High-Purity Alkyltin Compounds and Method for Producing the Same

Abstract

Describe a monoalkyltin triamide compound having a purity of at least about 99 mol% and the chemical formula RSn(NMe2)3. R 1 is R A 、R B 、and R C selected from, R A is a primary alkyl group having from about 1 to 10 carbon atoms, R B is a secondary alkyl group having from about 3 to 10 carbon atoms, R C is a tertiary alkyl group having from about 3 to 10 carbon atoms, each R 2 is, independently, an alkyl group having from about 1 to 10 carbon atoms, R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) content is less than about 1 mol%. Methods for synthesizing, purifying, and storing these compounds are also provided. The monoalkyltin compounds can be used for the formation of precursors for high-resolution EUV lithography - pattern formation, which are of interest because of their high purity and minimal concentrations of dialkyltin and other tin impurities.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Application No. 63 / 348,173, filed on June 2, 2022, the disclosure of which is incorporated herein by reference.

Background Art

[0002] As semiconductor fabrication continues to advance, feature sizes have been continuously decreasing, and there is an increasing need for new processing methods. In applications such as extreme ultraviolet (EUV) lithography technology, certain organotin compounds have been shown to be useful for the deposition of tin oxide hydroxide coatings. For example, alkyltin compounds provide radiation - sensitive Sn - C bonds that can be used to pattern structures by lithography.

[0003] The materials used in microelectronics fabrication need to be extremely pure, and strict restrictions have been imposed on organic contamination (e.g., reaction by - products), metal contamination, and particulate contamination. The purity requirements are generally strict, especially for lithography applications, because chemicals can come into contact with semiconductor substrates and organic metal impurities in the compounds, such as diisopropylbis(dimethylamino)tin, 3(iPr)2Sn(NMe2)2, can affect the properties of the films formed. The exact target for purity is determined by various factors including performance metrics, but a typical minimum purity target is 3N +. Residual metals present in chemicals can be deposited on semiconductor substrates and may degrade the electrical performance of the devices being fabricated. Typical specifications for metals are less than 10 ppb for individual metals and not exceeding about 100 ppb for total metals.

[0004] The processing and performance of semiconductor materials can also be sensitive to dialkyltin contaminants. Oxotinate cluster films have low density when the film contains dialkyl groups, so dialkyltin impurities, namely R2Sn(NMe2)2 (where R is an alkyl group), serve as a source of off-gas after vapor deposition or spin-on coating processes. Proper control of dialkyltin contaminants is required for producing microelectronic products using EUV lithography. The high purity required by the monoalkyltin precursor manufacturing process poses a challenge. Generally, the synthesis of monoalkyltin triamides has hitherto utilized a lithium dimethylamide reagent that reacts with alkyltin trichloride, or subsequently, a lithium / Grignard reagent (alkylating agent) to convert stannatetraamide to the desired triamide.

[0005] When preparing primary alkyltin triamides, such as methyl and longer alkyl tin triamides, containing less than 1% dialkyltin after purification, the Kochiukov-like equilibrium reaction in Scheme (I) and the disproportionation reaction in Scheme (II) shown below during purification are two major challenges. Experiments have shown that the equilibrium reaction occurs independently of the reaction temperature up to -78 °C. In fact, lower temperatures have been found to slow down the substitution reaction that increases the risk of the equilibrium reaction.

[0006]

Chemical formula

[0007] The preparation of monoalkyltin triamide compounds can be achieved by two different known synthetic routes. When the alkyl group contains a primary and / or secondary moiety, e.g., methyltri(dimethylamino)tin (MeSn(NMe2)3) or isopropyltri(dimethylamino)tin (iPrSn(NMe2)3), the synthesis can be carried out using lithium dimethylamide and alkyltin trichloride (amination) according to the method of Lorberth (Journal of Organometallic Chemistry; 16(2), pp. 235 - 48 (1969)). See also Jones and Lappert (Organometal. Chem. Rev.; 1, p. 67 (1966)) as shown in Scheme (III). However, this reaction usually produces significant amounts of dialkyltin and other tin impurities. RSnCl3 + LiN(Me2)3 → RSn(NMe2)3 (III)

[0008] Instead, when the alkyl group contains a tertiary alkyl moiety, e.g., tert - butyltris(dimethylamino)tin (t - BuSn(NMe2)3), the compound must be synthesized using an alkylating reagent that converts stannatetetraamide by controlling the stoichiometry according to the method reported by Hanssgen et al. (Journal of Organometallic Chemistry, 293(2), pp. 191 - 5 (1985)) as shown in Scheme (IV). RLi + Sn(NMe2)4 → RSn(NMe2)3 (IV)

[0009] The reaction of Scheme (IV) using an alkylating reagent and tetraamide is not effective for the preparation of primary and secondary monoalkyltin triamide compounds. Rather, the use of a primary alkylating reagent converts stannatetetraamide to trialkyltin amide and unreacted tetraamide even when the correct stoichiometry is used. Secondary alkylating reagents also convert stannatetetraamide to polyalkyltin compounds.

[0010] The alkyl group in the monoalkyltin triamide compound is a tertiary alkyl group, for example, t-BuSnCl3, and Hanssgen et al. also reported that this compound rapidly decomposes at room temperature to produce SnCl2 and t-BuCl. Therefore, the tertiary monoalkyltin triamide compound cannot be prepared by synthesis using lithium dimethylamide and alkyltin trichloride.

[0011] Distillation is a well-developed technique for separating materials in a mixture based on their relative volatilities. The exact implementation of the distillation method depends on the characteristics, composition, and amount of the mixture to be separated. Distillation can be used and has been used to reduce the metal contamination of many materials including organometallic compounds.

[0012] For example, U.S. Patent Application Publication No. 2019 / 0337969 describes an organometallic tin compound having a low concentration of metal impurities as a result of using a multi-stage distillation method as compared to the methods commonly used for desalination of seawater. U.S. Patent Application Publication No. 2020 / 0239498 describes the purification of monoalkyltin trialkoxides and monoalkyltin triamides using fractional distillation and / or ultrafiltration methods for the removal of metal impurities and fine particulates. The removal of metal impurities from similar compounds is also described in U.S. Patent Application Publication No. 2020 / 0241413.

[0013] U.S. Patent No. 10,787,466 and U.S. Patent No. 10,732,505 describe organotin hydroxide, alkoxide, and amide compounds of low purity. However, only the t-butyl analog has been demonstrated to have extremely low levels of impurities.

[0014] U.S. Patent No. 8,901,335 describes the purification of a long list of organometallic compounds using a stripping column and a gas stream. More volatile impurities are removed from the organometallic compounds, and the metal impurity content is reduced to a specified level. U.S. Patent No. 11,156,915 relates to the purification of a chemically or radiation-sensitive compound containing a tin compound, using filtration to remove particulates. Finally, U.S. Patent No. 5,274,149 teaches a method for producing an alkylarsine compound including a distillation step, and it is taught that this alkylarsine compound contains substantially no metal impurities or oxygenated impurities.

Prior Art Documents

Patent Documents

[0015]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Documents

[0016]

Non-Patent Document 1

[0017] The ability to prepare and isolate alkylaminostannane compounds having a very high desired purity level is of great interest for use in the microelectronics industry. [[Means for Solving the Problems]]

[0018] In one aspect of the present disclosure, formula (1): R 1 Sn(NR 2 2)3(1) (wherein R 1 is selected from R A , R B , and R C , and R Ais a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, R C is a tertiary alkyl group having about 3 to 10 carbon atoms, each R 2 is, independently, an alkyl group having about 1 to 10 carbon atoms) having, and having a purity of at least about 99 mol%, a monoalkyltin triamide compound, R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) having a content of less than about 1 mol% is provided.

[0019] In another aspect of the present disclosure, formula (1a): R 1 Sn(NR 2 2)3(1a) (wherein R 1 is selected from R A and R B ), R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, each R 2 is, independently, an alkyl group having about 1 to 10 carbon atoms) having, and a method for synthesizing a monoalkyltin triamide compound having a purity of at least about 85 mol%, (a) lithiating a solution containing dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10% by mass; (b) adding a solution containing alkyltrichlorostannane and a second solvent, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of alkyltrichlorostannane; (c) removing the LiCl salt product by filtration, and (d) Removing the first solvent and the second solvent under vacuum to produce a crude product containing monoalkyltin triamide having the formula (1a) A method comprising the same is provided.

[0020] In a further aspect of the present disclosure, formula (1): R 1 Sn(NR 2 2)3(1) (wherein R 1 is selected from R A , R B , and R C , and R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, R C is a tertiary alkyl group having about 3 to 10 carbon atoms, each R 2 is independently an alkyl group having about 1 to 10 carbon atoms) A method of storing a sample of a monoalkyltin triamide compound having the formula (1) and having a purity of at least about 99 mol%, comprising storing a sample of a monoalkyltin triamide compound having the formula (1) at a temperature below about 30 °C without exposure to light.

[0021] Advantageous improvements of the present invention that can be introduced alone or in combination are specified in the dependent claims.

