyl group and a C1-C6 alkyl group.

[0107] According to an embodiment of the present invention, the number of substituents of the substituted phenyl group may be 1 to 5.

[0108] According to an embodiment of the present invention, R1, R2, R3 and R4 are respectively selected from any one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl and diphenylmethyl.

[0109] According to another embodiment of the present invention, there is provided a use of the above-mentioned α-diimine nickel complex or the above-mentioned composite complex as a catalyst in olefin polymerization.

[0110] The following lists a number of specific embodiments to illustrate the technical solution of the present invention in detail. It should be noted that the specific embodiments below are only used for illustration and are not used to limit the present invention.

[0111] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0112] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0113] The raw materials used in the following examples have no particular limitation on their purity, but analytically pure materials are preferably used in the present invention.

[0114] Unless otherwise specified, the concentrations in the following examples are molar concentrations.

[0115] The polymerization activities of the catalysts obtained in the following ethylene polymerization examples are calculated according to the following formula: polymerization activity = polymer yield / (catalyst dosage × polymerization time); the molecular weight and molecular weight distribution of the polymer are measured according to the conventional high temperature gel permeation chromatography method; the branching degree of the polymer is calculated according to the high temperature nuclear magnetic resonance hydrogen spectrum method.

[0116] Some of the synthesized compounds described below were confirmed by NMR.

[0117] Example 1

[0118] (1) This embodiment provides an α-diimine ligand compound having a structure shown in formula (I-1);

[0119] Formula (I-1).

[0120] The α-diimine ligand compound having the structure shown in formula (I-1) is prepared by the following method:

[0121] Under nitrogen protection, 2-iodo-4,6-dimethylaniline (5 mmol) and diacetyl (5 mmol) were dissolved in 20 mL of toluene, 0.01 mL of formic acid was added, and refluxed for two days. After the reaction was completed, the α-diimine ligand compound having the structure shown in formula (I-1) was obtained by filtration, with a yield of 80%.

[0122] (2) This embodiment also provides an α-diimine nickel complex having a structure shown in formula (II-1);

[0123] Formula (II-1).

[0124] The α-diimine nickel complex having the structure shown in formula (II-1) is prepared by the following method:

[0125] The α-diimine ligand compound (1 mmol) of formula (I-1) and an equivalent amount of ethylene glycol dimethyl ether nickel bromide were dissolved in 10 mL of dichloromethane, stirred at room temperature for 12 hours, and excess n-hexane was added. The solid powder was filtered and dried to obtain the α-diimine nickel complex (abbreviated as Ni0) of formula (II-1). Its single crystal structure is as follows: Figure 1 shown.

[0126] The above reaction process is shown in Scheme 1:

[0127]

[0128] Route 1

[0129] The α-diimine ligand compound having the structure shown in formula (I-1) prepared above was subjected to nuclear magnetic resonance detection. The detection results are as follows. After analysis, it is consistent with the structural information of the α-diimine ligand compound. 1 H NMR (400 MHz, CDCl3) δ7.65 - 7.45 (m, 2H, Ar-H), 7.10 - 6.96 (m, 2H, Ar-H), 2.28 (s, 6H, N=CCH3), 2.08 (dd, J = 11.5, 7.3 Hz, 12H, Ar-CH3). 13 C NMR (101 MHz, CDCl3) δ 170.23 (N=C), 170.16 (N=C), 148.37, 136.88, 136.74, 134.67, 134.65, 131.36, 131.27,126.04, 125.88, 87.25(IC), 87.15(IC), 20.29, 18.86, 18.81, 16.75, 16.66.

