WO2019168093A1

WO2019168093A1 - Ammonia manufacturing method, molybdenum complex, and benzimidazole compound

Info

Publication number: WO2019168093A1
Application number: PCT/JP2019/007793
Authority: WO
Inventors: 仁昭西林; 一成中島; 裕也芦田; 一隆的場; 章一近藤; 隆正菊池
Original assignee: 国立大学法人東京大学; 日産化学株式会社
Priority date: 2018-03-01
Filing date: 2019-02-28
Publication date: 2019-09-06
Also published as: CN111801297B; JP7318871B2; JPWO2019168093A1; CN111801297A

Abstract

The ammonia manufacturing method according to the present invention is for producing ammonia from nitrogen molecules in the presence of a catalyst, a reducing agent, and a proton source. Examples of usable catalysts include molybdenum complexes such as [MoI₃(PNP)] (PNP being 2,6-bis(di-tert-butylphosphinomethyl)pyridine). Samarium iodide (II) is used as the reducing agent, and an alcohol or water is used as the proton source.

Description

Method for producing ammonia, molybdenum complex and benzimidazole compound

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

The Harbor Bosch method, which is an industrial method for converting nitrogen molecules into ammonia, is an energy-intensive process that requires 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, in Non-Patent Document 1, as shown in the following formula, toluene of a molybdenum iodo complex having a PNP ligand as a catalyst and 2,4,6-collidinium trifluoromethanesulfonate as a proton source is used. To the solution, a toluene solution of decamethylcobaltene as a reducing agent was added at room temperature in the presence of atmospheric nitrogen gas, and then stirred to produce 415 equivalents of ammonia based on a molybdenum complex as a catalyst. It is reported.

However, in the above-mentioned Non-Patent Document 1, it is necessary to use a stoichiometric amount of expensive decamethylcobaltcene or collidine conjugate acid. For this reason, development of a cheaper method for producing ammonia has been expected from an industrial viewpoint.

The present invention has been made to solve the above-described problems, and has as its main object to produce ammonia from nitrogen molecules at a relatively low cost.

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

That is, the method for producing ammonia of the present invention comprises:
A process for producing ammonia from nitrogen molecules in the presence of a catalyst, a reducing agent and a proton source,
The catalyst comprises (A) 2,6-bis (dialkylphosphinomethyl) pyridine as a PNP ligand (wherein the two alkyl groups may be the same or different, and at least one hydrogen atom of the pyridine ring is an alkyl group). A molybdenum complex having an alkyl group, an alkoxy group or a halogen atom, and (B) N, N-bis (dialkylphosphinomethyl) dihydrobenzimidazolidene as a PCP ligand (however, 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), (C) Bis (dialkyl as a PPP ligand) Phosphinoethyl) arylphosphine (where the two alkyl groups may be the same or different) ) Molybdenum complexes with, or, (D) trans-Mo ( N 2) 2 (R 1 R 2 R 3 P) 4 ( ^{^{where, R 1, R 2, R}} 3 is an alkyl group which may be the same or different Or an aryl group, and two R ^{3 s} may be linked to each other to form an alkylene chain),
As the reducing agent, a lanthanoid metal halide (II) is used,
As the proton source, alcohol or water is used.

According to this ammonia production method, alcohol or water can be used as a proton source, and the reaction proceeds even at room temperature (0 to 40 ° C.), so that ammonia can be produced from nitrogen molecules at a lower cost than conventional methods. Can do.

A preferred embodiment of the method for producing ammonia of the present invention is shown below.

The ammonia production method of this 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, (A) 2,6-bis (dialkylphosphinomethyl) pyridine as a PNP ligand (wherein the two alkyl groups may be the same or different, and at least one hydrogen in the pyridine ring) Molybdenum complex having an atom which may be substituted with an alkyl group, an alkoxy group or a halogen atom, (B) N, N-bis (dialkylphosphinomethyl) dihydrobenzimidazolidene as a PCP ligand (provided that 2 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), (C) as a PPP ligand Bis (dialkylphosphinoethyl) arylphosphine (however, the two alkyl groups may be the same or different Molybdenum complexes having had may be) I, or, (D) trans-Mo ( N 2) 2 (R 1 R 2 R 3 P) 4 ( ^{^{where, R 1, R 2, R}} 3 are the same or different from each other An alkyl group or an aryl group, and two R ³ may be linked to each other to form an alkylene chain). Further, the lanthanoid metal halide (II) is used as the reducing agent, and alcohol or water is used as the proton source.

