Process for the photocatalytic chlorine-free synthesis of tetra(dimethylamino)tin

Abstract

The application discloses a method for photocatalytic chlorine-free synthesis of tetra (dimethylamino) tin, which comprises the following steps: reacting tetraalkyl tin and dimethylamine under the joint action of an alkyl lithium initiator and ultraviolet light; and purifying the reaction solution to obtain tetra (dimethylamino) tin products. The application breaks through the end substitution steric hindrance bottleneck by exciting the Sn-C bond of tetraalkyl tin to generate sigma to sigma star transition, effectively reducing the transition state energy barrier of the substitution reaction, and initiating trace active radicals to assist and accelerate the substitution process, ensuring the continuous and efficient progress of the reaction. The reaction rate and stability are significantly improved by using the synergistic effect of chemical energy and light energy. The reaction avoids the introduction of chlorine impurities from the source, does not need to add transition metal catalysts, and does not have additional heavy metal impurities, thereby ensuring the product purity from the process end.

Description

Technical Field

[0001] This application belongs to the field of organotin compound synthesis technology, specifically relating to a photocatalytic method for the chlorine-free synthesis of tetra(dimethylamino)tin. Background Technology

[0002] Tetra(dimethylamino)tin (CAS No. 1066-77-9) is a core tin-based organometallic precursor in the field of perovskite solar cell manufacturing. It is mainly used in the preparation of electron transport layers in perovskite solar cells. Its purity and impurity control level directly determine the photoelectric conversion efficiency, stability and lifespan of perovskite solar cells.

[0003] Currently, the synthesis processes of tetra(dimethylamino)tin are mainly divided into two categories: chlorine-containing processes and chlorine-free processes. The traditional chlorine-containing process uses tin tetrachloride as the tin source. First, stoichiometric dimethylaminolithium is generated by reacting n-butyllithium with dimethylamine, and then undergoes a nucleophilic substitution reaction with tin tetrachloride to obtain the target product. The byproducts are solid lithium chloride and butane. This process has several inherent defects: First, the raw material cost is high, requiring 4 equivalents of n-butyllithium for the reaction, resulting in a large amount of reagent consumption; second, chlorine impurities are difficult to eliminate, and the product is prone to carrying lithium chloride and chlorine-containing intermediates; third, the post-processing is complex, with cumbersome separation procedures for solid lithium chloride byproducts, adding additional purification steps and product loss; fourth, the side reaction is difficult to control, and the concentrated exothermic reaction can easily cause local overheating, promoting the disproportionation of Sn(IV) to generate low-valence Sn(II) impurities. Low-temperature dropwise addition can only suppress this side reaction, but cannot completely eliminate it, ultimately affecting the product yield and purity.

[0004] Chlorine-free processes can avoid the introduction of chlorine impurities at the source, eliminating the need for additional impurity removal processes such as lithium chloride salt slag separation. This aligns with the high purity requirements of downstream perovskite batteries for precursor materials, making it a mainstream research and development direction in the industry. Existing chlorine-free synthesis processes for tetra(dimethylamino)tin mostly use transition metal salts as catalysts. Due to the large steric hindrance of the fourth-position alkyl substitution, the intrinsic activation energy of this type of ammonolysis reaction is high. However, existing transition metal salt catalysts have limited activation capacity for Sn-C bonds, failing to effectively lower the transition state energy barrier of nucleophilic substitution, resulting in slow reaction start-up and a low overall rate. Furthermore, these catalytic systems are mostly heterogeneous, and the reaction effect is significantly affected by the uniformity of catalyst dispersion, easily leading to uneven local reaction rates and further incomplete conversion of raw materials. In addition, transition metal catalysts themselves introduce additional metal impurities into the system. These impurities have similar physicochemical properties to the products and are difficult to completely separate using conventional distillation methods, leading to decreased product purity and failing to meet the stringent requirements of perovskite precursors. This also increases the difficulty of product purification and production costs. Summary of the Invention

[0005] The purpose of this application is to provide a photocatalytic chlorine-free synthesis method for tetra(dimethylamino)tin, in order to solve the problems existing in the current tetra(dimethylamino)tin synthesis process.