[0130] Embodiment 2~4

[0131] In this embodiment, the α-diimine nickel complex (Ni0) is reacted with 2 equivalents (Example 2), 4 equivalents (Example 3) and 8 equivalents (Example 4) of phenylmagnesium bromide, respectively, so as to partially convert Ni0 into the α-diimine nickel complex (abbreviated as Ni1) shown in formula (II-2), and the specific method is as follows:

[0132] Formula (II-2);

[0133] Under nitrogen atmosphere, the α-diimine nickel complex (50 μmol) shown in formula (II-1) and 1,3-bis(diphenylphosphinopropane) nickel dichloride (10 μmol) and the required equivalent of phenylmagnesium bromide were dissolved in 2 mL of tetrahydrofuran and reacted at room temperature for 1.5 hours. After the reaction, the solvent was drained, dissolved with 5 mL of dichloromethane solvent and filtered to obtain a catalyst solution with a total concentration of Ni0+Ni1 of about 10 mmol / L.

[0134] Example 5

[0135] In this embodiment, the α-diimine nickel complex (Ni0) is reacted with 8 equivalents of 4-methoxy-phenylmagnesium bromide, thereby partially converting Ni0 into the α-diimine nickel complex (referred to as Ni2) shown in formula (II-3), and the specific method is as follows:

[0136] Formula (II-3);

[0137] Under nitrogen atmosphere, α-diimine nickel complex (50 μmol) shown in formula (II-1) was dissolved in 2 mL of tetrahydrofuran with 1,3-bis(diphenylphosphinopropane) nickel dichloride (10 μmol) and 8 equivalents of 4-methoxy-phenylmagnesium bromide, and reacted at room temperature for 1.5 hours. After the reaction, the solvent was drained, dissolved in 5 mL of dichloromethane solvent and filtered to obtain a catalyst solution with a total concentration of Ni0+Ni2 of about 10 mmol / L.

[0138] Example 6

[0139] In this embodiment, the α-diimine nickel complex (Ni0) is reacted with 8 equivalents of 2-methoxy-phenylmagnesium bromide, thereby partially converting Ni0 into the α-diimine nickel complex (referred to as Ni3) shown in formula (II-4), and the specific method is as follows:

[0140] Formula (II-4);

[0141] Under nitrogen atmosphere, α-diimine nickel complex (50 μmol) of formula (II-1), 1,3-bis(diphenylphosphinopropane) nickel dichloride (10 μmol) and 8 equivalents of 2-methoxy-phenylmagnesium bromide were dissolved in 2 mL of tetrahydrofuran and reacted at room temperature for 1.5 hours. After the reaction, the solvent was drained, dissolved in 5 mL of dichloromethane solvent and filtered to obtain a catalyst solution with a total concentration of Ni0+Ni3 of about 10 mmol / L.

[0142] Example 7

[0143] In this embodiment, the α-diimine nickel complex (Ni0) is reacted with 8 equivalents of 4-tert-butyl-phenylmagnesium bromide, thereby partially converting Ni0 into the α-diimine nickel complex (referred to as Ni4) shown in formula (II-5), and the specific method is as follows:

[0144] Formula (II-5);

[0145] Under nitrogen atmosphere, the α-diimine nickel complex (50 μmol) shown in formula (II-1) was dissolved in 2 mL of tetrahydrofuran with 1,3-bis(diphenylphosphinopropane) nickel dichloride (10 μmol) and 8 equivalents of 4-tert-butyl-phenylmagnesium bromide, and reacted at room temperature for 1.5 hours. After the reaction, the solvent was drained, dissolved in 5 mL of dichloromethane solvent and filtered to obtain a catalyst solution with a total concentration of Ni0+Ni4 of about 10 mmol / L.

[0146] Embodiments 8 to 14

[0147] The above NiO and the mixture of NiO and other nickel complexes are used to catalyze ethylene polymerization.

[0148] In a glove box under nitrogen atmosphere, add a stirrer to a 350 mL pressure bottle, add the required toluene and diethylaluminum chloride. Adjust the reaction temperature to the required value, adjust the ethylene pressure, and inject the dichloromethane solution containing the nickel complex. Close the valve, adjust the ethylene pressure to 8 atmospheres, and react for 30 minutes. Stop the reaction, add methanol solution to precipitate the solid, and add a little hydrochloric acid to remove the catalyst. The solid is then washed three times with pure methanol and dried.