[0022] In summary, the following embodiments are proposed as particularly preferred within the scope of the present invention:

[0023] Embodiment 1: Formula (1): R 1 Sn(NR 2 2)3(1) (wherein R 1 is selected from R A , R B , and R C , and RA is a primary alkyl group having from about 1 to 10 carbon atoms, and R B is a secondary alkyl group having from about 3 to 10 carbon atoms, and R C is a tertiary alkyl group having from about 3 to 10 carbon atoms, each R 2 is, independently, an alkyl group having from about 1 to 10 carbon atoms) and having a monoalkyltin triamide compound having a purity of at least about 99 mol%, R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) content of less than about 1 mol%, a compound.

[0024] Embodiment 2: Formula (2) R 1 2Sn(NR 2 2)2(2) having a content of dialkylbis(dialkylamino)tin of less than about 1 mol%, the monoalkyltin triamide compound according to Embodiment 1.

[0025] Embodiment 3: The total content of tetrakis(dialkylamino)tin is less than about 1 mol%, the monoalkyltin triamide compound according to Embodiment 1 or 2.

[0026] Embodiment 4: The content of tetraalkyltin is less than about 1 mol%, the monoalkyltin triamide compound according to any one of Embodiments 1 to 3.

[0027] Embodiment 5: The color is substantially colorless, the monoalkyltin triamide compound according to any one of Embodiments 1 to 4.

[0028] Embodiment 6: The APHA is less than about 20, the monoalkyltin triamide compound according to Embodiment 5.

[0029] Embodiment 7: R 1 is an isopropyl group, and R 2is a methyl group, and the compound is of formula (3):

[0030] [Chemical formula]

[0031] The monoalkyltin triamide compound according to any one of Embodiments 1 to 6, having

[0032] Embodiment 8: The monoalkyltin triamide compound according to Embodiment 7, wherein the content of diisopropylbis(dimethylamino)tin is less than about 1 mol%.

[0033] Embodiment 9: The monoalkyltin triamide compound according to Embodiment 8, wherein the total content of tetrakis(dimethylamino)tin is less than about 1 mol%.

[0034] Embodiment 10: R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) has a content of less than about 0.05 mol%, and the monoalkyltin triamide compound according to any one of Embodiments 1 to 9.

[0035] Embodiment 11: A method for synthesizing a monoalkyltin triamide compound having formula (1a): R 1 Sn(NR 2 2)3(1a) (wherein R 1 is selected from R A and R B , R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, each R 2 is independently an alkyl group having about 1 to 10 carbon atoms) and having a purity of at least about 85 mol%. (a) Lithiating a solution containing dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10% by mass; (b) Adding a solution containing an alkyltrichlorostannane and a second solvent, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of alkyltrichlorostannane; (c) Removing the LiCl salt product by filtration; and (d) Removing the first solvent and the second solvent under vacuum to produce a crude product containing a monoalkylstannane triamide having the formula (1a). A method comprising the above steps.

[0036] Embodiment 12: The method according to Embodiment 11, wherein the compound having the formula (1a) has a purity of at least about 99 mol%.

[0037] Embodiment 13: The compound having the formula (1a) contains less than about 1 mol% of R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2), and the method according to Embodiment 11 or 12.

[0038] Embodiment 14: The compound having the formula (1a) contains less than about 0.05 mol% of R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2), and the method according to Embodiment 13.

[0039] Embodiment 15: The method according to any one of Embodiments 11 to 14, wherein step (b) is carried out at about -78°C to 40°C.

[0040] Embodiment 16: The method according to Embodiment 15, wherein step (b) is carried out at about 0°C to about 10°C.

[0041] Embodiment 17: The method according to any one of Embodiments 11 to 16, wherein the first solvent and the second solvent are each independently selected from the group consisting of a hydrocarbon solvent, an aromatic solvent, and an ether solvent.

[0042] Embodiment 18: The method according to any one of Embodiments 11 to 17, wherein steps (a) to (d) are carried out substantially without exposure to light.

[0043] Embodiment 19: The method according to any one of Embodiments 11 to 18, wherein steps (a) and (b) are carried out in a stainless steel container.

[0044] Embodiment 20: The method according to Embodiment 11, further comprising a step of distilling the compound having the formula (1a).

[0045] Embodiment 21: The distillation is a step of distilling the crude product having the formula (1a) at about 1 torr, a step of discarding any distillate before the boiling point of the monoalkyltriamide having the formula (1a), and a step of collecting the distillate obtained at the boiling point of the monoalkylstannic triamide having the formula (1a) to produce a product containing at least about 99 mol% of the monoalkylstannic triamide having the formula (1a) The method according to Embodiment 20, comprising.

[0046] Embodiment 22: comprising a step of performing fractional distillation using an operating pressure of about 0.1 to 50 torr and a pot temperature of about 50 to 120 °C, The method according to Embodiment 20 or 21, wherein the purified monoalkylstannic triamide compound having the formula (1a) contains less than about 0.1 mol% of the dialkylbis(dialkylamino)stannane compound having the formula (2).

[0047] Embodiment 23: The method according to any one of Embodiments 20 to 22, comprising a step of performing distillation substantially without exposure to light.

[0048] Embodiment 24: A method according to any one of Embodiments 20 to 23, comprising a step of performing distillation using a condenser temperature within about 1 to 10 °C, which is the dew point of a monoalkyltin triamide compound having the formula (1a) with an operating pressure and reflux ratio of about 10 to 100.

[0049] Embodiment 25: A method according to any one of Embodiments 20 to 24, wherein the distillation is performed using a stainless steel column filled with a stainless steel packing material.

[0050] Embodiment 26: A method according to any one of Embodiments 20 to 25, wherein the distillation is performed in a light-shielded apparatus containing glass.

[0051] Embodiment 27: Formula (1): R 1 Sn(NR 2 2)3(1) (wherein R 1 is selected from R A R B and R C and R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, R C is a tertiary alkyl group having about 3 to 10 carbon atoms, each R 2 is independently an alkyl group having about 1 to 10 carbon atoms) A method for storing a sample of a monoalkyltin triamide compound having the formula (1) and having a purity of at least about 99 mol%, comprising a step of storing a sample of a monoalkyltin triamide compound having the formula (1) substantially without exposure to light and at a temperature of less than about 30 °C.

[0052] Embodiment 28: The method according to Embodiment 27, wherein a sample of the monoalkyltin triamide compound having the formula (1) is stored for about 3 days to about 1 year.

[0053] Embodiment 29: The method according to Embodiment 27 or 28, wherein a sample of monoalkyltin triamide undergoes substantially no decomposition after a storage time of about 3 days to about 1 year.

[0054] Embodiment 30: R in a sample of monoalkyltin triamide having the formula (1) 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) has a content of less than about 1 mol%, the method according to any one of Embodiments 27 to 29.

[0055] Embodiment 31: R in a sample of monoalkyltin triamide having the formula (1) 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) has a content of less than about 0.05 mol%, the method according to Embodiment 30.

[0056] Embodiment 32: R 1 is selected from R A and R B , and (a) lithiating a solution containing dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10% by mass, (b) adding a solution containing alkyltrichlorotin and a second solvent, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of alkyltrichlorotin, (c) removing the LiCl salt product by filtration, and (d) removing the first solvent and the second solvent under vacuum to produce a crude product containing monoalkyltin triamide having the formula (1) A monoalkyltin triamide compound having the formula (1), produced by a method comprising:

[0057] Embodiment 33: The method according to Embodiment 32, wherein step (b) is carried out at about -78 °C to about 40 °C.

[0058] Embodiment 34: The method according to embodiment 33, wherein step (b) is carried out at about 0 °C to about 10 °C.

[0059] Embodiment 35: The method according to any one of embodiments 32 to 34, wherein the first solvent and the second solvent are each independently selected from the group consisting of a hydrocarbon solvent, an aromatic solvent, and an ether solvent.

[0060] Embodiment 36: The method according to any one of embodiments 32 to 35, wherein steps (a) to (d) are carried out substantially without exposure to light.

[0061] Embodiment 37: The method according to any one of embodiments 32 to 36, wherein steps (a) and (b) are carried out in a stainless steel container.

[0062] Embodiment 38: The method according to any one of embodiments 32 to 37, further comprising a step of distilling the compound having the formula (1).

[0063] The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, presently preferred embodiments are shown in the drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. The drawings are as follows.

Brief Description of the Drawings

[0064]

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DETAILED DESCRIPTION OF THE INVENTION

[0065] According to one aspect of the present disclosure, a monoalkyltin triamide compound represented by formula (1) and having a purity of at least about 99 mol% is provided. In a preferred embodiment, the compound having formula (1) contains a dialkylbis(dialkylamino)tin compound having formula (2) in an amount of about 1 mol% or less based on the total amount of tin. R 1 Sn(NR 2 2)3(1) R 1 2Sn(NR 2 2)3(2)

[0066] In formulas (1) and (2), R 1 is R A 、RB and R C is selected from. R A is a primary alkyl group having about 1 to 10 carbon atoms, preferably about 1 to about 5 carbon atoms, and includes methyl, ethyl, n-propyl, n-butyl, n-pentyl, etc. Preferred groups are methyl or ethyl groups. R B is a secondary alkyl (linear alkyl or cycloalkyl) group having about 3 to 10 carbon atoms, more preferably about 3 to about 5 carbon atoms, for example, without limitation, isopropyl, isobutyl, sec-butyl, cyclohexyl, cyclopentyl, cyclobutyl, cyclopropyl, isopentyl, sec-pentyl, etc. Currently preferred are isopropyl and cyclopentyl groups. R C is a tertiary alkyl group having about 3 to 10 carbon atoms, for example, tert-pentyl, 3-ethyl 3-pentyl, methyl 3-pentyl, methylcyclopentyl, methylcyclohexyl and preferably t-butyl.

