Bidentate phosphine ligands, processes for their preparation and use

Abstract

The application discloses a bidentate phosphine ligand shown in the following general formula 1 and a preparation method thereof, a catalyst solution system prepared from the ligand, and application of the catalyst solution system in isomerization of 2-methyl 3-butenenitrile. The bidentate phosphine ligand is a compound containing calix[4]arene, wherein the calix[4]arene is used as a skeleton, a phosphorus-containing substituent part is arranged at 1,3-positions of an upper edge of the calix[4]arene, and a crown ether structure part is arranged at 2',4'-positions of a lower edge of the calix[4]arene. The catalyst solution system containing the bidentate phosphine ligand has high catalytic capacity for isomerization of 2M3BN, and conversion rate and selectivity are obviously improved; a Lewis acid does not need to be added as an auxiliary agent, cost and a post-processing process are reduced, the catalyst is stable in nature, catalytic performance is not obviously reduced after multiple circulation and application, the catalyst can be used in cooperation with existing trialkylphenyl phosphite in industrial production, equipment does not need to be modified, and cost increase caused by technical transformation is further reduced.

Description

Technical Field

[0001] This invention relates to the field of homogeneous catalysis technology, and in particular to a bidentate phosphine ligand and its preparation method, as well as a catalyst solution system prepared from the ligand, and the application of the catalyst solution system in the isomerization of 2-methyl-3-butenonitrile. Background Technology

[0002] The butadiene-based process for preparing adiponitrile consists of three steps: primary hydrocyanation, isomerization, and secondary hydrocyanation. In the primary hydrocyanation, in addition to generating the linear product 3-pentenonitrile (3PN), a certain amount of the branched byproduct 2-methyl-3-butene (2M3BN) is also produced. Isomerization involves converting 2M3BN generated in the primary hydrocyanation back into 3PN to further improve the yield. Two problems still exist in this process: 1. Generally, in industry, NiL4 (L stands for phosphite ligand) is used as a catalyst, and Lewis acids such as zinc chloride, triphenylboron, and aluminum chloride are used as promoters to promote the isomerization of 2M3BN to 3PN. Without the participation of Lewis acids, the isomerization conversion rate of 2M3BN is only 1-2%. Adding Lewis acids can improve the isomerization conversion rate, but it will seriously reduce the reaction rate. The order of catalytic effect is aluminum chloride < zinc chloride < triphenylboron, and the effect on the reaction rate is triphenylboron > zinc chloride > aluminum chloride. There is a contradiction between high isomerization selectivity and slow reaction rate. 2. In the existing industrial methods, the conversion rate of 2M3BN is about 85%. At the same time, by-products such as 2-methyl-2-butenonitrile (2M2BN) and 2-pentenonitrile (2PN) are generated. This not only reduces the yield of 3PN, but also easily causes catalyst decomposition and deactivation, and generates nickel dicyanoate, which is deposited on the reactor surface and inside the pipeline, causing the plant to shut down.

[0003] Currently, the catalysts used in existing technologies, whether monodentate or multidentate phosphine ligands, are often single phosphine ligand catalysts, such as CN1169143A, CN1914157A, and CN1875025A. However, the catalytic performance of these catalysts is still not ideal, so it is still necessary to develop new catalysts to improve the yield. Summary of the Invention

[0004] To address the shortcomings of existing technologies and the demands of industrial production, this invention provides a bidentate phosphine ligand and its preparation method, a catalyst solution system containing the ligand and its preparation method, and the application of this catalyst solution system in the isomerization of 2M3BN to 3PN. This catalyst solution system possesses advantages such as high catalytic activity, stable properties, and ease of preparation, which helps to solve existing problems in the adiponitrile industry.

[0005] According to one aspect of the present invention, one object of the present invention is to provide a bidentate phosphine ligand, said bidentate phosphine ligand being a compound containing calix[4]arene, the structure of which is shown in general formula 1 below, wherein the calix[4]arene is used as the backbone, a phosphorus-containing substituent is present at the 1,3-position of the upper edge of the calix[4]arene, and a crown ether structure is present at the 2',4'-position of the lower edge of the calix[4]arene:

[0006]

[0007] Wherein, the 1,3-position substitution The phosphorus-containing substituent moiety, wherein X1 and X2 are each independently selected from substituted or unsubstituted C6-C14 aryl, C6-C14 aryl C1-C6 alkyl, C6-C14 aryl C1-C6 alkoxy, and C1-C10 alkyl, wherein the "substituted" in the substituted C6-C14 aryl means that the C6-C14 aryl contains one or two substituents each independently selected from C1-C6 alkyl and C1-C6 alkoxy;

[0008] The 2',4'-bit It is a crown ether structure part, selected from one of crown ethers, azacrown ethers, and aromatic cyclic crown ethers.

[0009] Preferably, the crown ether structure is selected from one of the following structures, wherein It is a simplified formula of calix[4] aromatics and phosphorus-containing substituents;

[0010]

[0011] Preferably, X1 and X2 are each independently selected from one or two of the following: phenyl, ortho-C1-C6 alkylphenyl, meta-C1-C6 alkylphenyl, p-C1-C6 alkylphenyl, ortho-C1-C6 alkoxyphenyl, meta-C1-C6 alkoxyphenyl, p-C1-C6 alkoxyphenyl, 1-naphthyl, 2-naphthyl, cyclohexyl, tert-butyl, 2,4-dimethylphenyl, 2,4-di-tert-butylphenyl, and 2,4-dimethoxyphenyl.

[0012] Preferably, X1 and X2 are each independently selected from phenyl, o-methylphenyl, m-methylphenyl, p-methylphenyl, o-methoxyphenyl, m-methoxyphenyl, p-methoxyphenyl, o-ethoxyphenyl, m-ethoxyphenyl, p-ethoxyphenyl, o-propoxyphenyl, m-propoxyphenyl, and p-propoxyphenyl.

