Cobalt metal complex and preparation method and application thereof

Abstract

The invention relates to the technical field of chemical synthesis, and particularly discloses a cobalt metal complex and a preparation method and application thereof. The organic metal complex containing a metal-chlorine-hydrogen bond is prepared by screening a specific ligand, and the complex is applied to a hexafluoroacetone synthesis reaction as a catalyst. Compared with a traditional hexafluoroacetone synthesis method, under the condition of a small amount of catalyst, the cobalt metal complex can obviously improve the selectivity and yield of hexafluoroacetone, meanwhile, the synthesis method is easy in raw material obtaining, simple in reaction step, free of pollution in the reaction process, convenient to purify, high in yield, low in equipment requirement and suitable for industrial production. And industrial production is facilitated, so that the production cost of hexafluoroacetone is effectively reduced.

Description

Technical Field

[0001] This application relates to the technical field of chemical synthesis, and more specifically, it relates to a cobalt metal complex, a preparation method thereof, and an application thereof. Background Art

[0002] Partially or fully fluorinated organic compounds are a very valuable class of chemical products, and perfluoroketones are an important type among them. Hexafluoroacetone (HFA) is a typical perfluoroketone, and many of its uses are well-known. Its main uses include being used as a polymer monomer, monomer intermediate, solvent, chemical, and medicine (such as sevoflurane). However, the low yield of HFA makes it difficult to be commercialized.

[0003] Currently, there are several reactions that can be used to prepare HFA. Bigelow described the direct reaction of acetone with fluorine gas, but the cost of using fluorine gas is too high, making this reaction economically unfeasible. The halogen exchange reaction of hexachloroacetone with hydrogen fluoride (HF) was described in European Patent EP1372549, and this reaction is carried out in the gas phase. In this reaction, the preferred catalyst is a trivalent chromium compound. However, the high boiling point of hexachloroacetone makes it difficult to vaporize in the industrially preferred pressure range of 0.6 - 1.8 MPa, and there will be incomplete conversion, and it is very easy to produce toxic fluorochloroacetone by-products, and these by-products need to be carefully removed completely from the product. In addition, the product obtained from this reaction is a fluoroalcohol rather than hexafluoroacetone. This fluoroalcohol is an adduct formed by hexafluoroacetone and hydrogen fluoride, and this fluoroalcohol has high stability and does not decompose even after distillation. Removing hydrogen fluoride from it and obtaining hexafluoroacetone still requires cumbersome operations. Therefore, the actual effect of the production process based on this reaction is not ideal.

[0004] In some reactions, suitable fluoroolefins can be oxidized to obtain HFA. For example, U.S. Patent US2617836 introduced the application of perfluoroisobutene, a by-product in the production of hexafluoropropene. However, the extremely high toxicity of perfluoroisobutene hinders its transportation and handling. Carlson taught in U.S. Patent US3536733 that oxidizing hexafluoropropene can produce HFA, but the similar boiling points of the product, unreacted raw materials, and by-products including hexafluoropropene oxide and pentafluoropropionyl fluoride make the separation process extremely long and it is difficult to effectively improve production efficiency.

[0005] As described in U.S. Patent No. US3213134, in the presence of the catalyst antimony pentafluoride, once purified, hexafluoropropylene oxide can be isomerized into HFA. However, the additional separation and isomerization operations in this method also make the preparation process cumbersome and difficult to promote on a large scale. Middleton illustrated that the oxidation of hexafluoropropanethione dimer can conveniently prepare HFA, but dithiane must first be prepared from hexafluoropropylene, which adds another step and produces solid waste in the form of sulfite / sulfate.