[0067] Each R 2 is independently an alkyl group having about 1 to 10 carbon atoms, preferably about 1 to 5 carbon atoms, which includes methyl, ethyl, propyl, butyl, pentyl, etc. Preferred are methyl or ethyl groups.

[0068] The R in the compound having formula (1), also referred to herein as compound (4) 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) total content is preferably less than about 1 mol%, preferably even lower as described below. Further, the content of the compound having formula (2) is preferably less than about 1 mol%, preferably even lower as described below.

[0069] All numerical ranges expressed in this disclosure include all values within the range, including amounts and fractional amounts. Thus, the content of the compounds having formulas (4) and (2) is, independently of each other, preferably less than about 0.9 mol%, less than about 0.8 mol%, less than about 0.7 mol%, less than about 0.6 mol%, less than about 0.5 mol%, less than about 0.4 mol%, less than about 0.3 mol%, less than about 0.2 mol%, less than about 0.1 mol%, less than about 0.05 mol%, less than about 0.04 mol%, less than about 0.03 mol%, less than about 0.02 mol%, less than about 0.01 mol%, or 119 undetectable by Sn NMR, i.e., the compounds having formulas (4) and (2) are undetectable in a sample of the compound having formula (1) in some embodiments.

[0070] If the content of the compound having formula (2) is too high, this high content reduces the crosslinkability and toughness when the material is used in an EUV lithography resist. Further, the compound having formula (2) can cause gas generation when the photoresist is irradiated with extreme ultraviolet light, which can lead to degradation of very expensive multilayer-coated optical equipment in harsh situations. As described below, the dialkyltin impurity levels can be reduced to low levels undetectable by Sn NMR by utilizing carefully controlled reaction and distillation conditions. 119 It is possible to reduce them to low levels undetectable by Sn NMR. However, for industrial-scale reactions, for example, on a product scale exceeding 0.5 kg, it is often sufficient and practical to control the impurities to be limited to less than about 0.3 mol%, more preferably less than about 0.1 mol% based on stable production and economic considerations.

[0071] In a preferred embodiment, R 1 is an isopropyl group, R 2 is a methyl group, and the compound having formula (1) is (iPr)Sn(NMe2)3 (formula (3)) (wherein the dialkyltin impurity is (iPr)2Sn(NMe2)2). In some embodiments, when the compound has formula (3), the compound has a purity of at least about 99 mol% and contains about 1 mol% or less of (iPr)2Sn(NMe2)2.

[0072] [Chem.]

[0073] In some embodiments, the content of tetrakis(dialkylamino)tin (e.g., tetrakis(dimethylaminotin)) in the monoalkyltin triamide compound having the formula (1) is less than about 1 mol%. In some embodiments, the content of tetraalkyltin (e.g., tetrakis(isopropyl)tin in (iPr)Sn(NMe2)3 described above) in the monoalkyltin triamide compound having the formula (1) is less than about 1 mol%. The contents of tetrakis(dialkylamino)tin and tetraalkyltin (e.g., tetrakis(dimethylaminotin) and tetrakis(isopropyl)tin in iPrSn(NMe2)3) are each independently preferably less than about 0.9 mol%, less than about 0.8 mol%, less than about 0.7 mol%, less than about 0.6 mol%, less than about 0.5 mol%, less than about 0.4 mol%, less than about 0.3 mol%, less than about 0.2 mol%, less than about 0.1 mol%, less than about 0.05 mol%, less than about 0.04 mol%, less than about 0.03 mol%, less than about 0.02 mol%, less than about 0.01 mol%, or 119 undetectable by 119Sn NMR, i.e., these compounds are undetectable in a sample of the compound having the formula (1).

[0074] If the contents of tetrakis(dimethylaminotin) and tetraalkyltin are too high, when the material is used in an EUV lithography resist, defects may be caused due to the boiling points and molecular weights of these compounds. As described below, by utilizing carefully controlled reaction and distillation conditions, 119 it is possible to reduce the impurity levels of these compounds to levels that are undetectable by 119Sn NMR. However, for industrial-scale reactions, e.g., product scales exceeding 0.5 kg, it can be practical to control the impurities to be less than about 0.3 mol%, more preferably less than about 0.1 mol% based on stable production and economic considerations.

[0075] In some embodiments, R, also referred to herein as compound (4), 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) has a total content of less than about 1 mol%, and may be a compound having the formula R A Sn(NMe2)2(NMeCH2NMe2) or R B (NMe2)2(NMeCH2NMe2). When the compound having formula (4) is iPrSn(NMe2)2(NMeCH2NMe2) (formula (5)), this compound has 119 a chemical shift around -84 ppm in the 119Sn NMR spectrum: 119 119Sn NMR (223.8 MHz; C6D6): δ -84 ppm. 1 1H NMR (600 MHz; C6D6): δ 3.37 (s, 2H, CH2), 2.89 (s, 3H, Sn-NMe), 2.86 (s, 12H, Sn-(NMe2)2), 2.15 (s, 6H, NMe2), 1.68 (m, 1H, iPr), 1.33 (s, 6H, iPr).

[0076] [Chemical formula]

[0077] The content of the compound having formula (4) or (5) is preferably less than about 1 mol%, less than about 0.9 mol%, less than about 0.8 mol%, less than about 0.7 mol%, less than about 0.6 mol%, less than about 0.5 mol%, less than about 0.4 mol%, more preferably less than about 0.3 mol%, even more preferably less than about 0.2 mol%, less than about 0.1 mol%, less than about 0.05 mol%, etc.

[0078] As described above, by utilizing carefully controlled reaction and distillation conditions, it is possible to reduce the level of the compound having formula (4) or (5) to less than about 0.1 mol%, for example, to less than about 0.05 mol%. However, for industrial-scale reactions, for example, for product scales exceeding 0.5 kg, it is often practical to control the impurities to less than about 0.3 mol%, preferably less than about 0.1 mol% based on stable production and economic considerations.

[0079] In some embodiments, the monoalkyltin triamide compound having formula (1) is substantially colorless. In some embodiments, the monoalkyltin triamide compound having formula (1) has an APHA color of less than about 20. The APHA color of the composition containing the tin compound can be controlled during distillation, for example, by using light shielding or a suitable distillation apparatus as described below (e.g., by minimizing the formation of colored impurities).

[0080] APHA color, also known as the Hazen or platinum / cobalt (Pt / Co) scale, is commonly used in the chemical industry as a measure of yellowness to evaluate the color of liquids that appear colorless to yellow. The measured value of yellowness (APHA color) is compared to a standard solution containing potassium hexachloroplatinate(IV), cobalt(II) chloride (Pt / Co), and hydrochloric acid in water. The APHA color scale ranges from 0 to 500, and a color of APHA 1 is equivalent to 1 ppm of Pt / Co. APHA color can be evaluated as described in ASTM D1209-05(2019), either through visual comparison with a standard substance or using a spectrophotometer.

[0081] The organotin compound having formula (1) can be used in the formation of high-resolution EUV lithography - pattern forming precursors, which is interesting because of their high purity and the minimized concentration of the dialkyl impurity having formula (2) and the additional impurities described above.

[0082] Synthesis method Aspects of the present disclosure further relate to methods for synthesizing high-purity alkyltin compounds having formula (1) above, suitable for use in the microelectronics industry. These high-purity compounds are substantially free of dialkyltin compounds having formula (2) and / or impurities having formula (4) or (5), can have a desired color level, and can be prepared without using multi-stage distillation or, in some embodiments, without any purification.

[0083] For the purposes of the present disclosure, the term "high-purity" can be considered to mean greater than about 99 mole %, more preferably greater than about 99.1 mole %, greater than about 99.2 mole %, greater than about 99.3 mole %, greater than about 99.4 mole %, greater than about 99.5 mole %, greater than about 99.6 mole %, greater than about 99.7 mole %, greater than about 99.8 mole %, greater than about 99.9 mole %, greater than about 99.95 mole %, greater than about 99.98 mole %, greater than about 99.99 mole %, or even higher purity. The term "substantially free of" can be considered to mean that the impurity is 119 undetectable by Sn NMR, in which case 119 Sn NMR can have a detection limit as low as 0.3 mole %, 0.1 mole %, 0.05 mole %, or 0.04 mole % (depending on the particular compound or impurity) when the sample is tested using specific conditions without dilution in a deuterated solvent, e.g., using more than 2000 scans. For the particular impurities described herein, the detection limit is 0.01 mole %.

