A method for hydrogenation degradation of polyester

Abstract

The present invention discloses a method for hydrogenation degradation of polyester. The method for hydrogenation degradation of polyester includes heating and reacting polyester, an additive, a pincer ruthenium catalyst, and an alkaline substance in a selected solvent in a hydrogen atmosphere to achieve the degradation of polyester. The pincer ruthenium catalyst includes a tridentate pincer ruthenium complex, which has the structure shown as follows: #imgabs0# wherein, R 1 , R 2 are respectively selected from alkyl groups, aryl groups and hydrogen containing C1-C 20 , etc., and R 3 , R 4 are respectively selected from hydrogen, alkyl groups containing C1-C 20 , aryl groups, etc. Compared with traditional methods, the method for hydrogenation degradation of polyester provided by the present invention has the advantages of high catalytic activity, mild reaction conditions, high yield, little environmental pollution, simple operation, easy industrialization, etc., and will have broad market application prospects in the future.

Description

Technical Field

[0001] The present invention relates to the application of a novel class of tridentate pincer ruthenium complexes in the hydrogenative degradation of polyesters and a method for the hydrogenative degradation of polyesters, belonging to the technical field of organic chemistry. Background Art

[0002] With the rapid development of human society, plastic products have brought countless conveniences to our clothing, food, housing, and transportation. However, at the same time, they have also brought a global environmental crisis. Discarded plastic waste can be seen everywhere and has become one of the main sources of environmental pollution because plastics themselves have a relatively stable structure and are difficult to decompose in the natural environment. Therefore, developing a new method for the efficient and green degradation of plastics can not only greatly alleviate environmental pollution problems but also "turn waste into treasure" and convert them into high-value-added chemicals, which will have important scientific significance and potential application value.

[0003] As an important class of plastics, polyesters mainly include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyarylates. Among them, PET products are the most common, with an annual global output of about 80 million tons, accounting for more than 20% of the total global polymers. Although the output of PET is large, the recovery rate is very low, and only about 30% of PET materials are recycled. At present, PET is mainly chemically degraded by high-temperature hydrolysis or alcoholysis, but there are problems such as harsh conditions, serious pollution, and high costs. Although the conditions of the biodegradation method are relatively mild, there are still limitations such as difficult product purification, long cycle, and high costs. Considering that hydrogen is a green energy source with high production and no pollution in the reaction, it is of great significance to use homogeneous catalysts for the hydrogenative degradation of PET. For homogeneous catalytic hydrogenolysis reactions, metal catalysts play a crucial role in the activity of the reaction. Metal catalysts include metal centers and ligands, and ligands have a significant regulatory effect on both the spatial and electronic effects of the metal center. Therefore, the design and synthesis of metal complex catalysts with appropriate skeletons are of great significance for degradation. Among them, pincer ruthenium complexes are a class of metal catalysts with high catalytic activity and selectivity and have been successfully applied to the hydrogenative degradation of PET. However, so far, there are only three reports, and there are problems such as few catalyst types, low catalytic efficiency, and harsh reaction conditions. Therefore, it is of great significance to develop a pincer ruthenium complex with a brand-new skeleton for the efficient and green degradation of polyesters, which can not only solve environmental pollution problems but also contribute to the renewable utilization of waste plastics and the development of a circular economy. Summary of the Invention

[0004] The main object of the present invention is to provide the application of a novel class of tridentate pincer ruthenium complexes in the hydrogenative degradation of polyesters and the corresponding method for the hydrogenative degradation of polyesters to improve the efficiency of the existing technology.

[0005] To achieve the above-mentioned invention object, the technical solutions adopted by the present invention include:

[0006] In some embodiments of the present invention, a novel tridentate pincer ruthenium complex is provided as an application of a metal catalyst in the hydrogenation degradation of polyesters. The novel tridentate pincer ruthenium complex has a structure shown in any one of formulas (II-1), (II-2), and (II-3):

[0007]

[0008] Wherein, R 1 , R 2 are each independently selected from any one or a combination of alkyl groups, aryl groups, and hydrogen containing C1-C 20 , and R 3 , R 4 are each independently selected from any one or a combination of hydrogen, alkyl groups containing C1-C 20 , and aryl groups.

[0009] In some embodiments of the present invention, a method for the hydrogenation degradation of polyesters is also provided, which includes:

[0010] In a hydrogen atmosphere, polyesters, optionally added additives, pincer ruthenium catalysts, and basic substances are heated and reacted in a selected solvent to achieve the degradation of polyesters;

[0011] The pincer ruthenium catalyst includes a novel tridentate pincer ruthenium complex, and the novel tridentate pincer ruthenium complex has a structure shown in any one of formulas (II-1), (II-2), and (II-3):

[0012]

[0013] Wherein, R 1 , R 2 are each independently selected from any one or a combination of alkyl groups, aryl groups, and hydrogen containing C1-C 20 , and R 3 , R 4 are each independently selected from any one or a combination of hydrogen, alkyl groups containing C1-C 20 , and aryl groups.

[0014] In some embodiments, the structural formula of the polyester is as follows:

[0015]

[0016] In the formula, R and R' are each independently selected from any one or a combination of aliphatic groups containing C1-C 40 and aryl groups containing C6-C 60 , and the value of n is 1 to 500.

[0017] Compared with the prior art, the present invention has at least the following advantages:

[0018] 1) The polyester degradation method provided by the present invention improves the disadvantages of the existing methods, such as low catalyst efficiency and harsh reaction conditions, and can efficiently degrade polyester under relatively mild conditions;

[0019] 2) The present invention proposes to use an additive to first cut large molecular ester fragments into small molecules and then hydrogenate them to improve the efficiency of polyester degradation;

[0020] 3) The preparation route of the metal pincer ruthenium catalyst used in the present invention is clear, which improves the operability of the present invention to a certain extent. Detailed implementation manners

[0021] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention through long-term research and a large number of practices. Specifically, in a hydrogen atmosphere, the synthesized tridentate pincer ruthenium catalyst with an NNP-type quinoline backbone is used for the hydrogenation degradation reaction of polyester (such as polyethylene terephthalate). The following will further explain the technical solution, its implementation process and principle, etc.

[0022] An aspect of an embodiment of the present invention provides an application of a novel tridentate pincer ruthenium complex as a metal catalyst in the hydrogenation degradation of polyester. The novel tridentate pincer ruthenium complex has a structure shown in any one of formulas (II-1), (II-2), and (II-3):

[0023]

[0024] Wherein, R 1 , R 2 are each independently selected from any one or a combination of alkyl groups, aryl groups, and hydrogen containing C1-C 20 , and R 3 , R 4 are each independently selected from any one or a combination of hydrogen, alkyl groups containing C1-C 20 , and aryl groups.

[0025] Furthermore, another aspect of an embodiment of the present invention also provides a method for hydrogenation degradation of polyester, which includes:

[0026] In a hydrogen atmosphere under a certain pressure, the polyester, an additive that can be selectively added or not added, a pincer ruthenium catalyst, and a basic substance in the reaction structural formula are heated and reacted in a selected solvent to achieve the degradation of polyester.

