Binuclear sulfonamide modified beta-ketimine zinc complex as well as synthesis method and application thereof

Abstract

The invention belongs to the field of preparation and application of metal complex catalysts, and discloses a binuclear sulfonamide modified beta-ketimine zinc complex as well as a synthesis method and application thereof. The binuclear sulfonamide-modified beta-ketimine zinc complex is applied to catalysis of epsilon-caprolactone ring-opening polymerization, the binuclear sulfonamide-modified beta-ketimine zinc complex is used as a catalyst, epsilon-caprolactone is used as a raw material, and the binuclear sulfonamide-modified beta-ketimine zinc complex is subjected to ring-opening polymerization in the absence of a solvent at 110 DEG C in the absence of water, oxygen and inert gas. Epsilon-caprolactone ring opening polymerization can be catalyzed to prepare polycaprolactone without the participation of a cocatalyst. The catalyst is low in toxicity, simple in preparation method, novel in structure and high in catalytic activity, and the dosage of the catalyst is low in the catalysis process.

Description

Technical Field

[0001] The present invention belongs to the field of preparation and application of metal complex catalysts, and particularly relates to a binuclear sulfonamido-modified β-ketoimine zinc complex, a preparation method thereof, and an application thereof in the catalytic ring-opening polymerization of ε-caprolactone. Background Art

[0002] Polycaprolactone (PCL) is a semi-crystalline aliphatic polyester with attractive characteristics such as excellent biodegradability, biocompatibility, good thermal stability, and easy manufacturability. These properties enable PCL to be applied in many fields, ranging from biomedicine, pharmaceuticals to the agricultural field. There are mainly two methods for preparing PCL: the condensation of 6-hydroxycaproic acid and the ring-opening polymerization (ROP) of ε-CL. The polycondensation method synthesizes PCL oligomers by polycondensing 6-hydroxycaproic acid under vacuum. By removing the water generated during the elimination reaction, the reaction is shifted towards the formation of the polymer. This method has defects such as low polymer molecular weight and long reaction time. The ring-opening polymerization method is to catalyze the ring-opening polymerization of ε-caprolactone monomers through a catalyst to obtain polycaprolactone with controllable molecular weight and narrow molecular weight distribution.

[0003] Currently, the industrial preparation of polycaprolactone is mainly through the ring-opening polymerization of ε-caprolactone catalyzed by metal tin complexes. It is very difficult to completely remove metal residues from the polymer, and tin elements have certain cytotoxicity, which will limit the application and promotion of PCL in fields such as medicine. Therefore, it is very meaningful to find a non-toxic metal catalyst to replace the tin catalyst. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a method for the catalytic ring-opening polymerization of ε-caprolactone by a binuclear sulfonamido-modified β-ketoimine zinc complex. This method first prepares a sulfonamido-modified β-ketoimine with a new structure, and further prepares a binuclear sulfonamido-modified β-ketoimine zinc complex. Using the metal complex as a catalyst to catalyze the polymerization of ε-caprolactone, no cocatalyst is required during the catalytic process, and the ring-opening polymerization of ε-caprolactone can be catalyzed at a low catalyst loading ratio, and the resulting polymer also has a relatively high molecular weight.

[0005] The above object of the present invention is achieved by the following technical solutions:

[0006] A binuclear sulfonamido-modified β-ketoimine zinc complex, the binuclear sulfonamido-modified β-ketoimine zinc complex has a structure as shown in General Formula I:

[0007]

[0008] Wherein R is one of C6H5, 2,4,6-MeC6H2, 2,4,6-iPrC6H2.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned binuclear sulfonamide-modified β-ketimine zinc complex, which comprises the following steps:

[0010] In an argon atmosphere, slowly add the ZnEt2 solution dropwise to the β-ketimine ligand solution of the general formula II at 50-100°C and stir for 0.5-2 hours to complete the reaction. The general formula II structure is as follows:

[0011]

[0012] Wherein R=one of C6H5, 2,4,6-MeC6H2, 2,4,6-iPrC6H2.

[0013] Furthermore, in the preparation method, the molar ratio of the β-ketimine ligand having the structure of general formula II to ZnEt2 is 1:1 to 1.6.

[0014] Furthermore, in the preparation method, the solvent in the β-ketimine ligand solution having a structure such as general formula II is one of toluene, acetonitrile and tetrahydrofuran.

