Synthesis method of tetrakis (trifluorophosphine) nickel based on nickel powder

Abstract

The invention discloses a nickel powder-based tetrakis (trifluorophosphine) nickel synthesis method, and belongs to the technical field of chemistry, the synthesis method comprises the following steps: using nickel powder as a raw material to prepare nickel oxalate, heating and decomposing the nickel oxalate to obtain active nickel powder with the specific surface area of 1-10m < 2 > / g, and under the action of a catalyst, carrying out fluorophosphine reaction on the active nickel powder and phosphorus trifluoride to obtain the tetrakis (trifluorophosphine) nickel. The tetrakis (trifluorophosphine) nickel is obtained. According to the synthesis method, nickel powder is used as a raw material to prepare tetrakis (trifluorophosphine) nickel, the active nickel powder is prepared through a nickel oxalate thermal decomposition method, the reaction activity of the nickel powder is improved, no special requirement for the contrast area exists in the preparation process of the active nickel powder, the follow-up fluorophosphination reaction process cannot be affected even if the active nickel powder is placed in air, and the reaction efficiency is improved. And transfer in inert gas is not needed.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a method for synthesizing tetra(trifluorophosphine) nickel based on nickel powder. Background Technology

[0002] Nickel isotopes hold unique value in scientific research and industrial technology. High-abundance nickel-62 can be used to prepare nickel-63 through neutron irradiation and other methods. Nickel-63 releases β-particles during decay, and this energy can be converted into electrical energy for nuclear batteries. Nickel-64 with an abundance of over 99% can be used to prepare the medical radionuclide copper-64. Copper-64 is a next-generation PET imaging nuclide, characterized by clear imaging and a wide scanning time window. It can be used for the precise detection of neuroendocrine tumors, hypoxic tumor tissues, and Alzheimer's disease, providing important evidence for early diagnosis and treatment planning. Whether enriching nickel-64 or nickel-62 isotopes, the working medium used for enrichment is tetratetrafluorophosphine (Ni(PF3)4). Tetratetrafluorophosphine (Ni(PF3)4), as an important transition metal phosphorus complex, also has wide applications in catalysis, electronic materials, and organic synthesis.

[0003] Japanese patent JP306682A proposes a method for preparing nickel tetra(trifluorophosphine) by reacting nickel dicerocene or its derivatives with phosphorus trifluoride in a substitution reaction. According to the literature, nickel dicerocene and phosphorus trifluoride are mixed, heated to 60°C to 90°C, and reacted for 96 hours. The yield of this method is between 20% and 81%. This method has a low yield for producing nickel tetra(trifluorophosphine) and requires distillation purification, resulting in unreacted nickel dicerocene impurities in the product, which affect subsequent separation. Soviet patent SU1406966A1 describes adding 0.1–3 wt% sulfur powder to nickel oxalate, evacuating the system at 120°C to 150°C, introducing hydrogen gas at 300°C to 350°C to 1–2 atm, cooling the system afterward, and introducing phosphorus trifluoride at 60–70°C. The above process route allows the use of phosphorus trifluoride at lower temperatures and pressures. However, sulfur-containing impurities in this product are not easily removed during the later purification process, which can affect the concentration process of Ni isotopes and even the irradiation process.

[0004] Russian patents RU2750621C1, RU2707035C1 and RU2650955C1 all use nickel oxalate as a reactant. After being decomposed, decarbonized and dehydrated at high temperature, it reacts with phosphorus trifluoride under certain temperature and pressure.

[0005] Patent RU2650955C1 describes a process where nickel oxalate is heated to 300-350°C under a vacuum and low pressure (below 5 Pa) to dehydrate and decompose into nickel powder. The resulting nickel powder is then further reacted with phosphorus trifluoride at 100-150°C and 40-60 atmospheres for fluorination, a reaction time of 30-40 hours. The reaction conditions have a significant impact on the yield. At a nickel oxalate decomposition temperature of 350°C, a fluorination reaction temperature of 150°C, and 40 atmospheres, the yield is 98.5%, while at the same temperature, the yield is only 28%. Furthermore, this process requires continuous low-temperature and high-temperature operation within the same reactor, placing extremely high demands on the materials used.

