Preparation method of bis (alkyl cyclopentadiene) metal complex

Abstract

The invention discloses a preparation method of a bis (alkyl cyclopentadiene) metal complex, which comprises the following steps: obtaining a reaction solution for preparing alkyl cyclopentadiene and carrying out rectification treatment, impurities of the reaction solution mainly comprise cyclopentadiene, a cyclopentadiene dimer, an alkyl cyclopentadiene dimer and impurities generated by mutual polymerization of cyclopentadiene and alkyl cyclopentadiene, purifying the alkyl cyclopentadiene through rectification; and dissolving the purified alkyl cyclopentadiene at low temperature, and adding zinc powder and metal chloride to obtain the bis (alkyl cyclopentadiene) metal complex. The invention provides a method for synthesizing a bis (alkyl cyclopentadiene) metal complex from purified alkyl cyclopentadiene by carrying out low-temperature rectification purification treatment on a reaction solution of alkyl cyclopentadiene. The low-temperature rectification and the addition of the polymerization inhibitor can prevent the polymerization of the alkyl cyclopentadiene, thereby solving the bottleneck problem of the process route for synthesizing the bis (alkyl cyclopentadiene) metal complex from the alkyl cyclopentadiene.

Description

Technical Field

[0001] The invention relates to the technical field of metal organic compound synthesis, and in particular to a method for preparing a bis(alkylcyclopentadienyl) metal complex. Background Art

[0002] Bis(cyclopentadienyl)metal complexes are an important class of metal organic compounds, such as bis(ethylcyclopentadienyl)ruthenium, which can be used as precursors for atomic layer deposition to deposit ruthenium metal or ruthenium-containing films.

[0003] Patent US20010056198A1 discloses a method for preparing bis(ethylcyclopentadiene)ruthenium, which is obtained by reacting alkylcyclopentadiene, ruthenium chloride and zinc powder in an alcohol solvent. To obtain a high-purity bis(ethylcyclopentadiene)ruthenium product, it depends on the improvement of the purity of the reactants. However, since cyclopentadiene and its derivatives are easily dimerized when heated, they are easily dimerized in the tower and at the top of the tower when separated and purified by conventional distillation methods. To obtain high-purity alkylcyclopentadiene, the prior art usually cracks the raw materials, but the cracking temperature is high and there are many by-products. Therefore, the process of preparing bis(ethylcyclopentadiene)ruthenium using the above method is relatively complicated. In this regard, patent CN1155607C proposes another synthetic route, that is, using bis(cyclopentadiene)ruthenium as a raw material and adding bromoethane to obtain bis(ethylcyclopentadiene)ruthenium. This method has also become a common method for preparing bis(ethylcyclopentadiene)ruthenium. However, this method requires the addition of butyl lithium for a hydrogen-lithium exchange reaction during the preparation process, which is relatively dangerous; at the same time, the cost of the raw material di(cyclopentadienyl)ruthenium is also relatively high. Summary of the invention

[0004] The present invention provides a method for preparing a bis(alkylcyclopentadienyl) metal complex represented by formula (I), wherein formula (I) is: M(RCp) 2 (I) Wherein, M is a metal, R is an alkyl group having 1 to 4 carbon atoms, and Cp is a cyclopentadienyl group; the method comprises the following steps: preparing alkyl cyclopentadiene, and performing distillation and purification on the reaction liquid of the prepared alkyl cyclopentadiene, wherein the distillation pressure is less than 15 kPa, and an alkyl cyclopentadiene raw material with a purity of more than 99% is obtained; o C or below, the alkylcyclopentadiene raw material is dissolved and reacted with zinc powder and chloride of metal M to obtain a bis(alkylcyclopentadienyl)metal complex.

[0005] Preferably, the alkylcyclopentadiene is obtained by reacting sodium cyclopentadiene with RBr.

[0006] Preferably, the specific preparation process of alkyl cyclopentadiene is to dissolve sodium cyclopentadiene in a solvent, add RBr to react, and control the reaction temperature to be less than 5o C.