[0027] Among them, the pincer ruthenium catalyst includes the novel tridentate pincer ruthenium complex having the structure shown in any one of the foregoing formulas (II-1), (II-2), and (II-3).

[0028] In some embodiments, the structural formula of the polyester is as follows:

[0029]

[0030] In the formula, R and R′ are respectively selected from any one or more combinations of aliphatic groups containing C1-C 40 and aryl groups containing C6-C 60 , and the value of n is 1 to 500.

[0031] Furthermore, the polyester may preferably be polyethylene terephthalate, but is not limited thereto.

[0032] The present invention uses the foregoing pincer ruthenium catalyst to efficiently catalyze the degradation of the polyester shown by the following formula, and the reaction formula is as follows:

[0033]

[0034] In some more preferred specific embodiments, the reaction steps of the method for hydrogenation degradation of the polyester are specifically as follows:

[0035] In a glove box, add the foregoing pincer ruthenium catalyst, basic substance, and selected solvent to a reaction flask. After stirring, add the polyester (such as polyethylene terephthalate) and additive. Place the reaction flask in a high-pressure reactor and remove it from the glove box. Add hydrogen at a certain pressure to the autoclave and stir at a certain temperature for 1 to 120 hours. After the reaction is completed, monitor the content of the target product p-tolyl alcohol by GC.

[0036] In some preferred embodiments, the molar ratio of the polyester, pincer ruthenium catalyst, basic substance, and additive is 1:0.0001:0.0001:0 to 1:0.05:0.05:500.

[0037] In some preferred embodiments, the temperature of the heating reaction is 25 to 200 °C, and the reaction time is 1 to 120 h.

[0038] In some preferred embodiments, the pressure of the hydrogen atmosphere is 1 to 100 bar.

[0039] In some preferred embodiments, the additive includes any one or a combination of two or more of methanol, ethanol, isopropanol, n-propanol, n-butanol, benzyl alcohol, cyclohexylamine, n-propylamine, benzylamine, aniline, tert-butylamine, etc., but is not limited thereto. The present invention uses an additive to first cut the large molecular ester fragments into small molecules and then hydrogenate them to improve the efficiency of polyester degradation.

[0040] In some preferred embodiments, the basic substance includes any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, sodium hydride, potassium hydride, potassium ethoxide, potassium methoxide, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, etc., but is not limited thereto.

[0041] In some preferred embodiments, the selected solvent includes any one or a combination of two or more of tetrahydrofuran, toluene, n-hexane, methanol, ethanol, isopropanol, benzene, 1,4-dioxane, dimethyl sulfoxide, xylene, anisole, ethylene glycol dimethyl ether, mesitylene, etc., but is not limited thereto.

[0042] In some embodiments, the preparation method of the novel tridentate pincer ruthenium complex includes:

[0043] Providing a tridentate pincer ligand having a structure shown in any one of formulas (I-1), (I-2), and (I-3);

[0044]

[0045] wherein, R 1 , R 2 are each independently selected from any one or a combination of alkyl groups, aryl groups, and hydrogen containing C1-C 20 , and R 3 , R 4 are each independently selected from any one or a combination of hydrogen, alkyl groups containing C1-C 20 , and aryl groups;

[0046] Reacting the tridentate pincer ligand with a metal ruthenium catalyst precursor to efficiently prepare a novel class of tridentate pincer ruthenium complexes.

[0047] In some preferred embodiments, the metal ruthenium catalyst precursor includes RuH(CO)Cl(PPh3)3.

[0048] In some preferred embodiments, the preparation method includes: mixing the tridentate pincer ligand (shown in any one of formulas (I-1), (I-2), and (I-3)) and the metal ruthenium catalyst precursor in a fourth solvent, and heating and reacting to obtain a novel tridentate pincer ruthenium complex. Specifically, taking formula (I-1) as an example, the reaction process is as follows:

[0049]

[0050] Furthermore, the molar ratio of the tridentate pincer ligand to the metal ruthenium catalyst precursor is 1:2 to 10:1, preferably 1:1 to 3:1.

[0051] Further, the fourth solvent includes any one or a combination of two or more of tetrahydrofuran, toluene, benzene, dichloromethane, methanol, ethanol, isopropanol, ether, n - hexane, 1,4 - dioxane, etc., but is not limited thereto.

[0052] Further, the heating temperature is 25 - 150 °C, preferably 50 - 110 °C, and the reaction time is 12 - 36 h.

[0053] In some more preferred specific embodiments, the specific reaction steps included in the preparation method are as follows: Under a nitrogen atmosphere, a tridentate pincer ligand represented by any one of the structural formulas (I - 1), (I - 2), and (I - 3), a metal ruthenium catalyst precursor, and a fourth solvent are added to a reaction flask, and heated and reacted for 12 - 36 hours. After returning to room temperature, the target tridentate pincer ruthenium complex represented by any one of the structural formulas (II - 1), (II - 2), and (II - 3) is obtained through steps such as concentration, washing, centrifugation, and concentration.

[0054] As a preferred technical solution, the preparation method includes: dissolving the concentrated solution of the tridentate pincer ligand obtained in the previous step in a fourth solvent and transferring it into a reaction flask, adding a metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3, and heating to 25 - 150 °C for reaction for 12 - 36 hours. After the reaction is completed, the temperature is lowered to room temperature, the solvent is dried, the reaction flask is transferred into a glove box and washed with a solvent, centrifuged, and concentrated to obtain a light yellow solid, that is, a tridentate pincer ruthenium complex having a structure represented by any one of the structural formulas (II - 1), (II - 2), and (II - 3). Specifically, taking the tridentate pincer ruthenium complex represented by the structural formula (II - 1) as an example, its preparation reaction process is as follows:

[0055]

[0056] In some embodiments, the preparation method of the tridentate pincer ligand mainly includes: in a protective atmosphere, starting from 8 - aminoquinaldine, a series of tridentate pincer ligands with a new NNP - type quinaldine skeleton are efficiently synthesized through 3 - 4 steps.

[0057] In some preferred embodiments, the preparation method of the tridentate pincer ligand represented by any one of the structural formulas (I - 1), (I - 2), and (I - 3) includes:

[0058] In a protective atmosphere, a mixed reaction system containing 8 - aminoquinaldine, a halogen - containing compound (halogen is chlorine, bromine, iodine), a first base, and a first solvent is heated to 35 - 150 °C for reaction for 12 - 48 h to obtain a substituted 8 - aminoquinaldine;

[0059] Mix the substituted 8-aminoquinaldine with a second solvent, cool the temperature to -78 to -45 °C, add a second base, stir for 1 to 2 h, then add a phosphine chloride reagent, and subsequently heat to 40 to 150 °C for reaction for 6 to 48 h. After the reaction is completed, add a BH3·THF solution, stir for 2 to 12 h, and after post-treatment, obtain a tridentate pincer ligand having a structure shown in any one of formulas (VI-1), (VI-2), and (VI-3);

[0060] Under nitrogen protection, mix a tridentate pincer ligand having a structure shown in any one of formulas (VI-1), (VI-2), and (VI-3), an amine, and a third solvent, and heat to 30 to 150 °C for reaction for 12 to 24 h to obtain a tridentate pincer ligand having a structure shown in any one of formulas (I-1), (I-2), and (I-3).