[0006] Patent RU2750621C1 describes a process where nickel oxalate is dehydrated and decomposed through heat treatment under reduced pressure at 300-350°C. Subsequently, metallic nickel powder is reacted with phosphorus trifluoride at 100-150°C and 8-10 atmospheres for 10-12 hours. The nickel oxalate is heat-treated by grinding in a vacuum ball mill with quartz wool. Approximately 1 kg of nickel oxalate requires heat treatment at 300-350°C and 160-180 rpm for 1-3 hours, with a yield of up to 95% according to examples. The advantage of this patent is the low pressure of the phosphonation reaction. The disadvantages are that the obtained active nickel powder requires the injection of inert gas to transfer within the vacuum ball mill, which must operate at high temperatures and be able to accommodate inert gas. This places high demands on the equipment structure and materials, making it difficult to obtain, and the reaction time remains long.

[0007] Patent RU2707035C1 increases the yield of nickel tetrafluoro(trifluorophosphine) and reduces the duration of the decomposition process. The nickel oxalate decomposition and fluorophosphineation reactions are carried out in separate devices. The nickel oxalate decomposition reaction is conducted under an inert atmosphere. During the decomposition process, it is particularly emphasized that the nickel oxalate must be deeply dehydrated, and the specific surface area of ​​the active nickel powder must be at least 60 m². 2 For nickel powder with a yield of 98.2% to 99.8%, the fluorophosphineation reaction is carried out at a pressure of 8.1–14.5 MPa and a temperature of 100–150 °C. This reduces the reaction time to 3–10 hours. While the reaction time is shortened, it places extremely high demands on the removal of water vapor during the preparation of active nickel powder. It is emphasized that if the crystal water and charged water of nickel oxalate are not completely removed, the specific surface area of ​​the nickel powder will be less than 10 m². 2 Below a certain value (g), the yield of subsequent reactions will decrease significantly, which places very high demands on the operating conditions of the decomposition process. Furthermore, the transfer of active nickel powder must be carried out under an inert atmosphere, which is not feasible. In addition, the reaction process involves excessively high pressure.

[0008] As can be seen from the above, traditional synthesis methods rely on the fluorophosphine reaction of highly active nickel powder and PF3 under high temperature and high pressure conditions, which has problems such as high energy consumption, stringent equipment requirements, and slow reaction rates. In addition, the weak coordination ability of PF3 means that the reaction requires extreme conditions, which limits its industrial application.

[0009] In the prior art, there is no report on optimizing the kinetics of this reaction by adding a catalyst system. Therefore, the efficient, low-cost, and mild-condition synthesis method proposed in this invention is of great value. Summary of the Invention

[0010] The purpose of this invention is to address the technical deficiencies in the prior art by providing a method for synthesizing tetra(trifluorophosphine) nickel based on nickel powder.

[0011] The technical solution adopted to achieve the purpose of this invention is: A method for synthesizing tetra(trifluorophosphine) nickel based on nickel powder involves preparing nickel oxalate from nickel powder, and then decomposing the nickel oxalate by heating to obtain nickel with a specific surface area of ​​1-10 m². 2 / g of active nickel powder, under the action of a catalyst, undergoes a fluorophosphine reaction with phosphorus trifluoride to obtain tetra(trifluorophosphine)nickel.

[0012] In the above technical solution, the synthesis method includes the following steps: Step 1, Preparation of nickel oxalate from nickel powder: Nickel powder is oxidized with nitric acid solution to generate nickel nitrate solution. Oxalic acid solution is added to nickel nitrate solution to carry out precipitation reaction to obtain nickel oxalate suspension. Then, after depressurization, filtration and drying, nickel oxalate (nickel oxalate dihydrate) is obtained. Step 2, Thermal decomposition of nickel oxalate: Under an inert atmosphere, the nickel oxalate obtained in Step 1 is thermally decomposed to obtain a specific surface area of ​​1~10 m². 2 / g active nickel powder; Step 3, fluorophosphine reaction: Using a halogenated compound as a catalyst, the active nickel powder obtained in step 2 is reacted with excess phosphorus trifluoride (gas) to produce tetra(trifluorophosphine) nickel.

