A cobalt complex, a method for preparing the same and a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanediol

Abstract

The application provides a cobalt complex and a preparation method thereof and a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and belongs to the technical field of organic synthesis. The cobalt complex provided by the application does not contain noble metal and has low cost, and when used as a catalyst to catalyze the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol, the selectivity of the cis product is high. The results of the examples show that when the cobalt complex provided by the application is used as a catalyst to catalyze the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol, the molar ratio of the cis product to the trans product is above 91:9, and the proportion of the cis product is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a cobalt complex, a preparation method thereof and a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanediol. BACKGROUND

[0002] 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO) is an important diol polyester monomer, which is mainly used for producing high-performance polyester materials. A relatively mature CBDO synthesis route is as follows: dimethyl ethylene ketone is generated by thermal cracking of isobutyric acid or isobutyric anhydride, dimethyl ethylene ketone is dimerized to generate 2,2,4,4-tetramethyl-1,3-cyclobutanedione (CBDK), and CBDO is generated by catalytic hydrogenation of CBDK. The catalytic hydrogenation reaction of CBDK usually generates a mixture of cis-CBDO and trans-CBDO, the C4 ring of cis-CBDO is non-planar, the dihedral angle of the crystal is 17.5°, and the dihedral angle of trans-CBDO is 0°, and the cis-trans isomer ratio of CBDO has an important influence on the glass transition temperature, impact strength, crystallization rate and other properties of the polyester. At present, the catalysts for synthesizing CBDO by catalytic hydrogenation of CBDK mainly include two types: the first type is a supported transition metal catalyst, which uses activated carbon or the like as a matrix to support active components such as Ni, Cu, Co and Fe, and this type of catalyst has very high catalytic activity for hydrogenation reaction, but usually has no high selectivity; the second type is a noble metal supported catalyst, especially a ruthenium-based noble metal catalyst, which has relatively high catalytic activity and selectivity in ketone hydrogenation reaction, but has a high cost. Therefore, it is of great significance to develop a catalyst for synthesizing CBDO by hydrogenation of CBDK, which has low cost and high selectivity of cis-product. SUMMARY

[0003] The application aims to provide a cobalt complex, a preparation method thereof and a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanediol. The cobalt complex provided by the application does not contain noble metals, has low cost, and has high selectivity of cis-product when catalyzing the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0004] In order to achieve the above application purposes, the application provides the following technical solutions:

[0005] The application provides a cobalt complex, which is composed of cobalt ions and a ligand.

[0006] The ligand has the following structural formula:

[0007] The application further provides a preparation method of the cobalt complex, comprising: mixing a cobalt salt, a ligand and an organic solvent, performing a coordination reaction to obtain the cobalt complex.

[0008] Preferably, the mass ratio of the cobalt salt and the ligand is 1:(0.1-1.5).

[0009] Preferably, the organic solvent comprises at least one of tetrahydrofuran, benzene, toluene, p-xylene, 1,4-dioxane, dimethyl sulfoxide, 1,2-dichloroethane, diethyl ether, cyclohexane, petroleum ether, chloroform and dichloromethane.

[0010] Preferably, the mass ratio of the cobalt salt and the solvent is 0.05 mol:(50-150) mL.

[0011] Preferably, the temperature of the coordination reaction is 40-60 DEG C, and the time of the coordination reaction is 6-12 h.

[0012] The application further provides a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising:

[0013] Mixing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, a catalyst and a base, and introducing hydrogen to perform a hydrogenation reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol; the catalyst is the cobalt complex according to the above technical solution or the cobalt complex prepared according to the preparation method according to the above technical solution.

[0014] Preferably, the base comprises at least one of K2CO3, KHCO3, NaOtBu, CF3COONa, K3PO4, Na2CO3, Cs2CO3, CsF, LiOH, NaOH, NaHCO3, tBuOK and KOAc.

[0015] Preferably, the mass ratio of the 2,2,4,4-tetramethyl-1,3-cyclobutanedione and the base is (3-4):1.

[0016] Preferably, the temperature of the hydrogenation reaction is 130-155 DEG C, the time of the hydrogenation reaction is 10-14 h, and the hydrogen pressure of the hydrogenation reaction is 4-6 MPa.

