A pyrazole bridged phosphine ligand, its binuclear complex and application thereof

Abstract

The application discloses a pyrazole bridged phosphine ligand, a binuclear complex thereof and application, and belongs to the field of metal organic synthesis, and a structural formula of the pyrazole bridged phosphine ligand is shown as formula (4), wherein R1 is selected from hydrogen, a substituted or unsubstituted alkyl, a substituted or unsubstituted alkoxy, a substituted or unsubstituted aromatic group or an aromatic group derivative, and R2 is selected from a substituted or unsubstituted aromatic group or an aromatic group derivative. The ligand has higher electron density at a metal center, so that a pi backbonding is more easily formed, and thus activation of a double bond and a triple bond small molecule is more favorable. In addition, the application further provides a D3-pz-D3 type binuclear complex with the pyrazole bridged phosphine ligand as a ligand, which can be applied to alkyne polymerization, and catalytic reaction conditions are mild and economic efficiency is better.

Description

Technical Field

[0001] This invention relates to the field of organometallic synthesis technology, and in particular to a pyrazole-bridged phosphine ligand, its binuclear complexes, and their applications. Background Technology

[0002] In nature, many enzymes utilize two adjacent metal centers as their active sites to activate and transform small molecules. This allows them to perform chemical reactions crucial to human health under very mild conditions, exhibiting high selectivity and efficiency. This phenomenon has inspired numerous inorganic chemists to study these enzymes, hoping to understand the unique synergistic effects between binuclear metals and thus design more efficient, economical, and environmentally friendly catalysts.

[0003] The synergistic effect between binuclear metals plays a crucial role in the activation and transformation of small molecules. In the study of binuclear metal complexes, a commonly used strategy is to use a bridging group with two coordinating atoms as a ligand to synthesize the corresponding complex. However, pyrazole, due to its binuclear metal complex having a metal distance of... arrive The 3 and 5 positions are easily modified, making them highly favored. Although D1-pz-D1 type phosphine ligands and many D3-pz-D3 type nitrogen, oxygen, and sulfur ligands have been reported in recent decades, D1-pz-D1 type ligands tend to form 2:2 complexes, which is sterically unfavorable for the catalysis of small molecules. D3-pz-D3 type nitrogen, oxygen, and sulfur ligands, due to their harder ligand atoms and poorer electron-donating ability, mostly form divalent complexes and are primarily used for the hydrolysis of small molecules. However, pyrazole-bridged binuclear phosphine ligands and their corresponding low-valent complexes have never been reported. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a pyrazole-bridged phosphine ligand, a D3-pz-D3 type binuclear complex and its applications. The D3-pz-D3 type binuclear complex provided by this invention is particularly suitable for the catalysis of small molecules.

[0005] To achieve the above and other related objectives, a first aspect of the present invention provides a pyrazole-bridged phosphine ligand, the structural formula of which is shown below:

[0006]

[0007] Among them, R 1 Selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aromatic or aromatic derivatives;

[0008] R2 Selected from substituted or unsubstituted aromatic groups or aromatic derivatives.

[0009] A second aspect of the present invention provides a method for preparing the above-mentioned pyrazole-bridged phosphine ligand, the synthetic route of which is as follows:

[0010]

[0011] A third aspect of the present invention provides a D3-pz-D3 type binuclear complex, using a pyrazole-bridged phosphine ligand provided in the first aspect or prepared in the second aspect as the ligand.

[0012] A fourth aspect of the present invention provides an application of the D3-pz-D3 type binuclear complex in catalytic reactions, specifically, the application of the D3-pz-D3 type binuclear complex in the catalytic polymerization of alkynes; more specifically, the application of the D3-pz-D3 type binuclear complex in the catalytic dimerization of phenylacetylene. Attached Figure Description

[0013] Figure 1 The ligands developed for this invention 31 P NMR spectrum.

[0014] Figure 2 The ligands developed for this invention 1 H NMR spectrum.

[0015] Figure 3 The ligands developed for this invention 13 C NMR spectrum.

[0016] Figure 4 It is a dimerization product of phenylacetylene. 1 H NMR spectrum.

