High-purity alkyl tin compound and preparation method thereof

Abstract

Monoalkyltin triamino compounds having a purity of at least about 99 mol% and having the chemical formula RSn (NMe2) 3 are described. R1 is selected from RA, RB and RC; rA is a primary alkyl group having about 1 to 10 carbon atoms, RB is a secondary alkyl group having about 3 to 10 carbon atoms, and RC is a tertiary alkyl group having about 3 to 10 carbon atoms; each R2 is independently an alkyl group having from about 1 to 10 carbon atoms; the content of R1Sn (NR22) 2 (N (R2) CH2NR22) is less than about 1 mol%. Methods of synthesizing, purifying and storing these compounds are also provided. The monoalkyltin compounds can be used to form high resolution EUV lithography patterning precursors and have attractive force due to their high purity and minimum concentrations of dialkyltin and other tin impurities.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to co-pending U.S. Provisional Application No. 63,348,173, filed on June 2, 2022, the disclosure of which is incorporated herein by reference. Background of the Invention

[0004] As semiconductor manufacturing continues to advance, feature sizes continue to shrink, driving the need for new processing methods. Certain organotin compounds have proven useful for depositing tin oxide hydroxide coatings in applications such as extreme ultraviolet (EUV) lithography. For example, alkyltin compounds provide radiation-sensitive Sn-C bonds that can be used in lithographically patterned structures.

[0005] Materials used in microelectronics manufacturing need to be extremely pure, with strict limits on organic contaminants (such as reaction byproducts), metal contaminants, and particle contaminants. Purity requirements are often stringent, especially for photolithography applications, where the chemicals come into contact with semiconductor substrates. Organometallic impurities in compounds such as diisopropylbis(dimethylamino)tin, 3(iPr) 2 Sn(NMe 2 ) 2 , which can affect the properties of the resulting film. The exact purity target is determined by various factors, including performance specifications, but a typical minimum purity target is 3N+. Residual metals present in the chemistry can deposit on the semiconductor substrate and degrade the electrical performance of the fabricated device. Typical specifications for metals are less than 10 ppb for a single metal and no more than ~100 ppb for total metals.

[0006] The processing and properties of semiconductor materials may also be sensitive to dialkyltin contaminants. 2 Sn(NMe 2 ) 2 , where R is an alkyl group, is a source of off-gassing after vapor deposition or spin coating processes because the density of oxostannate cluster films is lower when the film contains a dialkyl group. Proper control of dialkyltin contaminants is required for the production of microelectronics using EUV lithography. The high purity required for the manufacturing process of monoalkyltin precursors becomes a challenge. Generally speaking, the synthesis of monoalkyltin triamides has previously used alkyltin trichlorides reacting with lithium dimethylamide reagents or subsequently using lithium / Grignard reagents (alkylating agents) to convert the tin tetraamide to the desired triamide.

[0007] In the preparation of primary alkyltin triaminos (such as methyl and long alkyl triaminos), the Kocheshkov-like antidisproportionation reaction in Scheme (I) shown below and the disproportionation reaction in Scheme (II) are two major challenges in the purification process, and the dialkyltin content does not exceed 1% after purification. Studies have shown that below -78°C, the occurrence of antidisproportionation reactions is independent of the reaction temperature. In fact, it has been found that lower temperatures slow down the substitution reaction, thereby increasing the risk of antidisproportionation.

[0008]

[0009] The preparation of monoalkyltin triamides can be accomplished by two different known synthetic routes. When the alkyl group contains primary and / or secondary groups, such as methyltri(dimethyl)tin (MeSn(NMe 2 ) 3 ) or isopropyltri(dimethyl)tin (iPrSn(NMe 2 ) 3 ), dimethyl lithium and alkyl tin trichloride (amination) can be used for synthesis according to the method of Lorberth (Journal of Organometallic Chemistry; 16 (2), 235-48 (1969)); see also Jones and Lappert (Organometal. Chem. Rev.; 1, 67 (1966)), as shown in Scheme (III). However, this reaction usually produces a large amount of dialkyl tin and other tin impurities.

[0010] RSnCl3+LiN(Me2)3RSn(NMe2)3(III)

[0011] Alternatively, when the alkyl group contains a tertiary alkyl group, such as tert-butyltri(dimethyl)tin (t-BuSn(NMe2)3), an alkylating agent must be used to synthesize the compound in order to convert the tin tetraamino group by controlling the stoichiometry, according to the method reported by Hanssgen et al. (Journal of Organometallic Chemistry, 293(2), 191-5(1985)), as shown in Scheme (IV).

[0012] RLi+Sn(NMe2)4RSn(NMe2)3((IV)

[0013] The reaction of Scheme (IV) using an alkylating agent and a tetraamino group is not effective for preparing primary and secondary monoalkyltin triamino groups. Instead, even with the correct stoichiometry, the use of a primary alkylating agent will convert the tin tetraamino group to a trialkyltin amino group and unreacted tetraamino groups. Secondary alkylating agents will also convert the tin tetraamino group to a polyalkyltin compound.

[0014] When the alkyl group in the monoalkyltin triamide is a tertiary alkyl group such as t-BuSnCl 3 Hanssgen et al. also reported that the compound decomposes rapidly at room temperature to produce SnCl 2 Therefore, tertiary monoalkyltin triamides cannot be prepared by synthesis using dimethyllithium and alkyltin trichloride.

[0015] Distillation is a well-established technique for separating substances in a mixture based on their relative volatility. The specific implementation of the distillation process depends on the nature, composition, and amount of the mixture to be separated. Distillation can and has been used to reduce metal contamination in a variety of materials, including organometallic compounds.

[0016] For example, U.S. Patent Application Publication No. 2019 / 0337969 describes organometallic tin compounds with low concentrations of metal impurities using a multi-stage distillation process, compared to processes typically used for desalination. U.S. Patent Application Publication No. 2020 / 0239498 describes the purification of monoalkyltin trialkoxy and monoalkyltin triamide using fractionation and / or ultrafiltration to remove metal impurities and fine particles. Methods for removing metal impurities from similar compounds are also described in U.S. Patent Application Publication No. 2020 / 0241413.

[0017] U.S. Patent No. 10,787,466 and U.S. Patent No. 10,732,505 describe organotin hydroxides, alkoxides and amides with low purity. However, only the tert-butyl analogs have extremely low impurity levels.

[0018] U.S. Patent No. 8,901,335 describes the purification of a series of organometallic compounds using a stripping column and a gas stream; impurities that are more volatile than the organometallic compound are removed and the metal impurity content is reduced to a specified level. U.S. Patent No. 11,156,915 relates to the purification of compounds sensitive to actinic rays or radiation, including tin compounds, using filtration to remove particulate matter. Finally, U.S. Patent No. 5,274,149 teaches a method for preparing alkylarsine compounds, which method includes a distillation step and is taught to be substantially free of metal or oxygen-containing impurities.

[0019] The ability to prepare and isolate alkyl tin compounds with the extremely high purity levels required is very attractive for applications in the microelectronics industry.

[0020] Brief description of the invention

[0021] In one aspect of the present invention, there is provided a monoalkyltin tris compound having the formula (1) and having a purity of at least about 99 mol %:

[0022] R1 Sn(NR 2 2 ) 3 (1)

[0023] Where R 1 Selected from R A , R B and R C ;

[0024] 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;

[0025] Each R 2 is independently an alkyl group having from about 1 to 10 carbon atoms; and

[0026] Where R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) content is less than about 1 mol%.

[0027] In another aspect of the present disclosure, a method for synthesizing a monoalkyltin tris compound having formula (1a) and a purity of at least about 85 mol% is provided:

[0028] R 1 Sn(NR 2 2 ) 3 (1a)

[0029] Where R 1 Selected from R A and R B ;

[0030] 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

[0031] Each R 2 is independently an alkyl group having about 1 to 10 carbon atoms; the method comprising:

[0032] (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %;

[0033] (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride;

[0034] (c) removing the LiCl salt product by filtration; and

[0035] (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltintriamine having the formula (1a).

[0036] In another aspect of the present disclosure, a method for storing a sample of a monoalkyltin triamino compound having formula (1) and a purity of at least about 99 mol % is provided:

[0037] R 1 Sn(NR 2 2 ) 3 (1)

[0038] Where R 1 Selected from R A , R B and R C ;

[0039] 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;

[0040] Each R 2 is independently an alkyl group having about 1 to 10 carbon atoms;

[0041] The method comprises storing a sample of a monoalkyltin triamino compound having formula (1) without exposure to light and at a temperature of less than about 30°C.