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

As the molybdenum complex of (A), for example, the formula (A1), (A2) or (A3)

Wherein R ¹ and R ² are the same or different alkyl groups, X is an iodine atom, bromine atom or chlorine atom, and at least one hydrogen atom on the pyridine ring is an alkyl group , An molybdenum group which may be substituted with an alkoxy group or a halogen atom). Examples of the alkyl group, alkoxy group and halogen atom are the same as those already exemplified. R ¹ and R ² are preferably bulky alkyl groups (for example, tert-butyl group or isopropyl group). It is preferable that the hydrogen atom on the pyridine ring is not substituted, or the hydrogen atom at the 4-position is substituted with a chain, cyclic or branched alkyl group having 1 to 12 carbon atoms.

As the molybdenum complex of (B), for example, the formula (B1)

Wherein R ¹ and R ² are the same or different alkyl groups, X is an iodine atom, bromine atom or chlorine atom, and at least one hydrogen atom on the benzene ring is an alkyl group , An molybdenum group which may be substituted with an alkoxy group or a halogen atom). Examples of the alkyl group, alkoxy group and halogen atom are the same as those already exemplified. R ¹ and R ² are preferably bulky alkyl groups (for example, tert-butyl group or isopropyl group). It is preferable that the hydrogen atom on the benzene ring is not substituted, 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. In particular, a molybdenum complex of the formula (B2) is preferable. Wherein ^{(B2), R 1, R} 2 and X are as defined in the formula (B1), preferably at least one of R ³ and R ⁴ is substituted with a fluoro group, further R ³ and R ⁴ More preferably, at least one is substituted with a trifluoromethyl group. The benzimidazole compound of the formula (E) can be used as an intermediate for synthesizing the molybdenum complex of the 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). The anion of A is not particularly limited, and examples thereof include PF ₆ ⁻ , BF ₄ ⁻ , ClO ₄ ^{− and the} like.

As the molybdenum complex of (C), for example, the formula (C1)

(Wherein R ¹ and R ² are the same or different alkyl groups, R ³ is an aryl group, and X is an iodine atom, bromine atom or chlorine atom). A molybdenum complex is mentioned. Examples of the alkyl group include those already exemplified. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a group in which at least one of the hydrogen atoms on the ring is substituted with an alkyl group or a halogen atom. Examples of the alkyl group and halogen atom are the same as those already exemplified. R ¹ and R ² are preferably bulky alkyl groups (for example, tert-butyl group or isopropyl group). As R ³ , for example, a phenyl group is preferable.

As the molybdenum complex of (D), the formula (D1) or (D2)

(Wherein R ¹ , R ² and R ³ are alkyl groups or aryl groups which may be the same or different, and n is 2 or 3). Examples of the alkyl group and aryl group are the same as those already exemplified. In the formula (D1), R ¹ and R ² are aryl groups (eg, phenyl groups) and R ³ is an alkyl group having 1 to 4 carbon atoms (eg, methyl group), or R ¹ and R ² are 1 to 4 carbon atoms. It is preferable that R ³ is an aryl group (for example, a phenyl group) in 4 alkyl groups (for example, a methyl group). In the formula (D2), it is preferable that R ¹ and R ² are an aryl group (for example, a phenyl group) and n is 2.

In the ammonia production method of the present embodiment, it is preferable to use nitrogen gas at normal pressure as nitrogen molecules. Nitrogen gas is inexpensive and may be used in a large excess relative to other reagents.

In the method for producing ammonia of the present embodiment, when alcohol is used as the proton source, glycol may be used as the alcohol, or ROH (where R is a carbon atom having a hydrogen atom substituted with a fluorine atom and having 1 to 6 carbon atoms). A linear, cyclic or branched alkyl group, or a phenyl group which may have an alkyl group). Examples of the glycol include ethylene glycol, propylene glycol, and diethylene glycol. Among these, ethylene glycol is preferable. Examples of ROH include chain or branched alkyl alcohols such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol; cyclopropanol, cyclopentanol, cyclohexanol, etc. Cyclic alkyl alcohols of the following: alcohols containing fluorine atoms such as trifluoroethyl alcohol and tetrafluoroethyl alcohol; phenol derivatives such as phenol, cresol and xylenol.

