Cobalt complex, preparation method thereof and preparation method of 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol

Abstract

The invention provides a cobalt complex, a preparation method of the cobalt complex 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 invention does not contain noble metal, is relatively low in cost, and has high cis-product selectivity when being used as a catalyst for catalyzing hydrogenation of 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanedione to prepare 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol. The result of the embodiment shows that when the cobalt complex provided by the invention is used as a catalyst to catalyze hydrogenation of 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanedione to prepare 2, 2, 4, 4-tetramethyl-1, 3-cyclobutanediol, the ratio of the amount of substance of a cis-product to the amount of substance of a trans-product is 91: 9 or above, and the ratio of the cis-product is high.

Description

Technical Field

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

[0002] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol (CBDO) is an important diol polyester monomer, mainly used in the production of high-performance polyester materials. The more mature CBDO synthesis route is to generate dimethyl ketone by thermal cracking of isobutyric acid or isobutyric anhydride, and then dimerize dimethyl ketone to generate 2,2,4,4-tetramethyl-1,3-cyclobutanedione (CBDK), and finally catalytic hydrogenation of CBDK to generate CBDO. The catalytic hydrogenation reaction of CBDK usually produces a mixture of cis- and trans-CBDO. The C4 ring of cis-CBDO is non-planar, and the dihedral angle of the crystal is 17.5°, while the dihedral angle of trans-CBDO is 0°. The ratio of cis- and trans-isomers of CBDO has an important influence on the glass transition temperature, impact strength, crystallization rate and other properties of polyester. At present, the catalysts for catalytic hydrogenation of CBDK to CBDO are mainly divided into two categories. The first category is supported transition metal catalysts, which use activated carbon and other matrices to support active components such as Ni, Cu, Co, and Fe. This catalyst has high catalytic activity for hydrogenation reactions, but usually does not have high selectivity; the second category is noble metal supported catalysts, especially ruthenium-based noble metal catalysts, which have high catalytic activity and selectivity in ketone hydrogenation reactions, but are relatively expensive. Therefore, it is of great significance to develop a low-cost catalyst for the hydrogenation of CBDK to CBDO with high selectivity for cis-products. Summary of the invention

[0003] The purpose of the present invention is to provide a cobalt complex and a preparation method thereof and a preparation method of 2,2,4,4-tetramethyl-1,3-cyclobutanediol. The cobalt complex provided by the present invention does not contain precious metals, has low cost, and has high selectivity for cis-products when catalyzing 2,2,4,4-tetramethyl-1,3-cyclobutanedione to hydrogenate 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a cobalt complex consisting of cobalt ions and ligands;

[0006] The structural formula of the ligand is:

[0007] The present invention also provides a method for preparing the cobalt complex described in the above technical solution, comprising: mixing a cobalt salt, a ligand and an organic solvent, and performing a coordination reaction to obtain the cobalt complex.

[0008] Preferably, the molar ratio of the cobalt salt to 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 volume ratio of the amount of the cobalt salt to the solvent is 0.05 mol: (50-150) mL.

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

[0012] The present invention also provides a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising:

[0013] 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 described in the above technical scheme or the cobalt complex prepared according to the preparation method described in the above technical scheme.

[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 to the base is (3-4):1.

[0016] Preferably, the temperature of the hydrogenation reaction is 130-155° 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 present invention provides a cobalt complex consisting of cobalt ions and ligands;

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

[0019] Figure 1 is the reaction equation of 2,2,4,4-tetramethyl-1,3-cyclobutanediol;

[0020] Figure 2 is a flow chart of the preparation of ligand L1 in Example 1;

[0021] Figure 3 The hydrogen spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanediol prepared in Example 2;

[0022] Figure 4 The carbon spectrum of 2,2,4,4-tetramethyl-1,3-cyclobutanediol prepared in Example 2;

[0023] Figure 5 is a flow chart for the preparation of ligand L2 in Example 3;

[0024] Figure 6 This is a flow chart for the preparation of ligand L3 in Example 5. DETAILED DESCRIPTION

[0025] The present invention provides a cobalt complex consisting of cobalt ions and ligands;

[0026] The structural formula of the ligand is:

[0027]

[0028] The cobalt complex provided by the invention does not contain precious metals, has low cost, and has high selectivity for cis-products 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 invention also provides a method for preparing the cobalt complex described in the above technical solution, comprising: mixing a cobalt salt, a ligand and an organic solvent, and performing a coordination reaction to obtain the cobalt complex.

[0030] Unless otherwise specified, the present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0031] In the present invention, 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 invention, the structural formula of the ligand is: The present invention has no particular limitation on the source of the ligand, and any commercially available product or a product prepared by a conventional preparation method well known to those skilled in the art may be used.

[0033] In the present invention, the molar ratio of the cobalt salt and the ligand is preferably 1:(0.1-1.5). In an embodiment of the present invention, the molar ratio of the cobalt salt and the ligand may 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 invention controls the molar ratio of the cobalt salt and the ligand within the above range, so that the two can fully react to form a complex.

[0034] In the present invention, 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 invention, the volume ratio of the amount of the cobalt salt to the solvent is preferably 0.05 mol: (50-150) mL. In an embodiment of the present invention, the volume ratio of the amount of the cobalt salt to the solvent may 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 invention controls the volume ratio of the amount of the cobalt salt to the solvent within the above range, so that the raw material can be fully dissolved.

[0036] The present invention has no special limitation on the mixing operation of the cobalt salt, the ligand and the organic solvent, and the technical scheme of material mixing well known to those skilled in the art can be adopted.

[0037] In the present invention, the temperature of the coordination reaction is preferably 40-60° C. In an embodiment of the present invention, the temperature of the coordination reaction may specifically be 40° C., 45° C., 50° C., 55° C. or 60° C.

[0038] In the present invention, the coordination reaction time is preferably 6 to 12 hours. In an embodiment of the present invention, the coordination reaction time may be specifically 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours. The present invention controls the coordination reaction temperature and time within the above range, so that the coordination reaction can be fully carried out.

[0039] In the present invention, 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] In the present invention, the product of the coordination reaction is preferably not post-treated, and the product after the coordination reaction is directly used 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 invention also provides a method for preparing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising:

[0042] 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 described in the above technical scheme or the cobalt complex prepared according to the preparation method described in the above technical scheme.

[0043] In the present invention, 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 invention, the mass ratio of the 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base is preferably (3-4): 1. In an embodiment of the present invention, the mass ratio of the 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base may 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 invention controls the mass ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanedione to the base within the above range, which can make the hydrogenation reaction more sufficient and improve the reaction selectivity.

[0045] In the present invention, the mass ratio of the amount of the cobalt salt used to prepare 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. The present invention controls the mass ratio of the amount of the cobalt salt used to prepare the cobalt complex to 2,2,4,4-tetramethyl-1,3-cyclobutanedione within the above range, so that the hydrogenation reaction can be fully carried out, and the proportion of cis products is higher.

[0046] The present invention has no special limitation on the operation of mixing the 2,2,4,4-tetramethyl-1,3-cyclobutanedione, the catalyst and the base, and a technical solution for mixing materials well known to those skilled in the art can be adopted.

[0047] In the present invention, the temperature of the hydrogenation reaction is preferably 130-155° C. In an embodiment of the present invention, the temperature of the hydrogenation reaction may be specifically 130° C., 135° C., 140° C., 145° C., 150° C. or 155° C.

[0048] In the present invention, the hydrogenation reaction time is preferably 10 to 14 hours. In an embodiment of the present invention, the hydrogenation reaction time can be specifically 10 hours, 11 hours, 12 hours, 13 hours or 14 hours.

[0049] In the present invention, the hydrogen pressure of the hydrogenation reaction is preferably 4-6 MPa. In an embodiment of the present invention, the hydrogen pressure of the hydrogenation reaction may be specifically 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa or 6 MPa. The present invention controls the parameters of the hydrogenation reaction within the above range, so that the hydrogenation reaction can be fully carried out.

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

[0051] The present invention has no special limitation on the specific operation of the post-treatment, and the unreacted raw materials can be removed by adopting the post-treatment technical scheme well known to those skilled in the art.