[0084] 119 Sn NMR spectroscopy is ideally suited for quantitative analysis of monoalkyltin compounds because of its high sensitivity to small structural changes and its large spectral range of 6500 ppm (see Davies et al., Eds.; Tin Chemistry: Fundamentals, Frontiers, and Applications; Wiley (2008)). This allows 119Since Sn resonance has extremely high resolution, easy identification and quantification of monoalkyltin compounds and their impurities are possible. 119 Sn NMR has the problem of low sensitivity compared to other analytical methods, such as GC, HPLC, or 1 H NMR. To improve the sensitivity, monoalkyltin compounds are analyzed without dilution, and to measure the low-level impurities described in this study, acquisition of many spectra (at least 2000, preferably more than 10,000 for unknown impurity detection) is performed. Using this method, the detection limits of 0.01 mol% of dialkyltin diamide and other Sn compounds, such as the compounds having formulas (2), (4), and (5), can be achieved. In the case of Sn(NMe2)4, the detection limit is 0.3 mol% because the peak is broad.

[0085] As described herein 119 The Sn NMR data were obtained using a method similar to the relative purity method described in J. Med. Chem. (57, 22, 9220 - 9231 (2014)). 119 The Sn NMR spectra were acquired using an inverse gate with a 45° pulse, a 1-second relaxation delay, and sufficient scans to achieve the required sensitivity 1 H decoupling. The samples were prepared without dilution in a deuterated solvent. Quantification was performed by integrating all the peaks of the spectra and setting the total peak area to 100. Each peak of the spectrum represents a distinct tin compound, and the area of each peak represents the concentration or purity of that compound in mol%.

[0086] Generally, a method for preparing a monoalkyltin triamide compound according to an aspect of the present disclosure includes the following general steps, each of which is described below: 1. A step of lithiating a solution of dimethylamine and a first solvent to produce lithium dimethylamide. 2. A step of adding a solution containing alkyltrichlorotin and a second solvent to the lithium dimethylamide solution with stirring. 3. A step of removing the LiCl salt product by filtration, 4. A step of removing the solvent under vacuum to produce a crude product, and optionally 5. A step of distilling the crude product to produce a product containing at least about 99 mol% of monoalkyltin triamide.

[0087] As previously described, the reaction conditions and parameters, such as the solvent, the relative amounts of reactants, stirring conditions, temperature, and concentration, should be carefully controlled to ensure the production of the desired compound in high purity.

[0088] Solvent The first and second solvents are not particularly limited, but preferred solvents include hydrocarbons (e.g., but not limited to hexane, hexanes, heptane, and cyclohexane), aromatics (e.g., but not limited to toluene and xylene), and ethers (e.g., but not limited to THF and Et2O), and mixtures thereof. Particularly preferred as the main component of the solvent for the removal of LiCl by filtration are hydrocarbons and aromatics. Toluene and hexane are currently the most preferred solvents for the easy removal of the product under vacuum and at low temperature after the reaction. Further, an ether, for example, the most preferred THF, is a currently preferred solvent because of the high solubility of lithium dimethylamide among these types of solvents. The use of mixtures of these solvents is also within the scope of the present disclosure. In some embodiments, the solvent used for the lithiation step and the solvent used for the amination step are the same.

[0089] Amount of lithium dimethylamide The preferred amount of lithium dimethylamide relative to alkyltrichlorostannane is more than about 3.0 equivalents, more than about 3.05 equivalents, more than about 3.09 equivalents, more than about 3.10 equivalents, or more than about 3.15 equivalents. If the amount of lithium dimethylamide is too low, the reaction speed becomes too slow and the amount of impurities increases due to side reactions such as redistribution.

[0090] Stirring Conditions during the Addition of Alkyltrichlorotin The stirring speed during the addition of alkyltrichlorotin has great significance in determining the purity of the resulting product. Since the solution of lithium amide in hexane or toluene is actually a heavy slurry, high-speed stirring is preferred for sufficient mixing. On the other hand, stirring at too high a speed may cause problems for the motor due to the heaviness of the slurry. The preferred stirring speed is greater than about 10 rpm, greater than about 20 rpm, greater than about 40 rpm, more preferably greater than about 60 rpm, and most preferably greater than about 100 rpm. On the other hand, the preferred stirring speed is less than about 500 rpm, less than about 400 rpm, less than about 300 rpm, more preferably less than about 250 rpm, and most preferably less than about 200 rpm. To achieve good mixing, the selection of an appropriate shape and size of the stirring blade is important. For example, suitable stirring blades include paddle blades, anchor blades, twin star blades, ribbon blades, three-blade retreat impellers, and logbone blades. In the reaction (amination) between the lithium amide slurry and alkyltrichlorotin, it is important to have a high blade peripheral speed. This is because the miniaturization and high reactivity of the lithium amide slurry result in high shear stress being achieved at the blade peripheral speed (blade tip speed, m / s). The preferred blade peripheral speed is about 0.1 rpm or more, preferably 0.3 rpm or more, most preferably 0.5 rpm or more, and 1000 rpm or less, preferably 100 rpm or less, and most preferably 50 rpm or less. The blade peripheral speed is calculated by the following formula (a): Blade Peripheral Speed (m / s) = π × D × N / 60 (a) In formula (a), D represents the blade diameter (m) and N represents the rotational speed (rpm).

[0091] Temperature For the lithiation step, preferred low temperatures are about -78 °C, about -40 °C, about -20 °C, about -10 °C, or most preferably the low temperature is about 0 °C, and the upper limit of the temperature is about 40 °C, about 20 °C, or most preferably the upper limit is about 10 °C. Thus, the preferred temperature range is about 0 °C to about 10 °C. If the reaction temperature for lithiation is too low, the viscosity of the reactants may be too high. Conversely, if the reaction temperature is too high, HNMe2 will evaporate.

[0092] For the step of adding alkyltrichlorostannane (amination), preferred low temperatures are about -78 °C, about -40 °C, about -20 °C, about -10 °C, most preferably about 0 °C, and the upper limit of the temperature is about 40 °C, about 25 °C, about 20 °C, or most preferably the upper limit is about 10 °C. Thus, the preferred temperature range is about 0 °C to about 10 °C. However, in other embodiments, the reaction is preferably carried out at room temperature. If the temperature is too low, the reaction rate will be too slow, while if the temperature is too high, by-products will be generated.

[0093] Lithium dimethylamide concentration Lithium dimethylamine is currently present in the solution in an amount up to about 30% by mass, more preferably up to about 20% by mass, up to about 15% by mass, or up to about 10% by mass. This dilution concentration has been found to provide an effective slurry for solid and liquid reactants. On the other hand, productivity is lower under dilution conditions in industrial settings.

[0094] According to an aspect of the present disclosure, for the method of preparing a monoalkylstannamide compound having the formula (1a) R 1 Sn(NR 2 2)3(1a) comprises the following steps, each of which is described in more detail below: (a) A step of lithiating a solution containing dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10% by mass. (b) A step of adding a solution containing an alkyltrichlorostannane and a second solvent, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of the alkyltrichlorostannane, (c) A step of removing the LiCl salt product by filtration, and (d) A step of removing the first solvent and the second solvent under vacuum to produce a crude product containing a monoalkylstannane triamide having the formula (1a).

[0095] In formula (1a), R 1 is selected from R A and R B , R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, and each R 2 is, independently, an alkyl group having about 1 to 10 carbon atoms.

[0096] When the steps (a) to (d) of the method are carried out substantially without exposure to light, for example, when at least steps (a) and (b) are carried out in an amber or stainless steel reactor, that is preferred. Exposure to light has a harmful effect on the monoalkylstannane triamide compound as described below.

[0097] In some embodiments, the first solvent and the second solvent are the same.

[0098] The first step of this method involves lithiating dimethylamine in a solution of a first solvent such as hexane in an amount up to 10% by weight (but not exceeding this). This dilution concentration has been found to provide an effective slurry for solid and liquid reactants. Lithiation is carried out in some embodiments at a preferred temperature of about -10°C to about 10°C, and about 0°C to about 10°C. Lithiation can be carried out using n-BuLi or other common lithiating reagents commonly used in the art, such as t-BuLi or HexylLi. Such lithiating agents are commonly utilized in hexane solution, and additional hexane can be added so that lithium dimethylamide is present in the desired concentration range. An excess of dimethylamine is required to ensure complete reaction of the lithiating reagent. The reaction is carried out under an inert atmosphere, for example, under nitrogen or argon, and the addition rate is controlled to limit the exothermic reaction. After the addition is complete, the reaction mixture is warmed to room temperature to vaporize the butane by-product and excess dimethylamine, and then, in some embodiments, cooled to about -10°C to about 10°C, or about 0°C to about 10°C.

[0099] In the second step of this method, an alkyltrichlorostannane solution in a second solvent such as toluene is added to the reaction mixture, and in some embodiments, this is maintained at a preferred temperature of about -10°C to about 10°C, or about 0°C to about 10°C. The alkyltrichlorostannane is added such that the amount of lithium dimethylamide is at least about 3.09 equivalents relative to the amount of alkyltrichlorostannane. The alkyltrichlorostannane solution is preferably added in droplet form to control the exothermic reaction. The second step of this method is preferably carried out under an inert atmosphere, for example, under nitrogen or argon.

[0100] After the addition of the alkyltrichlorotin to the reaction mixture is complete, the reaction mixture is slowly warmed to room temperature over a period of, for example, about 4 hours and then stirred at room temperature for an additional period, for example, about 4 hours. The reaction mixture is then filtered, for example, through a filter aid, to remove the LiCl by-product. Other filtration means known in the art can also be utilized. The resulting salt is then washed, for example, with anhydrous hexane, and the solvents (e.g., hexane and toluene) are removed under reduced pressure by means known in the art to produce a crude product containing at least about 85 mol% of monoalkylstannic triamide.

