Imidazo [1, 2-alpha] pyridine group-containing bidentate cobalt complex as well as preparation method and application thereof

Abstract

The invention provides a bidentate cobalt complex containing an imidazo [1, 2-alpha] pyridine group as well as a preparation method and application of the bidentate cobalt complex, and belongs to the technical field of organic chemical synthesis. The structural formula of the bidentate cobalt complex is shown in the specification, and the preparation method comprises the following steps: carrying out bromination reaction and cyclization reaction on 2-methoxy-6-acetylpyridine to obtain a bidentate ligand with methoxy and imidazo [1, 2-alpha] pyridyl, and carrying out demethylation reaction on the ligand to obtain another bidentate cobalt complex with hydroxyl and imidazo [1, 2-alpha] pyridyl. The imidazo [1, 2-alpha] pyridyl-containing bidentate cobalt complexes are prepared from imidazo [1, 2-alpha] pyridyl-containing bidentate ligands, and the two ligands react with anhydrous cobalt chloride respectively to obtain various imidazo [1, 2-alpha] pyridyl-containing bidentate cobalt complexes. The electron effect of the complex is adjusted by changing substituent groups on imidazo [1, 2-a] pyridine groups, then the activity of the complex in catalytic reaction is adjusted, and the complex can be further applied to hydrosilylation reaction of styrene and has very important application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic chemical synthesis, and particularly relates to a cobalt complex. BACKGROUND

[0002] Coordination chemistry as a core cross-cutting field connecting catalysis, drug research and material science, its key value lies in constructing metal complexes with clear structure through precise ligand design, and then realizing efficient regulation of specific organic reaction pathways. Among them, imidazo [1,2-α] pyridine structure has become a kind of extremely advantageous multidentate nitrogen heterocyclic ligand because of its unique rigid skeleton and adjustable electronic properties, which provides stable geometric configuration and adaptive electronic environment for the coordination of metal center, so it has attracted much attention in the field of coordination chemistry and organic catalysis. The ligand designed based on this structure can form metal complexes with stable structure and specific spatial configuration with various transition metal ions, and exhibit excellent catalytic activity. It is worth noting that the patent with publication number CN108218925A discloses an imidazopyridine cobalt complex, and the related composition has been proved to be useful for the preparation of antitumor drugs, further verifying the application potential of the ligand derived complex in the field of medicine.

[0003] Among many important organic transformation reactions, the hydrosilylation of olefins is a mature process for the synthesis of high value-added organosilicon compounds. For a long time, the efficient catalysis of this reaction mainly depends on noble metal catalysts such as platinum. However, with the deepening of the concept of green and sustainable chemistry, the problems of resource scarcity, high cost and potential toxicity of noble metal catalysts are increasingly prominent, and the development of low-toxicity, inexpensive 3d transition metal alternative catalysts has become a research hotspot in the field of catalysis. Under this background, cobalt element has shown great potential to replace noble metals in catalytic hydrosilylation reactions due to its abundant resources and environmental friendliness. Therefore, the design and synthesis of new cobalt complexes with imidazo [1,2-α] pyridine structure as ligand not only helps to further elucidate the regulation mechanism of electronic effect and spatial effect in the catalytic process, but also provides efficient and green catalytic solutions for the hydrosilylation of olefins, which has important significance for promoting the development of this reaction in an economic and sustainable direction, and opens up a new path for the construction of new green catalytic system. SUMMARY

[0004] In view of the above technical problems, the present application provides a bidentate cobalt complex containing an imidazo [1,2-α] pyridine group, a preparation method and application thereof. By changing the substituents on the imidazo [1,2-α] pyridine group, the electronic effect of the complex can be adjusted, and the activity of the complex in the catalytic reaction can be further adjusted. The complex can be further applied to the hydrosilylation of styrene.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows: A bidentate cobalt complex containing an imidazo[1,2-a]pyridine group, having the following structure: , wherein R is a hydrogen atom, a methyl group or a trifluoromethyl group.

