Preparation method of 1, 5-cyclooctadiene iridium chloride dimer catalyst

Abstract

The present invention relates to the technical field of catalysts, and discloses a 1, 5-cyclooctadiene iridium chloride dimer catalyst preparation method, which comprises: (1) adding an iridium precursor to an alcohol, adding a hydrochloric acid solution, adding 1, 5-cyclooctadiene while carrying out a heating stirring reaction, and filtering after the reaction to obtain a 1, 5-cyclooctadiene iridium dichlorohydride dimer; and (2) adding the 1, 5-cyclooctadiene iridium dichlorohydride dimer into water, then adding an alkaline substance and alcohol, carrying out a stirring reaction under the assistance of ultrasonic waves, and filtering after the reaction to obtain the 1, 5-cyclooctadiene iridium chloride dimer. According to the method, the hydrochloric acid is added to enable the reaction to be carried out in the direction of generating the intermediate product, the obtained intermediate product and the alkaline substance are subjected to the dehydrochlorination reaction, the reaction time can be shortened under the action of ultrasonic waves, and finally the high-purity 1, 5-cyclooctadiene iridium chloride dimer can be obtained at a relatively high yield.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a method for preparing a 1,5-cyclooctadiene iridium chloride dimer catalyst. Background Art

[0002] As an important type of catalytic material, iridium has been widely used in the chemical, pharmaceutical, and electronic industries. For example, in drug synthesis and fine chemical synthesis, iridium catalysts can be used for CH bond activation reactions, hydrogenation reactions, olefin addition reactions, etc., which can increase the reaction rate and selectivity, and improve the purity and yield of the product; in fuel cells, iridium catalysts can be used to catalyze oxygen reduction reactions, improve the efficiency and stability of fuel cells; in hydrogen energy, iridium can catalyze the electrolysis of water to produce hydrogen. With the rapid development of related industries in China, the demand for special platinum group metal catalytic materials is increasing, and iridium is an extremely rare and expensive metal. Therefore, people are constantly exploring the synthesis method of high-yield, high-purity iridium catalysts to improve the utilization rate of iridium resources.

[0003] 1,5-Cyclooctadiene iridium chloride dimer ([Ir(C8H 12 )Cl]2) is an important iridium catalyst. Due to its unique catalytic properties, it is widely used in various organic synthesis reactions in drug synthesis and fine chemical industries. When used, it is usually coordinated with various organic ligands to form chiral iridium homogeneous catalysts to play an asymmetric catalytic role, such as allylic asymmetric alkylation, synthesis of hydrogen transfer chiral alcohols, Suzuki-Miyaura coupling reaction, alkylation of carbonyl compounds, cycloaddition reaction, hydroalkylation and hydroarylation, etc. It has the characteristics of high yield and high corresponding selectivity for specific reactions.

[0004] 1,5-cyclooctadiene iridium chloride dimer is generally obtained by a one-step reaction of a soluble iridium precursor and an excess of 1,5-cyclooctadiene in a solution. Günter Winkhaus (Chem. Ber., 1966, 99, 3610) first reported the reaction of sodium chloroiridate and 1,5-cyclooctadiene in alcohol to obtain [Ir(C8H 12 )Cl]2, a series of subsequent related literature reported similar synthesis methods (Inorganic Syntheses, 1974, 15, 18; Inorg. Chem. 1993, 32, 3347; Inorg. Chim. Acta, 2006, 359, 3800; Org. Chem. Front., 2018, 5, 46, etc.), with a yield between 66-85%. In practical applications, the yield of the above method is relatively low.