[0149] See Table 1, which shows the specific experimental conditions, yield (Yield), catalytic activity (Act.), polymer molecular weight (M) of ethylene polymerization provided by the present invention. w ), polymer molecular weight distribution (PDI), degree of branching (B) and other polymerization result data.

[0150] Table 1

[0151]

[0152] a The polymerization conditions in Table 1 are: 20 mL of toluene, nickel complex = 0.5 μmol dissolved in 0.5 mL of CH2Cl2, Al / Ni = 200, ethylene pressure = 8 atm, time = 10 minutes. b Activity=10 6 g·mol -1 ·h -1 . c The weight average molecular weight (M) was determined by gel permeation chromatography in trichlorobenzene at 150°C. w ) and polydispersity index (PDI). d The degree of branching B ( / 1000C) was determined by high temperature hydrogen nuclear magnetic resonance spectroscopy.

[0153] By comparing the polymerization data of Example 8 with Example 9, it can be found that after Ni0 is partially converted into Ni1 through the Kumuda coupling reaction, the molecular weight of the polyethylene obtained is greatly reduced, indicating that the molecular weight of the polyethylene produced by Ni1 is much smaller than that of the polyethylene produced by Ni0. At the same time, the degree of branching in Example 9 is much smaller than that in Example 8, indicating that the polyethylene produced by Ni1 is highly linear compared to Ni0. The gel permeation chromatography curves of Examples 8-11 (as shown in FIG. Figure 2 As shown in the figure, as the amount of phenylmagnesium bromide used increases, more Ni0 is converted into Ni1, and accordingly, the low molecular weight portion of the obtained bimodal polyethylene gradually increases and the high molecular weight portion gradually decreases. It can be seen from the gel permeation chromatography curves of Examples 12-14 and Example 8 (as shown in the figure) Figure 3 As shown in FIG. 1 ), the parameters of the bimodal polyethylene obtained by using different Grignard reagents are quite different. In summary, in the present invention, the parameters of the bimodal polyethylene can be regulated by the amount of the Grignard reagent and the type of the Grignard reagent.

[0154] The above ethylene polymerization results (e.g., polymerization activity, polymer molecular weight, degree of branching, Figure 2 as well as Figure 3 ), it can be seen that the obtained polyethylene is an obvious bimodal polyethylene, and the content ratio of the low molecular weight part to the high molecular weight part is controlled by the amount and type of the Grignard reagent.

[0155] Embodiment 15

[0156] (1) This embodiment provides an α-diimine ligand compound having a structure shown in formula (I-3);

[0157] Formula (I-3).

[0158] The α-diimine ligand compound having the structure shown in formula (I-3) is prepared by the following method:

[0159] Under nitrogen protection, 2-iodo-4-methyl-6-isopropylaniline (5 mmol) and diacetyl (5 mmol) were dissolved in 20 mL of toluene, 0.01 mL of formic acid was added, and refluxed for two days. After the reaction was completed, an α-diimine ligand compound having a structure shown in formula (I-3) was obtained with a yield of 80%.

[0160] (2) This embodiment also provides an α-diimine nickel complex having a structure shown in formula (II-6);

[0161] (II-6).

[0162] The α-diimine nickel complex having the structure shown in formula (II-6) is prepared by the following method:

[0163] The α-diimine ligand compound (1 mmol) shown in formula (I-3) and an equivalent amount of ethylene glycol dimethyl ether nickel bromide are dissolved in 10 mL of dichloromethane, stirred at room temperature for 12 hours, excess n-hexane is added, solid powder is filtered out, and the α-diimine nickel complex shown in formula (II-6) is obtained by drying.

