Organic iron-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses an organic iron-based catalyst as well as a preparation method and application thereof, the structure of the catalyst is as shown in formula (I), and A is tert-butyl or isopropyl. The preparation method of the catalyst comprises the following steps: dissolving a phenyl-substituted pyridine compound and alkyl phosphorus chloride in an organic solvent in an inert atmosphere, and reacting under the action of the catalyst; and adding an organic solution containing Fe < 2 + > into the obtained product, carrying out a reaction, adding a silicon-based lithium compound into the obtained product, adding a precipitant, and carrying out a crystallization reaction to obtain the organic iron-based catalyst. The organic iron-based catalyst disclosed by the invention is high in catalytic activity and good in stability, the ring-opening metathesis polymerization reaction of cyclic olefin can be completed at a relatively low temperature, the reaction process is simple, the conversion rate of raw materials and the yield of a target product are relatively high, and the reaction process is green, environment-friendly and pollution-free. The catalyst is simple in preparation process, raw materials are easy to obtain, and the production cost can be greatly reduced. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis and relates to an olefin polymerization catalyst, in particular to an organic iron catalyst and a preparation method and application thereof. Background Art

[0002] The research on olefin metathesis has developed rapidly due to the great value of its synthetic products in the fields of medicine, pesticides and materials. Ring-opening metathesis polymerization is an important type of olefin metathesis reaction. It has received more and more attention due to its characteristics of active polymerization. Polydicyclopentadiene (PDCPD) is a typical polymer obtained by ring-opening metathesis polymerization. It is a homopolymer or copolymer formed by dicyclopentadiene (DCPD) through a catalyst to promote the connection of olefin monomers. It is a cross-linked three-dimensional network structure engineering plastic with both rigidity and toughness. It has excellent heat resistance, creep resistance, dimensional stability, shape memory, corrosion resistance, light weight and other characteristics. It can be used in many engineering fields, such as transportation, electrical equipment, sports equipment, agricultural machinery, civil engineering, etc.

[0003] Ring-opening metathesis polymerization catalytic system based on metal organic catalyst is an important method to realize ring-opening metathesis polymerization of various cyclic olefin monomers. Grubbs catalyst is currently the most widely used catalyst in ring-opening metathesis polymerization. It can ensure high initiation efficiency, thus providing a basis for active polymerization, but its catalytic efficiency is still low and the cost is high, which limits its industrial application prospects.

[0004] Patent document with publication number CN114656315A discloses a method for preparing a PDCPD raw material containing cyclopentadiene trimer. This method uses DCPD as a raw material and reacts with 0.006%wt Hoveyda-Grubbs catalyst through segmented injection, preheating, and precise temperature control to synthesize PDCPD.

[0005] The patent document with publication number CN117343286A discloses a carbon nanotube / PDCPD composite material and a preparation method thereof, the preparation method comprising the following steps: adding modified carbon nanotubes to DCPD (dicyclopentadiene), ultrasonically dispersing for 2 hours, and dispersing uniformly; dissolving the Grubbs catalyst in a small amount of dichloromethane in a beaker, adding the mixed solution of carbon nanotubes and DCPD after ultrasonic dispersion, stirring at 30°C for 30 seconds, and then quickly pouring into a mold, curing at 110°C, to obtain a carbon nanotube / PDCPD composite material. This method reacts the modified carbon nanotubes with DCPD under the action of phenylmethylenebis(tricyclohexylphosphine)ruthenium dichloride (Grubbs first generation catalyst) to synthesize PDCPD material.

[0006] Patent document with announcement number CN107987107B discloses a method for synthesizing a novel nitrogen heterocyclic carbene ligand and a ruthenium metal carbene catalyst synthesized by using the ligand. The ruthenium metal carbene catalyst is synthesized by a metathesis exchange reaction after a carbene ligand containing a terminal olefin replaces a ligand on a Grubbs first-generation catalyst. The catalyst can be used to catalyze the ring-opening metathesis polymerization of norbornene to prepare polynorbornene products.