[0061] Among them, the structure of the halogen-containing compound is shown in any one of formulas (III-1), (III-2), and (III-3):

[0062]

[0063] X is Cl, Br or I, R 3 、R 4 are each independently selected from hydrogen, an alkyl group containing C1-C 20 and any one or a combination of one or more of aryl groups.

[0064] Among them, the structure of the substituted 8-aminoquinaldine is shown in any one of formulas (IV-1), (IV-2), and (IV-3):

[0065]

[0066] The structure of the phosphine chloride reagent is shown in formula (V):

[0067] R 1 R 2 PCI.

[0068] (V)

[0069] The structure of the tridentate pincer ligand having a structure shown in any one of formulas (VI-1), (VI-2), and (VI-3) is:

[0070]

[0071] Among them, R 1 、R 2 in the above structural formulas are each independently selected from any one or a combination of one or more of an alkyl group containing C1-C 20 , aryl group and hydrogen, R 3 、R 4Selected from hydrogen, an alkyl group containing C1-C 20 or a combination of any one or more of aryl groups.

[0072] Specifically, the synthesis method of the tridentate pincer ligand with the structure shown in formula (VI-1) includes the following steps:

[0073] Synthesis method:

[0074]

[0075] Furthermore, when R 1 and R 2 are both selected from phenyl groups, the structural formula of the substituted 8-aminoquinaldine is:

[0076]

[0077] And its NMR characterization data are as follows: 1 H NMR(600MHz, CDCl3)δ7.89(d, J = 8.4Hz, 1H), 7.72-7.68(m, 4H), 7.46-7.43(m, 2H), 7.39-7.36(m, 4H), 7.30-7.24(m, 2H), 7.08(d, J = 7.8Hz, 1H), 6.72(d, J = 7.8Hz, 1H), 3.99(d, J = 12.6Hz, 2H), 3.37(t, J = 6.6Hz, 4H), 1.87-1.85(m, 4H), 1.32-0.80(m, 3H); 13 C NMR(151MHz, CDCl3)δ148.8(d, J C-P = 4.4Hz), 146.7, 140.3, 135.9, 132.6(d, J C-P = 9.5Hz), 131.2(d, J C-P = 2.1Hz), 129.2, 128.7(d, J C-P = 9.8Hz), 126.8, 122.7, 116.0, 110.6, 51.6, 37.7(d, J C-P = 30.6Hz), 25.5; 31 P NMR(243MHz, CDCl3): δ17.1(J = 68.0Hz).

[0078] Furthermore, when R 1 and R 2 are both selected from cyclohexyl groups, the structural formula of the substituted 8-aminoquinaldine is:

[0079]

[0080] And its NMR characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.97 (d, J = 8.4 Hz, 1H), 7.41 (d, J = 8.4 Hz, 1H), 7.33 (t, J = 7.8 Hz, 1H), 7.14 (d, J = 7.8 Hz, 1H), 6.81 (d, J = 7.2 Hz, 1H), 3.76 - 3.74 (m, 4H), 3.38 (d, J = 12.0 Hz, 2H), 2.04 - 2.00 (m, 4H), 1.91 - 1.75 (m, 10H), 1.68 - 1.67 (m, 2H), 1.47 - 1.40 (m, 2H), 1.37 - 1.29 (m, 2H), 1.26 - 1.16 (m, 6H), 0.53 - 0.33 (m, 3H); 13 C NMR (151 MHz, CDCl3) δ 150.8 (d, J C-P = 4.5 Hz), 146.7, 140.4, 136.0, 128.6, 126.6, 122.6, 116.3, 110.9, 52.0, 31.8, 31.6 (d, J C-P = 4.4 Hz), 31.4, 26.8 (d, J C-P = 10.0 Hz), 26.6, 25.8, 25.5; 31 P NMR (243 MHz, CDCl3): δ 27.7 (J = 77.5 Hz).

[0081] Furthermore, when R 1 and R 2 are respectively selected from tert-butyl groups, the structural formula of the substituted 8-aminoquinaldine is:

[0082]

[0083] And its NMR characterization data are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.97 (d, J = 8.4 Hz, 1H), 7.71 (d, J = 8.4 Hz, 1H), 7.33 (t, J = 7.8 Hz, 1H), 7.14 (d, J = 7.8 Hz, 1H), 6.81 (d, J = 7.8 Hz, 1H), 3.73 (t, J = 6.6 Hz, 4H), 3.52 (d, J = 12.6 Hz, 2H), 2.02 - 2.00 (m, 4H), 1.31 (d, J = 12.6 Hz, 18H), 0.98 - 0.39 (m, 3H); 1313C NMR (151 MHz, CDCl3) δ 152.0, 146.7, 140.2, 135.8, 128.6, 126.6, 123.0, 116.4, 110.8, 52.1, 32.9 (d, J C-P = 25.8 Hz), 30.2 (d, J C-P = 23.3 Hz), 28.1, 25.5; 31 31P NMR (243 MHz, CDCl3): δ 45.6 (J = 80.4 Hz).

[0084] In some more preferred specific embodiments, the specific reaction steps of the tridentate pincer ligand having the structure shown in formula (I-1) are as follows:

[0085] (1) Under nitrogen protection, 8-aminoquinaldine, a halogen-containing compound (halogen is chlorine, bromine, iodine) (such as dibromoalkane), a first base, and a first solvent are added to a reaction flask, and the temperature is raised to 35 - 150 °C for reaction for 12 - 48 hours. After cooling to room temperature, filtration is carried out, and column chromatography separation gives the substituted 8-aminoquinaldine (IV-1). Subsequently, the substituted 8-aminoquinaldine and a second solvent are added to the reaction flask, and the temperature is cooled to -78 to -45 °C. A second base is added, and after stirring for 1 - 2 hours, a phosphine chloride reagent is added. Subsequently, the temperature is raised to 40 - 150 °C for reaction for 6 - 48 hours. After the reaction is completed, a BH3·THF solution is added dropwise, and after stirring for 2 - 12 hours, the tridentate pincer ligand (VI-1) is obtained through post-treatment.

[0086] (2) Under nitrogen protection, the tridentate pincer ligand (VI-1), an amine, and a third solvent are added to a reaction flask, and heated to 30 - 150 °C for reaction for 12 - 24 hours. Subsequently, it is concentrated and washed with a solvent, filtered through diatomaceous earth and then concentrated to obtain the tridentate pincer ligand having the structure shown in formula (I-1), which is directly used for the next reaction.

[0087] In some preferred embodiments, in step (1), the molar ratio of the 8-aminoquinaldine, the halogen-containing compound to the first base is 1:1:1 - 1:5:10.

[0088] Furthermore, the molar ratio of the substituted 8-aminoquinaldine to the second base is 1:0.5 - 1:10.

[0089] Furthermore, the molar ratio of the substituted 8-aminoquinaldine to the phosphine chloride reagent is 1:0.5 - 1:10.

[0090] Further, in step (1), the first base includes any one or a combination of two or more of sodium hydroxide, sodium tert-butoxide, potassium tert-butoxide, potassium methoxide, potassium ethoxide, sodium methoxide, sodium ethoxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium hydride, potassium hydride, potassium phosphate, etc., but is not limited thereto.