[0006] Haszeldine has described a method for directly oxidizing highly fluorinated hydrocarbons using chlorine and oxygen as initiators. The products are linear acyl halides or the corresponding acids of fluorinated hydrocarbons, and hexafluoroketone is not obtained as a product. If HFA is to be directly oxidized, a suitable hydrofluoropropane is 1,1,1,3,3,3-hexafluoropropane. McBee described the high-temperature reaction of R236fa in the range of 550 - 585 °C, but masked the fact of low conversion due to low reactivity. As described in U.S. Patent No. US5629460, in this case, a highly reactive initiator such as fluorine is required to oxidize R236fa to directly prepare HFA. As described in U.S. Patent No. US6274005, in the absence of a catalyst, by selecting a relatively high reaction temperature and pressure and irradiating with an ultraviolet lamp, the reaction can also proceed, but the reaction conditions are relatively harsh; in addition, the selectivity of R216aa is relatively high, so it is not conducive to the subsequent separation and purification of hexafluoroacetone.

[0007] Regarding the above related technologies, the inventors believe that the disadvantage of the above fluorine-initiated direct oxidation is the generation of by-product water, which will combine with HFA to form monohydrate, sesquihydrate, and trihydrate. These hydrates are very stable, and it is difficult to release anhydrous HFA by sublimation or evaporation, resulting in a decrease in the yield of anhydrous hexafluoroacetone. To overcome this defect, it is necessary to further improve the selectivity and yield of anhydrous hexafluoroacetone and optimize the reaction conditions as much as possible. Summary of the Invention

[0008] In the related technologies, the generation of hexafluoroacetone hydrate will cause a decrease in the yield of anhydrous hexafluoroacetone. To overcome this defect, it is necessary to further improve the selectivity and yield of anhydrous hexafluoroacetone and optimize the reaction conditions as much as possible. To improve this defect, the present application provides a cobalt metal complex and its preparation method and application.

[0009] In the first aspect, the present application provides a cobalt metal complex, adopting the following technical solution: A cobalt metal complex, the cobalt metal complex has the following structure:

[0010] By adopting the above technical solution, after applying the above cobalt metal complex as a catalyst to the reaction for catalytic preparation of hexafluoroacetone, compared with the traditional synthesis method, when the addition amount of the cobalt metal complex of the present application is less, the formation of hexafluoroacetone hydrate can be reduced, and the selectivity and conversion rate of the reaction can be significantly improved, resulting in an increase in the yield of anhydrous hexafluoroacetone. In addition, the cobalt metal catalyst of the present application also has good effects in reducing the reaction temperature and pressure, and the above effects can be achieved without using ultraviolet lamp irradiation, thus being able to fully overcome the defects in the related art and fully reducing the production cost of hexafluoroacetone.

[0011] In a second aspect, the present application provides a preparation method of a cobalt metal complex, adopting the following technical solution.

[0012] A preparation method of a cobalt metal complex includes the following steps: (1) Under the protection of an inert atmosphere, CoCl 2 is reacted with PMe 3 and magnesium chips in a solvent D to obtain an intermediate B, and the structure of the intermediate B can be expressed as Co(PMe 3 ) 4 ; (2) Under the protection of an inert atmosphere, the intermediate B, CoCl 2 and PMe 3 are added to the solvent D for reaction to obtain a raw material C, and the structure of the raw material C can be expressed as CoCl(PMe 3 ) 3 ; (3) The raw material C and the raw material A are mixed according to a weight ratio of 1:(1.05 - 2.30), and then added to the solvent D for reaction to obtain a cobalt metal complex; in this step, the raw material A has the following structure:

[0013] By adopting the above technical solution, in step (1) of the present application, PMe 3 is used as a ligand, and magnesium chips are used to reduce cobalt chloride. After reduction, cobalt chloride reacts with PMe 3 to undergo a coordination reaction to obtain the intermediate B. Then, in the present application, PMe 3 is still used as a ligand, and the intermediate and cobalt chloride undergo a disproportionation reaction to obtain the raw material C. Through the reaction of the raw material C and the raw material A, the silicon atom and phosphorus atom of the raw material A respectively form bonds with the cobalt atom in the raw material C, thereby obtaining a cobalt metal complex that can be used as a catalyst.

