CN111801297A - Method for producing ammonia, molybdenum complex and benzimidazole compound - Google Patents

Abstract

The method for producing ammonia of the present invention is a method for producing ammonia from a nitrogen molecule in the presence of a catalyst, a reducing agent, and a proton source. As the catalyst, use is made of, for example, [ MoI ]₃(PNP)](PNP is 2, 6-bis (di-tert-butylphosphinomethyl) pyridine). As the reducing agent, samarium (II) iodide was used, and as the proton source, alcohol or water was used.

Description

Method for producing ammonia, molybdenum complex and benzimidazole compound

technical field

The present invention relates to a method for producing ammonia, a molybdenum complex, and a benzimidazole compound.

Background technique

The Haber-Bosch process, which is an industrial method for converting nitrogen molecules into ammonia, is an energy-intensive process requiring high-temperature and high-pressure reaction conditions. On the other hand, in recent years, a method for producing ammonia from nitrogen molecules under mild conditions has been developed. For example, Non-Patent Document 1 reports that a molybdenum-iodine complex having a PNP ligand as a catalyst and 2,4,6-trimethylpyridine trimethylpyridine as a proton source as represented by the following formula In the toluene solution of the fluoromethanesulfonate, in the presence of nitrogen at atmospheric pressure, a toluene solution of cobalt-decamethyl cobaltene was added at room temperature as a reducing agent, and then stirred, thereby generating a molybdenum complex as a catalyst. The compound is based on 415 equivalents of ammonia.

prior art literature

Non-patent literature

Non-Patent Document 1: Bull.Chem.Soc.Jpn.2017, vol.90, pp1111-1118

SUMMARY OF THE INVENTION

The problem to be solved by the invention

However, in the above-mentioned Non-Patent Document 1, it is necessary to use a stoichiometric amount of an expensive decamethylcobaltocene and a conjugate acid of collidine. Therefore, from an industrial point of view, development of a cheaper ammonia production method is expected.

The present invention has been made in order to solve the above-mentioned problems, and its main purpose is to produce ammonia from nitrogen molecules relatively inexpensively.

methods for solving problems

In order to achieve the above object, the present inventors have studied a method for producing ammonia from nitrogen molecules using a certain molybdenum complex as a catalyst and samarium (II) iodide as a reducing agent, and found that alcohol and water can be used as the reducing agent. A proton source, thereby completing the present invention.

That is, the ammonia production method of the present invention is a method of producing ammonia from nitrogen molecules in the presence of a catalyst, a reducing agent and a proton source,

The above catalyst is (A) having 2,6-bis(dialkylphosphinomethyl)pyridine (wherein, the two alkyl groups may be the same or different, and at least one hydrogen atom of the pyridine ring may be replaced by an alkyl group, an alkoxy molybdenum coordination compound, (B) with N,N-bis(dialkylphosphinomethyl)benzimidazolidene (N,N-bis(dialkylphosphinomethyl)benzimidazolidene) as PNP ligand, Wherein, the two alkyl groups may be the same or different, and at least one hydrogen atom of the benzene ring may be substituted with an alkyl group, an alkoxy group or a halogen atom) as a molybdenum complex compound of PCP ligands, (C) having bis( Dialkylphosphinoethyl)arylphosphine (wherein the two alkyl groups may be the same or different) as molybdenum complexes of PPP ligands, or (D) trans-Mo(N ₂ ) ₂ (R) Molybdenum represented by ¹ R ² R ³ P) ₄ (wherein R ¹ , R ² , and R ³ are alkyl or aryl groups that may be the same or different, and two R ³ may be connected to each other to form an alkylene chain) coordination compounds,

As the above-mentioned reducing agent, a halide (II) of a lanthanoid metal is used,

As the above-mentioned proton source, alcohol or water is used.

According to this method for producing ammonia, alcohol and water can be used as proton sources, and the reaction proceeds even at normal temperature (0 to 40° C.), so that ammonia can be produced from nitrogen molecules at a lower cost than in the past.

Detailed ways

Preferred embodiments of the method for producing ammonia of the present invention are shown below.