[0006] To achieve the above objectives, this application provides a method for the photocatalytic chlorine-free synthesis of tetra(dimethylamino)tin, comprising:

[0007] Tetraalkyltin and dimethylamine react under the combined action of an alkyllithium initiator and ultraviolet light;

[0008] After the reaction was completed, the reaction solution was purified to obtain tetra(dimethylamino)tin product;

[0009] The wavelength of the ultraviolet light is 240~330nm.

[0010] In one or more embodiments, the tetraalkyltin is selected from at least one of tetrabutyltin, tetrapropyltin, tetrapentyltin, and tetrahexyltin.

[0011] In one or more embodiments, the reaction temperature is 0~25°C.

[0012] In one or more embodiments, the reaction time is 6 to 10 hours.

[0013] In one or more embodiments, the average effective optical power density within the reaction system is 1.0 mW / cm². 2 ~3.5mW / cm 2 .

[0014] In one or more embodiments, the alkyllithium initiator is selected from at least one of n-butyllithium and tert-butyllithium.

[0015] In one or more embodiments, the molar ratio of the alkyllithium initiator to the tetraalkyltin is (0.02~0.04):1.

[0016] In one or more embodiments, the molar ratio of the dimethylamine to the tetraalkyltin is (6~10):1.

[0017] In one or more embodiments, the step of reacting tetraalkyltin and dimethylamine under the action of an alkyllithium initiator and ultraviolet light includes:

[0018] Tetraalkyltin and an organic solvent were added to the reaction vessel under an inert atmosphere, and the mixture was stirred and cooled.

[0019] The dimethylamine is introduced into the reaction system;

[0020] The alkyllithium initiator was added to the reaction system, stirred until homogeneous, and then ultraviolet light was applied to carry out the reaction.

[0021] In one or more embodiments, the organic solvent is n-hexane.

[0022] In one or more embodiments, the ultraviolet light is applied by an ultraviolet light source arranged in a ring on the inner wall of the reaction vessel, or by an immersion ultraviolet light source immersed in the reaction system.

[0023] In one or more embodiments, after the reaction is completed, the step of purifying the reaction solution to obtain the tetra(dimethylamino)tin product includes:

[0024] After the reaction is complete, the gaseous byproducts are discharged, and then the reaction solution is purified by distillation to obtain tetra(dimethylamino)tin product.

[0025] In one or more embodiments, the distillation purification includes: first removing the organic solvent and excess dimethylamine by atmospheric distillation, and then collecting the target fraction by vacuum distillation.

[0026] The advantages of this application, which differ from existing technologies, are:

[0027] This application utilizes ultraviolet light to excite the Sn-C bond of tetraalkyltin to undergo a σ→σ* transition, effectively reducing the transition state energy barrier of the substitution reaction and initiating trace amounts of active free radicals to accelerate the substitution process. This overcomes the steric hindrance bottleneck of terminal substitution, ensuring the continuous and efficient advancement of the reaction. By utilizing the synergistic effect of chemical and light energy, the reaction rate and stability are significantly improved. The entire reaction process avoids the introduction of chlorine impurities from the source, requires no addition of transition metal catalysts, and leaves no additional heavy metal impurities, thus ensuring product purity from the process end.

[0028] The amount of alkyl lithium initiator used in this application is only the amount required for catalysis, which is far less than the 4 equivalents of n-butyllithium used in traditional methods, thus significantly reducing the cost of core reagents. The reaction can proceed stably at room temperature, and the Sn(IV) thermal disproportionation side reaction is effectively suppressed, reducing the generation of low-valent tin impurities. At the same time, it eliminates complex processes such as cryogenic drop addition and solid-liquid separation, further reducing production energy consumption and operating costs.

[0029] The tetra(dimethylamino)tin product prepared in this application has an organic purity greater than 99% and a total metal impurity content of less than 1 ppm, reaching the 6N grade metal purity standard. The target product molar yield is greater than 90%, which is significantly better than the existing chlorine-free synthesis technology in terms of yield and purity. It can directly meet the high-purity application requirements of perovskite battery precursors. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart of one embodiment of the photocatalytic chlorine-free synthesis of tetra(dimethylamino)tin in this application. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0033] The traditional chlorine-containing synthesis method for tetra(dimethylamino)tin uses tin tetrachloride as the tin source. First, n-butyllithium reacts with dimethylamine to generate a stoichiometric amount of dimethylaminolithium, which then undergoes a nucleophilic substitution reaction with tin tetrachloride to obtain the target product. Byproducts include solid lithium chloride and butane. This process has several inherent drawbacks: First, the raw material cost is high, requiring 4 equivalents of n-butyllithium for the reaction, resulting in large reagent consumption; second, chlorine impurities are difficult to remove, and the product easily carries incompletely substituted intermediates and lithium chloride particles, failing to meet the stringent purity requirements for perovskite battery precursors; third, the raw material utilization rate is low, with a molar yield of only 70%–75% for the target product.