[0013] According to another aspect of the present invention, a second object of the present invention is to provide a method for preparing the bidentate phosphine ligand, the method comprising the following steps:

[0014] 1) The precursor of the polyether structure, calix[4] aromatics and solvent were added to the reactor and reacted to obtain calix[4]-2',4'-crown ether intermediate;

[0015] 2) The calix[4]-2',4'-crown ether intermediate obtained in step 1), the phosphine-containing substituent precursor, solvent, and reducing agent are added to the reactor to react and obtain the final bidentate phosphine ligand product with phosphine-containing substituent modified at the 1,3-position.

[0016] Preferably, step 1) is carried out according to the following method: using an inorganic base as an acid-binding agent and a template agent, the calix[4]-2',4'-crown ether intermediate is obtained by reacting the p-toluenesulfonate of polyether diol with calix[4] aromatics;

[0017] Alternatively, step 1) can be carried out as follows: a bimolecular nucleophilic substitution reaction is used to directly cyclize a mixture of calix[4] aromatics and polyether diols in the presence of organophosphorus compounds and dialkyl azodicarbonate to obtain the product.

[0018] Preferably, the polyether diol is selected from triethylene glycol, tetraethylene glycol, pentaethylene glycol, 1,2-di(hydroxyethoxy)cyclohexane, 1,2-di(hydroxyethoxy)diphenyl ether, 1,3-di(hydroxyethoxy)diphenyl ether, and 3,9-dioxa-6-aza-1,11-undecanediol.

[0019] Preferably, the p-toluenesulfonate of the polyether diol is selected from the p-toluenesulfonates of the following substances: triethylene glycol, tetraethylene glycol, pentaethylene glycol, 1,2-di(hydroxyethoxy)cyclohexane, 1,2-di(hydroxyethoxy)diphenyl ether, 1,3-di(hydroxyethoxy)diphenyl ether, and 3,9-dioxa-6-aza-1,11-undecanediol.

[0020] In method one of step 1), the base is an alkali metal carbonate, alkoxy compound, hydride, etc., such as one or more of sodium carbonate, potassium carbonate, cesium carbonate, potassium tert-butoxide, and sodium hydride. Preferably, when the crown ether structure is C4, C4CH, C4PH, or C4NA, sodium carbonate is used as the base; when the crown ether structure is C5 or azaC5, potassium carbonate is used as the base; and when the crown ether structure is C6, cesium carbonate is used as the base.

[0021] Preferably, in step 1), the molar ratio of the base to the calix[4] aromatic hydrocarbon is 3:1 to 5:1, preferably 3:1.

[0022] Preferably, in step 1), the molar ratio of calix[4] aromatic hydrocarbon to polyether p-toluenesulfonate is 1:1 to 5, more preferably 1:1.1 to 1.5.

[0023] Preferably, the solvent in step 1) of method one is selected from acetonitrile, acetone, tetrahydrofuran, methyltetrahydrofuran, etc., more preferably acetonitrile, and the amount of solvent added is 5-50 times the mass of calix[4] aromatic hydrocarbon, preferably 20-30 times.

[0024] Preferably, the reaction time in step 1) of method one is 6–36 h, more preferably 18–24 h.

[0025] Preferably, in step 1) of method two, the molar ratio of cup[4] aromatic hydrocarbon to polyether glycol is 1:1 to 5, preferably 1:1.05 to 1.20, and more preferably 1:1 to 1.2.

[0026] Preferably, in step 1), the molar ratio of the organophosphorus compound, the dialkyl azodicarbonate, and the calix[4] aromatic hydrocarbon is 2:2:1.

[0027] Preferably, the solvent in step 1) of method 2 is tetrahydrofuran, methyltetrahydrofuran or acetonitrile, and the amount added is 1–100 times the mass of calix[4] aromatic hydrocarbon, preferably 3–10 times; the reaction temperature is 0–40℃, preferably room temperature.

[0028] Preferably, the organophosphorus compound mentioned in step 1) of method two is triphenylphosphine, tributylphosphine, etc., and triphenylphosphine is preferred.

[0029] Preferably, the solvent in step 1) of method two is selected from acetonitrile, acetone, tetrahydrofuran, methyltetrahydrofuran, etc., more preferably acetonitrile, and the amount of solvent added is 3-10 times the mass of calix[4] aromatic hydrocarbon, preferably 4-5 times.

[0030] Preferably, the reaction time in method two of step 1) is 6–36 h, more preferably 6–12 h.

[0031] Preferably, the phosphorus-containing substituent precursor in step 2) has an HPX1X2 structure, wherein X1 and X2 are defined in the same way as in general formula 1.

[0032] More specifically, the method includes the following steps:

[0033] Step 1) Modify the 1,3-position of the upper edge of the calix[4]-2',4'-crown ether intermediate to obtain a calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate with two aldehyde groups modified at the 1,3-position of the upper edge;

[0034] Step 2) Under acidic conditions, the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate obtained in step 1) reacts with a disubstituted phosphine compound, and then in the presence of a haloalkane and a reducing agent, the final bidentate phosphine ligand product is obtained.

[0035] In step 1) of forming a bidentate phosphine ligand on the upper edge of the calix[4]-2',4'-crown ether, the 1,3-position of the upper edge of the calix[4]-2',4'-crown ether is first modified, and then reacted with the corresponding phosphine compound to obtain the product through substitution, reduction and other methods.

[0036] Preferably, the method for modifying the 1,3-position of the upper edge of the calix[4]-2',4'-crown ether intermediate in step 1) can be carried out in accordance with existing literature, or a preparation route can be determined by selecting corresponding steps and reactants. For example, in some embodiments, the method disclosed in Tetrahedron, 2008, 64, 741-748 is used: the calix[4]-2',4'-crown ether intermediate is mixed with a certain amount of hexamethylenetetramine, and under the action of trifluoroacetic acid, calix[4]-2',4'-crown ether-1,3-dialdehyde with two aldehyde groups modified at the 1,3-position of the upper edge is obtained. The molar ratio of hexamethylenetetramine to the calix[4]-2',4'-crown ether intermediate is 30:1-100:1, preferably 30:1-50:1; the amount of trifluoroacetic acid added is 20-200 times the weight of the calix[4]-2',4'-crown ether intermediate, preferably 80-120 times. The preferred reaction temperature is 20-30℃.

