PYRIDINE PYRROLE RUTHENIUM COORDINATION COMPLEX, PREPARATION METHOD THEREFOR AND USE THEREOF AS CATALYST FOR ELECTROCATALYZING AMMONIA OXIDATION TO PREPARE HYDRAZINE

Abstract

A pyridine pyrrole ruthenium coordination complex, a preparation method therefor and use thereof as a catalyst for electrocatalyzing ammonia oxidation to prepare hydrazine is provided. The pyridine pyrrole ruthenium coordination complex takes high-activity metal ruthenium as a central metal ion and compounds containing pyridine pyrrole with electron withdrawing/donating capability as ligands, and thus has relatively high catalytic activity for ammonia oxidation. High conversion rate and highly selective conversion of ammonia can be realized by applying the pyridine pyrrole ruthenium coordination complex to electrocatalytic ammonia oxidation in an organic solvent, with major products including H.sub.2, N.sub.2, N.sub.2H.sub.4.

Claims

1. A pyridine pyrrole ruthenium coordination complex, having a structure of any one of Formula 1 to Formula 5: ##STR00009##

2. A method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 1, comprising the following steps: 1) dissolving 2,5-dipyridylpyrrole, 2,5-dipyridyl-3-methyl-4-acetylpyrrole or 2,5-dipyridyl-3-carboxymethyl-4-methylpyrrole, cis-dichlorotetrakis(dimethyl sulfoxide)ruthenium, bipyridine and a basic compound in a solvent to provide a first resulting solution, and heating the first resulting solution to reflux and causing a first reaction to obtain the pyridine pyrrole ruthenium coordination complex having a structure of Formula 1, formula 4 or Formula 5; then optionally 2) dissolving the pyridine pyrrole ruthenium coordination complex having a structure of Formula 1 in a solvent to provide a second resulting solution, then first heating the second resulting solution to reflux and causing a second reaction, and then adding saturated ammonium hexafluorophosphate solution for ion exchange to obtain a pyridine pyrrole ruthenium coordination complex having a structure of Formula 2; and further optionally 3) dissolving the pyridine pyrrole ruthenium coordination complex having a structure of Formula 2 in a solvent to obtain a third resulting solution, and then introducing an ammonia-containing gas to the third resulting solution and causing a third reaction to obtain the pyridine pyrrole ruthenium coordination complex having a structure of Formula 3.

3. The method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 2, wherein a molar ratio of 2,5-dipyridylpyrrole, 2,5-dipyridyl-3-methyl-4-acetylpyrrole or 2,5-dipyridyl-3-carboxymethyl-4-methylpyrrole to cis-dichlorotetrakis(dimethyl sulfoxide)ruthenium is 1:2 to 2:1.

4. The method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 2, wherein a molar ratio of cis-dichlorotetrakis(dimethyl sulfoxide)ruthenium to bipyridine is 1:3 to 3:1.

5. The method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 2, wherein the basic compound is at least one selected from the group consisting of calcium hydride, sodium hydride and triethylamine.

6. The method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 2, wherein in step (1), the first reaction is performed at a temperature of 50-115? C. for a period of 8-12 h.

7. The method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 2, wherein step (2) is performed, and in step (2) the second reaction is performed at a temperature of 50-115? C. for a period of 2-6 d.

8. The method for synthesizing the pyridine pyrrole ruthenium coordination complex according to claim 2, wherein steps (2) and (3) are performed, and in step (3) the ammonia-containing gas has an ammonia concentration of greater than 1%.

9. A method of using the pyridine pyrrole ruthenium coordination complex according to claim 1 as a catalyst for electrocatalyzing ammonia oxidation to prepare N.sub.2H.sub.4 and co-produce H.sub.2, comprising the step of providing ammonia to the catalyst.