The ammonia production method of the present embodiment is a method of producing ammonia from nitrogen molecules in the presence of a catalyst, a reducing agent, and a proton source. In this method, as a catalyst, (A) having 2,6-bis(dialkylphosphinomethyl)pyridine (wherein two alkyl groups may be the same or different, and at least one hydrogen atom of the pyridine ring may be Molybdenum complex compound, (B) having N,N-bis(dialkylphosphinomethyl)benzimidazocarbene (wherein, 2 The alkyl groups may be the same or different, and at least one hydrogen atom of the benzene ring may be substituted with an alkyl group, an alkoxy group or a halogen atom) as a molybdenum complex compound of PCP ligands, (C) having bis(dialkylphosphine) ethyl)arylphosphine (wherein the two alkyl groups may be the same or different) as a molybdenum complex of a PPP ligand, or (D) trans-Mo(N ₂ ) ₂ (R ¹ R ² R ³ P) ₄ (wherein, R ¹ , R ² and R ³ are alkyl or aryl groups which may be the same or different, and two R ³ may be connected to each other to form an alkylene chain) molybdenum complex compound. In addition, as the reducing agent, a halide (II) of a lanthanoid metal is used, and as a proton source, an alcohol or water is used.

In the molybdenum complex of (A), the alkyl group may be, for example, a straight chain or branched chain such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and structural isomers thereof. The alkyl group can also be a cyclic alkyl group such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The alkyl group preferably has 1 to 12 carbon atoms, and more preferably has 1 to 6 carbon atoms. Examples of the alkoxy group include linear or branched alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, and structural isomers thereof. The group may be a cyclic alkoxy group such as a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group. The alkoxy group preferably has 1 to 12 carbon atoms, and more preferably has 1 to 6 carbon atoms. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned, for example.

As a molybdenum complex compound of (A), the molybdenum complex compound represented by formula (A1), (A2) or (A3) is mentioned, for example. As the alkyl group, the alkoxy group and the halogen atom, the same groups and atoms as the alkyl group, the alkoxy group and the halogen atom have been exemplified. As R ¹ and R ² , a bulky alkyl group (eg, tert-butyl group, isopropyl group) is preferable. The hydrogen atom on the pyridine ring is preferably unsubstituted, or the hydrogen atom at the 4-position is substituted with a chain, cyclic or branched alkyl group having 1 to 12 carbon atoms.

(in the formula, R ¹ and R ² are alkyl groups that can be the same or different, X is an iodine atom, a bromine atom or a chlorine atom, and at least one hydrogen atom on the pyridine ring can be replaced by an alkyl group, an alkoxy group or a halogen atom replace)

As a molybdenum complex compound of (B), the molybdenum complex compound represented by formula (B1) is mentioned, for example. As the alkyl group, the alkoxy group and the halogen atom, the same groups and atoms as the alkyl group, the alkoxy group and the halogen atom have been exemplified. As R ¹ and R ² , a bulky alkyl group (eg, tert-butyl group, isopropyl group) is preferable. The hydrogen atom on the benzene ring is preferably unsubstituted, or the hydrogen atoms at the 5th and 6th positions are substituted with a chain, cyclic or branched alkyl group having 1 to 12 carbon atoms. Particularly preferred are molybdenum complex compounds of the formula (B2). In formula (B2), preferably R ¹ , R ² and X are the same as in formula (B1), at least one of R ³ and R ⁴ is substituted with a fluoro group, and still more preferably at least one of R ³ and R ⁴ are substituted by trifluoromethyl. The benzimidazole compound of formula (E) can be used as an intermediate for synthesizing the molybdenum complex of formula (B2). In formula (E), A is an anion, R ¹ , R ² and X are the same as in formula (B1), and R ³ and R ⁴ are the same as in formula (B2). Although it does not specifically limit as an anion of _A , For example, _PF6- ^{, BF4- ,} ClO4- etc. are mentioned _.

(in the formula, R ¹ and R ² are alkyl groups that can be the same or different, X is an iodine atom, a bromine atom or a chlorine atom, and at least one hydrogen atom on the benzene ring can be replaced by an alkyl group, an alkoxy group or a halogen atom replace)

As a molybdenum complex compound of (C), the molybdenum complex compound represented by formula (C1) is mentioned, for example. As the alkyl group, the same groups as those already exemplified can be mentioned. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a group obtained by substituting at least one atom of hydrogen atoms on these rings with an alkyl group or a halogen atom. Examples of the alkyl group and the halogen atom include the same groups and atoms as the alkyl group and the halogen atom already exemplified. As R ¹ and R ² , a bulky alkyl group (eg, tert-butyl group, isopropyl group) is preferable. As R ³ , for example, a phenyl group is preferable.

(In the formula, R ¹ and R ² are alkyl groups which may be the same or different, R ³ is an aryl group, and X is an iodine atom, a bromine atom or a chlorine atom)

As a molybdenum complex compound of (D), the molybdenum complex compound represented by formula (D1) or (D2) is mentioned. As the alkyl group and the aryl group, the same groups as those already exemplified can be mentioned. In formula (D1), it is preferable that R ¹ and R ² are aryl groups (eg, phenyl) and R ³ are alkyl groups having 1 to 4 carbon atoms (eg, methyl groups), or R ¹ and R ² are carbon atoms. 1-4 alkyl (eg methyl) and R ³ is aryl (eg phenyl). In formula (D2), preferably R ¹ and R ² are aryl groups (eg phenyl) and n is 2.

(In the formula, R ¹ , R ² and R ³ are alkyl or aryl groups which may be the same or different, and n is 2 or 3)

In the method for producing ammonia according to the present embodiment, it is preferable to use nitrogen at normal pressure as the nitrogen molecule. Since nitrogen gas is cheap, it can be used in large excess relative to other reagents.

In the method for producing ammonia according to the present embodiment, when an alcohol is used as a proton source, a diol may be used as the alcohol, or ROH (R is a carbon number of 1 to 6 in which a hydrogen atom may be substituted by a fluorine atom may be used) chain, cyclic or branched alkyl group, or phenyl group which may have an alkyl group). As diols, for example, ethylene glycol, propylene glycol, diethylene glycol, etc. are mentioned, among them, ethylene glycol is preferable. Examples of ROH include chain or branched alkyl alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, isobutanol, and tert-butanol; cyclopropanol, cyclopentanol, etc. Cyclic alkyl alcohols such as alcohols and cyclohexanol; alcohols containing fluorine atoms such as trifluoroethyl alcohol and tetrafluoroethyl alcohol; phenol derivatives such as phenol, cresol, and xylenol, and the like.

In the method for producing ammonia of the present embodiment, ammonia can be produced from nitrogen molecules in a solvent. Although it does not specifically limit as a solvent, A cyclic ether type solvent, a chain ether type solvent, a nitrile type solvent, a hydrocarbon type solvent, etc. are mentioned. Examples of the cyclic ether-based solvent include tetrahydrofuran (hereinafter, abbreviated as THF or thf.), dioxane, and the like. As a chain ether type solvent, diethyl ether etc. are mentioned, for example. As a nitrile-type solvent, acetonitrile, propionitrile, etc. are mentioned, for example. As a hydrocarbon type solvent, aromatic hydrocarbons, such as toluene, saturated hydrocarbons, such as hexane, etc. are mentioned, for example.

In the method for producing ammonia of the present embodiment, the reaction temperature is preferably normal temperature (0 to 40°C). The reaction atmosphere does not need to be a pressurized atmosphere, and may be a normal pressure atmosphere. The reaction time is not particularly limited, but is usually set within a range of several minutes to several 10 hours.

In the ammonia production method of the present embodiment, the amount of the catalyst used may be appropriately within the range of 0.00001 to 0.1 equivalents relative to the reducing agent, preferably 0.0005 to 0.1 equivalents, and more preferably 0.005 to 0.01 equivalents. The amount of the proton source used is preferably 0.5 to 5 equivalents with respect to the reducing agent, but more preferably 1 to 2 equivalents.

In the method for producing ammonia according to the present embodiment, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy are exemplified as the lanthanoid metal used for the halide (II) of the lanthanoid metal. , Ho, Er, Tm, Yb, and Lu, among them, Sm is preferable. As the halogen, chlorine, bromine, and iodine can be mentioned, and among them, iodine is preferable. As the halide (II) of the lanthanoid metal, samarium (II) halide is preferable, and samarium (II) iodide is more preferable.

In addition, it goes without saying that the present invention is not limited to the above-described embodiments at all, and can be implemented in various forms as long as it falls within the technical scope of the present invention.

Example

Hereinafter, examples of the present invention will be described. In addition, the following examples do not limit the present invention at all.

[Experimental example 1-21]

Ammonia was produced from nitrogen molecules in the presence of a reducing agent and a proton source using a molybdenum complex (1a) (the chemical formula is shown in the column of Table 1) as a catalyst (Table 1). In the following experimental examples, when ammonia was generated in excess of 2 equivalents with respect to the molybdenum metal in the catalyst, it was determined that ammonia was catalytically generated. The molybdenum complex (1a) was synthesized with reference to a known document (Bull.Chem.Soc.Jpn.2017, vol.90, pp1111-1118).

[Table 1]

^aReducer benchmark ^bUsed 1mL of THF ^cNo catalyst ^dUsed CoCp* ₂ as reducing agent

In Experimental Example 1, under a nitrogen atmosphere at normal pressure, at room temperature, molybdenum complex (1a) (1.7 mg, 0.002 mmol) as a catalyst and SmI ₂ (thf) ₂ (solid crystal) as a reducing agent , 0.36 mmol, 180 equiv. to molybdenum) in tetrahydrofuran solution (6 mL), add ethylene glycol (20 μL, 0.36 mmol, 180 equiv., 1 equiv. (1 times mol) to reducing agent) as a hydrogen ion source , and then stirred for 18 hours. Then, potassium hydroxide aqueous solution (30 mass %, 5 mL) was added, it was distilled under reduced pressure, and the distillate was recovered with sulfuric acid aqueous solution (0.5 M, 10 mL). The amount of ammonia in the aqueous sulfuric acid solution was determined by the indophenol method (Analytical Chemstry, 1967, vol. 39, pp971-974). As a result, 43.8 equivalents of ammonia was produced with respect to the catalyst (molybdenum complex).

In Experimental Example 2-6, the amount of ethylene glycol used in Experimental Example 1 was set within a range of 0.5 to 5 equivalents relative to the reducing agent. As a result, it was found that the yield hardly changed when the amount of ethylene glycol used was 1 to 5 equivalents of the reducing agent. In addition, in Experimental Example 1, the amount of ammonia generated when the reaction time was 1 minute and 15 minutes was investigated, and the results were 35% and 62% based on the reducing agent, respectively, and the reaction was substantially completed in 15 minutes. The TOF calculated from this result was at most about 1300/h.

In Experimental Example 7, although the amount of the solvent in Experimental Example 1 was reduced to 1 mL, the reaction proceeded without problems.

In Experimental Example 8-12, the solvent in Experimental Example 1 was changed from THF to dioxane, acetonitrile, diethyl ether, toluene, and hexane. When these solvents are used, the yield is slightly lower than that of THF, but ammonia can be obtained catalytically. In addition, in Experimental Example 13, an experiment in which ethylene glycol was used as both a proton source and a solvent was performed. As a result, ammonia was 8% based on a reducing agent, and 4.9 equivalents were produced with respect to molybdenum. Therefore, it was confirmed that ammonia was catalytically generated even when ethylene glycol was used as a solvent.

In Experimental Examples 14 to 19, the proton source in Experimental Example 3 was changed from ethylene glycol to various alcohols (methanol, ethanol, isopropanol, tert-butanol, trifluoroethanol, and phenol). As a result, although the yield was slightly lower than that of ethylene glycol, it was confirmed that ammonia was catalytically produced.

In Experimental Example 20, the reaction was performed without using the molybdenum complex (1a) in Experimental Example 1, and as a result, ammonia was not produced. In Experimental Example 21, decamethylcobalocene was used as a reducing agent, and as a result, ammonia was not generated.

[Experimental example 22-29]

In Experimental Examples 22 to 29, instead of the catalyst of Example 1, various molybdenum complexes shown in Table 2 were used as catalysts to try to synthesize ammonia. The chemical formula of each catalyst is shown in the column of Table 2. In Experimental Example 29, 0.01 mmol of the catalyst was used. The results are shown in Table 2.

The molybdenum complex (1b) was synthesized with reference to a known document (Bull.Chem.Soc.Jpn.2017, vol.90, pp1111-1118). The molybdenum complexes (1c) and (2) were synthesized with reference to known documents (Nat. Chem. 2011, vol. 3, pp120-125). The molybdenum complex (3a) was synthesized with reference to a known document (Nat. Commun. 2017, vol. 8, Airticle No. 14874). The molybdenum complex (3b) was synthesized with reference to a known document (J.Am.Chem.Soc.2015, vol.137, pp5666-5669). The molybdenum complex (5a) was synthesized with reference to a known literature (Inorg. Chem. 1973, vol. 12, pp2544-2547). The molybdenum complex (5b) was synthesized with reference to a known literature (J.Am.Chem.Soc.1972, vol.94, pp110-114). The molybdenum complex (4) was synthesized as follows. To a THF solution (16 mL) of the molybdenum complex (1a) (0.2 mmol, 174.4 mg), under a nitrogen atmosphere of 1 atmosphere, pyridine (0.4 mmol, 38 μL) and water (0.4 mmol, 7 μL) were added, Stir at 50°C for 14 hours. Then, the reaction solution was concentrated to dryness under vacuum, and the solid was washed with benzene (5 mL, 3 times). Then, the residue was extracted with THF (5 mL, twice), and concentrated to dryness under vacuum. The solid was dissolved in dichloromethane (4 mL), filtered through Celite, and then added with hexane (20 mL), followed by recrystallization for 4 days to obtain 46.1 mg (0.059 mmol, 30% yield) as pale yellow crystals. 4 (molybdenum complex (4)).

[Table 2]

^aReducing agent benchmark ^b 0.01 mmol catalyst used

In Experimental Examples 22 to 23, molybdenum complexes (1b) to (1c) having PNP ligands were used as catalysts. It was found that ammonia is catalytically generated regardless of whether X of the molybdenum complexes (1b) to (1c) is any one of an iodine atom, a bromine atom, and a chlorine atom.

In Experimental Examples 24 to 27, as catalysts, a dinuclear molybdenum complex (2) having a PNP ligand, a molybdenum complex (3a) having a PCP ligand, and a molybdenum having a PPP ligand were used Coordination compound (3b) and Mo(IV) oxo coordination compound (4) with PNP ligands. It was found that ammonia was catalytically produced regardless of the use of any of the molybdenum complexes (2), (3a), (3b), and (4). Among them, especially the molybdenum complex (3a) gave good results.

In Experimental Examples 28 to 29, mononuclear molybdenum complexes (5a) to (5b) were used as catalysts. It was found that ammonia was catalytically generated regardless of the use of the trans-type mononuclear molybdenum complexes (5a) and (5b).

[Experimental example 30]

Experimental Example 30 is an example using water as a proton source (refer to the following formula). A THF solution (4 mL) of a molybdenum complex (1a) (0.002 mmol) and SmI ₂ (thf) ₂ (solid crystal, 0.36 mmol, 180 equiv. to molybdenum), under a nitrogen atmosphere of 1 atm, A THF solution (2 mL) of water (0.36 mmol, 180 equiv with respect to molybdenum) was added dropwise with stirring at room temperature using a syringe pump over 0.5 hours. After completion of the dropwise addition, the mixture was further stirred at room temperature for 17.5 hours, and then the quantitative determination of ammonia and hydrogen was performed. As a result, 43% of ammonia (26.8 equivalents with respect to molybdenum) and 39% of hydrogen (36.0 equivalents with respect to molybdenum) were produced. Therefore, it was found that ammonia was catalytically generated even when water was used as a proton source.

[Experimental example 31-38]

In Experimental Examples 31-38, using a molybdenum complex as a catalyst, ammonia was produced from nitrogen molecules in THF at room temperature in the presence of a reducing agent (SmI ₂ ) and a proton source (Table 3). In Experimental Example 31, the reaction was carried out using a molybdenum complex (1a) having a PNP ligand as a catalyst and diethylene glycol as a proton source. In Experimental Examples 32 to 37, the reaction was carried out using a molybdenum complex (3a) having a PCP ligand as a catalyst and using diethylene glycol as a proton source. In Experimental Example 38, the reaction was performed using a molybdenum complex (3a) having a PCP ligand as a catalyst and water as a proton source. The results are shown in Table 3.

[table 3]

多个实验(至少2例)的平均。*Based on the yield of SmI ₂ (thf) ₂ .

Average of multiple experiments (at least 2 cases).

# THF (2 mL) was used as solvent. § Using _H2O as the proton source.

From the results of Experimental Example 31 and Experimental Example 32, it is understood that the molybdenum complex compound (3a) having a PCP ligand has higher catalytic activity than the molybdenum complex (1a) having a PNP ligand. As can be seen from the results of Experimental Examples 32 to 37, when the molybdenum complex (3a) was used as a catalyst and diethylene glycol was used as a proton source, ammonia was obtained at a high rate. From the results of Experimental Example 33 and Experimental Example 38, when the molybdenum complex (3a) having a PNP ligand was used as the catalyst, the proton source was compared with the use of diethylene glycol when water was used. Ammonia is obtained at a higher rate. In addition, among the experimental examples shown in this specification, the experimental example 38 obtained the best results.

[Experimental example 39-41]

In Experimental Examples 39 to 41, using molybdenum complexes as catalysts, ammonia was produced from nitrogen molecules in THF at room temperature in the presence of a reducing agent (SmI ₂ ) and a proton source (H ₂ O) (Table 4 ). In Experimental Example 39, the above-mentioned molybdenum complex (3a) was used as a catalyst, and in Experimental Example 40, a molybdenum complex (3c) having a fluorine atom at the 5 and 6 positions of the benzimidazole carbene ring was used as a catalyst, In Experimental Example 41, the reaction was performed using a molybdenum complex (3d) having a trifluoromethyl group at the 5-position of the benzimidazocarbene ring as a catalyst.

As a representative example, Experimental Example 41 will be described. For a solution (2 mL) of molybdenum complex (3d) (0.025 μmol) and SmI ₂ (thf) ₂ (solid crystal, 1.44 mmol, 57600 equiv. to molybdenum) in THF, under a nitrogen atmosphere of 1 atm, in A THF solution (1 mL) of water (1.44 mmol, 57600 equiv with respect to molybdenum) was added at room temperature, followed by stirring at room temperature for 22 hours. Then, the gas phase was analyzed by gas chromatography (GC) to quantify hydrogen, and as a result, 4700 equivalents of hydrogen was produced with respect to the catalyst (molybdenum complex). An aqueous potassium hydroxide solution (30% by mass, 5 mL) was added, and the mixture was distilled under reduced pressure, and the distillate was recovered with an aqueous sulfuric acid solution (0.5 M, 10 mL). The amount of ammonia in the aqueous sulfuric acid solution was determined by the indophenol method (Analytical Chemstry, 1967, vol. 39, pp971-974). As a result, 16,000 equivalents of ammonia was produced with respect to the catalyst (molybdenum complex). In Experimental Examples 39 and 40, the reaction was carried out in the same manner as in Experimental Example 41, except that the molybdenum complexes (3a) and (3c) were used instead of the molybdenum complex (3d). The results are shown in Table 4. As can be seen from Table 4, regarding the catalytic activity, the catalytic activities of the molybdenum complexes (3c) and (3d) are higher than those of the molybdenum complex (3a), and the molybdenum complex is higher than that of the molybdenum complex (3c). The catalytic activity of (3d) is higher.

[Table 4]

*Based on the yield of SmI ₂ (thf) ₂ .

Here, the synthesis procedure of the molybdenum complex (3d) used in Experimental Example 41 will be described below with reference to the following scheme.

· Synthesis of compound 1

The synthesis of compound 1 is shown below. Di-tert-butylphosphine (2.25 g, 14.9 mmol) and paraformaldehyde (450 mg, 15.0 mmol) were stirred at 60°C for 16 hours under nitrogen atmosphere. Then, 150 mL of dichloroethane and 1,2-diamino-4-trifluoromethylbenzene (1.06 g, 6.02 mmol) were added, and the mixture was stirred at 60° C. for 24 hours under a nitrogen atmosphere. Then, selenium (1.26 g, 16.0 mmol) was added and stirred at room temperature for 24 hours under nitrogen atmosphere. The reactant was concentrated, and the obtained solid was separated by silica gel column chromatography (dichloromethane:hexane=1/1). The recovered fractions were concentrated, dried under vacuum to solidify to isolate Compound 1 as a white solid as 2.48 g (3.81 mmol, 63% yield). ¹ H NNR (CDCl ₃ ): δ 7.08 (d, J=8.4Hz, 1H), 6.81 (s, 1H), 6.66 (d, J=8.4Hz, 1H), 5.01-4.99 (m, 1H), 4.81-4.77 (m, 1H), 3.39-3.33 (m, 4H), 1.45 (d, J=15.2Hz, 18H), 1.43 (d, J=15.2Hz, 18H), ³¹ P NMR (CDCl ₃ ): delta 79.9(s), 79.6(s).

· Synthesis of compound 2

The synthesis of compound 2 is shown below. Compound 1 (2.48 g, 3.81 mmol), triethyl orthoformate (10 mL), ammonium hexafluorophosphate (629 mg, 3.86 mmol) were stirred at 120° C. for 3 hours under air. Then, it was concentrated and washed with CH ₂ Cl ₂ /Et ₂ O mixed solution (4 mL/8 mL×2), Et ₂ O (10 mL×1). Drying under vacuum isolated compound 2 as a white solid as 2.58 g (3.20 mmol, 84% yield). ¹ H NNR (CDCl ₃ ): δ 10.13 (s, 1H), 8.16 (s, 1H), 8.11 (d, J=8.4 Hz, 1H), 7.89 (d, J=8.4 Hz, 1H), 5.08- 5.04 (m, 4H), 1.48 (d, J=16.0 Hz, 18H), 1.47 (d, J=16.4 Hz, 18H), ³¹ P NMR (CDCl ₃ ): δ 81.7 (s), 80.7 (s) , -135.1～-152.7(m).

· Synthesis of compound 3

The synthesis of compound 3 is shown below. Compound 3 (2.58 g, 3.20 mmol), tris(dimethylamino)phosphine (1.5 mL) in dichloromethane (40 mL) were stirred at room temperature for 4 hours under nitrogen atmosphere. Then, it was concentrated and washed with toluene (7 mL×3), dried under vacuum, and compound 3 was isolated as a white solid as 1.66 g (2.56 mmol, 80% yield). ¹ H NNR (CDCl ₃ ): δ 9.81 (s, 1H), 8.27 (s, 1H), 8.15 (d, J=8.4 Hz, 1H), 7.88 (d, J=8.4 Hz, 1H), 4.72- 4.70 (m, 4H), 1.23 (d, J=12.0 Hz, 18H), 1.21 (d, J=12.0 Hz, 18H), ³¹ P NMR (CDCl ₃ ): δ 25.9 (s), 25.1 (s) , -139.4～-152.6(m).

· Synthesis of Molybdenum Coordination Compound (3d)

The synthesis of the molybdenum complex (3d) is shown below. Compound 3 (1.30 g, 2.00 mmol), bis(trimethylsilyl)amide potassium salt (561 mg, 2.81 mmol) in toluene (45 mL) was stirred at room temperature for 1 hour under an argon atmosphere. Then, after filtering using Celite, MoCl ₃ (thf) ₃ (756 mg, 1.81 mmol) was added, and the mixture was stirred at 80° C. for 26 hours. The reaction solution was concentrated to 5 mL, filtered using filter paper and dried under vacuum to solidify. The obtained solid was washed with toluene (5 mL×2), dissolved in CH ₂ Cl ₂ (20 mL), and filtered using Celite. Hexane (30 mL) was slowly added to the filtrate, and it was allowed to stand for 5 days to form brown crystals. The supernatant was removed, washed with hexane (5 mL×3), and dried under vacuum to isolate the molybdenum complex (3d) as brown crystals as 381 mg (0.54 mmol, 30% yield). _{Anal.Calcd.for C26H43N2F3P2Cl3Mo · 1} / _{2CH2Cl2 :} C, _{42.59 ;} H, 5.93; N, 3.75 Found: C, 42.79; H, 5.74; N, 3.91 .

The molybdenum complex (3c) used in Experimental Example 40 can be obtained by using 1,2-diamino-4-trifluoromethylbenzene instead of 1,2-diamino-4-trifluoromethylbenzene in the synthesis scheme of the molybdenum complex (3d). Amino-4,5-difluorobenzene was synthesized.

[Experimental Example 42]

In Experimental Example 42, the scale was enlarged to produce ammonia. In a 1000 mL four-necked flask, THF relative to platinum complex (3a) (0.100 mmol, 63.8 mg) and SmI ₂ (thf) ₂ (solid crystal, 36.0 mmol, 19.7 g, 360 equivalent to platinum) A solution (270 mL) was added to a THF solution (20 mL) of water (36.0 mmol, 360 equiv with respect to platinum) at room temperature under nitrogen flow while stirring with a mechanical stirrer (220 rpm), followed by stirring at room temperature for 8 minute. The reaction solution was concentrated, dried and solidified by an evaporator. Potassium hydroxide aqueous solution (30 mass %, 20 mL) was added to the obtained solid, the distillation was carried out under reduced pressure, and the distillate was recovered with an aqueous solution (about 10 mL) of 96% concentrated sulfuric acid (5.04 mmol, 515 mg). The recovered aqueous solution was concentrated by an evaporator and dried under vacuum overnight. As a result, a white solid of (NH ₄ ) ₂ SO ₄ was obtained at 668 mg (5.06 mmol, 84% yield). This corresponds to the generation of 101 equivalents of ammonia relative to the catalyst (molybdenum complex). _{Anal.Calcd.forH8N2O4S} : H, 6.10; N, _21.20 Found: H, 6.06; N, _20.98 .

In addition, the experimental examples 1-19, 22-42 correspond to the Example of this invention, and the experimental examples 20 and 21 correspond to the comparative example.

This application claims priority on the basis of Japanese Patent Application No. 2018-36967 filed on March 1, 2018 and Japanese Patent Application No. 2018-158595 filed on August 27, 2018, all of which are hereby incorporated by reference. The contents are contained in this manual.

industry availability

The present invention can be used for the production of ammonia.

Claims (11)

1. A process for producing ammonia from a nitrogen molecule in the presence of a catalyst, a reducing agent and a proton source,

the catalyst is (A) a molybdenum complex compound having 2, 6-bis (dialkylphosphinomethyl) pyridine as a PNP ligand, (B) a molybdenum complex compound having N, N-bis (dialkylphosphinomethyl) benzimidazolecarbonine as a PCP ligand, (C) a molybdenum complex compound having bis (dialkylphosphinoethyl) arylphosphine as a PPP ligand, or (D) trans-Mo (N₂)₂(R¹R²R³P)₄The molybdenum complex compound represented by the formula (I), wherein 2 alkyl groups in the 2, 6-bis (dialkylphosphinomethyl) pyridine may be the same or different, at least 1 hydrogen atom of the pyridine ring may be substituted by an alkyl group, an alkoxy group or a halogen atom, 2 alkyl groups in the N, N-bis (dialkylphosphinomethyl) benzimidazole carbene may be the same or different, at least 1 hydrogen atom of the benzene ring may be substituted by an alkyl group, an alkoxy group or a halogen atom, 2 alkyl groups in the bis (dialkylphosphinoethyl) arylphosphine may be the same or different, and the trans-Mo (N, 6-bis (dialkylphosphinomethyl) pyridine₂)₂(R¹R²R³P)₄In, R¹、R²、R³Is an alkyl or aryl group which may be the same or different, 2R³Can be linked to each other to form an alkylene chain,

as reducing agent, a halide (II) of a lanthanide metal is used,

as the proton source, alcohol or water is used.

2. The method for producing ammonia according to claim 1, wherein the molybdenum complex compound of (A) is a molybdenum complex compound represented by the following formula (A1), (A2) or (A3),

in the formula, R¹And R²Is an alkyl group which may be the same or different, X is an iodine atom, a bromine atom or a chlorine atom, and at least 1 hydrogen atom on the pyridine ring may be substituted by an alkyl group, an alkoxy group or a halogen atom.

3. The process for producing ammonia according to claim 1, wherein the molybdenum complex compound of the formula (B) is a molybdenum complex compound represented by the following formula (B1),

in the formula, R¹And R²Is an alkyl group which may be the same or different, X is an iodine atom, a bromine atom or a chlorine atom, and at least 1 hydrogen atom on the benzene ring may be substituted by an alkyl group, an alkoxy group or a halogen atom.

4. The method for producing ammonia according to claim 3, wherein at least one of the 5-position and the 6-position of the benzimidazole carbene ring of the formula (B1) is substituted with a trifluoromethyl group.

5. The method for producing ammonia according to claim 1, wherein the molybdenum complex compound of formula (C) is a molybdenum complex compound represented by formula (C1),

in the formula, R¹And R²Is an alkyl group which may be the same or different，R³Is aryl, and X is iodine atom, bromine atom or chlorine atom.

6. The method for producing ammonia according to claim 1, wherein the molybdenum complex compound of (D) is a molybdenum complex compound represented by formula (D1) or (D2),

in the formula, R¹、R²And R³Is an alkyl or aryl group which may be the same or different, and n is 2 or 3.

7. The method for producing ammonia according to any one of claims 1 to 6, wherein nitrogen gas at normal pressure is used as the nitrogen molecules.

8. The method for producing ammonia according to any one of claims 1 to 7, wherein the alcohol is a diol or ROH, and R is a C1-6 linear, cyclic or branched alkyl group whose hydrogen atom may be substituted with a fluorine atom, or a phenyl group which may have an alkyl group.

9. The method for producing ammonia according to any one of claims 1 to 8, wherein the halide (II) of a lanthanoid metal is a samarium (II) halide.

10. A molybdenum complex compound represented by the formula (B2),

in the formula, R¹And R²Is an alkyl group which may be the same or different, X is an iodine atom, a bromine atom or a chlorine atom, R is³And R⁴At least one of which is substituted with trifluoromethyl.

11. A benzimidazole compound represented by the formula (E),

wherein A is an anion, R¹And R²Are alkyl groups which may be the same or different, R³And R⁴At least one of which is substituted with trifluoromethyl.