[0007] However, the catalysts used in the above existing methods have the disadvantages of high cost, poor reaction activity, and potential environmental hazards, and the yield of the obtained target product is low and cannot meet the requirements of industrial production. Summary of the invention

[0008] To address the deficiencies of the prior art, the present invention provides an organic iron-based catalyst and a preparation method and application thereof. The organic iron-based catalyst can trigger a ring-opening metathesis polymerization reaction, has high catalytic activity and high stability, is particularly suitable for the polymerization of cyclic olefins, and can meet the requirements of industrial production.

[0009] The first aspect of the present invention provides an organic iron catalyst, the molecular structure of which is shown below:

[0010]

[0011] Wherein, A is tert-butyl or isopropyl.

[0012] The second aspect of the present invention provides a method for preparing the organic iron-based catalyst, comprising the following steps:

[0013] (1) Under an inert atmosphere, a phenyl-substituted pyridine compound and an alkylphosphonium chloride are dissolved in an organic solvent and reacted in the presence of a catalyst;

[0014] (2) Under an inert atmosphere, add Fe-containing 2+ An organic solution is reacted;

[0015] (3) After adding the silicon-based lithium compound to the product obtained in step (2), a precipitant is added to carry out a crystallization reaction, and after the reaction is completed, the obtained product is washed and dried to obtain the organic iron-based catalyst.

[0016] The phenyl-substituted pyridine compound undergoes a condensation reaction with alkylphosphonium chloride to generate a cyclic dendritic ligand; the cyclic dendritic ligand then reacts with Fe 2+ , silicon-based lithium compounds undergo complexation reaction, Fe 2+ The ions provide empty orbitals, and the atoms in the cyclic dendritic ligands provide lone pairs of electrons to form coordination bonds, thereby generating the organic iron-based catalyst.

[0017] The organic iron catalyst of the present invention is synthesized from a cyclic dendritic ligand. In the structure of the cyclic dendritic ligand, the benzene ring is usually in a planar configuration and has rigidity, which will lead to difficulty in rotation within the molecular chain and increase the steric hindrance. During the polymerization reaction, the obtained catalyst can cover the active center to a certain extent without affecting the insertion of the chain reactant due to the large steric hindrance of the cyclic dendritic ligand, thereby avoiding the deactivation of the double centers between the catalysts, ensuring the stability and activity of the catalyst, and improving the catalytic effect.

[0018] Preferably, the phenyl-substituted pyridine compound is 2,6-diisopropylphenylpyridine, 2,6-dimethylphenylpyridine, 2-(2,6-di-tert-butylphenyl)-6-methylpyridine or 2-(2,6-diisopropylphenyl)-6-methylpyridine. 2-(2,6-di-tert-butylphenyl)-6-methylpyridine or 2-(2,6-diisopropylphenyl)-6-methylpyridine is preferred because the above two phenyl-substituted pyridine compounds have electron-donating groups, which help to improve the activity of the catalytic center.

[0019] Preferably, in step (1), the alkyl phosphonium chloride includes di-tert-butyl phosphonium chloride, diethyl phosphonium chloride or dicyclohexyl phosphonium chloride, etc. Since di-tert-butyl phosphonium chloride has moderate steric hindrance and reaction activity, di-tert-butyl phosphonium chloride is preferably used.

[0020] Preferably, in step (1), the molar ratio of the phenyl-substituted pyridine compound to the alkyl phosphonium chloride is 1:1 to 1.2. The present invention controls the ratio of the phenyl-substituted pyridine compound to the alkyl phosphonium chloride within this range, which can ensure that the phenyl-substituted pyridine compound is completely reacted without affecting the subsequent reaction activity.

[0021] Preferably, in step (1), the organic solvent includes anhydrous ethanol, toluene, methanol, tetrahydrofuran, etc. More preferably, it is anhydrous ethanol.

[0022] Preferably, in step (1), the catalyst is an organic weak acid such as formic acid, acetic acid or glacial acetic acid. Glacial acetic acid is preferably used.