10. A method of using the pyridine pyrrole ruthenium coordination complex according to claim 1 as a catalyst for electrocatalyzing ammonia oxidation to prepare N.sub.2H.sub.4 and co-produce H.sub.2, comprising the step of providing ammonia to the catalyst, wherein the catalyst is dissolved in an organic solvent selected from the group consisting of anhydrous tetrahydrofuran and anhydrous acetonitrile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 is a single crystal diffraction pattern of coordination complex 1 [Ru(K.sup.2N,N-dpp)(bpy)(S-dmso)(Cl)];

[0041] FIG. 2 is a single crystal diffraction pattern of coordination complex 2 [Ru(K.sup.3N,NN-dpp)(bpy)(S-dmso)].Math.PF.sub.6;

[0042] FIG. 3 is a single crystal diffraction pattern of coordination complex 3 [Ru(K.sup.2N,N-dpp)(bpy)(S-dmso)(NH.sub.3)].Math.PF.sub.6;

[0043] FIG. 4 is a single crystal diffraction pattern of coordination complex 4 [Ru(K.sup.2N,N-mdpc)(bpy)(S-dmso)(Cl)];

[0044] FIG. 5 is a single crystal diffraction pattern of coordination complex 5 [Ru(K.sup.3N,NN-mdpe)(bpy)(Cl)];

[0045] FIGS. 6A-6B are graphs showing standard curves of gas chromatography of hydrogen and nitrogen;

[0046] FIG. 7 is a graph showing the gas composition during ammonia oxidation reactions electrocatalyzed by 0.01 mM coordination complexes 1, 2 and 3;

[0047] FIGS. 8A-8D are graphs showing the gas composition during an ammonia oxidation reaction electrocatalyzed by 0.01 mM coordination complex 3 at various reaction times;

[0048] FIGS. 9A-9D are graphs showing the gas composition during an ammonia oxidation reaction electrocatalyzed by 0.01 mM coordination complex 5 at various reaction times;

[0049] FIGS. 10A-10B are graphs showing ultraviolet-visible spectrum absorption intensity and hydrazine concentration standard curves;

[0050] FIG. 11 is a graph showing ultraviolet-visible absorption spectra of the electrolysis solutions of coordination complexes 1, 2, and 3 after reacting with p-C.sub.9H.sub.11NO for 1 h.

DETAILED DESCRIPTION OF THE INVENTION

[0051] To facilitate the understanding of the present invention, the present invention will be described comprehensively and in further detail with reference to preferred examples. However, the protection scope of the present invention is not limited to the following specific examples.

[0052] The substrate starting materials, solvents, etc. involved in the following examples are all commercially available products (analytically pure reagents). All the reagents used had underwent purification, drying and oxygen removal pretreatments. The involved synthesis and treatment processes used standard anhydrous and oxygen-free treatment techniques. .sup.1H NMR, .sup.31P NMR, and .sup.19F NMR used CDCl.sub.3 as solvent and TMS as internal standard.

[0053] Multiplicity is defined as follows: s (singlet); d (doublet); t (triplet); q (quartet) and m (multiplet). Absorption intensity is defined as follows: s (strong absorption); m (moderate absorption); w (weak absorption).

[0054] Unless defined otherwise, all the terms used in the following have the same meaning as commonly understood by those skilled in the art. The terms used herein are for the purpose of describing specific examples only and not all of them are within the scope of the present invention.

Example 1

1. Preparation of Coordination Complex 1 [Ru(K.SUP.2.N,N-dpp)(bpy)(S-dmso)(Cl)]

[0055] ##STR00004##

[0056] (1) cis-Dichlorotetrakis(dimethyl sulfoxide)ruthenium (1.088 g, 2.248 mmol), 2,5-dipyridylpyrrole (0.566 g, 2.248 mmol), bipyridine (0.351 g, 2.247 mmol) and triethylamine were dissolved in an organic solvent (50 mL) under nitrogen atmosphere. The solution was magnetically stirred and heated to 105? C. and was reacted for 10 h.

[0057] (2) After the reaction was completed, toluene, diethyl ether and water were each added under nitrogen atmosphere to wash the mixture three times. Subsequently, the resulting solid was dissolved in dichloromethane, and anhydrous sodium sulfate was added to remove water was removed from the solution. The solvent was removed from the filtrate to obtain a red solid.

[0058] (3) The resulting red solid was dissolved in dichloromethane by liquid phase diffusion, and diethyl ether and n-hexane were sequentially added. After the mixture was left to stand for 2 weeks, coordination complex 1 was obtained as a red acicular crystal.

[0059] Yield: 32%

[0060] .sup.1H NMR (400 MHz, CDCl.sub.3): ?10.171-10.186 (d, 1H), ?9.399-9.413 (d, 1H), ?8.125-8.137 (d, 1H), ?7.914-7.934 (d, 1H), ?7.644-7.731 (m, 3H), ?7.573-7.607 (t, 2H), ?7.472-7.510 (m, 1H), ?7.099-7.169 (m, 4H), ?6.963-6.995 (m, 1H), ?6.829-6.838 (d, 1H), ?6.676-6.710 (m, 1H), ?6.299-6.309 (d, 1H), ?3.165 (s, 3H), ?2.401 (s, 3H) ppm.

[0061] IR (KBr, cm.sup.?1): 1589 (s), 1522 (s), 1433 (s), 1323 (s), 1279 (w), 1152 (w), 1074 (s), 1014 (s), 961 (w), 919 (w), 789 (m), 766 (s), 724 (m), 686 (m), 435 (m).

2. Preparation of Coordination Complex 2 [Ru(K.SUP.3.N,NN-dpp)(bpy)(S-dmso)].Math.PF.SUB.6

[0062] ##STR00005##

[0063] (4) Coordination complex 1 was dissolved in an organic solvent under nitrogen atmosphere. The solution was stirred and heated to 60? C., reacted for 4 days, and then concentrated to 3 mL by rotary evaporation.

[0064] (5) A saturated aqueous ammonium hexafluorophosphate solution was added dropwise to the above solution. After 2 h of stirring, the reaction mixture was filtered and dried by rotary evaporation to obtain a yellow solid.

[0065] (6) The resulting red solid was dissolved in dichloromethane by liquid phase diffusion, and diethyl ether and n-hexane were sequentially added. After the mixture was left to stand for 2 weeks, coordination complex 2 was obtained as a red acicular crystal.

[0066] Yield: 93%.

[0067] .sup.1H NMR (400 MHz, CDCl.sub.3): ?10.315-10.301 (d, 1H), ?8.583-8.563 (d, 1H), ?8.442-8.422 (d, 1H), ?8.177-8.138 (t, 1H), ?7.924-7.884 (t, 1H), ?7.763-7.730 (t, 1H), ?7.550-7.511 (m, 2H), ?7.418-7.399 (d, 2H), ?7.328-7.315 (d, 2H), ?7.231-7.197 (t, 1H), ?6.909 (s, 2H), ?6.823-6.809 (d, 1H), ?6.748-6.715 (m, 2H), ?2.582 (s, 6H) ppm.

[0068] .sup.31P NMR (162 MHz, CDCl.sub.3): ??135.60, 6-140.01, 6-144.40, 6-148.80, 6-153.20 ppm.

[0069] .sup.19F NMR (380 MHz, CDCl.sub.3): ??72.36, ??74.25 ppm.

[0070] IR (KBr, cm.sup.?1): 1598 (s), 1486 (s), 1396 (m), 1298 (s), 1263 (w), 1156 (w), 1087 (m), 1042 (w), 1008 (m), 840 (s), 760 (s), 557 (s), 431 (m).

TABLE-US-00001 TABLE 1 Crystal data of coordination complex 2 Compound Coordination complex 2 Empirical formula C.sub.26H.sub.24F.sub.6N.sub.5OPRuS Formula weight 700.60 Crystal system monoclinic Space group P2.sub.1/n a/? 9.52761(19) b/? 26.2603(5) c/? 12.0967(2) a/? b/? 101.4548(16) g/? V/[?.sup.3] 2966.28(10) Z 4 ?.sub.calcd [g cm.sup.?3] 1.569 u [mm?.sup.1] 0.719 F(000) 1408.0 R.sub.int 0.0384 .sup.aGooF 1.024 .sup.bR.sub.1, .sup.cwR.sub.2 [I > 2? (I)] 0.0406/0.0898 R.sub.1, wR.sub.2 [all data] 0.0615/0.0968 .sup.aGOOF = [?w(|F.sub.o| ? |F.sub.c|).sup.2/(N.sub.obs ? N.sub.param)].sup.1/2. .sup.bR.sub.1 = ?||F.sub.o| ? |F.sub.c||/?|F.sub.o|. .sup.cwR.sub.2[(?w|F.sub.o| ? |F.sub.c|).sup.2/?w.sup.2|F.sub.o|.sup.2].sup.1/2.