[0014] Preferably, the solvent D is selected as an aprotic solvent.

[0015] Preferably, the aprotic solvent is tetrahydrofuran, which is dehydrated before use.

[0016] By adopting the above technical solution, aprotic solvents, especially tetrahydrofuran, can enhance the solubility of reactants, and dehydration treatment can reduce the generation of hexafluoroacetone hydrate, which helps to improve the selectivity and conversion rate of the reaction, and increase the yield of anhydrous hexafluoroacetone.

[0017] Preferably, the inert atmosphere is a nitrogen atmosphere.

[0018] By adopting the above technical solution, an inert atmosphere represented by a nitrogen atmosphere can fully play a protective role and contribute to the successful progress of the reaction.

[0019] Preferably, in step (1) of the method, CoCl 2 is mixed with PMe 3 and magnesium chips in a molar ratio of 1:(4.0 - 5.0):(2.0 - 3.0).

[0020] Preferably, in step (2) of the method, intermediate B, CoCl 2 and PMe 3 are mixed in a molar ratio of 1:(1.05 - 2.30):(2.05 - 3.50).

[0021] Preferably, in step (3) of the method, raw material C and raw material A are mixed in a molar ratio of 1:(1.05 - 2.30).

[0022] In a third aspect, the present application provides an application of a cobalt metal complex, adopting the following technical solution.

[0023] An application of a cobalt metal complex, using the cobalt metal complex as a catalyst, adding 2-chloro-1,1,1,3,3,3-hexafluoropropane to an aprotic polar solvent under the conditions of a temperature of 20 - 60 °C and a pressure of 0.6 - 1.5 Mpa for catalytic reaction, and obtaining hexafluoroacetone after reacting for 2 - 8 h; the dosage of the cobalt metal complex is 0.5% - 1.0% mol of 2-chloro-1,1,1,3,3,3-hexafluoropropane, and the dosage ratio of 2-chloro-1,1,1,3,3,3-hexafluoropropane to the aprotic polar solvent is (5.0 - 7.0) g:10.0 mL.

[0024] By adopting the above technical solution, the present application uses the above cobalt metal complex as a catalyst to prepare hexafluoroacetone, which not only reduces the temperature and pressure in the synthesis process of hexafluoroacetone, but also has easily available raw materials, simple reaction steps, no pollution during the reaction process, convenient purification, high yield, low requirements for equipment, and is convenient for industrial production.

[0025] Preferably, the aprotic polar solvent is one of 1,4-dioxane, toluene, and diethylene glycol dimethyl ether.

[0026] In summary, the present application has the following beneficial effects: 1. By screening specific ligands, the present application prepares an organometallic complex containing a metal-chloro-hydrogen bond and applies this complex as a catalyst to the hexafluoroacetone synthesis reaction. Compared with the traditional hexafluoroacetone synthesis method, in the case of a small amount of catalyst, the cobalt metal complex of the present application can significantly improve the selectivity and yield of hexafluoroacetone, thereby effectively reducing the cost of the reaction.

[0027] 2. The cobalt metal complex prepared in the present application reduces the temperature and pressure in the synthesis process of hexafluoroacetone. At the same time, the synthesis method has easily available raw materials, simple reaction steps, no pollution during the reaction process, convenient purification, high yield, low requirements for equipment, and is convenient for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of raw material A in the embodiment of the present application.

[0029] Figure 2 is a schematic structural diagram of raw material C in the embodiment of the present application.

[0030] Figure 3 is a schematic structural diagram of the cobalt metal complex in the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present application will be further described in detail below with reference to examples, preparation examples, and comparative examples. The raw materials involved in the present application are all commercially available. EXAMPLES

[0032] Examples 1-5 In the following examples, tetrahydrofuran was subjected to adsorption and water treatment using 4A molecular sieves before use.