[0017] Figure 5 It is a dimer of 2-alkynyltoluene. 1 H NMR spectrum.

[0018] Figure 6 This is the single-crystal structure of the chloride ion-bridged binuclear CoI complex developed in this invention.

[0019] Figure 7 This is the hollow binuclear CoI complex single-crystal structure developed in this invention.

[0020] Figure 8 This is the single-crystal structure of the borohydride-bridged binuclear CoI complex developed in this invention.

[0021] Figure 9 This is the single-crystal structure of the borohydride-bridged binuclear FeI complex developed in this invention.

[0022] Figure 10This is the single-crystal structure of the chloride ion-bridged binuclear NiI complex developed in this invention.

[0023] Figure 11 This is the single-crystal structure of the chloride ion-bridged binuclear FeI complex developed in this invention.

[0024] Figure 12 This is the single-crystal structure of the binuclear CuI complex developed in this invention. Detailed Implementation

[0025] The inventors of this invention considered that the strong electron-donating ability of phosphine ligands can lead to higher electron density in the metal center, making it easier to form π-backbonds and thus more conducive to the activation of double and triple bonds in small molecules. Therefore, the aim was to develop a novel pyrazole-bridged phosphine ligand and its synthetic method, and a series of corresponding monovalent dinuclear complexes of iron, cobalt, nickel, and copper were successfully synthesized. Since phosphine ligands have excellent coordination ability with most transition metals, this ligand can be used not only to study dinuclear transition metal complexes, but also other first-series, and even second- and third-series transition metal complexes. Furthermore, research has shown that dinuclear complexes can be applied to alkyne polymerization, and compared to other ruthenium and palladium complexes with similar functions, cobalt is relatively inexpensive, thus offering better economic benefits. Based on these findings, this invention was completed.

[0026] The first aspect of this invention provides a pyrazole-bridged phosphine ligand, the structural formula of which is shown below:

[0027]

[0028] Among them, R 1 Selected from hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted aromatic groups or aromatic derivatives; R 2 Selected from substituted or unsubstituted aromatic groups or aromatic derivatives.

[0029] As described above, the ligand developed in this invention is a binuclear ligand. Compared to mononuclear metal complexes, binuclear metal complexes can provide more diverse coordination modes. It is also a multidentate ligand, and the chelation effect leads to an increase in entropy, resulting in complexes with higher stability. Highly stable complexes have wider applications. Furthermore, the ligand possesses four phosphine ligands with strong electron-donating capabilities, capable of coordinating with almost all transition metals. Therefore, it can coordinate with almost all transition metals, and the metal center has a higher electron density, which is beneficial for catalytic reactions.

[0030] In a preferred embodiment of the present invention, in the pyrazole-bridged phosphine ligand, the R 1Selected from hydrogen, alkyl groups with 1-5 carbon atoms, alkoxy groups with 1-5 carbon atoms, and aryl groups with 6-18 carbon atoms; R 2 The aromatic groups are selected from 6-18 carbon atoms. This invention aims to prepare a class of binuclear phosphine ligands, to which substituents can be introduced onto the pyrazole, depending on the application.

[0031] In a preferred embodiment of the present invention, the R 1 Selected from hydrogen, alkyl groups with 1-3 carbon atoms, alkoxy groups with 1-3 carbon atoms, and aryl groups with 6-12 carbon atoms, R 2 Selected from aromatic groups with 6-12 carbon atoms.

[0032] In a preferred embodiment of the present invention, the R 1 Selected from one of hydrogen, methyl, ethyl, methoxy, ethoxy, or phenyl, R 2 It is a phenyl group.

[0033] In a specific embodiment of the present invention, the pyrazole-bridged phosphine ligand is selected from the following structural formula:

[0034]

[0035] The second aspect of this invention provides a method for preparing the pyrazole-bridged phosphine ligand, the synthetic route of which is as follows:

[0036]

[0037] In the synthetic route: X is selected from Cl, Br, or I; R 1 Selected from hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted aromatic groups or aromatic derivatives; R 2 Selected from substituted or unsubstituted aromatic groups or aromatic derivatives.