[0006] A preparation method of a bidentate cobalt complex containing an imidazo[1,2-a]pyridine group, comprising the following steps: (1) subjecting 2-methoxy-6-acetylpyridine to a bromination reaction to obtain compound 1, which has the following structure: ; (2) subjecting a 2-aminopyridine derivative and compound 1 to a cyclization reaction to obtain a bidentate ligand 2, which has the following structure: , wherein R is a hydrogen atom, a methyl group or a trifluoromethyl group; (3) subjecting the bidentate ligand 2 to a demethylation reaction to obtain a bidentate ligand 3, which has the following structure: , wherein R is a hydrogen atom, a methyl group or a trifluoromethyl group; (4) subjecting the bidentate ligand 2 or the bidentate ligand 3 to a complexation reaction with a cobalt precursor to obtain a bidentate cobalt complex I or II.

[0007] The bromination reaction is performed by adding 2-methoxy-6-acetylpyridine, a bromine source and a catalyst into solvent I, and reacting at 80-100 ℃ for 6-24 h; after the reaction is completed, the mixture is cooled to room temperature, filtered, and concentrated under vacuum to obtain the crude product of compound 1; the molar ratio of 2-methoxy-6-acetylpyridine, the bromine source and the catalyst is 1:1-2:1-2; and the ratio of 2-methoxy-6-acetylpyridine to solvent I is 0.01-0.1 mmol / mL.

[0008] The bromine source is N-bromosuccinimide or N-bromophthalimide; the catalyst is p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid or acetic acid; and the solvent I is acetonitrile, toluene, chloroform or tetrahydrofuran.

[0009] The cyclization reaction is performed by adding a 2-aminopyridine derivative, compound 1 and a base into solvent II, and reacting at 80-100 ℃ for 6-24 h; after the reaction is completed, the mixture is cooled to room temperature, filtered, and concentrated under vacuum, and the bidentate ligand 2 is separated by column chromatography; the molar ratio of compound 1, the 2-aminopyridine derivative and the base is 1:1-2:1-2; and the ratio of compound 1 to solvent II is 0.01-0.1 mmol / mL.

[0010] The 2-aminopyridine derivative has the following structure: R is a hydrogen atom, a methyl group or a trifluoromethyl group; the base is sodium bicarbonate, potassium bicarbonate, potassium carbonate, triethylamine or ammonium bicarbonate; the solvent II is acetonitrile, ethanol, chloroform or tetrahydrofuran.

[0011] The step of the demethylation reaction is mixing the bidentate ligand 2 and hydrobromic acid, the substance concentration of the bidentate ligand 2 in the hydrobromic acid is 0.1-0.5 mol / L, the reaction is carried out at 60-100 ℃ for 6-24 h, and the reaction environment is an argon environment.

[0012] The step of the complexation reaction is dissolving the bidentate ligand 2 or the bidentate ligand 3 and a cobalt precursor into a solvent III, and the reaction is carried out at room temperature for 6-24 h, and the reaction environment is an argon environment.

[0013] The cobalt precursor is cobalt chloride; and the solvent III is acetonitrile, ethanol, chloroform or tetrahydrofuran.

[0014] The application of a bidentate cobalt complex containing an imidazo[1,2-a]pyridine group as a metal catalyst in a hydrosilylation reaction, raw materials of the hydrosilylation reaction are styrene and diphenylsilane, and a main product is an anti-Markovnikov hydrosilylation product of styrene.

[0015] Preferably, the styrene, diphenylsilane, bidentate cobalt complex and sodium triethylborohydride are subjected to a hydrosilylation reaction in an organic solvent, after the reaction, quenching, filtration and vacuum concentration are carried out, and column chromatography separation is carried out to obtain the hydrosilylation product.

[0016] Preferably, the molar ratio of the styrene, diphenylsilane, cobalt complex and sodium triethylborohydride in the step is 1:1-1.5:0.01-0.1:0.01-0.1, the organic solvent in the step is tetrahydrofuran, the reaction temperature in the step is 25-70 ℃, the reaction time in the step is 1-12 h, and the reaction environment in the step is an argon environment.

[0017] The application has the following beneficial effects: (1) The application successfully designs and synthesizes six bidentate ligands 2a-c and 3a-c and six novel bidentate cobalt complexes Ia-c and IIa-c derived therefrom for the first time. The preparation route of the series of compounds is reasonable in design, simple and easy to operate, does not require complex reaction conditions and precise equipment, the substrate conversion rate is high during the reaction process, the target product is convenient to separate and purify, and a high reaction yield is finally obtained, which not only reduces the synthesis cost, but also is conducive to the subsequent large-scale preparation and practical application popularization, thereby laying a solid process foundation for further development of the novel complexes.