[0015] Furthermore, the solvent in the ZnEt2 solution in the preparation method is one of toluene and hexane.

[0016] Another object of the present invention is to protect the application of the binuclear sulfonamide-modified β-ketimine zinc complex.

[0017] Furthermore, the application of the binuclear sulfonamide-modified β-ketimine zinc complex is specifically the application of the binuclear sulfonamide-modified β-ketimine zinc complex in catalyzing the ring-opening polymerization of caprolactone.

[0018] The present invention offers the following advantages over the prior art: a novel preparation method and application of a dinuclear sulfonamide-modified β-ketoimine zinc complex. Using the dinuclear sulfonamide-modified β-ketoimine zinc complex as a catalyst and ε-caprolactone as a raw material, polycaprolactone can be prepared by ring-opening polymerization of caprolactone at 110°C in an anhydrous, oxygen-free environment under the protection of an inert argon atmosphere, without the need for a co-catalyst. The catalyst exhibits low toxicity, a simple preparation method, a novel structure, high catalytic activity, and a low catalyst dosage. The reaction is rapid, resulting in a polymer with a medium molecular weight distribution (1.4-2.0) and a high molecular weight (41,337-193,968 g / mol). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 and Figure 2Schematic diagram of the crystal structures of β-ketoimine zinc complexes 1b and 1c modified with binuclear sulfonamide groups. Detailed implementation manners

[0021] The present invention will be described in detail below with reference to the embodiments. However, the following embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention. The experimental methods adopted by the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained from commercial channels.

[0022] The reaction formulas of the following embodiments are as follows:

[0023]

[0024] Example 1

[0025] L 1 Synthesis of H2: Dissolve Et3N (5.67 g, 0.052 mmol) and N-Boc-1,3-propanediamine (4.48 g, 0.0257 mmol) in CH2Cl2 (50 mL). Under an ice-water bath, add benzenesulfonyl chloride (5 g, 0.0283 mmol) to the solution. After naturally rising to room temperature and continuing to stir for 24 h, quench the reaction with saturated aqueous NaHCO3 solution. Extract the mixture with ethyl acetate (30 mL), and rotary evaporate the solution to obtain a brown solid. Then add hydrochloric acid (10 mL, 12 M) and 1,4-dioxane (20 mL), stir at room temperature for 24 h, rotary evaporate the solution to obtain a hydrochloride solid. Then add this hydrochloride (5.29 g, 0.018 mmol), acetylacetone (1.85 g, 0.018 mmol), NaHCO3 (8 g, 0.09 mmol), and ethanol (40 mL) to a 100 ml eggplant-shaped flask. Stir the mixture at 60 °C for 24 h, then filter and rotary evaporate the filtrate to obtain a yellow solid. Yield: 3.8 g (50%). 1 1H NMR (400 MHz, CDCl3): δ = 10.79 (br, 1H, NH), 7.87 - 7.84 (m, 2H, Ph-H), 7.61 - 7.49 (m, 3H, Ph-H), 4.97 (s, 1H, [OC(C-H)CN]), 4.96 - 4.94 (m, 1H, NH), 3.31 (q, J = 6.4 Hz, 2H, NCH2), 3.04 (q, J = 6.4 Hz, 2H, NCH2), 1.98 (s, 3H, CH3CO), 1.90 (s, 3H, CH3CN), 1.78 (quint, J = 6.4 Hz, 2H, NCH2CH2CH2N).13 13C NMR (126 MHz, Chloroform-d): δ = 194.52, 163.87, 139.97, 132.43, 129.03, 126.85, 95.46, 40.30, 40.08, 30.11, 28.64, 18.77. ESI-HRMS: m / z calcd for [M+H] + : 297.1273; found: 297.1238.