[0101] Finally, in some embodiments, the crude product having the formula (1a) is distilled, for example, at about 1 torr using, for example, a 300 mm Pro-Pak column, and any distillate is discarded before the boiling point of the monoalkylstannic triamide is reached, and only the distillate obtained at the boiling point of the monoalkylstannic triamide is collected to produce a product containing at least about 99 mol% of monoalkylstannic triamide having the formula (1a). The boiling points of two representative monoalkylstannic triamides are shown in Table 1. As an example, if the desired product is methylstannic triamide, the distillate obtained at less than 34 °C is discarded and only the distillate obtained at 34 - 35 °C is collected.

[0102]

Table 1

[0103] The distillate obtained at a boiling point such as 34 - 35 °C for methylstannic triamide contains a monoalkylstannic triamide compound having a purity of at least about 99 mol%. For example, if the desired compound having the formula (1a) is methylstannic triamide, it shows peaks at δ - 16.78 (99.5%) and δ 56.23 (0.5%) 119 The Sn NMR (neat) spectrum is consistent with the published data for methylstannic triamide and dimethylstannic diamide, respectively.

[0104] After distillation, the compound having the formula (1a) contains less than about 1 mol% of R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) or less than about 0.05 mol% of R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2).

[0105] A further aspect of the present disclosure is a compound of formula (1): R 1 Sn(NR 2 2)3(1) (wherein R 1 is selected from R A and R B , R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, each R 2 is independently an alkyl group having about 1 to 10 carbon atoms) and a method for synthesizing a monoalkyltin triamide compound having at least about 85 mol% purity, comprising (a) lithiating a solution containing dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10% by weight; (b) adding a solution containing alkyltrichlorostannane and a second solvent, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of alkyltrichlorostannane; (c) removing the LiCl salt product by filtration, and (d) removing the first solvent and the second solvent under vacuum to produce a crude product containing monoalkyltin triamide having the formula (1), wherein the first solvent is the same as the second solvent, and distilling the compound having the formula (1) The present invention relates to a method comprising

[0106] One method for preparing an isopropyltin triamide compound having formula (3) in accordance with an aspect of the present disclosure includes the following steps: (a) lithiating dimethylamine in a hexane solution at about 0 °C to 10 °C to produce lithium dimethylamide having a concentration in hexane of up to about 10% by weight; (b) adding a solution of isopropyltrichlorotin in toluene at about 0 to 10 °C, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of isopropyltrichlorotin; (c) removing the LiCl salt product by filtration; and (d) removing hexane and toluene under vacuum to produce a product containing at least about 99 mol% of isopropyltin triamide having formula (3).

[0107] A second method for preparing an isopropyltin triamide compound having formula (3) in accordance with an aspect of the present disclosure includes the following steps: (a) lithiating dimethylamine in a THF solution at about 0 °C to 10 °C to produce lithium dimethylamide; (b) adding a solution of isopropyltrichlorotin in toluene at about 0 to 10 °C, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of isopropyltrichlorotin; (c) removing the LiCl salt product by filtration; and (d) removing THF and toluene under vacuum to produce a product containing at least about 99 mol% of isopropyltin triamide having formula (3).

[0108] The method for producing an isopropyltin triamide compound having formula (3) is the same as the method described above for producing a monoalkyltin triamide compound having formula (1), except that no distillation step may be required, i.e., the product obtained after step (b) is already at least about 99 mol% neat, which is different. The method described above for synthesizing an isopropyltin triamide compound having formula (3) can also be utilized to synthesize other alkyltin triamide compounds having formula (1) by changing only the alkyltrichlorotin reactant.

[0109] The isopropyltin triamide produced by the method according to the present disclosure is a substantially colorless liquid, 119 The Sn NMR (neat) spectrum shows peaks at δ -64.85 (99.8%) and δ -19.06 ppm (0.2%), which are consistent with the published and collected data for isopropyltin triamide and diisopropyltin diamide, respectively. However, if desired, the product can be further distilled to remove any unwanted organic impurities and / or by-products, and to isolate any photodegraded by-products. Contrary to the literature report of collecting the distilled product at 50 - 52 °C and 1.4 mTorr, the product obtained at 49 - 53 °C and 0.5 torr was found to have the desired high purity and was desirably colorless.

[0110] During the amination reaction to form the monoalkyltin triamide, the Kochi - Schukov - like equilibrium reaction shown in Scheme (I) also occurs, and the occurrence of the reaction is not prevented even at low temperatures, e.g., about -78 °C to 10 °C. Instead, the low temperature was found to slow down the substitution reaction and increase the risk of the equilibrium reaction. Further, light or heat promotes the equilibrium reaction, 119 and can form up to 15 mol% of the dialkyltin amide as determined by Sn NMR. According to the method reported by Lorberth, the amination reaction is carried out as a solid slurry in hexane, which is a liquid reaction.

[0111] The methods described herein solve known problems in several ways. First, as described herein, it has been found that lithium dimethylamide must be properly prepared in order to prevent the occurrence of an equilibrium reaction during the reaction. Second, the concentration of the reactants is diluted, for example, by using lithium dimethylamide as a hexane slurry at a concentration of about 10% by weight or less. Third, the equilibrium reaction is minimized by conducting the reaction at a preferred temperature around -10°C to 10°C or about 0°C to about 10°C rather than at a lower temperature. Finally, THF can be used in place of hexane to form a homogeneous solution of lithium dimethylamide. Using the methods described herein, iPrSn(NMe2)3 can be produced in very high purity (with dialkyltin compounds and other specified impurities being about 0.05 mol% or less) without purification on a pilot scale.

[0112] Purification A further aspect of the present disclosure further relates to a method for purifying a monoalkyltin triamide compound having formula (1) described above.

[0113] The purification methods encompassed by the present disclosure include the following: · A single-stage flash to remove metal contamination, · Fractional distillation to remove dialkyltin impurities as the heavy fraction, · Fractional distillation to remove tetra-alkyltin impurities as the light fraction, · Using fractional distillation to simultaneously remove di- and tetra-alkyltin impurities in either batch or continuous mode, · Using microchannel distillation to remove dialkyl and tetra-alkyl impurities with similar boiling points, · Fractional distillation to simultaneously remove metal contaminants along with di- and tetra-alkyltin impurities, · Using a light impermeable material to prevent the formation of photodegradation products of the organotin compound, · Distillation with a limited bottom temperature (e.g., less than 112°C) to limit the formation of tetra-alkyltin compounds · Operating the condenser at or near the dew point of the overhead product to increase the operating efficiency, · Treating the distillation residue from the first distillation process with concentrated dialkyltin impurities (via the same or a different purification process) to recover more of the desired isopropyltrimethylamine tin product and / or purified dialkyltin product, · Re-equilibrating di- and tetra-alkyl by-products to produce the desired isopropyltrimethylamine tin product, · Recycling the distillation residue obtained in the first distillation process to the final step of the manufacturing process and leveraging the equilibrium disproportionation reaction of the desired product to dialkyl and tetra-alkyl tin impurities, · Maintaining a minimum level of dialkyltin impurities in the feed to the distillation and leveraging the same equilibrium disproportionation reaction, · Using an adsorbent or ion exchange resin to reduce metal impurities, chloride impurities, water, and oxygen, and / or · Using an adsorbent to reduce color without introducing isopropyltrimethylamine tin decomposition products.

[0114] The size of the alkyl group (and the fact that it is similar in size to the NMe2 group) can affect the difference in boiling points between monoalkyltin triamides and dialkyltin diamides, and fractional distillation is generally an excellent method for isolating contaminants. As an example, i PrSn(NMe2)3 (A) and iThe difference in molecular weight between Pr2Sn(NMe2)2(B) is small (294 g / mol and 293 g / mol respectively). For the t-butyl compound, the triamido tin compound is 13 g / mol lighter than the diamido tin compound. For the isopropyl analog, the difference between the isopropyl group and the dimethylamino group is only 1 g / mol, and considering that the polarities are very similar, the difference in boiling points between compounds A and B can be extremely small. The boiling points of these two compounds with a purity > 97 mol% were measured over a wide pressure range and are shown in Figure 1. It can be observed that the difference in boiling points between the two compounds is within 2 °C in the pressure range of 0.7 - 10 torr. In another example, t BuSn(NMe2)3 and t the boiling points of Bu2Sn(NMe2)2 at 0.4 torr are 50 °C (measured value) and 90 °C respectively (reported in Chemische Berichte, 112(8), pages 2798 - 2803 (1979)). Therefore, purification by fractional distillation is difficult and requires specific distillation parameters developed specifically. By utilizing such a purification method, PrSn(NMe2)3 or an analog with < 0.5 mol% dialkyl, < 0.4 mol% dialkyl, < 0.3 mol% dialkyl, < 0.2 mol% dialkyl, < 0.1 mol% dialkyl, < 0.05 mol% dialkyl, or undetectable dialkyl tin compound contamination as described below can be provided. i PrSn(NMe2)3 or an analog

[0115] When the mass difference between the alkyl group and the amide group is large (e.g., the tBu-NMe2 pair has a difference of 13 amu), purification by fractional distillation is expected to be less difficult. When the difference is small, purification is expected to be more difficult. For example, the iPr-NMe2 pair has a difference of -1 amu (i.e., the iPr group is slightly lighter than the amide group). In other examples, the cyclohexyl-NMe2 pair has a molecular weight difference of 39 amu, and the cycloheptyl-NMe2 pair has a molecular weight difference of 53 amu. Schwarzenbach et al. (Environmental Organic Chemistry; pages 56 - 75 (1993)) have observed that an increase in the molecular weight of the components decreases the vapor pressure over a range of molecular weights for similar compounds. Essentially, compounds with more electrons have stronger London forces. However, this does not account for the non-ideal behavior frequently observed in multicomponent vapor-liquid equilibria.