[0164] The above reaction process is shown in Scheme 2:

[0165]

[0166] Route 2

[0167] The α-diimine ligand compound having the structure shown in formula (I-3) obtained above was subjected to nuclear magnetic resonance detection. The detection results are as follows. After analysis, it is consistent with the structural information of the α-diimine ligand compound. 1 H NMR (400 MHz, CDCl3) δ7.62 (d, J = 2.4 Hz, 2H, Ar-H), 7.22 (dd, J = 1.9, 1.1 Hz, 2H, Ar-H), 3.15 -3.06 (m, 2H, CH(CH3)2), 2.35 (s, 6H, Ar-CH3), 2.12 (s, 6H, C=NCH3), 1.30 (d, J= 6.2 Hz, 12H, CH(CH3)2). 13C NMR (101 MHz, CDCl3) δ 167.44 (N=C), 167.17 (N=C), 145.70, 145.62, 141.31, 139.54, 139.18, 127.87, 89.31(IC), 30.68, 23.99,21.14, 18.55, 15.64.

[0168] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite complex, characterized in that: The following steps are involved: reacting an α-diimine ligand compound having a structure represented by formula (I) with a divalent nickel salt to obtain a first complex; Carrying out a coupling reaction between the first complex and a Grignard reagent to obtain the composite complex; Formula (I); R1 is the same as R3, R2 is the same as R4, and R1, R2, R3 and R4 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C5 alkyl, and substituted or unsubstituted C6-C12 aryl; When there is a substituent on the substituted or unsubstituted group, the substituent is selected from any one of a C1-C5 alkyl group and a C6-C12 aryl group, and the number of the substituent is 1 to 5; X1 and X2 are the same, and X1 and X2 are selected from any one of halogen; The composite complex comprises a first complex and a second complex respectively having structures shown in formula (II); Formula (II); R5 is the same as R6; Wherein, in the first complex, R5 and R6 are selected from any one of halogens; In the second complex, R5 and R6 are selected from any one of a C1-C6 alkyl group, a phenyl group and a substituted phenyl group, and the substituent of the substituted phenyl group is selected from any one of a C1-C6 alkoxy group, a trifluoromethyl group and a C1-C6 alkyl group.

2. The preparation method according to claim 1, characterized in that: R1, R2, R3 and R4 are independently selected from any one of hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl and diphenylmethyl; In the first complex, R5 and R6 are selected from any one of chlorine, bromine and iodine.

3. The preparation method according to claim 1, characterized in that: The coupling reaction of the first complex with a Grignard reagent to obtain the composite complex comprises: The first complex and the coupling catalyst are dissolved in a solvent, and a Grignard reagent having a structure represented by formula (III) or formula (IV) is added to react to obtain the composite complex; R5MgY formula (III); R6MgY formula (IV); R5 is the same as R6, and R5 and R6 are selected from any one of a C1-C6 alkyl group, a phenyl group, and a substituted phenyl group, wherein the substituent of the substituted phenyl group is selected from any one of a C1-C6 alkoxy group, a trifluoromethyl group, and a C1-C6 alkyl group; Y is selected from any one of chlorine and bromine.

4. The preparation method according to any one of claims 1 to 3, characterized in that The α-diimine ligand compound has a structure shown in any one of formula (I-1) to formula (I-7): ， ， ， ， ， ， 。 5. The preparation method according to any one of claims 1 to 3, characterized in that The Grignard reagent is selected from any one of phenylmagnesium bromide, 4-methoxy-phenylmagnesium bromide, 2-methoxy-phenylmagnesium bromide, 4-tert-butyl-phenylmagnesium bromide, phenylmagnesium chloride, 4-methoxy-phenylmagnesium chloride, 2-methoxy-phenylmagnesium chloride and 4-tert-butyl-phenylmagnesium chloride.

6. A composite complex obtained by the preparation method according to any one of claims 1 to 5.

7. A method for synthesizing bimodal polyethylene, characterized in that: The composite complex is used as a catalyst to catalyze the polymerization reaction of ethylene monomer to obtain bimodal polyethylene; Wherein, the composite complex is the composite complex described in claim 6 or the composite complex prepared by the preparation method described in any one of claims 1 to 5.

8. Use of the composite complex according to claim 6 as a catalyst in olefin polymerization.

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