[0037] Preferably, the method of further modifying the phosphine substituent on the calix[4]-2',4'-crown ether-1,3-dialdehyde in step 2) is divided into two steps: substitution step 2a) and reduction step 2b).

[0038] Preferably, in the substitution step 2a), under acidic conditions, the disubstituted phosphine compound is mixed with the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate in an organic solvent, and a certain amount of acid is added to catalyze the reaction. The resulting precipitate is then separated and used.

[0039] Preferably, in reduction step 2b), the precipitate obtained in step 2a) is further dissolved in a certain organic solvent, and a reducing agent is added in the presence of alkyl halides to carry out a reduction reaction to obtain the target product.

[0040] Preferably, in substitution step 2a), the molar ratio of the disubstituted phosphine compound to the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate is 2:1–10:1, preferably 2:1;

[0041] The acid added in step 2a) is one of sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, methanesulfonic acid, and trifluoroacetic acid, preferably p-toluenesulfonic acid, and the molar ratio of the amount added to the intermediate calix[4]-2',4'-crown ether-1,3-dialdehyde is 0.5:1–10:1, preferably 1–2:1;

[0042] The organic solvent used in step 2a) is one or more of dichloromethane, chloroform, acetonitrile, tetrahydrofuran, methyltetrahydrofuran, ethylene glycol dimethyl ether, dimethylformamide, and dimethylacetamide, preferably ethylene glycol dimethyl ether, and the amount added is 1–20 times the weight of the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate, preferably 3–5 times; the reaction temperature is 20–40°C, preferably room temperature.

[0043] Preferably, in reduction step 2b), the organic solvent is one or more of dichloromethane, chloroform, acetonitrile, tetrahydrofuran, methyltetrahydrofuran, ethylene glycol dimethyl ether, dimethylformamide, and dimethylacetamide, preferably tetrahydrofuran, and the amount added is 1–20 times the weight of the substituted product in the previous step, preferably 8–10 times.

[0044] The alkyl halide is one or more of iodomethane, iodoethane, bromoethane, bromobutane, etc., preferably iodomethane, and the molar ratio of the amount added to the substitution product in the previous step is 1:1.

[0045] The reducing agent is one or more of sodium borohydride, lithium aluminum hydride, sodium triacetoxyborohydride, diisobutylaluminum hydride, and red aluminum, preferably lithium aluminum hydride, and the amount added is 1:4–1:20, preferably 1:10–1:15, based on the molar ratio of the substitution product in the previous step; the reaction temperature is -20–40℃, preferably -5–0℃.

[0046] According to another aspect of the present invention, an object of the present invention is to provide a catalyst solution system for isomerization of branched unsaturated aliphatic nitrile linear products, said catalyst solution system comprising a complex NiL4 formed by phosphite L and zero-valent metal Ni, the bidentate phosphine ligand described in the present invention, an alkali metal salt and a solvent, wherein the molar ratio of NiL4:bidentate phosphine ligand:alkali metal salt is 1:5-40:5-40, preferably 1:5-15:5-15, more preferably 1:4-5:8-10:8-10.

[0047] According to another aspect of the present invention, another object of the present invention is to provide a method for preparing the catalyst solution system containing the bidentate phosphine ligand, the preparation method comprising: mixing a large excess of Ni powder and L phosphite in a certain organic solvent and heating for a period of time to form NiL4; subsequently adding the bidentate phosphine ligand and a certain amount of the corresponding alkali metal salt; continuing to heat to a certain temperature and react for a period of time under the protection of an inert gas and anhydrous conditions; finally, filtering out the excess Ni powder and alkali metal salt, and the resulting solution is the catalyst solution system.

[0048] The nickel powder has a particle size of 50 nm to 5.0 μm, preferably 2 to 3 μm. During the preparation of the catalyst solution system, the nickel powder can be added in excess and recycled.

[0049] Preferably, the general structural formula of the phosphite L is as follows: Wherein X, Y, and Z may be the same or different, and each is independently selected from one or more of o-phenylphenyl, p-phenylphenyl, o-methylphenyl, m-methylphenyl, p-methylphenyl, 2,6-dimethylphenyl, 2,4-dimethylphenyl, 2,4-di-tert-butylphenyl, 2,4,6-trimethylphenyl, 2,4,6-tri-tert-butylphenyl, 1-naphthyl, and 2-naphthyl.

[0050] Preferably, the choice of the alkali metal salt is related to the size of the crown ether ring. Generally, NaCl corresponds to C4, C4CH, C4PH, and C4NA structures; KCl corresponds to C5 and azaC5 structures; and cesium chloride corresponds to a C6 structure. The molar ratio of the alkali metal salt to the bidentate phosphine ligand is 1:1–1:10, preferably 1:1–1:2.

[0051] The organic solvent is toluene, xylene, 3PN, etc., preferably 3PN, and the amount used is 1-50 times the mass of the bidentate phosphine ligand, preferably 1-3 times.

[0052] According to another aspect of the invention, another object of the invention is to provide the use of the catalyst solution system in the reaction of isomerization of 2M3BN to 3PN.

[0053] According to another aspect of the present invention, another object of the present invention is to provide a method for isomerizing 2M3BN to 3PN, the method comprising: adding 2M3BN or a mixture of 2M3BN and 3PN, etc., to a reactor, adding a certain amount of the catalyst solution system, maintaining the reaction system in an anhydrous and oxygen-free state at a certain temperature, and reacting for a period of time to obtain the isomerized product 3PN.

[0054] Preferably, the 2M3BN or the mixture of 2M3BN and 3PN is a reaction solution containing about 95-98 wt% of 2M3BN raw material, and the amount of catalyst solution added is 1-50 wt% of the reaction solution, preferably 10 wt%; the reaction temperature is 60-150°C, preferably 110-120°C; and the reaction time is about 15-45 min, preferably 20-30 min.