[0038] Specifically, the synthesis steps are as follows: S1, reacting diethanolamine with 3,5-dihalomethylpyrazole hydrochloride (1) in the presence of a base to obtain tetrahydroxysubstituted pyrazole (2); S2, acidifying tetrahydroxysubstituted pyrazole (2) and then reacting it with thionyl chloride to obtain tetrachlorosubstituted pyrazole (3); S3, reacting tetrachlorosubstituted pyrazole (3) with substituted or unsubstituted diarylphosphine in the presence of a base to obtain pyrazole-bridged phosphine ligand (4).

[0039] In some specific embodiments of the present invention: S1, diethanolamine and 3,5-dihalomethylpyrazole hydrochloride (1) are reacted at 40°C to 80°C for 1 to 3 hours in the presence of an aprotic solvent and a base to obtain the corresponding tetrahydroxysubstituted pyrazole (2), wherein the molar ratio of 3,5-dihalomethylpyrazole hydrochloride (1) to diethanolamine is 1:4 to 8, preferably 1:5 to 7, more preferably 1:6; the molar ratio of 3,5-dihalomethylpyrazole hydrochloride (1) to the base is 1:5 to 10, preferably 1:6 to 8, more preferably 1:7. The aprotic solvent is selected from at least one of acetonitrile, dimethylformamide, or dimethyl sulfoxide, preferably acetonitrile. The base is selected from potassium carbonate or sodium carbonate, preferably sodium carbonate. Generally, purification is required after step S1. Specifically, the reaction system is filtered and subjected to vacuum extraction at 130°C to 160°C and 50 μmHg to 12 μmHg for 3 to 6 hours to remove excess diethanolamine from the product, thereby obtaining a high-purity tetrahydroxysubstituted pyrazole (2).

[0040] S2. After acidifying tetrahydroxy-substituted pyrazole (2), it is reacted with sulfoxide to obtain tetrachloro-substituted pyrazole (3). The acid used for acidifying tetrahydroxy-substituted pyrazole (2) is hydrogen chloride, preferably a hydrogen chloride diethyl ether solution, with a hydrogen chloride concentration of 0.5-2M, preferably 1M (mol / L). Preferably, the molar ratio of tetrahydroxy-substituted pyrazole (2) to hydrogen chloride is 1:1-4, and the molar ratio of tetrahydroxy-substituted pyrazole (2) to sulfoxide is 1:1-4. The specific reaction conditions are as follows: after acidification, tetrahydroxy-substituted pyrazole (2) is reacted with sulfoxide in the presence of a nonpolar solvent at a temperature of 80℃-100℃ for 3-5 hours. The preferred nonpolar solvent is diethyl ether.

[0041] S3, tetrachloro-substituted pyrazole (3) and substituted or unsubstituted diarylphosphine are reacted in the presence of a solvent at a temperature of 60℃~80℃ for 16~48h to obtain pyrazole-bridged phosphine ligand (4). The solvent is selected from polar solvents, preferably at least one of tetrahydrofuran, methanol or acetonitrile, wherein the molar ratio of tetrachloro-substituted pyrazole (3) to substituted or unsubstituted diarylphosphine is 1:4~8, preferably 1:4~5. The molar ratio of tetrachloro-substituted pyrazole (3) to base is 1:4~8, preferably 1:4.8~6.

[0042] A third aspect of the present invention provides a D3-pz-D3 type binuclear complex, wherein the general formula of the D3-pz-D3 type binuclear complex is [formula omitted]. Or [MNM]A;

[0043] Wherein, N is the pyrazole-bridged phosphine ligand provided or prepared above; M is selected from metal atoms or ions; Y is the bridging atom of the complex; and A is the anion. Since phosphine ligands have excellent coordination ability with most transition metals, our ligands can be used not only to study binuclear transition metal complexes but also other first-series, and even second- and third-series transition metal complexes. The ligands developed in this invention are binuclear ligands. Compared with mononuclear metal complexes, binuclear metal complexes can provide more diverse coordination modes, which are crucial for the activation and transformation of small molecules. The ligands developed in this invention are polydentate ligands, and the chelation effect can lead to an increase in entropy, resulting in higher stability of the complex, which is very important for the catalytic reaction itself. Furthermore, the ligand has four phosphine ligands with strong electron-donating ability that can coordinate with almost all transition metals, thus enabling coordination with almost all transition metals, and the metal center has a higher electron density, which is more favorable for reducing catalytic reactions.