[0026] Example 2

[0027] L 2 Synthesis of H2: Triethylamine (4 g, 0.0396 mmol) and N-Boc-1,3-propanediamine (3 g, 0.0171 mmol) were dissolved in CH2Cl2 (50 mL). Mesitylenesulfonyl chloride (5 g, 0.0188 mmol) was added to the solution under an ice-water bath. The mixture was allowed to warm to room temperature and stirred for 24 h, then quenched with saturated aqueous NaHCO3 and extracted with ethyl acetate (30 mL). The solution was concentrated in vacuo to obtain a yellow solid. Then, hydrochloric acid (10 mL, 12 M) and 1,4-dioxane (20 mL) were added, and the mixture was stirred at room temperature for 24 h. The solution was concentrated in vacuo to obtain a hydrochloride solid. Then, the hydrochloride (3.94 g, 0.012 mmol), acetylacetone (1.2 g, 0.012 mmol), NaHCO3 (5.34 g, 0.06 mmol), and ethanol (40 mL) were added to a 100 mL eggplant-shaped flask. The mixture was stirred at 60 °C for 24 h, then filtered and the filtrate was concentrated in vacuo to obtain a white solid. Yield: 4.28 g (65%). 1 1H NMR (400 MHz, CDCl3): δ = 10.77 (br, 1H, NH), 6.96 (s, 2H, Ph-H), 4.96 (s, 1H, [OC(C-H)CN]), 4.65 (t, J = 6.4 Hz, 1H, NH), 3.27 (q, J = 6.4 Hz, 2H, NHCH2), 2.99 (q, J = 6.4 Hz, 2H, NHCH2), 2.62 (s, 6H, Ph-CH3), 2.30 (s, 3H, Ph-CH3), 1.98 (s, 3H, CH3CO), 1.88 (s, 3H, CH3CN), 1.76 (quint, J = 6.4 Hz, 2H, NCH2CH2CH2N). 13CNMR(126MHz,CDCl3):δ=194.86,163.40,142.14,139.00,133.66,131.99,95.51,40.09,39.79,30.22,28.73,22.91,20.90,18.75.ESI-HRMS:m / z calcd for[M+H] + :339.1742;found:339.1739.

[0028] Example 3

[0029] L 3 Synthesis of H2: Dissolve Et3N (4 g, 0.03 mmol) and N-Boc-1,3-propanediamine (2.61 g, 0.015 mmol) in CH2Cl2 (50 mL). Under an ice-water bath, add 2,4,6-triisopropylbenzenesulfonyl chloride (5 g, 0.0165 mmol) to the solution. Allow it to warm to room temperature naturally and continue stirring for 24 h. Quench the reaction with saturated aqueous NaHCO3. Extract the mixture with ethyl acetate (30 mL). Rotate the solution to dryness to obtain a yellow solid. Then add hydrochloric acid (10 mL, 12 M) and 1,4-dioxane (20 mL), stir at room temperature for 24 h, and rotate the solution to dryness to obtain a hydrochloride solid. Then add this hydrochloride (4.12 g, 0.01 mmol), acetylacetone (1 g, 0.01 mmol), NaHCO3 (4.45 g, 0.05 mmol), and ethanol (40 mL) to a 100 mL eggplant-shaped flask. Stir the mixture at 60 °C for 24 h. Then filter and rotate the filtrate to dryness to obtain a yellow solid. Yield: 2.89 g (40%). 1 H NMR(400MHz,CDCl3):δ=10.79(br,1H,NH),7.16(s,2H,Ph-H),4.96(s,1H,[OC(C-H)CN]),4.47(t,J=6.4Hz,1H,NH),4.11(sept,J=6.8Hz,2H,CH(CH3)2,3.31(q,J=6.4Hz,2H,NCH2),3.05(q,J=6.4Hz,2H,NCH2),2.90(sept,J=6.8Hz,1H,CH(CH3)2),1.98(s,3H,CH3CO),1.90(s,3H,CH3CN),1.81(quint,J=6.8Hz,2H,NCH2CH2CH2N),1.26,(d,J=6.8Hz,12H,Ph-CH(CH3)2),1.25(d,J=6.8Hz,6H,Ph-CH(CH3)2). 1313C NMR(100 MHz, CDCl3): δ = 194.81, 163.37, 152.63, 150.21, 132.33, 123.79, 95.48, 40.24, 40.05, 34.11, 30.39, 29.55, 28.70, 24.89, 23.57, 18.81. ESI-HRMS: m / z calcd for [M+H] + : 445.2495; found: 445.2496.