[0023] Preferably, in step (1), the reaction temperature is 50-90° C., and the reaction time is 12-20 h.

[0024] Preferably, before step (2), the product obtained in step (1) is recrystallized and purified, and the solid product obtained after recrystallization is dissolved in an organic solvent such as tetrahydrofuran before the reaction in step (2) is carried out.

[0025] Preferably, in step (2), the Fe-containing 2+In the organic solution, the solute is FeCl2·6H2O, FeCl2·4H2O, FeCl2, FeSO4 or FeSO4·H2O, etc., and the organic solvent is tetrahydrofuran, ethanol or methanol, etc. Further preferably, the Fe-containing 2+ In the organic solution, the solute is FeCl2·6H2O and the solvent is ethanol.

[0026] Preferably, in step (2), Fe 2+ The molar ratio of Fe to the phenyl-substituted pyridine compound is 1:0.8-1.5. 2+ The molar ratio of the amount of the phenyl-substituted pyridine compound is 1:0.8-1.1. This ratio range can make the pyridine compound and Fe 2+ The reaction was complete to generate the desired product.

[0027] Preferably, in step (2), the reaction time is 50-90° C. and the reaction time is 4-6 h.

[0028] Preferably, in step (3), the silicon-based lithium compound is trimethylsilylmethyllithium, trimethylsilylpropyllithium or bis(trimethylsilyl)amide lithium. Since the methyl group in trimethylsilylmethyllithium has moderate steric hindrance and suitable reaction activity, trimethylsilylmethyllithium is preferably used in the present invention.

[0029] Preferably, in step (3), the amount of the silicon-based lithium compound is about the same as Fe 2+ The molar ratio of the dosage is 1:0.8~1. Within this ratio range, the silicon-based lithium compound and Fe 2+ Forming coordination bonds protects the effective active center.

[0030] Preferably, in step (3), the precipitant includes diethyl ether, xylene or n-hexane.

[0031] Preferably, in step (3), the temperature of the crystallization reaction is -18 to 20°C and the time is 1 to 10 hours. Under these conditions, the crystallization reaction can be ensured to be complete.

[0032] The present invention also provides the use of the organic iron catalyst in catalyzing the ring-opening metathesis polymerization of cyclic olefins. The organic iron catalyst of the present invention has the advantages of high catalytic activity and good stability, a high yield of the target product in catalyzing the ring-opening metathesis polymerization of cyclic olefins, and a simple polymerization process.

[0033] Preferably, the application method is: adding the cyclic olefin into a reaction container, and dripping the solution of the organic iron-based catalyst into the reaction container under stirring conditions to carry out a curing reaction.

[0034] Preferably, the cyclic olefin includes DCPD, norbornene, cyclohexene, cyclooctene or cyclooctadiene.

[0035] Preferably, in the solution of the organic iron-based catalyst, the solvent is an aromatic hydrocarbon or halogenated hydrocarbon solvent such as ethanol, toluene, xylene, trimethylbenzene, chlorobenzene, trichlorobenzene, tetralin, dioxane, tetrahydrofuran, diphenyl ether, dichloromethane, dichloroethane, etc., preferably toluene.

[0036] Preferably, the concentration of the organic iron catalyst solution is 1 to 100 mol·mL -1 More preferably, the concentration of the organic iron catalyst solution is 10 to 20 mol·mL -1 .

[0037] Preferably, the molar ratio of the organic iron catalyst to the cyclic olefin is 1:1000 to 100000. More preferably, the molar ratio of the organic iron catalyst to the cyclic olefin is 1:10000 to 40000.

[0038] Preferably, the curing reaction temperature is 10-50° C., and the reaction time is 1-3 hours.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] (1) The present invention uses a phenyl-substituted pyridine compound to undergo a condensation reaction with an alkylphosphonium chloride to generate a cyclic dendritic ligand; the cyclic dendritic ligand is then reacted with Fe 2+ , silicon-based lithium compounds undergo complexation reaction to form coordination bonds, thereby preparing the organic iron catalyst. In the structure of the cyclic dendritic ligand, the benzene ring is usually in a planar configuration, rigid, and has large steric hindrance, so that during the polymerization reaction, the catalyst can both cover the active center to a certain extent and not affect the insertion of the chain reactant, thereby avoiding the deactivation of the dual centers between the catalysts, ensuring the stability and activity of the catalyst, and improving the catalytic effect.