[0044] In some specific embodiments of the present invention: M is selected from transition metal atoms or ions, preferably, M is selected from the first series of transition metal atoms or ions; more preferably, M is selected from iron, cobalt, nickel or copper atoms or ions, and Y is selected from Cl. - or BH4 - A is selected from BF4 - .

[0045] In a specific embodiment of the present invention: the D3-pz-D3 type binuclear complex is selected from the following structural formula:

[0046]

[0047] In another aspect of the invention, a method for preparing the above-mentioned complex is provided, wherein the target ligand is deprotonated by a strong base such as hexamethyldisilamide lithium or n-butyllithium, and then reacted with a corresponding divalent metal salt in an amount of 1 to 1.2 equivalents, followed by reduction with a reducing agent such as sodium amalgam to obtain the corresponding binuclear complex. Further reaction of the obtained binuclear complex with other reactants such as sodium borohydride yields other corresponding borohydride-bridged complexes.

[0048] The fourth aspect of this invention provides the application of the D3-pz-D3 type binuclear complex in catalytic reactions, particularly in the catalytic polymerization of alkynes, and even more particularly in the catalytic dimerization of phenylacetylene. In addition to the advantages of the ligands and complexes provided in this application mentioned above, the binuclear cobalt complex obtained by this invention catalyzes reactions at room temperature, resulting in mild catalytic conditions. Experiments have demonstrated that the borohydride-bridged binuclear monovalent cobalt complex can catalyze the polymerization of alkynes, and that cobalt metal is cheaper than previously reported ruthenium and palladium binuclear complexes.

[0049] The beneficial effects of the present invention are further illustrated below with reference to embodiments. To make the inventive objective, technical solution, and beneficial technical effects of the present invention clearer, the present invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of the present invention are merely for explaining the present invention and are not intended to limit the present invention, and the embodiments of the present invention are not limited to the embodiments given in the specification. Unless otherwise specified, specific experimental or operating conditions in the embodiments are prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0050] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0051] Unless otherwise specified, all reagents, materials and instruments used in the following embodiments are commercially available.

[0052] Example 1

[0053] Preparation of pyrazole-bridged binuclear diphenylphosphine ligand (4-1)

[0054] 1) Add 0.4 g of 3,5-dichloromethylpyrazole hydrochloride and 1.06 g of sodium carbonate to 50 ml of acetonitrile solution containing 1.26 g of diethanolamine, and stir at 80 °C for three hours; remove the solvent under reduced pressure, dissolve in 50 ml of methanol, filter, remove the solvent again, and then pump at 150 °C and 100 μm Hg for 4 hours. A white solid is obtained as the tetrahydroxy product.

[0055] 2) Dissolve the white solid in 50 ml of methanol, add 1 M HCl ether solution, stir for 10 minutes, then remove the solvent to obtain the acidified tetrahydroxy product. Add 10 ml of thionyl chloride to the acidified tetrahydroxy product, heat at 95 °C for 3 hours, then remove excess thionyl chloride under reduced pressure. Dissolve the obtained product in 50 ml of methanol, filter, and remove the methanol to obtain 1.15 g of yellow solid, which is the tetrachloro-substituted product.

[0056] 3) In a 150 ml Schleck flask, add 40 ml tetrahydrofuran and 2.24 g potassium tert-butoxide to form a suspension. Then add 1.5 ml diphenylphosphine and stir for 20 minutes. Next, add the resulting yellow solid and continue stirring at 80 °C for 16 hours. Stop heating and allow the reaction solution to cool to room temperature. Add 20 ml of 1 M dilute hydrochloric acid and stir for 10 minutes. Then add 30 ml water and 20 ml ethyl acetate, stir for 5 minutes, and filter. Separate the filtrate in a separatory funnel and extract the aqueous phase with 50 ml x 2 ethyl acetate. Mix the organic phase, wash with saturated brine, dry with anhydrous sodium sulfate, and remove the solvent to obtain a red oily substance. Separate the oily substance by silica gel column chromatography. The eluent ratio of petroleum ether:ethyl acetate:triethylamine is 4:1:0.01, yielding 0.375 g of a white solid, which is the pyrazole-bridged dinuclear diphenylphosphine ligand (4-1). Figure 1 Phosphine ligand (4-1) in CD2Cl2 31 p-NMR (162MHz) spectrum: 31 P{1H}NMR (162MHz, CD2Cl2, 298K): δ-20.67(s).