[0030] Example 4

[0031] (L 1 Synthesis of Zn)2(1a): Under an argon atmosphere, take L 1 H2(0.142 g, 0.48 mmol) and dissolve it in 10 mL of anhydrous toluene. Dropwise add diethylzinc (0.24 mL, 2 M in toluene, 0.48 mmol), and the reaction is stirred at 90 °C for 30 minutes. Cool the reaction system to room temperature, filter to obtain a yellow filtrate, vacuum dry the solvent, and wash it once with 4 mL of n-hexane to obtain a yellow solid. Yield: 0.146 g (85%). 1 1H NMR(400 MHz, DMSO-d 6 ): δ = 7.71 - 7.68 (m, 4H, Ph-H), 7.46 - 7.44 (m, 6H, Ph-H), 4.80 (s, 2H, [OC(C-H)CN]), 3.32 - 3.29 (m, 4H, NHCH2), 2.88 - 2.86 (m, 4H, NHCH2), 1.86 (s, 6H, CH3CO), 1.82 (s, 6H, CH3CN), 1.68 (m, 4H, NHCH2CH2CH2). 13 13C NMR(100 MHz, DMSO-d 6 ): δ = 180.00, 172.64, 143.94, 130.84, 128.94, 126.89, 97.12, 51.07, 46.48, 31.14, 27.92, 21.26.

[0032] Example 5

[0033] (L 2 Synthesis of Zn)2(1b): Under an argon atmosphere, take L 2H2 (0.16 g, 0.48 mmol) was dissolved in 10 mL of anhydrous toluene. Diethylzinc (0.24 mL, 2 M in toluene, 0.48 mmol) was added dropwise. After the reaction was stirred at 90 °C for 30 minutes, the solvent was dried under reduced pressure. 4 mL of n-hexane was added. After filtration, the filtrate was dried under reduced pressure. The obtained solid was dried at 60 °C for 3 h, and the product was characterized by NMR and elemental analysis. Yield: 0.173 g (90%). 1 H NMR (400 MHz, DMSO-d 6 ): δ = 6.86 (s, 4H, Ph-H), 4.77 (s, 2H, [OC(C-H)CN]), 3.29 (br, 4H, NCH2), 2.79 (br, 4H, NCH2), 2.50 (s, 12H, Ph-CH3), 2.18 (s, 6H, Ph-CH3), 1.83 (s, 6H, CH3CO), 1.80 (s, 6H, CH3CN), 1.67 (br, 4H, NCH2CH2CH2N). 13 C NMR (100 MHz, DMSO-d 6 ): δ = 179.89, 172.34, 139.42, 138.49, 137.24, 131.45, 96.90, 51.13, 46.06, 31.19, 27.89, 23.50, 21.16, 20.73. Anal. Calcd for C 34 H 48 N4O6S2Zn2: C, 50.81; H, 6.02; N, 6.97. Found: C, 51.11; H, 6.06; N, 6.73.

[0034] Example 6

[0035] (L 3 Zn)2(1c) synthesis: Under an argon atmosphere, take L 3 H2 (0.2 g, 0.48 mmol) was dissolved in 10 mL of anhydrous toluene. Diethylzinc (0.24 mL, 2 M in toluene, 0.48 mmol) was added dropwise. After the reaction was stirred at 90 °C for 30 minutes, the solvent was dried under reduced pressure. 4 mL of n-hexane was added. After filtration, the filtrate was dried under reduced pressure. The obtained solid was dried at 60 °C for 3 h, and the product was characterized by NMR and elemental analysis. Yield: 0.21 g (90%). 1 H NMR (400 MHz, DMSO-d 6): δ=7.06(s,4H,Ph-H),4.77(s,2H,[OC(CH)CN]),4.39-4.32(m,4H,Ph-CH(CH3)2),3.31(br,4H,NCH2),2.92(br,4H,NCH2),2.78-2.86(m,2H,Ph-CH(CH 3)2),1.85(s,6H,CH3CO),1.79(s,6H,CH3CN),1.75(br,4H,NCH2CH2CH2N),1.16(d,J=6.4Hz,24H,Ph-CH(CH3)2),1.09(d,J=6.4Hz,12H,Ph-CH(CH3)2). 13 C NMR (100 MHz, DMSO-d 6 ):180.01,172.18,150.01,149.87,136.11,123.00,96.77,51.15,46.34,33.72,31.17,29.18,27.78,25.26,24.04,21.16.Anal.Calcd forC 46 H 72 N4O6S2Zn2:C,56.84;H,7.47;N,5.76.Found:C,57.26;H,7.25;N,5.64.