[0005] The invention patent with publication number US6399804 discloses that iridium trichloride or iridium tetrachloride and alcohols with different carbon chain lengths are used as solvents, with a yield of 81%. The invention patent with publication number JP2006045089 discloses that isopropanol and water are used as reaction solvents, and after the reaction is completed, the reaction solution is concentrated and then a large amount of water is added to precipitate the product, with a maximum yield of 98%. The invention patent with application number CN201610668837.2 discloses that aldehyde is used as a reaction solvent, which can shorten the reaction time and have a yield of 75%. The invention patent with application number CN201910490325.5 discloses that a strong reducing agent is added to the reaction to replace alcohol reduction, with a yield of more than 99%. The above high-yield synthesis methods generally use concentrated crystallization or aqueous phase precipitation method, but 1,5-cyclooctadiene iridium chloride in solution is extremely sensitive to air (Inorg. Chim. Acta, 1986, 120, 153). Trace amounts of oxygen will generate oxidation products Ir2Cl2(COD)(μ2-OH)2((μ2O), affecting product quality.

[0006] Robert H.Crabtree (J.Organomet.Chem., 1977, 135, 395) reported that chloroiridic acid and 1,5-cyclooctadiene reacted to first generate [IrHCl2(COD)]2, and then reacted under the action of sodium acetate for 24 hours to obtain [IrCl(COD)]2, with a total yield of 90-95%. However, this method can only use chloroiridic acid as a raw material, the reaction time is long, and recrystallization purification is required, and the steps are relatively complicated.

[0007] The monovalent iridium compound 1,5-cyclooctadiene iridium chloride dimer is synthesized using trivalent iridium or tetravalent iridium compounds as raw materials. The excess chlorine in the reaction will combine with hydrogen to form HCl in the reaction solution, which partially reacts with [Ir(C8H 12 )Cl]2 addition to generate [IrHCl2(C8H 12 )]2, resulting in a decrease in yield and affecting product purity. Therefore, it is urgent to develop a [Ir(C8H 12 )Cl]2 synthesis method. Summary of the invention

[0008] In order to solve the technical problems of long reaction time, easy oxidation in the product separation and crystallization process and low purity in the existing 1,5-cyclooctadiene iridium chloride dimer synthesis method, the present invention provides a method for preparing a 1,5-cyclooctadiene iridium chloride dimer catalyst, which utilizes chemical reaction equilibrium to synthesize the intermediate product [IrHCl2(C8H 12 )]2, and then ultrasonic-assisted dehydrochlorination to obtain [Ir(C8H 12)Cl]2, the method can broaden the applicable scope of the substrate, avoid the mixing of hydrogen chloride adducts in 1,5-cyclooctadiene iridium chloride dimer, high raw material utilization rate, and can obtain high-purity products.

[0009] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a method for preparing a 1,5-cyclooctadiene iridium chloride dimer catalyst, comprising the following steps: (1) adding an iridium precursor to an alcohol, then adding a hydrochloric acid solution, then adding 1,5-cyclooctadiene while heating and stirring for reaction, filtering after the reaction to obtain 1,5-cyclooctadiene iridium dichlorohydride dimer; (2) Adding 1,5-cyclooctadiene iridium dichloride dimer to water, then adding alkaline substances and alcohol, stirring and reacting under the assistance of ultrasonic waves, filtering after the reaction, and obtaining 1,5-cyclooctadiene iridium chloride dimer.

[0010] The invention synthesizes 1,5-cyclooctadiene iridium chloride dimer with high yield and high purity through a two-step reaction. In the first step, a chlorine-containing iridium compound is used as a raw material to react with 1,5-cyclooctadiene in an alcohol solvent containing hydrochloric acid, wherein the alcohol is simultaneously used as a reaction solvent and a reducing agent to obtain an intermediate product, 1,5-cyclooctadiene iridium dichloride dimer, and the addition of hydrochloric acid is conducive to the reaction proceeding in the direction of generating the intermediate product. In the second step, the intermediate product is added to an alcohol-water mixed solvent, an alkaline substance is added, and the intermediate product reacts with the base to eliminate hydrogen chloride to obtain the 1,5-cyclooctadiene iridium chloride dimer, and ultrasonic assistance is conducive to the efficient dehydrochlorination reaction and shortens the reaction time.