In the ammonia production method of the present embodiment, ammonia may be produced from nitrogen molecules in a solvent. Examples of the solvent include, but are not limited to, cyclic ether solvents, chain ether solvents, nitrile solvents, hydrocarbon solvents, and the like. Examples of the cyclic ether solvent include tetrahydrofuran (hereinafter abbreviated as THF or thf), dioxane, and the like. Examples of the chain ether solvent include diethyl ether. Examples of the nitrile solvent include acetonitrile and propionitrile. Examples of the hydrocarbon solvent include aromatic hydrocarbons such as toluene and saturated hydrocarbons such as hexane.

In the method for producing ammonia of this embodiment, the reaction temperature is preferably room 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 in the range of several minutes to several tens of hours.

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

In the ammonia production method of the present embodiment, the lanthanoid metal used for the lanthanoid metal halide (II) includes La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu are mentioned, among which Sm is preferable, and halogen includes chlorine, bromine, and iodine, and among these, iodine is preferable. The halide (II) of the lanthanoid metal is preferably samarium (II) halide, and more preferably samarium (II) iodide.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

Hereinafter, examples of the present invention will be described. The following examples do not limit the present invention.

[Experimental 1-21]
Using molybdenum complex (1a) (the chemical formula is shown in the column of Table 1) as a catalyst, ammonia was produced from nitrogen molecules in the presence of a reducing agent and a proton source (Table 1). In the following experimental examples, it was determined that ammonia was generated catalytically when more than 2 equivalents of ammonia was generated per molybdenum metal in the catalyst. The molybdenum complex (1a) was synthesized with reference to known literature (Bull. Chem. Soc. Jpn. 2017, vol. 90, pp1111-1118).

In Experimental Example 1, molybdenum complex (1a) (1.7 mg, 0.002 mmol) as a catalyst and SmI ₂ (thf) ₂ (solid crystal, 0. To a tetrahydrofuran solution (6 mL) of 36 mmol, 180 equivalents to molybdenum), ethylene glycol as a hydrogen ion source (20 μL, 0.36 mmol, 180 equivalents, 1 equivalent (1 mole) to the reducing agent) was added, The mixture was then stirred for 18 hours. Then, potassium hydroxide aqueous solution (30 mass%, 5 mL) was added and distilled under reduced pressure conditions, and the distillate was recovered with sulfuric acid aqueous solution (0.5 M, 10 mL). The amount of ammonia in the sulfuric acid aqueous solution was determined by the indophenol method (Analytical Chemstry, 1967, vol. 39, pp971-974). As a result, 43.8 equivalents of ammonia was produced per catalyst (molybdenum complex).

In Experimental Example 2-6, the amount of ethylene glycol used in Experimental Example 1 was set between 0.5 and 5 equivalents with respect to the reducing agent. As a result, it was found that when the amount of ethylene glycol used was 1 to 5 equivalents relative to the reducing agent, there was almost no change in yield. In Experimental Example 1, when the amount of ammonia generated when the reaction time was 1 minute and 15 minutes was examined, it was 35% and 62%, respectively, based on the reducing agent, and the reaction was almost completed in 15 minutes. The maximum TOF calculated from this result was about 1300 / h.

In Experimental Example 7, the amount of solvent was reduced to 1 mL in Experimental Example 1, but 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 were used, ammonia could be obtained catalytically, although the yield was slightly lower than that of THF. In Experimental Example 13, an experiment was conducted using ethylene glycol as both a proton source and a solvent. As a result, ammonia was generated in an amount of 8% based on the reducing agent and 4.9 equivalents relative to molybdenum. From this, it was confirmed that ammonia was produced catalytically even when ethylene glycol was used as a solvent.

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

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

[Experimental Examples 22-29]
In Experimental Examples 22-29, synthesis of ammonia was attempted using various molybdenum complexes shown in Table 2 as catalysts instead of the catalyst of Example 1. The chemical formula of each catalyst is shown in the column of Table 2. In Experimental Example 29, 0.01 mmol of catalyst was used. The results are shown in Table 2.