[0042] Advantageous developments of the invention are specified in the dependent claims and can be implemented individually or in combination.

[0043] In summary, the following particularly preferred embodiments are proposed within the scope of the present invention:

[0044] Embodiment 1: A monoalkyltin triamino compound having formula (1) and a purity of at least about 99 mol%:

[0045] R 1 Sn(NR 2 2 ) 3 (1)

[0046] Where R 1 Selected from R A , RB and R C ;

[0047] 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;

[0048] Each R 2 is independently an alkyl group having from about 1 to 10 carbon atoms; and

[0049] Where R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) content is less than about 1 mol%.

[0050] Embodiment 2: The monoalkyltin triamino compound according to Embodiment 1, wherein the content of dialkylbis(dialkylamino)tin having formula (2) is less than about 1 mol%

[0051] R 1 2 Sn(NR 2 2 ) 2 (2).

[0052] Embodiment 3: The monoalkyltin triamino compound according to Embodiment 1 or 2, wherein the total content of tetrakis(dialkylamino)tin is less than about 1 mol%.

[0053] Embodiment 4: The monoalkyltin triamino compound according to any of the preceding embodiments, wherein the content of tetraalkyltin is less than about 1 mol%.

[0054] Embodiment 5: The monoalkyltin triamino compound according to any of the preceding embodiments, wherein the color is substantially colorless.

[0055] Embodiment 6: The monoalkyltin triamino compound of Embodiment 5, wherein the APHA is less than about 20.

[0056] Embodiment 7: A monoalkyltin triamino compound according to any one of the preceding embodiments, wherein R 1 is isopropyl, R 2 is a methyl group, and the compound has the formula (3):

[0057]

[0058] Embodiment 8: The monoalkyltin triamino compound according to Embodiment 7, wherein the content of diisopropylbis(dimethylamino)tin is less than about 1 mol%.

[0059] Embodiment 9: The monoalkyltin triamino compound according to Embodiment 8, wherein the total content of tetrakis(dimethylamino)tin is less than about 1 mol%.

[0060] Embodiment 10: A monoalkyltin triamino compound according to any one of the preceding embodiments, wherein R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) content is less than about 0.05 mol%.

[0061] Embodiment 11: A method for synthesizing a monoalkyltin triamino compound having formula (1a) and a purity of at least about 85 mol%:

[0062] R 1 Sn(NR 2 2 ) 3 (1a)

[0063] Where R 1 Selected from R A and R B ;

[0064] 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

[0065] Each R 2 is independently an alkyl group having about 1 to 10 carbon atoms; the method comprising:

[0066] (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %;

[0067] (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride;

[0068] (c) removing the LiCl salt product by filtration; and

[0069] (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltintriamine having the formula (1a).

[0070] Embodiment 12: The method of Embodiment 11, wherein the compound having formula (1a) has a purity of at least about 99 mol%.

[0071] Embodiment 13: The method according to Embodiment 11 or 12, wherein the compound of formula (1a) contains less than about 1 mol% of R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ).

[0072] Embodiment 14: The method according to Embodiment 13, wherein the compound having formula (1a) contains less than about 0.05 mol% of R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ).

[0073] Embodiment 15: The method according to any one of Embodiments 11-14, wherein step (b) is carried out at about -78°C to 40°C.

[0074] Embodiment 16: The method of Embodiment 15, wherein step (b) is performed at about 0°C to about 10°C.

[0075] Embodiment 17: The method according to any one of Embodiments 11-16, 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.

[0076] Embodiment 18: The method of any one of Embodiments 11-17, wherein steps (a) to (d) are performed substantially without exposure to light.

[0077] Embodiment 19: The method according to any one of Embodiments 11-18, wherein steps (a) and (b) are performed in a stainless steel container.

[0078] Embodiment 20: The method according to Embodiment 11, further comprising distilling the compound having formula (1a).

[0079] Embodiment 21: A method according to Embodiment 20, wherein the distillation includes distilling the crude product having formula (1a) at about 1 torr, discarding any distillate before the boiling point of the monoalkyltriamine having formula (1a), and collecting the distillate obtained at the boiling point of the monoalkyltintriamine having formula (1a) to obtain a product containing at least about 99 mol% of the monoalkyltintriamine having formula (1a).

[0080] Embodiment 22: The method according to Embodiment 20 or 21, comprising fractionating using an operating pressure of about 0.1 to 50 Torr and a pot temperature of about 50 to 120°C, wherein the purified monoalkyltin triamino compound having formula (1a) contains less than about 0.1 mol% of the dialkylbis(dialkylamino)tin compound having formula (2).

[0081] Embodiment 23: The method of any one of Embodiments 20 to 22, comprising performing the distillation in the absence of substantial exposure to light.

[0082] Embodiment 24: The method according to any one of Embodiments 20 to 23, comprising distilling at an operating pressure and a reflux ratio of about 10 to 100 using a condenser temperature in the range of about 1 to 10°C of the dew point of the monoalkyltin triamide having formula (1a).

[0083] Embodiment 25: The method according to any one of Embodiments 20 to 24, wherein the distillation is performed using a stainless steel column filled with stainless steel packing.

[0084] Embodiment 26: The method of any one of Embodiments 20 to 25, wherein the distillation is performed in a light-shielding device comprising glass.

[0085] Embodiment 27: A method for storing a sample of a monoalkyltin triamino compound having formula (1) and a purity of at least about 99 mol %:

[0086] R 1 Sn(NR 2 2 ) 3 (1)

[0087] Where R 1 Selected from R A , R B and R C ;

[0088] 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;

[0089] Each R 2 is independently an alkyl group having about 1 to 10 carbon atoms;

[0090] The method comprises storing a sample of a monoalkyltin triamide compound having formula (1) substantially without exposure to light and at a temperature of less than about 30°C.

[0091] Embodiment 28: The method of Embodiment 27, wherein the sample of the monoalkyltin triamino compound having formula (1) is stored for about three days to about one year.

[0092] Embodiment 29: The method of Embodiment 27 or 28, wherein the monoalkyltintriamide sample does not substantially decompose after storage for about three days to about one year.

[0093] Embodiment 30: A method according to any one of embodiments 27 to 29, wherein R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) content is less than about 1 mol%.

[0094] Embodiment 31: The method according to embodiment 30, wherein R 1 Sn(NR 2 2) 2 (N(R 2 )CH 2 NR 2 2 ) content is less than about 0.05 mol%.

[0095] Embodiment 32: A monoalkyltin triamino compound having formula (1) according to any one of Embodiments 1 to 10, wherein R 1 Selected from R A and R B , the compound is prepared by a method comprising the following steps:

[0096] (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %;

[0097] (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride;

[0098] (c) removing the LiCl salt product by filtration; and

[0099] (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltintriamine group having the formula (1).

[0100] Embodiment 33: The method according to Embodiment 32, wherein step (b) is carried out at about -78°C to about 40°C.

[0101] Embodiment 34: The method of Embodiment 33, wherein step (b) is performed at about 0°C to about 10°C.

[0102] Embodiment 35: The method according to any one of Embodiments 32-34, 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.

[0103] Embodiment 36: The method of any one of Embodiments 32-35, wherein steps (a) to (d) are performed substantially without exposure to light.

[0104] Embodiment 37: The method according to any one of Embodiments 32-36, wherein steps (a) and (b) are performed in a stainless steel container.

[0105] Embodiment 38: The method according to any one of Embodiments 32-37, further comprising distilling the compound having formula (1).

[0106] BRIEF DESCRIPTION OF THE DRAWINGS

[0107] The above summary and 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, there are shown in the accompanying drawings presently preferred embodiments. However, it should be understood that the invention is not limited to the precise arrangements and instrumentalities shown.

