Cu4 cluster catalytic material with synergistic double catalytic sites and application of Cu4 cluster catalytic material in hydroboration reaction

Abstract

The invention discloses a Cu4 cluster catalytic material with synergistic double catalytic sites and application of the Cu4 cluster catalytic material in hydroboration reaction, and belongs to the crossing field of coordination chemistry and nano materials. The copper cluster is synthesized through a simple one-pot method by taking N-heterocyclic thione (methylmercaptoimidazole) as a protective ligand, and the yield is high. The chemical formula of the cluster is C16H20Cu4N8S4, the abbreviation is Cu4NC, the cluster belongs to a tetragonal system, the space group is P42 / n, a is equal to 10.0 1930 (10), b is equal to 10.0 1930 (10), c is equal to 11.6512 (2), alpha is equal to 90 degrees, beta is equal to 90 degrees, gamma is equal to 90 degrees, and V is equal to 1169.62 (3). The catalyst realizes efficient and high-selectivity catalysis of alkyne hydroboration reaction by utilizing the advantage of synergistic double catalytic sites, and has the advantages of excellent chemical selectivity (up to 100%), high efficiency (conversion number (TON) = 77786), high yield (up to 99%), wide substrate range (28), mild conditions (room temperature and air), high recovery rate and the like; the development of the functionalized cluster catalyst is facilitated.

Description

Technical Field

[0001] The invention belongs to the cross field of coordination chemistry and nanomaterials, relates to a novel Cu4 cluster catalyst material modified by N-heterocyclic thione ligand, and efficiently applies the Cu4 cluster catalyst material to hydroboration reaction. Background Art

[0002] The preparation and study of atomically precise metal nanoclusters has become a new and promising research direction in the field of nanoscience. Metal nanoclusters are usually composed of a class of clusters with precise atomic structures composed of tens to hundreds of metal atoms bridged by organic ligands. As a bridge connecting atoms and nanoparticles, metal nanoclusters exhibit unique optical, electrical and chemical properties. Compared with gold and silver, copper has many advantages such as low price, high abundance in the earth's crust and wide sources. However, due to the difficulty in synthesizing copper clusters and their easy oxidation in the air, the synthesis of highly active copper cluster catalysts is still a huge challenge. The research on copper clusters is still in its infancy, especially atomically precise carbene-modified copper cluster catalysts.

[0003] The hydroboration reaction of alkynes is an important type of organic chemical reaction. Through the hydroboration reaction of alkynes, new CB bonds are directly constructed, multifunctional organic reaction modules are constructed, and the directional, controllable and diverse functionalization of alkynes is achieved. Various complex organic molecules are directly constructed in a streamlined and efficient manner. Therefore, it is very important in various fields of chemistry, especially in the field of pharmaceutical and other fine chemical research. Its product, vinyl boron compound, is an important organic intermediate in organic synthesis, drug synthesis and synthesis of high value-added industrial compounds.

[0004] Copper catalysts are one of the most representative catalysts for catalytic hydroboration reactions, but it is still a considerable challenge to achieve high chemical selectivity and considerable conversion rate for catalytic hydroboration of alkynes. Summary of the invention

[0005] The present invention aims to synthesize a Cu4 cluster catalyst with high efficiency and multifunctional N-heterocyclic thione ligand protection, and to develop an efficient, multifunctional and practical method for preparing important organic reaction module vinyl boron compounds.

[0006] To this end, the present invention has developed a Cu4 cluster material modified with N-heterocyclic thione ligand, characterized in that: its chemical formula is: C 16 H 20 Cu4N8S4, abbreviated as: Cu4NC, belongs to the tetragonal system, and the space group is P42 / n. α=90°, β=90°, γ=90°, The shell ligand used is methimidazole, and the structural formula is as follows:

[0007] The preparation method of the Cu4 cluster material of the present invention is achieved by the following steps:

[0008] Under air atmosphere, copper salt Cu(MeCN)4PF6 is dissolved in MeCN, and methanol solution containing methimazole is added thereto under vigorous stirring at room temperature. After the solution turns blue, it is stirred again; then an excess of triethylamine is added to the stirring reaction to form microcrystals. The suspension is centrifuged, the microcrystals are collected, and vacuum dried.

[0009] The core of the copper nanocluster is composed of four copper atoms and four N-heterocyclic thione ligands ( Figure 1 The NHT ligands contain S and N donors and can be firmly anchored on the surface of the Cu4NC cluster through Cu-S and Cu-N bonds. In the Cu4 unit, the average Cu-Cu distance is observed to be Less than twice the van der Waals radius ( Figure 2 shown).

[0010] The N-heterocyclic thione ligand-modified copper cluster catalyst of the present invention can be used for efficient and multifunctional catalytic hydroboration of alkynes, and its properties are specifically described as follows:

[0011] The cluster material catalyst fully utilizes the advantages of its synergistic dual catalytic sites in the alkyne hydroboration reaction to achieve efficient and highly selective catalytic alkyne hydroboration reaction, including excellent chemical selectivity (up to 100%), high efficiency (turnover number (TON) = 77786), high yield (up to 99%), and a wide substrate range (28 examples) ( Figure 3 ), mild conditions (room temperature and air), high stability (catalytic cycle 5 times), high recovery rate and scale-up experiments ( Figure 4 As shown) and vinyl boron compounds were directed to develop functionalized cluster catalysts.

[0012] Beneficial effects of the present invention: The Cu4 cluster of the present invention has a structure with precise atomic size, and the structure can be accurately characterized at the atomic level; the N-heterocyclic thione ligand gives it the dual properties of rigidity and flexibility, and realizes efficient and multifunctional catalysis of alkyne hydroboration reaction under mild conditions, and has very good application value for preparing important organic reaction module vinyl boron compounds. The cluster catalyst has a good application prospect in the field of organic catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1This is a schematic diagram of the shell protective ligand structure of the Cu4 copper cluster material of the present invention. Figure 2 It is a schematic structural diagram of the Cu4 copper cluster material of the present invention. Figure 3 The present invention provides a substrate table for the hydroboration reaction of alkynes catalyzed by the Cu4 copper cluster material. Figure 4 This is an amplified experiment of the hydroboration of alkynes catalyzed by the Cu4 copper cluster material of the present invention and the directional derivatization of vinyl boron compounds. DETAILED DESCRIPTION

[0014] The present invention will be further described below by way of examples:

[0015] Example 1: Synthesis of Cu4 copper cluster material of the present invention

[0016] Under air atmosphere, copper salt Cu(MeCN)4PF6 (4.0mmol) was dissolved in 100mL MeCN, and 100mL methanol solution containing methimazole (4.0mmol) was added thereto under vigorous stirring at room temperature. After the solution turned blue, it was stirred for another 10 minutes. Then, an excess of triethylamine (2.0ml) was added to the stirring reaction, and microcrystals were immediately formed. The suspension was centrifuged and the microcrystals were collected. The microcrystals were dissolved in DCM, and after 2 days at room temperature, the resulting solution was diffused with MeCN to obtain colorless Cu4NC crystals with a yield of 75%, which was then dried in vacuo.

[0017] The Cu4 copper cluster material of the present invention obtained in Example 1 was further characterized as follows: (1) Crystal structure determination The X-ray single crystal diffraction data of the complex were measured on a Rigaku XtaLAB Pro single crystal diffractometer using a single crystal sample of appropriate size. The data were all measured using CuKα radiation monochromatized by graphite. The diffraction source was collected at 200K by ω scanning mode, and was corrected by Lp factor and semi-empirical absorption. The structure was first solved by direct method using SHELXS-97 program, and then refined by full matrix least squares method using SHELXL-97 program. All non-hydrogen atoms were refined by anisotropic thermal parameter method. All hydrogen atoms were refined by isotropic thermal parameter method. Detailed crystal measurement data are shown in Table 1.

[0018] Table 1 Main crystallographic data of nano copper cluster materials of the present invention

[0019] Application Example 1: Cu4 copper cluster catalyst catalyzes the hydroboration of alkynes with ethinyl estradiol as the reaction substrate Under air atmosphere, ethinylestradiol 1aa (59.3 mg, 0.2 mmol, 1.0 eq), B2Pin2 2 (111.8 mg, 0.44 mmol, 2.2 eq.), microcrystalline Cu4NC catalyst (2.8 mg, 2.0 mol%), K2CO3 (60.7 mg, 0.44 mmol, 2.2 equiv.) and mixed solvent (2.0 mL, MeCN-H2O, v / v 4 / 1) were added to a reaction bottle. The reaction mixture was stirred at room temperature for 1 hour. The reaction was monitored by TLC (PE-EA, v / v 2 / 1). When the alkyne was consumed, the reaction was quenched, and 0.2 mmol of trimethoxybenzene was added as an internal standard. The catalytic yield was determined by the nuclear magnetic internal standard method. Three parallel experiments were performed, and the average value was taken to calculate the catalytic yield. Finally, the crude product was concentrated. The crude product was then purified by column chromatography (PE-EA, v / v 7 / 3) to afford the target product 4aa as a white solid with an overall isolated yield of 85% (71.9 mg) ( Figure 3 ,4aa). In other embodiments, as shown in the above reaction scheme, different products and yields are obtained by using different substrates. The above embodiments are only used to illustrate the content of the present invention. In addition, the present invention has other embodiments. However, all technical solutions formed by equivalent replacement or equivalent deformation methods fall within the protection scope of the present invention.

Claims

1. Application of Cu4 cluster materials modified by N-heterocyclic thione ligands in hydroboration reaction, characterized in that: It is used as a catalyst for the hydroboration reaction of alkynes; the Cu4 cluster material modified by the N-heterocyclic thione ligand has the chemical formula: C 16 H 20 Cu4N8S4, abbreviated as: Cu4NC, belongs to the tetragonal system, and the space group is P42 / n. α=90°, β=90°, γ=90°, The shell ligand used is methimidazole, and the structural formula is as follows:

2. The use of the N-heterocyclic thione-modified Cu4 cluster material according to claim 1 in a hydroboration reaction, characterized in that: The core of the Cu4 cluster material modified by the N-heterocyclic thione ligand is composed of four copper atoms, and the Cu4 metal core is protected by four N-heterocyclic thione ligands; The N-heterocyclic thione ligands are firmly anchored on the surface of Cu4NC clusters via Cu-S and Cu-N bonds.

3. The use of the N-heterocyclic thione-modified Cu4 cluster material in a hydroboration reaction as claimed in claim 1 or 2, characterized in that: The hydroboration reaction route of the alkyne is as follows: R 1 A substituent selected from the following:

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