[0057] Figure 2 Phosphine ligands in CD2Cl2 1 H-NMR (400MHz) NMR spectrum: 1 H NMR (400MHz, CD2Cl2) δ7.47–7.23(m,40H),5.77(s,1H),3.59(s,4H),2.54(q,J=7.6Hz,8H),2.12(dd,J=9.4,6.0Hz,8H).

[0058] Figure 3 Phosphine ligands in CD2Cl2 13 C-NMR (101MHz) NMR spectrum: 13 C{1H}NMR(101MHz,Methylene Chloride-d2) δ 139.11 (d, J = 13.4Hz), 133.08 (d, J = 19.0Hz), 128.91, 128.81, 128.76, 104.23, 50.13 (d, J = 21.0Hz), 49.85, 25.88 (d, J = 11.9Hz).

[0059] Example 2

[0060] Preparation of pyrazole-bridged binuclear chloride ion-bridged monovalent cobalt complex (6)

[0061] 1) Weigh 40 mg of the obtained pyrazole-bridged dinuclear diphenylphosphine ligand (4-1) into a 20 ml sample bottle, add 10 ml of furan to dissolve it, then add 7.5 mg of hexamethyldisilamide lithium, stir for ten minutes, add 11 mg of anhydrous cobalt chloride, and continue stirring for 4 hours.

[0062] 2) Weigh 2.3 mg of sodium into a 20 ml sample vial and add 1 ml of tetrahydrofuran solution, then add 460 mg of mercury to form a gray suspension. The reaction solution from step 1) is then added to the freshly prepared sodium amalgam and stirred at room temperature for 16 hours.

[0063] 3) The reaction solution was filtered and the solvent was removed under reduced pressure. The product was then dissolved in toluene, filtered, and the toluene was removed. The product was then washed with pentane and dried to obtain 35 mg of reddish-brown powder, which was a pyrazole-bridged binuclear chloride ion-bridged monovalent cobalt complex.

[0064] Example 3

[0065] Preparation of pyrazole-bridged binuclear chloride-bridged monovalent iron complex (8)

[0066] 1) Weigh 40 mg of the obtained pyrazole-bridged dinuclear diphenylphosphine ligand (4-1) into a 20 ml sample bottle, add 10 ml of furan to dissolve it, then add 7.5 mg of hexamethyldisilamide lithium, stir for ten minutes, add 12 mg of anhydrous ferrous chloride, and continue stirring for 4 hours.

[0067] 2) Weigh 2.3 mg of sodium into a 20 ml sample vial and add 1 ml of tetrahydrofuran solution, then add 460 mg of mercury to form a gray suspension. The reaction solution from step 1) is then added to the freshly prepared sodium amalgam and stirred at room temperature for 16 hours.

[0068] 3) The reaction solution was filtered and the solvent was removed under reduced pressure. The product was then dissolved in toluene, filtered, and the toluene was removed. The product was then washed with pentane and dried to obtain 36 mg of black powder, which was a pyrazole-bridged binuclear chloride ion-bridged monovalent iron complex.

[0069] Example 4

[0070] Preparation of pyrazole-bridged binuclear chloride ion-bridged monovalent nickel complex (9)

[0071] 1) Weigh 40 mg of the obtained pyrazole-bridged dinuclear diphenylphosphine ligand (4-1) into a 20 ml sample bottle, add 10 ml of furan to dissolve it, then add 7.5 mg of hexamethyldisilamide lithium, stir for ten minutes, then add 9.1 mg of NiCl2·DME and 15 mg of Ni(COD)2, and continue stirring at room temperature for 16 hours.