[0116] A further aspect of the present disclosure relates to a method for purifying PrSn(NMe2)3 using fractional distillation to have a purity of at least about 85 mol%, further at least about 97 mol% or at least about 99 mol%. i The method includes performing fractional distillation using an operating pressure of about 0.1 to about 50 torr (e.g., greater than about 0.1 torr, greater than about 0.2 torr, greater than about 0.3 torr, preferably greater than about 0.5 torr, more preferably greater than about 1 torr, preferably less than about 50 torr, less than about 30 torr, less than about 20 torr, less than about 10 torr, most preferably about 1 torr). If the pressure is too high, the formation of decomposition and redistribution products is accelerated. If the pressure is too low, the volatilization rate becomes too high and the separation efficiency through the distillation column becomes too low.

[0117] Fractional distillation preferably uses a pot temperature of about 50 °C to about 120 °C (preferably exceeding about 50 °C, exceeding about 60 °C, preferably exceeding about 70 °C, preferably exceeding about 80 °C, preferably exceeding about 90 °C, preferably exceeding about 100 °C, most preferably exceeding about 105 °C, preferably less than about 120 °C, preferably less than about 115 °C, most preferably about 110 °C). If the pot temperature is too low, the volatilization speed will be too low and the distillation time will be too long. Conversely, if the pot temperature is too high, the decomposition of the product will be accelerated.

[0118] Fractional distillation preferably uses a condenser temperature within about 10 °C, more preferably within about 7 °C, more preferably within about 5 °C, more preferably within about 3 °C, most preferably within about 1 °C of the dew point of the desired compound having formula (1), e.g., iPrSn(NMe2)3, at an operating pressure and reflux ratio of about 10 to 100 (preferably about 20 to 80, more preferably about 40 to 60, more preferably about 50) used. Thereby, a sample of iPrSn(NMe2)3 having a purity exceeding about 99.5 mol% is obtained. In one embodiment, the purified sample of iPrSn(NMe2)3 contains less than about 0.1 mol% or is undetectable by Sn NMR of (iPr)2Sn(NMe2)2 as determined by known analytical methods such as GC and HPLC. 119 contains (iPr)2Sn(NMe2)2 which is also undetectable by Sn NMR.

[0119] Thus, according to the present disclosure i One method for purifying PrSn(NMe2)3 utilizes fractional distillation using a pot temperature of less than about 112 °C to avoid the formation of the tetramethylamido tin compound Sn(NMe2)4 and remove a substantial amount of the dialkyl tin compound (iPr)2Sn(NMe2)2.

[0120] For example, according to an aspect of the present disclosure i The following conditions can be utilized for the fractional distillation purification method of PrSn(NMe2)3: a pressure of 10 torr, a pot temperature of 105 °C, a condenser temperature of 95 °C, and a reflux ratio of 50. The feed purity is 97% iStarting from PrSn(NMe2)3, fractional distillation using these parameters produced a 99.5% fraction, which corresponds to 95.7% in the bottom product after removing 46 g from an initial charge of 8.6 kg. The purity was determined using 119 Sn NMR without diluting the sample with a deuterated solvent.

[0121] The monoalkyltin triamide compound can be disproportionated to obtain a dialkyltin diamide and a tetraamide compound. The extent of the disproportionation reaction is affected by the temperature in the distillation pot, and a higher temperature is expected to result in a higher degree of disproportionation. The activation energy of the disproportionation reaction is related to the size of the alkyl group (R). For example, when R is a methyl group, the disproportionation reaction can be observed around 45 °C. As another example, when R is an isopropyl group, the disproportionation reaction occurs around 110 °C. The disproportionation reaction of the tert-butyl group occurs at a higher temperature. The two impurities produced from the disproportionation reaction of the monoalkyltin triamide compound have different molecular weights from the starting monoalkyl compound due to the mass difference between the alkyl group and the amide group. One product is heavier than the starting monoalkyltin triamide, and the other product is lighter than the monoalkyltin triamide. As a result, it is expected that the lighter compound will appear in the distillation fraction and the heavier compound will appear in the bottom fraction from the distillation, ensuring the presence of both lighter and heavier impurities and making the distillation more difficult. Thus, it has been found that limiting the pot temperature and thus the extent of the disproportionation reaction not only improves the yield by limiting the loss of the desired monoalkyl product but also avoids the formation of additional impurities to be removed. As is well known in the art, determining the optimal conditions for separating similar components using distillation requires significant analysis and experimentation of various parameters that are neither simple nor predictable and are interrelated.

[0122] Photosensitivity Monoalkyltin triamide compounds are photosensitive, and thus it has been found that proper light protection is required during the reaction and purification. Newly prepared iPrSn(NMe2)3 is a colorless liquid. However, when an NMR sample of iPrSn(NMe2)3 is left standing in a laboratory under ordinary room lighting, the sample turns yellow. This discoloration is emphasized by the storage life data shown in Figure 2. After exposure to light, a new 119 Sn resonance is present at -84 ppm, which indicates the formation of a photolytic decomposition byproduct, a compound having the formula (5), iPrSn(NMe2)2(NMeCH2NMe2). The 119 Sn NMR representing the formation of the compound having the formula (5) is shown in Figure 3. The photolysis rate increases with increasing temperature. Therefore, maintaining a purified sample of iPrSn(NMe2)3 in the dark (without exposure to light) minimizes the formation of unwanted photolytic decomposition byproducts and 119 enables the provision of (iPr)Sn(NMe2)3 in which the total content of substances having a chemical shift around -84 ppm in the Sn NMR spectrum is less than 1% by mass. Control of light during the reaction steps for generating monoalkyltin triamide compounds is also important and can be achieved by using an amber or stainless steel reactor or a glass reactor that shields light.

[0123] Similarly, distillation may be carried out using a stainless steel column packed with stainless steel packing material. Alternatively, distillation may be carried out in a light-shielded apparatus containing glass, such as a glass apparatus, a glass-lined apparatus, a glass-coated apparatus, etc. The shielding can also be achieved by any method known in the art, such as using a light-shielding container, such as an amber glass, a metal (SUS) container, wrapping the container with a light-shielding cover, such as cloth, foil or film, using a light-shielding coating, or carrying out distillation in a dark room.

[0124] Storage A method of storing a sample of a monoalkyltin triamide compound having formula (1) and having a purity of at least about 99 mol% (e.g., samples greater than about 0.5 kg, but not limited to these) includes storing a sample of the monoalkyltin triamide compound having formula (1) substantially without exposure to light and at a temperature of less than about 30°C. A sample of the compound having formula (1) has an R content of less than about 1 mol% or less than about 0.05 mol%. 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) can be had.

[0125] A sample of the monoalkyltin triamide compound having formula (1) can be stored for a period of about 3 days to about 1 year, e.g., for a period of about 1 week or more, about 10 months or less, about 2 - 6 weeks, and all desired intermediate times. Preferably, the sample is stored at a temperature of less than about 30°C, less than about 25°C, less than about 20°C, preferably greater than about - 10°C. "Substantially without exposure to light" can be considered to mean that the sample is protected from exposure to light, to the extent possible, e.g., by storage in an amber or stainless steel container. In embodiments, a sample of the monoalkyltin triamide does not substantially decompose after a storage time of about 3 days to about 1 year as described above.

[0126] Reduction of additional impurities It is reasonable to presume that metal impurities in the alkyltin triamide compound exist as metal chlorides. If so, removal by an adsorbent, for example, BASF CL-750, a chloride adsorbent known in the art, may be affected. Additional chloride impurities, such as amine hydrochloride and lithium chloride, may be present, which are carried over in the production process and can become the impurities of concern. Removal by a chloride scavenging adsorbent, such as CL-750, activated carbon, or activated alumina, may be effective for removal. Finally, the desired tin compound may contain water and oxygen impurities. Metal halide-promoted and then activated carbon has been used to remove water and oxygen from HCl gas, and a similar approach may be effective.

[0127] The present invention will now be described in connection with the following non-limiting examples.

