Iron-based complex and preparation method thereof, method for catalytic preparation of polycarbonate and catalytic polymerization of cyclohexene oxide and phthalic anhydride

Abstract

The present invention relates to the field of iron complexes, and discloses a complex and a preparation method thereof, a catalytic preparation method of polycarbonate, and a method for catalyzing the polymerization of cyclohexene oxide and phthalic anhydride. The complex has a structure shown in formula (I) or formula (II), and has the characteristics of simple preparation method, high catalytic efficiency, and low production cost. On the one hand, it can cooperate with a catalyst to catalyze the reaction of CHO and CO2 to generate polycarbonate, and has good selectivity. On the other hand, the binuclear iron-based complex can catalyze the polymerization of PA and CHO alone through the synergistic effect of bimetallic agents; at the same time, it can cooperate with a catalyst to catalyze the polymerization reaction of CHO and PA to obtain a polyester with an ester content of 11%-99%. In the catalytic reaction process, the amount of catalyst used is low, there is no problem of heavy metal residues, the price is low, and the reaction conditions are mild, and it has good industrial application prospects. #imgabs0#

Description

Technical Field

[0001] The invention relates to the technical field of iron complexes, and in particular to a binuclear iron-based complex and a preparation method thereof, a method for catalytically preparing polycarbonate, and a method for catalytically polymerizing cyclohexene oxide and phthalic anhydride. Background Art

[0002] Under the background of dual carbon, low carbon has become a hot topic in current research, and chemical fixation of carbon dioxide is a feasible solution. Polyester or polycarbonate produced by ring-opening polymerization of epoxide has good biodegradability and biocompatibility, and has broad application prospects in biomedical materials, packaging materials, etc., especially it can solve the white pollution problem caused by non-degradable plastics. In addition, the polymerization of epoxide with CO2 or anhydride to prepare polycarbonate or polyester has the characteristics of low energy consumption and green environmental protection, showing good development prospects and receiving widespread attention.

[0003] At present, the catalytic systems with heavy metals such as cobalt, chromium and manganese as the catalytic center are widely studied. These catalytic systems have heavy metal residues in the polymer and are difficult to meet the requirements of the material for heavy metal ion control. Catalysts with aluminum and zinc as the central metal are more sensitive to moisture and air, and the preparation process conditions require strict requirements. Iron is widely present in nature and is environmentally friendly, cheap, easy to obtain, and low in toxicity. At the same time, iron is also widely used in the field of organic synthesis. The development of iron-based catalysts meets the requirements of green chemistry and the development trend of today's society.

[0004] In recent years, in order to further improve the catalytic performance of the complex, the research on binuclear metal complexes has attracted more and more attention. The literature (Polym Int 2019; 68: 1704–1709) discloses a piperazine-bridged ligand-supported binuclear chromium complex that catalyzes the ring-opening polymerization of cyclohexene oxide (CHO) promoted by phthalic anhydride (PA), but the generated polymerization product is mainly polyether, containing only 1% of ester units, and the ester content cannot be adjusted by changing the reaction conditions.

[0005] The binuclear iron complex studied by our research group in the early stage (Shi Z, et al., Polymer Chemistry, 2018, 9(38), 4733-4743) can catalyze cyclohexene oxide (CHO) / CO2 and has a good catalytic effect. However, the synthesis steps of the iron-based complex are more and the catalyst cost is higher, which greatly limits its prospects for industrial application. At the same time, the research also shows that the synthesis of binuclear complexes often requires more steps than that of mononuclear complexes, resulting in too low a yield, which greatly increases the cost and makes it have no obvious advantages. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of complex synthesis steps and high production cost of binuclear iron complexes in the prior art.

[0007] In order to achieve the above object, the first aspect of the present invention provides a binuclear iron-based complex having a structure shown in formula (I) or formula (II):

[0008]

[0009] Wherein, in formula (I) and formula (II), each R1 is the same, each R2 is the same; R1 and R2 are each independently selected from methyl and tert-butyl;

[0010] THF means tetrahydrofuran.

[0011] The second aspect of the present invention provides a method for preparing the binuclear iron-based complex described in the first aspect, the method comprising the following steps:

[0012] (1) Under a protective gas atmosphere, in the presence of triethylamine and tetrahydrofuran, subjecting the compound represented by formula (A) to a first reflux reaction with 3,3′-dihydroxybenzidine or 3,3′-diamino-4,4′-dihydroxybiphenyl to obtain a ligand;

[0013] (2) in the presence of an alkaline reagent and a first solvent, subjecting the iron salt and the ligand to a second reflux reaction to obtain the binuclear iron-based complex;

[0014]

[0015] Wherein, in formula (A), the definitions of R1 and R2 are the same as those in the first aspect;

[0016] The iron salt is selected from at least one of anhydrous ferric chloride and anhydrous ferric bromide, and the first solvent is selected from at least one of tetrahydrofuran and 1,4-dioxane.

[0017] The third aspect of the present invention provides a method for catalytically preparing polycarbonate, the method comprising the following steps:

[0018] The reactor containing the binuclear iron-based complex described in the first aspect and the catalyst I is evacuated and replaced with protective gas. Under the protection of the protective gas, cyclohexane oxide (CHO) is added and carbon dioxide is introduced to carry out a first polymerization reaction. After the reaction is completed, the reaction solution is dissolved in a second solvent and precipitated in acidified methanol, and then separated and dried in sequence to obtain the polycarbonate.

[0019] A fourth aspect of the present invention provides a method for catalyzing the polymerization of cyclohexene oxide and phthalic anhydride, the method comprising the following steps:

[0020] The reactor containing the binuclear iron-based complex described in the first aspect, phthalic anhydride and bis(triphenylphosphine)ammonium chloride is evacuated and replaced with protective gas, and under the protection of the protective gas, cyclohexane is added to carry out a second polymerization reaction. After the reaction is completed, the reaction liquid is dissolved with dichloromethane and precipitated in acidified methanol, and then separated and dried in sequence;

[0021] The molar ratio of the binuclear iron-based complex, bis(triphenylphosphine)ammonium chloride, phthalic anhydride and cyclohexene oxide is 1:0-3:500-6000:5000-20000.

[0022] The present invention provides a binuclear iron-based complex with good performance, which has the characteristics of simple preparation method, high catalytic efficiency and low production cost (selecting cheap and stable iron (III) as the central metal). On the one hand, it can cooperate with a catalyst to catalyze the reaction of CHO and CO2 to generate polycarbonate, and has the advantages of high selectivity, low catalyst dosage and mild reaction conditions, no heavy metal residue problem and low price, and has good industrial application prospects. On the other hand, the binuclear iron-based complex can not only cooperate with the catalyst to catalyze the polymerization reaction of CHO and PA through the synergistic effect of binuclear metals to obtain polyester with a selectivity of more than 99%, but also can catalyze the polymerization reaction of CHO and PA alone to generate polyester-polyether copolymers with different ester contents (that is, the ester content in the CHO / PA polymerization reaction can be flexibly adjusted through the catalytic system of the present invention). The presence of flexible polyether in the polyether-polyester copolymer can reduce the glass transition temperature of the polymer, improve flexibility and facilitate film formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A is the Ligand-1 in Example 1 1 H NMR spectrum;

[0024] Figure 1B is the Ligand-1 in Example 1 13 C NMR spectrum;

[0025] Figure 2A is the Ligand-2 in Example 2 1 H NMR spectrum;

[0026] Figure 2B is the Ligand-2 in Example 2 13 C NMR spectrum;

[0027] Figure 3A is Ligand-3 in Example 3 1 H NMR spectrum;

[0028] Figure 3Bis Ligand-3 in Example 3 13 C NMR spectrum;

[0029] Figure 4A is Ligand-4 in Example 4 1 H NMR spectrum;

[0030] Figure 4B is the Ligand-4 in Example 4 13 C NMR spectrum;