[0011] Compared with the existing synthesis method, the present invention promotes the chemical equilibrium to the direction of generating intermediate products by adding hydrochloric acid, inhibits the generation of 1,5-cyclooctadiene iridium chloride dimer, so that this step of reaction only generates a very small amount of 1,5-cyclooctadiene iridium chloride dimer, thereby improving the yield of the intermediate product. The intermediate product is then dehydrochlorinated to prepare 1,5-cyclooctadiene iridium chloride dimer, without the need for recrystallization and purification, and 1,5-cyclooctadiene iridium chloride dimer can be directly obtained, thereby greatly improving the yield and purity of the product. In addition, the preparation method is applicable to a variety of iridium raw materials, and the intermediate product is relatively stable in solution or air, and is easy to industrialize.

[0012] The specific reaction equation is (taking chloroiridic acid as an example): In formula (a), C8H 12 is 1,5-cyclooctadiene; formula (b) is the equation for preparing 1,5-cyclooctadiene iridium chloride dimer by dehydrochlorination reaction of 1,5-cyclooctadiene dichloroiridium dimer.

[0013] Preferably, in step (1), the iridium precursor is chloroiridic acid, hydrated iridium trichloride, iridium tetrachloride, sodium hexachloroiridate or ammonium chloroiridate; more preferably chloroiridic acid or hydrated iridium trichloride. When the iridium precursor is chloroiridic acid, it is generally added to the reaction in the form of a chloroiridic acid solution.

[0014] A small amount of hydrochloric acid is also produced during the conventional one-step method for preparing 1,5-cyclooctadiene iridium chloride dimer, thereby generating a small amount of intermediate products, resulting in a low yield of 1,5-cyclooctadiene iridium chloride dimer. However, the present invention promotes the generation of intermediate products by adding hydrochloric acid during the first step reaction, so that the raw materials are almost completely converted into intermediate products, and then an alkaline substance is added in the second step reaction for dehydrochlorination to obtain high-purity 1,5-cyclooctadiene iridium chloride dimer with a high yield. If an alkaline substance is directly added to the system after the first step reaction for dehydrochlorination, some impurities will co-precipitate, affecting the purity of the final product.

[0015] Preferably, in step (1), the molar ratio of the iridium element in the iridium precursor, 1,5-cyclooctadiene and HCl in the hydrochloric acid solution is 1:2-5:2-6.

[0016] Preferably, in step (1), the ratio of the iridium content in the iridium precursor to the amount of alcohol added is 1 g: 10-15 mL.

[0017] Preferably, in step (1), the iridium precursor, alcohol and hydrochloric acid solution are mixed, wherein the volume ratio of the alcohol to water is 3 to 4:1.

[0018] Preferably, in step (1), the alcohol is methanol, ethanol, n-propanol or isopropanol; more preferably isopropanol or ethanol.

[0019] Preferably, in step (1), the temperature of the heating and stirring reaction is 70 to 90° C., and the time is 4 to 7 hours.

[0020] Preferably, in step (2), the ratio of the added amount of the 1,5-cyclooctadiene iridium dichlorohydride dimer to water is 1 g: 2-4 mL.

[0021] Preferably, in step (2), the alkaline substance is sodium bicarbonate, sodium carbonate, potassium carbonate, anhydrous sodium acetate or disodium hydrogen phosphate; more preferably sodium bicarbonate or anhydrous sodium acetate; the molar ratio of the alkaline substance to 1,5-cyclooctadiene dichlorohydridoiridium dimer is 1 to 4:1.

[0022] Preferably, in step (2), the alcohol is methanol, ethanol, n-propanol or isopropanol; more preferably methanol or ethanol; the volume ratio of the alcohol to water is 1:5-10.

[0023] Preferably, in step (2), the stirring reaction is carried out at room temperature for 2 to 3 hours.