[0013] In the above technical solution, in step 1, the mass ratio of nickel powder to nitric acid solution is 1:6.5 to 1:20.0, and the mass concentration of nitric acid solution is 20% to 40%.

[0014] In the above technical solution, in step 1, the precipitation reaction time is 1 to 4 hours, the precipitation reaction temperature is 30 to 80°C, and the mass of the oxalic acid solution is 3.5 to 20.0 times the mass of the nickel powder.

[0015] In the above technical solution, the drying temperature in step 1 is 80~120℃.

[0016] In the above technical solution, step 2 specifically includes the following steps: Step 2.1: Under an inert atmosphere, place the nickel oxalate obtained in Step 1 in a tube furnace and heat it at a heating rate of 1~10℃ / min to 240~260℃ and hold it for more than 1 hour, preferably 1~3 hours, to remove the water of crystallization of nickel oxalate and obtain anhydrous nickel oxalate. Then, continue heating at a heating rate of 1~10℃ / min to 360~380℃ and hold it for 1~3 hours to completely decompose the anhydrous nickel oxalate. Stop heating to obtain active nickel powder. Step 2.2: In an inert gas atmosphere, cool the tube furnace to room temperature and remove the active nickel powder obtained in step 2.1 for later use.

[0017] In the above technical solution, in step 3, the halogenated compound is aluminum trichloride, boron halide, hydrogen chloride, carbon tetrachloride or hydrogen fluoride, and the mass of the halogenated compound is 0.05% to 5% of the mass of phosphorus trifluoride.

[0018] In the above technical solution, step 3 specifically includes the following steps: Step 3.1: In the reactor, add the active nickel powder obtained in step 2, evacuate the vacuum, add the phosphorus trifluoride mixture and start stirring. Heat the temperature to 50~70℃ and increase the pressure to above 4MPa to initiate the phosphonation reaction. The reaction temperature continues to rise and the reaction pressure decreases. After 1~3 hours, the reaction temperature begins to decrease and the reaction stops. Cool the reactor temperature to -100~-70℃. Step 3.2: Collect the excess unreacted phosphorus trifluoride from the reactor in step 3.1 for reuse. Then, thaw the reactor and heat it. When the temperature reaches above -15°C, collect the tetra(trifluorophosphine) nickel obtained from the reaction from the reactor.

[0019] In the above technical solution, in step 3.1, the phosphorus trifluoride mixture is a mixture of phosphorus trifluoride with a purity of 99% or higher and a halogenated compound, or the phosphorus trifluoride mixture is phosphorus trifluoride containing hydrogen fluoride and hydrogen chloride.

[0020] In the above technical solution, in step 3.1, if the halogenated compound is a gas, the halogenated compound and phosphorus trifluoride are first mixed evenly or the halogenated compound and phosphorus trifluoride are added to the reaction vessel in sequence. If the halogenated compound is a solid, the halogenated compound and phosphorus trifluoride are added to the reaction vessel in sequence.

[0021] In the above technical solution, during step 3.2, the temperature of the reaction vessel does not exceed 50°C during the process of collecting tetrafluorophosphine nickel from the reaction vessel.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. The synthesis method of the present invention uses nickel powder as raw material to prepare tetra(trifluorophosphine) nickel, which is prepared by the thermal decomposition of nickel oxalate to obtain active nickel powder, thereby improving the reactivity of nickel powder. Moreover, the preparation process of this active nickel powder does not have special requirements for the contrast area.