[0018] (2) The bidentate cobalt complexes IIa-c prepared in the application exhibit a unique novel dimer structure. The structure not only enriches the structural diversity of imidazo [1, 2-a] pyridine ligand derived cobalt complexes, but also endows the complexes with special spatial configuration and electronic distribution characteristics. The dimer structure can optimize the catalytic microenvironment of the metal center through metal-metal interaction or synergistic effect between ligands, thereby providing valuable model compounds for further research on the structure-performance relationship and providing a new idea for complex design oriented to novel structures.

[0019] (3) The cobalt complexes provided by the application exhibit certain catalytic activity in the hydrosilylation reaction of styrene and diphenylsilane, and can effectively promote the generation of target organosilicon compounds. The application potential of the cobalt complexes in olefin hydrosilylation reaction is verified, which provides a new candidate system for replacing traditional noble metal catalysts; more importantly, the catalytic performance provides experimental basis and directional guidance for subsequent structure modification of ligands and structure regulation of complexes, which is helpful to further improve the catalytic efficiency, selectivity and stability and promote the sustainable development of green catalytic system. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 It is the ORTEP diagram of the molecular structure of compound Ia, and the ellipsoid is drawn at a 30% probability level.

[0022] Figure 2 It is the ORTEP diagram of the molecular structure of compound IIa, and the ellipsoid is drawn at a 30% probability level.

[0023] Figure 3 It is the ORTEP diagram of the molecular structure of compound IIb, and the ellipsoid is drawn at a 30% probability level. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.

[0025] Example 1 A preparation method of a bidentate cobalt complex containing an imidazo[1,2-a]pyridine group, and the synthetic route is as follows: Specifically includes the following steps: In a 100 mL round-bottom flask, 2-methoxy-6-acetylpyridine (151.2 mg, 1.00 mmol), N-bromosuccinimide (222.5 mg, 1.25 mmol) and p-toluenesulfonic acid monohydrate (285.3 mg, 1.50 mmol) were added, then 20 mL of acetonitrile solvent was added, heated in an oil bath pot, refluxed at 88 ℃ for 16 hours, after the reaction was completed, cooled to room temperature, filtered, vacuum concentrated and dried to obtain the crude product of compound 1.

[0026] The crude product of compound 1, 2-aminopyridine (117.6 mg, 1.25 mmol) and sodium bicarbonate (126.0 mg, 1.50 mmol) were added to a 100 mL round-bottom flask, and 20 mL of acetonitrile solvent was added, and then placed in an oil bath pot for continued heating, refluxed at 88 ℃ for 7 hours, after the reaction was completed, cooled to room temperature, filtered and concentrated, and the crude product was purified by column chromatography with dichloromethane / ethyl acetate (v / v=5 / 1) as the eluent to obtain the bidentate ligand 2a (150.0 mg), with a yield of 67%. The characterization data is as follows: light yellow solid. 1 H NMR (400 MHz, CDCl3): δ 8.22 (s, 1H), 8.14 (dt, J = 6.8, 1.1 Hz,1H), 7.78 (dd, J = 7.4, 0.6 Hz, 1H), 7.69-7.62 (m,2H), 7.20-7.16 (m, 1H),6.79 (td, J = 6.8, 1.0 Hz, 1H), 6.69 (dd, J = 8.2, 0.6 Hz, 1H), 4.03 (s, 3H). 13 C{ 1H} NMR (151 MHz, CDCl3): δ 163.7, 150.4, 145.9, 145.6, 139.3,125.8,124.8, 117.8, 113.1, 112.6, 111.0, 109.8, 53.2. HRMS (ESI-TOF) m / z: [M + H] + calcd for C 13 H 11 N3O, 226.0975; found, 226.0973. Bidentate ligand 2a (45.0 mg, 0.20 mmol) and cobalt chloride (26.0 mg, 0.20 mmol) were added into a 25 mL Schlenk flask, then 10 mL of anhydrous tetrahydrofuran solvent was added, and the reaction was stirred at room temperature for 10 hours under argon environment. After the reaction was completed, the reaction solution was filtered, and the solid was washed with anhydrous tetrahydrofuran several times, and after drying, the bidentate cobalt complex la (59.0 mg) was obtained, with a yield of 83%. Its characterization data are as follows: green solid. Elemental analysis: C 13 H 11 Cl2CoN3O:C, 43.97; H, 3.12; N, 11.83. Found: C, 43.70; H, 3.13; N, 11.61. Its ORTEP diagram is shown in Figure 1 Fig. 1, in which, in addition to the isotropic sphere model of hydrogen atoms, the thermal ellipsoids of the non-hydrogen atoms are drawn at a 30% probability level, clearly showing the structure of the complex and the coordination environment of the metal center.