[0031] Figure 5A is the Ligand-5 in Example 5 1 H NMR spectrum;

[0032] Figure 5B is the Ligand-5 in Example 5 13 C NMR spectrum;

[0033] Fig. 6A is the Ligand-6 in Example 6 1 H NMR spectrum;

[0034] Figure 6B is Ligand-6 in Example 6 13 C NMR spectrum;

[0035] Figure 7 It is the UV spectra of ligands Ligand-1 to Ligand-6 and complexes Complex-1 to Complex-6;

[0036] Figure 8 It is the infrared spectra of ligands Ligand-1 to Ligand-6 and complexes Complex-1 to Complex-6;

[0037] Fig. 9 This is the H NMR spectrum of the product obtained after the polymerization reaction of cycloalkane cyclohexane CHO and CO2 in Example 7;

[0038] Fig.10 is the infrared spectrum of the product obtained after the polymerization reaction of cycloalkanecyclohexane CHO and CO2 in Example 7;

[0039] Fig.11 This is the H NMR spectrum of the product obtained after the polymerization reaction of cycloalkanecyclohexane CHO and PA in Example 14. DETAILED DESCRIPTION

[0040] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0041] As mentioned above, the first aspect of the present invention provides a binuclear iron-based complex having a structure shown in formula (I) or formula (II):

[0042]

[0043] Wherein, in formula (I) and formula (II), each R1 is the same, each R2 is the same; R1 and R2 are each independently selected from methyl (Me), tert-butyl ( t Bu);

[0044] THF means tetrahydrofuran.

[0045] Preferably, in formula (I) and formula (II), R1 is the same as R2, and R1 and R2 are selected from methyl and tert-butyl; or R1 is tert-butyl and R2 is methyl.

[0046] As mentioned above, the second aspect of the present invention provides a method for preparing the binuclear iron-based complex described in the first aspect, the method comprising the following steps:

[0047] (1) Under a protective gas atmosphere, in the presence of triethylamine and tetrahydrofuran, subjecting the compound represented by formula (A) to a first reflux reaction with 3,3′-dihydroxybenzidine or 3,3′-diamino-4,4′-dihydroxybiphenyl to obtain a ligand;

[0048] (2) in the presence of an alkaline reagent and a first solvent, subjecting the iron salt and the ligand to a second reflux reaction to obtain the binuclear iron-based complex;

[0049]

[0050] Wherein, in formula (A), the definitions of R1 and R2 are the same as those in the first aspect;

[0051] The iron salt is selected from at least one of anhydrous ferric chloride and anhydrous ferric bromide, and the first solvent is selected from at least one of tetrahydrofuran and 1,4-dioxane.

[0052] Preferably, the protective gas is argon.

[0053] Preferably, in step (1), the conditions of the first reflux reaction include: temperature of 70-80° C. and time of 5-10 h.

[0054] Preferably, the conditions of the second reflux reaction include: temperature of 70-80° C. and time of 4-8 h.

[0055] Preferably, in step (1), the molar ratio of 3,3′-dihydroxybenzidine, the compound represented by formula (A), and triethylamine is 1:3-5:3-5.

[0056] Preferably, in step (1), the molar ratio of the 3,3'-diamino-4,4'-dihydroxybiphenyl, the compound represented by formula (A), and triethylamine is 1:3-5:3-5.

[0057] More preferably, in step (1), the molar ratio of the 3,3′-dihydroxybenzidine, the compound represented by formula (A), and triethylamine is 1:4:4; the molar ratio of the 3,3′-diamino-4,4′-dihydroxybiphenyl, the compound represented by formula (A), and triethylamine is 1:4:4.

[0058] Preferably, in step (1), the amount of tetrahydrofuran used is 1-10 mL relative to 1 mmol of the compound represented by formula (A).

[0059] Preferably, in step (2), the molar ratio of the iron salt, ligand, and alkaline agent is 1:0.4-0.6:2-4. Particularly preferably, in step (2), the molar ratio of the iron salt, ligand, and alkaline agent is 1:0.5:3.

[0060] Preferably, the amount of the first solvent used is 1-15 mL relative to 0.1 mmol of the ligand.

[0061] The present invention also includes post-processing the ligand obtained in step (1) and the binuclear iron-based complex obtained in step (2) during the preparation of the binuclear iron-based complex. The present invention does not particularly limit the post-processing method, and those skilled in the art can select it as needed; for example, the post-processing may include filtering, washing, rotary evaporation, column chromatography, recrystallization, drying and other steps.

[0062] The method for preparing a binuclear iron-based complex provided by the present invention is preferably carried out under stirring conditions. The specific speed of stirring is not particularly limited, and those skilled in the art can select it according to needs.

[0063] In the present invention, the 3,3'-dihydroxybenzidine and 3,3-diamino-4,4'-dihydroxybiphenyl can be directly purchased or prepared according to methods known in the art. The present invention hereinafter exemplarily provides a method for preparing 3,3-diamino-4,4'-dihydroxybiphenyl, which comprises the following steps:

[0064] Sa: Add 0.5-1.5g 4,4'-dihydroxybiphenyl and 15-25mL glacial acetic acid to the reaction bottle, then slowly add 1-2mL nitric acid (concentration of 60-65wt%) under magnetic stirring, react at room temperature for 2-4h, add 130-170mL deionized water, continue to react at 40-60℃ for 2-4h, and stop the reaction. Filter, wash with water and ethanol three times respectively, then wash the filter cake with saturated sodium bicarbonate solution, and then vacuum dry for 12-24h to obtain dinitrobenzidine;

[0065] Sb: Add 0.4-0.6g of dinitrobenzidine, 40-60mL of water and 80-120mL of ethanol to a three-necked flask, add 4-5g of Na2S2O4 after the solid is dispersed, heat and reflux at 85-95℃ for 5-15min to stop the reaction. Spin dry the solvent, wash with water and ethanol respectively, and vacuum dry for 12-24h to obtain 3,3-diamino-4,4'-dihydroxybiphenyl.

[0066] In order to further reduce the cost of preparing binuclear iron-based complexes, the present invention provides a method for preferably preparing a compound represented by formula (A), the method comprising the following steps:

[0067] S1: dissolving the compound represented by formula (B) in solvent A, adding sodium hydroxide and formaldehyde solution and stirring at 5-30° C. for 28-53 hours; after the reaction stops, adding deionized water, adjusting the pH to 2-4 with hydrochloric acid, and then post-treating to obtain an intermediate product; the solvent A is methanol and / or water;

[0068] S2: Under an argon atmosphere, the intermediate product was dissolved in anhydrous dichloromethane, and then thionyl chloride was added dropwise. The reaction was carried out at 25-35° C. for 40-60 min. After the reaction was complete, the solvent was removed by rotary evaporation, and the mixture was dried in vacuo for 8-12 h to obtain a compound represented by formula (A);

[0069]

[0070] In formula (A) and formula (B), the definitions of R1 and R2 are the same as those in the first aspect.

[0071] Preferably, in step S1, the molar ratio of the compound represented by formula (B), sodium hydroxide and formaldehyde solution is 1: (0.5-1.31): (1.6-2.5); the formaldehyde solution is a formaldehyde aqueous solution, and the concentration of the formaldehyde solution is 37wt%-40wt%; relative to 1mmol of the compound represented by formula (B), the amount of solvent A is 0.1-5mL.

[0072] Preferably, in step S1, the amount of deionized water used is 0.1-3 mL relative to 1 mmol of formaldehyde solution.

[0073] Preferably, in step S2, the molar ratio of the intermediate product to thionyl chloride is 1:1-1.5; relative to 1 mmol of the intermediate product, the amount of anhydrous dichloromethane is 1-10 mL.