[0017] The application provides a cobalt complex, which is composed of a cobalt ion and a ligand;

[0018] The structural formula of the ligand is: The cobalt complex provided by the present application does not contain noble metals, has low cost, and has high cis-product selectivity when used as a catalyst to catalyze the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol. The results of the examples show that when the cobalt complex provided by the present application is used as a catalyst to catalyze the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol, the molar ratio of cis-product to trans-product is above 91:9, and the proportion of cis-product is high. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The reaction equation of 2,2,4,4-tetramethyl-1,3-cyclobutanediol is shown in the following formula:

[0020] Figure 2 The preparation flowchart of the ligand L1 in Example 1 is shown in the following formula:

[0021] Figure 3 The hydrogen spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanediol prepared in Example 2 is shown in the following formula:

[0022] Figure 4 The carbon spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanediol prepared in Example 2 is shown in the following formula:

[0023] Figure 5 The preparation flowchart of the ligand L2 in Example 3 is shown in the following formula:

[0024] Figure 6 The preparation flowchart of the ligand L3 in Example 5 is shown in the following formula. DETAILED DESCRIPTION

[0025] The present application provides a cobalt complex composed of a cobalt ion and a ligand.

[0026] The structural formula of the ligand is as follows:

[0027]

[0028] The cobalt complex provided by the present application does not contain noble metals, has low cost, and has high cis-product selectivity when used as a catalyst to catalyze the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0029] The present application further provides a preparation method of the cobalt complex, which comprises: mixing a cobalt salt, a ligand and an organic solvent, performing a coordination reaction to obtain the cobalt complex.

[0030] The source of each raw material is not particularly limited in the present application, and commercially available products known to those skilled in the art can be used.

[0031] In the present application, the cobalt salt preferably includes at least one of Co(acac)2, CoCl2, CoBr2, CoI2, Co(NTf2)2, Co(BF4)2, Co(OAc)2, Co(NO3)2, and Co(ClO4)2.

[0032] In the present application, the ligand has the following structural formula: The source of the ligand is not particularly limited in the present application, and commercially available products known to those skilled in the art or products prepared by conventional preparation methods can be used.

[0033] In the present application, the molar ratio of the cobalt salt to the ligand is preferably 1:(0.1-1.5). In the embodiments of the present application, the molar ratio of the cobalt salt to the ligand can be specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5. The present application controls the molar ratio of the cobalt salt to the ligand within the above range, so that the two can sufficiently react to form a complex.

[0034] In the present application, the organic solvent preferably includes at least one of tetrahydrofuran, benzene, toluene, p-xylene, 1,4-dioxane, dimethyl sulfoxide, 1,2-dichloroethane, diethyl ether, cyclohexane, petroleum ether, chloroform, and dichloromethane.

[0035] In the present application, the molar amount of the cobalt salt and the volume of the solvent are preferably 0.05 mol:(50-150) mL. In the embodiments of the present application, the molar amount of the cobalt salt and the volume of the solvent can be specifically 0.05 mol:50 mL, 0.05 mol:80 mL, 0.05 mol:100 mL, 0.05 mol:120 mL, or 0.05 mol:150 mL. The present application controls the molar amount of the cobalt salt and the volume of the solvent within the above range, so that the raw materials can be sufficiently dissolved.

[0036] The operation of mixing the cobalt salt, the ligand, and the organic solvent is not particularly limited in the present application, and the technical solutions for mixing materials known to those skilled in the art can be used.

[0037] In the present application, the temperature of the coordination reaction is preferably 40-60°C. In the embodiments of the present application, the temperature of the coordination reaction can be specifically 40°C, 45°C, 50°C, 55°C, or 60°C.

[0038] In the present application, the time of the coordination reaction is preferably 6-12 h. In the embodiments of the present application, the time of the coordination reaction can be specifically 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h. The present application controls the temperature and time of the coordination reaction in the above range, which can make the coordination reaction proceed sufficiently.

[0039] In the present application, the mixing of the cobalt salt, the ligand and the organic solvent and the coordination reaction are preferably carried out in an inert atmosphere; the inert atmosphere is preferably a nitrogen atmosphere.

[0040] The present application preferably does not post-treat the product of the coordination reaction, and directly uses the product after the coordination reaction as a catalyst for catalyzing the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0041] The present application also provides a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising:

[0042] Mixing 2,2,4,4-tetramethyl-1,3-cyclobutanedione, a catalyst and a base, and introducing hydrogen to carry out a hydrogenation reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol; the catalyst is the cobalt complex described in the above technical solution or prepared by the preparation method described in the above technical solution.

[0043] In the present application, the base preferably includes at least one of K2CO3, KHCO3, NaOtBu, CF3COONa, K3PO4, Na2CO3, Cs2CO3, CsF, LiOH, NaOH, NaHCO3, tBuOK and KOAc.

[0044] In the present application, the mass ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base is preferably (3-4):1. In the embodiments of the present application, the mass ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base can be specifically 3:1, 3.1:1, 3.2:1, 3.3:1, 3.33:1, 3.5:1, 3.8:1 or 4:1. The present application controls the mass ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base in the above range, which can make the hydrogenation reaction more sufficient and improve the reaction selectivity.

[0045] In the present application, the mass ratio of the amount of substance of the cobalt salt for preparing the cobalt complex to 2,2,4,4-tetramethyl-1,3-cyclobutanedione is preferably 0.05 mol:(5-15) g, more preferably 0.05 mol:10 g. By controlling the mass ratio of the amount of substance of the cobalt salt for preparing the cobalt complex to 2,2,4,4-tetramethyl-1,3-cyclobutanedione within the above range, the present application can make the hydrogenation reaction proceed sufficiently and the cis product has a higher proportion.

[0046] The present application does not have special limitations on the operation of mixing the 2,2,4,4-tetramethyl-1,3-cyclobutanedione, the catalyst and the base, and the technical solution of material mixing known to those skilled in the art can be used.

[0047] In the present application, the temperature of the hydrogenation reaction is preferably 130-155°C. In the embodiments of the present application, the temperature of the hydrogenation reaction can be specifically 130°C, 135°C, 140°C, 145°C, 150°C or 155°C.

[0048] In the present application, the time of the hydrogenation reaction is preferably 10-14 h. In the embodiments of the present application, the time of the hydrogenation reaction can be specifically 10 h, 11 h, 12 h, 13 h or 14 h.

[0049] In the present application, the hydrogen pressure of the hydrogenation reaction is preferably 4-6 MPa. In the embodiments of the present application, the hydrogen pressure of the hydrogenation reaction can be specifically 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa or 6 MPa. By controlling the parameters of the hydrogenation reaction within the above range, the present application can make the hydrogenation reaction proceed sufficiently.

[0050] After the hydrogenation reaction is completed, the present application preferably performs post-treatment on the product of the hydrogenation reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0051] The present application does not have special limitations on the specific operation of the post-treatment, and the technical solution of post-treatment known to those skilled in the art can be used to remove the unreacted raw materials.

[0052] In the embodiments of the present application, the post-treatment can be specifically: cooling the product of the hydrogenation reaction to room temperature, filtering to obtain a filtrate, spin-drying the filtrate to obtain a crude product, recrystallizing the crude product in n-hexane, drying after filtration to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0053] In the present application, the reaction equation of the 2,2,4,4-tetramethyl-1,3-cyclobutanediol is as follows: Figure 1The 2,2,4,4-tetramethyl-1,3-cyclobutanediol is prepared by the reaction of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with a cobalt catalyst and hydrogen.

[0054] The preparation method provided by the application has mild conditions, simple operation, high yield, and can directly obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol with a high cis ratio.

[0055] The technical solutions in the application will be clearly and completely described below in combination with the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0056] Embodiment 1

[0057] The preparation method of the cobalt complex is as follows: (1) 2-(4,5-dihydrooxazol-2-yl) aniline 10 g and triethylamine 7.5 g are sequentially added into a flask containing 200 mL of dichloromethane, the system is stirred at room temperature for 20 min, then the system is lowered to 0°C, and then 2-bromoacetyl chloride 11.6 g is added dropwise, the system is continuously stirred at room temperature for 20 h, and then the reaction is quenched by adding 150 mL of water, and the reaction mixture is extracted with dichloromethane for three times (250 mL of dichloromethane is used each time), the organic phases are combined, the organic phase is washed with a saturated sodium chloride solution, and then the organic phase is dried over anhydrous sodium sulfate and dried, and then 15.1 g of compound I is obtained by column chromatography (the volume ratio of petroleum ether to ethyl acetate is 3:1), and the yield is 86%;

[0058] (2) 8.5 g of compound I is added into a flask, and then 200 mL of acetone is added, and then the system is stirred until the solid is completely dissolved, and then 6.6 g of diethylamine is added, and then the system is stirred at 70°C for 24 h, and then the acetone is evaporated, and then the system is quenched by adding 150 mL of water, and then the system is extracted with dichloromethane for three times (250 mL of dichloromethane is used each time), the organic phases are combined, the organic phase is washed with a saturated sodium chloride solution, and then the organic phase is dried over anhydrous sodium sulfate and dried, and then 7.2 g of ligand L1 is obtained by column chromatography (the volume ratio of petroleum ether to ethyl acetate is 3:1), and the yield is 87%;

[0059] The structural formula of the ligand L1 is

[0060] (3) Under nitrogen atmosphere, 0.05 mol of CoCl2 and 0.06 mol of ligand L1 (the molar ratio of CoCl2 to ligand is 1:1.2, and the molar ratio of CoCl2 to the volume of tetrahydrofuran is 0.05 mol:100 mL) were added into a flask containing 100 mL of tetrahydrofuran, and the flask was placed on a stirrer and stirred at 60°C for 12 h to obtain a solution containing a cobalt complex.

[0061] The preparation process of ligand L1 in Example 1 is shown in Figure 2 .

[0062] Example 2

[0063] A high-pressure reactor was sequentially charged with 10 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 3 g of potassium carbonate, and 100 mL of the solution containing the cobalt complex obtained in Example 1. The reactor was replaced with nitrogen three times, and then replaced with hydrogen once. Hydrogen was introduced, and the temperature was controlled at 150°C and the hydrogen pressure was 5 MPa. The reaction was carried out for 12 h. After the reaction was completed, the system was cooled to room temperature, and a filtrate was obtained by filtration. The filtrate was spin-dried to obtain a crude product. The crude product was recrystallized in n-hexane, dried after filtration, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol was obtained in a yield of 96% and a cis-trans ratio of 96:4.

[0064] The hydrogen spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanediol prepared in Example 2 is shown in Figure 3 , and the carbon spectrum is shown in Figure 4 .

[0065] Example 3

[0066] (1) A flask containing 200 mL of ethanol was charged with 22 mL of pyrrole and 18.2 g of benzophenone, and then 2 mL of trifluoroacetic acid was slowly added dropwise. The reaction was stirred at room temperature for 40 min. After TLC showed that the reaction was complete, the reaction was extracted three times with dichloromethane (250 mL of dichloromethane was used each time). The organic phase was washed with saturated sodium bicarbonate solution, and then dried over anhydrous sodium sulfate. The obtained crude product was purified by column chromatography (the volume ratio of petroleum ether to ethyl acetate was 10:1) to obtain 44.7 g of compound II in a yield of 90%.

[0067] (2) 8.5 g of compound II was dissolved in 150 mL of ethanol, the obtained solution was placed in an ice water bath at 0°C, 4.8 g of ethylenediamine and 9 mL of a formaldehyde solution with a mass concentration of 37% were added, the temperature was restored to room temperature, the reaction was stirred in a flask for 3 h, then 5 g of sodium hydroxide was added, the stirring was continued for 30 min, after the reaction was completed, the reaction mixture was filtered, the solid residue was moved into 150 mL of ethyl ether, dried over anhydrous sodium sulfate, filtered and the solvent was rotary evaporated to obtain 12.6 g of compound III with a yield of 91%;

[0068] (3) 11.8 g of compound III and 10.7 g of diphenylphosphine were added to a flask, then 150 mL of toluene was added and stirred until the solids were completely dissolved, the flask was placed on a stirring frame and refluxed at 110°C for 36 h, after TLC showed that the reaction was complete, the system was cooled to room temperature, the solvent was removed by vacuum filtration, the obtained viscous solid was dissolved in 100 mL of toluene, then 50 mL of petroleum ether was added, the solution was recrystallized by cooling to -18°C, after filtration and washing, drying was performed to obtain 15.8 g of ligand L2 with a yield of 93%;

[0069] The structural formula of ligand L2 is

[0070] (4) Under a nitrogen atmosphere, 0.05 mol of CoCl2 and 0.06 mol of ligand L2 (the molar ratio of CoCl2 to ligand was 1:1.2, and the molar ratio of CoCl2 to the volume of 1,4-dioxane was 0.05 mol:100 mL) were added to a flask containing 100 mL of 1,4-dioxane, the flask was placed on a stirrer and stirred at 60°C for 9 h to obtain a solution containing a cobalt complex.

[0071] The preparation process of ligand L2 in Example 3 is shown in Figure 5 .

[0072] Example 4

[0073] A high-pressure kettle was sequentially added with 10 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 3 g of potassium carbonate and 100 mL of the solution containing the cobalt complex obtained in Example 3, the kettle was replaced with nitrogen three times, then replaced with hydrogen once, hydrogen was introduced, the temperature was controlled at 130°C, the hydrogen pressure was 5.5 MPa, and the reaction was carried out for 12 h, after the reaction was completed, the system was cooled to room temperature, and the filtrate was obtained by filtration, the filtrate was rotary evaporated to obtain a crude product, the crude product was recrystallized in n-hexane, dried after filtration to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol 9.46 g with a yield of 92% and a cis-trans ratio of 95:5.

