A method for preparing a bis(alkylcyclopentadiene) metal complex

Abstract

The present invention discloses a method for preparing a bis(alkylcyclopentadiene)metal complex. The method involves obtaining a reaction solution from the preparation of alkylcyclopentadiene and subjecting it to distillation. Impurities in the reaction solution are primarily cyclopentadiene, cyclopentadiene dimer, alkylcyclopentadiene dimer, and impurities resulting from the polymerization of cyclopentadiene and alkylcyclopentadiene. The alkylcyclopentadiene is purified by distillation. The purified alkylcyclopentadiene is dissolved at low temperature, and zinc powder and a metal chloride are added to obtain the bis(alkylcyclopentadiene)metal complex. The present invention proposes synthesizing the bis(alkylcyclopentadiene)metal complex from the purified alkylcyclopentadiene by subjecting the reaction solution to low-temperature distillation. Low-temperature distillation and the addition of a polymerization inhibitor prevent the polymerization of the alkylcyclopentadiene, thereby resolving bottlenecks in the process of synthesizing the bis(alkylcyclopentadiene)metal complex from alkylcyclopentadiene.

Description

Technical Field

[0001] The present 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. For example, bis(ethylcyclopentadienyl)ruthenium can be used as precursors for atomic layer deposition to deposit ruthenium metal or ruthenium-containing thin films.

[0003] Patent US20010056198A1 discloses a method for preparing bis(ethylcyclopentadienyl)ruthenium by reacting alkylcyclopentadiene, ruthenium chloride, and zinc powder in an alcohol solvent. Obtaining high-purity bis(ethylcyclopentadienyl)ruthenium product relies on increasing the purity of the reactants. However, because cyclopentadiene and its derivatives readily dimerize upon heating, conventional distillation methods for separation and purification often dimerize within the column and at the top. To obtain high-purity alkylcyclopentadiene, existing techniques typically involve cracking the raw materials. However, cracking at high temperatures produces numerous byproducts, making the preparation of bis(ethylcyclopentadienyl)ruthenium using this method relatively complex. Patent CN1155607C proposes an alternative synthetic route, using bis(cyclopentadienyl)ruthenium as the raw material and reacting it with ethyl bromide to produce bis(ethylcyclopentadienyl)ruthenium. This method has become a common method for preparing bis(ethylcyclopentadienyl)ruthenium. However, this method requires the addition of butyl lithium for a hydrogen-lithium exchange reaction during the preparation process, which is highly dangerous; at the same time, the cost of the raw material bis(cyclopentadienyl)ruthenium is also 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:

[0005] M(RCp)2 (I)

[0006] 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 alkylcyclopentadiene, and performing distillation and purification on the reaction solution of the prepared alkylcyclopentadiene, wherein the distillation pressure is less than 15 kPa, and obtaining an alkylcyclopentadiene raw material with a purity greater than 99%; 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.

[0007] Preferably, the alkylcyclopentadiene is obtained by reacting sodium cyclopentadiene with RBr.

[0008] Preferably, the specific preparation process of alkylcyclopentadiene is to dissolve sodium cyclopentadiene in a solvent, add RBr to react, and control the reaction temperature to be less than 5 o C.

[0009] Preferably, M is a Group I, Group II, Group III metal or a transition metal.

[0010] Preferably, M is Ru, Mn, Fe, Ba, Co, Rh or Ir.

[0011] Preferably, R is ethyl.

[0012] Preferably, the distillation purification specifically includes two stages: low-pressure distillation to separate the solvent in the reaction liquid, and the pressure of the distillation tower is 15-5kPa; and vacuum distillation to separate the alkylcyclopentadiene in the reaction liquid, and the pressure of the distillation tower is 5-1kPa.

[0013] Preferably, before the reaction solution of the prepared alkylcyclopentadiene is subjected to distillation and purification, a molecular polymerization inhibitor accounting for 0.1-1 wt % of the reaction solution is added to the reaction solution, preferably p-benzoquinone or hydroquinone accounting for 0.3 wt % of the reaction solution.