Example

[0128] Column Design and General Operations The following distillation parameters were utilized in the following examples: a. Glass-lined steel drain sump, nominal 16 liters b. 2" Schedule-40 316-SS heated column c. 0.24" 316L SS ProPak packing, total column length 5 feet (1.5 meters) d. Off / on reflux splitter operating at an apparent reflux ratio between 33 and 50 e. Stainless steel shell and tube condenser operating as a total condenser f. 304SS receiver vessel g. 316SS product vessel

Example

[0129] Demonstration of the Purification of (iPr)Sn(NMe2)3 by Distillation Using an (iPr)Sn(NMe2)3 sample with a purity of 97% as the feed, it was used at a reflux ratio of 50, an operating pressure of 10 Torr, a pot temperature of 105 - 105.2 °C, and a condenser temperature of 95 °C. The purity of the product fraction was 99.5%, without diluting the sample with a deuterated solvent, 119 When using Sn NMR, the two in-line distillate samples had (iPr)Sn(NMe2)3 with purities of 99.8% and 99.7%.

Example

[0130] (Effect of condenser temperature on the fractional distillation of (iPr)Sn(NMe2)3 The distillation operation of (iPr)Sn(NMe2)3 was carried out 3 times. After operating for a certain period (2 - 8 hours), the Fenske equation (alpha^N) was used to characterize the separation efficiency by performing analytical calculations on the samples collected from the pot and the receiver. The reflux ratio was 50 and the pressure was 10 Torr. The results are listed in Table 2 below, demonstrating that when evaluated as an improvement in separation efficiency, the condenser temperature has a significant effect on the overall performance of the distillation. The dew point of iPrSn(NMe2)3 was observed to be 96 °C. Therefore, operating the condenser approximated to the dew point of the product stream is advantageous for performing the separation and maximizing the column efficiency.

[0131]

Table 2

Example

[0132] (Effect of pot temperature on the formation of tetra-alkyl Sn(NMe2)4 impurities The tetraamide Sn(NMe2)4 impurity (6) is formed from the disproportionation reaction of (iPr)Sn(NMe2)3 and simultaneously generates the already existing dialkyl (iPr)2Sn(NMe2)2 impurity (7). This effect becomes significant when the pot temperature increases from 110 °C to 115 °C.

[0133]

Chemical formula

[0134] The tetraamide impurity (FW = 295.0) is a light component in distillation and thus appears in the distillate. Conversely, the dialkyl impurity (FW = 293) is a heavy component and appears in the bottom product. Based on the difference in formula weight (albeit slight), this is counterintuitive. (iPr)Sn(NMe2)3 has an FW of 294.0. The desired (iPr)Sn(NMe2)3 compound with both light and heavy impurities is the middle product. Thus, a forecut is required in the batch distillation process to remove the tetra impurities. Continuous distillation requires two columns to recover (iPr)Sn(NMe2)3.

[0135] The following conditions were utilized: a. Condenser temperature = 90 °C b. Reflux ratio = 40 - 50 c. Pressure = 10 Torr d. Pot temperature = 111.1 - 111.9 °C

[0136] The compositions measured in the systems shown in the following Table 3 and Table 4 indicate the effect of increasing pot temperature on the degree of purification achieved. In Table 3 and Table 4, the tin compounds (3), (6), and (7) have the structures shown above.

[0137] At 110 °C, tetraamido tin (6) was not observed in either the receiver or the samples collected from the reflux returning to the column. At higher pot temperatures, the amount of tetraamido tin in the receiver and reflux samples increased. None of the pot samples showed tetraamido tin. This indicates that this compound is a low-boiling limit component, even if it is slightly heavier (by only 1 amu) than iPrSn(NMe2)3.

[0138]

Table 3

[0139]

Table 4

Example

[0140] Synthesis of Methyltris(dimethylamino)tin Anhydrous hexane (970.5 g, 11.26 mol) and n-BuLi (429.8 g, 1.61 mol, 2.4 M solution in hexane) were charged into a 5 L reactor. Dimethylamine (145.1 g, 3.22 mol) was added below the surface at about 0 - 10 °C. While warming to room temperature, the reaction mixture was stirred for an additional 4 hours, and then methyltrichlorotin (125.0 g, 0.52 mol) in toluene (125 g, 1.36 mol) was added dropwise at about 0 - 10 °C. The resulting mixture was warmed to room temperature over 4 hours and stirred at room temperature for an additional 4 hours. The reaction mixture was filtered through a sparkler to remove the LiCl by-product. The salt was washed with anhydrous hexane (2 × 100 mL). The solvent was removed under reduced pressure, and the residue was distilled under reduced pressure (34 - 35 °C, 1 torr) using a 316 SS Pro-Pak column equipped with an amber distillation head. The product was collected as a colorless transparent liquid in an amber glass receiver. Yield: 74.0 g (53.4%), 119 Sn NMR (149.2 MHz; neat): δ -16.78. 1 H NMR (400 MHz; C6D6): δ 2.79 (s, 18H, NCH3), δ 0.12 (s, 3H, CH3). Purity( 119 Sn NMR): 99.5% product, 0.5% dimethylstannamide. 119 Sn and 1 The H NMR spectra are shown in Figures 4 and 5.

Example

[0141] Synthesis of Isopropyltris(dimethylamino)tin Anhydrous hexane (6.3 kg, 73 mol) and n-BuLi (3.1 kg, 11.75 mol, 2.4 M solution in hexane) were charged into a 22 L 316 stainless steel reactor equipped with a banana-shaped blade (CG-16). While stirring at about 200 rpm, dimethylamine (1.1 kg, 23.5 mol) was added below the surface at about 0 - 10 °C. While warming to room temperature, the reaction mixture was stirred for an additional 4 hours, and then isopropyltrichlorostannane (1.0 kg, 3.73 mol) was added dropwise at about 0 - 10 °C. The resulting mixture was warmed to room temperature over 4 hours and stirred at room temperature for an additional 4 hours. The reaction mixture was filtered through a sparkler to remove the LiCl by-product. This salt was rinsed with anhydrous hexane (2 × 500 mL). The solvent was removed under reduced pressure. To further purify the product, the residue was distilled under reduced pressure using a 316 SS Pro-Pak column equipped with an amber distillation head (49 - 53 °C, 0.5 torr). The product was collected as a colorless transparent liquid in an amber glass receiver. Yield: 803 g (73.3%). 119 Sn NMR (149.2 MHz; neat): δ -64.85. 1 H NMR (400 MHz; C6D6): δ 2.85 (s, 18H, NCH3), δ 1.61 (m, 1H, methine), δ 1.27 (d, 6H, CH3). Purity ( 119 Sn NMR): 99.8% product, 0.2% diisopropylstannane diamide (7), 0.0% compound (5)( 119 Sn NMR (149.2 MHz; neat): δ -84 ppm). 119 Sn and 1 H NMR spectra are shown in Figures 6 and 7. The product was stored in a 316 SS ampoule at 25 °C without exposure to light.

Example

[0142] Synthesis of Isopropyltris(dimethylamino)tin Anhydrous THF (1.0 kg, 13.86 mol) and n-BuLi (1.2 kg, 4.61 mol, 2.4 M solution in hexane) were charged into an amber glass reactor. Dimethylamine (0.38 kg, 8.32 mol) was added below the surface at about 0 - 10 °C. While warming to room temperature, the reaction mixture was stirred for an additional 4 hours, and then isopropyltrichlorostannane (0.4 kg, 1.49 mol) was added dropwise at about 0 - 10 °C. The resulting mixture was warmed to room temperature over 4 hours and stirred at room temperature for an additional 4 hours. The reaction mixture was filtered through a sparkler to remove the LiCl by-product. This salt was washed with anhydrous hexane (2 × 200 mL). The solvent was removed under reduced pressure. To further purify the product, the residue was distilled under reduced pressure (49 - 53 °C, 0.5 torr) using a 316 SS Pro-Pak column equipped with an amber distillation head. The product was collected as a colorless transparent liquid in an amber glass receiver. Yield: 305 g (69.5%). 119 Sn NMR (149.2 MHz; neat): δ -64.85. 1 H NMR (400 MHz; C6D6): δ 2.85 (s, 18H, NCH3), δ 1.61 (m, 1H, methine), δ 1.27 (d, 6H, CH3). Purity ( 119 Sn NMR): 99.57% product, 0.43% diisopropyltin diamide. 119 The Sn NMR spectrum is shown in Figure 8.

Example

[0143] Effect of Temperature on the Synthesis of Isopropyltris(dimethylamino)tin In three parallel experiments, anhydrous hexane (217.1 g, 2.52 mol) and n-BuLi (186.6 g, 0.63 mol, 2.4 M solution in hexane) were charged into a 5 L reactor. Dimethylamine (56.8 g, 1.26 mol) was added below the surface at about 0 - 10 °C. While warming to room temperature, the reaction mixture was stirred for an additional 4 hours, and then isopropyltrichlorostannane (53.6 g, 0.2 mol) was added dropwise at about -78 °C, about -40 °C, or about 0 °C. The resulting mixture was warmed to room temperature over 4 hours and stirred at room temperature for an additional 4 hours. The reaction mixture was filtered through a sparkler to remove the LiCl byproduct. This salt was rinsed with anhydrous hexane (2 × 100 mL). The solvent was removed under reduced pressure. The relative amounts of the desired product (3) and byproduct (7) are shown in Table 5, and the 119 Sn NMR spectra for the reactants at about 0 °C, about -40 °C, and about -78 °C are shown in Figures 9, 10, and 11, respectively. It can be observed that the highest purity was obtained at about -78 °C and about 0 °C, and the lowest purity was obtained at about -40 °C. Furthermore, among the three temperatures tested, the ideal temperature for the reaction is about 0 °C.

