Beta-ketimine type binuclear aluminum complex as well as preparation method and application thereof

Abstract

The invention discloses a beta-ketimine type binuclear aluminum complex and a preparation method thereof. The binuclear aluminum complex can be used for catalyzing ring opening polymerization of caprolactone, lactide, glycolide, valerolactone, butyrolactone or ethylene carbonate. The invention further discloses a preparation method and application of the binuclear aluminum complex. The preparation method is simple, the reaction condition is mild, the prepared beta-ketimine type binuclear aluminum complex is used as a catalyst, the catalytic activity is high, the stability is good, the service life is long, the molecular weight distribution of the obtained polymerization product is narrow, and the beta-ketimine type binuclear aluminum complex can be well applied to the ring-opening polymerization reaction of cyclic ester.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of β-ketoimine type binuclear aluminum complex and its preparation method and application, it belongs to the technical field of metal organic chemistry, also belongs to the technical field of polymer materials. BACKGROUND

[0002] Biodegradable polymer materials are an important development direction to solve "white pollution" and meet specific biomedical applications (such as drug release, tissue engineering scaffolds). Among them, polycaprolactone (PCL) is of great concern due to its excellent biocompatibility, biodegradability, flexibility and good compatibility with other biological materials. PCL is mainly prepared by ring-opening polymerization (ROP) of caprolactone (ε-CL).

[0003] The development of ring-opening polymerization catalysts is the core of efficient and controllable synthesis of PCL. Traditional catalysts include tin compounds (such as stannous octoate) and metal alkoxides (such as Al(O i Pr)3) and the like. However, tin-based catalysts have potential biological toxicity residue problems, and some single metal catalysts have limitations in activity and control of polymer molecular weight, molecular weight distribution (PDI) and stereoregularity. In recent years, non-metallocene catalysts, especially aluminum-based catalysts, have become a hot spot in the development of ring-opening polymerization due to their low toxicity, high activity and potential in achieving controllable and active polymerization.

[0004] Binuclear or multinuclear metal complexes have gradually attracted attention in recent years. Binuclear complexes can be divided into homobinuclear and heterobinuclear complexes. Compared with mononuclear complexes, binuclear complexes may have the following potential advantages: 1. There may be a synergistic effect between the two metal centers, improving the catalytic activity or the ability to activate monomers; 2. It may be possible to more accurately control the polymerization process to obtain a narrower molecular weight distribution (close to monodisperse) or specific stereoregularity; 3. It may reduce the amount of initiator or improve the stability of the catalyst; 4. The structural design of the binuclear metal site may provide a unique spatial and electronic environment, affecting the monomer insertion mode and polymer chain growth mechanism.

[0005] However, the reported binuclear aluminum complexes, especially those based on specific ligand design for ring-opening polymerization, are still relatively few. Existing research has focused on mononuclear aluminum complexes or binuclear systems based on other ligands (such as Schiff bases, phenoxyl groups). There is still a lack of systematic and in-depth research and high-efficiency catalyst system reports on binuclear aluminum complexes with clear structure based on β-ketoimine ligands and their application in catalyzing caprolactone ring-opening polymerization, especially the exploration of their binuclear synergistic effect and the influence on polymer controllability. SUMMARY

[0006] One object of the present invention is to provide a β-ketoimine type binuclear aluminum complex.

[0007] Another object of the present invention is to provide a method for preparing β-ketoimine-type binuclear aluminum complexes.

[0008] A third object of the present invention is to provide the use of the above-mentioned β-ketoimine type binuclear aluminum complex.

[0009] To achieve the first objective mentioned above, the non-phyrophoretic β-ketoimine type bidentate bimetallic aluminum complex provided by the present invention has the following general structural formula:

[0010]

[0011] In the above general formula, R 1 R 2 R 4 -R 7 It is hydrogen, a C1-C30 hydrocarbon group or aryl, aromatic heterol group, a C1-C30 haloalkyl group, haloaryl, or haloaromatic heterol group; R 3 It is a C1-C30 hydrocarbon group, a C1-C30 haloalkyl group, a haloaryl group, or a haloaryl heteroaryl group; wherein R 1 With R 2 R 2 With R 3 R 3 With R 4 R 4 With R 5 Each pair can be re-formed into an aromatic ring, either individually or simultaneously, wherein the aromatic ring is a benzene ring, a naphthalene ring, or an anthracene ring;

[0012] X and Y are anions or coordination groups including halogens, C1-C30 hydrocarbon groups, aryl groups, oxygen-containing groups, and nitrogen-containing groups; the halogen is fluorine, chlorine, bromine, or iodine; the oxygen-containing group is propylene oxide, butyl oxide, pentyl oxide, or acetylacetone; the nitrogen-containing group is an alkylamino group, preferably a di(C1-C15 alkyl)amino group (the two alkyl groups can be the same or different); X or Y can be one of m or n of the above-mentioned anions or coordination groups, or multiple of the above-mentioned anions and / or coordination groups, but their sum should be m or n; m, n = 1 or 2;

[0013] In the above general structural formula, the total charge of all anions and / or coordinating groups connected to any aluminum metal is the same as the oxidation state of that aluminum metal.

[0014] In the aforementioned β-ketoimine binuclear aluminum complexes, R 1 R 3 and R 5At least one of them is an aryl group; the aryl group is a single benzene, naphthalene, or anthracene group, a benzene, naphthalene, or anthracene group containing a substituent, or multiple benzene, naphthalene, or anthracene groups that are directly connected or connected through a hydrocarbon group or through O, N, P, or S heteroatoms.

[0015] In the aforementioned β-ketoimine binuclear aluminum complexes, R 1 R 3 and R 5 At least one of them is an aromatic heterogroup; the aromatic heterogroup includes thienyl, furanyl, pyranyl, pyridyl, and pyrroleyl.

[0016] The aforementioned β-ketoimine-type binuclear aluminum complexes can have the following general structural formula:

[0017]

[0018] In the above general formula, R 1 R 2 R 4 ~R 7 X, Y, m, and n are as described above.

[0019] This invention also provides a method for preparing the above-mentioned β-ketoimine-type binuclear aluminum complex. The β-ketoimine-type bimetallic aluminum complex is obtained by reacting a bridged bis-β-ketoimine bidentate ligand or the anion of the ligand with an organic compound of metallic aluminum or a complex of metallic aluminum in an organic solvent in one step or stepwise. The reaction temperature is -78℃ to 120℃, and the reaction time is 0.01 to 48 h. The organic solvent is an alkane, cycloalkanes, aromatics, halogenated hydrocarbons, or ether compounds, and the yield is 20% to 100%. The bridged bis-β-ketoimine ligand has the following general structural formula:

[0020]

[0021] In the above general formula, R 1 R 2 R 4 ~R 7 As stated above.

[0022] The present invention also provides the use of the above-mentioned non-magnesian β-ketoimine type bidentate bimetallic aluminum complex, which is used alone as a catalyst in the presence of benzyl alcohol as an initiator, for highly active and highly controllable catalysis of caprolactone ring-opening polymerization to prepare polycaprolactone.

[0023] The β-ketoimine bidentate bimetallic aluminum complex provided by this invention can also be used alone as a catalyst in the presence of benzyl alcohol as an initiator for highly active and controllable catalysis of ring-opening polymerization of other degradable cyclic ester monomers; the other degradable cyclic ester monomers include, but are not limited to, lactide, glycolide, valproic acid lactone, butyrolactone, or ethylene carbonate.

[0024] Ring-opening polymerization and ring-opening copolymerization reactions were carried out in a sealed reactor under an inert atmosphere at a reaction temperature ranging from room temperature to 100°C, preferably 40°C to 90°C. Alkanes, aromatics, halogenated hydrocarbons, or ether solvents were used as the reaction medium, or bulk polymerization was employed. The monomer to catalyst molar ratio ([M] / [I]) was 50:1 to 5000:1. The reaction time was 1 minute to 48 hours. After the reaction was completed, the reaction was terminated with an acid or alcohol solution. The polymer was precipitated, filtered, washed, and vacuum dried before weighing, and the conversion rate was calculated. The molecular weight (M) of the polymer was determined by gel permeation chromatography (GPC). n The composition and sequence distribution of the copolymer were characterized by hydrogen nuclear magnetic resonance (1H NMR) and molecular weight distribution (PDI).

[0025] The non-phyrophoretic β-ketoimine bidentate bimetallic aluminum complex provided by this invention is not only novel in design, combining the advantages of rigid ligand framework effect and bimetallic synergistic effect, but also has a simple synthesis method, mild reaction conditions, and low catalyst cost.

[0026] It exhibits high catalytic activity for the ring-opening polymerization of caprolactone, lactide, and glycolide, achieving >99% conversion rates in a short time under mild conditions, with a time-of-flight (TOF) of up to 1500 h. -1 ;

[0027] Excellent polymerization controllability: narrow molecular weight distribution (PDI = 1.1–1.3);

[0028] Good stability: It maintains high activity and controllability over a wide temperature range (25℃~90℃) and reaction time (≤60min). Detailed Implementation

[0029] The following examples illustrate different aspects of the invention and will help to further understand the invention, but they do not limit the scope of the invention. The synthesis and polymerization reactions of the metal complexes were carried out under anhydrous and oxygen-free atmospheres of argon or nitrogen. Both the raw materials and solvents were purified using standard methods, and the solvents used were dehydrated and deoxygenated. The structures of the complexes were determined using a Bruker AMX-300 NMR spectrometer. 1 HNMR and 13 CNMR was performed using a Nicolet Nexus 470 Fourier transform infrared spectrometer (KBr pellet) to determine infrared (IR) spectra, and elemental analysis was performed using an Elementar Vario ELIII elemental analyzer. Polymer molecular weight (Mn) and molecular weight distribution (PDI) were determined using an HT-GPC 350 high-temperature gel permeation chromatography system.

[0030] Example 1

[0031] Synthesis of ligands L1-L3

[0032]

[0033] Under nitrogen protection, compound D1 (1.41 mmol, 1.0 equiv) and 30 mL of anhydrous toluene were added to a 250 mL dry round-bottom flask, followed by aniline (4.23 mmol, 3.0 equiv) and the catalyst p-toluenesulfonic acid (60 mg). After installing a water separator, the system was heated to 128 °C and refluxed for 72 hours, during which the reaction progress was monitored by thin-layer chromatography (developing solvent: petroleum ether / ethyl acetate = 5:1). After the reaction was completed, the solvent was removed by vacuum distillation, yielding a brown viscous substance. The crude product was purified by silica gel column chromatography (gradient elution of petroleum ether / ethyl acetate = 40:1), finally yielding three isomers of ligands L1-L3.

[0034] Ligand L1, yellow solid, yield 41%. 1 H NMR (500MHz, CDCl3): δ12.41(s,2H),8.52(s,1H),8.13(d,J=7.8Hz,2H),7.61(s,1H),7.41(s,4H),7.33(d,J=7.6Hz,2H),7.29(s,2H),6.48(s,2H). 13 CNMR (101MHz, CDCl3): δ 195.84, 149.48, 140.37, 139.08, 137.53, 131.02, 129.09, 127.33, 126.40, 126.07, 121.40, 118.63, 96.78. Elemental analysis: Theoretical values ​​(%): C, 61.91; H, 3.60; N, 5.55%. Measured values ​​(%): C, 61.94; H, 3.62; N, 5.54%.

[0035] Ligand L2, yellow solid, yield 37% 1 H NMR (500MHz, CDCl3): δ12.52 (s, 1H, NH), 12.33 (s, 1H, NH), 7.97 (d, J=8.9Hz, 1H), 7.8 (s, 1H), 7.47 (s, 2H), 7.39 (s, 2H), 7.36-7.3 0 (m, 1H), 7.25 (s, 2H), 7.23 (d, J=4.8Hz, 1H), 7.20 (d, J=8.0Hz, 2H), 7.13 (s, 1H), 6.87 (d, J=7.6Hz, 2H), 6.16 (s, 1H), 5.77 (s, 1H). 13C NMR (101MHz, CDCl3): δ 197.52, 190.30, 149.43, 149.12, 139.04, 137.46, 134.68, 131.80, 131.76, 130.32, 129.25, 129.11, 129.08, 127.38, 127.26, 126.54, 126.06, 126.04, 124.52, 121.37, 118.60, 92.63, 91.41. Elemental analysis: Theoretical values ​​(%): C, 61.91; H, 3.60; N, 5.55%. Measured values ​​(%): C, 61.94; H, 3.62; N, 5.54%.

[0036] Ligand L3, yellow solid, yield 19% 1 H NMR (500MHz, CDCl3): δ12.35 (s, 2H, NH), 7.31 (d, J=1.3Hz, 2H, ArH), 7.29 (d, J=5.9Hz, 1H, ArH), 7.26-7.22 ( m, 4H, ArH), 7.22-7.19 (m, 1H, ArH), 7.16 (d, J=7.4Hz, 2H, ArH), 6.78 (d, J=7.7Hz, 4H, ArH), 5.41 (s, 2H, CH). 13 C NMR (101MHz, CDCl3): δ 192.57, 151.39, 148.69, 139.62, 138.71, 132.38, 130.27, 128.42, 126.53, 125.75, 121.91, 119.73, 91.28. Elemental analysis: Theoretical values ​​(%): C, 61.91; H, 3.60; N, 5.55%. Measured values ​​(%): C, 61.94; H, 3.62; N, 5.54%.

[0037] Compare with Example 1

[0038] Ligand L1 a Synthesis

[0039]

[0040] Compound D2 (5 mmol, 1.0 equiv) was added to a 100 mL round-bottom flask, followed by 50 mL of dry toluene to dissolve it. Then, aniline (6 mmol, 1.2 equiv) and p-toluenesulfonic acid (100 mg) were added sequentially, and the mixture was refluxed at 128 °C for 72 h. After the reaction was completed, the mixture was cooled to room temperature, concentrated under reduced pressure to remove the solvent, and the crude product was purified by column chromatography (petroleum ether: ethyl acetate = 40:1) to give ligand L4 as a pale yellow solid, with a yield of 54%. 1H NMR (400MHz, CDCl3): δ12.37 (s, 1H, NH), 7.99 (s, 1H, ArH), 7.98 (s, 1H, ArH), 7.56 (s, 1H, Ar H), 7.53 (s, 2H, ArH), 7.39 (s, 2H, ArH), 7.32 (s, 1H, ArH), 7.28 (s, 3H, ArH), 6.46 (s, 1H, CH). 13 C NMR (101MHz, CDCl3): δ197.84, 152.94, 139.11, 137.56, 131.25, 131.16, 131.00, 127.31, 126.62, 126.40, 126.04, 124.66, 118.65, 93.27.Anal.Calcd for C 16 H 11 F3NO: C, 66.21; H, 3.82; N, 4.83%. Found: C, 66.19; H, 3.78; N, 4.85%.

[0041] Example 2

[0042] Synthesis of ligand L4

[0043]

[0044] The synthesis method is as shown in Example 1, except that aniline is replaced with o-chloroaniline. Ligand L4, yellow solid, yield 58%. 1 HNMR (400MHz, CDCl3): δ12.24 (s, 2H, NH), 8.16 (d, J=9.4Hz, 2H, ArH), 7.64 (s, 1H, ArH), 7.28 (d, J=3.8Hz, 8H, ArH), 6.52 (s, 2H, CH). 13 C NMR (101MHz, CDCl3): δ 191.45, 149.29, 138.85, 136.54, 135.15, 132.32, 130.50, 128.64, 127.80, 127.50, 126.38, 121.41, 91.27. Elemental analysis: Theoretical values ​​(%): C, 52.28; H, 2.63; N, 7.32%. Measured values ​​(%): C, 52.52; H, 2.50; N, 7.68%.

[0045] Example 3

[0046] Synthesis of ligand L5

[0047]

[0048] The synthesis method is as shown in Example 1, yielding ligand L5, a yellow solid, in 49% yield. 1 H NMR (400MHz, CDCl3): δ12.41 (s, 1H, NH), 12.34 (s, 1H, NH), 8.56 (s, 1H, ArH), 8.15 (s, 2H, ArH), 7.66 (s, 1H, ArH), 7.20-7.28 (m, 13H, ArH), 6.52 (s, 2H, CH), 2.76 (s, 4H, CH2), 1.27 (d, J=7.6Hz, 6H, CH3). 13 CNMR (101MHz, CDCl3): δ 190.71, 150.36, 150.05, 140.71, 139.29, 135.94, 131.12, 129.14, 128.99, 128.25, 127.79, 127.77, 126.58, 126.49, 124.25, 121.48, 118.71, 115.94, 91.42, 91.37, 24.80, 14.50. Elemental analysis: Theoretical values ​​(%): C, 73.93; H, 5.50; N, 4.93%. Measured values ​​(%): C, 74.26; H, 4.94; N, 5.02%.

[0049] Example 4

[0050] Synthesis of ligand L6

[0051]

[0052] The synthesis method is as shown in Example 1, yielding ligand L6 in 31% yield. 1 ¹H NMR (400MHz, CDCl₃): δ 17.07 (H, s, OH), δ 11.57 (H, s, NH), 7.35-6.69 (3H, m, Ph-H), 5.95 (1H, s, OH), 5.50 (1H, s, =CH), 3.08 (1H, m, N-CH), 2.34 (1H, m, N-CH), 2.19-0.89 (24H, m, CH); Elemental analysis: Theoretical values ​​(%): C, 74.12; H, 9.05; N, 7.86; Measured values ​​(%): C, 74.36; H, 8.93; N, 7.58.

[0053] Example 5

[0054] Synthesis of ligand L7

[0055]

[0056] The synthesis method is as shown in Example 1, yielding ligand L7 in 35% yield.1 ¹H NMR (400MHz, CDCl₃): δ 16.67 (¹H, s, OH), 16.32 (¹H, s, OH), 8.43–7.35 (¹⁵H, m, Ph-H), 5.01 (²H, s, =CH), 3.88 (²H, m, CH₂), 3.56 (²H, m, CH₂), 3.01 (²H, m, CH), 2.63 (²H, s, CH₂), 1.18 (³H, m, CH₃). Elemental analysis: Theoretical values ​​(%): C, 74.97; H, 5.87; N, 5.83; Measured values ​​(%): C, 74.75; H, 5.46; N, 5.62.

[0057] Example 6

[0058] Synthesis of the binuclear aluminum complex Al1

[0059]

[0060] In a cryogenic reaction bath (0°C), ligand L1 (0.8 mmol, 1.0 equiv.) was placed in a dry 50 mL Schlenk flask. After three nitrogen-vacuum purging operations, it was added via syringe. The product was added to 5 mL of toluene dried with molecular sieves. Then, under nitrogen protection, a toluene solution of trimethylaluminum (AlMe3, 1.2 mL, 1.6 mmol, 2.0 equiv.) was slowly added dropwise while stirring continuously at low temperature for 4 hours. The cryogenic bath was removed, and the reaction system was allowed to naturally warm to room temperature and stirred for another 16 hours to complete the reaction. After the reaction, the solvent was removed by pumping out the solvent. The residue was dispersed in 5 mL of dry n-hexane and allowed to stand for 4 hours for precipitation purification. The solvent was removed again under reduced pressure. The crude product was transferred to a glove box and recrystallized by gas-phase diffusion using a dichloromethane (2 mL)-n-hexane (10 mL) dual solvent system. The final product was a yellow solid powder with a yield of 83%. 1 H NMR (400MHz, CDCl3): δ8.16 (s, 2H, ArH), 7.46-7.28 (m, 8H, ArH), 7.12 (s, 2H, ArH), 6.42 (s, 2H, CH), -0.75 (s, 12H, CH3). 13C NMR (101MHz, CDCl3): δ 180.51, 148.62, 140.79, 139.67, 138.69, 131.27, 129.09, 127.38, 126.49, 125.97, 121.45, 118.60, 99.75, -13.17. Elemental analysis: Theoretical values ​​(%): C, 58.45; H, 4.58; N, 4.54%. Measured values ​​(%): C, 58.47; H, 4.52; N, 4.51%.

[0061] Compare with Example 2

[0062] Synthesis of the binuclear aluminum complex Al2

[0063]

[0064] The synthesis method is as shown in Example 6, yielding the control complex Al2 with a yield of 78%. 1 H NMR (400MHz, CDCl3): δ7.86 (s, 2H, ArH), 7.67 (s, 3H, ArH), 7.20-7.42 (t, J=6.5Hz, 7H, ArH) , 7.07 (s, 2H, ArH), 6.06 (s, 1H, CH), 5.95 (s, 1H, ArH), -0.71 (s, 6H, CH3), -0.81 (s, 6H, CH3). 13 C NMR (101MHz, CDCl3): δ 178.52, 177.69, 151.43, 150.32, 139.77, 137.29, 133.98, 132.65, 131.57, 130.09, 129.47, 128.25, 128.08, 127.01, 126.84, 126.10, 125.73, 26.01, 124.59, 120.97, 118.54, 99.39, 98.95, -12.75, -13.28. Elemental analysis: Theoretical values ​​(%): C, 58.45; H, 4.58; N, 4.54%. Measured values ​​(%): C, 58.47; H, 4.52; N, 4.51%.

[0065] Compare with Example 3

[0066] Synthesis of the dinuclear aluminum complex Al3

[0067]

[0068] The synthesis method is as shown in Example 6, yielding the control complex Al3 with a yield of 75%. 1HNMR (500MHz, CDCl3): δ7.35 (d, J=1.3Hz, 2H, ArH), 7.31 (d, J=5.9Hz, 1H, ArH), 7.26-7.22 (m, 4H, ArH), 7.22-7.1 9 (m, 1H, ArH), 7.16 (d, J=7.4Hz, 2H, ArH), 7.10-6.68 (d, J=7.7Hz, 4H, ArH), 5.71 (s, 2H, CH), -0.87 (s, 12H, CH3). 13 CNMR (101MHz, CDCl3): δ 177.69, 148.72, 147.37, 141.58, 139.77, 132.38, 130.27, 128.42, 126.53, 125.71, 121.94, 119.73, 97.36, -12.91. Elemental analysis: Theoretical values ​​(%): C, 58.45; H, 4.58; N, 4.54%. Measured values ​​(%): C, 58.47; H, 4.52; N, 4.51%.

[0069] Compare with Example 4

[0070] Mononuclear aluminum complex Al1 a Synthesis

[0071]

[0072] Place a 50 mL dry Schlenk flask in a low-temperature constant-temperature reaction bath, set the reaction temperature to 0 °C, and add β-ketoimine ligand L1. a After purging with nitrogen three times, 15 mL of dry toluene was added, and the mixture was stirred for 15 min to completely dissolve the ligand. Then, 1.0 mL of trimethylaluminum was added, and the reaction was first carried out at 0 °C for 2 h, followed by a further reaction at room temperature for 10 h. After the reaction was complete, the toluene solvent was dried under vacuum, and then 5 mL of dried n-hexane was added. The mixture was allowed to precipitate completely, and after filtration, the solvent was dried under vacuum to obtain the mononuclear complex Al1. a It is a yellow solid with a yield of 85%. 1 H NMR (400MHz, CDCl3): δ7.97 (s, 1H, ArH), 7.68 (s, 1H, ArH), 7.59 (s, 1H, ArH), 7.52 (s, 2H, ArH ), 7.42(s, 2H, ArH), 7.38(s, 1H, ArH), 7.28(s, 3H, ArH), 6.43(s, 1H, CH), -1.12(s, 6H, CH3). 13C NMR (101MHz, CDCl3): δ179.17, 155.74, 139.82, 138.47, 130.96, 130.84, 130.2 1, 129.86, 128.65, 127.63, 126.91, 119.88, 118.65, 98.62, -13.03.Anal.Calcd for C 18 H 16 AlF3NO: C, 62.25; H, 4.93; N, 4.03%. Found: C, 62.27; H, 4.96; N, 4.01%.

[0073] Compare with Example 5

[0074] Synthesis of binuclear magnesium complex Mg1

[0075]

[0076] Under cryogenic constant-temperature reaction conditions (-78℃), ligand L1 (0.8 mmol, 1.0 equiv) was placed in a 50 mL dry Schlenk flask. After three nitrogen purgings, anhydrous toluene (5 mL) was added, followed by slow addition of di-n-butylmagnesium solution (1.2 mL, 1.6 mmol, 2.0 equiv) via syringe. The reaction was maintained at a low temperature with continuous stirring for 4 hours. The cooling device was then removed, and the system was allowed to warm naturally to room temperature with continuous stirring overnight. After the reaction was complete, volatile components were removed by vacuum distillation. Anhydrous n-hexane (5 mL) was added, and the mixture was allowed to stand for 4 hours to promote precipitation. The solid product was collected and transferred to a glove box. After micro-dissolution with dichloromethane (CH2Cl2), the product was purified by layer-by-layer diffusion crystallization (with slow addition of n-hexane to the upper layer) to finally obtain complex Mg1, a brownish-yellow solid, 0.58 g, with a yield of 56%. 1 H NMR (400MHz, CDCl3): δ8.47 (s, 1H, ArH), 8.09 (d, J=7.8Hz, 2H, ArH), 7.52-7.40 (s, 5H, ArH), 7.30 (d, J=7. 6Hz, 2H, ArH), 7.29 (s, 2H, ArH), 6.39 (s, 2H, CH), 1.35 (d, J=7.5Hz, 24H, CH2), 0.89 (t, J=6.7Hz, 12H, CH3). 13CNMR (101MHz, CD2Cl2): δ178.52, 152.32, 151.77, 139.64, 137.25, 131.17, 129.15, 127.54, 126.87, 126.02, 121.35, 118.72, 98.72, 32.6, 29.5, 26.3, 14.1.Anal.Calcd for C 34 H 34 F6Mg2N2O2: C, 61.39; H, 5.15%; N, 4.21%. Found: C, 61.35; H, 5.17%; N, 4.23%.

[0077] Example 7

[0078] Synthesis of the dinuclear aluminum complex Al4

[0079]

[0080] The synthesis method is as shown in Example 6, yielding complex Al4 with a yield of 54%. 1 HNMR (400MHz, CDCl3): δ8.98 (s, 1H, ArH), 7.96 (d, J=9.4Hz, 2H, ArH), 7.5-7.2 (d, J=3.8Hz, 8H, ArH), 6.54 (s, 2H, CH), 2.19 (s, 6H, CH3), -0.97 (s, 6H, CH3). 13 C NMR (101MHz, CDCl3): δ 177.52, 176.35, 153.43, 151.97, 139.65, 136.98, 135.02, 132.34, 131.76, 130.32, 129.02, 128.79, 128.28, 127.38, 127.01, 125.35, 124.97, 124.81, 124.52, 99.35, 98.47, -13.12. Elemental analysis: Theoretical values ​​(%): C, 51.04; H, 5.06; N, 9.02. Measured values ​​(%): C, 51.17%; H, 4.93%; N, 9.10%.

[0081] Example 8

[0082] Synthesis of the dinuclear aluminum complex Al5

[0083]

[0084] The synthesis method is as shown in Example 6, yielding complex Al5 with a yield of 51%. 1HNMR (400MHz, CDCl3): δ8.52 (s, 1H, ArH), 8.17 (s, 2H, ArH), 7.74 (s, 1H, ArH), 7.20-7.28 (s, 8H, ArH), 6.01 (s, 2H, CH), 2.64 (s, 4H, CH2), 1.19 (d, J=7.6Hz, 6H, CH3), -0.88 (s, 12H, CH3). 13 CNMR (101MHz, CDCl3): δ 177.65, 148.72, 147.88, 139.71, 139.29, 135.94, 131.12, 129.14, 128.99, 128.25, 127.79, 127.77, 126.58, 126.49, 124.25, 121.48, 118.71, 115.94, 91.42, 91.37, 23.88, 14.09, -12.95. Elemental analysis: Theoretical values ​​(%): C, 60.71; H, 5.39; N, 4.16%. Measured values ​​(%): C, 60.73; H, 5.35; N, 4.13%.

[0085] Example 9

[0086] Synthesis of the dinuclear aluminum complex Al6

[0087]

[0088] The synthesis method is as shown in Example 6, yielding a binuclear complex Al6 with a yield of 68%. 1 ¹H NMR (400MHz, CDCl₃): δ 7.41–6.72 (3H, m, Ph-H), 5.50 (1H, s, =CH), 3.8 (2H, m, CH), 3.26 (1H, m, N-CH), 2.49 (1H, m, N-CH), 2.19–0.89 (30H, m, CH); Elemental analysis: Theoretical values ​​(%): C, 63.33; H, 9.07; N, 4.34; Measured values ​​(%): C, 63.36; H, 8.93; N, 4.58.

[0089] Example 10

[0090] Synthesis of the dinuclear aluminum complex Al7

[0091]

[0092] The synthesis method is as shown in Example 6, yielding a binuclear complex Al7 with a yield of 57%. 1¹H NMR (400MHz, CDCl₃): δ 8.46–7.38 (¹⁵H, m, Ph-H), 5.15 (²H, s, =CH), 3.92 (²H, m, CH₂), 3.66 (²H, m, CH₂), 3.12 (²H, m, CH), 2.65 (²H, s, CH₂), 1.40 (²H, m, CH₂), 1.18 (³H, m, CH₃), 0.9 (⁶H, m, CH₃). Elemental analysis: Theoretical values ​​(%): C, 61.73; H, 5.48; N, 4.23; Measured values ​​(%): C, 61.75; H, 5.46; N, 4.32.

[0093] Example 11

[0094] Binary aluminum complex Al1-catalyzed ring-opening polymerization of caprolactone

[0095] The basic molar ratio for the ring-opening polymerization of caprolactone is [CL]:[complex]:[BnOH] = 100:1:1. The experimental procedure is as follows: Place a 100 mL dry polymerization flask in an oil bath at the required temperature, add 20 μmol of the complex Al1, purge with nitrogen three times, then add 5 mL of dried toluene solution, stir until the solid is completely dissolved, then add 20 μmol of benzyl alcohol in a nitrogen atmosphere, continue stirring for 10–20 min to fully activate the complex, then add 2 mmol of caprolactone and start timing. Immediately after the reaction is complete, add 2 drops of anhydrous ethanol to terminate the reaction. Pour the reaction solution into a 100ml clean beaker, take 0.5ml of the reaction solution, remove the solvent by vacuum extraction, and perform NMR analysis to determine the conversion rate of the reaction. Add 80ml of n-hexane to the remaining reaction solution, stir thoroughly for 2 hours, and then filter. Add 5ml of dichloromethane and 50ml of n-hexane to the filtered solid to further wash away the residual catalyst. Repeat the washing until the solid is pure white, then filter again and place the solid in an oven to dry for 10 hours until constant weight. Collect the solid.

[0096] Compare with Examples 6-9

[0097] Compare the aluminum complexes Al2, Al3, and Al1 of Examples 2-5 a Magnesium complex Mg1-catalyzed ring-opening polymerization of caprolactone

[0098] The implementation method is the same as in Example 11, and the control complex catalysts used are the isomers Al2 and Al3 of the binuclear catalyst Al1, and the corresponding mononuclear catalyst Al1. a The reaction conditions and experimental results of the two-nuclear magnesium catalyst Mg1 are shown in Table 1.

[0099] Examples 12-15

[0100] Binary aluminum complex Al4-Al7 catalyzes the ring-opening polymerization of caprolactone

[0101] The implementation method is the same as in Example 11. The complex catalysts used are binuclear catalysts Al4-Al7. The reaction conditions and experimental results are shown in Table 1.

[0102] Example 16

[0103] Ring-opening polymerization of lactide (LA) catalyzed by dinuclear aluminum complex Al1

[0104] The binuclear aluminum complex Al1 was used to catalyze the ring-opening polymerization of lactide. The basic molar ratio for the ring-opening polymerization of lactide was [LA]:[aluminum complex]:[BnOH] = 100:1:1. The experimental procedure was as follows: A 100 mL dry polymerization flask was placed in an oil bath at the required temperature. 20 μmol of the complex Al1 was added, and the mixture was purged with nitrogen three times. Then, 5 mL of dried chlorobenzene solution was added, and the mixture was stirred until the solid was completely dissolved. Subsequently, 20 μmol of benzyl alcohol in a nitrogen atmosphere was added, and the mixture was stirred for 10-20 min to fully activate the complex. Then, 2 mmol of lactide was added, and the timer was started. After the reaction was completed, 2 drops of glacial acetic acid were added immediately to terminate the reaction. The reaction solution was poured into a 100 mL clean beaker. 0.5 mL of the reaction solution was taken, the solvent was removed, and NMR analysis was performed to determine the conversion rate. 100 mL of glacial methanol was added to the remaining reaction solution, and the precipitate was allowed to set overnight. After filtration, the filtered solid was placed in an oven and dried for 10 h until constant weight was achieved. The solid was then collected.

[0105] Table 1. Binary-catalyzed ring-opening polymerization of lactones using dinuclear aluminum (or magnesium) complexes.

[0106]

[0107] a. 5 ml toluene, reaction temperature 70 °C, 20 μmol Al, 20 μmol BnOH, 2.0 mmol ε-CL (except for Example 16), control example 8 was a mononuclear aluminum complex; b. by 1 c. Determined by H NMR; d. Determined by GPC, using tetrahydrofuran as solvent and polymethyl methacrylate as standard sample; e. 2 mmol lactide, other parameters are the same as in a.

Claims

1. A β-ketoimine-type binuclear aluminum complex, characterized in that, The binuclear aluminum complex has the following general structural formula: In the above general formula, R 1 R 2 R 4 ~R 7 It is hydrogen, a C1-C30 hydrocarbon group or aryl, aromatic heterol group, a C1-C30 haloalkyl group, haloaryl, or haloaromatic heterol group; R 3 It is a C1–C30 hydrocarbon group, a C1–C30 haloalkyl group, a haloaryl group, or a haloaryl heteroaryl group; wherein R 1 With R 2 R 2 With R 3 R 3 With R 4 R 4 With R 5 Each pair can be re-formed into an aromatic ring, either individually or simultaneously, wherein the aromatic ring is a benzene ring, a naphthalene ring, or an anthracene ring; X and Y are anions or coordination groups including halogens, C1-C30 hydrocarbon groups, aryl groups, oxygen-containing groups, and nitrogen-containing groups; the halogen is fluorine, chlorine, bromine, or iodine; the oxygen-containing group is propylene oxide, butyl oxide, pentyl oxide, or acetylacetone; the nitrogen-containing group is an alkylamino group; X or Y can be one of m or n of the above-mentioned anions or coordination groups, or multiple of the above-mentioned anions and / or coordination groups, but their sum should be m or n; m, n = 1 or 2; In the above general structural formula, the total charge of all anions and / or coordinating groups connected to any aluminum metal is the same as the oxidation state of that aluminum metal.

2. The β-ketoimine binuclear aluminum complex as described in claim 1, characterized in that: In the aforementioned binuclear aluminum complex, R 1 R 3 and R 5 At least one of them is an aryl or aromatic heterol; the aryl group is a single benzene, naphthalene or anthracene group, a benzene, naphthalene or anthracene group containing a substituent, or multiple benzene, naphthalene or anthracene groups that are directly connected or connected through a hydrocarbon group or through O, N, P, S heteroatoms.

3. The β-ketoimine binuclear aluminum complex as described in claim 1, characterized in that: In the aforementioned binuclear aluminum complex, R 1 R 3 and R 5 At least one of them is an aromatic heterogroup; the aromatic heterogroup includes thienyl, furanyl, pyranyl, pyridyl, and pyrroleyl.

4. The method for preparing the β-ketoimine-type binuclear aluminum complex according to any one of claims 1 to 3, characterized in that: The binuclear aluminum complex is obtained by reacting an organic compound or complex of metallic aluminum with a bridged bis-β-ketoimine bidentate ligand or the anion of the ligand in an organic solvent in a one-step or stepwise manner. The reaction temperature is 0–120°C, and the reaction time is 0.01–48 h. The organic solvent is an alkane, cycloalkanes, aromatics, halogenated hydrocarbons, or ethers. The bridged bis-β-ketoimine ligand has the following general structural formula:

5. The use of the β-ketoimine-type binuclear aluminum complex according to any one of claims 1 to 3 as a catalyst, characterized in that: The binuclear aluminum complex, in the presence of benzyl alcohol as an initiator, acts as a catalyst alone to catalyze the ring-opening polymerization of caprolactone.

6. The use of the β-ketoimine-type binuclear aluminum complex according to any one of claims 1 to 3 as a catalyst, characterized in that: The binuclear aluminum complex, when benzyl alcohol is used as an initiator, can be used alone as a catalyst to catalyze the ring-opening polymerization of lactide, glycolide, valproic acid, butyrolactone, or ethylene carbonate.

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