A process for the preparation of dicarbonyl cyclopentadienyl cobalt

Abstract

The application discloses a preparation method of dicarbonyl cyclopentadienyl cobalt, which uses octacarbonyldicobalt, elemental iodine and cyclopentadienyl alkali metal salt as core reaction raw materials to prepare the dicarbonyl cyclopentadienyl cobalt. By introducing the elemental iodine and adopting the feeding sequence of first adding the cyclopentadienyl alkali metal salt and then adding the elemental iodine, the target product can be prepared under the conditions of low-temperature feeding and room-temperature reaction. The method not only avoids directly using the chemically active cyclopentadiene monomer, but also significantly reduces or avoids the generation of a cobalt-containing byproduct, reduces the diversion of part of the cobalt raw material to the byproduct side, improves the cobalt atom utilization rate and process repeatability, and is more convenient for post-processing, so that the target product with high purity can be obtained.

Description

Technical Field

[0001] This invention relates to the field of organometallic compound preparation technology, specifically to a method for preparing dicarbonylcyclopentadienyl cobalt. Background Technology

[0002] Dicarbonylcyclopentadienylcobalt (CpCo(CO)2) is a typical organometallic cobalt compound with unsaturated coordination sites and dissociable carbonyl ligands in its molecule. It has high application value in organic synthesis and homogeneous catalysis, and is also widely used in coordination chemistry research, metal-organic framework material synthesis and semiconductor precursor preparation.

[0003] In existing technologies, earlier preparation methods typically use cyclopentadiene monomers and octacarbonyl cobalt as raw materials, reacting them in an organic solvent to prepare dicarbonylcyclopentadienyl cobalt. While this method can achieve the generation of the target product, it has the following drawbacks: First, cyclopentadiene monomers are chemically highly reactive and prone to self-polymerization, polymerization, and oxidation side reactions during storage and reaction, generating dicyclopentadiene, tricyclopentadiene, and other polycyclopentadiene impurities. Second, these impurities have boiling points close to those of the target product, dicarbonylcyclopentadienyl cobalt, making complete separation by conventional distillation methods difficult, thus affecting product purity and yield. Third, the degree of cyclopentadiene monomer degradation, storage time, and trace impurities in the system all significantly affect the degree of side reactions, resulting in poor process repeatability and insufficient batch stability.

[0004] Besides the aforementioned route using cyclopentadiene monomers directly as raw materials, existing technologies also disclose preparation methods that use sodium cyclopentadienyl instead of cyclopentadiene monomers. For example, Chinese patent CN117126210A discloses a method for preparing dicarbonylcyclopentadienyl cobalt using octacarbonyldicobalt, sodium cyclopentadienyl, and tetrahydrofuran as a reaction system, under inert gas protection at 70-80 °C with stirring for 6-10 h. Although this method avoids the direct use of cyclopentadiene monomers, it still requires a relatively high temperature for the reaction, resulting in high energy consumption. Furthermore, according to its disclosed reaction formula, in addition to the target product dicarbonylcyclopentadienyl cobalt, a cobalt-containing byproduct sodium tetracarbonyl cobaltate (NaCo(CO)4) is also generated, causing some of the raw cobalt to be diverted to the byproduct side, failing to fully enter the target product, thus resulting in cobalt element loss and reduced cobalt atom utilization.

[0005] Therefore, there is an urgent need to develop a new method for preparing dicarbonylcyclopentadienyl cobalt. This method should overcome the shortcomings of the two existing technologies mentioned above, avoid the direct use of cyclopentadiene monomers, further reduce the reaction temperature, reduce or avoid the generation of cobalt-containing byproducts, reduce cobalt loss, improve cobalt atom utilization and process repeatability, and achieve simpler post-processing. Summary of the Invention

[0006] The purpose of this invention is to solve two types of technical problems existing in the preparation process of dicarbonylcyclopentadienyl cobalt: one is that when cyclopentadiene monomer is used directly as a raw material, self-polymerization and polymerization easily occur, introducing organic impurities that are difficult to separate; the other is that although the high-temperature reflux method using sodium cyclopentadienyl instead of cyclopentadiene monomer improves the stability of the raw materials, it still requires a high reaction temperature, and cobalt-containing byproducts are generated during the reaction, leading to cobalt loss and reducing the utilization rate of cobalt atoms. This invention provides a method for preparing dicarbonylcyclopentadienyl cobalt, using octacarbonyldicobalt, elemental iodine, and cyclopentadienyl alkali metal salt as core reactants, preparing dicarbonylcyclopentadienyl cobalt under low-temperature feeding and room temperature reaction conditions, significantly reducing or avoiding the generation of cobalt-containing byproducts, reducing cobalt loss, improving the utilization rate of cobalt atoms, while maintaining good process repeatability and operational stability.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0008] A method for preparing dicarbonylcyclopentadienyl cobalt includes the following steps:

[0009] Under an inert atmosphere, octacarbonyl dicobalt is mixed with an organic solvent to form a reaction system. The reaction system is cooled to 0-5 °C and then a cyclopentadienyl alkali metal salt is added. After adding elemental iodine, the reaction system is heated to 20-30 °C and stirred for 6-8 h. After the reaction is completed, the dicarbonyl cyclopentadienyl cobalt is obtained by desalting, desolventizing and purifying.

[0010] This invention uses a cyclopentadienyl alkali metal salt instead of cyclopentadiene monomer as the source of the cyclopentadienyl group, thereby reducing the chance of polymerization, dimerization, and other side reactions of the cyclopentadiene monomer under reaction conditions, and reducing the impact of polycyclopentadiene impurities on the purity of the target product and the post-processing. This invention employs a feeding sequence of first adding the cyclopentadienyl alkali metal salt and then adding elemental iodine, allowing the reaction to proceed at low temperature and room temperature. This avoids the direct reaction between elemental iodine and octacarbonyldicobalt, which could trigger unfavorable side reactions, and promotes the directed formation of the target product, dicarbonylcyclopentadienylcobalt. Simultaneously, because the reaction system of this invention significantly reduces the formation of cobalt-containing byproducts, it effectively reduces cobalt element loss.

[0011] Compared with existing high-temperature reflux NaCp routes, this invention not only retains the advantage of not directly using cyclopentadiene monomers, but also significantly reduces or avoids the generation of cobalt-containing byproducts, thereby reducing cobalt loss and improving cobalt atom utilization.

[0012] Furthermore, the molar ratio of the octacarbonyl cobalt, elemental iodine, and cyclopentadienyl alkali metal salt is 1:(0.9-1.1):(1.8-2.2).

[0013] Furthermore, the cyclopentadienyl alkali metal salt is cyclopentadienyl sodium, cyclopentadienyl lithium, or cyclopentadienyl potassium, preferably cyclopentadienyl sodium. The efficient preparation of the target product can be achieved using cyclopentadienyl sodium, cyclopentadienyl lithium, or cyclopentadienyl potassium, demonstrating the excellent applicability of this method to raw materials.

[0014] Furthermore, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0015] Furthermore, the organic solvent is selected from one or more of tetrahydrofuran, diethyl ether, toluene, 2-methyltetrahydrofuran, n-hexane, and dichloromethane, preferably tetrahydrofuran. The role of the organic solvent is to dissolve or disperse the reactants, improve the homogeneity of the reaction system, and promote the reaction.

[0016] Furthermore, the purification process employs vacuum distillation, column chromatography, or low-temperature precipitation, with vacuum distillation being the preferred method.

[0017] Furthermore, the method of adding elemental iodine is as follows: first, elemental iodine is dissolved in an organic solvent to obtain an iodine solution, and then the iodine solution is added to the reaction system.

[0018] Elemental iodine is the core functional raw material in the reaction system of this invention, playing a dual crucial role as a mild oxidant and an alkali metal ion scavenger: Firstly, as a mild oxidant, it can oxidize the 0-valent cobalt in octacarbonyl cobalt to +1-valent cobalt ions, enabling it to efficiently combine with the cyclopentadienyl anions provided by cyclopentadienyl sodium to directionally generate the target product dicarbonylcyclopentadienyl cobalt; secondly, during the oxidation of 0-valent cobalt to +1-valent cobalt ions, elemental iodine is simultaneously reduced to -1-valent iodide ions, which can combine in situ with sodium ions in cyclopentadienyl sodium to form sodium iodide solid precipitate and escape from the reaction system, ensuring that the reaction satisfies valence equilibrium and electron conservation throughout, making the reaction system more stable and controllable; thirdly, the combination of iodide ions and sodium ions to form sodium iodide precipitate can fundamentally avoid the generation of harmful cobalt-containing byproducts such as NaCo(CO)4, significantly improving the utilization rate of cobalt atoms, and thus greatly increasing the yield of the target product.