[0014] Preferably, before the reaction solution of the prepared alkylcyclopentadiene is subjected to rectification and purification, a diluent accounting for 50-80 wt% of the reaction solution is added to the reaction solution. The diluent has a higher boiling point than that of the ethylcyclopentadiene, and preferably diphenyl ether accounting for 50 wt% of the reaction solution. The inventors have discovered that the addition of the diluent can reduce the oxidation and polymerization of the ethylcyclopentadiene, which is conducive to further improving the purity of the ethylcyclopentadiene.

[0015] Preferably, during the distillation and purification process of the reaction solution of the prepared alkylcyclopentadiene, the bottom temperature ranges from 25 to 45°C.

[0016] Preferably, the impurities in the reaction solution of the prepared alkylcyclopentadiene are mainly cyclopentadiene, cyclopentadiene dimer, alkylcyclopentadiene dimer and impurities obtained by polymerization of cyclopentadiene and alkylcyclopentadiene.

[0017] The significant advantages of the present invention are:

[0018] The present invention proposes a new method for preparing a bis(alkylcyclopentadienyl)metal complex from alkylcyclopentadiene. The method involves subjecting the reaction solution of the alkylcyclopentadiene to vacuum distillation for purification. Through vacuum distillation and the addition of a polymerization inhibitor, polymerization of the alkylcyclopentadiene during the distillation process can be prevented, thereby solving the bottleneck problem of the process route for synthesizing the bis(alkylcyclopentadienyl)metal complex from alkylcyclopentadiene. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is the GC (gas chromatography) diagram of the ethylcyclopentadiene reaction solution;

[0020] Figure 2 This is the GC chart of ethylcyclopentadiene after distillation and purification;

[0021] Figure 3 This is the GC chart of crude bis(ethylcyclopentadienyl)ruthenium;

[0022] Figure 4 This is the GC chart of bis(ethylcyclopentadienyl)ruthenium product;

[0023] Figure 5 This is the GC chart of the product obtained in Comparative Example 1. DETAILED DESCRIPTION

[0024] To make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0025] The present invention relates to a method for preparing a bis(alkylcyclopentadienyl) metal complex represented by formula (I).

[0026] M(RCp)2 (I)

[0027] In formula (I), M is a metal, specifically ruthenium, manganese, cobalt, preferably ruthenium. R is C 1-4 Cp is a cyclopentadienyl group. In a preferred embodiment, the method of the present invention is used to synthesize bis(ethylcyclopentadienyl)ruthenium, and the structural formula is as follows:

[0028]

[0029] In a specific embodiment, the present invention prepares ethylcyclopentadiene, and the reaction solution of the prepared ethylcyclopentadiene is subjected to vacuum distillation and purification, the distillation pressure is less than 15kPa, and the ethylcyclopentadiene raw material with a purity of more than 99% is obtained; o Below 5°C, dissolve the ethylcyclopentadiene raw material and react with zinc powder and ruthenium chloride to obtain bis(ethylcyclopentadienyl)ruthenium. Ethylcyclopentadiene can be prepared by known methods, specifically by reacting sodium cyclopentadienyl with ethyl bromide. Sodium cyclopentadienyl is dissolved in a solvent and ethyl bromide is added to react. The reaction temperature is controlled to be less than 5°C. o C.

[0030] In general, there is more impurity in the reaction solution of synthetic ethylcyclopentadiene, as raw materials such as unreacted complete cyclopentadiene, monobromethane and a small amount of solvent, also there is the dimer of cyclopentadiene dimer, product and the polymer of cyclopentadiene and ethylcyclopentadiene two by two polymerization etc., conventional rectification and separation method temperature is higher, easily makes the product ethylcyclopentadiene polymerization, causes by product to increase, and yield reduces.The present embodiment is by rectification under reduced pressure and purifies alkylcyclopentadiene, and temperature is lower in the rectifying process, can reduce the generation of polymerization in the purification process.

[0031] In a specific embodiment, the temperature of the distillation tower bottom is 25-45 ° C, and the top temperature is 17-31 ° C, preferably liquid nitrogen refrigeration. The tower bottom is stirred to increase mixing. During the distillation process, in the first stage, the pressure in the tower is reduced from 15kPa to 5kPa to remove a small amount of light components. The light components are generally ethyl bromide, cyclopentadiene and solvent tetrahydrofuran. After the light components are basically removed, the second stage begins, and the pressure in the tower is gradually reduced from 5kPa to 1kPa to produce the product ethylcyclopentadiene.