[0091] Further, in step (1), the first solvent includes any one or a combination of two or more of N,N-dimethylformamide, diethyl ether, dichloromethane, methanol, ethanol, isopropanol, acetonitrile, 1,4-dioxane, acetone, tetrahydrofuran, toluene, etc., but is not limited thereto.

[0092] Further, in step (2), the second base includes any one or a combination of two or more of n-butyllithium, tert-butyllithium, sec-butyllithium, lithium diisopropylamide (LDA), sodium bis(trimethylsilyl)amide (NaHMDS), lithium bis(trimethylsilyl)amide (LiHMDS), potassium bis(trimethylsilyl)amide (KHMDS), potassium tert-butoxide, sodium tert-butoxide, sodium hydride, potassium hydride, etc., but is not limited thereto.

[0093] Further, in step (1), the second solvent includes any one or a combination of two or more of diethyl ether, tetrahydrofuran, methyl tert-butyl ether, toluene, n-hexane, and 1,4-dioxane, etc., but is not limited thereto.

[0094] Further, in step (2), the molar ratio of the tridentate pincer ligand having any one of the structures shown in formulas (VI-1), (VI-2), and (VI-3) to the amine is 1:1 to 1:20.

[0095] Further, in step (2), the amine includes any one or a combination of two or more of diethylamine, triethylamine, DABCO (1,4-Diazabicyclo[2.2.2]octane), aniline, benzylamine, etc., but is not limited thereto.

[0096] Further, in step (2), the third solvent includes any one or a combination of two or more of diethyl ether, tetrahydrofuran, methyl tert-butyl ether, toluene, xylene, n-hexane, and 1,4-dioxane, etc., but is not limited thereto.

[0097] The tridentate pincer ruthenium complex prepared by the present invention has a brand-new framework structure and shows excellent catalytic activity in the polyester hydrogenation degradation reaction through preliminary tests. This preparation method has mild conditions, simple operation, and is easy to industrialize. The obtained pincer ruthenium catalyst will have broad application prospects in the future.

[0098] In summary, the polyester degradation method provided by the present invention has the advantages of high catalytic activity, mild reaction conditions, high yield, little environmental pollution, simple operation, easy industrialization, etc. It overcomes the disadvantages of low catalyst efficiency and harsh reaction conditions in the previous methods, and can efficiently degrade polyester under relatively mild conditions, showing broad market application prospects in the future.

[0099] The technical solution of the present invention will be further explained and illustrated below in conjunction with several preferred embodiments. It is easy for those skilled in the art to understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0100] In the following embodiments, the experimental materials used can be purchased from conventional biochemical reagent companies without special instructions.

[0101] Example 1

[0102] Synthesis of tridentate pincer ruthenium complex 3b

[0103]

[0104] The specific steps are as follows:

[0105] Under nitrogen protection, 8-aminoquinaldine (15.8 g, 100 mmol), 1,4-dibromobutane (21.6 g, 100 mmol), K2CO3 (55.3 g, 400 mmol) and N,N-dimethylformamide (200 mL) were added to the reaction flask, and the temperature was raised to 100 °C and reacted for 8 hours. After cooling to room temperature, filtration was carried out, washed with water and extracted with ethyl acetate. The organic phases were combined, dried, concentrated and then distilled under reduced pressure to obtain a light yellow oil S-4 (13.5 g, yield 64%).

[0106] Under nitrogen protection, S-4 (2.1 g, 10.0 mmol) and THF (15 mL) were added to the reaction flask, cooled to -78 °C, n-butyllithium (10.0 mmol) was added, then the temperature was raised to room temperature and stirred for 1 hour, then cooled to -78 °C again, and a THF (5 mL) solution of diphenylphosphine chloride (2.2 g, 10.0 mmol) was added, and then the temperature was raised to 40 °C and reacted for 12 hours. Subsequently, the reaction system was cooled to 0 °C, and BH3·THF solution (15 mmol) was slowly added dropwise. After the addition was completed, the temperature was raised to 40 °C and stirred for 12 hours. After the reaction was completed, a small amount of H2O was added to quench the excess borane. Ethyl acetate was added for extraction, the organic phases were combined, dried over anhydrous sodium sulfate, concentrated, and column chromatography was carried out to obtain a yellow solid S-5 (2.5 g, yield 61%).

[0107] Under nitrogen protection, S-5 (246.0 mg, 0.6 mmol), DABCO (134.4 mg, 1.2 mmol) and toluene (6 mL) were added to a reaction flask, and the mixture was heated to 50 °C and reacted for 12 hours. Subsequently, after concentration, n-hexane was added, and the mixture was filtered through diatomaceous earth and then concentrated, and directly used for the next reaction. The concentrated solution from the previous step was dissolved in THF (6 mL) and transferred to a reaction flask. The metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3 (476 mg, 0.5 mmol) was added, and the mixture was heated to 70 °C and reacted for 12 hours. After the reaction was completed, the temperature was cooled to room temperature, the solvent was dried under reduced pressure, the reaction flask was transferred into a glove box, and washed with ether, centrifuged, and concentrated to obtain a light yellow solid 3b (260.8 mg, yield 93%), namely the novel tridentate pincer ruthenium complex.

[0108] The inventor of this case also characterized the light yellow solid 3b by NMR, and the data are as follows: 1 H NMR (600 MHz, DMSO-d6) δ 8.56 (d, J = 8.4 Hz, 1H), 8.27 (d, J = 7.8 Hz, 1H), 8.02 (d, J = 7.8 Hz, 1H), 7.91 (d, J = 8.4 Hz, 1H), 7.88 - 7.85 (m, 2H), 7.74 - 7.71 (m, 1H), 7.55 - 7.52 (m, 2H), 7.47 - 7.45 (m, 3H), 7.41 - 7.37 (m, 3H), 4.82 - 4.77 (m, 1H), 4.60 - 4.58 (m, 1H), 4.49 - 4.44 (m, 1H), 3.77 (t, J = 8.4 Hz, 1H), 3.60 - 3.55 (m, 1H), 3.18 - 3.13 (m, 1H), 2.46 - 2.39 (m, 2H), 2.23 - 2.13 (m, 2H), -14.29 (d, J = 26.4 Hz, 1H); 13 C NMR (151 MHz, DMSO-d6) δ 208.3 (d, J C-P = 16.2 Hz), 160.43 (d, J C-P = 5.9 Hz), 151.9, 144.7, 140.4, 140.0, 137.2, 134.2, 133.9, 133.1 (d, J C-P = 10.9 Hz), 131.0 (d, J C-P = 10.9 Hz), 130.1, 129.6, 129.0, 128.8 (d, J C-P = 6.8 Hz), 128.3 (d, J C-P = 10.0 Hz), 128.0 (d, J C-P = 10.4 Hz), 127.5 (d, JC-P = 15.3 Hz), 127.0, 125.8, 121.3 (d, J C-P = 11.0 Hz), 71.6, 61.8, 44.74 (d, J C-P = 28.4 Hz), 24.17 (d, J C-P = 6.5 Hz); 31 P NMR (243 MHz, DMSO-d6) δ 73.15.