[0034] In addition, the reaction is exothermic and concentrated, which can easily lead to local overheating, causing Sn(IV) to disproportionate and generate Sn(II) low-valence tin impurities. Industrially, this side reaction is usually suppressed by low-temperature dropwise addition, but it cannot be completely eliminated, which further reduces the yield and purity of the product.

[0035] To avoid residual chlorine impurities in the product, the industry is currently researching chlorine-free synthesis processes for tetra(dimethylamino)tin. Existing chlorine-free processes attempt to use transition metal catalysts to promote the amino substitution reaction of organotin compounds such as tetrabutyltin with dimethylamine. This type of reaction suffers from high steric hindrance at the fourth alkyl substitution position and a high intrinsic activation energy. However, existing transition metal salt catalysts have limited activation capacity for Sn-C bonds and cannot effectively lower the transition state energy barrier for nucleophilic substitution, only slightly increasing the reaction rate. According to reaction kinetics, the reaction rate is negatively correlated with the activation energy; the higher the activation energy, the slower the reaction rate. Therefore, this process still suffers from long reaction cycles and incomplete raw material conversion. Furthermore, the addition of catalysts introduces additional transition metal impurities. These impurities have similar physicochemical properties to the product and are difficult to separate using conventional purification methods, leading to decreased product purity. This fails to meet the stringent requirements of perovskite precursors and further increases the difficulty of product purification and production costs.

[0036] In addition, transition metal salt catalytic systems are mostly heterogeneous systems, and the reaction effect is significantly affected by the uniformity of catalyst dispersion: excessively high local catalyst concentration will aggravate side reactions such as Sn(IV) disproportionation, while too low concentration will not play a catalytic role, resulting in fluctuations in reaction rate, which in turn causes large differences in purity and yield between batches of products, making it difficult to meet the stability requirements of large-scale production of perovskite precursors.

[0037] In particular, due to the low reaction kinetic rate, even with extended reaction time, the fourth-position substitution at the terminal steric hindrance is still difficult to complete, resulting in a high residual amount of trisubstituted intermediates, low overall conversion rate of raw materials, waste of raw materials, and further increase in production costs.

[0038] To address the technical problems of low reaction efficiency, difficulty in impurity control, and high production costs in existing processes, the applicant has developed a photocatalytic, chlorine-free method for the synthesis of tetra(dimethylamino)tin. This method effectively reduces the transition state energy barrier of the substitution reaction through the synergistic effect of UV activation and alkyl lithium initiators, overcoming the steric hindrance bottleneck of terminal alkyl substitution and significantly improving the reaction rate and process stability. The entire process avoids the introduction of chlorine impurities from the source, requires no added transition metal catalysts, and leaves no additional heavy metal impurities, ensuring product purity from the reaction pathway level and achieving efficient, stable, and clean synthesis of tetra(dimethylamino)tin.

[0039] Specifically, please refer to Figure 1 , Figure 1 This is a schematic flowchart of one embodiment of the photocatalytic chlorine-free synthesis of tetra(dimethylamino)tin in this application.

[0040] like Figure 1 As shown, the method includes:

[0041] S101, Tetraalkyltin and dimethylamine react under the combined action of an alkyllithium initiator and ultraviolet light.

[0042] In one embodiment, the alkyllithium initiator may be selected from at least one of n-butyllithium and tert-butyllithium.

[0043] In one embodiment, the molar ratio of alkyllithium initiator to tetraalkyltin can be (0.02~0.04):1.

[0044] In one embodiment, the tetraalkyltin may be selected from at least one of tetrabutyltin, tetrapropyltin, tetrapentyltin, and tetrahexyltin.