[0032] In a preferred embodiment, a polymerization inhibitor is added to the reaction solution of ethylcyclopentadiene to further inhibit the polymerization of ethylcyclopentadiene. The polymerization inhibitor can be a conventional molecular polymerization inhibitor, such as hydroquinone, p-benzoquinone, phenothiazine, β-phenylnaphthylamine, p-tert-butylcatechol, methylene blue, cuprous chloride, ferric chloride, etc. The content of the polymerization inhibitor is preferably in the range of 0.1 wt% to 1 wt%.

[0033] In a preferred embodiment, the addition of a diluent to the ethylcyclopentadiene reaction solution or the feed to the distillation column midsection can also reduce the polymerization of ethylcyclopentadiene. The diluent can be a high-boiling point solvent such as diphenyl ether or white oil. The diluent content ranges from 50 wt% to 80 wt%.

[0034] Example 1.1 Synthesis of ethylcyclopentadiene

[0035] Dissolve 20 g of sodium cyclopentadiene in tetrahydrofuran (THF) to obtain a 1 M sodium cyclopentadiene solution. Lower the system temperature to 0. o C, 33 g of bromoethane was added dropwise to the solution. The temperature was controlled not to exceed 5°C during the process. The reaction was continued for 2 h after the addition and then terminated. The solvent was removed under reduced pressure to obtain 22.3 g of crude ethylcyclopentadiene with a purity of 77.35 wt%.

[0036] Figure 1 This is a chromatogram of the reaction liquid for synthesizing ethylcyclopentadiene. Impurities include unreacted cyclopentadiene, ethyl bromide and other raw materials, a small amount of solvent, cyclopentadiene dimer, product dimer, and polymers of cyclopentadiene and ethylcyclopentadiene. Therefore, distillation is required to obtain high-purity ethylcyclopentadiene.

[0037] Example 1.2 Distillation Separation of Ethylcyclopentadiene

[0038] The crude ethylcyclopentadiene from Example 1.1 was mixed with diphenyl ether in a volume ratio of 1:2. 0.2 wt% p-benzoquinone (polymerization inhibitor) was added to the bottom of the column. The refrigeration system was activated, vacuum was established, and the bottom of the column was heated to maintain heat. The ethylcyclopentadiene and diphenyl ether mixture was then added to the bottom of the distillation column. A peristaltic pump was then used to feed a diphenyl ether solution containing 0.2 wt% p-benzoquinone (polymerization inhibitor) into the middle section of the column at a flow rate of 5 mL / min.

[0039] In the first vacuum stage, the pressure dropped from 15kPa to 5kPa, the bottom temperature was 35°C, the gas phase temperature was 17°C~19°C, and the fractions were quickly extracted and divided into ethyl bromide, cyclopentadiene and solvent tetrahydrofuran.

[0040] In the second stage of vacuum, the pressure drops from 5kPa to 1kPa, the temperature of the tower bottom is 35℃, and the temperature of the gas phase is 25℃~31℃.

[0041] Quickly extract the fraction, which is mainly composed of the product ethylcyclopentadiene, and maintain this condition until no more fraction is extracted.

[0042] Through the above vacuum first and second stage operations, 15.2 g of ethylcyclopentadiene was obtained with a yield of 88.2% and a product purity of 99.5 wt%. Figure 2 As shown, major impurities such as dimers have been essentially removed.

[0043] Example 1.3 Synthesis of bis(ethylcyclopentadienyl)ruthenium

[0044] 15.2 g of the purified ethylcyclopentadiene in Example 1.2 was dissolved in 145 g of ethanol and cooled to -20°C. 27.7 g of zinc powder was added to prepare solution A for later use. 14 g of ruthenium trichloride was dissolved in 145 g of ethanol, filtered, and added dropwise to solution A. The temperature during the addition process was controlled not to exceed -18°C. After the addition was completed, the reaction was continued for 5 h to terminate the reaction.