[0109] Example 2

[0110] This example is different from Example 1 in that: diphenylphosphine chloride is replaced by di-tert-butylphosphine chloride. The structure of the obtained product is:

[0111]

[0112] The inventor of this case also carried out NMR characterization on this product, and the data are as follows: 1 H NMR (600 MHz, CD2Cl2 / CD3OD, V / V = 2∶1) δ 8.23 - 8.18 (m,, 1H), 7.87 - 7.74 (m, 2H), 7.64 - 7.53 (m, 2H), 4.34 - 4.20 (m, 2H), 3.85 - 3.80 (m, 1H), 3.61 - 3.57 (m, 1H), 3.23 - 3.15 (m, 2H), 2.47 - 2.41 (m, 2H), 2.11 (d, J = 10.8 Hz, 2H), 1.32 - 1.13 (m, 18H), -16.59 (s, 1H); 13 C NMR (151 MHz, CD2Cl2 / CD3OD, V / V = 2∶1) δ 209.3, 163.6, 153.6, 147.2, 138.8, 129.4, 128.6, 128.2, 126.0, 122.2, 74.6, 62.0, 39.1, 38.3 (m), 30.8, 25.9, 25.5; 31 P NMR (243 MHz, CD2Cl2 / CD3OD, V / V = 2∶1) δ 111.99.

[0113] Example 3

[0114] This example is different from Example 1 in that: diphenylphosphine chloride is replaced by dicyclohexylphosphine chloride. The structure of the obtained product is:

[0115]

[0116] The inventor of this case also carried out NMR characterization on this product, and the data are as follows: 11H NMR (600 MHz, CD2Cl2 / CD3OD, V / V = 2:1) δ 8.18 (d, J = 9.0 Hz, 1H), 7.88 (d, J = 7.8 Hz, 1H), 7.75 (d, J = 7.8 Hz, 1H), 7.57 - 7.53 (m, 2H), 4.36 (s, 2H), 3.93 (s, 1H), 3.73 - 3.62 (m, 2H), 3.50 - 3.48 (m, 1H), 3.00 (s, 1H), 2.52 - 2.46 (m, 2H), 2.34 (s, 1H), 2.15 - 2.10 (m, 2H), 1.97 (d, J = 12.0 Hz, 1H), 1.82 - 1.63 (m, 6H), 1.57 - 1.53 (m, 2H), 1.48 - 1.36 (m, 2H), 1.27 - 1.17 (m, 8H), 1.09 - 1.05 (m, 1H), -15.68 (s, 1H); 13 13C NMR (151 MHz, CD2Cl2 / CD3OD, V / V = 2∶1) δ 209.3, 163.3, 154.0, 147.2, 138.5, 129.4, 128.6, 128.4, 126.7, 122.30 (d, J C-P = 9.1 Hz), 73.2, 64.5, 42.3, 40.8 (d, J C-P = 24.5 Hz), 37.8 (d, J C-P = 30.5 Hz), 31.9, 30.6 (d, J C-P = 3.2 Hz), 29.8 (d, J C-P = 4.4 Hz), 29.2, 29.1, 29.0, 28.7 (d, J C-P = 9.4 Hz), 27.8 (m), 27.4, 26.3, 25.8; 31 31P NMR (243 MHz, CD2Cl2 / CD3OD, V / V = 2:1) δ 91.82.

[0117] Example 4

[0118]

[0119] Under nitrogen protection, 8-aminoquinaldine (100 mmol), 1,4-dibromobutane (200 mmol), K2CO3 (400 mmol) and N,N-dimethylformamide (200 mL) were added to a reaction flask, and the temperature was raised to 50 °C and reacted for 24 hours. After cooling to room temperature, filtration was carried out, washed with water and extracted with ethyl acetate. The organic phases were combined, dried, concentrated and then distilled under reduced pressure to obtain a light yellow oily substance S-4.

[0120] Under nitrogen protection, S-4 (2.1 g, 10.0 mmol) and THF (15 mL) were added to a reaction flask, cooled to -78 °C, n-butyllithium (5.0 mmol) was added, and then the temperature was raised to room temperature and stirred for 2 hours. Then the temperature was lowered to -78 °C again, and a THF (5 mL) solution of diphenylphosphine chloride (5.0 mmol) was added. Subsequently, the temperature was raised to 80 °C and reacted for 24 hours. Then the reaction system was cooled to 0 °C, and a BH3·THF solution (15 mmol) was slowly added dropwise. After the addition was completed, the temperature was raised to 40 °C and stirred for 12 hours. After the reaction was completed, a small amount of H2O was added to quench the excess borane. Ethyl acetate was added for extraction, the organic phases were combined, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography to obtain a yellow solid S-5.

[0121] Under nitrogen protection, S-5 (0.6 mmol), DABCO (1.2 mmol) and toluene (6 mL) were added to a reaction flask, heated to 50 °C and reacted for 12 hours. Then it was concentrated, n-hexane was added, filtered through diatomaceous earth and concentrated, and directly used for the next reaction. The concentrated solution from the previous step was dissolved in THF (6 mL) and transferred to a reaction flask. A metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3 (0.2 mmol) was added, and the mixture was heated to 80 °C and reacted for 12 hours. After the reaction was completed, the temperature was lowered to room temperature, the solvent was dried under reduced pressure, the reaction flask was transferred into a glove box, washed with ether, centrifuged, and concentrated to obtain a light yellow solid 3b, namely the novel tridentate pincer ruthenium complex.

[0122] Example 5

[0123]

[0124] Under nitrogen protection, 8-aminoquinaldine (100 mmol), 1,4-dibromobutane (500 mmol), K2CO3 (1000 mmol) and N,N-dimethylformamide (200 mL) were added to a reaction flask, and the temperature was raised to 100 °C and reacted for 36 hours. After cooling to room temperature, it was filtered by suction, washed with water and extracted with ethyl acetate. The organic phases were combined, dried, concentrated, and distilled under reduced pressure to obtain a light yellow oily substance S-4.

[0125] Under nitrogen protection, S-4 (10.0 mmol) and THF (15 mL) were added to a reaction flask, cooled to -78 °C, n-butyllithium (100.0 mmol) was added, and then the mixture was stirred at room temperature for 2 hours. After that, it was cooled to -78 °C again, and a THF (20 mL) solution of diphenylphosphine chloride (100.0 mmol) was added. Subsequently, the temperature was raised to 100 °C and the reaction was carried out for 48 hours. Then the reaction system was cooled to 0 °C, and a BH3·THF solution (15 mmol) was slowly added dropwise. After the addition was completed, the temperature was raised to 40 °C and the mixture was stirred for 10 hours. After the reaction was completed, a small amount of H2O was added to quench the excess borane. Ethyl acetate was added for extraction, the organic phases were combined, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography to obtain a yellow solid S-5.