[0108] In the attached picture:

[0109] Figure 1 It is used to describe the iPrSn(NMe 2 ) 3 (A) and iPr 2 Sn(NMe 2 ) 2 (B) boiling point diagram;

[0110] Figure 2 Is the description of iPrSn(NMe 2 ) 3 Plot of light decomposition over time;

[0111] Figure 3 Is the description of iPrSn(NMe2 ) 2 (NMeCH 2 NMe 2 ) 119 Sn NMR (pure) spectrum;

[0112] Figure 4 It is methyl tris(dimethylamino)tin 1 H NMR (C 6 D 6 ) spectrum;

[0113] Figure 5 It is methyl tris(dimethylamino)tin 119 Sn NMR (pure) spectrum;

[0114] Figure 6 It is isopropyl tri(dimethylamino)tin 1 H NMR (C 6 D 6 ) spectrum;

[0115] Figure 7 It is isopropyl tri(dimethylamino)tin 119 Sn NMR (pure) spectrum;

[0116] Figure 8 Isopropyl tris(dimethylamino)tin is synthesized in THF solution 119 Sn NMR (pure) spectrum;

[0117] Fig. 9 It is synthesized at about 0°C. 119 Sn NMR (pure) spectrum;

[0118] Fig.10 It is synthesized at about -40°C. 119 Sn NMR (neat) spectrum; and

[0119] Fig.11 It is synthesized at about -78°C. 119 Sn NMR (pure) spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0121] According to one aspect of the present invention, there is provided a monoalkyltin triamino compound represented by formula (1) having a purity of at least about 99 mol%. In a preferred embodiment, the compound having formula (1) contains no more than about 1 mol% of a dialkylbis(dialkylamino)tin compound having formula (2) relative to the total amount of tin.

[0122] R 1 Sn(NR2 2 ) 3 (1)

[0123] R 1 2 Sn(NR 2 2 ) 3 (2)

[0124] In formulas (1) and (2), R 1 Selected from R A , R B and R C . R A R is a primary alkyl group having about 1 to 10 carbon atoms, preferably about 1 to about 5 carbon atoms, including methyl, ethyl, n-propyl, n-butyl, n-pentyl, etc.; preferably methyl or ethyl. B It is a secondary alkyl group (straight chain alkyl group or cycloalkyl group) having about 3 to 10 carbon atoms, more preferably about 3 to about 5 carbon atoms, such as but not limited to isopropyl, isobutyl, sec-butyl, cyclohexyl, cyclopentyl, cyclobutyl, cyclopropyl, isopentyl, sec-pentyl, etc.; isopropyl and cyclopentyl are currently preferred. C It is a tertiary alkyl group having about 3 to 10 carbon atoms, such as tert-pentyl, 3-ethyl-3-pentyl, methyl-3-pentyl, methylcyclopentyl, methylcyclohexyl and preferably tert-butyl.

[0125] Each R 2 Independently, it is an alkyl group having about 1 to 10 carbon atoms, preferably about 1 to 5 carbon atoms, including methyl, ethyl, propyl, butyl, pentyl, etc.; preferably methyl or ethyl.

[0126] In the compound having formula (1), R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ), also referred to herein as compound (4), is preferably present in an amount of less than about 1 mol%, preferably even lower, as described below. In addition, the amount of the compound of formula (2) is preferably less than about 1 mol%, preferably even lower, as described below.

[0127] All numerical ranges expressed in the present disclosure include all values ​​within the range, including fractions and decimals. Therefore, the content of the compound having formula (4) and (2) is 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 ...5 mol%, less than about 0.05 mol%, less than about 0.05 mol%, less than about 0.05 mol%, less than about 0.05 mol 119 Sn NMR is not detectable, that is, in some embodiments, compounds having formulae (2) and (4) are not detectable in a sample of the compound of formula (1).

[0128] If the content of the compound of formula (2) is too high, crosslinking and toughness will be reduced when the material is used in EUV lithography resists. In addition, when the photoresist is exposed to extreme ultraviolet radiation, the compound of formula (2) can cause outgassing, which in extreme cases can lead to degradation of very expensive multi-layer coated optics. As described below, by using carefully controlled reaction and distillation conditions, the dialkyltin impurity level can be reduced to 119 Sn is not detectable at levels detected by NMR. However, for industrial scale reactions, such as product scales greater than 0.5 kg, it is usually sufficient and feasible to control the impurity limit to less than about 0.3 mol%, more preferably less than about 0.1 mol%, based on stable production and economic considerations.

[0129] In a preferred embodiment, R' is isopropyl, R 2 is methyl, the compound having formula (1) is (iPr)Sn(NMe 2 ) 3 (Formula (3)), wherein the dialkyltin impurity is (iPr) 2 Sn(NMe 2 ) 2 In some embodiments, when the compound has formula (3), it has a purity of at least about 99 mol% and contains no more than about 1 mol% (iPr) 2 Sn(NMe 2 ) 2 .

[0130]

[0131] In some embodiments, the content of tetrakis(dialkylamino)tin (e.g., tetrakis(dimethylaminotin)) in the monoalkyltin triamino compound of formula (1) is less than about 1 mol%. In some embodiments, the content of tetrakis(dialkylamino)tin (e.g., tetrakis(dimethylaminotin)) in the monoalkyltin triamino compound of formula (1) is less than about 1 mol%. 2 ) 3 Tetra(isopropyl)tin) in the mixture is less than about 1 mol%. Tetra(dialkylamino)tin and tetraalkyltin (e.g., (iPr)Sn(NMe 2 ) 3 The content of tetrakis(dimethylamino)tin or tetrakis(isopropyl)tin) in the above-mentioned compound is 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%, about 0.04 mol%, less than about 0.03 mol%, less than about 0.02 mol%, less than about 0.01 mol%, or less than about 0.02 mol%. 119 Sn NMR was not detectable, that is, these compounds were not detected in the sample of the compound of formula (1).

[0132] If the content of tetrakis(dimethylamino)tin and tetraalkyltin is too high, defects may occur when the material is used for EUV lithography resists due to the boiling points and molecular weights of these compounds. As described below, the impurity levels of these compounds can be reduced to 119 Sn is not detectable at NMR levels. However, for industrial scale reactions, such as greater than 0.5 kg product scale, it may be feasible to control the impurity limit to less than about 0.3 mol%, more preferably less than about 0.1 mol%, based on stable production and economic considerations.

[0133] In some embodiments, R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ), also referred to herein as compound (4), has a total content of less than about 1 mol %, and may be a compound having the formula R A Sn(NMe 2 ) 2 (NMeCH 2 NMe 2 ) or R B (NMe 2 ) 2(NMeCH 2 NMe 2 ) 2 When the compound having formula (4) is iPrSn(NMe 2 ) 2 (NMeCH 2 NMe 2 )(Formula (5)), when 119 The chemical shift in the Sn NMR spectrum is about -84 ppm: 119 Sn NMR (223.8MHz; C6D6): δ-84ppm. 1 H NMR (600MHz; C6D6): δ3.37(s,2H,CH 2 ),2.89(s,3H,Sn-NMe),2.86(s,12H,Sn-(NMe 2 ) 2 ),2.15(s,6H,NMe 2 ),1.68(m,1H,iPr),1.33(s,6H,iPr).

[0134]

[0135] 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.

[0136] As described above, by using strictly controlled reaction and distillation conditions, the content of the compound of formula (4) or (5) can be reduced to less than about 0.1 mol%, such as less than about 0.05 mol%. However, for industrial-scale reactions, such as product scales greater than 0.5 kg, it is usually feasible to control the impurity limit to less than about 0.3 mol%, preferably less than about 0.1 mol%, based on stable production and economic considerations.

[0137] In some embodiments, the monoalkyltin triamide compound of formula (1) is substantially colorless. In some embodiments, the monoalkyltin triamide compound of formula (1) has an APHA color of less than about 20. During the distillation process, the APHA color of the composition containing the tin compound can be controlled (e.g., by minimizing the formation of colored impurities), such as by using light shielding or appropriate distillation equipment, as described below.

[0138] APHA color, also known as the Hazen or platinum / cobalt (Pt / Co) scale, is commonly used in the chemical industry as a yellowness index to assess the color of colorless to yellow liquids. 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 ranges from 0 to 500, where 1 APHA color equals 1 ppm of Pt / Co. APHA color can be assessed by visual comparison of standards or using a spectrophotometer, as described in ASTM D1209-05 (2019).

[0139] Organometallic tin compounds of formula (1) are useful in forming high resolution EUV lithography patterning precursors and are attractive due to their high purity and minimal concentration of dialkyl impurities of formula (2) and other impurities as described above.

[0140] Synthesis method

[0141] Aspects of the present disclosure also relate to methods for synthesizing high purity alkyl tin compounds of formula (1) above suitable for use in the microelectronics industry. These high purity compounds can be substantially free of dialkyl tin compounds of formula (2) and / or impurities of formula (4) or (5), have a desired level of color, and can be prepared without the need for multiple stages of distillation, or in some embodiments, without any purification.