[0024] Preferably, the reaction processes in step (1) and step (2) are carried out under nitrogen protection, and the reaction solvent, water and alcohol used are deoxygenated by nitrogen bubbling before use.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) using a chlorine-containing iridium compound as a raw material and reacting it with 1,5-cyclooctadiene in an alcohol solvent containing hydrochloric acid, wherein the addition of hydrochloric acid is conducive to the reaction in the direction of generating an intermediate product, and obtaining an intermediate product, 1,5-cyclooctadiene dichlorohydridoiridium dimer, in a high yield; (2) then adding alkaline substances and the intermediate products to undergo dehydrochlorination reaction, and ultrasonic assistance can promote efficient dehydrochlorination reaction and shorten the reaction time; (3) The present invention can effectively avoid the problems of long reaction time, easy oxidation during product separation and recrystallization, and low purity in the conventional one-step synthesis process. The iridium content of the obtained 1,5-cyclooctadiene iridium chloride dimer is ≥56.6%, the yield is above 90%, and the purity is above 99%. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] The preparation of the 1,5-cyclooctadiene iridium chloride dimer catalyst of the present invention comprises the following steps: (1) An iridium precursor is added to an alcohol, and then a hydrochloric acid solution is added, and then 1,5-cyclooctadiene is added under stirring conditions, wherein the molar ratio of the iridium element in the iridium precursor, 1,5-cyclooctadiene and HCl in the hydrochloric acid solution is 1:2-5:2-6, and heating is turned on at the same time. After the addition is completed and the temperature is raised to 70-90° C., the temperature is maintained and stirred for reaction for 4-7 hours; after the reaction, the precipitate is concentrated by vacuum distillation, cooled and filtered, and the obtained precipitate is washed and dried in turn to obtain 1,5-cyclooctadiene dichloroiridium dimer [IrHCl2(C8H 12 )]2; (2) Adding 1,5-cyclooctadiene dichloroiridium dimer to water, and then adding alkaline substances and alcohol, wherein the molar ratio of the alkaline substances to 1,5-cyclooctadiene dichloroiridium dimer is 1 to 4:1, and the volume ratio of the alcohol to water is 1:5 to 10; stirring the reaction at room temperature under the assistance of ultrasonic wave and under the protection of nitrogen, and the reaction time is 2 to 3 hours; filtering the precipitate after the reaction, and then washing and drying the precipitate in turn to obtain 1,5-cyclooctadiene iridium chloride dimer [Ir(C8H 12 )Cl]2.

[0028] In a specific embodiment of the present invention, in step (1), the iridium precursor is chloroiridic acid, hydrated iridium trichloride, iridium tetrachloride, sodium hexachloroiridate or ammonium chloroiridate.

[0029] In a specific embodiment of the present invention, in step (1), the alcohol is methanol, ethanol, n-propanol or isopropanol, more preferably isopropanol or ethanol.

[0030] In a specific embodiment of the present invention, in step (1), the ratio of the iridium content in the iridium precursor to the amount of alcohol added is 1 g: 10-15 mL. The iridium precursor, alcohol and hydrochloric acid solution are mixed, wherein the volume ratio of alcohol to water added is 3-4:1.

[0031] In a specific embodiment of the present invention, in step (2), the alkaline substance is sodium bicarbonate, sodium carbonate, potassium carbonate, anhydrous sodium acetate or disodium hydrogen phosphate.

[0032] In a specific embodiment of the present invention, in step (2), the alcohol is methanol, ethanol, n-propanol or isopropanol, more preferably methanol or ethanol.

[0033] In a specific embodiment of the present invention, the reaction processes in step (1) and step (2) are carried out under nitrogen protection, and the reaction solvent, water and alcohol used are deoxygenated by nitrogen bubbling before use.