The molybdenum complex (1b) was synthesized with reference to known literature (Bull. Chem. Soc. Jpn. 2017, vol. 90, pp1111-1118). Molybdenum complexes (1c) and (2) were synthesized with reference to known literature (Nat. Chem. 2011, vol. 3, pp120-125). The molybdenum complex (3a) was synthesized with reference to known literature (Nat. Commun. 2017, vol. 8, Airticle No. 14874). The molybdenum complex (3b) was synthesized with reference to known literature (J. Am. Chem. Soc. 2015, vol. 137, pp5666-5669). The molybdenum complex (5a) was synthesized with reference to known literature (Inorg. Chem. 1973, vol. 12, pp2544-2547). The molybdenum complex (5b) was synthesized with reference to 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), pyridine (0.4 mmol, 38 μL) and water (0.4 mmol, 7 μL) were added under a nitrogen atmosphere of 1 atm. And stirred at 50 ° C. for 14 hours. Thereafter, the reaction solution was concentrated to dryness under vacuum, and the solid was washed with benzene (5 mL, 3 times). The residue was then extracted with THF (5 mL, 2 times) and concentrated to dryness under vacuum. Dissolve the solid in dichloromethane (4 mL), add hexane (20 mL) after celite filtration, and recrystallize for 4 days to obtain 46.1 mg (0.059 mmol, 30% yield) as pale yellow crystals. It was.

In Experimental Examples 22-23, molybdenum complexes (1b) to (1c) having PNP ligands were used as catalysts. It has been found that ammonia is produced catalytically regardless of whether X in the molybdenum complexes (1b) to (1c) is an iodine atom, a bromine atom or a chlorine atom.

In Experimental Examples 24-27, as a catalyst, a binuclear molybdenum complex (2) having a PNP ligand, a molybdenum complex (3a) having a PCP ligand, a molybdenum complex (3b) having a PPP ligand, and a PNP ligand are used. Mo (IV) oxo complex (4) having a ligand was used. It was found that ammonia was produced catalytically when any of the molybdenum complexes (2), (3a), (3b), and (4) was used. Of these, the molybdenum complex (3a) gave particularly good results.

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

[Experiment 30]
Experimental Example 30 is an example using water as a proton source (see the following formula). A solution of molybdenum complex (1a) (0.002 mmol) and SmI ₂ (thf) ₂ (solid crystals, 0.36 mmol, 180 equivalents to molybdenum) in THF (4 mL) at room temperature under a nitrogen atmosphere of 1 atm. The solution was stirred while adding dropwise a THF solution (2 mL) of water (0.36 mmol, 180 equivalents relative to molybdenum) over 0.5 hour using a syringe pump. After completion of the dropwise addition, the mixture was further stirred for 17.5 hours at room temperature, and then ammonia and hydrogen were quantified. As a result, 43% ammonia (26.8 equivalents relative to molybdenum) and 39% hydrogen (36.0 equivalents relative to molybdenum) were produced. From this, it was found that ammonia was produced catalytically even when water was used as the proton source.

[Experimental Examples 31-38]
In Experimental Examples 31-38, ammonia was produced from nitrogen molecules at room temperature in THF in the presence of a reducing agent (SmI ₂ ) and a proton source using a molybdenum complex as a catalyst (Table 3). In Experimental Example 31, the reaction was performed using 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 performed using molybdenum complex (3a) having a PCP ligand as a catalyst and 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.

From the results of Experimental Example 31 and Experimental Example 32, it was found that the molybdenum complex (3a) having a PCP ligand has higher catalytic activity than the molybdenum complex (1a) having a PNP ligand. From the results of Experimental Examples 32-37, it was found that ammonia was obtained at a high rate when molybdenum complex (3a) was used as a catalyst and diethylene glycol was used as a proton source. From the results of Experimental Example 33 and Experimental Example 38, when the molybdenum complex (3a) having a PNP ligand is used as a catalyst, ammonia is obtained at a higher rate when water is used than when diethylene glycol is used as a proton source. I understood it. Of the experimental examples shown in this specification, Experimental Example 38 gave the best results.

[Experimental Examples 39-41]
In Experimental Examples 39-41, ammonia was produced from nitrogen molecules at room temperature in THF in the presence of a reducing agent (SmI ₂ ) and a proton source (H ₂ O) using a molybdenum complex as a catalyst (Table 4). In Experimental Example 39, the molybdenum complex (3a) described above as a catalyst, in Experimental Example 40, the molybdenum complex (3c) having a fluorine atom at the 5th and 6th positions of the dihydrobenzimidazolidene ring as a catalyst, and in Experimental Example 41, the catalyst The reaction was carried out using a molybdenum complex (3d) having a trifluoromethyl group at the 5-position of the dihydrobenzimidazolidene ring.