[0055] Compared with the prior art, the bidentate phosphine ligand and the catalyst prepared therefrom of the present invention have the following advantages:

[0056] 1. The catalyst prepared by the method of the present invention has a high ability to catalyze the isomerization of 2M3BN, and the conversion rate and selectivity are significantly improved;

[0057] 2. The catalyst system in this invention has good selectivity, and the increase of 2PN and 2M2BN during the reaction is very small, which ensures high yield and easy post-processing, and can protect the catalyst from deactivation.

[0058] 3. The reaction rate is relatively fast. Compared with the current catalyst system, the reaction rate is significantly improved, laying the foundation for continuous production.

[0059] 4. This catalyst system does not require the addition of Lewis acid as an auxiliary agent, reducing costs and post-processing procedures;

[0060] 5. The catalyst prepared by the method of the present invention is stable and its catalytic performance does not decrease significantly after multiple cycles.

[0061] 6. The bidentate phosphine ligand prepared by this invention can be used in industrial production in conjunction with existing trialkylphenyl phosphite without requiring equipment modification, further reducing the cost increase brought about by technical upgrades. Detailed Implementation

[0062] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0063] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0064] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0065] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0066] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0067] Example 1: Preparation of bidentate phosphine ligands 1-3, preparation of catalysts containing bidentate phosphine ligands 1-3, and their application in the isomerization of 2M3BN.

[0068]

[0069]

[0070] Preparation of intermediate 1-1: Under nitrogen protection, a solution of calix[4] aromatics (42.5 g, 0.1 mol), diethylene glycol di-p-toluenesulfonate (55.0 g, 0.12 mol) and Na2CO3 (21.2 g, 0.20 mol) in acetonitrile (1.0 L) was refluxed for 24 h. The solution was filtered and acetonitrile was removed by vacuum distillation. 1500 mL of dichloromethane was added to the residue to dissolve it completely, followed by 800 mL of deionized water. After phase separation, the organic phase was washed with 10% dilute hydrochloric acid aqueous solution (800 mL × 2) and deionized water (800 mL × 2), dried with anhydrous magnesium sulfate, and the dichloromethane was evaporated to dryness under vacuum. The crude product was purified by silica gel column chromatography (elution buffer: petroleum ether-ethyl acetate = 4:1, v / v) to obtain intermediate 1-1 (39.1 g, yield 72.6%), a white solid. 1 H-NMR(400MHz, CDCl3), δ:7.73(2H,s),7.07(4H,d),6.85(4H,d),6.72-6.64 (4H,m),4.38(4H,d,J=13.1),4.07(8H,s),3.97(4H,t),3.28(4H,d,J=13.1);

[0071] Preparation of intermediate 1-2: Intermediate 1-1 (27 g, 50.0 mmol) and hexamethylenetetramine (280.0 g, 2.0 mol) were added to trifluoroacetic acid (1000 g). The mixture was heated to reflux and monitored by TLC until 1-1 was completely eliminated. After the reaction was complete, most of the trifluoroacetic acid was distilled off in a bent tube and reused. The residue was quenched in 1000 mL of an ice-water mixture and extracted with dichloromethane. The phases were separated, and the organic phase was washed with deionized water (500 mL × 3) and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure, and the mixture was recrystallized from ethyl acetate-methanol to give 21.9 g of white powdery solid 1-2, yield 73.8%. ESI-MS: 595 ([M+H) + ),617([M+Na] + ).

[0072] Preparation of ligands 1-3: In a round-bottom flask, diphenylphosphine (11.2 g, 60.0 mmol) was added to ethylene glycol dimethyl ether (60 mL), followed by the solution of ligands 1-2 (17.8 g, 30.0 mmol). The solution was stirred at room temperature for 10 minutes. p-Toluenesulfonic acid (11.4 g, 60.0 mmol) was added via syringe, and the mixture was stirred for 48 hours. The resulting white precipitate was separated by filtration, washed with ethylene glycol dimethyl ether (30 mL × 2), and dried under vacuum for 4 hours without further purification. This precipitate was used directly in the next step. After drying, anhydrous tetrahydrofuran (90 mL) was added and dissolved completely. The reactor was sealed, purged with nitrogen three times, and then iodomethane (3.8 mL, approximately 60 mmol) was added via syringe. The solution was stirred at room temperature for 2 hours. The mixture was then cooled to 0 °C, and solid LiAlH4 (11.4 g, 0.3 mol) was added in small portions. After addition, the system was heated to room temperature and stirred for 5-6 hours. The reaction progress was monitored by TLC. The reactor was cooled to 0°C again, and 300 mL of 10% dilute hydrochloric acid was slowly added dropwise (note the exothermic reaction). The organic layer was separated, and the aqueous layer was washed with ethyl acetate (100 mL × 3). The combined organic phases were dried overnight with anhydrous sodium sulfate, and the solvent was removed by vacuum distillation. The crude product was purified by silica gel column chromatography (eluent: petroleum ether:ethyl acetate = 7:3, v / v) to give bidentate phosphine ligand 1-3, 25.2 g, yield 90%. 1 H-NMR(400MHz, CDCl3), δ:7.75(2H,s),7.52-7.30(20H,m),7.17(2H,t),7.09(4H, d),6.76(4H,m),4.37(4H,d),4.08(8H,s),3.97(4H,t),3.28(4H,d),3.18(4H,s);

[0073] Preparation of the catalyst solution: Under anhydrous and oxygen-free conditions, 20 g of 3PN, 0.59 g (10 mmol) of nickel powder, and 3.0 g (8.5 mmol) of tri-m-tolyl phosphite were added to a round-bottom flask. The mixture was heated to 115 °C and reacted for 2–3 hours. Subsequently, 15.0 g (16.0 mmol) of the 1–3 solution prepared in the above reaction was added to the system, followed by 1.0 g (17.1 mmol) of sodium chloride. The reaction was continued overnight at 115–120 °C. After the reaction was completed, the solution was cooled to 50–60 °C, allowed to stand, and stored under warm conditions. When using, the supernatant was used. The catalyst system contained approximately 7.0 g of NiL4 per 100 g of catalyst solution and 37.5 g of bidentate phosphine ligand per 100 g of catalyst solution.