[0027] Example 2 A preparation method of a bidentate cobalt complex containing an imidazo[1,2-a]pyridine group, and the synthesis route is as follows: Specifically includes the following steps: In a 100 mL round-bottom flask, 2-methoxy-6-acetylpyridine (151.2 mg, 1.00 mmol), N-bromosuccinimide (222.5 mg, 1.25 mmol), and p-toluenesulfonic acid monohydrate (285.3 mg, 1.50 mmol) were added, then 20 mL of toluene solvent was added, heated in an oil bath, refluxed at 110 ℃ for 8 hours, after the reaction was completed, cooled to room temperature, filtered, vacuum concentrated and dried to obtain the crude product of compound 1.

[0028] The crude product of compound 1, 2-aminopyridine (117.6 mg, 1.25 mmol) and sodium bicarbonate (126.0 mg, 1.50 mmol) were added into a 100 mL round bottom flask, 20 mL of ethanol solvent was added, and the mixture was heated in an oil bath at 100 ℃ for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered and concentrated. The crude product was purified by column chromatography using dichloromethane / ethyl acetate (v / v=5 / 1) as the eluent to obtain the bidentate ligand 2a.

[0029] The bidentate ligand 2a (45.0 mg, 0.20 mmol) and cobalt chloride (28.6 mg, 0.22 mmol) were added into a 25 mL Schlenk flask, and 10 mL of anhydrous ethanol solvent was added. The mixture was stirred at room temperature under an argon atmosphere for 12 hours. After the reaction was completed, the mixture was filtered, and the solid was washed with anhydrous ethanol and n-hexane several times, and dried to obtain the bidentate cobalt complex la.

[0030] Example 3 In this example, 2-aminopyridine was replaced by 2-amino-4-methylpyridine, and the other conditions were the same as in Example 1. The final product obtained was the pincer tridentate cobalt complex lb, which had the following structure: The characterization data of lb (64.3 mg, 87%) were as follows: green solid. Elemental analysis: C 14 H 13 Cl2CoN3O: C, 45.56; H, 3.55; N, 11.38. Found: C, 45.32; H, 3.63; N, 11.09. Example 4 In this example, 2-aminopyridine was replaced by 2-amino-4-trifluoromethylpyridine, and the other conditions were the same as in Example 1. The final product obtained was the pincer tridentate cobalt complex lc, which had the following structure: The characterization data of lc (77.2 mg, 91%) were as follows: green solid. Elemental analysis: C 14 H 10 Cl2CoN3O: C, 39.74; H, 2.38; N, 9.93. Found: C, 40.03; H, 2.52; N, 9.60. Example 5 A method for preparing a bidentate cobalt complex containing an imidazo[1,2-a]pyridine group, and the synthesis route is as follows: comprising the following steps: In a 10 mL Schlenk tube, 2a (45.0 mg, 0.20 mmol) was added, followed by hydrobromic acid (2.0 mL, 40% in water), and then heated to reflux in an oil bath at 80 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature and neutralized with saturated sodium bicarbonate solution. Then the mixture was extracted with dichloromethane, and the organic phase was combined, dried over anhydrous magnesium sulfate, filtered, concentrated in vacuo and dried to give the bidentate ligand 3a (35.0 mg) in 83% yield. Characterization data: white solid. 1 H NMR (400 MHz, DMSO- d 6): δ 11.43 (s, 1H), 8.75-8.51 (m, 2H), 7.65-7.48 (m, 2H),7.39-7.24 (m, 1H),7.08-6.86 (m, 2H), 6.35 (d, J = 8.9 Hz, 1H). 13 C{ 1 H} NMR (101MHz, MeOD): δ 165.8, 147.1,143.7, 141.7, 138.9, 128.3, 128.2, 119.3, 117.9,114.9, 112.9, 105.9.HRMS (ESI-TOF) m / z: [M + H] + calcd for C 12 H9N3O, 212.0819;found, 212.0820. In a 25 mL Schlenk tube, bidentate ligand 3a (0.20 mmol) and cobalt chloride (26.0 mg, 0.20 mmol) were added, followed by 10 mL of anhydrous tetrahydrofuran solvent, and the reaction was stirred at room temperature for 10 h under argon. After the reaction was completed, the reaction solution was filtered, and the solid was washed with anhydrous tetrahydrofuran several times, and dried to obtain the bidentate cobalt complex IIa. Characterization data: green solid. Elemental analysis: C 24 H 18 Cl4Co2N6O2: C, 42.26; H, 2.66; N,12.32. Found: C, 42.11; H, 2.67; N, 12.22. Its ORTEP diagram is shown in Figure 2 .

