Synthesis of ligand unfilled-corner cubic iron-sulfur cluster compound and potential small molecule activation application of ligand unfilled-corner cubic iron-sulfur cluster compound

Abstract

The invention relates to the field of synthesis of novel iron-sulfur cluster compounds and the field of design of biomimetic catalysts. According to the invention, the ligand unfilled-corner cubic alkane iron-sulfur cluster compound is controllably synthesized by utilizing a ligand replacement strategy under an oxidation-reduction condition; as a novel trinuclear iron catalyst, the iron-sulfur cluster compound is highly similar to iron-molybdenum coenzyme in local structure and has the potential of nitrogen activation and ammonia synthesis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of synthesis of new iron-sulfur clusters and the field of design of enzyme-mimicking catalysts, in particular to the synthesis of ligand-deficient cubane iron-sulfur clusters and their potential application in small molecule activation. BACKGROUND

[0002] Ammonia plays an irreplaceable important role in the global agricultural and chemical industry system. In the field of agriculture, the increase in agricultural income supported by industrial nitrogen fertilizer has solved the food supply problem for nearly half of the world's population; in the chemical industry, ammonia is a key raw material for the fertilizer industry and basic organic chemical industry, and its stable supply is directly related to the operation of the downstream chemical industry chain. At present, industrial ammonia synthesis generally relies on iron-based catalysts and needs to be carried out under harsh conditions of high temperature and high pressure. This process not only increases the additional equipment investment and raises the operating cost, but also causes a certain degree of environmental pollution. Therefore, developing new catalysts with mild reaction conditions and high catalytic activity has become an important breakthrough to promote the upgrading of ammonia synthesis technology and achieve energy saving and cost reduction.

[0003] Under this background, biological nitrogen fixation provides a new direction for research. Biological nitrogen fixation can be carried out at room temperature and pressure, and the total amount of nitrogen fixation accounts for more than 90% of the natural world, and there is no pollutant emission. Nitrogenase, as an important carrier of biological nitrogen fixation, its structure and catalytic mechanism are concerned. Studies have found that the active center of nitrogenase for activating nitrogen is iron-molybdenum coenzyme ([MoFe7S9C]), which is composed of Fe4S3 cluster and MoFe3S3 incomplete cubane cluster through special atom connection, and its catalytic process needs to go through three steps of complexation, reduction and hydrogenation, which depends on the synergistic effect of double iron atoms, completely overturning the traditional single iron atom catalytic design idea, and providing a molecular mechanism reference for the research and development of new catalysts.

[0004] Based on this, chemists propose the "structure imitation-function imitation" strategy. The ligand-deficient cubane iron-sulfur cluster is highly similar to the local structure of iron-molybdenum coenzyme and is regarded as a key intermediate for synthesizing iron-molybdenum coenzyme. And there are three open iron sites in its structure, and the synergistic effect of iron atoms makes it have the potential to activate small molecules. However, the synthesis of this kind of iron-sulfur cluster and the exploration of its catalytic performance are not in-depth. The mainstream self-assembly method needs to repeatedly adjust the reaction conditions, and the controllability of the results is poor, and it is difficult to obtain the target product in a directional way, which restricts its catalytic application research. SUMMARY

[0005] The present application aims to provide a synthesis of ligand-deficient cubane iron-sulfur cluster and its potential small molecule activation application, the present application successfully realizes the precise synthesis of ligand-deficient cubane iron-sulfur cluster by using ligand replacement strategy under redox conditions, fundamentally breaks through the technical limitation of traditional self-assembly synthesis method, and provides an efficient and reliable technical path for directional preparation of target products, so as to solve the problems in the above background art.

[0006] To achieve the above object, the present application provides the following technical scheme:

[0007] The present application provides a ligand-deficient cubane iron-sulfur cluster, the chemical formula of the compound is [(L1)MFe3(μ3-S)3(L2)3], and the structure is shown as formula I;

[0008]

[0009] Among them, L1 is one of the sum of tridentate ligand, bidentate ligand plus monodentate ligand, and the sum of three monodentate ligands, and the coordination atom of L1 is one or more of C, N, O, S, P, Si, F, Cl, Br and I; L2 is one or more of chalcogen end group ligand SR, halogen end group ligand, nitrogen end group ligand NR and carbene end group ligand; M is one of Mo, W, V and Fe.

[0010] Further, R in the chalcogen end group ligand SR is one of heteroatom-containing substituent, C1-C 40 alkyl, C2-C 40 alkenyl, C2-C 40 alkynyl, C6-C 48 aryl and C5-C 48 heteroaryl; the halogen end group ligand is one of Cl and Br; R in the nitrogen end group ligand NR is one of heteroatom-containing substituent, C1-C 40 alkyl, C2-C 40 alkenyl, C2-C 40 alkynyl, C6-C 48 aryl and C5-C 48 heteroaryl; and the carbene end group ligand is a nitrogen heterocyclic carbene, and the structure includes the structure as shown in the following formula:

[0011] .

[0012] The present application also provides a preparation method of the ligand-deficient cubane iron-sulfur cluster as described above, comprising the following steps:

[0013] Step 1: completely dissolving [(L1)WFe3(μ3-S)3(μ3-Cl)Cl3] in CH3CN to obtain solution A;

[0014] Step 2: the end group ligand is completely dissolved in CH3CN solution to obtain solution B; the end group ligand is one or more of chalcogen end group ligand SR, halogen end group ligand, nitrogen end group ligand NR, and carbene end group ligand;

[0015] Step 3: solution A and solution B are mixed, and the solution is color changed after stirring at 60 DEG C for 12 hours;

[0016] Step 4: after returning to room temperature, sodium-potassium alloy reagent is added to the solution, and the solution is stirred at room temperature for 12 hours;

[0017] Step 5: after the reaction is completed, methanol is added to the reaction solution, and the target crystal [(L1)WFe3(μ3-S)3(L2)3] is obtained after standing for 2 weeks.

[0018] Further, in step 1, the concentration of [(L1)WFe3(μ3-S)3(μ3-Cl)Cl3] in solution A is 0.1-0.2 mol / L.

[0019] Further, in step 2, the concentration of the end group ligand in solution B is 0.3-0.6 mol / L.

[0020] Further, in step 3, the molar ratio of [(L1)WFe3(μ3-S)3(μ3-Cl)Cl3] to end group ligand in solution A and solution B is 1:3.

[0021] Further, in step 4, the molar ratio of sodium-potassium alloy reagent to [(L1)WFe3(μ3-S)3(μ3-Cl)Cl3] in solution A is 2:1.

[0022] The application also provides the application of the ligand-deficient corner-cubane iron-sulfur cluster compound as described above in the field of catalysis.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1. The application uses ligand replacement strategy under redox conditions to controllably synthesize ligand-deficient corner-cubane iron-sulfur cluster compounds as novel ternary iron catalysts, which are highly similar to the local structure of iron-molybdenum coenzyme.

[0025] 2. The preparation method of the application is simple and easy to operate, has strong structural stability, and good repeatability in the synthesis process.

[0026] 3、Based on the mechanism understanding of the synergistic effect of multiple iron centers in the nitrogen fixation process of iron-molybdenum coenzyme, the performance limitations of traditional inorganic iron-based catalysts are broken through, and an iron-sulfur cluster compound with three open iron atom sites similar to the local structure of iron-molybdenum coenzyme is designed as a new type of metal-organic iron-based catalyst. The open structure of the cluster compound forms an adaptive reaction space, not only reduces the complexing energy barrier of nitrogen molecules, but also provides precise site support for the nitrogen activation process, has potential application value for activating nitrogen to synthesize ammonia, and provides a new technical path for the green and efficient upgrading of industrial ammonia synthesis catalysts. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The structural general formula of the ligand cubane iron-sulfur cluster compound of the application;

[0028] Figure 2 The structural formula of Tp* of the application;

[0029] Figure 3 The structural formula of Me NHC Et and NHC Ipr ;

[0030] Figure 4 The three-dimensional schematic diagram of the crystal material structure of a ligand cubane iron-sulfur cluster compound prepared in Example 1 of the application;

[0031] Figure 5 The three-dimensional schematic diagram of the crystal material structure of a ligand cubane iron-sulfur cluster compound prepared in Example 2 of the application;

[0032] Figure 6 The infrared spectrum of a ligand cubane iron-sulfur cluster compound material prepared in Example 1 of the application;

[0033] Figure 7 The infrared spectrum of a ligand cubane iron-sulfur cluster compound material prepared in Example 2 of the application;

[0034] Figure 8 The ultraviolet-visible absorption spectrum of a ligand cubane iron-sulfur cluster compound material prepared in Example 1 of the application;

[0035] Figure 9 The ultraviolet-visible absorption spectrum of a ligand cubane iron-sulfur cluster compound material prepared in Example 2 of the application;

[0036] Figure 10 The cyclic voltammogram of a ligand cubane iron-sulfur cluster compound material prepared in Example 1 of the application;

[0037] Figure 11Cyclic voltammetry curve of a ligand-deficient cuboethane iron-sulfur cluster compound material prepared in Example 2 of this invention; Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] Preparation of compound [(Tp * )WFe3(μ3-S)3( Me NHC Et )3]:

[0041] First refer to the literature (Lavallo, V.; Canac, Y.; Donnadieu, B.; Schoeller, WW; Bertrand, G., Cyclopropenylidenes: from interstellar space to an isolated derivative in the laboratory. Science (New York, NY) 2006, 312 (5774), 722-4.; Hahn, FE, Heterocyclic carbenes. Angewandte Chemie (International ed.in English) 2006, 45 (9), 1348-52.) Preparation Me NHC Et Ligands.

[0042] Accurately weigh 5 g of N,N-diethylthiourea (Aladdin-D154883) and 3.33 g of 3-hydroxy-2-butanone (Innochem-A35009) using an analytical balance, and react them in 110 mL of n-hexanol at 160 °C for 12 h with stirring. Freeze the reaction solution for 12 h to precipitate crystals, and filter to obtain the carbene precursor. Take 4 g of the carbene precursor and 2.0745 g of potassium, and heat and stir at 80 °C for 24 h under nitrogen purging in 30 mL of THF. After cooling, filter the solution, freeze the filtrate for 12 h to precipitate crystals, and filter to obtain the target ligand. Me NHC Et The yield was 80%.

[0043] Accurately weigh 5.7 g of (Et4N)[(Tp] using an analytical balance. * [WFe3(µ3-S)3(µ3-Cl)Cl3] (prepared according to the literature, He, J.; Wei, J.; Xu, G.; Chen, XD, Stepwise Construction of Mo-Fe-S Clusters Using a LEGO Strategy. Inorg Chem 2022, 61 (9), 4150-4158), completely dissolved in 50 mL CH3CN, and then weighed 2.3 g. Me NHC Et The ligand was completely dissolved in 50 mL of CH3CN solution. The two solutions were mixed and stirred at 60°C for 12 hours, during which a color change occurred. After returning to room temperature, 0.62 g of sodium-potassium alloy (Aladdin-P282335) was added to the solution, and the mixture was stirred at room temperature for 12 hours. After the reaction was complete, methanol was added to the reaction solution, and the mixture was allowed to stand for 2 weeks to obtain the target crystals [(Tp * )WFe3(μ3-S)3( Me NHC Et [3], with a yield of 80%.

[0044] The three-dimensional structure of the ligand-deficient cuboethane iron-sulfur cluster crystal material prepared in Example 1 of this invention is as follows: Figure 4 As shown, the Fourier attenuated total reflectance infrared spectrum is as follows: Figure 6 As shown, the ultraviolet-visible absorption spectrum is as follows: Figure 8 As shown, the cyclic voltammetry curve is as follows: Figure 10 As shown.

[0045] Example 2

[0046] Preparation of compound [(Tp * )WFe3(μ3-S)3(NHC Ipr )3]:

[0047] First refer to the literature (Lavallo, V.; Canac, Y.; Donnadieu, B.; Schoeller, WW; Bertrand, G., Cyclopropenylidenes: from interstellar space to an isolated derivative in the laboratory. Science (New York, NY) 2006, 312 (5774), 722-4.; Hahn, FE, Heterocyclic carbenes. Angewandte Chemie (International ed.in English) 2006, 45 (9), 1348-52.) Preparation of NHC Ipr Ligands. 2.81 g of 1,3-diisopropylimidazolium chloride (Innochem-A92630) was accurately weighed using an analytical balance, and 50 mL of CH3CN was added. Then, 15 mL of 1 mol / L bis(trimethylsilyl)amino potassium (Aladdin-P109542) was added, and the mixture was stirred at room temperature for 12 h to obtain NHC. Ipr Carbene solution.

[0048] Accurately weigh 5.7 g of (Et4N)[(Tp] using an analytical balance. * [WFe3(µ3-S)3(µ3-Cl)Cl3] (prepared according to the literature, He, J.; Wei, J.; Xu, G.; Chen, XD, Stepwise Construction of Mo-Fe-S Clusters Using a LEGO Strategy. Inorg Chem 2022, 61 (9), 4150-4158), was completely dissolved in 50 mL CH3CN, mixed with the previous carbene solution, and stirred at 60°C for 6 hours, during which the solution showed a color change. After returning to room temperature, 0.62 g of sodium-potassium alloy (Aladdin-P282335) was added to the solution, and the mixture was stirred at room temperature for 10 hours. After the reaction was completed, methanol was added to the reaction solution, and the solution was allowed to stand for 2 weeks to obtain the target crystal [(Tp * )WFe3(μ3-S)3(NHC Ipr [3], with a yield of 78%.