[0074] Isomerization reaction of 2M3BN: In a reactor, 100g of reaction solution (the composition of the initial reaction solution is shown in Table 1) was added, followed by 10g of the catalyst solution prepared above. The mixture was purged with nitrogen three times. Heating and stirring were then initiated, and the reaction was heated to 120℃ and allowed to proceed for 20 min. The reaction was then cooled to terminate the reaction. The actual effect of the reaction was determined by gas chromatography.

[0075] Product distribution is shown in Table 1.

[0076] Example 2: Preparation of bidentate phosphine ligands 2-3, preparation of catalysts containing bidentate phosphine ligands 2-3, and their application in the isomerization of 2M3BN.

[0077]

[0078] Preparation of ligands 2-3: The procedure was the same as that for 1-3 in Example 1, 25.3 g, yield 80.5%. 1 H-NMR(400MHz, CDCl3), δ:7.75(2H,s),7.38(2H,t),7.32–6.80(24H,m),4.3 7(4H,d),4.08(8H,s),3.97(4H,t),3.88(12H,s),3.28(4H,d),3.18(4H,s);

[0079] Preparation of catalyst solution: The operation method is the same as in Example 1, and the catalyst system contains approximately 7.0 g of NiL4 per 100 g catalyst solution.

[0080] Isomerization reaction of 2M3BN: The procedure was the same as in Example 1, and the experimental results are shown in Table 1.

[0081] Example 3: Preparation of bidentate phosphine ligand 3-3, preparation of catalysts containing bidentate phosphine ligand 3-3, and their application in the isomerization of 2M3BN.

[0082]

[0083] Preparation of intermediate 3-1: The procedure was the same as that for intermediate 1-1 in Example 1, except that the alkali was replaced with K2CO3 (27.6 g, 0.20 mol), while other parameters remained unchanged. Intermediate 2-1 (37.6 g, yield 64.5%) was obtained. 1 H-NMR(400MHz, CDCl3), δ:7.73(2H,s),7.08(4H,m),6.85(4H,d),6.73-6.6 4(4H,m),4.42(4H,d),4.02(8H,s),3.93(4H,t),3.85(4H,t),3.36(4H,d);

[0084] Preparation of intermediate 3-2: The procedure was the same as that for intermediate 1-2 in Example 1. Product yield: 24.0 g, 75.2%. ESI-MS: 639 ([M+H)). + ),661([M+Na] + ).

[0085] Preparation of ligand 3-3: The procedure was the same as that for 1-3 in Example 1. The product yielded 26.7 g, with a yield of 91%. ¹H-NMR (400 MHz, CDCl₃), δ: 7.73 (2H, s), 7.59-7.30 (20H, m), 7.15 (2H, t), 7.10 (4H, d), 6.76 (4H, m), 4.38 (4H, d), 4.08 (8H, s), 3.97 (4H, t), 3.85 (4H, t), 3.28 (4H, d), 3.18 (4H, s).

[0086] Preparation of catalyst solution: The operation method is the same as in Example 1, and the catalyst system contains approximately 7.0 g of NiL4 per 100 g catalyst solution.

[0087] Isomerization reaction of 2M3BN: The operation was the same as in Example 1, and the experimental results are shown in Table 1.

[0088] Example 4: Preparation of bidentate phosphine ligand 4-3, preparation of catalysts containing bidentate phosphine ligand 4-3, and their application in the isomerization of 2M3BN.

[0089]

[0090] Preparation of intermediate 4-1: In a flask, calix[4] aromatics (42.4 g, 0.10 mol) and acetonitrile (250 mL) were added, followed by DEAD (17.5 g, 0.20 mol) and TPP (26.3 g, 0.20 mol) at 0 °C. The mixture was stirred for 30 min under nitrogen protection, followed by the addition of 1,2-di(hydroxyethoxy)diphenyl ether (21.8 g, 0.11 mol). The reaction was stirred overnight. After the reaction was completed, the solvent was removed by vacuum distillation, deionized water (150 mL) was added, and the mixture was extracted with dichloromethane (100 mL × 3). The organic phases were combined, dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by vacuum distillation. The product was separated by silica gel chromatography (eluent: petroleum ether: ethyl acetate = 3:1, v / v). Intermediate 3-1, 41.7 g, yield 71.0%. H-NMR(400MHz, CDCl3), δ:7.73(2H,s),7.10(2H,m),7.04(2H,t),6.99-6.75(12H,m),4.40(4H,d),4.30(8H,s),3.38(4H,d);

[0091] Preparation of intermediate 4-2: The procedure was the same as that for intermediate 1-2 in Example 1, 25.7 g, 80.0%. ESI-MS: 587 ([M+H) + ),609([M+Na] + );

[0092] Preparation of ligands 4-3: The procedure was the same as that for 1-3 in Example 1, 26.5 g, yield 90%. 1 H-NMR (400MHz, CDCl3), δ: 7.73(2H,s),7.59-7.30(20H,m),7.10(2H,m),7.01-6.75(12H,m),4.42(4H,d),4.30(8H,s),3.38(4H,d), 3.26(4H,s).

[0093] Preparation of catalyst solution: The operation method is the same as in Example 1, and the catalyst system contains approximately 7.0 g of NiL4 per 100 g catalyst solution.

[0094] Example 5: Repeated application of the experiment

[0095] The catalyst solution from Example 1 was used in a cyclic experiment, with the same procedure as in Example 1. The experiment was repeated six times, and the results are summarized in Table 2.

[0096] Comparative Example 1: Preparation of bidentate phosphine ligand 5-3, preparation of catalysts containing bidentate phosphine ligand 5-3, and their application in 2M3BN isomerization.

[0097]

[0098] Preparation of intermediate 5-1: Refer to the methods in the following literature: 1) Tetrahedron, 1983, 39, 409-426; 2) J. Chem. Soc., Chem. Commun. 1992, 730-732; 3) Tetrahedron Lett. 1997, 38, 1999-2002; 4) Eur. J. Org. Chem. 2006, 21, 4951-4962.