[0045] In one embodiment, the molar ratio of dimethylamine to tetraalkyltin can be (6~10):1 to ensure complete reaction of the tetraalkyltin raw material.

[0046] The theoretical stoichiometric ratio for the formation of tetra(dimethylamino)tin is 4:1 (dimethylamine: tetraalkyltin). Using excess dimethylamine can, on the one hand, shift the equilibrium of the sterically hindered substitution reaction to the forward direction, reduce the residual trisubstituted intermediate, and ensure complete conversion of the starting material; on the other hand, it can stabilize the catalytic cycle and simultaneously quench trace amounts of active free radicals in the system, inhibiting photodegradation side reactions of the product. Based on the above molar ratio range, reaction efficiency, product purity, and production economy can be balanced. When the molar ratio of dimethylamine to tetraalkyltin is lower than 6:1, complete terminal substitution cannot be guaranteed; when it is higher than 10:1, the marginal benefit of the technology diminishes, and the cost of recovering and purifying excess dimethylamine increases significantly.

[0047] In one embodiment, the wavelength of ultraviolet light can be 240~330nm. Ultraviolet light in this wavelength range can selectively activate the Sn-C bond of tetraalkyltin and lower the transition state energy barrier of the substitution reaction.

[0048] In one embodiment, the reaction temperature can be 0~25℃; the reaction can be carried out at room temperature, effectively suppressing the Sn(IV) thermal disproportionation side reaction and reducing the generation of low-valent tin impurities.

[0049] In one implementation, the reaction time can be 6 to 10 hours.

[0050] In one embodiment, the average effective optical power density within the reaction system can be 1.0 mW / cm². 2 ~3.5mW / cm 2 This is to ensure the reaction rate.

[0051] The average effective optical power density can be obtained by taking the arithmetic mean after measuring multiple points in the upper, middle, and lower layers of the reaction solution, as well as the center and near-wall positions, using an ultraviolet radiometer of the corresponding wavelength band.

[0052] Based on the above scheme, this application significantly optimizes the reaction kinetics by applying ultraviolet light to activate the reaction substrate and introducing an alkyllithium initiator, utilizing the synergistic effect of chemical and light energy. Based on the reaction phenomena and product analysis, taking n-butyllithium as the alkyllithium initiator and tetrabutyltin as the tetraalkyltin as an example, the reaction mechanism of this application is speculated as follows (this mechanism is used to help understand the technical solution of this application, and not to limit the invention).

[0053] 1. In-situ active species generation stage: In the reaction system, the strongly basic n-butyllithium reacts rapidly with dimethylamine to generate the strong nucleophile lithium dimethylamino in situ, while releasing butane. This step is the initiation process of the reaction.

[0054] 2. Photoactivation barrier reduction stage: Ultraviolet light with a wavelength of 240~330nm can selectively excite the σ→σ* transition of the Sn-C bond of tetrabutyltin, weaken the bond energy of the Sn-C bond, reduce the transition state energy barrier of the subsequent nucleophilic substitution reaction, and thus significantly increase the reaction rate; at the same time, ultraviolet light can induce homolytic cleavage of a small amount of Sn-C bond, generating a small amount of butyl radical (•Bu).

[0055] 3. Main Reaction Cycle Stage: Lithium dimethylamino, acting as a nucleophile, attacks the four-coordinate tin center, undergoing a nucleophilic substitution reaction. This transfers the dimethylamino ligand to the tin atom, simultaneously displacing butyllithium. The generated butyllithium immediately undergoes proton transfer with excess dimethylamine in the system, regenerating lithium dimethylamino, which then participates in the next round of substitution reactions. This polar nucleophilic substitution cycle is the main reaction pathway. Through stepwise substitution, all four butyl ligands of tetrabutyltin are replaced with dimethylamino groups, ultimately generating the target product, tetra(dimethylamino)tin. During this process, only a small amount of n-butyllithium is required to maintain the cycle.

[0056] 4. Free radical-assisted acceleration stage: The trace amount of butyl radical (•Bu) generated by photoinitiation can abstract hydrogen atoms from the NH bond of the dimethylamine molecule to generate dimethylamino radical (•NMe2) and butane. The dimethylamino radical can react with alkyltin intermediates to help accelerate the ligand substitution process and further improve the overall reaction rate.