[0023] 2. In the preparation of tetra(trifluorophosphine)nickel, this invention utilizes a halogenated compound as a catalyst during the fluorophosphidization reaction. This halogenated compound possesses strong Lewis acidity and surface regulation properties, enabling it to form PF3-halogenated adducts with phosphorus trifluoride, leading to PF bond polarization and enhancing the σ-donor ability of PF3. It can also form metal-halogen bonds with the nickel surface, altering the electronic structure of nickel and increasing the number and reactivity of its coordination active sites. The addition of the catalyst significantly reduces the activation energy required for PF3 coordination with nickel, accelerating the reaction and allowing it to proceed under milder conditions. It also reduces the activity (specific surface area) requirements of the nickel powder, thereby increasing the reaction rate, shortening the overall reaction time, and stabilizing the reaction yield at over 98%. This method is easily industrially applicable for the preparation of tetra(trifluorophosphine)nickel.

[0024] 3. The active nickel powder prepared by this invention has a low specific surface area. The active nickel powder with a low specific surface area is very stable in air and has no risk of combustion or loss of activity. It does not need to be transferred in an inert gas and has no special requirements for storage, which is conducive to batch production and large-scale scale-up. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the active nickel powder prepared according to this invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] Example 1 Step 1, Preparation of Nickel Oxalate from Nickel Powder: 10 kg of 20% nitric acid solution and 500 g of nickel powder were added sequentially to a reaction vessel. Stirring was started, and the mixture was heated to 60°C for oxidation. Once the nickel powder was completely dissolved, a nickel nitrate solution was obtained. 10 kg of 20% oxalic acid solution was then added dropwise to the nickel nitrate solution at a rate of 60 ml / min. After the addition was complete, a precipitation reaction was carried out for 1 hour at a temperature of 30-40°C, resulting in a suspension of nickel oxalate. This suspension was then filtered under reduced pressure and dried at 80°C to obtain 1544.6 g of nickel oxalate dihydrate. The specific reaction process is as follows: 3Ni+ 8HNO3= 3Ni(NO3)2+ 2NO↑+4 H2O Ni + 2HNO3 = Ni(NO3)2 + H2↑ Ni(NO3)2+ H2C2O4+ 2H2O = NiC2O4•2H2O↓+ 2HNO3 Step 2, Thermal decomposition of nickel oxalate: Weigh 369g of nickel oxalate dihydrate and place it in a glass boat. Place the boat in the heating zone of a tube furnace (multiple glass boats are placed depending on the furnace size). Introduce argon gas at a flow rate of 300ml / min. Set the heating program and heat the furnace at a rate of 1℃ / min until it reaches 250℃. Hold for 1 hour to remove the water of crystallization from the nickel oxalate. Continue heating at a rate of 1℃ / min until it reaches 360℃ and holds for 1 hour to completely decompose the anhydrous nickel oxalate. Stop heating and continue introducing argon gas at the same flow rate. After cooling the furnace to room temperature, remove 118.5g of active nickel powder, seal and store for later use. The sealing and storage process does not require an inert atmosphere. The specific reaction equation is as follows: NiC2O4•2H2O= Ni+2CO2↑+ 2H2O↑ The obtained active nickel powder was characterized by XRD as nickel powder, with a specific surface area of ​​4.6 m². 2 / g.

[0028] Step 3, Fluorophosphine reaction: 42g of the active nickel powder obtained in Step 2 is added to a 2L pressure reactor, and the reactor is evacuated to 100°C. Below Pa, 0.15g of boron trifluoride was added through a pipeline, and then 300g of phosphorus trifluoride was added to the reactor through a pipeline at room temperature. The mixture was stirred at 200r / min and heated to 50℃ using an electric heating mantle. At this point, the phosphorus trifluoride gas in the reactor increased the reactor pressure to about 4.5MPa, rapidly initiating the fluorophosphine reaction. The reactor pressure dropped to 3MPa within 1 hour. After continuing the reaction for 1 hour, the pressure dropped to 1MPa. During this period, the reaction temperature reached a maximum of 170℃ and then remained relatively constant. The reaction continued until the reaction pressure remained relatively constant, indicating that the reaction was complete. The reactor was then cooled to -100~-70℃ using a coolant. At this point, the generated tetra(trifluorophosphine)nickel (Ni(PF3)4) was solid, and the phosphorus trifluoride was gaseous. The reactor outlet was connected to a phosphorus trifluoride gas receiving cylinder, and excess unreacted phosphorus trifluoride gas was frozen into the receiving cylinder using liquid nitrogen. After the phosphorus trifluoride was collected, the reactor was thawed and heated. When the temperature reached above -15°C, the reactor outlet was connected to the nickel tetra(trifluorophosphine) receiving gas cylinder. The reactor temperature was controlled to not exceed 50°C. The nickel tetra(trifluorophosphine) was frozen into the receiving gas cylinder using liquid nitrogen in the gas phase. When there was no pressure in the reactor, the collection of nickel tetra(trifluorophosphine) was stopped. 290g of nickel tetra(trifluorophosphine) (liquid at room temperature) was obtained by weighing, and the reactor outlet was closed. The yield was 98.2%, and the purity of the collected nickel tetra(trifluorophosphine) was 99.32% as characterized by gas chromatography.

[0029] Example 2 Step 1, Preparation of nickel oxalate from nickel powder: 4550g of 40% nitric acid solution and 700g of nickel powder were added sequentially to a reaction vessel. Stirring was started, and the mixture was heated to 50℃ for oxidation. Once the nickel powder was completely dissolved, a nickel nitrate solution was obtained. 2450g of 40% oxalic acid solution was then added dropwise to the nickel nitrate solution at a rate of 20ml / min. After the addition was complete, a precipitation reaction was carried out for 4 hours at a temperature of 50-80℃, resulting in a suspension of nickel oxalate. This suspension was then subjected to reduced pressure, filtered, and separated to obtain solid nickel oxalate, which was dried at 120℃ to obtain 2164.6g of nickel oxalate dihydrate.

[0030] Step 2, Thermal decomposition of nickel oxalate: Weigh 351g of nickel oxalate dihydrate and place it in a glass boat. Place the boat in the heating zone of a tube furnace (multiple glass boats are placed depending on the furnace size). Infuse argon gas at a flow rate of 800ml / min. Set the heating program and heat the furnace at a rate of 5℃ / min until it reaches 260℃. Hold for 3 hours to remove the water of crystallization from the nickel oxalate. Then, continue heating at a rate of 5℃ / min until it reaches 370℃ and holds for 2 hours to completely decompose the anhydrous nickel oxalate. Stop heating, continue purging with argon gas, and cool the furnace to room temperature. Remove 112.6g of active nickel powder, seal and store for later use. Sealing and storage do not require an inert atmosphere. The specific surface area of ​​the nickel powder is measured to be 5.6m². 2 / g.

[0031] Step 3, Fluorophosphine reaction: 50g of the active nickel powder obtained in Step 2 is added to a 2L pressure reactor. The reactor is evacuated to below 100Pa. 25g of hydrogen fluoride is added through a pipeline. At room temperature, 500g of phosphorus trifluoride is added to the reactor through a pipeline. The mixture is stirred at 200r / min. The reactor is heated to 50℃ using an electric heating mantle. At this point, the phosphorus trifluoride gas in the reactor raises the reactor pressure to about 7.5MPa, rapidly initiating the fluorophosphine reaction. The reactor pressure drops to 3MPa after 1 hour, indicating that the reaction is basically complete. During this period, the reaction temperature reaches a maximum of 200℃ and then slowly decreases. The reactor is cooled to -100~-70℃ using a coolant. At this point, the reaction produces tetra(trifluorophosphine)nickel (Ni(PF3)4) as a solid and phosphorus trifluoride as a gas. The reactor outlet is connected to a phosphorus trifluoride gas receiving cylinder. Excess unreacted phosphorus trifluoride gas is frozen into the receiving cylinder using liquid nitrogen. After the phosphorus trifluoride was collected, the reactor was thawed and heated. When the temperature reached above -15°C, the reactor outlet was connected to the nickel tetra(trifluorophosphine) receiving gas cylinder. The reactor temperature was controlled to not exceed 50°C. The nickel tetra(trifluorophosphine) was frozen into the receiving gas cylinder using liquid nitrogen in the gas phase. When there was no pressure rise in the reactor, the collection of nickel tetra(trifluorophosphine) was stopped. After weighing, 345g of nickel tetra(trifluorophosphine) (liquid) was obtained, and 150g of phosphorus trifluoride was recovered, resulting in a preparation yield of 98.6%. The purity of the collected nickel tetra(trifluorophosphine) was 99.92% as characterized by gas chromatography.

[0032] Comparative Example 1 Step 1, Preparation of nickel oxalate from nickel powder: 4550g of 40% nitric acid solution and 700g of nickel powder were added sequentially to a reaction vessel. Stirring was started, and the mixture was heated to 50℃ for oxidation. Once the nickel powder was completely dissolved, a nickel nitrate solution was obtained. 2450g of 40% oxalic acid solution was then added dropwise to the nickel nitrate solution at a rate of 20ml / min. After the addition was complete, a precipitation reaction was carried out for 4 hours at a temperature of 50-80℃, resulting in a suspension of nickel oxalate. This suspension was then subjected to reduced pressure, filtered, and separated to obtain solid nickel oxalate, which was dried at 120℃ to obtain 2164.6g of nickel oxalate dihydrate.

[0033] Step 2, Decomposition of Nickel Oxalate by Heating: Weigh 351g of nickel oxalate dihydrate and place it in a glass boat. Place the boat in the heating zone of a tube furnace and introduce argon gas at a flow rate of 800ml / min. Set the heating program and heat the tube furnace at a heating rate of 5℃ / min. Heat to 260℃ and hold for 3 hours to remove the water of crystallization of nickel oxalate. Then, continue heating at a heating rate of 5℃ / min to 370℃ and hold for 2 hours to completely decompose the anhydrous nickel oxalate. Stop heating, continue introducing argon gas, and cool the tube furnace to room temperature. Take out 112.6g of active nickel powder, seal it, and store it for later use. The sealing and storage process does not require operation under an inert atmosphere.

[0034] Step 3, Phosphonation reaction: 50g of the active nickel powder obtained in Step 2 was added to a 2L pressure reactor. The reactor was evacuated to below 100Pa. At room temperature, 500g of phosphorus trifluoride was added to the reactor via a pipeline. The mixture was stirred at 200r / min. The reactor was heated to 50℃ using an electric heating mantle. At this point, the phosphorus trifluoride gas inside the reactor increased the pressure to approximately 7.5MPa. The reactor was then heated to 150℃ at a rate of 3℃ / min, reaching a pressure of 10MPa. The reactor was then kept at this temperature. Within 12 hours, the pressure in the reactor did not decrease, indicating that no surface reaction had occurred. The reactor was cooled to -100~-70℃ using a coolant. The reactor outlet was connected to a phosphorus trifluoride gas receiving cylinder. Unreacted phosphorus trifluoride gas was frozen into the receiving cylinder using liquid nitrogen, yielding 500g of phosphorus trifluoride. This again demonstrates that the reaction was not initiated. After opening the reactor lid, the recovered nickel powder weighed 50g, indicating that the yield of tetra(trifluorophosphine) nickel was 0%.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the synthesis of tetra(trifluorophosphine)nickel based on nickel powder, characterized in that, Nickel oxalate is prepared by using nickel powder as raw material, and the specific surface area of active nickel powder obtained by heating and decomposing the nickel oxalate is 1-10 m 2 / g. Under the action of a catalyst, the active nickel powder and phosphorus trifluoride undergo fluorophosphination reaction to obtain tetra(trifluorophosphine)nickel.

2. The method of synthesis of claim 1, wherein, It comprises the following steps: Step 1, preparation of nickel powder: the nickel powder is oxidized with nitric acid solution to form a nickel nitrate solution, and then oxalic acid solution is added to the nickel nitrate solution to generate a nickel oxalate suspension, which is then dried under reduced pressure to obtain nickel oxalate; Step 2, heating decomposition of nickel oxalate: the nickel oxalate obtained in Step 1 is subjected to heating decomposition under an inert atmosphere to obtain active nickel powder having a specific surface area of 1 to 10 m 2 / g. Step 3, fluorophosphination reaction: the active nickel powder obtained in step 2 is fluorophosphinated with excess phosphorus trifluoride in the presence of a halogenated compound to obtain tetra(trifluorophosphine)nickel.

3. The method of synthesis of claim 2, wherein, In step 1, the mass ratio of the nickel powder to the nitric acid solution is 1:6.5-1:20.0, and the mass concentration of the nitric acid solution is 20%-40%.

4. The method of synthesis of claim 2, wherein, In step 1, the precipitation reaction is carried out at a temperature of 30-80℃ for 1-4 hours, and the mass of the oxalic acid solution is 3.5-20.0 times the mass of the nickel powder; the drying temperature is 80-120℃.

5. The method of synthesis of claim 2, wherein, Step 2 specifically comprises the following steps: Step 2.1, under an inert atmosphere, the nickel oxalate obtained in step 1 is heated in a tube furnace at a heating rate of 1-10℃ / min to 240-260℃ and kept for 1 hour or more, preferably 1-3 hours, to remove the crystal water of the nickel oxalate and obtain anhydrous nickel oxalate, which is then heated at a heating rate of 1-10℃ / min to 360-380℃ and kept for 1-3 hours to completely decompose the anhydrous nickel oxalate, and the heating is stopped to obtain the active nickel powder; Step 2.2, the tube furnace is cooled to room temperature in an inert gas atmosphere, and the active nickel powder obtained in step 2.1 is taken out for use.

6. The method of synthesis of claim 2, wherein, In step 3, the halogenated compound is aluminum chloride, boron halide, hydrogen chloride, carbon tetrachloride or hydrogen fluoride, and the mass of the halogenated compound is 0.05%-5% of the mass of the phosphorus trifluoride.

7. The method of synthesis of claim 2, wherein, Step 3 specifically comprises the following steps: Step 3.1, in a reaction kettle, the active nickel powder obtained in step 2 is put into the reaction kettle, vacuum is applied, and then the phosphorus trifluoride mixture is added and stirred, the temperature is heated to 50-70℃, the pressure is increased to 4 MPa or more, the fluorophosphination reaction is initiated, the reaction temperature continues to rise, the reaction pressure drops, and after 1-3 hours, the reaction temperature begins to drop, the reaction stops, and the temperature of the reaction kettle is cooled to -100--70℃; Step 3.2, the excess unreacted phosphorus trifluoride in step 3.1 is collected from the reaction kettle for reuse, and then the reaction kettle is thawed and warmed up, and when the temperature reaches -15℃ or more, the tetra(trifluorophosphine)nickel obtained by the reaction is collected from the reaction kettle.

8. The method of synthesis of claim 7, wherein, In step 3.1, the phosphorus trifluoride mixture is a mixture of phosphorus trifluoride with a purity of 99% and a halogenated compound, or the phosphorus trifluoride mixture contains hydrogen fluoride and hydrogen chloride.

9. The method of synthesis of claim 7, wherein, In step 3.1, if the halogenated compound is a gas, the halogenated compound and the phosphorus trifluoride are mixed uniformly or added to the reaction kettle in sequence, and if the halogenated compound is a solid, the halogenated compound and the phosphorus trifluoride are added to the reaction kettle in sequence.

10. The method of synthesis of claim 7, wherein, In step 3.2, during the collection of the tetra(trifluorophosphine)nickel from the reaction kettle, the temperature of the reaction kettle does not exceed 50℃.

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