[0099] Preparation of intermediate 5-2: It was prepared according to the method of Tetrahedron, 2008, 64, 741–748.

[0100] Preparation of bidentate phosphine ligand 5-3: The procedure was the same as that for the preparation of 1-3 in Example 1, 23.2 g, yield 91%. 1H-NMR (400MHz, CDCl3), δ: 7.73(2H,s),7.59-7.30(20H,m),7.10-7.01(6H,m),6.75(4H,s),4.42(4H,d),3.90(6H,s),3.38(4H,d), 3.26(4H,s).

[0101] Preparation of catalyst solution: The operation method is the same as in Example 1. The catalyst system contains 3.87 g of NiL4 per 100 g of catalyst solution and 17.90 g of ligand per 100 g of catalyst.

[0102] Isomerization reaction of 2M3BN: The operation was the same as in Example 1, and the experimental results are shown in Table 1.

[0103] Comparative Example 2: Preparation of a catalyst containing tris(m-tolyl) phosphite and its application in the isomerization of 2M3BN

[0104] Preparation of catalyst solution: The preparation method is the same as in Example 1, using tri-m-tolyl phosphite, which is commonly used in industry, as a ligand. The catalyst system contains approximately 7.0 g of NiL4 per 100 g of catalyst solution and approximately 40.0 g of ligand per 100 g of catalyst solution.

[0105] Isomerization reaction of 2M3BN: After adding the reaction solution and catalyst solution, 0.5 g of zinc chloride was added as a Lewis acid using current industrial technology. The reaction time was 120–150 min. Other procedures were the same as in Example 1, and the experimental results are shown in Table 1.

[0106] Table 1

[0107]

[0108] Table 2

[0109] project 2M3BN conversion rate (%) 3PN selectivity (%) Loop 1 ＞99 98.8 Loop 2 ＞99 98.1 Cycle 3 ＞99 98.7 Cycle 4 ＞99 97.9 Cycle 5 ＞99 98.8 Cycle 6 ＞99 98.0

[0110] As can be seen from Table 1, the above examples and comparative examples demonstrate that the bidentate phosphine ligand prepared by the present invention, and the catalyst system containing the bidentate phosphine ligand, have high selectivity and conversion rate. In addition, compared with comparative examples 1 and 2, it is fully demonstrated that the introduction of calixarene and crown ether significantly improves the efficiency and selectivity of the catalyst. Compared with the method in comparative example 2, the catalyst system used in the present invention does not contain Lewis acid, achieving better application results. It is worth noting that the introduction of bidentate phosphine ligand with calix[4]arene group has a significant effect on reducing reaction time because it does not require the addition of Lewis acid.

[0111] As can be seen from Table 2, the catalyst of the present invention has a good recycling effect, and the activity of the catalyst does not change significantly after being reused six times.

[0112] In summary, compared with traditional research approaches that utilize the cyclic framework structure and cavities of calixarenes or the phase transfer catalytic effect of crown ethers, the catalyst solution provided by this invention innovatively proposes a structural synergistic effect between calixarenes and crown ethers, which together achieve the goal of improving conversion rate and selectivity.

[0113] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A bidentate phosphine ligand, said bidentate phosphine ligand being a compound containing calix[4]arene, the structure of which is shown in general formula 1 below, wherein the calix[4]arene is used as the backbone, a phosphorus-containing substituent is present at the 1,3-position of the upper edge of the calix[4]arene, and a crown ether structure is present at the 2',4'-position of the lower edge of the calix[4]arene: General Formula 1 in, The 1,3-position substitution The phosphorus-containing substituent moiety, wherein X1 and X2 are each independently selected from substituted or unsubstituted C6-C14 aryl, C6-C14 aryl C1-C6 alkyl, C6-C14 aryl C1-C6 alkoxy, and C1-C10 alkyl, wherein "substituted" in the substituted C6-C14 aryl means that the C6-C14 aryl contains one or two substituents each independently selected from C1-C6 alkyl and C1-C6 alkoxy; The 2',4'-bit The crown ether structure part is selected from one of crown ethers, azacrown ethers, and aromatic cyclic crown ethers.

2. The bidentate phosphine ligand according to claim 1, characterized in that, The crown ether structure is selected from one of the following structures, wherein It is a simplified formula of calix[4] aromatics and phosphorus-containing substituents; 。 3. The bidentate phosphine ligand according to claim 1, characterized in that, X1 and X2 are each independently selected from one or two of the following: phenyl, ortho-C1-C6 alkylphenyl, meta-C1-C6 alkylphenyl, p-C1-C6 alkylphenyl, ortho-C1-C6 alkoxyphenyl, meta-C1-C6 alkoxyphenyl, p-C1-C6 alkoxyphenyl, 1-naphthyl, 2-naphthyl, tert-butyl, 2,4-dimethylphenyl, 2,4-di-tert-butylphenyl, and 2,4-dimethoxyphenyl.

4. The bidentate phosphine ligand according to claim 1, characterized in that, X1 and X2 are each independently selected from phenyl, o-methylphenyl, m-methylphenyl, p-methylphenyl, o-methoxyphenyl, m-methoxyphenyl, p-methoxyphenyl, o-ethoxyphenyl, m-ethoxyphenyl, p-ethoxyphenyl, o-propoxyphenyl, m-propoxyphenyl, and p-propoxyphenyl.

5. The method for preparing bidentate phosphine ligands according to any one of claims 1 to 4, the method comprising the following steps: 1) The precursor of the polyether structure, calix[4] aromatic hydrocarbon and solvent were added to the reactor to react and obtain calix[4]-2',4'-crown ether intermediate; 2) The calix[4]-2',4'-crown ether intermediate was mixed with a certain amount of hexamethylenetetramine and reacted with trifluoroacetic acid to obtain calix[4]-2',4'-crown ether-1,3-dialdehyde with two aldehyde groups modified at the 1,3-position of the upper edge, i.e., the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate. The molar ratio of hexamethylenetetramine to calix[4]-2',4'-crown ether intermediate was 30:1 to 100:1; the amount of trifluoroacetic acid added was 20 to 200 times the weight of the calix[4]-2',4'-crown ether intermediate; and the reaction temperature was 20 to 30 °C. 3) Under acidic conditions, the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate obtained in step 2) and the phosphine-containing substituent moiety The precursor reaction was followed by the final bidentate phosphine ligand product in the presence of a haloalkane and a reducing agent. In step 1), the following method is followed: using an inorganic base as an acid-binding agent and a template agent, the calix[4]-2',4'-crown ether intermediate is obtained by reacting the p-toluenesulfonate of polyether diol with calix[4] aromatics; Alternatively, step 1) can be carried out as follows: using a bimolecular nucleophilic substitution reaction, a mixture of calix[4] aromatic hydrocarbons and polyether diols is directly cyclized under the action of organophosphorus compounds and dialkyl azodicarbonate to obtain the product; The polyether diol is selected from triethylene glycol, tetraethylene glycol, pentaethylene glycol, 1,2-di(hydroxyethoxy)diphenyl ether, 1,3-di(hydroxyethoxy)diphenyl ether, and 3,9-dioxa-6-aza-1,11-undecanediol.

6. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, The p-toluenesulfonate of the polyether diol is selected from the p-toluenesulfonates of the following substances: triethylene glycol, tetraethylene glycol, pentaethylene glycol, 1,2-di(hydroxyethoxy)diphenyl ether, 1,3-di(hydroxyethoxy)diphenyl ether, and 3,9-dioxa-6-aza-1,11-undecanediol.

7. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the inorganic base is one or more of sodium carbonate, potassium carbonate, cesium carbonate, and sodium hydride; wherein, when the crown ether structure is C4, C4PH, or C4NA, sodium carbonate is used as the base; when the crown ether structure is C5 or azaC5, potassium carbonate is used as the base; and when the crown ether structure is C6, cesium carbonate is used as the base.

8. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of inorganic base to calix[4] aromatic hydrocarbon is 3:1 to 5:

1.

9. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of inorganic base to calix[4] aromatic hydrocarbon is 3:

1.

10. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of cup[4] aromatic hydrocarbon to p-toluenesulfonate of polyether diol is 1:1~5.

11. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of cup[4] aromatic hydrocarbon to p-toluenesulfonate of polyether diol is 1:1.1 ~ 1.

5.

12. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the solvent is selected from acetonitrile, acetone, tetrahydrofuran, and methyltetrahydrofuran, and the amount of solvent added is 5 to 50 times the mass of calix[4] aromatic hydrocarbon.

13. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the solvent is acetonitrile, and the amount of solvent added is 20-30 times the mass of calix[4] aromatic hydrocarbon.

14. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1) of method one, the reaction time is 6–36 h.

15. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1) of method one, the reaction time is 18-24 h.

16. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of the aromatic hydrocarbon to the polyether diol in method 2 is 1:1~5.

17. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of the cup[4] aromatic hydrocarbon to the polyether diol in method 2 is 1:1.05~1.

20.

18. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of the cup[4] aromatic hydrocarbon to the polyether diol in method 2 is 1:1~1.

2.

19. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the molar ratio of the organophosphorus compound, the dialkyl azodicarbonate ester, and the calix[4] aromatic hydrocarbon in method 2 is 2:2:

1.

20. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the solvent described in method 2 is tetrahydrofuran, methyltetrahydrofuran or acetonitrile, and the amount added is 1-100 times the mass of calix[4] aromatic hydrocarbon; the reaction temperature is 0-40 ℃.

21. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the amount of solvent added in method 2 is 3-10 times the mass of the calix[4] aromatic hydrocarbon; the reaction temperature is room temperature.

22. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, The organophosphorus compounds mentioned in Method 2 of Step 1) are triphenylphosphine and tributylphosphine.

23. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, The organophosphorus compound mentioned in Method 2 of Step 1) is triphenylphosphine.

24. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the solvent in method 2 is selected from acetonitrile, acetone, tetrahydrofuran, and methyltetrahydrofuran, and the amount of solvent added is 3 to 10 times the mass of calix[4] aromatic hydrocarbon.

25. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 1), the solvent in method 2 is acetonitrile, and the amount of solvent added is 4-5 times the mass of calix[4] aromatic hydrocarbon.

26. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In Method 2 of Step 1), the reaction time is 6–36 h.

27. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In Method 2 of Step 1), the reaction time is 6-12 h.

28. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, The phosphorus-containing substituent precursor in step 3) has an HPX1X2 structure, where X1 and X2 are defined in the same way as in general formula 1.

29. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, In step 2), the molar ratio of hexamethylenetetramine to calix[4]-2',4'-crown ether intermediate is 30:1 to 50:1; the amount of trifluoroacetic acid added is 80 to 120 times the weight of calix[4]-2',4'-crown ether intermediate.

30. The method for preparing bidentate phosphine ligands according to claim 5, characterized in that, Step 3) involves further modifying the phosphine substituent on calix[4]-2',4'-crown ether-1,3-dialdehyde in two steps: substitution step 2a) and reduction step 2b). In step 2a), the phosphine-containing substituent portion is subjected to acidic conditions. The precursor and the intermediate of calix[4]-2',4'-crown ether-1,3-dialdehyde were mixed in an organic solvent, and a certain amount of acid was added to catalyze the reaction. The resulting precipitate was separated and used. In reduction step 2b), the precipitate obtained in step 2a) is further dissolved in a certain organic solvent, and a reducing agent is added in the presence of alkyl halides to carry out a reduction reaction to obtain the target product.

31. The method for preparing bidentate phosphine ligands according to claim 30, characterized in that, In the substitution step 2a), the phosphine-containing substituent moiety The molar ratio of the precursor to the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate is 2:1 – 10:1; The acid added in step 2a) is one of sulfuric acid, hydrochloric acid, phosphoric acid, p-toluenesulfonic acid, methanesulfonic acid, or trifluoroacetic acid, and the molar ratio of the amount added to the intermediate calix[4]-2',4'-crown ether-1,3-dialdehyde is 0.5:1 – 10:1; The organic solvent used in step 2a) is one or more of dichloromethane, chloroform, acetonitrile, tetrahydrofuran, methyltetrahydrofuran, ethylene glycol dimethyl ether, dimethylformamide, and dimethylacetamide, and the amount added is 1-20 times the weight of the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate; the reaction temperature is 20-40 ℃.

32. The method for preparing bidentate phosphine ligands according to claim 30, characterized in that, In substitution step 2a), the molar ratio of the disubstituted phosphine compound to the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate is 2:1; The acid added in step 2a) is replaced by p-toluenesulfonic acid, and the molar ratio of the amount added to the intermediate calix[4]-2',4'-crown ether-1,3-dialdehyde is 1 – 2 : 1; The organic solvent used in step 2a) was replaced with ethylene glycol dimethyl ether, and the amount added was 3-5 times the weight of the calix[4]-2',4'-crown ether-1,3-dialdehyde intermediate; the reaction temperature was room temperature.

33. The method for preparing bidentate phosphine ligands according to claim 30, characterized in that, In reduction step 2b), the organic solvent is one or more of dichloromethane, chloroform, acetonitrile, tetrahydrofuran, methyltetrahydrofuran, ethylene glycol dimethyl ether, dimethylformamide, and dimethylacetamide, and the amount added is 1 to 20 times the weight of the substituted product in the previous step. The alkyl halide is one or more of iodomethane, iodomethane, bromoethane, and bromobutane, and the molar ratio of the amount added to the substitution product in the previous step is 1:

1. The reducing agent is one or more of sodium borohydride, lithium aluminum hydride, sodium triacetoxyborohydride, diisobutylaluminum hydride, and red aluminum, and the amount added is 1:4 – 1:20 of the molar ratio of the substitution product in the previous step; the reaction temperature is -20 to 40 ℃.

34. The method for preparing bidentate phosphine ligands according to claim 30, characterized in that, In reduction step 2b), the organic solvent is tetrahydrofuran, and the amount added is 8-10 times the weight of the substituted product from the previous step; The alkyl halide is iodomethane; The reducing agent is lithium aluminum hydride, and the amount added is 1:10 – 1:15 of the molar ratio of the substitution product in the previous step; the reaction temperature is -5 to 0 ℃.

35. A catalyst solution system for isomerization of branched unsaturated aliphatic nitrile into linear products, said catalyst solution system comprising a complex NiL4 formed from phosphite L and zero-valent metal Ni, a bidentate phosphine ligand according to any one of claims 1 to 4, an alkali metal salt, and a solvent, wherein, The molar ratio of NiL4: bidentate phosphine ligand: alkali metal salt is 1:5-40:5-40.

36. The catalyst solution system according to claim 35, characterized in that, The molar ratio of NiL4: bidentate phosphine ligand: alkali metal salt is 1: 5-15: 5-15.

37. The catalyst solution system according to claim 35, characterized in that, The molar ratio of NiL4: bidentate phosphine ligand: alkali metal salt is 1: 4-5: 8-10.

38. The method for preparing the catalyst solution system according to claim 35, wherein the preparation method comprises: In a certain organic solvent, excess Ni powder and L phosphite are mixed and heated for a period of time to form NiL4. Then, the bidentate phosphine ligand and a certain amount of the corresponding alkali metal salt are added. Under the protection of inert gas and anhydrous conditions, the mixture is heated to a certain temperature and reacted for a period of time. Finally, the excess Ni powder and alkali metal salt are filtered off, and the resulting solution is the catalyst solution system.

39. The preparation method according to claim 38, characterized in that, The nickel powder has a particle size of 50 nm - 5.0 μm; during the preparation process, excess nickel powder is added and recycled. The general structural formula of the phosphite L is: X, Y, and Z may be the same or different, and each is independently selected from one or more of o-phenylphenyl, p-phenylphenyl, o-methylphenyl, m-methylphenyl, p-methylphenyl, 2,6-dimethylphenyl, 2,4-dimethylphenyl, 2,4-di-tert-butylphenyl, 2,4,6-trimethylphenyl, 2,4,6-tri-tert-butylphenyl, 1-naphthyl, and 2-naphthyl. The choice of alkali metal salt is related to the size of the crown ether ring. NaCl corresponds to C4, C4PH, and C4NA structures; KCl corresponds to C5 and azaC5 structures; and cesium chloride corresponds to C6 structure. The molar ratio of the alkali metal salt to the bidentate phosphine ligand is 1:1 – 1:

10. The organic solvent is toluene, xylene, or 3-pentenonitrile, and the amount used is 1-50 times the mass of the bidentate phosphine ligand.

40. The preparation method according to claim 38, characterized in that, The nickel powder has a particle size of 2-3 μm; The molar ratio of the alkali metal salt to the bidentate phosphine ligand is 1:1 – 1:2; The organic solvent is 3-pentenonitrile, and the amount used is 1 to 3 times the mass of the bidentate phosphine ligand.

41. Use of the catalyst solution system according to claim 35 in the reaction of isomerization of 2-methyl-3-butene to 3-pentenonitrile.

42. A method for isomerizing 2-methyl-3-butene to 3-pentenonitrile, the method comprising: In a reactor, 2-methyl-3-butene or a mixture of 2-methyl-3-butene and 3-pentenonitrile is added, along with a certain amount of the catalyst solution system according to claim 37. The reaction system is kept in an anhydrous and oxygen-free state at a certain temperature and reacted for a period of time to obtain the isomerized product 3-pentenonitrile. The 2-methyl-3-butene or the mixture of 2-methyl-3-butene and 3-pentenonitrile is a reaction solution containing 95-98 wt% of 2-methyl-3-butene raw material; the amount of catalyst solution added is 1-50 wt% of the reaction solution; the reaction temperature is 60-150 ℃; and the reaction time is 15-45 min.

43. The preparation method according to claim 42, characterized in that, The catalyst solution system is added at a rate of 10 wt% of the reaction solution; the reaction temperature is 110–120 °C; and the reaction time is 20–30 min.

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