[0057] Based on the above reaction mechanism, this application achieves a highly efficient reaction through the synergistic effect of light and chemical energy: ultraviolet light is responsible for activating the Sn-C bond, lowering the transition state energy barrier, and overcoming the steric hindrance bottleneck of terminal alkyl substitution; the alkyl lithium initiator is responsible for the in-situ generation of strong nucleophilic species, initiating a polar nucleophilic substitution catalytic cycle. The synergistic effect of these two factors significantly improves the reaction rate and process stability; the entire process avoids the introduction of chlorine impurities from the source, requires no addition of transition metal catalysts, and leaves no additional heavy metal impurities, ensuring product purity from the reaction pathway level.

[0058] In other embodiments, when the alkyllithium initiator is tert-butyllithium, the reaction rate can be further increased because tert-butyllithium is more basic and has a faster proton transfer rate, allowing for faster in-situ generation of lithium dimethylamino.

[0059] In other embodiments, when the tetraalkyltin is selected from tetrapropyltin, tetrapentyltin, and tetrahexyltin, its ultraviolet light response all originates from the σ→σ* transition of the Sn-C σ bond. The saturated alkyl side chain has no characteristic absorption in the wavelength range of 240~330nm, and the absorption peak is only shifted by less than 10nm through the inductive effect. Therefore, it can be effectively excited and initiate trace amounts of active free radicals. The reaction rate is slightly different only due to the different steric hindrance of the alkyl group. Those skilled in the art can ensure the complete conversion of the raw materials by conventionally fine-tuning the irradiation time.

[0060] It should be noted that under ultraviolet light in the 240–330 nm range, the Sn-N bonds of some target products, tetra(dimethylamino)tin, undergo n→σ* transitions, exhibiting a slight tendency for photodegradation and generating low-valent tin byproducts such as di(dimethylamino)tin(II). However, since the main reaction rate is much faster than the photodegradation rate of the Sn-N bonds of the product, and excess dimethylamine can play a role in free radical capture and inhibiting the disproportionation side reactions after bond cleavage, the degradation rate of the product during the reaction is extremely low.

[0061] Previous studies have shown that significant degradation of tetra(dimethylamino)tin requires prolonged and continuous ultraviolet irradiation. However, in this system, the nucleophilic substitution reaction is accelerated by the alkyllithium initiator. Combined with the condition of excess dimethylamine, by controlling the duration and intensity of irradiation, byproducts can be kept at extremely low levels. Under the reaction conditions of this application, the product degradation rate is less than 1%, with no significant impact on product purity.

[0062] Specifically, in one embodiment, the ultraviolet light source can be a 254nm wavelength low-pressure mercury lamp with a single photon energy of about 4.88eV, which can excite the σ→σ* transition of Sn-C in tetrabutyltin and simultaneously induce the homolytic cleavage of trace Sn-C bonds to generate free radicals, resulting in the fastest overall reaction rate and the highest comprehensive efficiency.

[0063] In another embodiment, the ultraviolet light source can also be a mid-wave ultraviolet light source of 310~330nm, with a single photon energy of 3.8~4.0eV. The excitation efficiency for tetrabutyltin is weaker than that of 254nm, and the reaction rate is reduced. The conversion efficiency can be compensated by increasing the light intensity and extending the reaction time. However, at this wavelength, the probability of n→σ* transition of the Sn-N bond of tetra(dimethylamino)tin is greatly reduced, the photodegradation rate is significantly slowed down, and the amount of low-valent tin impurities generated is extremely small, which is more suitable for the product requirements of high-purity electronic-grade MO source.

[0064] In addition, when the wavelength of ultraviolet light is below 240 nm, the photon energy is too high, which will cause significant photolysis of the Sn-N bond of the product, resulting in a significant decrease in product yield and purity; while when the wavelength is above 330 nm, the photon energy is insufficient and cannot effectively activate the Sn-C bond of tetraalkyltin, and the reaction rate will drop sharply.

[0065] It should be noted that the above embodiments are merely illustrative examples. In other embodiments, the wavelength, power, and reaction temperature of the ultraviolet light can be adjusted accordingly for different tetraalkyltin raw materials to ensure that the Sn-C bond can be effectively activated while avoiding significant photodegradation of the product. All of these can achieve the effects of this embodiment.