[0034] Example 1 (1) Add 6.4 g of iridium chloride solution (containing iridium 1.92 g, 10 mmol) and 20 mL of isopropanol to a reaction bottle, replace nitrogen gas under reduced pressure for 3 times, then add 7 mL of hydrochloric acid solution (2 mL of 36% concentrated hydrochloric acid + 5 mL of deionized water, containing 24 mmol of HCl), add 4.3 g (40 mmol) of 1,5-cyclooctadiene under stirring, and turn on heating at the same time. After the addition is completed and the temperature is raised to 80°C, maintain the temperature, stir and react for 5 hours, and generate a large amount of white precipitate. Concentrate by vacuum distillation, cool and filter, wash the obtained precipitate with anhydrous ethanol, and vacuum dry at 50°C to obtain 7.0 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0035] (2) 7.0 g of 1,5-cyclooctadiene dichloroiridium dimer and 20 mL of deionized water were mixed in a reaction flask, 2 mL of ethanol and 1.7 g (20 mmol) of sodium bicarbonate powder were added, the reaction flask was placed in an ultrasonic water bath with an ultrasonic frequency of 40 kHz, and stirred at room temperature for 2 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50°C to obtain 6.3 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 93.8%, an iridium content of 56.72%, a purity of 99.1%, and elemental analysis of C: 28.39%, H: 3.64%, which is consistent with the literature data.

[0036] Example 2 (1) 3.6 g of hydrated iridium trichloride (containing 1.92 g of iridium, 10 mmol) and 20 mL of isopropanol were added to a reaction bottle, and the nitrogen was replaced by reduced pressure for 3 times. Then, 9 mL of hydrochloric acid solution (4 mL of 36% concentrated hydrochloric acid + 5 mL of deionized water, containing 48 mmol of HCl) was added, and the mixture was heated to 50°C and stirred to dissolve. Then, 4.3 g (40 mmol) of 1,5-cyclooctadiene was added under stirring, and the mixture was heated continuously. After the addition was completed and the temperature was raised to 80°C, the temperature was maintained, and the reaction was stirred for 5 hours to generate a large amount of white precipitate. The mixture was concentrated by reduced pressure distillation, cooled and filtered, and the precipitate was washed with anhydrous ethanol and dried under vacuum at 50°C to obtain 6.9 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0037] (2) 6.9 g of 1,5-cyclooctadiene dichloroiridium dimer and 20 mL of deionized water were mixed in a reaction flask, 2 mL of ethanol and 1.7 g (20 mmol) of sodium bicarbonate powder were added, the reaction flask was placed in an ultrasonic water bath with an ultrasonic frequency of 40 kHz, and stirred at room temperature for 2 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50°C to obtain 6.2 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 92.3%, an iridium content of 56.74%, a purity of 99.1%, and elemental analysis of C: 28.35%, H: 3.62%, which is consistent with the literature data.

[0038] Example 3 (1) 4.5 g of ammonium hexachloroiridate (containing 1.92 g of iridium, 10 mmol) and 20 mL of isopropanol were added to a reaction flask, and the nitrogen was replaced by decompression for 3 times. Then, 10 mL of hydrochloric acid solution (5 mL of 36% concentrated hydrochloric acid + 5 mL of deionized water, containing 60 mmol of HCl) was added, and the mixture was heated to 50° C. and stirred to dissolve. Then, 4.3 g (40 mmol) of 1,5-cyclooctadiene was added under stirring, and the mixture was heated continuously. After the addition was completed and the temperature was raised to 80° C., the temperature was maintained, and the reaction was stirred for 5 h to generate a large amount of white precipitate. The mixture was concentrated by decompression distillation, cooled and filtered, and the precipitate was washed with anhydrous ethanol and dried under vacuum at 50° C. to obtain 6.8 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0039] (2) 6.8 g of 1,5-cyclooctadiene iridium dichloride dimer and 20 mL of deionized water were mixed in a reaction flask, 2 mL of ethanol and 3.4 g (40 mmol) of sodium bicarbonate powder were added, the reaction flask was placed in an ultrasonic water bath with an ultrasonic frequency of 40 kHz, and stirred at room temperature for 2 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50°C to obtain 6.1 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 90.8%, an iridium content of 56.90%, a purity of 99.4%, and elemental analysis of C: 28.33%, H: 3.63%, which is consistent with the literature data.

[0040] Example 4 (1) 6.4 g of iridium chloride solution (containing iridium 1.92 g, 10 mmol) and 20 mL of isopropanol were added to a reaction flask, and the nitrogen was replaced by decompression for 3 times. Then 7 mL of hydrochloric acid solution (2 mL of 36% concentrated hydrochloric acid + 5 mL of deionized water, containing 24 mmol of HCl) was added, and 2.2 g (20 mmol) of 1,5-cyclooctadiene was added under stirring, and heating was turned on at the same time. After the addition was completed and the temperature was raised to 75°C, the temperature was maintained and stirred for 6 hours to generate a large amount of white precipitate. The precipitate was concentrated by vacuum distillation, cooled and filtered, and the obtained precipitate was washed with anhydrous ethanol and dried in vacuo at 50°C to obtain 6.8 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0041] (2) 6.8 g of 1,5-cyclooctadiene iridium dichloride dimer and 20 mL of deionized water were mixed in a reaction flask, 2 mL of ethanol and 2.5 g (30 mmol) of anhydrous sodium acetate powder were added, the reaction flask was placed in an ultrasonic water bath, the ultrasonic frequency was 40 kHz, and the reaction was stirred at room temperature for 3 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50° C. to obtain 6.1 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 90.8%, an iridium content of 56.83%, and a purity of 99.3%.

[0042] Example 5 (1) 6.4 g of iridium chloride solution (containing iridium 1.92 g, 10 mmol) and 30 mL of isopropanol were added to a reaction flask, and the nitrogen was replaced by decompression for 3 times. Then 12 mL of hydrochloric acid solution (2 mL of 36% concentrated hydrochloric acid + 10 mL of deionized water, containing 24 mmol of HCl) was added, and 4.3 g (40 mmol) of 1,5-cyclooctadiene was added under stirring, and heating was turned on at the same time. After the addition was completed and the temperature was raised to 90°C, the temperature was maintained and stirred for 7 hours to generate a large amount of white precipitate. The precipitate was concentrated by vacuum distillation, cooled and filtered, and the obtained precipitate was washed with anhydrous ethanol and dried under vacuum at 50°C to obtain 6.9 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0043] (2) 6.9 g of 1,5-cyclooctadiene iridium dichloride dimer and 20 mL of deionized water were mixed in a reaction flask, 4 mL of methanol and 1.1 g (10.4 mmol) of sodium carbonate powder were added, the reaction flask was placed in an ultrasonic water bath, the ultrasonic frequency was 40 kHz, and the reaction was stirred at room temperature for 3 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50° C. to obtain 6.2 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 92.2%, an iridium content of 56.66%, and a purity of 99.0%.

[0044] Comparative Example 1 The difference from Example 1 is that hydrochloric acid is not added in step (1).

[0045] (1) Add 6.4 g of iridium chloride solution (containing iridium 1.92 g, 10 mmol) and 20 mL of isopropanol to a reaction bottle, replace nitrogen under reduced pressure for 3 times, then add 5 mL of deionized water, add 4.3 g (40 mmol) of 1,5-cyclooctadiene under stirring, and turn on heating at the same time. After the addition is completed and the temperature is raised to 80°C, maintain the temperature and stir the reaction for 5 hours to generate a large amount of white precipitate. Concentrate by vacuum distillation, cool and filter, wash the obtained precipitate with anhydrous ethanol, and vacuum dry at 50°C to obtain 5.0 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0046] (2) 5.0 g of 1,5-cyclooctadiene iridium dichloride dimer and 15 mL of deionized water were mixed in a reaction flask, 2 mL of ethanol and 1.3 g (15.5 mmol) of sodium bicarbonate powder were added, the reaction flask was placed in an ultrasonic water bath, the ultrasonic frequency was 40 kHz, and the reaction was stirred at room temperature for 2 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50° C. to obtain 4.4 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 65.5%, an iridium content of 56.72%, and a purity of 99.1%.

[0047] Comparative Example 2 The difference from Example 1 is that the amount of hydrochloric acid added in step (1) is too small (lower than the limit amount in the claims).

[0048] (1) Add 6.4 g of iridium chloride solution (containing iridium 1.92 g, 10 mmol) and 20 mL of isopropanol to a reaction bottle, replace nitrogen gas under reduced pressure for 3 times, then add 6 mL of hydrochloric acid solution (1 mL of 36% concentrated hydrochloric acid + 5 mL of deionized water, containing 12 mmol of HCl), add 4.3 g (40 mmol) of 1,5-cyclooctadiene under stirring, and turn on heating at the same time. After the addition is completed and the temperature is raised to 80°C, maintain the temperature, stir and react for 5 hours, and generate a large amount of white precipitate. Concentrate by vacuum distillation, cool and filter, wash the obtained precipitate with anhydrous ethanol, and vacuum dry at 50°C to obtain 6.3 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0049] (2) 6.3 g of 1,5-cyclooctadiene iridium dichloride dimer and 20 mL of deionized water were mixed in a reaction flask, 2 mL of ethanol and 1.7 g (20 mmol) of sodium bicarbonate powder were added, the reaction flask was placed in an ultrasonic water bath, the ultrasonic frequency was 40 kHz, and the reaction was stirred at room temperature for 2 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and vacuum dried at 50° C. to obtain 5.6 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 83.4%, an iridium content of 56.68%, and a purity of 99.0%.

[0050] Comparative Example 3 The difference from Example 1 is that the dehydrochlorination reaction process in step (2) does not use ultrasonic assistance.

[0051] (1) Add 6.4 g of iridium chloride solution (containing iridium 1.92 g, 10 mmol) and 20 mL of isopropanol to a reaction flask, replace nitrogen under reduced pressure 3 times, then add 7 mL of hydrochloric acid solution (2 mL of 36% concentrated hydrochloric acid + 5 mL of deionized water, containing 24 mmol of HCl), add 4.3 g (40 mmol) of 1,5-cyclooctadiene under stirring, and turn on heating at the same time. After the addition is completed and the temperature is raised to 80°C, maintain the temperature, stir and react for 5 hours, and generate a large amount of white precipitate. Concentrate by vacuum distillation, cool and filter, wash the obtained precipitate with anhydrous ethanol, and vacuum dry at 50°C to obtain 7.0 g of off-white 1,5-cyclooctadiene dichlorohydridoiridium dimer.

[0052] (2) 7.0 g of 1,5-cyclooctadiene dichloroiridium dimer and 20 mL of deionized water were mixed in a reaction bottle, 2 mL of ethanol and 1.7 g (20 mmol) of sodium bicarbonate powder were added, and the mixture was stirred at room temperature for 24 h under a nitrogen atmosphere, and the white precipitate turned orange-red. The precipitate was filtered, washed with deionized water and anhydrous ethanol respectively, and dried under vacuum at 50° C. to obtain 6.2 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder, with a yield of 92.3%, an iridium content of 56.14%, a purity of 98.1%, and elemental analysis of C: 28.28%, H: 3.70%, which was consistent with the literature data.

[0053] Comparative Example 4 The difference from Example 2 is that hydrochloric acid is not added.

[0054] 3.6 g of hydrated iridium trichloride (containing iridium 1.92 g, 10 mmol), 10 mL of deionized water and 20 mL of isopropanol were added to a reaction bottle, and the nitrogen was replaced by reduced pressure for 3 times. The reaction was heated to 50° C. and stirred to dissolve. Then, 4.3 g (40 mmol) of 1,5-cyclooctadiene was added and stirred rapidly. After the addition was completed, the temperature was continued to rise to 80° C. under nitrogen protection, and the reaction was stirred for 24 hours to generate an orange-red precipitate. The precipitate was cooled to room temperature, filtered to obtain the precipitate, and then washed with deionized water and anhydrous ethanol respectively, and dried in vacuo at 50° C. to obtain 5.6 g of orange-red 1,5-cyclooctadiene iridium chloride dimer powder with a yield of 83.3%, an iridium content of 56.37%, and a purity of 98.5%.