[0074] It should be noted that the present invention has no particular limitation on the specific operation of the post-treatment in step S1, and those skilled in the art can perform it according to conventional technical means in the art; illustratively, the post-treatment may include filtration, extraction, recrystallization, column chromatography, vacuum drying and the like.

[0075] The present invention provides a preferred specific implementation method for preparing the above binuclear iron-based complex. The preparation method is carried out according to the following specific steps. The synthesis route is shown in Reaction Formula I and Reaction Formula II:

[0076]

[0077]

[0078] (1) Synthesis of intermediate 1-3

[0079] The compound represented by formula (B) and sodium hydroxide are dissolved in solvent A, formaldehyde solution is added, and the mixture is stirred at 5-30° C. for 28-53 hours; after the reaction stops, deionized water is added, and the pH is adjusted to 2-4 with hydrochloric acid, and then extracted with dichloromethane, and recrystallized or subjected to column chromatography to obtain an intermediate product; the solvent A is methanol and / or water;

[0080] (2) Synthesis of the compound represented by formula (A) (intermediate product 4-6)

[0081] Under an argon atmosphere, the intermediate product was dissolved in anhydrous dichloromethane, and then thionyl chloride was added dropwise, and the reaction was carried out at 25-35° C. for 40-60 min. After the reaction was complete, the solvent was removed by rotary evaporation, and the mixture was dried in vacuo for 8-12 h to obtain a compound represented by formula (A);

[0082] (3) Synthesis of ligands Ligand-1 to Ligand-6

[0083] Under a protective gas atmosphere, in the presence of triethylamine and tetrahydrofuran, the compound represented by formula (A) is subjected to a first reflux reaction with 3,3'-dihydroxybenzidine at 70-80° C. for 5-10 hours to obtain ligands (Ligand-1 to Ligand-3); or

[0084] Under a protective gas atmosphere, in the presence of triethylamine and tetrahydrofuran, the compound represented by formula (A) and 3,3'-diamino-4,4'-dihydroxybiphenyl are subjected to a first reflux reaction at 70-80° C. for 5-10 h to obtain ligands (Ligand-4 to Ligand-6);

[0085] (4) Synthesis of binuclear iron-based complexes Complex-1 to Complex-6

[0086] In the presence of an alkaline reagent and a first solvent, subjecting the iron salt and the ligand to a second reflux reaction at 70-80° C. for 4-8 hours to obtain the binuclear iron-based complex;

[0087] The iron salt is selected from at least one of anhydrous ferric chloride and anhydrous ferric bromide, and the first solvent is selected from at least one of tetrahydrofuran and 1,4-dioxane.

[0088] As mentioned above, the third aspect of the present invention provides a method for catalytically preparing polycarbonate, the method comprising the following steps:

[0089] The reactor containing the binuclear iron-based complex and the catalyst promoter I described in the first aspect is evacuated and replaced with protective gas. Under the protection of the protective gas, cyclohexane is added and carbon dioxide is introduced to carry out a first polymerization reaction. After the reaction is completed, the reaction solution is dissolved in a second solvent and precipitated in acidified methanol, and then separated and dried in sequence to obtain the polycarbonate.

[0090] Preferably, the catalyst promoter I is selected from at least one of N-methylimidazole, dimethylaminopyridine (DMAP), bis(triphenylphosphine)ammonium chloride (PPNCl), tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide (TBAB), and tetrabutylammonium iodide (TBAI). More preferably, the catalyst promoter is selected from bis(triphenylphosphine)ammonium chloride.

[0091] Preferably, the molar ratio of the binuclear iron-based complex, the co-catalyst, and cyclohexene oxide is 1: 0.5-4: 1000-8000. More preferably, the molar ratio of the binuclear iron-based complex, the co-catalyst, and cyclohexene oxide is 1: 1.5-2.5: 1000-4000. The inventors found that in this preferred case, the catalytic efficiency of preparing polycarbonate by catalysis of the binuclear iron-based complex is higher.

[0092] Particularly preferably, the molar ratio of the binuclear iron-based complex, the catalyst promoter and cyclohexene oxide is 1:2:2000.

[0093] Preferably, the protective gas is selected from at least one of carbon dioxide, argon and nitrogen.

[0094] Preferably, the second solvent is selected from at least one of dichloromethane, chloroform and 1,2-dichloroethane.

[0095] Preferably, the conditions of the first polymerization reaction include: a reaction starting pressure of 0.1 MPa-6 MPa, a reaction temperature of 80-120° C., and a reaction time of 2-8 h. More preferably, the conditions of the first polymerization reaction include: a reaction starting pressure of 2 MPa-4 MPa, a reaction temperature of 90-120° C., and a reaction time of 3-8 h. The inventors found during the research process that in this preferred case, the catalytic activity of the catalyst is higher.

[0096] As mentioned above, the fourth aspect of the present invention provides a method for catalyzing the polymerization of cyclohexene oxide and phthalic anhydride, the method comprising the following steps:

[0097] The reactor containing the binuclear iron-based complex described in the first aspect, phthalic anhydride and bis(triphenylphosphine)ammonium chloride is evacuated and replaced with protective gas, and under the protection of the protective gas, cyclohexane is added to carry out a second polymerization reaction. After the reaction is completed, the reaction liquid is dissolved with dichloromethane and precipitated in acidified methanol, and then separated and dried in sequence to obtain the polyester;

[0098] The molar ratio of the binuclear iron-based complex, bis(triphenylphosphine)ammonium chloride, phthalic anhydride and cyclohexene oxide is 1:0-3:500-6000:5000-20000.

[0099] Preferably, the molar ratio of the binuclear iron-based complex, bis(triphenylphosphine)ammonium chloride, phthalic anhydride, and cyclohexene oxide is 1: 0-2: 1000-4000: 5000-20000. The inventors found that in this preferred case, the binuclear iron-based complex has a better effect of catalyzing the polymerization reaction of cyclohexene oxide and phthalic anhydride, wherein, when bis(triphenylphosphine)ammonium chloride is not added, the binuclear iron-based complex can efficiently catalyze the polymerization reaction of cyclohexene oxide and phthalic anhydride to generate a polyether-polyester mixture containing polyether, and after adding bis(triphenylphosphine)ammonium chloride, the ester content in the polymer can be increased by adjusting the molar ratio of the binuclear iron-based complex, bis(triphenylphosphine)ammonium chloride, phthalic anhydride, and cyclohexene oxide.

[0100] Preferably, the conditions of the second polymerization reaction include: reaction temperature of 80-100° C., and reaction time of 10-30 min.

[0101] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all reagents used are commercially available chemical reagents, and there is no particular limitation thereto. The water used in the following examples is all deionized water, and the room temperature represents 25±3°C.

[0102] In the following preparation examples, Preparation Examples 1-3 are methods for preparing the compound represented by formula (A) provided by the present invention, and Preparation Example 4 is a method for preparing 3,3-diamino-4,4′-dihydroxybiphenyl provided by the present invention.

[0103] Preparation Example 1

[0104] In formula (A), R1 and R2 are both tert-butyl ( t Bu), the compound represented by formula (A) is 2,4-di-tert-butyl-6-chloromethylphenol, and is prepared by the following steps:

[0105] S1: Add 40mL of methanol to a 100mL reaction bottle, then add 2,4-di-tert-butylphenol (48.4mmol) and sodium hydroxide (53.48mmol) respectively, stir for 30min until they are completely dissolved, add formaldehyde solution (96.9mmol) with a mass fraction of 40wt%, use a constant temperature water solution to control the reaction temperature to 25°C, and continue the reaction for 28h. After the reaction stops, transfer the reaction solution to a beaker and add 100mL of deionized water. Adjust the pH to 3 with hydrochloric acid while stirring. During this process, the solution turns from yellow to white and a white precipitate appears. After filtering, a solid crude product is obtained. The crude product is recrystallized using n-hexane and vacuum dried to obtain 2,4-di-tert-butyl-6-hydroxymethylphenol (intermediate product 1), a white needle-like substance with a yield of 72%. 1 H NMR (500MHz, CDCl3) δ7.57 (s, 1H), 7.31 (d, J = 2.4Hz, 1H), 6.91 (d, J = 2.3Hz, 1H), 4.84 (d, J = 5.2Hz, 2H), 1.45 (s, 9H), 1.31 (s, 9H).