[0049] The three-dimensional structure of the ligand-deficient cuboethane iron-sulfur cluster crystal material prepared in Example 2 of this invention is as follows: Figure 5 As shown, the Fourier attenuated total reflectance infrared spectrum is as follows:Figure 7 As shown, the ultraviolet-visible absorption spectrum is as follows: Figure 9 As shown, the cyclic voltammetry curve is as follows: Figure 11 As shown.

[0050] Determination of the crystal structure of ligand-deficient cuboethane iron-sulfur clusters:

[0051] The prepared crystals were observed under a microscope at room temperature. Target cluster crystals were selected and subjected to X-ray single-crystal diffraction experiments at 298 K. All crystals were fixed on Hamiltonian loops using Parabar 10312 oil. Data were collected using a Bruker APEX II CCD diffractometer with Mo-Kα radiation (50 kV and 30 mA, λ = 0.71073 Å) employing a φ- / ω-scans collection strategy. Data were calculated using SAINT, and SADABS was used for absorption correction. The crystal structure was resolved using SHELXT, and the F-axis was analyzed using SHELXL and OLEX2 with full-matrix least squares. 2 The crystallographic process involved refining all non-hydrogen atoms anisotropically, and all hydrogen atoms were theoretically hydrogenated. The positions of the hydrogen atoms were calculated based on the geometric configuration, and the refinement was performed using a riding model. Specific crystallographic data and structural parameters are shown in Table 1.

[0052] Table 1:

[0053]

[0054] As shown in Table 1, the molecular formula of the ethyl carbene ligand-substituted ligand-deficient cuboethane iron-sulfur cluster compound in Example 1 is C1. 46 H 78 BFe3N 12 OS3W, triclinic crystal system, space group P The smallest asymmetric unit includes a [(Tp * )WFe3(μ3-S)3( Me NHC Et )3] Corner-deficient cubane, one THF solvent molecule. The W atom is coordinated with Tp in an octahedral configuration. * The ligand has three N atoms and three S atoms coordinated; the three Fe atoms are respectively associated with two S atoms and one Fe atom. Me NHC Et The C atom is coordinated, exhibiting a rare three-coordination mode. The isopropyl carbene-substituted ligand-deficient cuboethane iron-sulfur cluster compound in Example 2 has the molecular formula C0. 42 H 70 BFe3N 12 S3W, monoclinic crystal system, space group P21 / c, minimum asymmetric unit cell includes one [(Tp* )WFe3(μ3-S)3(NHC Ipr )3] Corner-deficient cubane. The W atom is coordinated with Tp in an octahedral configuration. * The ligand has three N atoms and three S atoms coordinated to it; the three Fe atoms are respectively associated with two S atoms and one NHC atom. Ipr The C atom is coordinated, exhibiting a rare three-coordinate mode.

[0055] Infrared spectroscopy determination of ligand-deficient cuboethane iron-sulfur clusters

[0056] At room temperature, the Fourier attenuated total reflectance infrared spectra of ligand-deficient cuboethane iron-sulfur clusters were determined using an ALPHA II Fourier transform infrared spectrometer. Analysis Figure 6 and Figure 7 It can be observed that the elution positions of these cluster compounds are quite similar, basically all containing the 2800-3000 cm⁻¹ peak position. -1 aliphatic and aromatic CH stretching vibrations, 2500 cm -1 The stretching vibrations of the BH groups on the left and right, 1500 cm -1 Stretching vibrations of the left and right C=N double bonds, 1040 cm -1 The stretching vibrations of the left and right CN single bonds and 900-1000 cm -1 The stretching vibration of the left and right NN single bonds.

[0057] UV-Vis absorption spectroscopy determination of ligand-deficient cuboethane iron-sulfur clusters:

[0058] At room temperature, the UV-Vis absorbance of ligand-deficient cuboidal iron-sulfur clusters was measured using a UH5300 spectrophotometer. The concentration of the clusters was 100 ppm. Analysis Figure 8 and Figure 9 It can be observed that this type of cluster compound exhibits a strong UV-Vis absorption peak at 230-235 nm, which is presumably the characteristic absorption peak of Tp*; while at 250-300 nm, Figure 9 Presented Figure 8 The absence of characteristic absorption peaks is, in our opinion, due to the differences in terminal carbene ligands.

[0059] Electrochemical testing of ligand-deficient cuboethane iron-sulfur clusters:

[0060] At room temperature, a ChenHua CHI600E electrochemical workstation was used with a glassy carbon electrode as the working electrode, an Ag / AgNO3 electrode (acetonitrile solution) as the reference electrode, a platinum wire electrode as the counter electrode, and a 0.1 mmol / mL tetraethylammonium tetrafluoroborate acetonitrile solution as the electrolyte. The ligand-deficient cuboline iron-sulfur clusters prepared in Examples 1 and 2 were dissolved in 10 mL of acetonitrile to prepare 1.0 mmol / mL solutions, and scanned at 100 mV / s.

[0061] Through analysis Figure 10 and Figure 11 This class of clusters exhibits multiple reversible redox couples, displaying rich redox properties. Furthermore, the terminal ligands significantly alter the relevant chemical properties of the clusters, and due to the removal of the chlorine atom at the bridging position, the redox couples of this series of clusters are generally negative, making them more susceptible to oxidation and exhibiting extremely strong reactivity. This further demonstrates that ligand-deficient cubane iron-sulfur clusters possess the potential to activate small molecules.

[0062] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0063] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A ligand-deficient cuboethane iron-sulfur cluster compound, characterized in that, The chemical formula of the compound is [(L1)MFe3(μ3-S)3(L2)3], and its structure is shown in Formula I; L1 is one of the following: a tridentate ligand, a sum of a bidentate ligand and a monodentate ligand, or a sum of three monodentate ligands. The coordinating atom of L1 is one or more of C, N, O, S, P, Si, F, Cl, Br, and I. L2 is one or more of the following: a chalcogenide-terminated ligand SR, a halogen-terminated ligand NR, a nitrogen-terminated ligand NR, or a carbene-terminated ligand. M is one of Mo, W, V, and Fe.

2. The ligand-deficient cuboethane iron-sulfur cluster compound according to claim 1, characterized in that, In the chalcogenide-terminated ligand SR, R is a heteroatom-containing substituent, C1-C. 40 Alkyl, C2-C 40 alkenyl, C2-C 40 alkynyl group, C6-C 48 Aryl, C5-C 48 One of the heteroaryl groups, wherein the halogen-terminated ligand is one of Cl and Br, and the R in the nitrogen-terminated ligand NR is a heteroatom-containing substituent, C1-C. 40 Alkyl, C2-C 40 alkenyl, C2-C 40 alkynyl group, C6-C 48 Aryl, C5-C 48 One of the heteroaryl groups; the carbene-type terminal ligand is a nitrogen-heterocyclic carbene, which includes the following structure: 。 3. The method for preparing the ligand-deficient cuboethane iron-sulfur cluster compound according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Dissolve [(L1)WFe3(µ3-S)3(µ3-Cl)Cl3] completely in CH3CN to obtain solution A; Step 2: Dissolve the terminal ligand completely in CH3CN solution to obtain solution B; Step 3: Mix solution A and solution B, stir and react at 60°C for 12 hours, and the solution will change color; Step 4: Return to room temperature, add sodium-potassium alloy reagent to the solution, and stir the reaction at room temperature for 12 hours; Step 5: After the reaction is complete, methanol is added to the reaction solution and allowed to stand for 2 weeks to obtain the target crystal [(L1)WFe3(μ3-S)3(L2)3].

4. The method for preparing the ligand-deficient cuboethane iron-sulfur cluster compound according to claim 3, characterized in that, In step 1, the concentration of [(L1)WFe3(µ3-S)3(µ3-Cl)Cl3] in solution A is 0.1-0.2 mol / L.

5. The method for preparing a ligand-deficient cuboethane iron-sulfur cluster compound according to claim 3, characterized in that, In step 2, the concentration of the terminal ligand in solution B is 0.3-0.6 mol / L.

6. The method for preparing a ligand-deficient cuboethane iron-sulfur cluster compound according to claim 3, characterized in that, In step 3, the molar ratio of [(L1)WFe3(µ3-S)3(µ3-Cl)Cl3] to the terminal ligand in solution A and solution B is 1:

3.

7. The method for preparing a ligand-deficient cuboethane iron-sulfur cluster compound according to claim 3, characterized in that, In step 4, the molar ratio of the sodium-potassium alloy reagent to [(L1)WFe3(µ3-S)3(µ3-Cl)Cl3] is 2:

1.

8. The application of the ligand-deficient cuboethane iron-sulfur cluster compound according to any one of claims 1-2 in the field of catalysis.

Images