[0031] Example 6 A method for preparing a bidentate cobalt complex containing an imidazo[1,2- a]pyridine group, the synthetic route is shown as follows: Specifically comprising the following steps: In a 10 mL Schlenk tube, 2a (45.0 mg, 0.20 mmol) was added, followed by hydrobromic acid (2.0 mL, 40% in water), and then heated to reflux in an oil bath at 100 ℃ for 6 h. After the reaction was completed, the solution was cooled to room temperature and neutralized with saturated sodium bicarbonate solution. Then the organic phase was extracted with dichloromethane, and the organic phase was combined, dried over anhydrous magnesium sulfate, filtered, concentrated in vacuo and dried to obtain the bidentate ligand 3a.

[0032] In a 25 mL Schlenk tube, the bidentate ligand 3a (136.4 mg, 0.20 mmol) and cobalt chloride (28.6 mg, 0.22 mmol) were added, followed by 10 mL of anhydrous ethanol solvent, and then the reaction was stirred at room temperature under argon for 12 h. After the reaction was completed, the reaction solution was filtered, and the solid was washed with anhydrous ethanol and n-hexane several times, and then dried to obtain the bidentate cobalt complex IIa.

[0033] Example 7 In this example, 2-aminopyridine was replaced by 2-amino-4-methylpyridine, and other conditions were the same as in Example 5. The final product was the pincer tridentate cobalt complex IIb, and its structure was as follows: Its characterization data were as follows: IIb (64.0 mg, 90%): green solid. Elemental analysis: C 26 H 22 Cl4Co2N6O2: C, 43.97; H, 3.12; N, 11.83. Found: C, 43.59; H, 3.24; N, 11.58. Its ORTEP diagram is shown in Figure 3 .

[0034] Example 8 In this example, 2-aminopyridine was replaced by 2-amino-4-trifluoromethylpyridine, and other conditions were the same as in Example 5. The final product was the pincer tridentate cobalt complex IIc, and its structure was as follows: Its characterization data were as follows: IIc (65.1 mg, 79%): green solid. Elemental analysis: C 26 H 16 Cl4Co2F6N6O2: C, 38.17; H, 1.97; N, 10.27. Found: C, 37.80; H, 1.82; N, 9.87. Application examples The three cobalt complexes Ia-c obtained in Examples 1 and 3-4 and the three cobalt complexes IIa-c obtained in Examples 5 and 7-8 were used as catalysts to carry out the hydrosilylation reaction of styrene: Under argon protection, cobalt complexes Ia-c and IIa-c (0.01 mmol) were added as catalysts to six 10 mL Shrek tubes, followed by the addition of styrene (0.50 mmol), diphenylsilane (0.55 mmol), and anhydrous tetrahydrofuran solvent (1.0 mL). The reaction was then transferred to a cryogenic environment of -38 °C, and sodium triethylborohydride (0.02 mmol) was added dropwise. After the addition was complete, the reaction was heated to 50 °C and continued for 4 hours. After the reaction was completed, it was cooled to room temperature and quenched with 2 mL of petroleum ether. The reaction solution was then filtered and concentrated, and the crude product was purified by column chromatography using petroleum ether as the eluent to obtain compound 3a.

[0035] The following are the results of using different cobalt complexes as catalysts for the hydrosilylation of styrene.

[0036] Table 1. Six cobalt complexes as catalysts for the hydrosilylation of styrene. a [a] Reaction conditions: styrene (0.50 mmol), diphenylsilane (0.55 mmol), cobalt complex (0.01 mmol), NaBHEt3 (0.02 mmol), THF (1.0 mL), 50 °C, 4 h, argon atmosphere, separation yield; [b] Yield was determined by 1H NMR spectroscopy.