[0106] S2: In an argon atmosphere, anhydrous dichloromethane (30 mL) and 2,4-di-tert-butyl-6-hydroxymethylphenol (10 mmol) were added to a 100 mL reaction bottle, stirred and dissolved, and then thionyl chloride (12 mmol) was slowly added dropwise, and the reaction was carried out at 25°C for 40 min. The reaction was monitored by TLC, and the reaction was stopped after the reaction was complete. The solvent and unreacted thionyl chloride were removed by rotating on a rotary evaporator for 30 min, and vacuum dried for 12 h to obtain 2,4-di-tert-butyl-6-chloromethylphenol (intermediate product 4), a colorless oil with a yield of 100%. 1HNMR (500MHz, CDCl3) δ7.23 (dd, J=7.8, 1.1Hz, 1H), 7.18 (d, J=2.4Hz, 2H), 7.00 –6.94(m,3H),6.84(t,J=8.3Hz,2H),4.13(s,4H),1.39(s,18H),1.26(s,18H).

[0107] Preparation Example 2

[0108] In formula (A), R1 is tert-butyl ( t When R2 is methyl (Me), the compound represented by formula (A) is 2-tert-butyl-4-methyl-6-chloromethylphenol, and is prepared by the following steps:

[0109] S1: Add 40mL of methanol to a 100mL reaction bottle, then add 2-tert-butyl-4-methylphenol (60.8mmol) and sodium hydroxide (79mmol) respectively, stir for 15min to dissolve, add formaldehyde solution (149mmol) with a mass fraction of 40wt%, use a constant temperature water solution to control the reaction temperature to 25°C, and continue the reaction for 53h. After the reaction stops, transfer the reaction solution to a beaker and add 100mL of deionized water. Adjust the pH to 3 with hydrochloric acid while stirring, and a light red oil will appear. Use CH2Cl2 to extract 3 times (50mL each time), then wash with saturated brine, dry with anhydrous sodium sulfate, and column chromatography (the volume ratio of petroleum ether to ethyl acetate is 20:1) to obtain 2-tert-butyl-4-methyl-6-hydroxymethylphenol (intermediate product 2, yield 70%). 1 HNMR (500MHz, CDCl3) δ7.51(s,1H),7.05(s,1H),6.71(s,1H),4.81(s,2H),2.26(s,3H),1.42(s,9H).

[0110] S2: In an argon atmosphere, anhydrous dichloromethane (30 mL) and 2-tert-butyl-4-methyl-6-hydroxymethylphenol (10 mmol) were added to a 100 mL reaction bottle, stirred and dissolved, and then thionyl chloride (12 mmol) was slowly added dropwise, and the reaction was carried out at 25°C for 40 min. The reaction was monitored by TLC, and the reaction was stopped after the reaction was complete. The solvent and unreacted thionyl chloride were removed by a rotary evaporator, and vacuum dried for 12 h to obtain 2-tert-butyl-4-methyl-6-chloromethylphenol (intermediate product 5), a colorless oil, with a yield of 100%. 1 H NMR (500MHz, CDCl3) δ7.51(s,1H),7.05(s,1H),6.71(s,1H),4.81(s,2H),2.26(s,3H),1.42(s,9H).

[0111] Preparation Example 3

[0112] In formula (A), when R1 and R2 are both methyl (Me), the compound represented by formula (A) is 2,4-dimethyl-6-chloromethylphenol, which is prepared by the following steps:

[0113] S1: Add 20mL of deionized water to a 100mL reaction bottle, then add sodium hydroxide (63mmol) and 2,4-dimethylphenol (100mmol) respectively, stir for 15min until they are completely dissolved, add a 40wt% formaldehyde solution (167.6mmol), stir at 5°C for 2h, and continue to react at 25°C for 43h. After the reaction stops, transfer the reaction solution to a beaker and add 100mL of deionized water. Adjust the pH to 3 with hydrochloric acid while stirring until a dark red oil appears. Extract with CH2Cl2 3 times (50mL each time), then wash with saturated brine, dry with anhydrous sodium sulfate, and obtain 2,4-dimethyl-6-hydroxymethylphenol (intermediate product 3) as a white solid with a yield of 76%. 1 H NMR (500MHz, CDCl3) δ7.16(s,1H),6.91(s,1H),6.67(s,1H),4.78(s,2H),2.23(s,3H),2.22(s,3H).

[0114] S2: In an argon atmosphere, anhydrous dichloromethane (30 mL) and 2,4-dimethyl-6-hydroxymethylphenol (10 mmol) were added to a 100 mL reaction bottle, stirred and dissolved, and then thionyl chloride (12 mmol) was slowly added dropwise, and the reaction was carried out at 25°C for 60 min. The reaction was monitored by TLC, and the reaction was stopped after the reaction was complete. The solvent and unreacted thionyl chloride were removed by a rotary evaporator, and vacuum dried for 12 h to obtain 2,4-dimethyl-6-chloromethylphenol (intermediate product 6) as a white solid with a yield of 97%. 1 H NMR (500MHz, CDCl3) δ6.95(s,1H),6.93(s,1H),4.65(s,2H),2.25(s,3H),2.24(s,3H).

[0115] Preparation Example 4

[0116] Sa: Add 1g 4,4'-dihydroxybiphenyl and 20mL glacial acetic acid to the reaction bottle, then slowly add 2mL nitric acid (concentration 65wt%) under magnetic stirring, react at room temperature for 3h, add 150mL water, continue to react at 50℃ for 3h, and stop the reaction. Filter, wash with water and ethanol three times respectively, then wash the filter cake with saturated sodium bicarbonate solution, and then vacuum dry for 12h to obtain dinitrobenzidine (intermediate product 7) as an orange-yellow solid with a yield of 90%. 1 H NMR (500MHz, DMSO): δ11.13 (s, 2H), 8.14 (d, J = 2.4Hz, 2H), 7.87 (dd, J = 8.7, 2.4Hz, 2H), 7.20 (d, J = 8.7Hz, 2H).

[0117] Sb: Add 0.5 g of dinitrobenzidine, 50 mL of water and 100 mL of ethanol to a 250 mL three-necked flask, add 4.47 g of Na2S2O4 after the solid is dispersed, and heat under reflux at 90°C for 10 min to stop the reaction. The solvent is spin-dried, washed with water and ethanol respectively, and vacuum dried for 12 h to obtain 3,3-diamino-4,4'-dihydroxybiphenyl (intermediate product 8) as a white solid with a yield of 52%. 1 HNMR (500MHz, DMSO) δ8.91 (s, 2H), 6.75 (d, J = 2.2Hz, 2H), 6.63 (d, J = 8.1Hz, 2H), 6.53 (dd, J = 8.1, 2.2Hz, 2H), 4.57 (s, 4H).

[0118] In the following examples, the compound represented by formula (A) prepared in the above-mentioned Preparation Examples 1-3 and the 3,3-diamino-4,4'-dihydroxybiphenyl prepared in Preparation Example 4 were used in Examples 1-6 to prepare binuclear iron-based complexes. Examples 7-13 are methods for catalytically preparing polycarbonate provided by the present invention, and Examples 14-24 are methods for catalytically polymerizing cyclohexene oxide and phthalic anhydride provided by the present invention.