[0033] Example 1 In this example, raw material A has Figure 1 the structure shown, and raw material C has Figure 2 the structure shown.

[0034] This example provides a cobalt metal complex having the following structure asFigure 3 The structure shown

[0035] This embodiment also provides a method for preparing a cobalt metal complex, comprising the following steps: (1) Under a nitrogen protection system, weigh raw materials CoCl 2 (11.2 mmol), PMe 3 (44.8 mmol), and magnesium chips (22.4 mmol) into the reaction system, add 75 mL of THF solvent, react at 25 °C for 8 h under nitrogen protection, then cool to room temperature, precipitate will form. After the reaction, filter to obtain a solid, wash with n-pentane, and finally dry in a vacuum drying oven to obtain the intermediate B as a yellow powder (2.89 g, yield 71%).

[0036] (2) Weigh raw materials CoCl 2 (16.3 mmol), intermediate B (17.1 mmol), add PMe 3 (33.4 mmol), then add 100 mL of THF to the system. React at 25 °C for 8 h under nitrogen protection, evaporate the solvent, wash with n-pentane, and dry the remaining solid in a vacuum drying oven to obtain the raw material C as a purple powder (3.89 g, yield 74%).

[0037] (3) Weigh raw material A (28.2 mmol), add raw material C (29.6 mmol), then add 235 mL of THF to the system. React at 25 °C for 4 h under nitrogen protection, evaporate the solvent, wash with n-pentane, and dry the remaining solid in a vacuum drying oven to obtain a yellow powdery solid, which is the cobalt metal complex (12.13 g, yield 76%).

[0038] 1 HNMR (400 MHz, benzene-d6, 300 K, δ, ppm): -11.68 (ddd, Co-H, 1H), 0.63 (s, SiMe, 6H), 0.86 (d, J = 5.55 Hz, PMe 3 , 9H), 1.54 (d, J = 7.12 Hz, PMe 3 , 9H), 7.11 (m, Ar, 6H), 7.45 (m, Ar, 1H), 7.71 (m, Ar, 2H), 8.29 (m, Ar, 5H); 31PNMR (121 MHz, benzene-d6, 300 K, δ, ppm): -5.04 (s, PMe 3 , 1P), 9.9 (m, PMe 3 , 1P), 77.68 (d, PPh 2, 1P); Mass spectrum: Calculated value is 566.99; Measured value is 567.21. Elemental analysis: Calculated value is: C, 55.08; H, 6.93%; Measured value is: C, 55.21%; H, 6.76%.

[0039] Example 2 In this example, raw material A has Figure 1 the structure shown, and raw material C has Figure 2 the structure shown.

[0040] This example provides a cobalt metal complex having the structure as Figure 3 shown.

[0041] This example also provides a method for preparing a cobalt metal complex, comprising the following steps: (1) Under a nitrogen protection system, weigh raw materials CoCl 2 (17.3 mmol), PMe 3 (86.5 mmol) and magnesium chips (51.9 mmol) into the reaction system, add 155 mL of THF solvent, react at 50 °C for 2 h under nitrogen protection, then cool to room temperature, precipitate will form. After the reaction, filter to obtain a solid, wash with n-pentane, and finally dry in a vacuum drying oven to obtain intermediate B as a yellow powder (4.84 g, yield 77%).

[0042] (2) Weigh raw materials CoCl 2 (18.1 mmol), intermediate B (41.6 mmol), add PMe 3 (63.4 mmol), then add 300 mL of THF to the system. React at 50 °C for 2 h under nitrogen protection, evaporate the solvent, wash with n-pentane, and dry the remaining solid in a vacuum drying oven to obtain raw material C as a purple powder (3.97 g, yield 68%); (3) Weigh raw material A (24.7 mmol), add raw material C (56.8 mmol), then add 410 mL of THF to the system. React at 50 °C for 4 h under nitrogen protection, evaporate the solvent, wash with n-pentane, and dry the remaining solid in a vacuum drying oven to obtain a yellow powdery solid, which is the cobalt metal complex (11.05 g, yield 79%).