[0142] For the purposes of this disclosure, the term "high purity" may be understood to mean a purity greater than about 99 mol%, more preferably greater than about 99.1 mol%, greater than about 99.2 mol%, greater than about 99.3 mol%, greater than about 99.4 mol%, greater than about 99.5 mol%, greater than about 99.6 mol%, greater than about 99.7 mol%, greater than about 99.8 mol%, greater than about 99.9 mol%, greater than about 99.95 mol%, greater than about 99.98 mol%, greater than about 99.99 mol%, or even higher. The term "substantially free" may be understood to mean that when a sample is tested using specific conditions without dilution in a deuterated solvent, for example, using more than 2,000 scans, 119 Sn NMR does not detect impurities and the detection limit can be as low as 0.3 mol%, 0.1 mol%, 0.05 mol% or 0.04 mol% (depending on the specific compound or impurity). For the specific impurities described herein, the detection limit is 0.01 mol%.

[0143] 119Sn NMR spectroscopy is well suited for the quantitative analysis of monoalkyltin compounds due to 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 makes the identification and quantification of monoalkyltin compounds and their impurities easy because 119 Sn resonances are highly resolved. 1 Compared with other analytical methods such as H NMR, 119 Sn NMR has low sensitivity. To improve sensitivity, monoalkyltin compounds are analyzed without dilution and a large number of spectra (at least 2000, preferably more than 10,000 for unknown impurities) are collected to detect the low-level impurities described in this study. Using this approach, detection limits of 0.01 mol% for dialkyltin diamino and other Sn compounds such as compounds of formula (2), (4) and (5) can be achieved. In Sn(NMe 2 ) 4 In the case of , the detection limit was 0.3 mol % due to the broad peak.

[0144] Described in this article 119 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 Sn NMR spectra were obtained by using the reverse 1 The spectra were obtained with H decoupling, 45° pulses, 1 s relaxation delay and sufficient scans to achieve the required sensitivity. Samples were prepared without dilution in deuterated solvents. Quantification was performed by integrating all peaks in the spectrum and setting the total peak area to 100. Each peak in the spectrum represents a different tin compound and the area of ​​each peak represents the concentration or purity of that compound in mol%.

[0145] Generally speaking, the method for preparing a monoalkyltin triamino compound according to aspects of the present disclosure involves the following general steps, each of which is described below:

[0146] 1. Lithiating a solution of dimethylamine and a first solvent to prepare lithium dimethylamide;

[0147] 2. adding the solution containing alkyl tin trichloride and the second solvent to the lithium dimethylamide solution under stirring;

[0148] 3. Remove the LiCl salt product by filtration;

[0149] 4. removing the solvent under vacuum to produce a crude product; and optionally 5. distilling the crude product to obtain a product containing at least about 99 mol % monoalkyltintriamide.

[0150] As mentioned previously, reaction conditions and parameters, such as solvents, relative amounts of reactants, stirring conditions, temperature, and concentrations, should be strictly controlled to ensure the preparation of the desired compound in high purity.

[0151] Solvents

[0152] The first and second solvents are not particularly limited, but preferred solvents include hydrocarbons (such as but not limited to hexane, n-hexane, heptane and cyclohexane), aromatic hydrocarbons (such as but not limited to toluene and xylene) and ethers (such as but not limited to THF and Et 2 O), and mixtures thereof. Particularly preferred at present are hydrocarbons and aromatics as the main components of the solvent for removing LiCl by filtration. Toluene and hexane are currently the most preferred solvents for easily removing the product under low temperature vacuum after the reaction. In addition, ethers, such as the most preferred THF, are currently preferred solvents because lithium dimethylamide has a high solubility in these types of solvents. It is also within the scope of the present disclosure to use a mixture of these solvents. In some embodiments, the solvent used for the lithiation step is the same as the solvent used for the amination step.

[0153] The amount of lithium dimethylamide

[0154] The preferred amount of lithium dimethylamide is greater than about 3.0 equivalents, greater than about 3.05 equivalents, greater than about 3.09 equivalents, greater than about 3.10 equivalents, or greater than about 3.15 equivalents relative to the alkyl tin trichloride. If the amount of lithium dimethylamide is too low, the reaction rate will be too slow, and the amount of impurities will increase due to side reactions such as redistribution.

[0155] Stirring conditions during the addition of alkyl tin trichloride

[0156] The stirring speed during the addition of alkyl tin trichloride is of great significance for determining the purity of the resulting product. The solution of lithium amide in hexane or toluene is actually a heavy slurry, so in order to fully mix, it is preferably stirred at a high speed. On the other hand, due to the excessive weight of the slurry, the stirring speed is too fast and may cause problems with the motor. The preferred stirring speed is greater than about 10rpm, greater than about 20rpm, greater than about 40rpm, more preferably greater than about 60rpm, most preferably greater than about 100rpm. On the other hand, the preferred stirring speed is less than about 500rpm, less than about 400rpm, less than about 300rpm, more preferably less than about 250rpm, most preferably less than about 200rpm. In order to achieve good mixing, it is very important to select a suitable stirring blade shape and size. For example, suitable stirring blades include paddle blades, anchor blades, twinstir blades, belt blades, 3-blade retreat impellers and log bone blades. In the reaction (amination) between lithium amide slurry and alkyl tin trichloride, high blade peripheral speed is important because the small size and high reactivity of lithium amide slurry are high shear stresses obtained at blade peripheral speed (blade tip speed, m / s). Preferred blade peripheral speeds are 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, most preferably 50 rpm or less. The blade peripheral speed is calculated by the following formula (a):

[0157] Blade peripheral speed (m / s) = π x D x N / 60 (a)

[0158] In formula (a), D represents the blade diameter (m), and N represents the number of revolutions (rpm).

[0159] temperature

[0160] For the lithiation step, the preferred lower temperature is about -78°C, about -40°C, about -20°C, about -10°C, or the most preferred lower temperature is about 0°C, and the upper limit of the temperature is about 40°C, about 20°C, or the most preferred upper limit is about 10°C. Therefore, the preferred temperature range is about 0°C to about 10°C. If the reaction temperature of the lithiation is too low, the reaction viscosity may be too high. Conversely, if the reaction temperature is too high, HNMe 2 Will evaporate.

[0161] For the step of adding alkyl tin trichloride (amination), the preferred lower temperature is 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 the most preferred upper limit is about 10°C. Therefore, 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, and if the temperature is too high, by-products will be produced.

[0162] Concentration of lithium dimethylamide

[0163] Lithium dimethylamide is currently present in solution in an amount up to about 30 wt%, more preferably up to about 20 wt%, up to about 15 wt%, or up to about 10 wt%. It has been found that such dilute concentrations provide effective slurries for solid and liquid reactions. On the other hand, under industrial conditions, the productivity is lower under dilute conditions.

[0164] A method for preparing a monoalkyltin triamino compound having formula (1a)

[0165] R 1 Sn(NR 2 2 ) 3 (1a)

[0166] According to aspects of the present disclosure, the following steps are involved, each of which will be described in more detail below:

[0167] (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %;

[0168] (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride;

[0169] (c) removing the LiCl salt product by filtration; and

[0170] (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltintriamine having the formula (1a).

[0171] In formula (1a), R 1 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.

[0172] Preferably, the process steps (a) to (d) are carried out substantially without exposure to light, for example at least steps (a) and (b) are carried out in an amber or stainless steel reactor. As described below, exposure to light has an adverse effect on monoalkyltin triamide compounds.

[0173] In some embodiments, the first solvent and the second solvent are the same.

[0174] The first step of the method involves lithiation of dimethylamine in a first solvent (such as hexane) solution, with an amount of up to (but not more than) 10 wt %. It has been found that this dilute concentration provides an effective slurry for solid and liquid reactions. The lithiation is carried out at a preferred temperature of about -10°C to about 10°C, and in some embodiments, at about 0°C to about 10°C. The lithiation can be carried out with n-BuLi or other lithiation agents commonly used in the art such as t-BuLi or hexyl lithium. This lithiation agent is usually used in a hexane solution, and additional hexane can be added to bring the dimethylamine lithium into the desired concentration range. An excess of dimethylamine is required to ensure that the lithiation agent is completely reacted. The reaction is carried out under an inert atmosphere such as nitrogen or argon, and the addition rate is controlled to limit the exothermic reaction. After the addition is completed, the reaction mixture is heated to room temperature to evaporate the butane byproduct and excess dimethylamine, and then cooled to about -10°C to about 10°C, or in some embodiments, cooled to about 0°C to 10°C.