[0007] Preferably, M is a Group I, Group II, Group III metal or a transition metal.

[0008] Preferably, M is Ru, Mn, Fe, Ba, Co, Rh or Ir.

[0009] Preferably, R is ethyl.

[0010] Preferably, the rectification purification specifically includes two stages: low-pressure rectification to separate the solvent in the reaction solution, with the pressure of the rectification column being 15 - 5 kPa; vacuum rectification to separate the alkylcyclopentadiene in the reaction solution, with the pressure of the rectification column being 5 - 1 kPa.

[0011] Preferably, before rectification purification of the reaction solution of the prepared alkylcyclopentadiene, a molecular inhibitor is added to the reaction solution in an amount of 0.1 - 1 wt% of the reaction solution, preferably p-benzoquinone or hydroquinone accounting for 0.3 wt% of the reaction solution.

[0012] Preferably, before rectification purification of the reaction solution of the prepared alkylcyclopentadiene, a diluent is added to the reaction solution in an amount of 50 - 80 wt% of the reaction solution. The boiling point of this diluent is higher than that of ethylcyclopentadiene, preferably diphenyl ether accounting for 50 wt% of the reaction solution. The inventor found that the addition of the diluent can reduce the oxidation and polymerization of ethylcyclopentadiene, which is beneficial to further improving the purity of ethylcyclopentadiene.

[0013] Preferably, during the rectification purification of the reaction solution of the prepared alkylcyclopentadiene, the temperature range of the bottom of the column is 25 - 45 °C.

[0014] Preferably, the impurities in the reaction solution of the prepared alkylcyclopentadiene are mainly cyclopentadiene, cyclopentadiene dimer, alkylcyclopentadiene dimer, and the impurities formed by the polymerization of cyclopentadiene and alkylcyclopentadiene with each other.

[0015] The remarkable advantages of the present invention are as follows: The present invention provides a new method for preparing bis(alkylcyclopentadienyl) metal complexes from alkylcyclopentadiene. This method is to carry out vacuum rectification purification on the reaction solution of alkylcyclopentadiene. By vacuum rectification and the addition of an inhibitor, the polymerization of alkylcyclopentadiene during rectification can be prevented, thus solving the bottleneck problem of the process route for synthesizing bis(alkylcyclopentadienyl) metal complexes from alkylcyclopentadiene. Description of the Drawings

[0016] Figure 1 is the GC (gas chromatography) diagram of the reaction solution of ethylcyclopentadiene; Figure 2 is the GC diagram after rectification purification of ethylcyclopentadiene; Figure 3 It is the GC chart of crude bis(ethylcyclopentadienyl)ruthenium; Figure 4 It is the GC chart of bis(ethylcyclopentadienyl)ruthenium product; Figure 5 It is the GC chart of the product obtained in Comparative Example 1. Specific Embodiments

[0017] To make the above features and advantages of the present invention more obvious and understandable, specific embodiments are given below for detailed description. Unless otherwise specified, the methods of the present invention are conventional methods in the art.

[0018] The present invention relates to a method for preparing a bis(alkylcyclopentadienyl) metal complex represented by formula (I), M(RCp) 2 (I) In formula (I), M is a metal, specifically it can be ruthenium, manganese, cobalt, preferably ruthenium. R is an alkyl group of C 1-4 , for example, CH 3 (methyl), C 2 H 5 (ethyl), C 3 H 7 (n-propyl or isopropyl) or C 4 H 9 (n-butyl, isobutyl or tert-butyl), preferably ethyl. Cp is cyclopentadienyl. In a preferred embodiment, bis(ethylcyclopentadienyl)ruthenium is synthesized by the method of the present invention, and the structural formula is as follows: In a specific embodiment, the present invention prepares ethylcyclopentadiene, and the reaction solution of the prepared ethylcyclopentadiene is purified by vacuum distillation. The distillation pressure < 15 kPa to obtain an ethylcyclopentadiene raw material with a purity > 99%; at 0 o °C or below, the ethylcyclopentadiene raw material is dissolved and reacted with zinc powder and ruthenium chloride to obtain bis(ethylcyclopentadienyl)ruthenium. Ethylcyclopentadiene can be prepared by known methods, specifically, for example, by reacting sodium cyclopentadienide with bromoethane. Sodium cyclopentadienide is dissolved in a solvent, and bromoethane is added for reaction, and the reaction temperature is controlled at < 5 o °C.