[0043] 1 HNMR (400 MHz, benzene-d 6 , 300 K, δ, ppm): -11.57 (ddd, Co-H, 1H), 0.82 (s, SiMe, 6H), 1.06 (d, J = 5.55 Hz, PMe 3 , 9H), 1.73 (d, J = 7.12 Hz, PMe3 , 9H), 7.30 (m, Ar, 6H), 7.64 (m, Ar, 1H), 7.90 (m, Ar, 2H), 8.48 (m, Ar, 5H); 31 P NMR (121 MHz, benzene-d 6 , 300 K, δ, ppm): -5.10 (s, PMe 3 , 1P), 9.30 (m, PMe 3 , 1P), 77.62 (d, PPh 2 , 1P); Mass spectrometry: calculated value is 566.99; measured value is 566.81. Elemental analysis: calculated value for C, 55.08; H, 6.93%; measured value: C, 54.93%; H, 7.06%.

[0044] Example 3 In this example, raw material A has the Figure 1 structure shown, and raw material C has the Figure 2 structure shown.

[0045] This example also provides a method for preparing a cobalt metal complex, which includes the following steps: This example provides a cobalt metal complex having the Figure 3 structure shown.

[0046] (1) Under a nitrogen protection system, weigh raw materials CoCl 2 (20.7 mmol), PMe 3 (93.2 mmol) and magnesium chips (51.8 mmol) and put them into the reaction system. Add 170 mL of THF solvent, react at 40 °C for 6 h under nitrogen protection, then cool to room temperature. A precipitate will form. After the reaction, filter by suction to obtain a solid, wash it with n-pentane, and finally dry it in a vacuum drying oven to obtain the intermediate B as a yellow powder (6.32 g, yield 84%).

[0047] (2) Weigh raw materials CoCl 2 (37.5 mmol), intermediate B (41.3 mmol), add PMe 3 (82.5 mmol), then add 200 mL of THF to the system. React at 40 °C for 6 h under nitrogen protection, drain the solvent, wash with n-pentane, and dry the remaining solid in a vacuum drying oven to obtain the purple powder raw material C (10.6 g, yield 88%); (3) Weigh raw material A (38.1 mmol), add raw material C (49.5 mmol), and then add 235 mL of THF to the system. Under nitrogen protection, react at 40 °C for 6 h. Evaporate the solvent, wash with n-pentane, and dry the remaining solid in a vacuum drying oven to obtain a yellow powdery solid, which is the cobalt metal complex (44.1 g, yield 89%).

[0048] 1 HNMR (400 MHz, benzene-d 6 , 300 K, δ, ppm): -11.51 (ddd, Co-H, 1H), 0.88 (s, SiMe, 6H), 1.12 (d, J = 5.55 Hz, PMe 3 , 9H), 1.79 (d, J = 7.12 Hz, PMe 3 , 9H), 7.36 (m, Ar, 6H), 7.70 (m, Ar, 1H), 7.96 (m, Ar, 2H), 8.54 (m, Ar, 5H); 31 PNMR (121 MHz, benzene-d 6 , 300 K, δ, ppm): -5.07 (s, PMe 3 , 1P), 9.34 (m, PMe 3 , 1P), 77.66 (d, PPh 2 , 1P); Mass spectrum: Calculated value is 566.99; Measured value is 566.81. Elemental analysis: Calculated value for C is 55.08%; H is 6.93%; Measured values are: C, 55.18%; H, 7.01%.