[0072] 2) The reaction solution was filtered and the solvent was removed under reduced pressure. The product was then dissolved in toluene, filtered, and the toluene was removed. The product was then washed with pentane and dried to obtain 35 mg of red powder, which was a pyrazole-bridged binuclear chloride ion-bridged monovalent nickel complex.

[0073] Example 5

[0074] Preparation of pyrazole-bridged binuclear borohydride ion-bridged monovalent iron complex (11)

[0075] Weigh 20 mg of the black powder prepared in Example 3 into a 20 ml sample bottle, add 10 ml of tetrahydrofuran, then add 5 mg of sodium borohydride, stir at room temperature for 4 hours, filter, remove the solvent under reduced pressure, dissolve the product with toluene, filter, remove the solvent under reduced pressure, and obtain 15 mg of borohydride-bridged monovalent iron complex.

[0076] Example 6

[0077] Preparation of pyrazole-bridged binuclear hollow monovalent cobalt complex (10)

[0078] Weigh 20 mg of the red powder prepared in Example 1 into a 20 ml sample vial, add 10 ml of tetrahydrofuran, and then add NaBAr. F 16 mg was stirred at room temperature for 3 hours, filtered, the solvent was removed under reduced pressure, the product was dissolved in toluene, filtered, and the toluene was removed under reduced pressure to obtain 30 mg of hollow binuclear complex.

[0079] Example 7

[0080] Preparation of pyrazole-bridged binuclear borohydride ion-bridged monovalent cobalt complex (7)

[0081] Weigh 20 mg of the reddish-brown powder prepared in Example 2 into a 20 ml sample bottle, add 10 ml of tetrahydrofuran, then add 5 mg of sodium borohydride, stir at room temperature for 4 hours, filter, remove the solvent under reduced pressure to obtain 18 mg of borohydride-bridged complex.

[0082] Example 8

[0083] Weigh 10 mg of the borohydride-bridged complex prepared in Example 7 into a 20 ml bottle, add 10 ml of tetrahydrofuran, then add 1 ml of phenylacetylene, and stir at room temperature for four hours.

[0084] The solvent was removed from the reaction solution, which was then dissolved in pentane and separated by silica gel column chromatography with pure pentane as the eluent, yielding 18 mg of the dimer product.

[0085] phenylacetylene dimerization products in CDCl3 1 H-NMR (500MHz) NMR spectrum: 1H NMR(500MHz,Chloroform-d)δ7.66(dd,J=7.5,2.1Hz,2H),7.54(d,J=7.1Hz,2H),7.50–7.37(m,6H),7.20(d,J=16.2Hz,1H),6.54(d,J=16.2Hz,1H).

[0086] Example 9

[0087] Weigh 10 mg of the borohydride-bridged complex prepared in Example 7 into a 20 ml bottle, add 10 ml of tetrahydrofuran, then add 1 ml of 2-alkynyltoluene, and stir at room temperature for four hours.

[0088] The solvent was removed from the reaction solution, which was then dissolved in pentane and separated by silica gel column chromatography with pure pentane as the eluent, yielding 23 mg of dimer product.

[0089] 1H-NMR (500MHz) NMR spectrum of 2-alkynyltoluene dimer in CDCl3: 1H NMR (500MHz, Chloroform-d) δ 7.53–7.46 (m, 1H), 7.43 (d, J = 7.6Hz, 1H), 7.22 (d, J = 6.3Hz, 1H), 7.16 (ddt, J = 20.0, 13.3, 4.2Hz, 6H), 6.32 (d, J = 16.1Hz, 1H), 2.46 (s, 3H), 2.37 (s, 3H).

[0090] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A pyrazole-bridged phosphine ligand, the structural formula of which is shown in formula (4): ； in, R 1 Selected from hydrogen; R 2 Selected from aromatic groups with 6-18 carbon atoms.