[0175] In the second process step, a solution of alkyl tin chloride in a second solvent, such as toluene, is added to the reaction mixture, which is maintained at a preferred temperature of about -10°C to about 10°C, or in some embodiments, at about 0°C to 10°C. The alkyl tin chloride is added so that the amount of lithium dimethylamide is at least about 3.09 equivalents relative to the amount of alkyl tin chloride. The alkyl tin chloride solution is preferably added dropwise to control the exothermic reaction. The second process step is preferably carried out in an inert atmosphere, such as nitrogen or argon.

[0176] After the addition of alkyl tin trichloride to the reaction mixture is completed, the reaction mixture is slowly heated to room temperature, for example within about four hours, and then stirred at room temperature for a period of time, for example about four hours. The reaction mixture is then filtered, for example by a Sparkler, to remove the LiCl byproduct. Other filtering methods known in the art may also be used. The resulting salt is then rinsed with anhydrous hexane or the like, and the solvent (such as hexane and toluene) is removed under reduced pressure by methods known in the art to prepare a crude product containing at least about 85 mol% of monoalkyl tin triamino.

[0177] Finally, in some embodiments, the crude product of formula (1a) is distilled, for example, at about 1 torr, for example, by using a 300 mm Pro-Pak column, discarding any distillate before the boiling point of the monoalkyltin triamine, and collecting only the distillate obtained at the boiling point of the monoalkyltin triamine to produce a product containing at least about 99 mol% of the monoalkyltin triamine of formula (1a). Table 1 shows the boiling points of two representative monoalkyltin triamines. For example, if the desired product is methyltin triamine, the fractions obtained below 34°C are discarded and only the fractions obtained at 34-35°C are collected.

[0178] Table 1: Boiling points of representative monoalkyltin triamides

[0179] Compound Bp(℃) <![CDATA[MeSn(NMe 2 ) 3 ]]> 34-35 / 1 tray <![CDATA[EtSn(NMe 2 ) 3 ]]> 38.0-38.5 / 0.6Tor

[0180] The distillate obtained at a boiling point of 34-35°C, such as methyltin triamino, contains monoalkyltin triamino compounds in a purity of at least about 99 mol%. For example, when the desired compound of formula (1a) is methyltin triamino, 119 The Sn NMR (pure) spectrum showed peaks at δ-16.78 (99.5%) and δ56.23 (0.5%), which were consistent with the published data for methyltintriamino and dimethyltindiamino, respectively.

[0181] After distillation, the compound of formula (1a) contains less than about 1 mol % of R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 ) or less than about 0.05 mol% of R 1 SnNR 2 2 (N(R 2 )CH 2 NR 2 2 ).

[0182] Another aspect of the present invention is directed to a method for synthesizing a monoalkyltin triamino compound having the formula (1) and having a purity of at least about 85 mol %:

[0183] R 1 Sn(NR 2 2 ) 3 (1)

[0184] Where R 1 Selected from R A and R B ,

[0185] 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

[0186] Each R 2 is independently an alkyl group having about 1 to 10 carbon atoms; the method comprising:

[0187] (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %;

[0188] (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride;

[0189] (c) removing the LiCl salt product by filtration; and

[0190] (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltin triamino group having the formula (1), wherein the first solvent is the same as the second solvent; and

[0191] The compound having formula (1) is distilled.

[0192] According to aspects of the present disclosure, a method for preparing an isopropyltin triamino compound having formula (3) comprises the following steps:

[0193] (a) lithiating dimethylamine in a hexane solution at about 0° C. to 10° C. to produce lithium dimethylamide in hexane at a concentration of up to about 10 wt %;

[0194] (b) adding a solution of isopropyltin trichloride in toluene at a temperature of 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 isopropyltin trichloride;

[0195] (c) removing the LiCl salt product by filtration; and

[0196] (d) removing the hexane and toluene under vacuum to produce a product containing at least about 99 mole percent of the isopropyltin triamide having formula (3).

[0197] According to aspects of the present disclosure, a second method for preparing an isopropyltin triamino compound having formula (3) comprises the following steps:

[0198] (a) lithiation of dimethylamine in THF solution at about 0°C to 10°C to prepare lithium dimethylamide;

[0199] (b) adding a solution of isopropyltin trichloride in toluene at a temperature of 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 isopropyltin trichloride;

[0200] (c) removing the LiCl salt product by filtration; and

[0201] (d) removing THF and toluene under vacuum to produce a product containing at least about 99 mol % of the isopropyltintriamide having formula (3).

[0202] The method for preparing the isopropyltin triamino compound of formula (3) is the same as the method for preparing the monoalkyltin triamino compound of formula (1) described above, except that no distillation step is required, that is, the product obtained after step (b) is already at least about 99 mol% pure. The method described above for synthesizing the isopropyltin triamino compound of formula (3) can also be used to synthesize other alkyltin triamine compounds of formula (1) by changing the alkyltin trichloride reactant.

[0203] The isopropyltin triamine prepared by the method of the present disclosure is essentially a colorless liquid. 119 Sn NMR (pure) 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 of isopropyl triaminotin and diisopropyl diaminotin, respectively. However, if necessary, the product can be further distilled to remove any unwanted organic impurities and / or by-products, as well as to separate any photodecomposition by-products. It has been found that, contrary to the literature reports of collecting the distilled product at 50-52°C and 1.4 mTorr, the product obtained at 49-53°C and 0.5 Torr has the desired high purity and is the desired colorless.

[0204] While the amination reaction to form the monoalkyltin triamine is proceeding, the Kocheshkov-like antidisproportionation reaction shown in the above scheme (I) also occurs, and even low temperatures, such as about -78°C to 10°C, do not prevent the antidisproportionation reaction from occurring. On the contrary, it has been found that low temperatures slow down the substitution reaction, which increases the risk of antidisproportionation. In addition, according to 119 SnNMR measurements show that light or heat can accelerate the anti-disproportionation reaction and form up to 15 mol% of dialkyltin amino groups. According to the method reported by Lorberth, the amination reaction is carried out in the form of a solid slurry in hexane and is a liquid reaction.

[0205] The methods described herein solve known problems in a number of ways. First, as described herein, it has been discovered that in order to prevent back disproportionation reactions from occurring during the reaction, lithium dimethylamide must be properly prepared. Second, the concentration of the reactants is diluted, such as by using a lithium dimethylamide slurry in hexane at a concentration of no more than about 10 wt %. Third, back disproportionation reactions can be minimized by conducting the reaction at a preferred temperature of about -10°C to 10°C or about 0°C to about 10°C, rather than at lower temperatures. Finally, THF can be used instead of hexane to form a uniform solution of lithium dimethylamide. Using the methods described herein, iPrSn(NMe 2 ) 3 It can be prepared in a pilot scale at very high purity (containing no more than about 0.05 mol % of dialkyltin compounds and other specific impurities) without purification.

[0206] purification

[0207] Other aspects of the present disclosure also relate to methods for purifying the monoalkyltin triamino compound having the above formula (1).

[0208] Purification methods encompassed by the present disclosure include:

[0209] Single-stage flash evaporation to remove metal contaminants;

[0210] Fractionation to remove dialkyltin impurities as heavy fractions;

[0211] Fractional distillation to remove tetraalkyltin impurities as light fractions;

[0212] Simultaneous removal of dialkyltin and tetraalkyltin impurities using fractional distillation in either batch or continuous mode;

[0213] Use microchannel distillation to remove near-boiling dialkyl and tetraalkyl impurities;

[0214] Fractionation to remove both metal contaminants and dialkyltin and tetraalkyltin impurities;

[0215] Use of light-proof materials to prevent the formation of photodecomposition products of organotin compounds;

[0216] Limiting the bottom temperature (e.g., less than 112°C) to limit distillation of tetraalkyltin compounds;

[0217] Operate the condenser at or near the dew point of the overhead product to improve operating efficiency;

[0218] Treating the residue from the initial distillation process with concentrated dialkyltin impurities by the same or a different purification process,

[0219] To recover more desired isopropyltrimethylaminetin product and / or purified dialkyltin product;

[0220] Rebalancing the dialkyl and tetraalkyl byproducts to produce the desired isopropyltrimethylaminetin product;

[0221] Recycling the residue from the initial distillation process through the final step of the manufacturing process to exploit the equilibrium deproportionation reaction of the desired product to dialkyl and tetraalkyltin impurities;

[0222] Maintaining minimum dialkyltin impurity levels in the distillation feed to exploit the same equilibrium antidisproportionation reaction;

[0223] Use of adsorbents or ion exchange resins to reduce metal impurities, chloride impurities, water and oxygen; and / or

[0224] Use of adsorbents to reduce color without introducing isopropyltrimethylammonium tin decomposition products.

[0225] Size of alkyl groups (and their relationship to NMe 2 Similarity in group size) will affect the difference in boiling points between monoalkyltin triamides and dialkyltin diamides, and fractional distillation is usually the best method for separating the contaminants. For example, i PrSn(NMe 2 ) 3 (A) and i Pr 2 Sn(NMe 2 ) 2 The difference between the molecular weights of (B) is small (294 g / mol and 293 g / mol, respectively). For the tert-butyl compound, the triaminotin compound is only 13 g / mol lighter than the diaminotin compound. Considering the isopropyl analog, the difference between isopropyl and dimethylamino is only 1 g / mol, and the polarity is very similar, the difference in boiling point between compounds A and B is likely to be very small. Figure 1 As shown, the boiling points of these two compounds with a purity of >97 mol% were detected over a wide range of pressures. It can be seen that the boiling point difference between the two compounds is within 2°C over the pressure range of 0.7-10 Torr. In another example, t BuSn(NMe 2 ) 3 and t Bu 2 Sn(NMe 2 ) 2 The boiling points at 0.4 torr are 50°C (measured) and 90°C, respectively (reported in Chemische Berichte, 112 (8), 2798-803 (1979)). Therefore, purification by fractional distillation is challenging and requires specially developed specific distillation parameters. This purification method can providei PrSn(NMe 2 ) 3 or the like having a dialkyl content of <0.5 mol%, <0.4 mol%, <0.03 mol%, <0.2 mol%, <0.1 mol%, <0.05 mol% or no detectable contamination with dialkyltin compounds, as described below.

[0226] When the mass difference between the alkyl group and the amino group is large (e.g., tBu-NMe 2 When the mass difference of the pair is 13 amu), the difficulty of fractional purification is expected to be less. When the difference is very small, purification is expected to be more difficult. For example, iPr-NMe 2 The difference between the two groups is -1 amu (i.e., the iPr group is slightly lighter than the amino group). 2 The molecular weight difference between the two groups is 39 amu, cycloheptyl-NMe 2 The molecular difference of the pair is 53 amu. Schwarzenbach et al. (Environmental Organic Chemistry; 56-75 (1993)) observed that for a similar series of compounds, increasing the molecular weight of the components within a certain molecular weight range will reduce the vapor pressure. In essence, compounds with more electrons have stronger London forces. However, this does not solve the non-ideal behavior often observed in multi-component vapor-liquid equilibrium.

[0227] Another aspect of the present invention relates to a method for purifying iPrSn(NMe 2 ) 3 The method comprises fractionating the product 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, and most preferably about 1 Torr). If the pressure is too high, the formation of decomposition and redistribution products will be accelerated. If the pressure is too low, the volatilization rate is too high and the separation efficiency through the distillation column is too low.

[0228] The fractionation preferably uses a pot temperature of about 50°C to about 120°C (preferably greater than about 50°C, greater than about 60°C, preferably greater than about 70°C, preferably greater than about 80°C, preferably greater than about 90°C, preferably greater than about 100°C, most preferably greater than 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 rate is too low and the distillation time is too long. On the contrary, if the pot temperature is too high, the decomposition of the product will be accelerated.

[0229] The fractionation is preferably carried out using the desired compound of formula (1), such as iPrSn(NMe 2 ) 3 iPrSn(NMe) with a purity greater than about 99.5 mol % is obtained at 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, and most preferably within about 1°C of the dew point of the catalyst, and a reflux ratio of about 10 to 100 (preferably about 20 to 80, more preferably about 40 to 60, and more preferably about 50). 2 ) 3 In one embodiment, the purified iPrSn(NMe 2 ) 3 The sample contained less than about 0.1 mol% (iPr) 2 Sn(NMe 2 ) 2 , which is determined by known analytical methods such as GC and HPLC, or even by 119 Sn was not detectable by NMR.

[0230] Therefore, a purification according to the present invention i PrSn(NMe 2 ) 3 The method is to use a pot temperature of less than about 112°C for fractionation to avoid the formation of tetramethylaminotin compound Sn(NMe 2 ) 4 and removal of large amounts of dialkyltin compounds (iPr) 2 Sn(NMe 3 ) 2 .

[0231] For example, according to aspects of the present disclosure, i PrSn(NMe 2 ) 3 The following conditions can be used in the fractional distillation purification method: 10 torr pressure, 105°C pot temperature, 95°C condenser temperature and 50 reflux ratio. i PrSn(NMe 2 ) 3 Initially, fractionation using these parameters produced a 99.5% fraction and a corresponding 95.7% bottoms product after removing 46 g from an initial feed of 8.6 kg. Without diluting the sample with a deuterated solvent, the fraction was 119 Purity was determined by Sn NMR.

[0232] Monoalkyltin triamides can be disproportionated to dialkyltin diamides and tetraamides. The degree of disproportionation is affected by the temperature of the distillation pot, and higher temperatures are expected to result in higher degrees of disproportionation. The activation energy of disproportionation is related to the size of the alkyl group (R). For example, when R is a methyl group, the disproportionation reaction can be observed at around 45°C. As another example, when R is an isopropyl group, the disproportionation reaction occurs at around 110°C. The disproportionation of tert-butyl groups occurs at higher temperatures. Depending on the difference between the mass of the alkyl group and the amino group, the molecular weights of the two impurities produced by the disproportionation of monoalkyltin triamides are different from those of the starting monoalkyl compound. One product will be heavier than the starting monoalkyltin triamide, and the other product will be lighter than the monoalkyltin triamide. Therefore, the lighter compound is expected to appear in the distillate fraction of the distillation, and the heavier compound will appear in the bottom fraction of the distillation, resulting in both light and heavy impurities, increasing the difficulty of distillation. Therefore, it has been found that limiting the pot temperature, and thus limiting the degree of disproportionation, can not only improve the yield by limiting the loss of the desired monoalkyl product, but also avoid the production of other impurities that need to be removed. As is well known in the art, determining the optimal conditions for separating similar components using distillation is not simple or predictable and requires extensive analysis and experimentation of various interrelated parameters.

[0233] Photosensitivity

[0234] Studies have shown that monoalkyltin triamides are light sensitive, so proper light protection is required during the reaction and purification process. 2 ) 3 It is a colorless liquid. However, when iPrSn(NMe 2 ) 3 When NMR samples are placed under normal room lighting in a laboratory, the samples will turn yellow. Figure 2 The shelf life data shown highlights this color change. Upon exposure to light, a new 119 Sn resonance, indicating the formation of a photoinduced decomposition byproduct, iPrSn(NMe 2 ) 2 (NMeCH 2 NMe 2 ). Figure 3 The formation of compounds having formula (5) is shown 119 SnNMR. The photodecomposition rate increases with increasing temperature. Therefore, the purified iPrSn(NMe 2 ) 3 Keeping the samples in the dark (not exposed to light) minimizes the formation of unwanted photoinduced decomposition byproducts and allows for the availability of (iPr)Sn(NMe 2 ) 3,in 119 The total content of substances with a chemical shift of about -84 ppm in the Sn NMR spectrum is less than 1% by mass. Light control is also important in the reaction step of preparing monoalkyltin triamides, which can be achieved by using an amber or stainless steel reactor or a light-shielding glass reactor.

[0235] Similarly, a stainless steel column filled with stainless steel filler can be used for distillation. Alternatively, distillation can be performed in a light-shielding device containing glass, such as a glass apparatus, a glass-lined apparatus, a glass-coated apparatus, etc. Shielding can be achieved by any method known in the art, for example, using a light-shielding container such as an amber glass, metal (SUS) container, wrapping the container with a light-shielding cover such as a cloth, foil or film, using a light-shielding coating, or performing distillation in a dark room.

[0236] store

[0237] A method for storing a sample of a monoalkyltin triamide compound having formula (1) and having a purity of at least about 99 mol % (e.g., but not limited to, a sample of greater than about 0.5 kg), comprising storing the sample of the monoalkyltin triamide compound having formula (1) substantially without exposure to light and at a temperature of less than about 30° C. The sample of the compound having formula (1) has less than about 1 mol % or less than about 0.05 mol % of R 1 Sn(NR 2 2 ) 2 (N(R 2 )CH 2 NR 2 2 )content.

[0238] Samples of monoalkyltin triamide compounds of formula (1) can be stored for about three days to about one year, such as about one week or longer, not more than about ten months, about two to six weeks, and all intermediate times as desired. Preferably, the sample is stored at a temperature of less than about 30°C, less than about 25°C, less than about 20°C, and preferably greater than about -10°C. "Substantially not exposed to light" can be understood as the sample being protected from light to the greatest extent possible, such as by storage in an amber or stainless steel container. In an embodiment, as described above, after a storage period of about three days to about one year, the monoalkyltin triamide sample is substantially free of decomposition.

[0239] Reduce other impurities

[0240] It is reasonable to assume that the metal impurities in the alkyltin triamide are in the form of metal chlorides. If so, they can be removed by an adsorbent, such as BASF CL-750, a chloride adsorbent known in the industry. There may be other chloride impurities, such as amine hydrochlorides and lithium chloride, which may be carried over during the production process and become impurities of concern. Removal by chloride-scavenging adsorbents such as CL-750, activated carbon, or activated alumina may be effective. Finally, the desired tin compound may contain water and oxygen impurities. Carbon promoted and then activated with metal halides has been used to remove water and oxygen from HCl gas, and similar methods may be effective.

[0241] The invention will now be described with reference to the following non-limiting examples.

[0242] Example 1: Column design and general operation

[0243] The following distillation parameters were used in the following examples:

[0244] a. Glass-lined steel sump, nominal 16 liters

[0245] b. 2” Schedule-40 316-SS Heating Column

[0246] c. 0.24” 316L SS ProPak packing, total column length 5 feet

[0247] d. On / off reflux splitter operating at apparent reflux ratio of 33 to 50

[0248] e. Stainless steel shell and tube condenser operates as a total condenser

[0249] f.304SS receiver

[0250] g.316SS product container

[0251] Example 2: Distillation and purification of (iPr)Sn(NMe 2 ) 3 Demo

[0252] Using 97% pure (iPr)Sn(NMe 2 ) 3 The sample was used as feed, with 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 product fraction purity was 99.5%, and the purity of the two inline distillate samples was 99.8% and 99.7% of (iPr)Sn(NMe 2 ) 3 , without using deuterated solvent to dilute the sample, using 119 Sn NMR.

[0253] Example 3: Effect of condenser temperature on (iPr)Sn(NMe 2 ) 3 Effect of Fractionation

[0254] (iPr)Sn(NMe 2 ) 3 Three distillation runs were performed and their fractionation efficiency was characterized using the Fenske equation (α^N), which is an analytical calculation of samples collected from the tank and receiver after a period of operation (2 to 8 hours). The reflux ratio was 50 and the pressure was 10 Torr. The results are shown in Table 2 below, indicating that the condenser temperature has a significant effect on the overall performance of the distillation, as evaluated by higher fractionation efficiency. iPrSn(NMe 2 ) 3 The dew point of the column is 96° C. Therefore, operating the condenser at conditions close to the dew point of the product stream is beneficial for achieving separation and maximizing the efficiency of the column.

[0255] Table 2: Distillation conditions of Example 3

[0256]

[0257] Example 4: Effect of Tank Temperature on the Properties of Tetraalkyl Sn(NMe 2 ) 4 Effect of impurity formation

[0258] TetraaminoSn(NMe 2 ) 4 Impurity (6) is composed of (iPr)Sn(NMe 2 ) 3 disproportionately, co-producing the existing dialkyl (iPr) 2 Sn(NMe 2 ) 2 Impurities (7). The effect becomes apparent when the tank temperature is increased from 110°C to 115°C.

[0259]

[0260] The tetraamine impurity (FW = 295.0) is a light component in the distillation and therefore appears in the distillate. In contrast, the dialkyl impurity (FW = 293) is a heavy component and appears in the bottoms. This is counterintuitive based on the (admittedly slight) difference in weight in the formula. (iPr)Sn(NMe 2 ) 3 The FW is 294.0. The desired (iPr)Sn(NMe 2 ) 3 The compound becomes the intermediate product. Then, the batch distillation process requires a forecut to remove the four impurities. Continuous distillation requires two columns to recover (iPr)Sn(NMe 2 ) 3 .

[0261] The following conditions were used:

[0262] a. Condenser temperature = 90°C

[0263] b. Reflux ratio = 40 to 50

[0264] c. Pressure = 10 Torr

[0265] d. Tank temperature = 111.1 to 111.9°C

[0266] The compositions tested in the system show the effect of increasing the tank temperature on the degree of purification achieved as shown below in Tables 3 and 4. In Tables 3 and 4, tin compounds (3), (6) and (7) have the structures described above.

[0267] At 110°C, no tetraaminotin (6) was observed in either the receiver or the sample collected from the reflux into the column. At higher pot temperatures, the amount of tetraaminotin in the receiver and reflux samples increased. None of the pot samples showed any tetraaminotin, indicating that this compound is a light component, although it is lighter than iPrSn(NMe 2 ) 3 Slightly heavier (1amu).

[0268] Table 3: Distillation results of Example 4

[0269]

[0270] ND; 119 Sn NMR not detected

[0271] Table 4: Distillation results of Example 4

[0272]

[0273] ND; 119 Sn NMR not detected

[0274] Example 5: Synthesis of methyltri(dimethylamino)tin

[0275] Anhydrous hexane (970.5 g, 11.26 mol) and n-butyl lithium (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 subsurface at a temperature of about 0-10° C. The reaction mixture was stirred for another 4 hours while warming to room temperature, and then methyl tin trichloride (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 within four hours and stirred at room temperature for another four hours. The reaction mixture was filtered through a Sparkler to remove the LiCl byproduct. The salt was rinsed with anhydrous hexane (2 x 100 mL). The solvent was removed under reduced pressure and the residue was distilled under reduced pressure (34-35° C., 1 torr) using a 316SS Pro-Pak column equipped with an amber distillation head. The product was collected in an amber glass receiver as a clear colorless liquid. Yield: 74.0 g (53.4%), 119 Sn NMR (400 MHz; pure): δ -16.78. 1 H NMR (400 MHz; C 6 D 6 ):δ2.79(s.18H,NCH 3 ),δ0.12(s,3H,CH 3 ).purity( 119 Sn NMR): 99.5% product, 0.5% dimethyltin diamide. 119 Sn and 1 H NMR spectrum Figure 4 and 5 shown.

[0276] Example 6: Synthesis of isopropyltri(dimethylamino)tin

[0277] Anhydrous hexane (6.3 kg, 73 mol) and n-butyl lithium (3.1 kg, 11.75 mol, 2.4 M in hexane solution) were charged into a 22 L 316 stainless steel reactor equipped with a banana blade (CG-16). Dimethylamine (1.1 kg, 23.5 mol) was added subsurface at about 0-10°C and stirred at a speed of about 200 rpm. The reaction mixture was stirred for another 4 hours while warming to room temperature, and then isopropyl tin trichloride (1.0 kg, 3.73 mol) was added dropwise at about 0-10°C. The resulting mixture was heated to room temperature within four hours and stirred at room temperature for another four hours. The reaction mixture was filtered through a Sparkler to remove the LiCl byproduct. The salt was rinsed with anhydrous hexane (2 x 500 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 316SS Pro-Pak column equipped with an amber distillation head. The product was collected in an amber glass receiver as a clear colorless liquid. Yield: 803 g (73.3%). 119 Sn NMR (400 MHz; pure): δ -64.85. 1 HNMR (400 MHz; C 6 D 6 ):δ2.85(s.18H,NCH 3 ),δ1.61(m,1H,methine),δ1.27(d,6H,CH 3 ).purity( 119 SnNMR): 99.8% product, 0.2% diisopropyltin diamide (7), 0.0% compound (5) ( 119 Sn NMR (400 MHz; pure): δ -84 ppm). 119 Sn and 1 H NMR spectrum Figure 6 and 7 The product was stored in 316SS stainless steel ampoules at 25°C protected from light.

[0278] Example 7: Synthesis of isopropyltri(dimethylamino)tin

[0279] Anhydrous THF (1.0 kg, 13.86 mol) and n-butyl lithium (1.2 kg, 4.61 mol, 2.4 M in hexane solution) were charged into an amber glass reactor. Dimethylamine (0.38 kg, 8.32 mol) was added subsurface at a temperature of about 0-10°C. The reaction mixture was stirred for another 4 hours while warming to room temperature, and then isopropyl tin trichloride (0.4 kg, 1.49 mol) was added dropwise at about 0-10°C. The resulting mixture was heated to room temperature within four hours and stirred at room temperature for another four hours. The reaction mixture was filtered through a Sparkler to remove the LiCl byproduct. The salt was rinsed with anhydrous hexane (2 x 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 316SS Pro-Pak column equipped with an amber distillation head. The product was collected in an amber glass receiver as a clear colorless liquid. Yield: 305 g (69.5%). 119 Sn NMR (400 MHz; pure): δ -64.85. 1 H NMR (400 MHz; C 6 D 6 ):δ2.85(s.18H,NCH 3 ),δ1.61(m,1H,methylene),δ1.27(d,6H,CH 3 ).purity( 119 Sn NMR): 99.57% product, 0.43% diisopropyltin diamide. 119 Sn NMR spectrum Figure 8 shown.

[0280] Example 8: Effect of Temperature on the Synthesis of Isopropyltris(dimethylamino)tin

[0281] In three parallel experiments, anhydrous hexane (217.1 g, 2.52 mol) and n-butyl lithium (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 subsurface at a temperature of about 0 to 10°C. The reaction mixture was stirred for another four hours while warming to room temperature, and then isopropyl tin trichloride (53.6 g, 0.2 mol) was added dropwise at about -78°C, about -40°C, or about 0°C. The resulting mixture was heated to room temperature within four hours and stirred at room temperature for another four hours. The reaction mixture was filtered through a Sparkler to remove the LiCl byproduct. The salt was rinsed with anhydrous hexane (2 x 100 mL). The solvent was removed under reduced pressure. The relative amounts of the desired product (3) and the byproduct (7) are shown in Table 5, and the reaction was carried out at about 0°C, about -40°C, and about -78°C. 119 Sn NMR spectra are shown in Fig. 9 ,10 and 11. It can be seen that the highest purity is obtained at about -78°C and about 0°C, and the lowest purity is obtained at about -40°C. In addition, among the three temperatures studied, the ideal temperature for the reaction is about 0°C.

[0282] Table 5. Temperature control reaction results

[0283]

[0284] Example 9: Effect of Photolysis on the Synthesis of Isopropyltris(dimethylamino)tin

[0285] Anhydrous hexane (120.6 g, 1.40 mol) and n-butyl lithium (127 ml, 0.35 mol, 186.6 g, 2.76 M solution in hexane) were charged into a 5 liter glass reactor that was not shaded to protect from light. Dimethylamine (48 ml, 0.70 mol) was added subsurface at a temperature of about 0-10°C. The reaction mixture was stirred for another 4 hours, and then isopropyl tin trichloride (30.4 g, 0.11 mol) was added dropwise at about 0°C. The resulting mixture was warmed to room temperature within four hours and stirred at room temperature for another sixteen hours. The reaction mixture was filtered through a funnel to remove the LiCl by-product. The salts were rinsed with anhydrous hexane (100 mL). The solvent was removed under reduced pressure in an unshielded 1 L glass flask. By 119 Sn NMR determined the relative amounts of the desired product (3) and byproducts (7) and (4) to be:

[0286] Product (3): 98.0 mol%, Impurity (7): 0.4 mol%, Compound (5): 1.6 mol%.

[0287] Those skilled in the art will appreciate that changes may be made to the above embodiments without departing from the broad inventive concept thereof. Therefore, it should be understood that the present invention is not limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A monoalkyltin triamino compound having the formula (1) and having a purity of at least about 99 mol %: R 1 Sn(NR 2 2)3(1) Where R 1 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 from about 1 to 10 carbon atoms; and Where R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) is present in an amount less than about 1 mol%.

2. The monoalkyltin triamino compound according to claim 1, characterized in that The content of dialkylbis(dialkylamino)tin having formula (2) is less than about 1 mol% R 1 2Sn(NR 2 2)2(2)。 3. The monoalkyltin triamino compound according to claim 1 or 2, characterized in that The total tetrakis(dialkylamino)tin content is less than about 1 mol %.

4. The monoalkyltin triamino compound according to any one of the preceding claims, characterized in that The tetraalkyltin content is less than about 1 mol%.

5. The monoalkyltin triamino compound according to any one of the preceding claims, characterized in that The color is essentially colorless.

6. The monoalkyltin triamino compound according to claim 5, characterized in that: The APHA is less than about 20.

7. The monoalkyltin triamino compound according to any one of the preceding claims, characterized in that R 1 is isopropyl, R 2 is a methyl group, and the compound has the formula (3):

8. The monoalkyltin triamino compound according to claim 7, characterized in that: The content of diisopropylbis(dimethylamino)tin is less than about 1 mol %.

9. The monoalkyltin triamino compound according to claim 5, characterized in that: The total tetrakis(dimethylamino)tin content is less than about 1 mol %.

10. The monoalkyltin triamino compound according to any one of the preceding claims, characterized in that R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) is present in an amount less than about 0.05 mol%.

11. A method for synthesizing a monoalkyltin triamino compound having formula (1a) and a purity of at least about 85 mol %: R 1 Sn(NR 2 2)3(1a) in, R 1 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; the method comprising: (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %; (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride; (c) removing the LiCl salt product by filtration; and (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltintriamine having the formula (1a).

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

13. The method according to claim 11 or 12, characterized in that: The compound of formula (1a) contains less than about 1 mol % of R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2).

14. The method according to claim 13, characterized in that The compound of formula (1a) contains less than about 0.05 mol% of R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2).

15. The method according to any one of claims 11 to 14, characterized in that Step (b) is carried out at a temperature of about -78°C to about 40°C.

16. The method according to claim 15, characterized in that Step (b) is carried out at a temperature of about 0°C to about 10°C.

17. The method according to any one of claims 11 to 16, characterized in that 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.

18. The method according to any one of claims 11 to 17, characterized in that Steps (a) to (d) are performed substantially without exposure to light.

19. The method according to any one of claims 11 to 18, characterized in that Steps (a) and (b) are carried out in a stainless steel container.

20. The method of claim 11, further comprising distilling the compound having formula (1a).

21. The method according to claim 20, characterized in that The distillation comprises distilling a crude product having formula (1a) at about 1 torr, discarding any distillate before the boiling point of the monoalkyltriamine having formula (1a), and collecting the distillate obtained at the boiling point of the monoalkyltintriamine having formula (1a) to obtain a product containing at least about 99 mol% of the monoalkyltintriamine having formula (1a).

22. The method of claim 20 or 21, comprising fractionating 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 monoalkyltin trisaminoglycidylamine compound of formula (1a) contains less than about 0.1 mol % of the dialkylbis(dialkylamino)tin compound of formula (2).

23. A method according to any one of claims 20 to 22, comprising carrying out the distillation in the absence of substantial exposure to light.

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

25. The method according to any one of claims 20 to 24, characterized in that The distillation was performed using a stainless steel column filled with stainless steel packing.

26. The method according to any one of claims 20 to 25, characterized in that The distillation was carried out in a light-tight apparatus containing glass.

27. A method for storing a sample of a monoalkyltin triamide compound having formula (1) and having a purity of at least about 99 mol %: R 1 Sn(NR 2 2)3(1) Where R 1 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; The method comprises storing a sample of a monoalkyltin triamide compound having formula (1) substantially without exposure to light and at a temperature of less than about 30°C.

28. The method according to claim 27, characterized in that The sample of the monoalkyltin triamino compound having formula (1) was stored for about three days to about one year.

29. The method according to claim 27 or 28, characterized in that The monoalkyltintriamide samples showed substantially no decomposition after storage for about three days to about one year.

30. The method according to any one of claims 27 to 29, characterized in that In the monoalkyltin triamino sample having the formula (1), R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) is present in an amount less than about 1 mol%.

31. The method according to claim 30, characterized in that In the monoalkyltin triamino sample having the formula (1), R 1 Sn(NR 2 2)2(N(R 2 )CH2NR 2 2) is present in an amount less than about 0.05 mol%.

32. The monoalkyltin triamino compound of formula (1) according to any one of claims 1 to 10, characterized in that R 1 Selected from R A and R B , the compound is prepared by a method comprising the following steps: (a) lithiation a solution comprising dimethylamine and a first solvent to produce a lithium dimethylamide solution having a concentration of up to about 10 wt %; (b) adding a solution comprising alkyl tin chloride 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 alkyl tin chloride; (c) removing the LiCl salt product by filtration; and (d) removing the first solvent and the second solvent under vacuum to prepare a crude product containing a monoalkyltintriamine group having the formula (1).

33. The method according to claim 32, characterized in that Step (b) is carried out at a temperature of about -78°C to about 40°C.

34. The method according to claim 33, characterized in that Step (b) is carried out at a temperature of about 0°C to about 10°C.

35. The method according to any one of claims 32 to 34, characterized in that 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, characterized in that Steps (a) to (d) are performed substantially without exposure to light.

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

38. The method of any one of claims 32-37, further comprising distilling the compound of formula (1).

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