[0126] Under nitrogen protection, S-5 (1.0 mmol), DABCO (2.0 mmol) and toluene (6 mL) were added to a reaction flask, and the mixture was heated to 100 °C and reacted for 24 hours. Subsequently, after concentration, n-hexane was added, and after filtration through diatomaceous earth, it was concentrated and directly used for the next reaction. The concentrated solution from the previous step was dissolved in THF (6 mL) and transferred to a reaction flask. A metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3 (0.2 mmol) was added, and the mixture was heated to 80 °C and reacted for 12 hours. After the reaction was completed, the temperature was cooled to room temperature, the solvent was evaporated, the reaction flask was transferred into a glove box, washed with ether, centrifuged, and concentrated to obtain a light yellow solid 3b, namely the novel tridentate pincer ruthenium complex.

[0127] Example 6

[0128]

[0129] Under nitrogen protection, 8-aminoquinaldine (100 mmol), 1,4-dibromobutane (300 mmol), K2CO3 (500 mmol) and N,N-dimethylformamide (200 mL) were added to a reaction flask, and the temperature was raised to 100 °C and the reaction was carried out for 36 hours. After cooling to room temperature, it was filtered by suction, washed with water and extracted with ethyl acetate. The organic phases were combined, dried, concentrated and distilled under reduced pressure to obtain a light yellow oily substance S-4.

[0130] Under nitrogen protection, S-4 (2.1 g, 10.0 mmol) and THF (15 mL) were added to a reaction flask, cooled to -78 °C, n-butyllithium (100.0 mmol) was added, then the temperature was raised to room temperature and stirred for 2 hours. After that, the temperature was lowered to -78 °C again, and a THF (30 mL) solution of diphenylphosphine chloride (100.0 mmol) was added. Subsequently, the temperature was raised to 80 °C and reacted for 48 hours. Then the reaction system was cooled to 0 °C, and BH3·THF solution (15 mmol) was slowly added dropwise. After the addition was completed, the temperature was raised to 40 °C and stirred for 12 hours. After the reaction was completed, a small amount of H2O was added to quench the excess borane. Ethyl acetate was added for extraction, the organic phases were combined, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography to obtain a yellow solid S-5.

[0131] Under nitrogen protection, S-5 (0.4 mmol), DABCO (8.0 mmol) and toluene (10 mL) were added to a reaction flask, heated to 100 °C and reacted for 12 hours. Then it was concentrated, n-hexane was added, filtered through diatomaceous earth and concentrated, and directly used for the next reaction. The concentrated solution from the previous step was dissolved in THF (10 mL) and transferred to a reaction flask. The metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3 (0.2 mmol) was added, and the temperature was raised to 50 °C and reacted for 36 hours. After the reaction was completed, the temperature was lowered to room temperature, the solvent was evaporated, the reaction flask was transferred into a glove box, washed with ether, centrifuged, and concentrated to obtain a light yellow solid 3b, namely the novel tridentate pincer ruthenium complex.

[0132] Example 7

[0133] Under nitrogen protection, 8-aminoquinoline (100 mmol), 1,4-dibromobutane (100 mmol), potassium phosphate (100 mmol) and tetrahydrofuran (200 mL) were added to a reaction flask, and the temperature was raised to 35 °C and reacted for 48 hours. After cooling to room temperature, it was filtered by suction, washed with water and extracted with ethyl acetate. The organic phases were combined, dried, concentrated and distilled under reduced pressure to obtain a light yellow oil.

[0134] Under nitrogen protection, the light yellow oil product (10.0 mmol) and THF (15 mL) were added to a reaction flask, cooled to -45 °C, lithium diisopropylamide (100.0 mmol) was added, then the temperature was raised to room temperature and stirred for 2 hours. After that, the temperature was lowered to -45 °C again, and a THF (30 mL) solution of di-tert-butylphosphine chloride (100.0 mmol) was added. Subsequently, the temperature was raised to 50 °C and reacted for 48 hours. Then the reaction system was cooled to 0 °C, and BH3·THF solution (15 mmol) was slowly added dropwise. After the addition was completed, the temperature was raised to 40 °C and stirred for 2 hours. After the reaction was completed, a small amount of H2O was added to quench the excess borane. Ethyl acetate was added for extraction, the organic phases were combined, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography to obtain a yellow solid.

[0135] Under nitrogen protection, the yellow solid (0.4 mmol), diethylamine (0.4 mmol) and tetrahydrofuran (10 mL) were added to a reaction flask, and the mixture was heated to 30 °C and reacted for 24 hours. Subsequently, after concentration, n-hexane was added, and the mixture was filtered through diatomaceous earth and then concentrated, and directly used for the next reaction. The concentrated solution from the previous step was dissolved in toluene (10 mL) and transferred into a reaction flask. The metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3 (0.8 mmol) was added, and the mixture was heated to 150 °C and reacted for 24 hours. After the reaction was completed, the temperature was lowered to room temperature, the solvent was dried under reduced pressure, the reaction flask was transferred into a glove box, washed with ether, centrifuged, and concentrated to obtain a light yellow solid, namely the novel tridentate pincer ruthenium complex.

[0136] Example 8

[0137] Under nitrogen protection, 8-aminoquinoline (100 mmol), 1,4-dibromobutane (200 mmol), sodium hydroxide (500 mmol) and acetone (200 mL) were added to a reaction flask, and the temperature was raised to 150 °C and reacted for 12 hours. After cooling to room temperature, the mixture was filtered by suction, washed with water and extracted with ethyl acetate. The organic phases were combined, dried, concentrated and then distilled under reduced pressure to obtain a light yellow oil.

[0138] Under nitrogen protection, the light yellow oil product (10.0 mmol) and THF (15 mL) were added to a reaction flask, and the temperature was lowered to -68 °C. Lithium bis(trimethylsilyl)amide (50.0 mmol) was added. Subsequently, the temperature was raised to room temperature and stirred for 2 hours, then the temperature was lowered to -68 °C again, and a THF (30 mL) solution of dicyclohexylphosphine chloride (80.0 mmol) was added. Subsequently, the temperature was raised to 150 °C and reacted for 6 hours. Then the reaction system was cooled to 0 °C, and a BH3·THF solution (15 mmol) was slowly added dropwise. After the addition was completed, the temperature was raised to 40 °C and stirred for 10 hours. After the reaction was completed, a small amount of H2O was added to quench the excess borane. Ethyl acetate was added for extraction, the organic phases were combined, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography to obtain a yellow solid.

[0139] Under nitrogen protection, the yellow solid (0.4 mmol), benzylamine (4 mmol) and n-hexane (10 mL) were added to a reaction flask, and the mixture was heated to 150 °C and reacted for 20 hours. Subsequently, after concentration, n-hexane was added, and the mixture was filtered through diatomaceous earth and then concentrated, and directly used for the next reaction. The concentrated solution from the previous step was dissolved in dichloromethane (10 mL) and transferred into a reaction flask. The metal ruthenium catalyst precursor RuH(CO)Cl(PPh3)3 (0.04 mmol) was added, and the reaction was carried out at 25 °C for 36 hours. After the reaction was completed, the temperature was lowered to room temperature, the solvent was dried under reduced pressure, the reaction flask was transferred into a glove box, washed with ether, centrifuged, and concentrated to obtain a light yellow solid, namely the novel tridentate pincer ruthenium complex.