[0037] The following conclusions can be drawn from the experimental results in Table 1: (1) In the hydrosilylation reaction of styrene and diphenylsilane, cobalt complexes Ia-c and IIa-c have a certain promoting effect on the formation of anti-Markovnikov hydrosilylation product 3a. (2) It is possible that due to its own dimerization, the catalytic efficiency of cobalt complex IIa for anti-Markovnikov hydrosilylation product 3a is less than that of cobalt complex Ia. (3) Imidazolo[1,2-] in bidentate cobalt ligands α Introducing electron-donating (CH3) and electron-withdrawing (CF3) groups onto the pyridyl group will reduce the yield of the anti-Markovnikov hydrosilylation product to varying degrees. Therefore, improving the yield may require further adjustment and design of the ligand host.

[0038] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A bidentate cobalt complex containing an imidazo[1,2-α]pyridine group, characterized in that, The structural formula is as follows: In the formula, R is a hydrogen atom, a methyl group, or a trifluoromethyl group.

2. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group as described in claim 1, characterized in that, Includes the following steps: (1) 2-Methoxy-6-acetylpyridine was brominated to give compound 1, the structural formula of which is as follows: ; (2) The 2-aminopyridine derivative and compound 1 were cyclized to obtain bidentate ligand 2. The structural formula of bidentate ligand 2 is as follows: R is a hydrogen atom, a methyl group, or a trifluoromethyl group; (3) The bidentate ligand 2 was demethylated to obtain bidentate ligand 3. The structural formula of bidentate ligand 3 is as follows: R is a hydrogen atom, a methyl group, or a trifluoromethyl group; (4) The bidentate ligand 2 or bidentate ligand 3 is complexed with the cobalt precursor to obtain bidentate cobalt complex I or II.

3. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to claim 2, characterized in that, The bromination reaction is carried out as follows: 2-methoxy-6-acetylpyridine, bromine source and catalyst are added to solvent I and reacted at 80-100 °C for 6-24 h; the molar ratio of 2-methoxy-6-acetylpyridine, bromine source and catalyst is 1:1-2:1-2; the ratio of 2-methoxy-6-acetylpyridine to solvent I is 0.01-0.1 mmol / mL.

4. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to claim 3, characterized in that, The bromine source is N-bromosuccinimide or N-bromophthalimide; the catalyst is p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid or acetic acid; and the solvent I is acetonitrile, toluene, chloroform or tetrahydrofuran.

5. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to claim 2, characterized in that, The cyclization reaction is carried out as follows: 2-aminopyridine derivative, compound 1 and base are added to solvent II and reacted at 80-100 °C for 6-24 h; the molar ratio of compound 1, 2-aminopyridine derivative and base is 1:1-2:1-2; the ratio of compound 1 to solvent II is 0.01-0.1 mmol / mL.

6. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to claim 5, characterized in that, The structural formula of the 2-aminopyridine derivative is as follows: R is a hydrogen atom, a methyl group, or a trifluoromethyl group; the base is sodium bicarbonate, potassium bicarbonate, potassium carbonate, triethylamine, or ammonium bicarbonate; the solvent II is acetonitrile, ethanol, chloroform, or tetrahydrofuran.

7. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to any one of claims 2-6, characterized in that, The demethylation reaction is carried out by mixing bidentate ligand 2 with hydrobromic acid, wherein the molar concentration of bidentate ligand 2 in hydrobromic acid is 0.1-0.5 mol / L, and reacting at 60-100 °C for 6-24 h.

8. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to claim 2, characterized in that, The complexation reaction is performed by dissolving bidentate ligand 2 or bidentate ligand 3 and cobalt precursor in solvent III and reacting at room temperature for 6-24 h; the molar ratio of bidentate ligand 2 or bidentate ligand 3 to cobalt precursor is 1:1-1.5, and the ratio of bidentate ligand 2 or bidentate ligand 3 to solvent III is 0.01-0.1 mmol / mL.

9. The method for preparing the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group according to claim 8, characterized in that, The cobalt precursor is cobalt chloride; the solvent III is acetonitrile, ethanol, chloroform or tetrahydrofuran.

10. The application of the bidentate cobalt complex containing an imidazo[1,2-α]pyridine group as a metal catalyst in hydrosilylation, as described in claim 1, is characterized in that... The raw materials for the hydrosilylation reaction are styrene and diphenylsilane, and the products include the anti-Markovnikov hydrosilylation products of styrene.

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