[0119] Example 1

[0120] This embodiment provides a binuclear iron-based complex, which is prepared by the following steps:

[0121] (1) Synthesis of Ligand-1

[0122] Under argon atmosphere, in a 50 mL reaction bottle, a tetrahydrofuran solution (10 mL) containing 3,3'-dihydroxybenzidine (1 mmol) was added to a tetrahydrofuran solution (10 mL) of 2,4-di-tert-butyl-6-chloromethylphenol (4 mmol), and then triethylamine (4 mmol) was added to the reaction bottle. The solution changed from brown-red to yellow and was heated to reflux at 75°C for 10 h to stop the reaction. After cooling, the white precipitate was removed by filtration, and the solvent was removed by rotary evaporation to obtain a brown oil. After separation by column chromatography (the volume ratio of petroleum ether to ethyl acetate was 5:1), the solvent was dried and recrystallized using acetonitrile to obtain the ligand Ligand-1 as a white solid (yield: 79%). 1 H NMR spectrum is shown in Figure 1A , 13 C NMR spectrum is shown in Figure 1B , UV spectrum is shown in Figure 7 , infrared spectrum see Figure 8 ; 1 H NMR (500MHz, CDCl3) δ7.42 (s, 4H), 7.24–7.16 (m, 6H), 6.95 (d, J = 13.6Hz, 8H), 4.13 (s, 8H), 1.38 (s, 36H), 1.26 (s, 36H). 13 C NMR(126MHz, CDCl3)δ152.28(s),151.34(s),141.87(s),138.04(s),135.70(s),134.88(s),125.91(s),123 .78(s),122.17(s),121.81(s),119.22(s),114.61(s),56.51(s),34.75(s),34.29(s),31.76(s),29.95(s).

[0123] (2) Synthesis of binuclear iron-based complex Complex-1

[0124] In a 50 mL reaction bottle, a tetrahydrofuran (10 mL) solution containing anhydrous FeCl3 (0.4 mmol) was added to a tetrahydrofuran (10 mL) solution containing ligand Ligand-1 (0.2 mmol), and then triethylamine (1.2 mmol) was added to the reaction bottle. The reaction was stopped after heating under reflux at 75°C for 8 h. After cooling to room temperature, the mixture was filtered through diatomaceous earth, and the solvent was removed by rotary evaporation. The mixture was recrystallized using methanol and dichloromethane to obtain a binuclear iron-based complex Complex-1 with a yield of 80%. Its UV spectrum is shown in FIG. Figure 7 , infrared spectrum see Figure 8 . HRMS (m / z): [M+Na-2THF] + Calcd for [C72 H 94 Fe2N2O6+Na] + :1217.5703, found:1217.5732.Anal.calcd for C 72 H 94 Fe2N2O6: C, 72.35; H, 7.93; N, 2.34. Found: C, 71.98; H, 7.88; N, 2.29.

[0125] The complex was successfully synthesized by performing ultraviolet, infrared, high-resolution mass spectrometry characterization and elemental analysis on the complex.

[0126] Example 2

[0127] This embodiment provides a binuclear iron-based complex, which is prepared by the following steps:

[0128] (1) Synthesis of Ligand-2

[0129] Under argon atmosphere, in a 50mL reaction bottle, a solution of 3,3′-dihydroxybenzidine (1mmol) in tetrahydrofuran (10mL) was added to a solution of 2-tert-butyl-4-methyl-6-chloromethylphenol (4mmol) in tetrahydrofuran (10mL), and then triethylamine (4mmol) was added to the reaction bottle. The solution changed from brown-red to earthy yellow, and was heated to reflux at 75°C for 10h to stop the reaction. After cooling, the white precipitate was filtered to remove the white precipitate. The solvent was removed by rotary evaporation to obtain a brown oil, which was then separated by column chromatography (the volume ratio of petroleum ether to ethyl acetate was 5:1), the solvent was dried, and acetonitrile was used for recrystallization to obtain the ligand Ligand-2, a white solid (yield: 85%). 1 H NMR spectrum is shown in Figure 2A , 13 C NMR spectrum is shown in Figure 2B , UV spectrum is shown in Figure 7 , infrared spectrum see Figure 8 ; 1 H NMR (500MHz, CDCl3) δ7.54(s,4H),7.01–6.94(m,6H),6.83(s,4H),6.35–6.16(m,4H),4.08(s,8H),2.27(s,12H),1.38(s,36H). 13C NMR (126MHz, CDCl3) δ 152.89 (s), 149.52 (s), 137.18–137.00 (m), 136.66 (d, J = 48.5Hz), 134.35 (s), 129.31 (s), 128.15 (s), 127. 76(s),122.09(s),121.37(s),119.42(s),114.47(s),77.41(s),77.16(s),76.91(s),56.26(s),34.77(s),29.95(s),21.02(s).

[0130] (2) Synthesis of binuclear iron-based complex Complex-2

[0131] In a 50 mL reaction bottle, a tetrahydrofuran (10 mL) solution containing anhydrous FeCl3 (0.4 mmol) was added to a tetrahydrofuran (15 mL) solution containing ligand-2 (0.2 mmol), and then triethylamine (1.2 mmol) was added to the reaction bottle. The reaction was stopped after heating under reflux at 75°C for 8 h. After cooling to room temperature, the mixture was filtered through diatomaceous earth, and the solvent was removed by rotary evaporation. The binuclear iron-based complex Complex-2 was obtained by recrystallization with methanol as a black solid (yield: 82%). Its UV spectrum is shown in FIG. Figure 7 , infrared spectrum see Figure 8 . HRMS (m / z): [M+Na-2THF] + Calcd for [C 60 H 70 Fe2N2O6+Na] + :1049.3825, found:1049.3828.Anal.calcd for C 60 H 70 Fe2N2O6: C, 70.18; H, 6.87; N, 2.73. Found: C, 69.88; H, 6.79; N, 2.68.

[0132] The complex was successfully synthesized by performing ultraviolet, infrared, high-resolution mass spectrometry characterization and elemental analysis on the complex.

[0133] Example 3

[0134] This embodiment provides a binuclear iron-based complex, which is prepared by the following steps:

[0135] (1) Synthesis of Ligand-3

[0136] Under argon atmosphere, in a 50 mL reaction bottle, a solution of 3,3′-dihydroxybenzidine (1 mmol) in tetrahydrofuran (10 mL) was added to a solution of 2,4-dimethyl-6-chloromethylphenol (4 mmol) in tetrahydrofuran (10 mL), and then triethylamine (4 mmol) was added to the reaction bottle. The solution changed from brown-red to yellow and was heated to reflux at 75°C for 10 h to stop the reaction. After cooling, the white precipitate was removed by filtration, and the solvent was removed by rotary evaporation to obtain a brown oil. After separation by column chromatography (the volume ratio of petroleum ether to ethyl acetate was 5:1), the solvent was dried and recrystallized using acetonitrile to obtain the ligand Ligand-3 as a white solid (yield was 81%). 1 H NMR spectrum is shown in Figure 3A , 13 C NMR spectrum is shown in Figure 3B , UV spectrum is shown in Figure 7 , infrared spectrum see Figure 8 ; 1 H NMR (500MHz, DMSO) δ10.46(s,2H),8.92(s,4H),7.13(d,J=8.4Hz,2H),7.03(d,J=2.0Hz,2H),6 .87(dd,J=8.3,1.9Hz,2H),6.81(s,4H),6.75(s,4H),4.08(s,8H),2.10(s,12H),2.07(s,12H). 13 C NMR(126MHz,DMSO)δ151.71(s),151.33(s),136.18(s),135.70(s),130.32(s),128.18(s),127.1 0(s),123.90(s),122.55(s),122.08(s),117.34(s),113.49(s),53.28(s),20.15(s),16.04(s).

[0137] (2) Synthesis of binuclear iron-based complex Complex-3

[0138] In a 50 mL reaction bottle, a solution of anhydrous FeCl3 (0.4 mmol) in tetrahydrofuran (10 mL) was added to a solution of ligand-3 (0.2 mmol) in tetrahydrofuran (15 mL), and then triethylamine (1.2 mmol) was added to the reaction bottle. The reaction was stopped after heating under reflux at 75 ° C for 8 h. After cooling to room temperature, the mixture was filtered through diatomaceous earth, and the solvent was removed by rotary evaporation. The binuclear iron-based complex Complex-3 was obtained by recrystallization with methanol as a black solid (yield of 82%). Its UV spectrum is shown in FIG. Figure 7 , infrared spectrum see Figure 8. HRMS (m / z): [M+Na-2THF] + Calcd for [C 48 H 46 Fe2N2O6+Na] + :881.1947, found:881.1949.Anal.calcd for C 48 H 46 Fe2N2O6: C, 67.15; H, 5.40; N, 3.26. Found: C, 66.89; H, 5.29; N, 3.24.

[0139] The complex was successfully synthesized by performing ultraviolet, infrared, high-resolution mass spectrometry characterization and elemental analysis on the complex.

[0140] Example 4

[0141] This embodiment provides a binuclear iron-based complex, which is prepared by the following steps:

[0142] (1) Synthesis of Ligand-4

[0143] Under argon atmosphere, in a 50 mL reaction bottle, a tetrahydrofuran (10 mL) solution containing 3,3'-diamino-4,4'-dihydroxybiphenyl (1 mmol) was added to a tetrahydrofuran (10 mL) solution of 2,4-di-tert-butyl-6-chloromethylphenol (4 mmol), and then triethylamine (4 mmol) was added to the reaction bottle. The solution changed from brown-red to yellow and was heated to reflux at 75°C for 10 h to stop the reaction. After cooling, the white precipitate was removed by filtration, and the solvent was removed by rotary evaporation to obtain a brown oil. After separation by column chromatography (the volume ratio of petroleum ether to ethyl acetate was 5:1), the solvent was dried and recrystallized using acetonitrile to obtain the ligand Ligand-4 as a white solid with a yield of 79%. 1 H NMR spectrum is shown in Figure 4A , 13 C NMR spectrum is shown in Figure 4B , UV spectrum is shown in Figure 7 , infrared spectrum see Figure 8 ; 1 H NMR (500MHz, CDCl3) δ7.47(s,4H),7.34(d,J=1.9Hz,2H),7.19(d,J=2.3Hz,4H),7.03(d,J=2.2Hz, 4H), 6.96 (dd, J=8.3, 2.0Hz, 2H), 6.86 (d, J=8.2Hz, 2H), 4.16 (s, 8H), 1.38 (s, 36H), 1.28 (s, 36H). 13C NMR(126MHz, CDCl3)δ152.22(s),150.39(s),141.87(s),135.72(s),135.52(s),133.64(s),125.81(s),124 .10(s),123.84(s),121.85(s),120.69(s),116.33(s),56.48(s),34.72(s),34.32(s),31.81(s),29.94(s).

[0144] (2) Synthesis of binuclear iron-based complex Complex-4

[0145] In a 50 mL reaction bottle, a tetrahydrofuran (10 mL) solution containing anhydrous FeCl3 (0.6 mmol) was added to a tetrahydrofuran (10 mL) solution containing ligand-4 (0.3 mmol), and then triethylamine (1.8 mmol) was added to the reaction bottle. The reaction was stopped after heating under reflux at 75°C for 8 h. After cooling to room temperature, the mixture was filtered through diatomaceous earth, and the solvent was removed by rotary evaporation. The mixture was recrystallized using tetrahydrofuran and methanol to obtain a binuclear iron-based complex Complex-4 as a black solid with a yield of 76%. Its UV spectrum is shown in FIG. Figure 7 , infrared spectrum see Figure 8 . HRMS (m / z): [M+Na-2THF] + Calcd for [C 72 H 94 Fe2N2O6+Na] + :1217.5703, found:1217.5708.Anal.calcd for C 72 H 94 Fe2N2O6: C, 72.35; H, 7.93; N, 2.34. Found: C, 71.86; H, 7.89; N, 2.38.

[0146] The complex was successfully synthesized by performing ultraviolet, infrared, high-resolution mass spectrometry characterization and elemental analysis on the complex.

[0147] Example 5

[0148] This embodiment provides a binuclear iron-based complex, which is prepared by the following steps:

[0149] (1) Synthesis of Ligand-5

[0150] Under argon atmosphere, in a 50mL reaction bottle, a tetrahydrofuran (10mL) solution containing 3,3′-diamino-4,4′-dihydroxybiphenyl (1mmol) was added to a tetrahydrofuran (10mL) solution of 2-tert-butyl-4-methyl-6-chloromethylphenol (4mmol), and then triethylamine (4mmol) was added to the reaction bottle. The solution changed from brown-red to yellow and was heated to reflux at 75°C for 10h to stop the reaction. After cooling, the white precipitate was removed by filtration and the solvent was removed by rotary evaporation to obtain a brown oil. After separation by column chromatography (the volume ratio of petroleum ether to ethyl acetate was 3:1), the solvent was dried and recrystallized using acetonitrile to obtain the ligand Ligand-5 as a white solid with a yield of 79%. 1 H NMR spectrum is shown in Figure 5A , 13 C NMR spectrum is shown in Figure 5B , UV spectrum is shown in Figure 7 , infrared spectrum see Figure 8 ; 1 H NMR(500MHz,DMSO)δ10.91(s,2H),8.98(s,4H),7.27(s,2H),7.01–6.92(m,2 H), 6.85 (dd, J = 20.8, 8.8Hz, 10H), 4.09 (s, 8H), 2.16 (s, 12H), 1.31 (s, 36H). 13 C NMR(126MHz,DMSO)δ152.41(s),149.86(s),136.00(d),131.54(s),128.80(s),126.63(d) ,123.11(s),122.20(s),119.84(s),115.72(s),53.79(s),34.24(s),29.44(s),20.50(s).

[0151] (2) Synthesis of binuclear iron-based complex Complex-5

[0152] In a 50 mL reaction bottle, a tetrahydrofuran (10 mL) solution containing anhydrous FeCl3 (0.4 mmol) was added to a tetrahydrofuran (10 mL) solution containing ligand-5 (0.2 mmol), and then triethylamine (1.2 mmol) was added to the reaction bottle. The reaction was stopped after heating under reflux at 75°C for 8 h. After cooling to room temperature, the mixture was filtered through diatomaceous earth, and the solvent was removed by rotary evaporation. The binuclear iron-based complex Complex-5 was obtained by recrystallization with methanol. The yield was 81%. Its UV spectrum is shown in FIG. Figure 7 , infrared spectrum see Figure 8 . HRMS (m / z): [M+Na-2THF] + Calcd for [C60 H 70 Fe2N2O6+Na] + :1049.3825, found:1049.3828.Anal.calcd for C 60 H 70 Fe2N2O6: C, 70.18; H, 6.87; N, 2.73. Found: C, 70.01; H, 6.91; N, 2.69.

[0153] The complex was successfully synthesized by performing ultraviolet, infrared, high-resolution mass spectrometry characterization and elemental analysis on the complex.

[0154] Example 6

[0155] This embodiment provides a binuclear iron-based complex, which is prepared by the following steps:

[0156] (1) Synthesis of Ligand-6

[0157] Under an argon atmosphere, a tetrahydrofuran (10 mL) solution containing 3,3'-diamino-4,4'-dihydroxybiphenyl (1 mmol) was added to a tetrahydrofuran (10 mL) solution of 2,4-dimethyl-6-chloromethylphenol (4 mmol) in a 50 mL reaction bottle, and then triethylamine (4 mmol) was added to the reaction bottle. The solution changed from brown-red to yellow, and the reaction was stopped after heating and reflux at 75°C for 10 hours. After cooling, the white precipitate was removed by filtration. The solvent was removed by rotary evaporation to obtain a brown oil, which was then separated by column chromatography (the volume ratio of dichloromethane to methanol was 50:1), and the solvent was dried and recrystallized using acetonitrile to obtain the ligand Ligand-6 as a white solid with a yield of 78%. 1 H NMR spectrum is shown in Fig. 6A , 13 C NMR spectrum is shown in Figure 6B , UV spectrum is shown in Figure 7 , infrared spectrum see Figure 8 ; 1 H NMR (500MHz, DMSO) δ10.30(s,2H),8.96(s,4H),7.07(d,J=1.6Hz,2H),6.93(dd,J=8.2,1 .8Hz,2H),6.86(d,J=8.2Hz,2H),6.77(s,8H),4.09(s,8H),2.12(s,12H),2.09(s,12H). 13C NMR(126MHz,DMSO)δ152.28(s),150.66(s),136.71(s),132.07(s),130.89(s),128.75(s), 127.54(s),124.42(s),122.89(s),120.57(s),116.48(s),53.81(s),20.64(s),16.55(s).

[0158] (2) Synthesis of binuclear iron-based complex Complex-6

[0159] In a 50 mL reaction bottle, a tetrahydrofuran (10 mL) solution containing anhydrous FeCl3 (0.4 mmol) was added to a tetrahydrofuran (10 mL) solution containing ligand-6 (0.2 mmol), and then triethylamine (1.2 mmol) was added to the reaction bottle. The reaction was stopped after heating under reflux at 75°C for 8 h. After cooling to room temperature, the mixture was filtered through diatomaceous earth, the solvent was removed by rotary evaporation, and the mixture was washed with methanol to obtain a binuclear iron-based complex Complex-6 with a yield of 75%. Its UV spectrum is shown in FIG. Figure 7 , infrared spectrum see Figure 8 . HRMS(ESI m / z):[M+Na-2THF] + Calcd for [C 48 H 46 Fe2N2O6+Na] + :881.1947, found:881.1939.Anal.calcd for C 48 H 46 Fe2N2O6: C, 67.15; H, 5.40; N, 3.26. Found: C, 66.95; H, 5.31; N, 3.12.

[0160] The complex was successfully synthesized by performing ultraviolet, infrared, high-resolution mass spectrometry characterization and elemental analysis on the complex.

[0161] Example 7

[0162] This embodiment provides a method for preparing polycarbonate by catalysis, the method comprising the following steps:

[0163] In a dry 50mL stainless steel reactor, binuclear iron-based complex Complex-1 (as catalyst) and co-catalyst PPNCl were added, and after sealing, vacuuming and argon replacement were repeated through a double-row tube. Under argon protection, 2mL of cyclohexene oxide (CHO) was added, and then CO2 was introduced to make the pressure in the reactor reach 3MPa, and the reaction was carried out at 100℃ for 3h;

[0164] The molar ratio of the binuclear iron-based complex, PPNCl and cyclohexene oxide is 1:2:2000;

[0165] After the reaction is completed, the composition of the product after the reaction is completed is detected by nuclear magnetic resonance and infrared. Fig. 9 , Fig.10 They are respectively the H NMR spectrum and IR spectrum of the product obtained after the polymerization reaction of CHO and CO2. The conversion rate of cyclohexene oxide, TOF value and carbonate content are calculated according to the following formulas. The selectivity of polycarbonate is determined by infrared spectroscopy, and the molecular weight of the polymer is tested by GPC. The specific results are shown in Table 1.

[0166]

[0167] In the above calculation formula, I 4.55-4.75 I represents the chemical shift of hydrogen protons on carbons connected to oxygen on polycarbonate; 3.12 I represents the chemical shift of hydrogen protons on the epoxy ring in cyclohexene oxide; 3.40 Represents the chemical shift of the hydrogen proton on the carbon attached to the oxygen on the polyether.

[0168] Example 8

[0169] This example is carried out using a method similar to that of Example 7, except that the catalyst Complex-1 in Example 1 is replaced by Complex-2, and the remaining steps are the same as those of Example 7.

[0170] Example 9

[0171] This example is carried out using a method similar to that of Example 7, except that the catalyst Complex-1 in Example 1 is replaced by Complex-4, and the remaining steps are the same as those of Example 7.

[0172] Example 10

[0173] This example is carried out using a method similar to that of Example 7, except that the catalyst Complex-1 in Example 1 is replaced by Complex-5, and the remaining steps are the same as those of Example 7.

[0174] Embodiment 11

[0175] This example is carried out using a method similar to that of Example 7, except that the polymerization reaction temperature is 110° C., and the remaining steps are the same as those of Example 7.

[0176] Example 12

[0177] This example is carried out using a method similar to that of Example 7, except that the polymerization reaction time of this example is 8 hours, and the remaining steps are the same as those of Example 7.

[0178] Embodiment 13

[0179] This example is carried out using a method similar to that of Example 7, except that in this example, CO2 is introduced so that the pressure in the reactor reaches 1 MPa; the remaining steps are the same as those of Example 7.

[0180] Table 1

[0181]

[0182] Embodiment 14

[0183] This embodiment provides a method for catalyzing the polymerization of cyclohexene oxide and phthalic anhydride, the method comprising the following steps:

[0184] In a dry 10 mL thick-walled reaction tube equipped with a magnet, binuclear iron-based complex Complex-2 (as a catalyst) and phthalic anhydride (PA) were added respectively. The reaction tube was sealed and subjected to multiple cycles of vacuum evacuation and argon replacement through a double-row tube. Under argon protection, 1 mL of cyclohexene oxide (CHO) was added and reacted at 90°C for 10 min.

[0185] The molar ratio of the binuclear iron-based complex, PA and cyclohexene oxide is 1:4000:20000.

[0186] After the reaction is completed, 1 H NMR was used to detect the composition of the product after the reaction. Fig.11 The H NMR spectrum of the product obtained after the polymerization reaction of CHO and PA was used to calculate the conversion rate of cyclohexene oxide and the proportion of ester chains and ether chains in the polymerization product. The glass transition temperature Tg of the polymerization product was determined by DSC and the catalytic efficiency was calculated. The specific results are shown in Table 2.

[0187]

[0188] In the calculation formula of PA conversion rate, I 7.39-7.58 I represents the chemical shift of hydrogen protons on the benzene ring of polyester; 7.90-8.00 represents the chemical shift of hydrogen protons on the benzene ring of PA;

[0189] In the calculation formula of CHO conversion rate, I 4.77-5.31 I represents the chemical shift of the hydrogen proton on the six-membered ring carbon connected to oxygen on the polyester; 3.12 I represents the chemical shift of hydrogen protons on the carbon of the epoxy cyclohexane ring; 3.40 It represents the chemical shift of the hydrogen proton on the carbon of the six-membered ring connected to the oxygen on the polyether.

[0190] Embodiment 15

[0191] This example is carried out using a method similar to that of Example 14, except that the molar ratio of the binuclear iron-based complex, PA, and cyclohexene oxide is 1:2000:10000; the remaining steps are the same as those of Example 14.

[0192] Example 16

[0193] This example is carried out using a method similar to that of Example 14, except that the molar ratio of the binuclear iron-based complex, PA, and cyclohexene oxide is 1:1000:5000; the remaining steps are the same as those of Example 14.

[0194] Embodiment 17

[0195] This example is carried out using a method similar to that of Example 16, except that the complex Complex-2 in Example 16 is replaced by Complex-1; the remaining steps are the same as those of Example 16.

[0196] Embodiment 18

[0197] This example is carried out using a method similar to that of Example 16, except that the complex Complex-2 in Example 16 is replaced by Complex-3; the remaining steps are the same as those of Example 16.

[0198] Embodiment 19

[0199] This example is carried out using a method similar to that of Example 16, except that the complex Complex-2 in Example 16 is replaced by Complex-4; the remaining steps are the same as those of Example 16.

[0200] Embodiment 20

[0201] This example is carried out using a method similar to that of Example 16, except that the complex Complex-2 in Example 16 is replaced by Complex-5; the remaining steps are the same as those of Example 16.

[0202] Embodiment 21

[0203] This example is carried out using a method similar to that of Example 16, except that the complex Complex-2 in Example 16 is replaced by Complex-6; the remaining steps are the same as those of Example 16.

[0204] Embodiment 22

[0205] The present embodiment provides a method for catalyzing the polymerization of cyclohexene oxide and phthalic anhydride, the method comprising the following steps: adding a binuclear iron-based complex Complex-2, PA and a catalyst promoter PPNCl to a dry 10 mL thick-walled reaction tube equipped with a magnet, sealing the reaction tube, and performing multiple cycles of vacuuming and argon replacement through a double-row tube, adding 1 mL of cyclohexene oxide under argon protection, and reacting at 90° C. for 30 minutes;

[0206] The molar ratio of the binuclear iron-based complex, PPNCl, PA and cyclohexene oxide is 1:1:1000:5000.

[0207] Embodiment 23

[0208] This example is carried out using a method similar to that of Example 22, except that the molar ratio of the binuclear iron-based complex, PPNCl, PA, and cyclohexene oxide is 1:1.5:1000:5000; the remaining steps are the same as those of Example 22.

[0209] Embodiment 24

[0210] This example is carried out using a method similar to that of Example 22, except that the molar ratio of the binuclear iron-based complex, PPNCl, PA, and cyclohexene oxide is 1:2:1000:5000; the remaining steps are the same as those of Example 22.

[0211] Comparative Example 1

[0212] This comparative example was carried out in a similar manner to Example 16, except that the iron-based complex Complex-4 synthesized in Example 4 of CN114369122A was used as a catalyst, and the remaining steps were the same as those of Example 16. After the reaction was completed, the conversion rate of cyclohexene oxide and the selectivity of polycarbonate were tested, and the specific results are shown in Table 2.

[0213] Comparative Example 2

[0214] This comparative example was carried out in a similar manner to Example 16, except that the catalyst in the literature (Shi Z, et al., Polymer Chemistry, 2018, 9 (38), 4733-4743) was used to replace Complex-1 in Example 16, and the other conditions were the same as those in Example 16. After the reaction was completed, the conversion rate of cyclohexene oxide and the selectivity of polycarbonate were tested, and the specific results are shown in Table 2.

[0215] The catalyst structure in the literature is:

[0216]

[0217] Table 2

[0218]

[0219]

[0220] The present invention provides a binuclear iron-based complex having the characteristics of high catalytic efficiency. Meanwhile, the preparation method of the complex has the characteristics of simple synthesis route and high yield, thus overcoming the problem of complex preparation process of the same type of binuclear iron-based complex.

[0221] In addition, the binuclear iron-based complex provided by the present invention can not only cooperate with the co-catalyst to catalyze CHO / CO2 and CHO / PA polymerization reactions to obtain polycarbonate or polyester with high selectivity; it can also efficiently catalyze the polymerization of CHO and PA to generate polyether-polyester copolymers with different ester contents, flexibly adjust the ester content in the product, so that the polymerization product has different glass transition temperatures, thereby increasing its scope of use.

[0222] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A binuclear iron-based complex, characterized in that: The complex has a structure shown in formula (I) or formula (II): Formula (I); Formula (II); Wherein, in formula (I) and formula (II), each R1 is the same, each R2 is the same; R1 and R2 are each independently selected from methyl and tert-butyl; THF means tetrahydrofuran.

2. A method for preparing the binuclear iron-based complex according to claim 1, characterized in that: The method comprises the following steps: (1) Under a protective gas atmosphere, in the presence of triethylamine and tetrahydrofuran, subjecting the compound represented by formula (A) to a first reflux reaction with 3,3'-dihydroxybenzidine or 3,3'-diamino-4,4'-dihydroxybiphenyl to obtain a ligand; (2) in the presence of an alkaline reagent and a first solvent, subjecting the iron salt and the ligand to a second reflux reaction to obtain the binuclear iron-based complex; Formula (A); Wherein, in formula (A), the definitions of R1 and R2 are the same as those in claim 1; The iron salt is selected from at least one of anhydrous ferric chloride and anhydrous ferric bromide, and the first solvent is selected from at least one of tetrahydrofuran and 1,4-dioxane.

3. The method according to claim 2, wherein: The conditions of the first reflux reaction include: temperature of 70-80° C., time of 5-10 h; and / or The conditions of the second reflux reaction include: temperature of 70-80° C. and time of 4-8 h.

4. The method according to claim 2 or 3, wherein: In step (1), the molar ratio of the 3,3'-dihydroxybenzidine, the compound represented by formula (A), and triethylamine is 1:3-5:3-5; the molar ratio of the 3,3'-diamino-4,4'-dihydroxybiphenyl, the compound represented by formula (A), and triethylamine is 1:3-5:3-5; and / or In step (2), the molar ratio of the iron salt, the ligand, and the alkaline reagent is 1:0.4-0.6:2-4.

5. A method for catalytically preparing polycarbonate, characterized in that: The method comprises the following steps: The reactor containing the binuclear iron-based complex and the catalyst promoter according to claim 1 is evacuated and replaced with protective gas, and then carbon dioxide is introduced into the reactor after adding cyclohexene oxide under the protection of the protective gas to carry out a first polymerization reaction. After the reaction is completed, the reaction solution is dissolved in a second solvent and precipitated in acidified methanol, and then separated and dried in sequence to obtain the polycarbonate; The catalyst promoter is selected from bis(triphenylphosphine)ammonium chloride.

6. The method according to claim 5, wherein: The molar ratio of the binuclear iron-based complex, the catalyst promoter and cyclohexene oxide is 1:0.5-4:1000-8000; and / or The protective gas is selected from at least one of carbon dioxide, argon and nitrogen; and / or The second solvent is selected from at least one of dichloromethane, chloroform, and 1,2-dichloroethane; and / or The conditions of the first polymerization reaction include: a reaction starting pressure of 0.1 MPa-6 MPa, a reaction temperature of 80-120° C., and a reaction time of 2-8 h.

7. The method according to claim 5 or 6, wherein: The catalyst promoter is selected from bis(triphenylphosphine)ammonium chloride; and / or The conditions of the first polymerization reaction include: a reaction starting pressure of 2 MPa-4 MPa, a reaction temperature of 90-120° C., and a reaction time of 3-8 h; and / or The molar ratio of the binuclear iron-based complex, the catalyst promoter and cyclohexene oxide is 1:1.5-2.5:1000-4000.

8. A method for catalyzing the polymerization of cyclohexene oxide and phthalic anhydride, characterized in that: The method comprises the following steps: The reactor containing the binuclear iron-based complex according to claim 1, phthalic anhydride and bis(triphenylphosphine)ammonium chloride is evacuated and replaced with protective gas, and under the protection of the protective gas, cyclohexane is added to carry out a second polymerization reaction. After the reaction is completed, the reaction liquid is dissolved with dichloromethane and precipitated in acidified methanol, and then separated and dried in sequence; The molar ratio of the binuclear iron-based complex, bis(triphenylphosphine)ammonium chloride, phthalic anhydride and cyclohexene oxide is 1:0-3:500-6000:5000-20000.

9. The method according to claim 8, wherein: The conditions of the second polymerization reaction include: reaction temperature of 80-100° C., and reaction time of 10-30 min.

10. The method according to claim 8 or 9, wherein: The molar ratio of the binuclear iron-based complex, bis(triphenylphosphine)ammonium chloride, phthalic anhydride and cyclohexene oxide is 1:0-2:1000-4000:5000-20000.

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