[0140] Example 9

[0141] This example is different from Example 8 in that 1,4-dibromobutane is replaced by bromoethane, and the structural formula of the finally obtained tridentate pincer ruthenium complex is:

[0142]

[0143] The bromoethane in this example can also be replaced by iodomethane, bromodecane, C 20 H 41 Br, etc., and similar effects can also be achieved.

[0144] Example 10

[0145] This example is different from Example 8 in that 1,4-dibromobutane is replaced by 2,2′-dibromo diethyl ether, and the structural formula of the finally obtained tridentate pincer ruthenium complex is:

[0146]

[0147] Example 11

[0148] This example is different from Example 8 in that 1,4-dibromobutane is replaced by bromobenzene, and the structural formula of the finally obtained tridentate pincer ruthenium complex is:

[0149]

[0150] Application Example 1

[0151] Using the product obtained in Example 3 as a ruthenium catalyst to carry out hydrogenation degradation of polyester:

[0152]

[0153] In a glove box, ruthenium catalyst (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to a reaction flask. After stirring for 10 minutes, PET (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 4 days. After the reaction was completed, internal standard n-dodecane was added, and through GC monitoring, the yield of the product p-xylene glycol 1 was 88%.

[0154] Application Example 2

[0155] Using the product obtained in Example 3 as a ruthenium catalyst to carry out hydrogenation degradation of polyester:

[0156]

[0157] In a glove box, ruthenium catalyst (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to a reaction flask. After stirring for 10 minutes, PBT (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 120 h. After the reaction was completed, internal standard n-dodecane was added, and by GC monitoring, the yield of the product p-xylene dimethanol 1 was 85%.

[0158] Application Example 3

[0159] In a glove box, ruthenium catalyst (1.0 mol%), potassium tert-butoxide (6.0 mol%) and methanol (1.5 mL) were added to a reaction flask. After stirring for 10 minutes, PET (0.2 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 5 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 4 days. After the reaction was completed, internal standard n-dodecane was added, and by GC monitoring, the yield of the product p-xylene dimethanol 1 was 86%.

[0160] In addition, the inventors of this case also tested the cases where R and R′ are respectively selected from aliphatic groups with C1, aliphatic groups with C4, R taking aliphatic groups with C 10 aliphatic groups, C 40 aliphatic groups, aryl groups containing C6, aryl groups containing C 20 aryl groups, aryl groups containing C 60 aryl groups, etc. The results were similar to those of Application Examples 1-3.

[0161] Application Example 4

[0162] In a glove box, ruthenium catalyst (5.0 mol%), sodium tert-butoxide (5.0 mol%) and benzene (2.5 mL) were added to a reaction flask. After stirring for 10 minutes, PET (0.2 mmol) was added, and isopropanol (10 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 80 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 3 days. After the reaction was completed, internal standard n-dodecane was added, and by GC monitoring, the target product p-xylene dimethanol 1 was obtained.

[0163] Application Example 5

[0164] In the glove box, ruthenium catalyst (0.01 mol%), sodium ethoxide (0.01 mol%) and tetrahydrofuran (1.5 mL) were added to the reaction flask. After stirring for 10 minutes, PET (0.2 mmol) was added, and aniline (1 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 100 bar of hydrogen was added to the autoclave, and the reaction was carried out at 25 °C for 4 days. After the reaction was completed, internal standard n-dodecane was added, and the target product p-xylene glycol 1 was obtained by GC monitoring.

[0165] Application Example 6

[0166] In the glove box, ruthenium catalyst (1.0 mol%), potassium phosphate (3.0 mol%) and 1,4-dioxane (1.5 mL) were added to the reaction flask. After stirring for 10 minutes, PET (0.2 mmol) was added, and tert-butylamine (100 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 1 bar of hydrogen was added to the autoclave, and the reaction was carried out at 200 °C for 1 h. After the reaction was completed, internal standard n-dodecane was added, and the target product p-xylene glycol 1 was obtained by GC monitoring.

[0167] Application Example 7

[0168] In the glove box, ruthenium catalyst (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to the reaction flask. After stirring for 10 minutes, shredded Coke bottle (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 4 days. After the reaction was completed, internal standard n-dodecane was added, and the target product p-xylene glycol 1 was obtained by GC monitoring.

[0169] Application Example 8

[0170] In the glove box, ruthenium catalyst (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to the reaction flask. After stirring for 10 minutes, shredded mineral water bottle (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 4 days. After the reaction was completed, internal standard n-dodecane was added, and the target product p-xylene glycol 1 was obtained by GC monitoring.

[0171] Application Example 9

[0172] In a glove box, ruthenium catalyst (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added to a reaction flask. After stirring for 10 minutes, PET film (0.2 mmol) was added, and methanol (0.2 mmol) was added. The reaction flask was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80 °C for 4 days. After the reaction was completed, internal standard n-dodecane was added, and the target product p-xylene glycol 1 was obtained by GC monitoring.

[0173] Furthermore, the inventors of this case also used the products obtained in the remaining examples as ruthenium catalysts and carried out hydrogenation degradation reactions on PET. The results were similar to those of Application Example 1.

[0174] Through the above examples and application examples, it can be found that the tridentate pincer ruthenium complex obtained by the above technical solution of the present invention has a novel structure, a brand-new skeleton structure, efficient reactions, can achieve the hydrogenation degradation of polyesters, and has good application prospects.

[0175] It should be understood that the above examples are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for hydrogenation degradation of polyester, characterized in that, Comprising: In a hydrogen atmosphere, a polyester, optionally added or not added additives, a pincer ruthenium catalyst, and an alkaline substance are heated and reacted in a selected solvent to achieve the degradation of the polyester; The pincer ruthenium catalyst comprises a novel tridentate pincer ruthenium complex, and the novel tridentate pincer ruthenium complex has a structure shown in any one of formulas (II-1), (II-2), and (II-3): Among them, R 1 and R 2 are each independently selected from any one or a combination of alkyl groups, aryl groups, and hydrogen containing C1-C 20 , and R 3 and R 4 are each independently selected from any one or a combination of hydrogen, alkyl groups containing C1-C 20 , and aryl groups; The additives are selected from any one or a combination of two or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, cyclohexylamine, n-propylamine, benzylamine, aniline, and tert-butylamine.

2. The polyester hydrogenation degradation method according to claim 1, wherein The structural formula of the polyester is as follows: wherein R and R' are each independently selected from any one or more combinations of aliphatic groups containing C1-C 40 and aryl groups containing C6-C 60 , and n ranges from 1 to 500.

3. The polyester hydrogenation degradation method according to claim 1, wherein: The molar ratio of the polyester, pincer ruthenium catalyst, alkaline substance to the additive is 1:0.0001:0.0001:0 to 1:0.05:0.05:

500.

4. The polyester hydrogenation degradation method according to claim 1, characterized in that: The temperature of the heating reaction is 25 to 200 °C, and the reaction time is 1 to 120 h.

5. The polyester hydrogenation degradation method according to claim 1, wherein: The pressure of the hydrogen atmosphere is 1 to 100 bar.