[0144]

Table 5

Example

[0145] Effect of Photolysis on the Synthesis of Isopropyltris(dimethylamino)tin Anhydrous hexane (120.6 g, 1.40 mol) and n-BuLi (127 ml, 0.35 mol, 186.6 g, 2.76 M solution in hexane) were charged into a 5 L glass reactor without a sunshade to protect from light. Dimethylamine (48 ml, 0.70 mol) was added below the surface at about 0 - 10 °C. The reaction mixture was stirred for an additional 4 hours, and then isopropyltrichlorostannane (30.4 g, 0.11 mol) was added dropwise at about 0 °C. The resulting mixture was warmed to room temperature over 4 hours and stirred at room temperature for an additional 16 hours. The reaction mixture was filtered through a funnel to remove the LiCl by-product. The salt was rinsed with anhydrous hexane (100 mL). The solvent was removed under reduced pressure in a 1 L glass flask without a sunshade. The relative amounts of the desired product (3) and by-products (7) and (4) were, 119 determined by Sn NMR as follows: product (3): 98.0 mol%, impurity (7): 0.4 mol%, compound (5): 1.6 mol%.

[0146] It is recognized by those skilled in the art that modifications can be made to the embodiments described above without departing from the broad inventive concept. Accordingly, it is to be understood that the present invention is not limited to the specific embodiments disclosed and is intended to cover variations within the spirit and scope of the invention as defined by the appended claims.

Claims

1. Formula (1): R 1 Sn(NR 2 2 ) 3 (1) (wherein R 1 is selected from R A , R B , and R C , and R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, R C is a tertiary alkyl group having about 3 to 10 carbon atoms, each R 2 is independently an alkyl group having about 1 to 10 carbon atoms) having, and having a purity of at least about 99 mol% of a monoalkyltin triamide compound, R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) has a content of less than about 1 mol% of a monoalkyltin triamide compound.

2. Formula (2): R 1 2 Sn(NR 2 2 ) 2 (2) having a content of less than about 1 mol% of dialkylbis(dialkylamino)tin, the monoalkyltin triamide compound according to Claim 1.

3. The total content of tetrakis(dialkylamino)tin is less than about 1 mol%, the monoalkyltin triamide compound according to Claim 1 or 2.

4. The monoalkyltin triamide compound according to any one of claims 1 to 3, wherein the content of tetraalkyltin is less than about 1 mol%.

5. The monoalkyltin triamide compound according to any one of claims 1 to 4, wherein the color is substantially colorless.

6. The monoalkyltin triamide compound according to claim 5, wherein the APHA is less than about 20.

7. R 1 is an isopropyl group, R 2 is a methyl group, and the compound has the formula (3): 【Chemical Formula 1】 The monoalkyltin triamide compound according to any one of claims 1 to 6, having

8. The monoalkyltin triamide compound according to claim 7, wherein the content of diisopropylbis(dimethylamino)tin is less than about 1 mol%.

9. The monoalkyltin triamide compound according to claim 5, wherein the total content of tetrakis(dimethylamino)tin is less than about 1 mol%.

10. R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 The monoalkyltin triamide compound according to any one of claims 1 to 9, wherein the content of is less than about 0.05 mol%.

11. Formula (1a): R 1 Sn(NR 2 2 ) 3 (1a) (wherein R 1 is selected from R A and R B , and R A is a primary alkyl group having from about 1 to 10 carbon atoms, and R B is a secondary alkyl group having from about 3 to 10 carbon atoms, each R 2 is, independently, an alkyl group having from about 1 to 10 carbon atoms) and having, a method for synthesizing a monoalkyltin triamide compound having a purity of at least about 85 mol%, (a) lithiating a solution containing dimethylamine and a first solvent to obtain a lithium dimethylamide solution having a concentration of up to about 10% by weight; (b) adding a solution containing alkyltrichlorotin and a second solvent, wherein the amount of lithium dimethylamide in the solution is at least about 3.09 equivalents relative to the amount of alkyltrichlorotin; (c) removing the LiCl salt product by filtration; and (d) removing the first solvent and the second solvent under vacuum to obtain a crude product containing a monoalkyltin triamide having formula (1a) The method comprising.

12. The method according to claim 11, wherein the compound having formula (1a) has a purity of at least about 99 mol%.

13. The compound having formula (1a) has less than about 1 mol% of R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) and contains, the method according to claim 11 or 12.

14. The compound having formula (1a) has less than about 0.05 mol% of R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2The method according to claim 13, comprising **Claim 15** The method according to any one of claims 11 to 14, wherein step (b) is carried out at about -78 °C to about 40 °C. **Claim 16** The method according to claim 15, wherein step (b) is carried out at about 0 °C to about 10 °C. **Claim 17** The method according to any one of claims 11 to 16, wherein the first solvent and the second solvent are each independently selected from the group consisting of hydrocarbon solvents, aromatic solvents, and ether solvents. **Claim 18** The method according to any one of claims 11 to 17, wherein steps (a) to (d) are carried out substantially without exposure to light. **Claim 19** The method according to any one of claims 11 to 18, wherein steps (a) and (b) are carried out in a stainless steel container. **Claim 20** The method according to claim 11, further comprising a step of distilling the compound having the formula (1a). **Claim 21** The distillation comprises a step of distilling the crude product having the formula (1a) at about 1 torr, a step of discarding any distillate before the boiling point of the monoalkyltriamide having the formula (1a), and a step of collecting the distillate obtained at the boiling point of the monoalkylstannic triamide having the formula (1a) to obtain a product containing at least about 99 mol% of the monoalkylstannic triamide having the formula (1a). The method according to claim 20. **Claim 22** The method comprises a step of performing fractional distillation using an operating pressure of about 0.1 to about 50 torr and a pot temperature of about 50 to about 120 °C, wherein the purified monoalkylstannic triamide compound having the formula (1a) contains less than about 0.1 mol% of the dialkylbis(dialkylamino)stannane compound having the formula (2). The method according to claim 20 or 21. **Claim 23** The method according to any one of claims 20 to 22, comprising a step of performing distillation without substantially exposing to light.

24. The method according to any one of claims 20 to 23, comprising a step of performing distillation using a condenser temperature in the range of about 1 to about 10 °C which is the dew point of a monoalkyltin triamide compound having formula (1a) at an operating pressure and a reflux ratio of about 10 to about 100.

25. The method according to any one of claims 20 to 24, wherein the distillation is carried out using a stainless steel column filled with a stainless steel packing material.

26. The method according to any one of claims 20 to 25, wherein the distillation is carried out in a device containing glass with light being shielded.

27. Formula (1): R 1 Sn(NR 2 2 ) 3 (1) (wherein R 1 is selected from R A , R B , and R C , R A is a primary alkyl group having about 1 to 10 carbon atoms, R B is a secondary alkyl group having about 3 to 10 carbon atoms, R C is a tertiary alkyl group having about 3 to 10 carbon atoms, each R 2 is independently an alkyl group having about 1 to 10 carbon atoms) A method for storing a sample of a monoalkyltin triamide compound having formula (1) and having a purity of at least about 99 mol%, comprising a step of storing a sample of a monoalkyltin triamide compound having formula (1) at a temperature of less than about 30 °C without substantially exposing to light .

28. The method according to claim 27, wherein a sample of the monoalkyltin triamide compound having the formula (1) is stored for about 3 days to about 1 year.

29. The method according to claim 27 or 28, wherein substantially no decomposition occurs in a sample of the monoalkyltin triamide after a storage period of about 3 days to about 1 year.

30. R in a sample of the monoalkyltin triamide having the formula (1) 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) has a content of less than about 1 mol%, the method according to any one of claims 27 to 29.

31. R in a sample of the monoalkyltin triamide having the formula (1) 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) has a content of less than about 0.05 mol%, the method according to claim 30.

32. R 1 is selected from R A and R B , and (a) lithiating a solution containing dimethylamine and a first solvent to obtain a lithium dimethylamide solution having a concentration of up to about 10% by mass; (b) adding a solution containing alkyltrichlorotin and a second solvent, wherein the amount of lithium dimethylamide is at least about 3.09 equivalents relative to the amount of alkyltrichlorotin; (c) removing the LiCl salt product by filtration, and (d) removing the first solvent and the second solvent under vacuum to obtain a crude product containing the monoalkyltin triamide having the formula (1) The monoalkyltin triamide compound having the formula (1) according to any one of claims 1 to 10, produced by a method comprising

33. The method according to claim 32, wherein step (b) is carried out at about -78°C to 40°C.

34. The method according to claim 33, wherein step (b) is carried out at about 0°C to about 10°C.

35. The method according to any one of claims 32 to 34, wherein the first solvent and the second solvent are each independently selected from the group consisting of a hydrocarbon solvent, an aromatic solvent, and an ether solvent.

36. The method according to any one of claims 32 to 35, wherein steps (a) to (d) are carried out substantially without exposure to light.

37. The method according to any one of claims 32 to 36, wherein steps (a) and (b) are carried out in a stainless steel container.

38. The method according to any one of claims 32 to 37, further comprising a step of distilling the compound having the formula (1).

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