[0052] In an embodiment of the present invention, the post-treatment may specifically be: cooling the product of the hydrogenation reaction to room temperature, filtering to obtain a filtrate, spinning the filtrate to dryness to obtain a crude product, recrystallizing the crude product in n-hexane, filtering and drying to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0053] In the present invention, the reaction equation of 2,2,4,4-tetramethyl-1,3-cyclobutanediol is as follows Figure 12,2,4,4-tetramethyl-1,3-cyclobutanedione is reacted with cobalt catalyst and hydrogen to generate 2,2,4,4-tetramethyl-1,3-cyclobutanediol.

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

[0055] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Example 1

[0057] The preparation method of the cobalt complex is as follows: (1) adding 10 g of 2-(4,5-dihydrooxazol-2-yl)aniline and 7.5 g of triethylamine to a flask containing 200 mL of dichloromethane in sequence, stirring and reacting at room temperature for 20 minutes, cooling the system to 0°C, and then dropwise adding 11.6 g of 2-bromoacetyl chloride in total, returning the temperature to room temperature and continuing to stir and react for 20 hours, quenching the reaction mixture with 150 mL of water after the reaction is completed, extracting three times with dichloromethane (each time with 250 mL of dichloromethane), combining the organic phases, washing the organic phases with a saturated sodium chloride solution, and then drying with anhydrous sodium sulfate, and purifying the resulting crude product by column chromatography (petroleum ether:ethyl acetate volume ratio of 3:1) to obtain 15.1 g of compound I, with a yield of 86%;

[0058] (2) Add 8.5 g of compound I to a flask, then add 200 mL of acetone, stir, and after the solid is completely dissolved, add 6.6 g of diethylamine, stir and react at 70° C. for 24 hours. After the reaction is completed, evaporate the acetone, add 150 mL of water to quench, and extract with dichloromethane three times (each time with 250 mL of dichloromethane). Combine the organic phases, wash the organic phases with saturated sodium chloride solution, and then remove water and dry over anhydrous sodium sulfate. The resulting crude product is purified by column chromatography (petroleum ether: ethyl acetate volume ratio of 3:1) to obtain 7.2 g of ligand L1, with a yield of 87%;

[0059] The structural formula of ligand L1 is

[0060] (3) Under a nitrogen atmosphere, 0.05 mol of CoCl2 and 0.06 mol of ligand L1 were added to a flask containing 100 mL of tetrahydrofuran (the molar ratio of CoCl2 to the ligand was 1:1.2, and the volume ratio of the molar ratio of CoCl2 to tetrahydrofuran was 0.05 mol:100 mL). 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 as follows Figure 2 shown.

[0062] Example 2

[0063] Into the autoclave, 10 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 3 g of potassium carbonate, and 100 mL of the solution of the cobalt-containing complex obtained in Example 1 were added in sequence, the air in the autoclave was replaced three times with nitrogen, and then the nitrogen was replaced once with hydrogen, and hydrogen was introduced. The temperature was controlled to be 150° C., the hydrogen pressure was 5 MPa, and the reaction was kept warm for 12 h. After the reaction, the system was cooled to room temperature, filtered to obtain a filtrate, and the filtrate was spin-dried to obtain a crude product. The crude product was recrystallized from n-hexane, filtered and dried to obtain 9.87 g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, with 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 as follows Figure 3 As shown, the carbon spectrum is Figure 4 shown.

[0065] Example 3

[0066] (1) Add 22 mL of pyrrole and 18.2 g of benzophenone to a flask containing 200 mL of ethanol, then slowly dropwise add 2 mL of trifluoroacetic acid, and stir the mixture at room temperature for 40 min. After TLC shows that the reaction is complete, extract the mixture three times with dichloromethane (250 mL of dichloromethane is used each time), combine the organic phases, wash the organic phases with a saturated sodium bicarbonate solution, and then dry the mixture with anhydrous sodium sulfate. The resulting crude product is purified by column chromatography (petroleum ether: ethyl acetate volume ratio 10:1) to obtain 44.7 g of compound II, with a yield of 90%;

[0067] (2) 8.5 g of compound II was dissolved in 150 mL of ethanol, and the resulting solution was placed in an ice-water bath at 0°C, and 4.8 g of ethylenediamine and 9 mL of a 37% formaldehyde solution were added, and the mixture was returned to room temperature. After stirring for 3 h in a flask, 5 g of sodium hydroxide was added, and the reaction was continued with stirring for 30 min. After the reaction was completed, the reaction mixture was filtered, and the solid residue was transferred to 150 mL of ether, dried over anhydrous sodium sulfate, filtered, and the solvent was dried 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, followed by the addition of 150 mL of toluene and stirring until the solid was completely dissolved. The flask was placed on a stirring rack 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, and then 50 mL of petroleum ether was added. The solution was cooled to -18° C. for recrystallization, filtered, washed, and dried 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 were added to a flask containing 100 mL of 1,4-dioxane (the molar ratio of CoCl2 to the ligand was 1:1.2, and the volume ratio of the molar ratio of CoCl2 to 1,4-dioxane was 0.05 mol:100 mL). 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 as follows Figure 5 shown.

[0072] Example 4

[0073] Into the autoclave, 10 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 3 g of potassium carbonate, and 100 mL of the solution of the cobalt-containing complex obtained in Example 3 were added in sequence, the air in the autoclave was replaced three times with nitrogen, and then the nitrogen was replaced once with hydrogen, and hydrogen was introduced. The temperature was controlled to be 130° C., the hydrogen pressure was 5.5 MPa, and the reaction was kept warm for 12 hours. After the reaction, the system was cooled to room temperature, filtered to obtain a filtrate, and the filtrate was spin-dried to obtain a crude product. The crude product was recrystallized from n-hexane, filtered and dried to obtain 9.46 g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, with a yield of 92% and a cis-trans ratio of 95:5.

[0074] Example 5

[0075] (1) Add 100 mL of 1,4-dioxane and 7.4 g of 2,4,6-trichloro-1,3,5-triazine to a flask, replace the air in the flask with nitrogen three times, introduce nitrogen protection, place the flask in an ice-water bath at 0°C, add 7.3 g of phenylmagnesium bromide, stir and react at room temperature for 10 hours, after the reaction is completed, add 50 mL of water to quench the reaction, let stand and separate, extract with dichloromethane three times (each time with 100 mL of dichloromethane), combine the organic phases, dry the organic phases over anhydrous sodium sulfate, add 30 mL of n-hexane thereto, recrystallize at 0°C, filter and dry to obtain 7.9 g of compound IV, with a yield of 87%;

[0076] (2) Add 4 g of 2-aminopyridine to a flask containing 150 mL of tetrahydrofuran, place the flask in an ice-water bath at 0°C, slowly add 2.5 g of sodium hydride in batches, stir for 30 min, then return the system to room temperature, add 5 g of compound IV, stir and react at room temperature for 12 h, monitor the reaction by TLC, and after the reaction is complete, add 60 mL of water to the reaction mixture to quench the reaction, let stand and separate, extract with ethyl acetate three times (each time with 100 mL of ethyl acetate), combine the organic phases, dry the organic phases over anhydrous sodium sulfate, and spin dry to obtain 6.5 g of ligand L3, with a yield of 96%;

[0077] The structural formula of ligand L3 is

[0078] (3) Under a nitrogen atmosphere, 0.05 mol of CoCl2 and 0.06 mol of ligand L3 were added to a flask containing 100 mL of toluene (the molar ratio of CoCl2 to the ligand was 1:1.2, and the volume ratio of the molar ratio of CoCl2 to toluene was 0.05 mol:100 mL). The flask 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 as follows Figure 6 shown.

[0080] Example 6

[0081] Into the autoclave, 10 g of 2,2,4,4-tetramethyl-1,3-cyclobutanedione, 3 g of potassium carbonate, and 100 mL of the solution of the cobalt-containing complex obtained in Example 5 were added in sequence, the air in the autoclave was replaced three times with nitrogen, and then the nitrogen was replaced once with hydrogen, and hydrogen was introduced. The temperature was controlled to be 155° C., the hydrogen pressure was 6 MPa, and the reaction was kept warm for 12 hours. After the reaction, the system was cooled to room temperature, filtered to obtain a filtrate, and the filtrate was spin-dried to obtain a crude product. The crude product was recrystallized in n-hexane, filtered and dried to obtain 9.76 g of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, with a yield of 94% and a cis-trans ratio of 91:9.

[0082] In summary, when the cobalt complex provided by the present invention 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 selectivity of the cis product is high.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

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

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 includes 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 the preparation methods of claims 2 to 6.

8. The preparation method according to claim 7, characterized in that: The base includes 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.

Images