[0066] Furthermore, in one embodiment, to ensure uniform ultraviolet light coverage of the reaction system and consistent reaction rates in each region, the ultraviolet light source is arranged in a ring around the inner wall of the reaction vessel to uniformly apply ultraviolet light into the system; combined with the stirring action during the reaction process, it can ensure uniform light intensity distribution and consistent reaction rates throughout the reaction system.

[0067] In another embodiment, the ultraviolet light source can also be set up in an immersion manner, directly immersing itself in the reaction system and emitting ultraviolet light evenly in all directions; combined with the stirring effect during the reaction process, it can also ensure that the light intensity distribution is uniform throughout the reaction system and the reaction rate is consistent.

[0068] The steps of the photocatalytic reaction of this application are described in detail below.

[0069] In one embodiment, the step of reacting tetraalkyltin and dimethylamine under the action of an alkyllithium initiator and ultraviolet light may include:

[0070] Tetraalkyltin and an organic solvent were added to the reaction vessel under an inert atmosphere, and the mixture was stirred and cooled.

[0071] Dimethylamine is introduced into the reaction system;

[0072] An alkyllithium initiator was added to the reaction system, stirred until homogeneous, and then ultraviolet light was applied to carry out the reaction.

[0073] In one embodiment, the organic solvent may be n-hexane, and the volume ratio of the organic solvent to tetraalkyltin is (1~5):1.

[0074] Hexane has an ultraviolet cutoff wavelength of approximately 195 nm and almost no absorption in the 240–330 nm range. The solvent does not undergo photolysis to produce impurities, and the system has good compatibility.

[0075] S102. After the reaction is complete, the reaction solution is purified to obtain tetra(dimethylamino)tin product.

[0076] In one embodiment, after the reaction is complete, the gaseous byproducts can be discharged first, and then the reaction solution can be purified by distillation to obtain tetra(dimethylamino)tin product.

[0077] Specifically, the distillation purification can be carried out by first removing the organic solvent and excess dimethylamine by atmospheric distillation, and then collecting the target fraction by vacuum distillation.

[0078] Specifically, after the reaction is complete, the ultraviolet light source is turned off, the alkane tail gas generated in the reaction is discharged, the solvent and excess dimethylamine are removed by atmospheric distillation, and finally the high-purity target product is obtained by vacuum distillation.

[0079] Specifically, the fraction collected by vacuum distillation can be the main fraction under conditions of 53~55℃ / 0.1mmHg.

[0080] Experimental verification shows that the tetra(dimethylamino)tin product prepared by the method of this embodiment has a total metal impurity content of <1ppm, a metal purity of 6N grade, and a target product molar yield of greater than 90%, and its comprehensive performance is significantly better than that of existing chlorine-free synthesis technology.

[0081] Based on the process design of the above embodiments, this application achieves efficient, stable, and clean synthesis of tetra(dimethylamino)tin through the synergistic effect of ultraviolet light activation and alkyl lithium initiators. The product avoids the introduction of chlorine impurities from the source, has no transition metal catalyst residues, and fully meets the stringent purity requirements of perovskite battery precursors; the alkyl lithium initiator requires only a small amount of catalyst, far less than the 4 equivalents of n-butyllithium required in traditional chlorine-containing processes, and the reaction can proceed stably at room temperature, effectively suppressing the Sn(IV) thermal disproportionation side reaction, which can significantly reduce the overall production cost.

[0082] The effects of the technical solution of this application will be further described in detail below with reference to specific embodiments.

[0083] Example 1:

[0084] A photocatalytic method for the chlorine-free synthesis of tetra(dimethylamino)tin is disclosed. A 1L sealed, pressure-resistant glass reactor is used as the reactor, with a low-pressure mercury lamp (peak wavelength 254nm) as the light source. The lamp has a single-lamp input power of 40W and a 254nm ultraviolet radiation efficiency ≥30%. A high-purity quartz sleeve with a 254nm light transmittance greater than 90% is placed outside the light source, immersing it ≥250mm below the liquid surface. The average effective light power density within the reaction solution is approximately 3.0 mW / cm². The light power density is measured using a corresponding wavelength ultraviolet radiometer. Six measurement points are taken in the upper, middle, and lower layers of the reaction solution, as well as at the center and near the wall. The arithmetic mean is taken as the average effective light power density within the system. The measurement is performed in a pure solvent blank system.

[0085] The methods include:

[0086] (1) Add 280 mL of anhydrous n-hexane to the dry and deoxygenated reactor, then add 0.2 mol (59.6 g) of tetrabutyltin, start stirring, control the speed at 200 rpm, and cool the system to 10 °C by jacket cooling;

[0087] (2) Slowly pass in 1.2 mol (54.1 g) of anhydrous dimethylamine;

[0088] (3) Inject 1.6 mL of 2.5 mol / L n-butyllithium hexane solution into the system, stir and mix for 5 min, then turn on the ultraviolet light source and maintain the system temperature in the range of 10~15℃ for 6 h of continuous light irradiation reaction;

[0089] (4) After the reaction is completed, turn off the light source, discharge the butane tail gas generated in the system, transfer the reaction liquid to the distillation apparatus, first remove the n-hexane solvent and excess dimethylamine by atmospheric distillation, and then collect the main fraction under the conditions of 53~55℃ / 0.1mmHg by vacuum distillation to obtain tetra(dimethylamino)tin product with a yield of 95.1%.

[0090] ICP-MS analysis showed that the total metal impurity content in the product was <1 ppm, meeting the 6N metal purity standard. ¹H NMR analysis showed that the organic purity of the product was >99%.

[0091] Example 2:

[0092] A photocatalytic method for the chlorine-free synthesis of tetra(dimethylamino)tin is basically the same as that in Example 1, except that:

[0093] An array of ultraviolet LEDs with a main peak of 315nm was used as a light source and placed outside the reaction vessel to irradiate the reaction liquid.

[0094] The total input power of the light source is 30W. After multi-point calibration by an ultraviolet radiometer, the effective light power density at the reaction liquid surface is 2.8mW / cm². 2 The average effective light power density in the reaction solution is approximately 2.2 mW / cm².

[0095] The product yield was 96.3%. Testing showed that the total metal impurity content of the product was <1 ppm, meeting the 6N grade metal purity standard, and the organic purity was >99%.

[0096] Example 3:

[0097] A method for the photocatalytic chlorine-free synthesis of tetra(dimethylamino)tin is disclosed, which uses a 30L pressure-resistant reactor as the reactor and a low-pressure mercury lamp with a main peak of 254nm as the light source. The single lamp input power is 80W, and the 254nm ultraviolet radiation efficiency is ≥30%. A high-purity quartz sleeve with a 254nm light transmittance greater than 90% is used to cover the light source, and three sleeves are evenly arranged along the inner wall of the reactor. The immersion depth below the liquid surface is ≥280mm, and the average effective light power density in the reaction solution is about 2.5mW / cm².

[0098] The methods include:

[0099] (1) Add 21L of anhydrous n-hexane to the dry and deoxygenated reactor, then add 14mol (4172g) of tetrabutyltin, start stirring, control the speed at 150rpm, and control the jacket temperature to 6℃.

[0100] (2) Slowly introduce 84 mol (3787 g) of anhydrous dimethylamine;

[0101] (3) Inject 200 mL of 2.5 mol / L n-butyllithium hexane solution, stir for 10 min, then turn on all 3 UV lamps and maintain the system temperature at 10~20℃ for 10 h of continuous light irradiation reaction;

[0102] (4) After the reaction is completed, turn off the light source, discharge the butane tail gas generated in the system, transfer the reaction liquid to a vacuum distillation apparatus, first remove the n-hexane solvent and excess dimethylamine by atmospheric distillation, and then collect the main fraction under the conditions of 53~55℃ / 0.1mmHg to obtain tetra(dimethylamino)tin product with a yield of 94.7%.

[0103] Tests showed that the total content of metal impurities in the product was <1ppm, meeting the 6N grade metal purity standard, and the organic purity was >99%.

[0104] Comparative Example 1:

[0105] A method for synthesizing tetra(dimethylamino)tin, which is basically the same as that in Example 1, except that:

[0106] Using a low-pressure mercury lamp with a main peak of 220nm as the light source, the single lamp input power is 55W, and the 220nm ultraviolet radiation efficiency is ≥25%. The light source is fitted with a deep ultraviolet-grade synthetic quartz sleeve with a 220nm light transmittance of ≥80%, which is vertically inserted into the reaction solution and immersed to a depth of ≥250mm below the liquid surface. The average effective light power density in the reaction solution is about 3.0mW / cm².

[0107] The product yield was approximately 81%, but testing revealed that the product could not meet the 6N purity standard.

[0108] Comparative Example 2:

[0109] A method for synthesizing tetra(dimethylamino)tin, which is basically the same as that in Example 1, except that:

[0110] A low-pressure mercury lamp with a peak wavelength of 365nm was used as the light source, with a single lamp input power of 75W and a 365nm ultraviolet radiation efficiency of ≥15%. The light source was encased in a high-purity quartz sleeve with a 365nm light transmittance of ≥95%, and was vertically inserted into the reaction solution to a depth of ≥250mm below the liquid surface. The average effective light power density in the reaction solution was approximately 3.0mW / cm². The photoreaction time was extended to 12 hours.

[0111] The product yield was approximately 73%, and testing revealed that the product could not meet the 6N purity standard.

[0112] Comparative Example 3:

[0113] A method for synthesizing tetra(dimethylamino)tin, which is basically the same as that in Example 1, except that:

[0114] No ultraviolet light was applied during the reaction, and the reaction time was extended to 24 hours. The product yield was approximately 70%.

[0115] Testing revealed that the product failed to meet the 6N purity standard.

[0116] Comparative Example 4:

[0117] A method for synthesizing tetra(dimethylamino)tin, which is basically the same as that in Example 1, except that:

[0118] No n-butyllithium was added to the reaction system, and the photo-irradiation reaction time was extended to 24 hours.

[0119] The product yield was found to be less than 10%.

[0120] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0121] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for photocatalytic chlorine-free synthesis of tetra(dimethylamino)tin, characterized in that, include: Tetraalkyltin and dimethylamine react under the combined action of an alkyllithium initiator and ultraviolet light; After the reaction was completed, the reaction solution was purified to obtain tetra(dimethylamino)tin product; The wavelength of the ultraviolet light is 240~330nm.

2. The method according to claim 1, characterized in that, The tetraalkyltin is selected from at least one of tetrabutyltin, tetrapropyltin, tetrapentyltin, and tetrahexyltin.

3. The method according to claim 1, characterized in that, The reaction temperature is 0~25℃.

4. The method according to claim 3, characterized in that, The reaction time is 6-10 hours; and / or, The average effective optical power density within the reaction system is 1.0 mW / cm². 2 ~3.5mW / cm 2 .

5. The method according to claim 1, characterized in that, The alkyl lithium initiator is selected from at least one of n-butyllithium and tert-butyllithium; and / or The molar ratio of the alkyllithium initiator to the tetraalkyltin is (0.02~0.04):

1.

6. The method according to claim 1, characterized in that, The molar ratio of the dimethylamine to the tetraalkyltin is (6~10):

1.

7. The method according to claim 1, characterized in that, The step of reacting tetraalkyltin and dimethylamine under the action of an alkyllithium initiator and ultraviolet light includes: Tetraalkyltin and an organic solvent were added to the reaction vessel under an inert atmosphere, and the mixture was stirred and cooled. The dimethylamine is introduced into the reaction system; The alkyllithium initiator was added to the reaction system, stirred until homogeneous, and then subjected to ultraviolet light to carry out the reaction.

8. The method according to claim 7, characterized in that, The organic solvent is n-hexane; and / or, The ultraviolet light is applied by an ultraviolet light source arranged in a ring on the inner wall of the reaction vessel, or by an immersion ultraviolet light source immersed in the reaction system.

9. The method according to claim 7, characterized in that, After the reaction is completed, the step of purifying the reaction solution to obtain the tetra(dimethylamino)tin product includes: After the reaction is complete, the gaseous byproducts are discharged, and then the reaction solution is purified by distillation to obtain tetra(dimethylamino)tin product.

10. The method according to claim 9, characterized in that, The distillation purification process includes: first, removing the organic solvent and excess dimethylamine by atmospheric distillation, and then collecting the target fraction by vacuum distillation.

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