2. The preparation method of the pyrazole-bridged phosphine ligand as described in claim 1, the synthetic route is as follows: ； Specifically, the synthesis steps include the following: S1. Diethanolamine was reacted with 3,5-dihalomethylpyrazole hydrochloride (1) in the presence of a base to obtain tetrahydroxysubstituted pyrazole (2). S2. After acidifying the tetrahydroxy-substituted pyrazole (2), it is reacted with thionyl chloride to obtain tetrachloro-substituted pyrazole (3). S3, Tetrachloro-substituted pyrazole (3) and HPR2 2 The reaction in the presence of a base yielded pyrazole-bridged phosphine ligands (4). In the synthetic route: X is selected from Cl, Br, or I; R 1 R 2 The definition is the same as that in claim 1.

3. The method for preparing the pyrazole-bridged phosphine ligand according to claim 2, characterized in that, The synthesis steps include one or more of the following technical features: In steps A1 and S1, the molar ratio of 3,5-dihalomethylpyrazole hydrochloride (1) to diethanolamine is 1:4~8, and the molar ratio of 3,5-dihalomethylpyrazole hydrochloride (1) to the base is 1:5~10. In steps A2 and S1, diethanolamine reacts with 3,5-dihalomethylpyrazole hydrochloride (1) in the presence of a solvent at a temperature of 40°C to 80°C. In steps A3 and S1, the base is selected from potassium carbonate or sodium carbonate. In steps A4 and S2, the acid used for the acidification of tetrahydroxysubstituted pyrazole (2) is hydrogen chloride; In steps A5 and S2, after the tetrahydroxy-substituted pyrazole (2) is acidified, it reacts with thionyl chloride in the presence of a solvent at a temperature of 80℃~100℃ for 3-5 hours. In steps A6 and S3, tetrachlorosubstituted pyrazole (3) reacts with HPR2. 2 The molar ratio is 1:4~8, and the molar ratio of the tetrachlorosubstituted pyrazole (3) to the base is 1:4~8; In steps A7 and S3, tetrachlorosubstituted pyrazole (3) reacts with HPR2. 2 In the presence of a solvent, the reaction is carried out at a temperature of 60℃~80℃ for 16~48h to obtain pyrazole-bridged phosphine ligands (4), wherein the solvent is selected from polar solvents.

4. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S1, diethanolamine reacts with 3,5-dihalomethylpyrazole hydrochloride (1) in the presence of a solvent at a temperature of 40°C to 80°C; the solvent is an aprotic solvent.

5. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S1, diethanolamine reacts with 3,5-dihalomethylpyrazole hydrochloride (1) in the presence of a solvent at a temperature of 40°C to 80°C; the solvent is selected from at least one of acetonitrile, dimethylformamide or dimethyl sulfoxide.

6. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S2, the acid used for the acidification of tetrahydroxysubstituted pyrazole (2) is a solution of diethyl ether chloride.

7. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S2, the acid used for acidification of tetrahydroxysubstituted pyrazole (2) is hydrogen chloride, the molar ratio of tetrahydroxysubstituted pyrazole (2) to hydrogen chloride is 1:1~4, and the molar ratio of tetrahydroxysubstituted pyrazole (2) to sulfoxide is 1:1~4.

8. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S2, after the tetrahydroxy-substituted pyrazole (2) is acidified, it is reacted with thionyl chloride in the presence of a solvent at a temperature of 80℃~100℃ for 3-5 hours; the solvent is a non-polar solvent.

9. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S2, after the tetrahydroxy-substituted pyrazole (2) is acidified, it is reacted with thionyl chloride in the presence of a solvent at a temperature of 80℃~100℃ for 3-5 hours; the solvent is diethyl ether.

10. The method for preparing the pyrazole-bridged phosphine ligand according to claim 3, characterized in that, In step S3, tetrachloro-substituted pyrazole (3) reacts with HPR2 2 In the presence of a solvent, the reaction is carried out at a temperature of 60℃~80℃ for 16~48h to obtain pyrazole-bridged phosphine ligands (4), wherein the solvent is selected from at least one of tetrahydrofuran, methanol or acetonitrile.

11. A D3-pz-D3 type binuclear complex, characterized in that, The structure of the D3-pz-D3 type binuclear complex is as follows: .

12. The application of the D3-pz-D3 type binuclear complex as described in claim 11 in the catalytic dimerization of phenylacetylene.

Images