6. The polyester hydrogenation degradation method according to claim 1, characterized in that: The alkaline substance includes any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, sodium hydride, potassium hydride, potassium ethoxide, potassium methoxide, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, and lithium bis(trimethylsilyl)amide.

7. The polyester hydrogenation degradation method according to claim 1, characterized in that: The selected solvent includes any one or a combination of two or more of tetrahydrofuran, toluene, n-hexane, methanol, ethanol, isopropanol, benzene, n-propanol, 1,4-dioxane, dimethyl sulfoxide, xylene, anisole, ethylene glycol dimethyl ether, and mesitylene.

8. The polyester hydrogenation degradation method according to claim 1, characterized in that The preparation method of the novel tridentate pincer ruthenium complex includes: providing a novel tridentate pincer ligand having a structure shown in any one of formulas (I-1), (I-2), and (I-3); Among them, R 1 and R 2 are each independently selected from any one or a combination of alkyl groups, aryl groups, and hydrogen containing C1-C 20 , and R 3 and R 4 are each independently selected from any one or a combination of hydrogen, alkyl groups containing C1-C 20 , and aryl groups; Reacting the novel tridentate pincer ligand with a metal ruthenium catalyst precursor to obtain a tridentate pincer ruthenium complex; The metal ruthenium catalyst precursor includes RuH(CO)Cl(PPh3)3.

9. The polyester hydrogenation degradation method according to claim 8, wherein, The preparation method of the novel tridentate pincer ligand includes: In a protective atmosphere, a mixed reaction system containing 8-aminoquinoline, a halogen-containing compound, a first base, and a first solvent is heated to 35 to 150 °C and reacted for 12 to 48 h to obtain a substituted 8-aminoquinoline; Mixing the substituted 8-aminoquinoline with a second solvent, cooling to -78 to -45 °C, adding a second base, stirring for 1 to 2 h, adding a phosphine chloride reagent, then heating to 40 to 150 °C and reacting for 6 to 48 h. After the reaction, a BH3·THF solution is added, stirred for 2 to 12 h, and after post-treatment, a tridentate pincer ligand having a structure shown in any one of formulas (VI-1), (VI-2), and (VI-3) is obtained; Under nitrogen protection, a tridentate pincer ligand having a structure shown in any one of formulas (VI-1), (VI-2), and (VI-3), an amine, and a third solvent are mixed and heated to 30 to 150 °C and reacted for 12 to 24 h to obtain a novel tridentate pincer ligand having a structure shown in any one of formulas (I-1), (I-2), and (I-3); Among them, the structure of the halogen-containing compound is shown as any one of formulas (Ⅲ-1), (Ⅲ-2), and (Ⅲ-3): Among them, X is Cl, Br or I; The structure of the substituted 8-aminoquinoline is shown as any one of formulas (Ⅳ-1), (Ⅳ-2), and (Ⅳ-3): The structure of the phosphine chloride reagent is shown as formula (Ⅴ): Among them, R 1 , R 2 are respectively selected from any one or a combination of more than one of alkyl, aryl and hydrogen containing C1-C 20 , and R 3 , R 4 are respectively selected from any one or a combination of more than one of hydrogen, alkyl containing C1-C 20 and aryl.

10. The polyester hydrogenation degradation method according to claim 9, characterized in that: The molar ratio of the 8-aminoquinoline, the halogen-containing compound to the first base is 1:1:1 to 1:5:

10.

11. The polyester hydrogenation degradation method according to claim 9, wherein: The molar ratio of the substituted 8-aminoquinoline to the second base is 1:0.5 to 1:

10.

12. The polyester hydrogenation degradation method according to claim 9, characterized in that: The molar ratio of the substituted 8-aminoquinoline to the phosphine chloride reagent is 1:0.5 to 1:

10.

13. The polyester hydrogenation degradation method according to claim 9, characterized in that: The first base includes any one or a combination of two or more of sodium hydroxide, sodium tert-butoxide, potassium tert-butoxide, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium hydride, potassium hydride, and potassium phosphate.

14. The polyester hydrogenation degradation method according to claim 9, characterized in that: The first solvent includes any one or a combination of two or more of N,N-dimethylformamide, diethyl ether, dichloromethane, methanol, ethanol, isopropanol, acetonitrile, 1,4-dioxane, acetone, tetrahydrofuran, and toluene.

15. The polyester hydrogenation degradation method according to claim 9, characterized in that: The second base includes any one or a combination of two or more of n-butyllithium, tert-butyllithium, sec-butyllithium, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, potassium bis(trimethylsilyl)amide, potassium tert-butoxide, sodium tert-butoxide, sodium hydride, and potassium hydride.

16. The polyester hydrogenation degradation method according to claim 9, characterized in that: The second solvent includes any one or a combination of two or more of diethyl ether, tetrahydrofuran, methyl tert-butyl ether, toluene, n-hexane, and 1,4-dioxane.

17. The polyester hydrogenation degradation method according to claim 9, characterized in that: The molar ratio of the tridentate pincer ligand having a structure shown as any one of formulas (Ⅵ-1), (Ⅵ-2), and (Ⅵ-3) to the amine is 1:1 to 1:

20.

18. The polyester hydrogenation degradation method according to claim 9, characterized in that: The amine includes any one or a combination of two or more of diethylamine, triethylamine, DABCO, aniline, and benzylamine.

19. The polyester hydrogenation degradation method according to claim 9, characterized in that: The third solvent includes any one or a combination of two or more of diethyl ether, tetrahydrofuran, methyl tert-butyl ether, toluene, xylene, n-hexane, and 1,4-dioxane.

20. The polyester hydrogenation degradation method according to claim 9, characterized in that, Comprising: Mixing the novel tridentate pincer ligand and the metal ruthenium catalyst precursor in a fourth solvent and heating for reaction to obtain a novel tridentate pincer ruthenium complex.

21. The polyester hydrogenation degradation method according to claim 20, wherein The molar ratio of the novel tridentate pincer ligand to the metal ruthenium catalyst precursor is 1:2 to 10:

1.

22. The polyester hydrogenation degradation method according to claim 21, wherein The molar ratio of the novel tridentate pincer ligand to the metal ruthenium catalyst precursor is 1:1 to 3:

1.

23. The polyester hydrogenation degradation method according to claim 20, wherein: The fourth solvent includes any one or a combination of two or more of tetrahydrofuran, toluene, benzene, dichloromethane, methanol, ethanol, isopropanol, diethyl ether, n-hexane, and 1,4-dioxane.

24. The polyester hydrogenation degradation method according to claim 20, wherein: The temperature of the heating is 25 to 150 °C, and the reaction time is 12 to 36 h.

25. The polyester hydrogenation degradation method according to claim 24, wherein: The temperature of the heating is 50 to 110 °C.

26. Application of a novel tridentate pincer ruthenium complex as a metal catalyst in the hydrogenation degradation of polyesters. The novel tridentate pincer ruthenium complex has a structure shown as any one of formulas (II-1), (II-2), and (II-3): Among them, R 1 and R 2 are each independently selected from any one or more combinations of an alkyl group, an aryl group, and hydrogen containing C1-C 20 , and R 3 and R 4 are each independently selected from any one or more combinations of hydrogen, an alkyl group containing C1-C 20 .

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