[0036] Example 7

[0037] The temperature for catalyzing the polymerization of ε-caprolactone by a binuclear sulfonamide-modified β-ketimine zinc complex is 110°C. A method for catalyzing the ring-opening polymerization of ε-caprolactone at a monomer to catalyst molar ratio of 1000:1 comprises the following steps:

[0038] Under argon protection, catalyst 1a and ε-caprolactone were mixed, and the resulting mixture was heated and stirred in IKA at 110°C. The reaction system was carefully observed until the magnetic stirring was no longer possible, and the reaction was stopped. The reaction time (t = 3 min) was recorded. The bottle cap was opened and cooled with ice water. A small amount of CH2Cl2 was added to completely dissolve the mixture. A small amount of sample was taken from the reaction mixture to remove volatiles in vacuo. 1 The monomer conversion rate was detected by H NMR (conv. = 92%).

[0039] The reaction mixture was added with a large amount of methanol solution under vigorous stirring to precipitate a crude polymer. When separating and purifying the polymer, a small amount of methanol was used to wash away the residual catalyst, ε-caprolactone and oligomers. The washing operation was repeated three times, and the polymer was vacuum-dried to obtain a polymer sample.

[0040] The present invention uses polystyrene as a standard substance, and analyzes the polycaprolactone obtained in this example by gel permeation chromatography, and measures the polymer molecular weight Mn = 146632 g / mol and the molecular weight distribution

[0041] Example 8

[0042] A method for catalytic ring-opening polymerization of ε-caprolactone by the binuclear sulfonamido-modified β-ketoimine zinc complex 1b under the condition that the molar ratio of monomer to catalyst is 1000:1. The method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 1 min, the monomer conversion rate conv. = 100%, the polymer molecular weight Mn = 41337 g / mol, and the polymer molecular weight distribution D = 1.716.

[0043] Example 8

[0044] A method for catalytic ring-opening polymerization of ε-caprolactone by the binuclear sulfonamido-modified β-ketoimine zinc complex 1c under the condition that the molar ratio of monomer to catalyst is 1000:1. The method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 1 min, the monomer conversion rate conv. = 100%, the polymer molecular weight Mn = 49479 g / mol, and the polymer molecular weight distribution D = 1.747.

[0045] Example 9

[0046] A method for catalytic ring-opening polymerization of ε-caprolactone by the binuclear sulfonamido-modified β-ketoimine zinc complex 1b under the condition that the molar ratio of monomer to catalyst is 2000:1. The method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 1 min, the monomer conversion rate conv. = 65%, the polymer molecular weight Mn = 79064 g / mol, and the polymer molecular weight distribution D = 1.878.

[0047] Example 10

[0048] A method for catalytic ring-opening polymerization of ε-caprolactone by the binuclear sulfonamido-modified β-ketoimine zinc complex 1a under the condition that the molar ratio of monomer to catalyst is 4000:1. The method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 3 min, the monomer conversion rate conv. = 100%, the polymer molecular weight Mn = 193968 g / mol, and the polymer molecular weight distribution D = 1.812.

[0049] Example 11

[0050] Method for catalytic ring-opening polymerization of ε-caprolactone by a binuclear sulfonamido-modified β-ketoimine zinc complex 1b under the condition that the molar ratio of monomer to catalyst is 4000:1, and the method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 1 min, the monomer conversion conv. = 100%, the polymer molecular weight Mn = 106886 g / mol, and the polymer molecular weight distribution D = 1.959.

[0051] Example 12

[0052] Method for catalytic ring-opening polymerization of ε-caprolactone by a binuclear sulfonamido-modified β-ketoimine zinc complex 1c under the condition that the molar ratio of monomer to catalyst is 4000:1, and the method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 1 min, the monomer conversion conv. = 64%, the polymer molecular weight Mn = 77878 g / mol, and the polymer molecular weight distribution D = 1.478.

[0053] Example 13

[0054] Method for catalytic ring-opening polymerization of ε-caprolactone by a binuclear sulfonamido-modified β-ketoimine zinc complex 1b under the condition that the molar ratio of monomer to catalyst is 8000:1, and the method is the same as that in Example 7. The difference from Example 7 is that the catalytic reaction time t = 1 min, the monomer conversion conv. = 76%, the polymer molecular weight Mn = 93210 g / mol, and the polymer molecular weight distribution

[0055] The detection data of the preparation of polycaprolactone by catalytic ring-opening polymerization of ε-caprolactone with the binuclear sulfonamido-modified β-ketoimine zinc complexes 1a, 1b, and 1c in the above examples are shown in Table 1.