[0049] Application Example 1 Add 694.0 mL of 1,4-dioxane to a 2 L high-pressure reactor, and add 5.3 g (9.3 mmol) of the cobalt metal complex as Figure 3 shown. Cool to -10 °C with a refrigerator, and add 347.0 g (1.86 mol) of 2-chloro-1,1,1,3,3,3-hexafluoropropane. Then introduce 59.5 g (1.86 mol) of oxygen into the reactor. Heat the reactor to 20 °C, stop stirring after reacting at 20 °C for 8 h, cool the collection tank to -40 °C, open the gas-phase valve of the reactor, and close the gas-phase valve of the reactor after the weight of the collection tank no longer increases. Analysis by GC / MS reveals a composition that is roughly the same: 5.1% O 2 , 84.6% HFA, 7.0% HFA hydrate, and 3.3% other components.

[0050] Application Example 2 Add 1055.0 mL of 1,4-dioxane to a 2 L high-pressure reactor, and add as Figure 3The shown cobalt metal complex (22.4 g, 39.6 mmol) was cooled to -10 °C with a refrigerator, and 739.0 g (3.96 mol) of 2-chloro-1,1,1,3,3,3-hexafluoropropane was added. Then, 126.7 g (3.96 mol) of oxygen was introduced into the reaction kettle. The reaction kettle was heated to 60 °C, and after reacting at 60 °C for 2 h, stirring was stopped. The collection tank was cooled to -40 °C, the gas phase valve of the reaction kettle was opened, and the gas phase valve of the reaction kettle was closed after the weight of the collection tank no longer increased. Analysis by GC / MS found that it had approximately the same composition: 4.1% O 2 , 86.9% HFA, 6.7% HFA hydrate, and 2.3% other components.

[0051] Application Example 3 1090.0 mL of 1,4-dioxane was added to a 2 L high-pressure reaction kettle. As Figure 3 shown, 14.89 g (26.3 mmol) of the cobalt metal complex was cooled to -10 °C with a refrigerator, and 654.0 g (3.51 mol) of 2-chloro-1,1,1,3,3,3-hexafluoropropane was added. Then, 112.3 g (3.51 mol) of oxygen was introduced into the reaction kettle. The reaction kettle was heated to 50 °C, and after reacting at 50 °C for 4 h, stirring was stopped. The collection tank was cooled to -40 °C, the gas phase valve of the reaction kettle was opened, and the gas phase valve of the reaction kettle was closed after the weight of the collection tank no longer increased. Analysis by GC / MS found that it had approximately the same composition: 1.6% O 2 , 88.1% HFA, 7.1% HFA hydrate, and 3.2% other components.

[0052] Application Example 4 1378.0 mL of toluene was added to a 2 L high-pressure reaction kettle. As Figure 3 shown, 18.8 g (33.2 mmol) of the cobalt metal complex was cooled to -10 °C with a refrigerator, and 827.0 g (4.43 mol) of 2-chloro-1,1,1,3,3,3-hexafluoropropane was added. Then, 141.8 g (4.43 mol) of oxygen was introduced into the reaction kettle. The reaction kettle was heated to 50 °C, and after reacting at 50 °C for 4 h, stirring was stopped. The collection tank was cooled to -40 °C, the gas phase valve of the reaction kettle was opened, and the gas phase valve of the reaction kettle was closed after the weight of the collection tank no longer increased. Analysis by GC / MS found that it had approximately the same composition: 1.5% O 2 , 88.3% HFA, 7.7% HFA hydrate, and 2.5% other components.

[0053] Application Example 5 1432 mL of diethylene glycol dimethyl ether was added to a 2 L high-pressure reaction kettle. As Figure 3The shown cobalt metal complex, 19.57 g (34.6 mmol), was cooled to -10 °C with a refrigerator, and 859.0 g (4.61 mol) of 2-chloro-1,1,1,3,3,3-hexafluoropropane was added. Then, 147.5 g (4.61 mol) of oxygen was introduced into the reaction kettle. The reaction kettle was heated to 50 °C, and after reacting at 50 °C for 4 h, the stirring was stopped. The collection tank was cooled to -40 °C, the gas phase valve of the reaction kettle was opened, and the gas phase valve of the reaction kettle was closed after the weight of the collection tank no longer increased. It was found by GC / MS analysis that they had approximately the same composition: 1.4% O 2 , 88.7% HFA, 8.0% HFA hydrate, and 1.9% other components.