[0019] Generally, there are many impurities in the reaction solution for synthesizing ethyl cyclopentadiene, such as unreacted raw materials like cyclopentadiene and bromoethane, as well as a small amount of solvent. There are also cyclopentadiene dimers, product dimers, and polymers formed by the polymerization of cyclopentadiene and ethyl cyclopentadiene in pairs. Conventional distillation separation methods have a relatively high temperature, which easily causes the polymerization of the product ethyl cyclopentadiene, resulting in an increase in by-products and a decrease in yield. In this example, alkyl cyclopentadiene is purified by vacuum distillation. During the distillation process, the temperature is relatively low, which can reduce the occurrence of polymerization during the purification process.

[0020] In a specific example, the temperature of the distillation column kettle is 25 - 45 °C, and the temperature at the top of the column is 17 - 31 °C, preferably cooled by liquid nitrogen. The kettle increases the mixing through stirring. During the distillation process, in the first stage, the pressure in the column drops from 15 kPa to 5 kPa to remove a small amount of light components. The light components are generally bromoethane, cyclopentadiene, and the solvent tetrahydrofuran. After the light components are basically removed, it enters the second stage, and the pressure in the column gradually drops from 5 kPa to 1 kPa, and the product ethyl cyclopentadiene is extracted.

[0021] In a preferred example, a polymerization inhibitor is added to the reaction solution of ethyl cyclopentadiene to further prevent the polymerization of ethyl cyclopentadiene. The polymerization inhibitor can be a conventional molecular-type polymerization inhibitor, such as hydroquinone, benzoquinone, phenothiazine, β-phenylnaphthylamine, p-tert-butylcatechol, methylene blue, cuprous chloride, ferric trichloride, etc. The content range of the polymerization inhibitor is preferably 0.1 wt% - 1 wt%.

[0022] In a preferred example, adding a diluent to the reaction solution of ethyl cyclopentadiene or the middle section of the distillation column can also reduce the polymerization of ethyl cyclopentadiene. The diluent can be a high-boiling solvent, such as diphenyl ether, white oil, etc. The content range of the diluent is 50 wt% - 80 wt%.

[0023] Example 1.1 Synthesis of Ethyl Cyclopentadiene 20 g of sodium cyclopentadienide was dissolved in tetrahydrofuran (THF) to prepare a 1 M sodium cyclopentadienide solution. The temperature of the system was lowered to 0 o °C, and 33 g of bromoethane was added dropwise to the solution. During the process, the temperature was controlled not to exceed 5 °C. After the addition, the reaction continued for 2 h and then the reaction ended. The solvent was removed under reduced pressure to obtain 22.3 g of crude ethyl cyclopentadiene product with a purity of 77.35 wt%.

[0024] Figure 1 The chromatogram of the reaction solution of the synthesized ethyl cyclopentadiene, in which the impurities include unreacted raw materials such as cyclopentadiene and bromoethane, as well as a small amount of solvent, and there are also cyclopentadiene dimers, product dimers, and polymers formed by the polymerization of cyclopentadiene and ethyl cyclopentadiene in pairs. Therefore, distillation is required to obtain high-purity ethyl cyclopentadiene.

[0025] Example 1.2 Distillation Separation of Ethyl Cyclopentadiene The crude ethylcyclopentadiene in Example 1.1 was mixed with diphenyl ether at a volume ratio of 1:2, and 0.2 wt% of p-benzoquinone (polymerization inhibitor) based on the total mass of the solution was added to the bottom of the tower. The refrigeration system was turned on, the vacuum was turned on, the heating and insulation of the bottom of the tower were turned on, and the mixed solution of ethylcyclopentadiene and diphenyl ether was added to the distillation tower bottom. Then, a diphenyl ether solution containing 0.2 wt% of p-benzoquinone (polymerization inhibitor) was fed into the middle of the tower at a flow rate of 5 mL / min by a peristaltic pump.

[0026] In the first stage of vacuum, the pressure dropped from 15 kPa to 5 kPa, the bottom temperature of the tower was 35 °C, and the gas-phase temperature was 17 °C - 19 °C. The fraction was quickly collected, and the fraction composition was bromoethane, cyclopentadiene, and the solvent tetrahydrofuran.

[0027] In the second stage of vacuum, the pressure dropped from 5 kPa to 1 kPa, the bottom temperature of the tower was 35 °C, and the gas-phase temperature was 25 °C - 31 °C. The fraction was quickly collected, and the fraction composition was mainly the product ethylcyclopentadiene. This condition was maintained until no fraction was collected.

[0028] Through the above operations in the first and second stages of vacuum, 15.2 g of ethylcyclopentadiene was obtained, with a yield of 88.2% and a product purity of 99.5 wt%. As Figure 2 shown, the main impurities, such as dimers, etc., have been basically removed.

[0029] Example 1.3 Synthesis of bis(ethylcyclopentadienyl)ruthenium 15.2 g of the purified ethylcyclopentadiene in Example 1.2 was dissolved in 145 g of ethanol and cooled to -20 °C, and then 27.7 g of zinc powder was added to prepare Solution A for standby; 14 g of ruthenium trichloride was dissolved in 145 g of ethanol, filtered and then added dropwise to Solution A, and the temperature was controlled not to exceed -18 °C during the dropping process. After the dropping was completed, the reaction continued for 5 h to end the reaction.

[0030] The reaction solution was subjected to vacuum desolvation. After desolvation, 100 ml of n-hexane was added for stirring extraction, and the upper layer was taken after stratification and subjected to vacuum desolvation to obtain 18.4 g of the crude product. The chromatogram of the crude product is as Figure 3 shown.

[0031] The crude product was distilled, the heating temperature was 140 °C - 160 °C, the vacuum was below 100 Pa, and the gas-phase temperature was 100 - 110 °C to obtain 15.36 g of the product bis(ethylcyclopentadienyl)ruthenium, with a purity of 99.9 wt% and a yield of 86.1%. The chromatogram of the product is as Figure 4 shown.

[0032] Example 2 In the preparation processes of Examples 1.1, 1.2, and 1.3, the ethyl bromide in Example 1.1 was replaced with ethyl iodide, and the p-benzoquinone in Example 1.2 was replaced with 0.3 wt% hydroquinone, and the remaining operations were the same as those in Examples 1.1, 1.2, and 1.3.

[0033] 2.1 25.3 g of crude ethylcyclopentadiene was obtained, with a content of 82.36%; 2.2 18.76 g of ethylcyclopentadiene was obtained, with a content of 99.4% and a yield of 89.52%; 2.3 20.32 g of the product bis(ethylcyclopentadienyl)ruthenium was obtained, with a content of 99.9% and a yield of 92.3%.

[0034] Example 3 In the preparation processes of Examples 1.1, 1.2, and 1.3, the distillation heating temperature in 3.2 was changed to 45 °C, and the remaining operations were the same as those in Examples 1.1, 1.2, and 1.3.

[0035] 3.1 22.1 g of crude ethylcyclopentadiene was obtained, with a content of 80.11% (different batches); 3.2 15.5 g of ethylcyclopentadiene was obtained, with a content of 99.6% and a yield of 87.2%; 3.3 16.2 g of the product bis(ethylcyclopentadienyl)ruthenium was obtained, with a content of 99.9% and a yield of 89.2%.