[0019] Compared to conventional oxidants that only have a single oxidation function, the iodine used in this invention has both oxidation regulation and sodium ion capture functions, which can effectively suppress the formation of by-products, improve atom economy and reaction yield.

[0020] In a specific embodiment, the elemental iodine is pre-dissolved in an organic solvent before being added to the reaction system, and is added to the reaction system by dropping or slowly adding; the organic solvent is selected from one or more of tetrahydrofuran, diethyl ether, toluene, 2-methyltetrahydrofuran, n-hexane and dichloromethane.

[0021] In a specific embodiment, the preparation method of the dicarbonylcyclopentadienyl cobalt includes the following steps: adding octacarbonyl cobalt to a reaction flask, adding an organic solvent under an inert atmosphere to form a reaction system; cooling the reaction system to 0-5 °C, adding a cyclopentadienyl alkali metal salt while stirring; slowly adding elemental iodine to the reaction system to allow it to react fully with octacarbonyl cobalt and the cyclopentadienyl alkali metal salt; after the addition is complete, heating the reaction system to 20-30 °C and continuing to stir the reaction for 6-8 h; after the reaction is complete, filtering to remove inorganic salt byproducts, collecting the filtrate and removing the solvent under reduced pressure to obtain a crude product; purifying the crude product, collecting the target product, and obtaining the dicarbonylcyclopentadienyl cobalt.

[0022] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0023] 1. On the one hand, this invention avoids the direct use of chemically active cyclopentadiene monomers, reducing cyclopentadiene self-polymerization, polymerization, and other related side reactions; on the other hand, it differs from the existing high-temperature reflux NaCp route by introducing elemental iodine and adopting a specific feeding sequence, enabling the reaction to proceed under low-temperature feeding and room-temperature conditions, and significantly reducing the formation of cobalt-containing byproducts, thereby reducing cobalt loss and improving the effective conversion rate of cobalt to the target product and the utilization rate of cobalt atoms.

[0024] 2. This invention uses cyclopentadienyl alkali metal salts to replace cyclopentadiene monomers as the source of cyclopentadienyl groups, avoiding the direct use of chemically active cyclopentadiene monomers. This reduces the occurrence of cyclopentadiene self-polymerization, polymerization, and other related side reactions from the reaction source, and reduces the adverse effects of polycyclopentadiene impurities on the purity of the target product and the post-processing.

[0025] 3. This invention constructs a ternary reaction system with octacarbonyl cobalt, elemental iodine and cyclopentadienyl alkali metal salt as core raw materials. The reaction byproducts are mainly inorganic salts. Post-processing can be completed by simple filtration and vacuum distillation. The operation is simple, the process has good repeatability, and it is conducive to scale-up production. Attached Figure Description

[0026] Figure 1 The image shows the NMR data of the dicarbonylcyclopentadienyl cobalt prepared in Example 1.

[0027] Figure 2 The image shows the NMR data of the dicarbonylcyclopentadienyl cobalt prepared in Comparative Example 1. Detailed Implementation

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] This invention provides a method for preparing dicarbonylcyclopentadienyl cobalt, comprising the following steps: using octacarbonyl cobalt, elemental iodine and cyclopentadienyl alkali metal salt as raw materials, reacting them in an organic solvent under an inert atmosphere, and after the reaction is completed, undergoing desalting, solvent removal and purification treatment to obtain the dicarbonylcyclopentadienyl cobalt.

[0030] In one embodiment of the present invention, the reaction route for preparing dicarbonylcyclopentadienyl cobalt is as follows:

[0031] .

[0032] This invention uses octacarbonyl cobalt, elemental iodine, and cyclopentadienyl alkali metal salt as raw materials, and carries out the reaction under an inert atmosphere. Preferably, the molar ratio of octacarbonyl cobalt, elemental iodine, and cyclopentadienyl alkali metal salt in the reaction is 1:1:2, and finally dicarbonylcyclopentadienyl cobalt and the corresponding alkali metal iodide are obtained.