[0054] Through comprehensive analysis of the above Examples 1-3 and Application Examples 1-5, it can be seen that when the cobalt metal complex prepared in this application is used as a catalyst, hexafluoroacetone has a very high selectivity. Without using ultraviolet light irradiation and under relatively mild temperature and pressure conditions, the proportion of HFA in the reaction residue can reach 84.6 - 88.7%. This is because when this cobalt metal complex is used as a catalyst, PMe 3 on the cobalt atom is prone to ionization in the solvent to form empty orbitals, so that oxygen molecules coordinate with the cobalt atom, and then exchange with the chlorine atom in 2-chloro-1,1,1,3,3,3-hexafluoropropane to form the final product hexafluoroacetone.

[0055] The above examples are only explanations of this application, not limitations of this application. Those skilled in the art can make modifications to the examples of this application without creative contributions according to needs after reading this specification, but as long as they are within the scope of the claims of this application, they are protected by the patent law.

Claims

1. A cobalt metal complex, characterized in that The cobalt metal complex has the structure shown below:

2. The method for preparing a cobalt metal complex according to claim 1, characterized in that: The following steps are involved: (1) Under the protection of an inert atmosphere, CoCl2, PMe3 and magnesium chips are added to a solvent D to react to obtain an intermediate B, the structure of which can be represented as Co(PMe3)4; (2) Under the protection of an inert atmosphere, the intermediate B, CoCl2 and PMe3 are added to a solvent D to react to obtain a raw material C, the structure of which can be represented as CoCl(PMe3)3; (3) Mixing the raw material C and the raw material A in a weight ratio of 1:(1.05-2.30), and then adding the mixture into the solvent D for reaction to obtain a cobalt metal complex; in this step, the raw material A has the structure shown below:

3. The method for preparing the cobalt metal complex according to claim 2, characterized in that: The solvent D is an aprotic solvent.

4. The method for preparing a cobalt metal complex according to claim 3, characterized in that: The aprotic solvent is tetrahydrofuran, which is dehydrated before use.

5. The method for preparing the cobalt metal complex according to claim 3, characterized in that: The inert atmosphere is nitrogen atmosphere.

6. The method for preparing a cobalt metal complex according to claim 3, characterized in that: In step (1) of the method, CoCl2 is mixed with PMe3 and magnesium chips in a molar ratio of 1:(4.0-5.0):(2.0-3.0).

7. The method for preparing a cobalt metal complex according to claim 6, characterized in that: In step (2) of the method, intermediate B, CoCl2 and PMe3 are mixed in a molar ratio of 1:(1.05-2.30):(2.05-3.50).

8. The method for preparing a cobalt metal complex according to claim 7, characterized in that: In step (3) of the method, raw material C and raw material A are mixed in a molar ratio of 1:(1.05-2.30).

9. The use of the cobalt metal complex according to claim 1, characterized in that: The cobalt metal complex is used as a catalyst, 2-chloro-1,1,1,3,3,3-hexafluoropropane is added to a non-protonic polar solvent for catalytic reaction at a temperature of 20-60° C. and a pressure of 0.6-1.5 MPa, and hexafluoroacetone is obtained after the reaction for 2-8 hours. The amount of the cobalt metal complex is 0.5%-1.0% mol of 2-chloro-1,1,1,3,3,3-hexafluoropropane, and the ratio of the amount of the 2-chloro-1,1,1,3,3,3-hexafluoropropane to the non-protonic polar solvent is (5.0-7.0) g:10.0 mL.

10. The use of the cobalt metal complex according to claim 9, characterized in that: The aprotic polar solvent is one of 1,4-dioxane, toluene and diethylene glycol dimethyl ether.

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