[0041] (2) The organic iron-based catalyst of the present invention has high catalytic activity and good stability, and the preparation process is simple. The raw materials are easy to obtain and low in price, which can significantly reduce the production cost.

[0042] (3) The organic iron-based catalyst of the present invention can complete the ring-opening metathesis polymerization reaction of cyclic olefins at a relatively low temperature. The reaction process is simple, the conversion rate of the raw materials and the yield of the target product are relatively high, and the reaction process is green, environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the infrared image of the organic iron-based catalyst prepared in Example 1.

[0044] Figure 2 This is the infrared image of the PDCPD prepared in Application Example 1.

[0045] Figure 3 This is the infrared image of the PDCPD prepared in Application Example 4.

[0046] Figure 4 This is a graph of the tensile strength of PDCPD prepared in Application Examples 1-4.

[0047] Figure 5 This is a graph of the tensile elongation at break of the PDCPD prepared in Application Examples 1-4. DETAILED DESCRIPTION

[0048] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0049] It should also be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0050] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0051] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0052] Preparation of organic iron catalysts

[0053] [Example 1]

[0054] A. Under nitrogen conditions, add 0.01 mol of 2-(2,6-di-tert-butylphenyl)-6-methylpyridine, 0.01 mol of di-tert-butylphosphine chloride and 50 mL of anhydrous ethanol into a 100 mL flask, add 5 to 10 drops of glacial acetic acid as a catalyst, stir at 60°C and 500 r / min for 15 hours to allow it to react fully, discharge part of the liquid and add 30 mL of anhydrous ethanol for recrystallization and purification.

[0055] B. Dissolve the solid product obtained by recrystallization in step A in 40 mL of tetrahydrofuran, slowly dropwise add 1 mL of 0.01 mol / mL FeCl2·6H2O ethanol solution, and react at 60°C for 5 h.

[0056] C. Add 0.01 mol of trimethylsilylmethyllithium to the mixture obtained in step B, add diethyl ether until no solid is precipitated in the mixture, and let stand for 30 min.

[0057] D. Filter the above system with a sand core funnel to obtain a filter cake, wash the filter cake with anhydrous ethanol three times, and vacuum dry it at 80°C for 10 hours to obtain a light yellow powder organic iron-based catalyst.

[0058] Figure 1 The infrared spectrum of the organic iron catalyst prepared in Example 1 is 810-680cm -1 and 1667~1430cm -1 The absorption peaks between 1250 and 1140 cm -1 and 2950cm -1 The absorption peak at 1365cm is the absorption peak of saturated alkane in the substituent; -1 、1643cm -1 and 3059cm -1 The absorption peak nearby is the vibration absorption peak of the pyridine ring, which proves that the catalyst of the target structure has been successfully synthesized.

[0059] [Example 2]

[0060] A. Under nitrogen conditions, add 0.01 mol of 2-(2,6-di-tert-butylphenyl)-6-methylpyridine, 0.01 mol of di-tert-butylphosphine chloride and 50 mL of anhydrous ethanol into a 100 mL flask, add 5 to 10 drops of acetic acid as a catalyst, stir at 70°C and 500 r / min for 15 hours to allow it to react fully, discharge part of the liquid and add 30 mL of anhydrous ethanol for recrystallization and purification.

[0061] B. Dissolve the solid product obtained by recrystallization in step A in 40 mL of tetrahydrofuran, slowly add 1 mL of 0.01 mol / mL FeCl2·6H2O ethanol solution, and react at 70°C for 5 h.

[0062] C. Add 0.01 mol of trimethylsilylmethyllithium to the mixture obtained in step B, and then add diethyl ether with a dropper, which will cause a precipitate to form. Continue to add diethyl ether until no solid is precipitated in the mixture, and let it stand for 30 minutes.