[0045] The reaction solution was desolvated under reduced pressure, and 100 ml of n-hexane was added for stirring and extraction. The upper layer was separated and desolvated under reduced pressure to obtain 18.4 g of crude product. The crude product chromatogram is shown in FIG. Figure 3 shown.

[0046] The crude product was distilled at a heating temperature of 140°C to 160°C, a vacuum of less than 100 Pa, and a gas phase temperature of 100°C to obtain 15.36 g of bis(ethylcyclopentadienyl)ruthenium with a purity of 99.9 wt% and a yield of 86.1%. The product chromatogram is shown in Figure 1. Figure 4 shown.

[0047] Example 2

[0048] According to the preparation process of Examples 1.1, 1.2 and 1.3, the bromoethane in Example 1.1 was replaced with iodoethane, and the p-benzoquinone in Example 1.2 was replaced with 0.3 wt% of hydroquinone. The remaining operations were the same as those of Examples 1.1, 1.2 and 1.3.

[0049] 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 product bis(ethylcyclopentadienyl)ruthenium was obtained with a content of 99.9% and a yield of 92.3%.

[0050] Example 3

[0051] According to the preparation process 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 of Examples 1.1, 1.2 and 1.3.

[0052] 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 product bis(ethylcyclopentadienyl)ruthenium was obtained, with a content of 99.9% and a yield of 89.2%.

[0053] Example 4

[0054] According to the preparation process 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 diluent diphenyl ether, and the remaining operations were exactly the same as in Example 1.

[0055] 4.1 Obtain 22.3 g of crude ethylcyclopentadiene with a purity of 77.35 wt% (same as in Example 1.1).

[0056] 4.2 After distillation, 14.8 g of ethylcyclopentadiene was obtained with a purity of 99.2 wt% and a yield of 86.1%.

[0057] 4.3 Synthesis of 14.9 g of bis(ethylcyclopentadienyl)ruthenium with a purity of 99.9 wt% and a yield of 83.5%.

[0058] Comparative Example 1 Synthesis of bis(ethylcyclopentadienyl)ruthenium

[0059] 15.2 g of the crude ethylcyclopentadiene obtained in Example 1.1 was dissolved in 145 g of ethanol and cooled to -20°C. 27.7 g of zinc powder was added to prepare solution A for later use. 14 g of ruthenium trichloride was dissolved in 145 g of ethanol, filtered, and added dropwise to solution A. The temperature during the addition process was controlled not to exceed -18°C. After the addition was completed, the reaction was continued for 5 h to terminate the reaction.

[0060] The obtained product chromatogram is as follows Figure 5 As shown, there is a by-product 1-ethylcyclopentadienylruthenium, and this by-product is difficult to remove.

[0061] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should 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 metal Ru, R is an alkyl group having 1 to 4 carbon atoms, and Cp is a cyclopentadienyl group; the preparation method comprises the following steps: preparing alkylcyclopentadiene, and performing rectification and purification on the reaction solution of the prepared alkylcyclopentadiene to obtain an alkylcyclopentadiene raw material with a purity greater than 99%; At a temperature below 0°C, the alkylcyclopentadiene raw material is dissolved and reacted with zinc powder and chloride of metal M to obtain a bis(alkylcyclopentadienyl)metal complex; The rectification and purification specifically includes the following two stages: Low-pressure distillation is used to separate the solvent from the reaction liquid. The pressure of the distillation tower is reduced from 15kPa to 5kPa, and the temperature of the tower bottom is in the range of 25-45℃. The alkylcyclopentadiene in the reaction solution is separated by vacuum distillation. The pressure of the distillation tower is reduced from 5kPa to 1kPa, and the temperature of the tower bottom is in the range of 25-45℃. Before the reaction solution of the prepared alkylcyclopentadiene is subjected to rectification and purification, a molecular polymerization inhibitor accounting for 0.1-1 wt% of the reaction solution is added to the reaction solution, wherein the molecular polymerization inhibitor is hydroquinone; 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, and the diluent is diphenyl ether.

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 alkylcyclopentadiene is to dissolve sodium cyclopentadiene in a solvent, add RBr to react, and control the reaction temperature to be less than 5°C.

4. The method according to claim 1, wherein Wherein R is ethyl.

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