As a representative example, Experimental Example 41 will be described. A solution of molybdenum complex (3d) (0.025 μmol) and SmI ₂ (thf) ₂ (solid crystals, 1.44 mmol, 57600 equivalents to molybdenum) in THF (2 mL) at room temperature under a nitrogen atmosphere of 1 atm. After adding water (1.44 mmol, 57600 equivalent to molybdenum) in THF (1 mL), the mixture was stirred at room temperature for 22 hours. Thereafter, the gas phase was analyzed by gas chromatography (GC) and the amount of hydrogen was determined. As a result, 4700 equivalents of hydrogen per catalyst (molybdenum complex) were produced. An aqueous potassium hydroxide solution (30% by mass, 5 mL) was added and 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 sulfuric acid aqueous solution was determined by the indophenol method (Analytical Chemstry, 1967, vol. 39, pp971-974). As a result, 16000 equivalents of ammonia was produced per catalyst (molybdenum complex). In Experimental Examples 39 and 40, the reaction was performed 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. Table 4 shows that the catalytic activity is higher in the molybdenum complexes (3c) and (3d) than in the molybdenum complex (3a) and higher in the molybdenum complex (3d) than in the molybdenum complex (3c). It was.

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 | combination of compound 1 The synthesis | combination 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 a nitrogen atmosphere. Thereafter, 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. Thereafter, selenium (1.26 g, 16.0 mmol) was added, and the mixture was stirred at room temperature for 24 hours under a nitrogen atmosphere. The reaction product was concentrated, and the resulting solid was separated by silica gel column chromatography (dichloromethane: hexane = 1/1). The collected fractions were concentrated and dried under vacuum to isolate Compound 1 as a white solid in 2.48 g (3.81 mmol, 63% yield). ¹ H NNR (CDCl ₃ ): δ 7.08 (d, J = 8.4 Hz, 1H), 6.81 (s, 1H), 6.66 (d, J = 8.4 Hz, 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 = 15.2 Hz, 18H), ³¹ P NMR (CDCl ₃ ): δ 79.9 (s), 79.6 (s).

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

-Synthesis | combination of compound 3 The synthesis | combination of compound 3 is shown below. Compound 3 (2.58 g, 3.20 mmol) and tris (dimethylamino) phosphine (1.5 mL) were stirred in dichloromethane (40 mL) at room temperature for 4 hours under a nitrogen atmosphere. Thereafter, the mixture was concentrated, washed with toluene (7 mL × 3), and dried under vacuum, whereby Compound 3 was isolated as a white solid in 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 to −152.6 (m).

-Synthesis | combination of molybdenum complex (3d) The synthesis | combination of a molybdenum complex (3d) is shown below. Compound 3 (1.30 g, 2.00 mmol) and potassium bis (trimethylsilyl) amide (561 mg, 2.81 mmol) were stirred in toluene (45 mL) at room temperature under an argon atmosphere for 1 hour. Then, after filtration through _{_{celite, MoCl 3 (thf) 3 (}} 756mg, 1.81mmol) was added and stirred for 26 hours at 80 ° C.. The reaction solution was concentrated to 5 mL, filtered using filter paper, and dried under vacuum. The obtained solid was washed with toluene (5 mL × 2), dissolved in CH ₂ Cl ₂ (20 mL), and filtered through celite. Hexane (30 mL) was slowly added to the filtrate and allowed to stand for 5 days to produce 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 in 381 mg (0.54 mmol, 30% yield). Anal. Calcd. _{_{_{for C 26 H 43 N 2 F}}} 3 P 2 Cl 3 Mo · 1 / 2CH 2 Cl 2: 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 was replaced with 1,2-diamino-4,5-difluoro in place of 1,2-diamino-4-trifluoromethylbenzene in the synthesis scheme of the molybdenum complex (3d). It can be synthesized by using benzene.

[Experimental Example 42]
In Experimental Example 42, ammonia production was scaled up. THF of molybdenum complex (3a) (0.100 mmol, 63.8 mg) and SmI ₂ (thf) ₂ (solid crystals, 36.0 mmol, 19.7 g, 360 equivalents to molybdenum) in a 1000 mL 4-neck flask To a solution (270 mL), a THF solution (20 mL) of water (36.0 mmol, 360 equivalents to molybdenum) was added at room temperature under a nitrogen stream while stirring with a mechanical stirrer (220 rpm). Stir for minutes at room temperature. The reaction solution was concentrated to dryness with an evaporator. A potassium hydroxide aqueous solution (30% by mass, 20 mL) was added to the obtained solid and distilled under reduced pressure conditions, and the distillate was collected with an aqueous solution (about 10 mL) of 96% concentrated sulfuric acid (5.04 mmol, 515 mg). The recovered aqueous solution was concentrated with an evaporator and dried overnight under vacuum. As a result, 668 mg (5.06 mmol, 84% yield) of a white solid (NH ₄ ) ₂ SO ₄ was obtained. This corresponds to the production of 101 equivalents of ammonia per catalyst (molybdenum complex). Anal. Calcd. forH ₈ N ₂ O ₄ S: H, 6.10; N, 21.20 Found: H, 6.06; N, 20.98.