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0035] Example 1

[0036] A method for preparing dicarbonylcyclopentadienyl cobalt includes the following steps:

[0037] Under nitrogen protection, 136.8 g (0.40 mol) of cobalt octacarbonyl was added to a 2 L three-necked flask, followed by 800 mL of tetrahydrofuran. The mixture was stirred to form a homogeneous reaction system. The reaction system was cooled to 5 °C, and 70.4 g (0.80 mol) of sodium cyclopentadienyl was added in portions with stirring. Subsequently, 101.5 g (0.40 mol) of elemental iodine was dissolved in 200 mL of tetrahydrofuran and slowly added dropwise to the reaction system. After the addition was complete, the temperature was naturally raised to 25 °C, and the reaction was continued with stirring for 8 h. After the reaction, the inorganic salt byproducts were removed by filtration in a glove box and the product was washed with tetrahydrofuran solvent. The filtrate was collected and the tetrahydrofuran solvent was removed under reduced pressure (2 mmHg) at room temperature. The crude product was purified by vacuum distillation at 30 °C and 2 mmHg. The target fraction was collected to obtain a deep red liquid dicarbonylcyclopentadienyl cobalt with a yield of 85.0%. ICP-MS analysis showed a metal purity of 6N. NMR data were as follows: 1 1H NMR (400 MHz, C6D6) δ 4.41 (s, 5H, Cp-H), NMR data as shown in the figure. Figure 1 As shown. No separable cobalt-containing byproducts were detected in Example 1.

[0038] Example 2

[0039] A method for preparing dicarbonylcyclopentadienyl cobalt includes the following steps:

[0040] Under nitrogen protection, 136.8 g (0.40 mol) of cobalt octacarbonyl was added to a 2 L three-necked flask, followed by 800 mL of tetrahydrofuran. The mixture was stirred to form a homogeneous reaction system. The reaction system was cooled to 5 °C, and 57.6 g (0.80 mol) of cyclopentadienyllithium was added in portions with stirring. Subsequently, 101.5 g (0.40 mol) of elemental iodine was dissolved in 200 mL of tetrahydrofuran and slowly added dropwise to the reaction system. After the addition was complete, the temperature was naturally raised to 25 °C, and the reaction was continued with stirring for 8 h. After the reaction, the inorganic salt byproducts were removed by filtration in a glove box and the product was washed with tetrahydrofuran solvent. The filtrate was collected and the tetrahydrofuran solvent was removed under reduced pressure (2 mmHg) at room temperature. The crude product was purified by vacuum distillation at 30 °C and 2 mmHg. The target fraction was collected to obtain a deep red liquid dicarbonylcyclopentadienyl cobalt with a yield of 82.0%. ICP-MS analysis showed a metal purity of 6N. NMR data were as follows: 1 ¹H NMR (400 MHz, C6D6) δ 4.41 (s, 5H, Cp-H). No separable cobalt-containing byproducts were detected in Example 2.

[0041] Example 3

[0042] A method for preparing dicarbonylcyclopentadienyl cobalt includes the following steps:

[0043] Under nitrogen protection, 136.8 g (0.40 mol) of cobalt octacarbonyl was added to a 2 L three-necked flask, followed by 800 mL of tetrahydrofuran. The mixture was stirred to form a homogeneous reaction system. The reaction system was cooled to 5 °C, and 83.4 g (0.80 mol) of potassium cyclopentadienyl was added in portions with stirring. Subsequently, 101.5 g (0.40 mol) of elemental iodine was dissolved in 200 mL of tetrahydrofuran and slowly added dropwise to the reaction system. After the addition was complete, the temperature was naturally raised to 25 °C, and the reaction was continued with stirring for 8 h. After the reaction, the inorganic salt byproducts were removed by filtration in a glove box and the product was washed with tetrahydrofuran solvent. The filtrate was collected and the tetrahydrofuran solvent was removed under reduced pressure (2 mmHg) at room temperature. The crude product was purified by vacuum distillation at 30 °C and 2 mmHg. The target fraction was collected to obtain a deep red liquid dicarbonylcyclopentadienyl cobalt with a yield of 80.0%. ICP-MS analysis showed a metal purity of 6N. NMR data were as follows: 1 ¹H NMR (400 MHz, C6D6) δ 4.41 (s, 5H, Cp-H). No separable cobalt-containing byproducts were detected in Example 3.

[0044] Comparative Example 1

[0045] A method for preparing dicarbonylcyclopentadienyl cobalt includes the following steps:

[0046] Under nitrogen protection, 136.8 g (0.40 mol) of octacarbonyl cobalt was added to a 2 L three-necked flask, followed by 800 mL of tetrahydrofuran. The mixture was stirred to form a homogeneous reaction system. Then, 52.8 g (0.80 mol) of freshly cleaved cyclopentadiene monomer was added to the reaction system, and the reaction was continued at 25 °C with stirring for 8 h. After the reaction was complete, the reaction solution was collected, and the tetrahydrofuran solvent was removed under reduced pressure (2 mmHg) at room temperature. The crude product was purified by vacuum distillation at 30 °C and 2 mmHg. The target fraction was collected to obtain a deep red liquid dicarbonylcyclopentadienyl cobalt with a yield of 58.0%. ICP-MS analysis showed a metal purity of 5N. NMR data were as follows: 1 ¹H NMR (400 MHz, C6D6) δ 4.41 (s, 5H, Cp-H), accompanied by other impurity peaks. The NMR data is shown in the figure below. Figure 2As shown. Compared with Examples 1-3, Comparative Example 1 directly uses freshly pyrolyzed cyclopentadiene monomer as the source of cyclopentadienyl groups. During the reaction, a large amount of polycyclopentadiene and other cyclopentadiene-derived organic impurities are generated. These impurities have boiling points similar to the target product, resulting in obvious fraction tailing during vacuum distillation. The target fraction and impurities are difficult to separate effectively, and the post-processing difficulty is significantly increased.

[0047] Comparative Example 2

[0048] A method for preparing dicarbonylcyclopentadienyl cobalt (CN117126210A) includes the following steps:

[0049] Under nitrogen protection, 136.8 g (0.40 mol) of octacarbonyl cobalt was added to a 2 L three-necked flask, followed by 240 mL of tetrahydrofuran. The mixture was stirred to form a homogeneous reaction system. Then, 300 mL (2.0 M, 0.60 mol) of a tetrahydrofuran solution of sodium cyclopentadienyl was added dropwise to the reaction system. After the addition was complete, the temperature was raised to 75 °C and maintained at 75 °C with stirring for 8 h. After the reaction was complete, the tetrahydrofuran was first distilled off under normal pressure, followed by purification by distillation under reduced pressure to obtain a deep red liquid dicarbonylcyclopentadienyl cobalt with a yield of 45.0%. ICP-MS analysis showed a metal purity of 5N. NMR data were as follows: 1 H NMR (400MHz, C6D 6) δ 4.41 (s, 5H, Cp-H), accompanied by other extraneous peaks.

[0050] Compared to Examples 1-3, Comparative Example 2, while avoiding the direct use of cyclopentadiene monomer, still employs a high-temperature reflux reaction. This reaction involves the cobalt-containing byproduct sodium tetracarbonyl cobaltate (NaCo(CO)4), which is detrimental to improving cobalt atom utilization. In contrast, this invention introduces elemental iodine and adopts a feeding sequence of first adding the cyclopentadienyl alkali metal salt and then adding elemental iodine. This allows for the preparation of the target product under low-temperature feeding and room-temperature reaction conditions, significantly reducing the formation of cobalt-containing byproducts in the reaction system, thereby effectively improving cobalt atom utilization and reducing post-processing difficulty.

[0051] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing dicarbonylcyclopentadienyl cobalt, characterized in that, Includes the following steps: Under an inert atmosphere, octacarbonyl dicobalt is mixed with an organic solvent to form a reaction system. The reaction system is cooled to 0-5 °C and then a cyclopentadienyl alkali metal salt is added. After adding elemental iodine, the reaction system is heated to 20-30 °C and stirred for 6-8 h. After the reaction is completed, the dicarbonyl cyclopentadienyl cobalt is obtained by desalting, desolventizing and purifying.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the octacarbonyl cobalt, elemental iodine and cyclopentadienyl alkali metal salt is 1:(0.9-1.1):(1.8-2.2).

3. The preparation method according to claim 1, characterized in that, The cyclopentadienyl alkali metal salt is cyclopentadienyl sodium, cyclopentadienyl lithium, or cyclopentadienyl potassium.

4. The preparation method according to claim 1, characterized in that, The inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

5. The preparation method according to claim 1, characterized in that, The organic solvent is selected from one or more of tetrahydrofuran, diethyl ether, toluene, 2-methyltetrahydrofuran, n-hexane, and dichloromethane.

6. The preparation method according to claim 1, characterized in that, The purification process employs methods such as vacuum distillation, column chromatography, or low-temperature precipitation.

7. The preparation method according to claim 1, characterized in that, The method of adding elemental iodine is as follows: first, elemental iodine is dissolved in an organic solvent to obtain an iodine solution, and then the iodine solution is added to the reaction system.

8. The preparation method according to claim 1, characterized in that, After the reaction is complete, the inorganic salt byproducts are removed by filtration, the filtrate is collected and the solvent is removed under reduced pressure to obtain the crude product; the crude product is purified to obtain the dicarbonylcyclopentadienyl cobalt.

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