[0074] Example 5

[0075] (1) A flask containing 100 mL of 1,4-dioxane and 7.4 g of 2,4,6-trichloro-1,3,5-triazine was replaced with nitrogen three times, and then placed in an ice water bath at 0°C. 7.3 g of phenyl magnesium bromide was added, and the reaction was stirred at room temperature for 10 h. After the reaction was completed, 50 mL of water was added to quench the reaction, and the mixture was allowed to stand to separate into two layers. The organic phase was extracted with dichloromethane three times (100 mL each time), and the combined organic phase was dried over anhydrous sodium sulfate. Then, 30 mL of n-hexane was added to the organic phase, which was recrystallized at 0°C. After filtration and drying, 7.9 g of compound IV was obtained in a yield of 87%.

[0076] (2) A flask containing 150 mL of tetrahydrofuran and 4 g of 2-aminopyridine was placed in an ice water bath at 0°C. Sodium hydride (2.5 g) was added in portions, and the mixture was stirred for 30 min. Then, the system was allowed to return to room temperature, and 5 g of compound IV was added. The reaction was stirred at room temperature for 12 h, and the reaction was monitored by TLC. After the reaction was completed, 60 mL of water was added to quench the reaction, and the mixture was allowed to stand to separate into two layers. The organic phase was extracted with ethyl acetate three times (100 mL each time), and the combined organic phase was dried over anhydrous sodium sulfate. After rotary evaporation, 6.5 g of ligand L3 was obtained in a yield of 96%.

[0077] The structural formula of ligand L3 is shown below.

[0078] (3) Under a nitrogen atmosphere, a flask containing 100 mL of toluene, 0.05 mol of CoCl2, and 0.06 mol of ligand L3 (the molar ratio of CoCl2 to ligand was 1:1.2, and the molar ratio of CoCl2 to the volume of toluene was 0.05 mol:100 mL) was placed on a stirrer and stirred at 50°C for 6 h to obtain a solution containing a cobalt complex.

[0079] The preparation process of ligand L3 in Example 5 is shown in Figure 6 .

[0080] Example 6

[0081] A high-pressure autoclave was charged with 10 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 3 g of potassium carbonate, and 100 mL of the solution containing the cobalt complex obtained in Example 5. The autoclave was replaced with nitrogen three times, and then replaced with hydrogen once. Hydrogen was introduced, and the temperature was controlled at 155°C and the hydrogen pressure was controlled at 6 MPa. The reaction was carried out for 12 h, and then the system was cooled to room temperature. The filtrate was obtained by filtration, and then rotary evaporation was performed to obtain a crude product. The crude product was recrystallized in n-hexane, and then dried by filtration to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol 9.76 g in a yield of 94% and with a cis / trans ratio of 91:9.

[0082] In summary, the cobalt complex provided by the application has high cis-product selectivity when used as a catalyst to catalyze the hydrogenation of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to prepare 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0083] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A cobalt complex consisting of a cobalt ion and a ligand; The structural formula of the ligand is: 、 or .

2. The method for preparing the cobalt complex according to claim 1, comprising: The cobalt salt, the ligand and the organic solvent are mixed and subjected to coordination reaction to obtain the cobalt complex.

3. The preparation method according to claim 2, characterized in that The molar ratio of the cobalt salt to the ligand is 1:(0.1-1.5).

4. The preparation method according to claim 2, characterized in that The organic solvent is selected from at least one of tetrahydrofuran, benzene, toluene, p-xylene, 1,4-dioxane, dimethyl sulfoxide, 1,2-dichloroethane, ether, cyclohexane, petroleum ether, chloroform and dichloromethane.

5. The preparation method according to claim 2 or 4, characterized in that The volume ratio of the amount of the cobalt salt to the solvent is 0.05 mol: (50-150) mL.

6. The preparation method according to claim 2, characterized in that The temperature of the coordination reaction is 40-60° C., and the time of the coordination reaction is 6-12 hours.

7. A method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising: 2,2,4,4-tetramethyl-1,3-cyclobutanedione, a catalyst and a base are mixed, and hydrogen is introduced for hydrogenation reaction to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol; the catalyst is the cobalt complex according to claim 1 or the cobalt complex prepared according to any one of claims 2 to 6.

8. The preparation method according to claim 7, characterized in that The base is selected from at least one of K2CO3, KHCO3, NaOtBu, CF3COONa, K3PO4, Na2CO3, Cs2CO3, CsF, LiOH, NaOH, NaHCO3, tBuOK and KOAc.

9. The preparation method according to claim 7 or 8, characterized in that The mass ratio of the 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base is (3~4):

1.

10. The preparation method according to claim 7, characterized in that The temperature of the hydrogenation reaction is 130-155° C., the time of the hydrogenation reaction is 10-14 hours, and the hydrogen pressure of the hydrogenation reaction is 4-6 MPa.

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