[0063] D. Filter the above system with a sand core funnel to obtain a filter cake, wash the filter cake with anhydrous ethanol three times, and vacuum dry it at 80°C for 10 hours to obtain a yellow powder iron-based catalyst.

[0064] [Example 3]

[0065] A. Under nitrogen conditions, add 0.01 mol of 2-(2,6-di-tert-butylphenyl)-6-methylpyridine, 0.01 mol of di-tert-butylphosphine chloride and 50 mL of anhydrous ethanol into a 100 mL flask, add 5 to 10 drops of acetic acid as a catalyst, stir at 80°C and 500 r / min for 15 hours to allow it to react fully, discharge part of the liquid and add 30 mL of anhydrous ethanol for recrystallization and purification.

[0066] B. Dissolve the solid product obtained by recrystallization in step A in 40 mL of tetrahydrofuran, slowly add 1 mL of 0.01 mol / mL FeCl2·6H2O ethanol solution, and react at 80°C for 5 h.

[0067] C. Add 0.01 mol of trimethylsilylmethyllithium to the mixture obtained in step B, and then add diethyl ether with a dropper, which will cause a precipitate to form. Continue to add diethyl ether until no solid is precipitated in the mixture, and let it stand for 30 minutes.

[0068] D. Filter the above system with a sand core funnel to obtain a filter cake, wash the filter cake with anhydrous ethanol three times, and vacuum dry it at 80°C for 10 hours to obtain a yellow powder iron-based catalyst.

[0069] [Example 4]

[0070] A. Under nitrogen conditions, add 0.01 mol of 2-(2,6-diisopropylphenyl)-6-methylpyridine, 0.01 mol of di-tert-butylphosphine chloride and 50 mL of anhydrous ethanol into a 100 mL flask, add 5 to 10 drops of acetic acid as a catalyst, stir at 60°C and 500 r / min for 15 hours to allow it to react fully, discharge part of the liquid and add 30 mL of anhydrous ethanol for recrystallization and purification.

[0071] B. Dissolve the solid product obtained by recrystallization in step A in 40 mL of tetrahydrofuran, slowly add 1 mL of 0.01 mol / mL FeCl2·6H2O ethanol solution, and react at 60°C for 5 h.

[0072] C. Add 0.01 mol of trimethylsilylmethyllithium to the mixture obtained in step B, and then add diethyl ether with a dropper to precipitate. Continue to add diethyl ether until no solid precipitates in the mixture, and let it stand for 30 minutes;

[0073] D. Filter the above system with a sand core funnel to obtain a filter cake, wash the filter cake with anhydrous ethanol three times, and vacuum dry it at 80°C for 10 hours to obtain a yellow powder iron-based catalyst.

[0074] [Example 5]

[0075] A. Under nitrogen conditions, add 0.01 mol of 2-(2,6-diisopropylphenyl)-6-methylpyridine, 0.01 mol of di-tert-butylphosphine chloride and 50 mL of anhydrous ethanol into a 100 mL flask, add 5 to 10 drops of acetic acid as a catalyst, stir at 70°C and 500 r / min for 15 hours to allow it to react fully, discharge part of the liquid and add 30 mL of anhydrous ethanol for recrystallization and purification.

[0076] B. Dissolve the solid product obtained by recrystallization in step A in 40 mL of tetrahydrofuran, slowly add 1 mL of 0.01 mol / mL FeCl2·6H2O ethanol solution, and react at 70°C for 5 h.

[0077] C. Add 0.01 mol of trimethylsilylmethyllithium to the mixture obtained in step B, and then add diethyl ether with a dropper, which will cause a precipitate to form. Continue to add diethyl ether until no solid is precipitated in the mixture, and let it stand for 30 minutes.

[0078] D. Filter the above system with a sand core funnel to obtain a filter cake, wash the filter cake with anhydrous ethanol three times, and vacuum dry it at 80°C for 10 hours to obtain a yellow powder iron-based catalyst.