Note that Experimental Examples 1-19 and 22-42 correspond to examples of the present invention, and Experimental Examples 20 and 21 correspond to comparative examples.

This application is based on Japanese Patent Application No. 2018-36967 filed on Mar. 1, 2018 and Japanese Patent Application No. 2018-158595 filed on Aug. 27, 2018. The entire contents of which are incorporated herein by reference.

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

Claims

A process for producing ammonia from nitrogen molecules in the presence of a catalyst, a reducing agent and a proton source,
The catalyst comprises (A) 2,6-bis (dialkylphosphinomethyl) pyridine as a PNP ligand (wherein the two alkyl groups may be the same or different, and at least one hydrogen atom of the pyridine ring is an alkyl group). A molybdenum complex having an alkyl group, an alkoxy group or a halogen atom, and (B) N, N-bis (dialkylphosphinomethyl) dihydrobenzimidazolidene as a PCP ligand (however, 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), (C) Bis (dialkyl as a PPP ligand) Phosphinoethyl) arylphosphine (where the two alkyl groups may be the same or different) ) Molybdenum complexes with, or, (D) trans-Mo ( N 2) 2 (R 1 R 2 R 3 P) 4 ( where, R 1, R 2, R 3 is an alkyl group which may be the same or different Or an aryl group, and two R 3 s may be linked to each other to form an alkylene chain),
As the reducing agent, a lanthanoid metal halide (II) is used,
As the proton source, alcohol or water is used.
A method for producing ammonia.
The molybdenum complex of (A) is represented by the following formula (A1), (A2) or (A3)

Wherein R 1 and R 2 are the same or different alkyl groups, X is an iodine atom, bromine atom or chlorine atom, and at least one hydrogen atom on the pyridine ring is an alkyl group , Which may be substituted with an alkoxy group or a halogen atom).
The method for producing ammonia according to claim 1.
The molybdenum complex (B) has the following formula (B1)

Wherein R 1 and R 2 are the same or different alkyl groups, X is an iodine atom, bromine atom or chlorine atom, and at least one hydrogen atom on the benzene ring is an alkyl group , Which may be substituted with an alkoxy group or a halogen atom).
The method for producing ammonia according to claim 1.
At least one of the 5-position and the 6-position of the dihydrobenzimidazolidene ring of the formula (B1) is substituted with a trifluoromethyl group,
The method for producing ammonia according to claim 3.
The molybdenum complex of (C) has the formula (C1)

(Wherein R 1 and R 2 are the same or different alkyl groups, R 3 is an aryl group, and X is an iodine atom, bromine atom or chlorine atom). A molybdenum complex,
The method for producing ammonia according to claim 1.
The molybdenum complex of (D) has the formula (D1) or (D2)

Wherein R 1 , R 2 and R 3 are the same or different alkyl groups or aryl groups, and n is 2 or 3.
The method for producing ammonia according to claim 1.
As the nitrogen molecules, normal pressure nitrogen gas is used.
The method for producing ammonia according to any one of claims 1 to 6.
The alcohol is glycol or ROH (wherein R has a linear, cyclic or branched alkyl group having 1 to 6 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, or an alkyl group. An optionally substituted phenyl group),
The method for producing ammonia according to any one of claims 1 to 7.
The lanthanoid metal halide (II) is samarium (II) halide,
The method for producing ammonia according to any one of claims 1 to 8.
Formula (B2)

Wherein R 1 and R 2 are the same or different alkyl groups, X is an iodine atom, bromine atom or chlorine atom, and at least one of R 3 and R 4 is trifluoromethyl Molybdenum complex represented by the following:
Formula (E)

(Wherein A is an anion, R 1 and R 2 are the same or different alkyl groups, and at least one of R 3 and R 4 is substituted with a trifluoromethyl group) A benzimidazole compound represented by: