CN111801297B - Method for producing ammonia, molybdenum complex compound, and benzimidazole compound - Google Patents

Abstract

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

Description

Method for producing ammonia, molybdenum complex and benzimidazole compound

technical field

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

Background technique

The Haber-Bosch method, which is an industrial method for converting nitrogen molecules into ammonia, is an energy-intensive process requiring reaction conditions of high temperature and high pressure. In contrast, in recent years, a method for producing ammonia from nitrogen molecules under mild conditions has been developed. For example, in Non-Patent Document 1, it is reported that, as shown in the following formula, a molybdenum-iodide complex having a PNP ligand as a catalyst and 2,4,6-collidine trimethylpyridine as a proton source In the toluene solution of fluoromethanesulfonate, in the presence of nitrogen at normal pressure, add the toluene solution of decamethyldicyclocenecobalt as a reducing agent at room temperature, and then stir, 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

Contents 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 conjugate acid of decamethylcobaltocene and collidine (collidine), which is expensive, in a stoichiometric amount. Therefore, from an industrial viewpoint, the development of a cheaper method for producing ammonia is expected.

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

method used to solve the problem

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

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

The above catalyst is (A) with 2,6-bis(dialkylphosphinomethyl)pyridine (wherein, the two alkyl groups can be the same or different, and at least one hydrogen atom of the pyridine ring can be replaced by an alkyl, alkoxy Substituted by a group or a halogen atom) as a molybdenum coordination compound of a PNP ligand, (B) has N,N-bis(dialkylphosphinomethyl)benzimidazolecarbene (N,N-bis(dialkylphosphinomethyl)benzimidazolidene, Wherein, the two alkyl groups can be the same or different, and at least one hydrogen atom of the benzene ring can be replaced by an alkyl group, an alkoxyl group or a halogen atom) as a molybdenum coordination compound of the PCP ligand, (C) has a double ( Dialkylphosphinoethyl)arylphosphine (wherein, the two alkyl groups may be the same or different) molybdenum coordination compound as a PPP ligand, or (D) trans-Mo(N ₂ ) ₂ (R ¹ R ² R ³ P) ₄ (where 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 compound,

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

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

According to this method for producing ammonia, alcohol and water can be used as a proton source, 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 before.

Detailed ways

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

The method for producing ammonia according to the present embodiment is a method for producing ammonia from nitrogen molecules in the presence of a catalyst, a reducing agent, and a proton source. In this method, as a catalyst, use (A) with 2,6-bis(dialkylphosphinomethyl)pyridine (wherein, the two alkyl groups can be the same or different, and at least one hydrogen atom of the pyridine ring can be Substituted by an alkyl group, an alkoxy group or a halogen atom) as a molybdenum coordination compound of a PNP ligand, (B) has N,N-bis(dialkylphosphinomethyl)benzimidazolcarbene (among them, 2 The alkyl groups can be the same or different, and at least one hydrogen atom of the benzene ring can be replaced by an alkyl group, an alkoxy group or a halogen atom) as a molybdenum coordination compound of the PCP ligand, (C) has a bis(dialkylphosphine Ethyl) arylphosphine (wherein, the two alkyl groups can be the same or different) molybdenum coordination compound as a PPP ligand, or (D) trans-Mo(N ₂ ) ₂ (R ¹ R ² R ^3P ) 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) as a molybdenum coordination compound. In addition, as a reducing agent, a lanthanide metal halide (II) is used, and as a proton source, alcohol or water is used.

In the molybdenum complex of (A), the alkyl group may be, for example, a linear or branched group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and their structural isomers. The alkyl group may also be a cyclic alkyl group such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, or a cyclohexyl group. 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 cyclopropoxy, cyclobutoxy, cyclopentyloxy, cyclohexyloxy or the like. 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.

Examples of the molybdenum complex of (A) include molybdenum complexes represented by formula (A1), (A2) or (A3). Examples of the alkyl group, alkoxy group and halogen atom include the same groups and atoms as those already exemplified. R ¹ and R ² are preferably bulky alkyl groups (eg, tert-butyl, isopropyl). 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, ^R1 and ^R2 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)

Examples of the molybdenum complex of (B) include molybdenum complexes represented by formula (B1). Examples of the alkyl group, alkoxy group and halogen atom include the same groups and atoms as those already exemplified. R ¹ and R ² are preferably bulky alkyl groups (eg, tert-butyl, isopropyl). The hydrogen atoms on the benzene ring are preferably unsubstituted, or the hydrogen atoms at positions 5 and 6 are substituted with chain, cyclic or branched alkyl groups having 1 to 12 carbon atoms. Particular preference is given to molybdenum complexes 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 by a fluorine group, further more preferably at least one of R ³ and R ⁴ were substituted by trifluoromethyl. The benzimidazole compound of formula (E) can be used as an intermediate for synthesizing the molybdenum complex compound 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). The anion of A is not particularly limited, and examples thereof include PF ₆ ^- , BF ₄ ^- , ClO ₄ ^- and the like.

(In the formula, ^R1 and ^R2 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)

Examples of the molybdenum complex of (C) include molybdenum complexes represented by formula (C1). Examples of the alkyl group include the same ones as those already exemplified. Examples of the aryl group include phenyl, tolyl, xylyl, naphthyl, and groups in which at least one of hydrogen atoms on these rings is substituted with an alkyl group or a halogen atom. Examples of the alkyl group and halogen atom include the same groups and atoms as those already exemplified. R ¹ and R ² are preferably bulky alkyl groups (eg, tert-butyl, isopropyl). R ³ is preferably, for example, phenyl.

(wherein, ^R1 and ^R2 are alkyl groups that can be the same or different, ^R3 is an aryl group, and X is an iodine atom, bromine atom or chlorine atom)

Examples of the molybdenum complex of (D) include molybdenum complexes represented by formula (D1) or (D2). Examples of the alkyl group and aryl group include the same ones as those already exemplified. In formula (D1), preferably R ¹ and R ² are aryl (such as phenyl) and R ³ is an alkyl group with 1 to 4 carbon atoms (such as methyl), or R ¹ and R ² are carbon atoms 1 to 4 alkyl (such as methyl) and R ³ is aryl (such as phenyl). In formula (D2), it is preferred that R ¹ and R ² are aryl (eg phenyl) and n is 2.

(In the formula, R ¹ , R ² and R ³ are alkyl or aryl groups that 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 gas at normal pressure as nitrogen molecules. 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 alcohol is used as the proton source, diol can be used as the alcohol, and ROH (R is a hydrogen atom with 1 to 6 carbon atoms that can be replaced by a fluorine atom) can also be used. chain, cyclic or branched alkyl, or phenyl that may have an alkyl). Examples of diols include ethylene glycol, propylene glycol, and diethylene glycol, among which ethylene glycol is preferred. Examples of ROH include chain or branched alkyl alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, isobutanol, and tert-butanol; Cyclic alkyl alcohols such as alcohol 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 according to the present embodiment, ammonia can be produced from nitrogen molecules in a solvent. The solvent is not particularly limited, and examples thereof include cyclic ether solvents, chain ether solvents, nitrile solvents, and hydrocarbon solvents. Examples of the cyclic ether-based solvent include tetrahydrofuran (hereinafter, abbreviated as THF or thf), dioxane, and the like. As a chain ether solvent, diethyl ether etc. are mentioned, for example. As a nitrile solvent, acetonitrile, propionitrile etc. are mentioned, for example. Examples of the hydrocarbon-based solvent include aromatic hydrocarbons such as toluene, saturated hydrocarbons such as hexane, and the like.

In the method for producing ammonia according to 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, but may be a normal pressure atmosphere. The reaction time is not particularly limited, but usually it may be set within a range of several minutes to several tens of hours.

In the method for producing ammonia according to the present embodiment, the amount of catalyst used may be appropriately used in the range of 0.00001 to 0.1 equivalent relative to the reducing agent, preferably 0.0005 to 0.1 equivalent, and more preferably 0.005 to 0.01 equivalent. The amount of the proton source used is preferably 0.5 to 5 equivalents, more preferably 1 to 2 equivalents, based on the reducing agent.

In the method for producing ammonia according to the present embodiment, the lanthanide metal used as the halide (II) of the lanthanide metal includes La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb, and Lu, among which Sm is preferable, and examples of the halogen include chlorine, bromine, and iodine, among which iodine is preferable. The halide (II) of the lanthanide metal is preferably samarium (II) halide, more preferably samarium (II) iodide.

In addition, this invention is not limited to the said embodiment at all, It goes without saying that it can implement in various aspects as long as it belongs to the technical scope of this 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 molybdenum complex (1a) (the chemical formula is shown in the extra column of Table 1) as a catalyst (Table 1). In the following experimental examples, when more than 2 equivalents of ammonia were generated with respect to the molybdenum metal in the catalyst, it was judged that ammonia was generated catalytically. The molybdenum complex (1a) was synthesized with reference to known literature (Bull.Chem.Soc.Jpn.2017, vol.90, pp1111-1118).

[Table 1]

^a Reducing agent baseline ^b 1 mL of THF was used ^c No catalyst ^d CoCp* ₂ was used 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 , 0.36mmol, 180 equivalents to molybdenum) in tetrahydrofuran solution (6mL), add ethylene glycol (20μL, 0.36mmol, 180 equivalents, 1 equivalent (1 times mole) to the reducing agent) as a source of hydrogen ions , and then stirred for 18 hours. Then, potassium hydroxide aqueous solution (30 mass%, 5 mL) was added, it distilled under reduced pressure, and the distillate was recovered with sulfuric acid aqueous solution (0.5M, 10 mL). The amount of ammonia in the sulfuric acid aqueous solution was determined by the indophenol method (Analytical Chemistry, 1967, vol.39, pp971-974). As a result, 43.8 equivalents of ammonia were generated with respect to the catalyst (molybdenum complex).

In Experimental Examples 2-6, the amount of ethylene glycol used in Experimental Example 1 was set between 0.5 and 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 to 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% respectively based on the reducing agent, and the reaction was basically completed in 15 minutes. The maximum TOF calculated from this result was 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 problem.

In Experimental Examples 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, ammonia can be obtained catalytically, although the yield is slightly lower than that of THF. In addition, in Experimental Example 13, an experiment was conducted in which ethylene glycol was used as both a proton source and a solvent. As a result, ammonia was 8% based on the reducing agent, and 4.9 equivalents were produced with respect to molybdenum. Therefore, it was confirmed that ammonia was generated catalytically even when ethylene glycol was used as the solvent.

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

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

[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 the 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). The molybdenum complexes (1c) and (2) were synthesized with reference to known documents (Nat.Chem.2011, vol.3, pp120-125). The molybdenum coordination compound (3a) was synthesized by referring to the known literature (Nat. Commun. 2017, vol. 8, Airticle No. 14874). The molybdenum coordination compound (3b) was synthesized by referring to the known literature (J.Am.Chem.Soc.2015, vol.137, pp5666-5669). The molybdenum complex (5a) was synthesized by referring to known documents (Inorg.Chem.1973, vol.12, pp2544-2547). The molybdenum complex (5b) was synthesized by referring to known documents (J.Am.Chem.Soc.1972, vol.94, pp110-114). The molybdenum complex (4) was synthesized as follows. With respect to the THF solution (16mL) of molybdenum coordination compound (1a) (0.2mmol, 174.4mg), under 1 pressure of nitrogen atmosphere, add pyridine (0.4mmol, 38μL), water (0.4mmol, 7μL), in Stir at 50°C for 14 hours. Then, the reaction solution was concentrated to dryness and solidified 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 in vacuo to solidify. The solid was dissolved in dichloromethane (4 mL), filtered through celite, hexane (20 mL) was added, and recrystallized for 4 days to obtain 46.1 mg (0.059 mmol, 30% yield) as light yellow crystals of 4 (molybdenum complex (4)).

[Table 2]

^aReductant benchmark ^bUsed 0.01mmol of catalyst

In Experimental Examples 22-23, molybdenum complexes (1b) to (1c) having a PNP ligand were used as catalysts. It can be seen 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 24-27, as catalysts, dinuclear molybdenum complexes (2) with PNP ligands, molybdenum complexes (3a) with PCP ligands, and molybdenum complexes (3a) with PPP ligands were used. Coordination compound (3b) and Mo(IV) oxo coordination compound (4) with PNP ligand. It can be seen that ammonia is catalytically generated regardless of any of the molybdenum complexes (2), (3a), (3b), and (4) used. Among them, particularly good results were obtained with the molybdenum complex (3a).

In Experimental Examples 28-29, mononuclear molybdenum complexes (5a) to (5b) were used as catalysts. It was found that ammonia was catalytically produced regardless of the use of any 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 (see the following formula). With respect to a THF solution (4 mL) of molybdenum complex (1a) (0.002 mmol) and SmI ₂ (thf) ₂ (solid crystals, 0.36 mmol, 180 equivalents to molybdenum), under a nitrogen atmosphere of 1 atmosphere, A THF solution (2 mL) of water (0.36 mmol, 180 equivalents to molybdenum) was added dropwise over 0.5 hours at room temperature with stirring. After completion of the dropwise addition, the mixture was further stirred at room temperature for 17.5 hours, and ammonia and hydrogen were quantified. As a result, 43% of ammonia (26.8 equivalents to molybdenum) and 39% of hydrogen (36.0 equivalents to molybdenum) were generated. Therefore, it can be seen that ammonia is catalytically produced even when water is used as a proton source.

[Experimental examples 31-38]

In Experimental Examples 31-38, ammonia was produced from nitrogen molecules in THF at room temperature 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 carried out using 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]

*Based on the yield of _SmI2 (thf) ₂ . Average of multiple experiments (at least 2 cases).

# THF (2 mL) was used as solvent. § Use H ₂ O as proton source.

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

[Experimental Example 39-41]

In Experimental Examples 39-41, 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 (H ₂ O) (Table 4 ). In Experimental Example 39, the above-mentioned molybdenum coordination compound (3a) was used as a catalyst, and in Experimental Example 40, a molybdenum coordination compound (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 carried out using a molybdenum complex (3d) having a trifluoromethyl group at the 5-position of the benzimidazole carbene ring as a catalyst.

Experimental Example 41 will be described as a representative example. For molybdenum complex (3d) (0.025μmol) and SmI ₂ (thf) ₂ (solid crystals, 1.44mmol, 57600 equivalents relative to molybdenum) in THF solution (2mL), under 1 pressure of nitrogen atmosphere, in A THF solution (1 mL) of water (1.44 mmol, 57600 equivalents 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, 4,700 equivalents of hydrogen were generated with respect to the catalyst (molybdenum complex). Potassium hydroxide aqueous solution (30 mass%, 5 mL) was added, it 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 sulfuric acid aqueous solution was determined by the indophenol method (Analytical Chemistry, 1967, vol.39, pp971-974). As a result, 16,000 equivalents of ammonia were generated 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 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, compared with the molybdenum complex (3a), the catalytic activity of the molybdenum complex (3c), (3d) is higher, and compared with the molybdenum complex (3c), the molybdenum complex (3d) has higher catalytic activity.

[Table 4]

*Based on the yield of _SmI2 (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 a nitrogen atmosphere. The reactant was concentrated, and the obtained solid was separated by silica gel column chromatography (dichloromethane:hexane=1/1). The recovered fraction was concentrated, dried and solidified under vacuum to isolate compound 1 as 2.48 g (3.81 mmol, 63% yield) as a white solid. ¹ H NNR (CDCl ₃ ): δ7.08(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 ): δ79.9(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 under air at 120° C. for 3 hours. 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 resulted in the isolation of Compound 2 as a white solid in 2.58 g (3.20 mmol, 84% yield). ¹ H NNR (CDCl ₃ ): δ10.13(s, 1H), 8.16(s, 1H), 8.11(d, J=8.4Hz, 1H), 7.89(d, J=8.4Hz, 1H), 5.08- 5.04 (m, 4H), 1.48 (d, J=16.0Hz, 18H), 1.47 (d, J=16.4Hz, 18H), ³¹ P NMR (CDCl ₃ ): δ81.7(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) was stirred at room temperature under nitrogen atmosphere for 4 hours. Then, it was concentrated and washed with toluene (7 mL×3), and dried under vacuum to isolate Compound 3 as a white solid in 1.66 g (2.56 mmol, 80% yield). ¹ H NNR (CDCl ₃ ): δ9.81(s, 1H), 8.27(s, 1H), 8.15(d, J=8.4Hz, 1H), 7.88(d, J=8.4Hz, 1H), 4.72- 4.70 (m, 4H), 1.23 (d, J=12.0Hz, 18H), 1.21 (d, J=12.0Hz, 18H), ³¹ P NMR (CDCl ₃ ): δ25.9(s), 25.1(s) , -139.4～-152.6 (m).

·Synthesis of molybdenum complex (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 under argon atmosphere for 1 hour. Then, after filtering with celite, MoCl ₃ (thf) ₃ (756 mg, 1.81 mmol) was added thereto, followed by stirring at 80° C. for 26 hours. The reaction solution was concentrated up 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 left 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 381 mg (0.54 mmol, 30% yield) as brown crystals. 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 coordination compound (3c) used in Experimental Example 40 can be replaced by 1,2-diamino-4-trifluoromethylbenzene in the synthesis scheme of the molybdenum coordination compound (3d) by using 1,2-bis Amino-4,5-difluorobenzene was synthesized.

[Experimental Example 42]

In Experimental Example 42, the production of ammonia was carried out on an enlarged scale. In a 1000mL four-neck flask, THF relative to molybdenum complex (3a) (0.100mmol, 63.8mg) and SmI ₂ (thf) ₂ (solid crystal, 36.0mmol, 19.7g, relative to molybdenum is 360 equivalents) solution (270mL), under nitrogen flow, THF solution (20mL) of water (36.0mmol, 360 equivalents relative to molybdenum) was added at room temperature while stirring with a mechanical stirrer (220rpm), and stirred at room temperature for 8 minute. The reaction solution was concentrated, dried and solidified using an evaporator. Potassium hydroxide aqueous solution (30% by mass, 20 mL) was added to the obtained solid, and it was distilled 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 using an evaporator and dried under vacuum overnight. As a result, 668 mg (5.06 mmol, 84% yield) of white solid (NH ₄ ) ₂ SO ₄ was obtained. This corresponds to the production of 101 equivalents of ammonia relative to the catalyst (molybdenum complex). Anal. Calcd. for _{H 8} N ₂ O ₄ S: H, 6.10; N, 21.20 Found: H, 6.06; N, 20.98.

In addition, 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 claims priority based on 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 incorporated by reference The content is included in this manual.

industry availability

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

Claims (11)

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

the catalyst is (A) a molybdenum complex having 2, 6-bis (dialkylphosphinomethyl) pyridine as PNP ligand, (B) a molybdenum complex having N, N-bis (dialkylphosphinomethyl) benzimidazole carbene as PCP ligand, (C) a molybdenum complex having bis (dialkylphosphinoethyl) arylphosphine as PPP ligand, or (D) trans-Mo (N) ₂ ) ₂ (R ¹ R ² R ³ P) ₄ Molybdenum complex compounds represented, wherein 2 alkyl groups in the 2, 6-bis (dialkylphosphinomethyl) pyridine are the same or different, at least 1 hydrogen atom of the pyridine ring is substituted or not substituted by an alkyl group, an alkoxy group or a halogen atom, 2 alkyl groups in the N, N-bis (dialkylphosphinomethyl) benzimidazole carbene are the same or different, at least 1 hydrogen atom of the benzene ring is substituted or not substituted by an alkyl group, an alkoxy group or a halogen atom, or is not substituted by an alkyl group, an alkoxy group or a halogen atom, 2 alkyl groups in the bis (dialkylphosphinoethyl) arylphosphine are the same or different, and trans-Mo (N ₂ ) ₂ (R ¹ R ² R ³ P) ₄ Wherein R is ¹ 、R ² 、R ³ Are the same or different alkyl or aryl groups, 2R ³ Are linked to each other to form an alkylene chain or are not linked to each other to form an alkylene chain,

as the 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 represented by the following formula (A1), (A2) or (A3),

wherein R is ¹ And R is ² And X is an iodine atom, a bromine atom or a chlorine atom, and at least 1 hydrogen atom on the pyridine ring is substituted with an alkyl group, an alkoxy group or a halogen atom or is not substituted with an alkyl group, an alkoxy group or a halogen atom.

3. The method for producing ammonia according to claim 1, wherein the molybdenum complex compound represented by the following formula (B1),

wherein R is ¹ And R is ² And X is an iodine atom, a bromine atom or a chlorine atom, and at least 1 hydrogen atom on the benzene ring is substituted with an alkyl group, an alkoxy group or a halogen atom or is not substituted with 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 represented by the formula (C1),

wherein R is ¹ And R is ² R are identical or different alkyl radicals ³ Is aryl, X is iodine atom, bromine atom or chlorine atom.

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

wherein R is ¹ 、R ² And R is ³ Are identical or different alkyl or aryl groups, n being 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 molecule.

8. The method for producing ammonia according to any one of claims 1 to 6, wherein the alcohol is a diol or ROH, and R is a chain, cyclic or branched alkyl group having 1 to 6 carbon atoms, in which a hydrogen atom is substituted or unsubstituted with a fluorine atom, or a phenyl group having an alkyl group or not having an alkyl group.

9. The method for producing ammonia according to any one of claims 1 to 6, wherein the halide (II) of a lanthanide metal is samarium (II) halide.

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

wherein R is ¹ And R is ² Is the same or different alkyl, X is an iodine atom, a bromine atom or a chlorine atom, R ³ And R is ⁴ At least one of which is substituted by trifluoromethyl.

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

wherein A is an anion, R ¹ And R is ² R are identical or different alkyl radicals ³ And R is ⁴ At least one of which is substituted by trifluoromethyl.