[0079] [Example 6]

[0080] A. Under nitrogen conditions, add 0.01 mol of 2-(2,6-diisopropylphenyl)-6-methylpyridine, 0.01 mol of di-tert-butylphosphine chloride and 50 mL of anhydrous ethanol into a 100 mL flask, add 5 to 10 drops of acetic acid as a catalyst, stir at 80°C and 500 r / min for 15 hours to allow it to react fully, discharge part of the liquid and add 30 mL of anhydrous ethanol for recrystallization and purification.

[0081] B. Dissolve the solid product obtained by recrystallization in step A in 40 mL of tetrahydrofuran, slowly add 1 mL of 0.01 mol / mL FeCl2·6H2O ethanol solution, and react at 80°C for 5 h.

[0082] C. Add 0.01 mol of trimethylsilylmethyllithium to the mixture obtained in step B, and then add diethyl ether with a dropper to precipitate. Continue to add diethyl ether until no solid precipitates in the mixture, and let it stand for 30 minutes;

[0083] D. Filter the above system with a sand core funnel to obtain a filter cake, wash the filter cake with anhydrous ethanol three times, and vacuum dry it at 80°C for 10 hours to obtain a yellow powder iron-based catalyst.

[0084] The composite iron-based metal catalyst was prepared by the methods described in Examples 1 to 6, and its output and yield are shown in Table 1.

[0085] Table 1 Output and yield of the organic iron catalysts prepared in Examples 1-6

[0086] Example 1 2 3 4 5 6 Yield 4.0609g 4.3864g 3.8182g 3.9296g 4.2188g 3.7354g Yield 79.47％ 85.84％ 74.72％ 76.90％ 82.56％ 73.10％

[0087] Application of organic iron catalysts in the preparation of PDCPD

[0088] In Application Examples 1-4, the tensile test refers to GBT1040.2-2022, the dumbbell shape is 75×5×2 mm, the test condition is 23° C., and the tensile speed is 5 mm / min.

[0089]

Application Example 1

[0090] E. Using the catalyst obtained in Example 1, add 15 mol mL -1 The catalyst toluene solution was prepared with a monomer to catalyst molar ratio of 30000:1. After stirring at room temperature for 30-60 seconds, the mixed solution was injected into the mold and cured at room temperature for 2 hours. After demolding, it was placed at room temperature for 24 hours and tested. The obtained polymer PDCPD had a conversion rate of 95.5%, a tensile strength of 45.5 MPa, and an elongation at break of 15.2%. Figure 2 The infrared spectrum of the obtained PDCPD is 1700~1550cm -1 The absorption peak between is the C=C double bond on the PDCPD molecular chain; 975cm -1 The strong absorption peak at is the non-planar swing of the trans C=CH of the non-cyclic olefin g(C=CH), indicating that there are a large number of trans structures in PDCPD.

[0091]

Application Example 2

[0092] E. Using the catalyst obtained in Example 2, add 15 mol mL -1 The catalyst toluene solution was prepared with a monomer to catalyst molar ratio of 30000:1. After stirring at room temperature for 30-60 seconds, the mixed solution was injected into the mold and cured at 40°C for 2 hours. After demolding, it was placed at room temperature for 24 hours and tested. The obtained polymer PDCPD had a conversion rate of 94.3%, a tensile strength of 32.7 MPa, and an elongation at break of 113.1%.

[0093]

Application Example 3

[0094] E. Using the catalyst obtained in Example 4, add 15 mol mL -1 The catalyst toluene solution was prepared with a monomer to catalyst molar ratio of 30000:1. After stirring at room temperature for 30-60 seconds, the mixed solution was injected into the mold and cured at room temperature for 2 hours. After demolding, it was placed at room temperature for 24 hours and tested. The obtained polymer PDCPD had a conversion rate of 98.2%, a tensile strength of 41.6 MPa, and an elongation at break of 31.2%. Figure 3 is the infrared spectrum of the obtained PDCPD, and its structure is consistent with the product obtained in Application Example 1.

[0095]

Application example 4

[0096] E. Using the catalyst obtained in Example 6, the monomers were 100 g purified DCPD and 3 g ethylidene norbornene, and the concentration was 15 mol mL -1 The catalyst toluene solution was prepared with a monomer to catalyst molar ratio of 30000:1. After stirring at room temperature for 30-60 seconds, the mixed solution was injected into the mold and cured at 50°C for 2 hours. After demolding, it was placed at room temperature for 24 hours and tested. The obtained polymer PDCPD had a conversion rate of 96.7%, a tensile strength of 40.1 MPa, and an elongation at break of 23.7%.

[0097] According to the analysis of the above application examples, it can be seen that appropriately increasing the polymerization temperature will increase the molecular kinetic energy and the collision frequency between molecules, thereby increasing the initiation rate and growth rate of the catalyst, thereby improving the catalytic activity, and the monomer conversion rate is always maintained at a high level.

[0098] By comparing the above results, it can be seen that the organic iron-based catalyst prepared by the method of the present invention has the advantages of high catalytic activity and good stability, can realize the ring-opening metathesis polymerization reaction of cyclic olefins at a relatively low temperature and normal pressure, has low preparation cost, high yield and simple process, and has the prospect of being industrialized.

[0099] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. An organic iron-based catalyst, characterized in that The molecular structure of the organic iron catalyst is shown below: Wherein, A is tert-butyl or isopropyl.

2. The method for preparing an organic iron-based catalyst according to claim 1, characterized in that: The following steps are involved: (1) Under an inert atmosphere, a phenyl-substituted pyridine compound and an alkylphosphonium chloride are dissolved in an organic solvent and reacted in the presence of a catalyst; (2) Under an inert atmosphere, add Fe-containing 2+ An organic solution is reacted; (3) After adding a silicon-based lithium compound to the product obtained in step (2), a precipitant is added to perform a crystallization reaction to obtain the organic iron-based catalyst.

3. The preparation method according to claim 2, characterized in that: The phenyl-substituted pyridine compound is 2,6-diisopropylphenylpyridine, 2,6-dimethylphenylpyridine, 2-(2,6-di-tert-butylphenyl)-6-methylpyridine or 2-(2,6-diisopropylphenyl)-6-methylpyridine; the alkyl phosphonium chloride is di-tert-butylphosphonium chloride, diethylphosphonium chloride or dicyclohexylphosphonium chloride; the molar ratio of the phenyl-substituted pyridine compound to the alkyl phosphonium chloride is 1:1-1.

2.

4. The preparation method according to claim 2 or 3, characterized in that: The catalyst described in step (1) is an organic weak acid; the reaction temperature is 50-90° C., and the reaction time is 12-20 hours.

5. The preparation method according to claim 2, characterized in that: In step (2), the Fe 2+ The molar ratio of the amount of the phenyl-substituted pyridine compound is 1:0.8-1.5; the reaction time is 50-90°C and the reaction time is 4-6h.

6. The preparation method according to claim 2, characterized in that: In step (3), the silicon-based lithium compound is trimethylsilyl methyl lithium, trimethylsilyl propyl lithium or bis(trimethylsilyl) amide lithium; the amount of the silicon-based lithium compound is about the same as that of Fe 2+ The molar ratio of the dosage is 1:0.8-1.

1.

7. The preparation method according to claim 6, characterized in that: In step (3), the crystallization reaction temperature is -18 to 20°C and the time is 1 to 10 hours.

8. Use of the organic iron-based catalyst according to claim 1 in catalyzing the ring-opening metathesis polymerization of cyclic olefins.

9. The use according to claim 8, characterized in that: The application method is: adding cyclic olefin into a reaction container, and dripping the solution of the organic iron catalyst into the reaction container under stirring conditions to carry out a curing reaction.

10. The use according to claim 9, characterized in that: The concentration of the organic iron catalyst solution is 1 to 100 mol·mL -1 ; The molar ratio of the organic iron catalyst to the cyclic olefin is 1:1000~100000; the curing reaction temperature is 10~50℃, and the reaction time is 1~3h.

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