[0036] Example 4 According to the preparation processes of Examples 1.1, 1.2, and 1.3, in the distillation step of Example 1.2, the crude product was directly distilled without adding the diluent diphenyl ether, and the remaining operations were exactly the same as those in Example 1.

[0037] 4.1 22.3 g of crude ethylcyclopentadiene was obtained, with a purity of 77.35 wt% (the same as in Example 1.1).

[0038] 4.2 After distillation, 14.8 g of ethylcyclopentadiene was obtained, with a purity of 99.2 wt% and a yield of 86.1%.

[0039] 4.3 14.9 g of bis(ethylcyclopentadienyl)ruthenium was synthesized, with a purity of 99.9 wt% and a yield of 83.5%.

[0040] Comparative Example 1 Synthesis of bis(ethylcyclopentadienyl)ruthenium 15.2 g of the crude ethylcyclopentadiene obtained in Example 1.1 was dissolved in 145 g of ethanol, cooled to -20 °C, and then 27.7 g of zinc powder was added to prepare Solution A for standby; 14 g of ruthenium trichloride was dissolved in 145 g of ethanol, filtered, and then added dropwise to Solution A. The temperature was controlled not to exceed -18 °C during the dropping process. After the dropping was completed, the reaction was continued for 5 h to end the reaction.

[0041] The chromatogram of the obtained product is as follows Figure 5As shown, there is a by-product, 1-ethylcyclopentadienyl ruthenium, and it is difficult to remove this by-product.

[0042] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing a bis(alkylcyclopentadienyl) metal complex, characterized in that: The chemical formula of the bis(alkylcyclopentadienyl) metal complex is shown in formula (I): M(RCp)2 (I) Wherein, M is a metal, R is an alkyl group having 1 to 4 carbon atoms, and Cp is a cyclopentadienyl group; the preparation method comprises the following steps: Prepare alkylcyclopentadiene, and purify the reaction solution of the prepared alkylcyclopentadiene by vacuum distillation, wherein the distillation pressure is less than 15 kPa, to obtain alkylcyclopentadiene raw material with a purity of more than 99%; At 0 o C or below, the alkylcyclopentadiene raw material is dissolved and reacted with zinc powder and chloride of metal M to obtain a bis(alkylcyclopentadienyl)metal complex.

2. The method according to claim 1, characterized in that Alkylcyclopentadiene is obtained by reacting sodium cyclopentadiene with RBr, wherein R is an alkyl group having 1 to 4 carbon atoms.

3. The method according to claim 2, characterized in that The specific preparation process of alkyl cyclopentadiene is to dissolve sodium cyclopentadiene in a solvent, add RBr to react, and control the reaction temperature to <5 o C.

4. The method according to claim 1, characterized in that Wherein M is a metal of Group I, Group II, Group III or a transition metal.

5. The method according to claim 4, characterized in that wherein M is Ru, Mn, Fe, Ba, Co, Rh or Ir.

6. The method according to claim 1, characterized in that Wherein R is ethyl.

7. The method according to claim 1, characterized in that The distillation purification specifically includes the following two stages: Low-pressure distillation to separate the solvent from the reaction liquid, the distillation tower pressure is 15-5kPa; The alkyl cyclopentadiene in the reaction solution is separated by vacuum distillation, and the pressure of the distillation tower is 5-1kPa.

8. The method according to claim 1, characterized in that Before the reaction liquid of the prepared alkylcyclopentadiene is distilled and purified, a molecular polymerization inhibitor accounting for 0.1-1 wt % of the reaction liquid is added to the reaction liquid.

9. The method according to claim 1, characterized in that: Before the reaction liquid of the prepared alkylcyclopentadiene is subjected to rectification and purification, a diluent accounting for 50-80 wt % of the reaction liquid is added to the reaction liquid, wherein the boiling point of the diluent is higher than that of the ethylcyclopentadiene.

10. The method according to claim 1, characterized in that During the distillation and purification process of the reaction liquid of the prepared alkylcyclopentadiene, the temperature of the bottom of the tower is in the range of 25-45°C.

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