Beta-diimine cerium complex and preparation method and application thereof

Abstract

A beta-diamide cerium complex, a preparation method and application thereof, the beta-diamide cerium complex has a structural formula as shown in formula (I), wherein the beta-diamide cerium complex is prepared by the following method: dissolving a beta-diamide ligand in a reaction solvent, adding a base to perform a deprotonation reaction, and further reacting with a cerium bromide dissolved in the solvent to obtain the beta-diamide cerium complex. The reactivity research is specifically focused on a ligand exchange reaction. The synthesis path is simple, has a good yield, and expands the range of beta-diamide stable rare earth metal complexes.

Description

Technical Field

[0001] This invention relates to the field of organometallic complex technology, specifically to a β-diimine cerium complex, its preparation method, and its application. Background Technology

[0002] Rare earth metals possess properties distinct from main group elements and transition metals due to their higher coordination numbers and ease of coordination with nitrogen- and oxygen-containing ligands. These differences extend beyond the structure and chemical bonding of their metal complexes; they also exhibit unique performance characteristics in catalytic organic synthesis and polymer polymerization. Over decades of development, our understanding of rare earth metal organochemistry has deepened, leading to its application in numerous fields. Based on the type of stable rare earth metal ligands, they can be broadly classified into cyclopentadienyl and non-cyclopentadienyl rare earth metal organochemistry complexes. However, cyclopentadienyl ligands suffer from drawbacks such as simple structure, difficulty in modification, and poor stability of mono-metallocene complexes, which limits their application to some extent.

[0003] In recent years, non-pentanediol ligand-stabilized rare earth metal complexes have seen rapid development. Among them, nitrogen-containing ligands are the most important class. By changing the type of substituents on the nitrogen atom, the electronic and steric effects of the ligands can be effectively controlled, resulting in diverse structural characteristics and reactivity of the corresponding rare earth metal complexes. β-diimine ligands, as an important class of bidentate nitrogen-containing ligands, have advantages such as readily available raw materials, simple synthesis, and multiple coordination modes, and have made a series of advances in the synthesis and application research of low-valence main group element complexes, d-block transition metal complexes, and f-block metal complexes. Rare earth metal cerium has a special electronic configuration and is one of the metals with good luminescent properties. Therefore, the optical properties and catalytic research of cerium compounds have attracted researchers' attention. However, due to the large atomic radius and high inner-shell orbital energy levels of cerium, energy level mismatch occurs when it interacts with ligands, resulting in poor stability and difficulty in separation and characterization of the complexes. Therefore, developing synthetic methods for stable cerium complexes and studying their reactivity are of great guiding significance for expanding the application range of β-diimine ligands and understanding the bonding characteristics of cerium complexes. Summary of the Invention

[0004] Technical problem solved: In view of the problems existing in the prior art, the present invention provides a β-diimine cerium complex, its preparation method and application. The method is simple, efficient and easy to synthesize, which enriches the types of β-diimine-stable rare earth metal complexes and provides a new route for the synthesis of cerium complexes. Moreover, the β-diimine cerium complex provided by the present invention can be used as a reaction precursor for ligand exchange and salt elimination reactions to prepare β-diimine-stable rare earth metal cerium complexes.

[0005] Technical solution: A β-diimine cerium complex, wherein the structural formula of the β-diimine cerium complex is shown in formula (I).

[0006]

[0007] Preferably, the β-diimine cerium complex is a monoclinic crystal with space group P121 / m1 and cell parameters as follows: α=90°, β=91.352(2)°, γ=90°. In this complex, the ligand forms a 1:1 molar ratio with the cerium ion. The ligand coordinates to the cerium ion in a bidentate chelate manner, while the cerium ion also coordinates with two solvent molecules.

[0008] The preparation method of the above-mentioned β-diimine cerium complex includes the following steps:

[0009] Step 1. Weigh the β-diimine compound into a reaction vessel, dissolve it in a solvent, add a base to carry out a deprotonation reaction to obtain the deprotonated ligand;

[0010] Step 2. Then, a cerium bromide suspension dissolved in a solvent is added to the reaction vessel to carry out the reaction, and the β-diimine cerium complex is obtained after post-treatment.

[0011] Preferably, the solvent is toluene, tetrahydrofuran (THF), or n-hexane, the base is sodium bis(trimethylsilyl)amino (NaHMDS), the molar ratio of the β-diimine compound to the base in step one is 1:1.05-1.1, and the molar ratio of the deprotonated ligand to cerium bromide in step two is 1:1.05-1.1.

[0012] Preferably, the deprotonation reaction time in step one is 12-18 hours, and the reaction temperature is room temperature (generally 25°C).

[0013] Preferably, the post-processing steps in step two are as follows: the reactants are filtered under reduced pressure, the reaction solvent is removed under vacuum, the residue is washed with n-hexane, and the solid product is obtained after removing the residual solvent.

[0014] Based on the application of the aforementioned β-diimine cerium complex in ligand exchange reactions or salt elimination reactions, this complex reaction can yield complexes with different structures.

[0015] Preferably, when the β-diimine cerium complex undergoes a ligand substitution reaction with a coordination solvent during the ligand exchange reaction, the specific steps are as follows: under an inert atmosphere, the β-diimine cerium complex is placed in a coordination solvent and stirred at room temperature, followed by post-treatment to obtain the target product; when the β-diimine cerium complex undergoes a salt elimination reaction, the specific steps are as follows: the β-diimine cerium complex is placed in a solvent, cyclopentadienyl sodium (CpNa) or 2,6-diisopropylaniline lithium (DippNHLi) is added, and stirred at room temperature, followed by post-treatment to obtain the target product.

[0016] Preferably, the coordinating solvent is pyridine (Py), N,N-dimethylpyridine (DMAP), dimethoxyethane (DME), or 2,6-dimethylphenylisocyanuric acid (ArNC); during the salt elimination reaction, the solvent is tetrahydrofuran, the molar ratio of the β-diimine cerium complex to cyclopentadienyl sodium is 1:2 to 2.1, and the molar ratio of the β-diimine cerium complex to 2,6-diisopropylaniline lithium is 1:1.05 to 1.1.

[0017] Preferably, the room temperature stirring reaction time for both the ligand exchange reaction and the salt elimination reaction is 12-24 h. For the ligand exchange reaction, the post-processing steps are as follows: after the reaction is completed, the solvent is removed under reduced pressure and the product is dried under vacuum to obtain the target solid product. For the salt elimination reaction, the post-processing steps are as follows: diatomaceous earth filtration, solvent removal under reduced pressure, vacuum drying, washing with n-hexane to remove residual solvent to obtain the target solid product.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0019] 1) This invention develops a method for synthesizing β-diimine cerium complexes, which is simple, efficient, and easy to synthesize. It enriches the types of stable rare-earth metal complexes of β-diimine and provides a new route for the synthesis of cerium complexes.

[0020] 2) This invention uses β-diimine cerium complexes as reaction precursors to explore their applications in ligand exchange and salt elimination reactions, obtaining cerium complexes with different coordination modes. These metal complexes are not only significant for rare earth coordination chemistry research, but also provide a theoretical basis for understanding the properties of cerium complexes. Attached Figure Description

[0021] Figure 1 A schematic diagram of a single crystal of the β-diimine cerium complex provided in Example 1;

[0022] Figure 2 A schematic diagram of a single crystal of the pyridine-coordinated cerium complex provided in Example 2;

[0023] Figure 3 A schematic diagram of a single crystal of the dimethoxyethane cerium complex provided in Example 3;

[0024] Figure 4 A schematic diagram of a single crystal of the 2,6-dimethylbenzene isocyanate complex provided in Example 4;

[0025] Figure 5 A schematic diagram of a single crystal of the N,N-dimethylpyridine cerium complex provided in Example 5;

[0026] Figure 6 A schematic diagram of a single crystal of the dicyclopentadiene cerium complex provided in Example 6;

[0027] Figure 7 This is a schematic diagram of a single crystal of the β-diimine lithium complex provided in Example 7. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, all raw materials, reagents, etc., used are commercially available. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art.

[0029] Example 1

[0030] This embodiment provides a β-diimine cerium complex, the synthetic route of which is as follows:

[0031]

[0032] First, the β-diimine ligand is reacted with NaHMDS to obtain the deprotonated target product; then, the deprotonated β-diimine ligand is reacted with CeBr3 to obtain the β-diimine cerium complex.

[0033] The specific steps are as follows: Weigh the β-diimine ligand in the glove box. (0.418 g, 1 mmol) was dissolved in tetrahydrofuran (10 mL), and 0.5 mL of NaHMDS (2 mol / L THF) was added. The mixture was stirred at room temperature for 12 hours. After the reaction was complete, the solvent was removed under reduced pressure, and the mixture was washed with n-hexane to remove the residual solvent, yielding a white powdery solid, which was the deprotonated ligand. The yield was 91%. Further reaction was carried out with CeBr3: 0.22 g (0.5 mmol) of the deprotonated ligand was dissolved in tetrahydrofuran (5 mL), and a pre-prepared suspension of CeBr3 (0.19 g, 0.5 mmol) in tetrahydrofuran (5 mL) was added dropwise. The mixture was stirred at room temperature for 18 hours. After the reaction was complete, the mixture was filtered under reduced pressure, the solvent was removed under vacuum, and the mixture was washed with n-hexane to remove residual solvent, yielding a yellow solid product, the β-diimine cerium complex. Yield 89%. Elemental analysis, C 35 H57 Calculated values ​​for CeBr2N2O2: C 50.18; H 6.86; N 3.34; Measured values: C 49.98; H 6.66; N 3.18.

[0034] The above β-diimine cerium complex can undergo ligand exchange and salt elimination reactions, as shown in the following reaction formulas:

[0035]

[0036] Example 2

[0037] This embodiment provides a pyridine ligand-substituted β-diimine cerium complex, and the specific synthesis method is as follows:

[0038] Weigh out the β-diimine cerium complex in the glove box. (86.2 mg, 0.1 mmol) was dissolved in the coordination solvent pyridine (Py) (5 mL), and the reaction was stirred at room temperature for 12 hours. After the reaction was completed, the solvent was removed under reduced pressure to obtain a yellow solid, namely the pyridine-coordinated cerium complex. Yield 93%. Elemental analysis, C 39 H 51 Calculated values ​​for CeBr2N4: C 53.49; H 5.87; N 6.40; Measured values: C 53.28; H 5.68; N 6.28.

[0039] Example 3

[0040] This embodiment provides a β-diimine cerium complex substituted with a dimethoxyethane ligand, the synthesis method of which is as follows:

[0041] The steps and parameters are the same as in Example 2, except that the coordination solvent is replaced with dimethoxyethane (DME), resulting in a bright yellow solid product, namely the dimethoxyethane cerium complex. Yield 92%. Elemental analysis, C 40 H 58 Calculated values ​​for CeBr2N2O2: C 53.45; H 6.50; N 3.12; Measured values: C 53.28; H 6.39; N 2.98.

[0042] Example 4

[0043] This embodiment provides a β-diimine cerium complex substituted with a 2,6-dimethylbenzeneisonitrile ligand, the synthesis method of which is as follows:

[0044] The steps and parameters are the same as in Example 2, except that the coordinating solvent is replaced with the coordinating molecule 2,6-dimethylphenylisocyanate ArNC (13.2 mg, 0.1 mmol), and the solvent used is tetrahydrofuran (5 mL), yielding a pale yellow solid product, 2,6-dimethylphenylisocyanate cerium complex. Yield 71%. Elemental analysis, C 67 H 91 Calculated values ​​for Ce2Br4N5: C 51.38; H 5.86; N 4.47; Measured values: C 51.26; H 5.69; N 4.36.

[0045] Example 5

[0046] This embodiment provides an N,N-dimethylpyridine ligand-substituted β-diimine cerium complex, the synthesis method of which is as follows:

[0047] The steps and parameters are the same as in Example 2, except that the coordination solvent is replaced with the coordination molecule N,N-dimethylpyridine DMAP (12.3 mg, 0.1 mmol), and the solvent used is tetrahydrofuran (5 mL), yielding a yellow solid product, N,N-dimethylpyridine cerium complex. Yield 92%. Elemental analysis, C 50 H 69 Calculated CeBr2N6 values: C 56.97; H 6.60; N 7.97, measured values: C 56.79; H 6.48; N 7.88.

[0048] Example 6

[0049] This embodiment provides a β-diimine cerium complex substituted with a dicyclopentadiene ligand, the synthesis method of which is as follows:

[0050] Weigh the β-diimine cerium complex from the glove box. (86.2 mg, 0.1 mmol) was dissolved in tetrahydrofuran (5 mL), and a tetrahydrofuran solution of cyclopentadienyl sodium CpNa (0.05 mL, 2 mol / L) was added dropwise. After the addition was complete, the mixture was stirred at room temperature for 24 hours. After the reaction was complete, the mixture was filtered through diatomaceous earth, the solvent was removed under reduced pressure, and the mixture was washed with n-hexane to remove the residual solvent, yielding an orange solid product, the dicyclopentadienylcerium complex. Yield 92%. Elemental analysis, C 39 H 50 Calculated CeN2 values: C 68.19; H 7.34; N 4.08, measured values: C 68.13; H 7.28; N 3.98.

[0051] Example 7

[0052] This embodiment provides a β-diimine lithium complex, the synthesis method of which is as follows:

[0053] The steps and parameters are the same as in Example 6, except that sodium cyclopentadienyl is replaced with 2,6-diisopropylaniline lithium DippNHLi, and tetrahydrofuran is used as the solvent to obtain a white solid product, β-diimine lithium complex. Yield 94%. Elemental analysis, C 33 H 49 Calculated LiN2O values: C 79.80; H 9.94; N 5.64; Measured values: C 79.73; H 9.86; N 5.58.

[0054] The single-crystal structure diagrams of the complexes prepared in Examples 1-7 are shown in the attached figures. Figures 1-7 As shown, its crystal data are presented in Tables 1 and 2:

[0055] Table 1: Crystal structure data of cerium complexes

[0056]

[0057]

[0058] Table 2: Crystal structure data of coordination compounds

[0059]

Claims

1. The application of a β-diimine cerium complex in salt elimination reactions, characterized in that, The specific steps of the salt elimination reaction are as follows: The β-diimine cerium complex was placed in a solvent, and sodium cyclopentadienyl or lithium 2,6-diisopropylaniline was added and stirred at room temperature. After post-treatment, the target product was obtained. The structural formula of the β-diimine cerium complex is shown in formula (I), and the structural formula of the target product is shown in formula (II) or formula (III). (I), (II) (Ⅲ), of which for .

2. The application of the β-diimine cerium complex according to claim 1 in salt elimination reactions, characterized in that, The solvent is tetrahydrofuran, the molar ratio of β-diimine cerium complex to cyclopentadienyl sodium is 1:2~2.1, and the molar ratio of β-diimine cerium complex to 2,6-diisopropylaniline lithium is 1:1.05~1.

1.

3. The application of the β-diimine cerium complex according to claim 1 in salt elimination reactions, characterized in that, The room temperature stirring reaction time in the salt elimination reaction is 12-24 h, and the post-processing steps are: diatomaceous earth filtration, solvent removal under reduced pressure, vacuum drying, and washing with n-hexane to remove residual solvent to obtain the target solid product.

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