[0055] Table 1 As shown in Table 1, hydrochloric acid is added in the first step of the reaction to promote the reaction to generate an intermediate product, and 1,5-cyclooctadiene dichloroiridium dimer [IrH(C8H 12 )Cl2]2, and then ultrasonic-assisted dehydrochlorination was used to obtain 1,5-cyclooctadiene iridium chloride dimer [Ir(C8H 12 )Cl]2. In Examples 1-5, different iridium precursors are used for two-step synthesis, and high-yield and high-purity 1,5-cyclooctadiene iridium chloride dimer can be obtained. The results show that the synthesis method of the present invention can not only broaden the substrate range and improve the utilization rate of raw materials, but also avoid the mixing of hydrogen chloride adducts in 1,5-cyclooctadiene iridium chloride dimer, and can obtain high-purity and high-yield products.

[0056] Comparative Example 1 is that hydrochloric acid is not added in the first step of the reaction, and chloroiridic acid solution is used as a raw material. A small amount of hydrochloric acid will be generated during the reaction, but the yield of the intermediate product obtained in the first step of the reaction is greatly reduced due to insufficient acidity, thereby affecting the overall yield. Similarly, in the first step of the reaction of Comparative Example 2, due to the lack of sufficient hydrochloric acid, the reaction conversion is incomplete, and the yields of the intermediate product and 1,5-cyclooctadiene iridium chloride dimer are both low. Comparative Example 3 is that ultrasound is not assisted during the second step of the reaction, and the reaction can also be carried out, but the reaction time is significantly prolonged, indicating that ultrasound assistance is conducive to the efficient dehydrochlorination reaction and shortens the reaction time.

[0057] Comparative Example 4 uses hydrated iridium trichloride as the iridium precursor for one-step synthesis, i.e., no hydrochloric acid is added during the first step of the reaction, the reaction time is significantly prolonged, and compared with Example 2 which also uses hydrated iridium trichloride as the iridium precursor for the reaction, the yield and purity of the obtained product are significantly reduced.

[0058] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a 1,5-cyclooctadiene iridium chloride dimer catalyst, characterized in that: The steps include: (1) adding an iridium precursor to an alcohol, then adding a hydrochloric acid solution, then adding 1,5-cyclooctadiene while heating and stirring to react, filtering after the reaction to obtain 1,5-cyclooctadiene dichlorohydridoiridium dimer; (2) Add 1,5-cyclooctadiene iridium dichloride dimer into water, then add alkaline substances and alcohol, stir and react under the assistance of ultrasonic wave, and filter after the reaction to obtain 1,5-cyclooctadiene iridium chloride dimer.

2. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1, characterized in that: In step (1), the molar ratio of the iridium element in the iridium precursor, 1,5-cyclooctadiene and HCl in the hydrochloric acid solution is 1:2-5:2-6.

3. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1, characterized in that: In step (1), the temperature of the heating and stirring reaction is 70-90° C. and the time is 4-7 hours.

4. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to any one of claims 1 to 3, characterized in that: In step (1), the iridium precursor is chloroiridic acid, hydrated iridium trichloride, iridium tetrachloride, sodium hexachloroiridate or ammonium chloroiridate.

5. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to any one of claims 1 to 3, characterized in that: In step (1), the alcohol is methanol, ethanol, n-propanol or isopropanol.

6. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1, characterized in that: In step (2), the alkaline substance is sodium bicarbonate, sodium carbonate, potassium carbonate, anhydrous sodium acetate or disodium hydrogen phosphate.

7. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1 or 6, characterized in that: In step (2), the molar ratio of the alkaline substance to 1,5-cyclooctadiene dichloroiridium dimer is 1-4:

1.

8. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1, characterized in that: In step (2), the stirring reaction is carried out at room temperature for 2 to 3 hours.

9. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1 or 8, characterized in that: In step (2), the alcohol is methanol, ethanol, n-propanol or isopropanol.

10. The method for preparing the 1,5-cyclooctadiene iridium chloride dimer catalyst according to claim 1, characterized in that: The reaction processes in step (1) and step (2) are all carried out under nitrogen protection, and the reaction solvent, water and alcohol used are all deoxygenated by nitrogen bubbling before use.

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