[0056] Table 1 Data table of the preparation of polycaprolactone by catalytic ring-opening polymerization of ε-caprolactone with a binuclear sulfonamido-modified β-ketoimine zinc complex at 110 °C without solvent

[0057]

[0058] Note: 1 The monomer conversion was determined by 1 1H NMR spectrum.

[0059] 2 The molecular weight was measured by gel permeation chromatography (GPC) using polystyrene as the standard substance and tetrahydrofuran as the eluent.

[0060] 3 Calculation formula for turnover frequency TOF: TOF = conversion × ([ε-CL]:[Zn]) / time.

[0061] It can be seen from Table 1 that the monomer conversion rate of the dinuclear sulfonamide group-modified β-ketoimine zinc complex prepared by the present invention in the polymerization of ε-caprolactone to prepare polycaprolactone at room temperature of 110 °C is 64% - 100%. Compared with the existing methods for polymerizing ε-caprolactone to prepare polycaprolactone, the monomer conversion rate has been significantly improved. Moreover, the dinuclear sulfonamide group-modified β-ketoimine zinc complex prepared by the present invention can catalyze the polymerization of ε-caprolactone to prepare polycaprolactone without the participation of a cocatalyst. The catalyst preparation method is simple and the structure is novel. Under the condition of 110 °C, when the molar ratio of monomer to catalyst is 1000:1, the complete conversion of the monomer can be achieved in basically 3 minutes. The molecular weight of polycaprolactone reaches up to 193,000 g / mol at most, and the corresponding polymer molecular weight distribution is 1.81.

[0062] Among them, the dinuclear sulfonamide group-modified N-alkyl-β-ketoimine zinc complex 1b catalyzes the ring-opening polymerization of caprolactone and still has catalytic activity at a relatively low catalyst dosage ([ε-CL]:[Zn] = 8000:1). Polycaprolactone with a molecular weight of 93,000 is obtained within 1 minute, and the turnover frequency is as high as 364,800 h -1 , and 1b is not very sensitive to moisture and has great application value.

[0063] The above-described embodiments are only the preferred embodiments of the present invention, rather than all the feasible embodiments of the present invention. For those of ordinary skill in the art, any obvious changes made without departing from the principle and spirit of the present invention should be considered to be included within the protection scope of the claims of the present invention.

Claims

1. A binuclear sulfonamido-modified β-ketoimine zinc complex, characterized in that, The β-ketoimine zinc complex modified with binuclear sulfonamide group has the structure of general formula I: wherein R is one of C6H5, 2,4,6-MeC6H2, and 2,4,6-iPrC6H2.

2. The method for preparing a binuclear sulfonamide-modified β-ketimine zinc complex according to claim 1, wherein the steps It includes: In an argon atmosphere, the ZnEt2 solution is slowly added dropwise to the β-ketoimine ligand solution with the structure of general formula II at 50-100 °C, and the reaction can be completed by stirring for 0.5-2 h; the structure of general formula II is as follows: wherein R is one of C6H5, 2,4,6-MeC6H2, and 2,4,6-iPrC6H2.

3. The preparation method of the binuclear sulfonamido-modified β-ketoimine zinc complex according to claim 2, wherein, The molar ratio of the β-ketoimine ligand with the structure of general formula II to ZnEt2 is 1:1 to 1.

6.

4. The preparation method of the binuclear sulfonamide group-modified β-ketoimine zinc complex according to claim 2, characterized in that, The solvent in the β-ketoimine ligand solution with the structure of general formula II is one of toluene, acetonitrile, and tetrahydrofuran.

5. The method for preparing a binuclear sulfonamide-modified β-ketimine zinc complex according to claim 2, characterized in that: The solvent in the ZnEt2 solution is one of toluene and hexane.

6. The application of the β-ketoimine zinc complex modified with binuclear sulfonamide group according to claim 1.

7. The use of the binuclear sulfonamide-modified β-ketimine zinc complex according to claim 6, characterized in that: Specifically, it is the application of the β-ketoimine zinc complex modified with binuclear sulfonamide group in the ring-opening polymerization of ε-caprolactone.

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