TABLE-US-00002 TABLE 2 Some bond length and bond angle data of coordination complex 2 Bond Distances(?) Ru(1)N(1) 2.1371(19) Ru(1)N(5) 2.1002(19) Ru(1)N(2) 1.9368(17) Ru(1)S(1) 2.2310(6) Ru(1)N(3) 2.1341(17) S(1)O(1) 1.4823(17) Ru(1)N(4) 2.1037(17) Bond Angles (?) N(1)Ru(1)N(2) 76.22(7) N(3)Ru(1)N(5) 84.61(7) N(1)Ru(1)N(3) 152.48(7) N(4)Ru(1)N(5) 77.58(7) N(1)Ru(1)N(4) 102.97(7) S(1)Ru(1)N(1) 91.80(5) N(1)Ru(1)N(5) 92.43(7) S(1)Ru(1)N(2) 92.53(6) N(2)Ru(1)N(3) 76.55(7) S(1)Ru(1)N(3) 93.28(5) N(2)Ru(1)N(4) 169.54(8) S(1)Ru(1)N(4) 97.93(6) N(2)Ru(1)N(5) 92.00(8) S(1)Ru(1)N(5) 174.42(5) N(3)Ru(1)N(4) 103.07(7) O(1)S(1)Ru(1) 118.20(8)

3. Preparation of Coordination Complex 3 [Ru(K.SUP.2.N,N-dpp)(bpy)(S-dmso)(NH.SUB.3.)].Math.PF.SUB.6

[0071] ##STR00006##

[0072] (1) Coordination complex 2 (35 mg, 0.050 mmol) was dissolved in trichloromethane. Then 2% ammonia gas was introduced (nitrogen as carrier gas) for half an hour, and the solution was left to stand for 1 h. The process was repeated 3 times. The solution was left to stand for 2 weeks and finally concentrated at room temperature. Diethyl ether and n-hexane were sequentially added, and coordination complex 3 was obtained as a red lamellar crystal by liquid phase diffusion.

[0073] Yield: 98%.

[0074] .sup.1H NMR (400 MHz, CDCl.sub.3): ?9.871-9.858 (d, 1H), ?8.412-8.401 (d, 1H), ?8.313-8.293 (d, 1H), ?8.251-8.231 (d, 1H), ?7.714-7.675 (t, 1H), ?7.646-7.612 (t, 1H), ?7.517-7.503 (d, 1H), ?7.463-7.402 (m, 2H), ?7.328-7.315 (d, 2H), ?7.189-7.175 (d, 1H), ?7.095-7.175 (d, 1H), ?7.095-7.064 (m, 1H), ?7.029-7.019 (d, 1H), ?6.981-6.952 (t, 1H), ?6.617-6.586 (t, 1H), ?3.160 (s, 3H), ?3.110 (s, 3H), ?2.534 (s, 3H) ppm.

[0075] .sup.31P NMR (162 MHz, CDCl.sub.3): ??135.92, 6-140.28, 6-144.64, 6-149.00, 6-153.36 ppm.

[0076] .sup.19F NMR (380 MHz, CDCl.sub.3): ??72.02, ??73.89 ppm.

[0077] IR (KBr, cm.sup.?1): 3371 (w), 1604 (m), 1529 (m), 1454 (w), 1421 (m), 1325 (m), 1161 (w), 1080 (m), 1018 (m), 843 (s), 764 (m), 685 (w), 557 (m), 430 (m).

4. Preparation of Coordination Complex 4 [Ru(K.SUP.2.N,N-mdpc)(bpy)(S-dmso)(Cl)] Target Product

[0078] ##STR00007##

[0079] (1) Dichlorotetrakis(dimethyl sulfoxide)ruthenium (1.088 g, 2.248 mmol), 2,5-dipyridyl-3-carboxymethyl-4-methylpyrrole ligand (0.659 g, 2.248 mmol), bipyridine (0.351 g, 2.247 mmol) and triethylamine were dissolved in an organic solvent (50 mL) under nitrogen atmosphere. The solution was stirred and heated to 105? C. and was reacted for reaction for 9 h.

[0080] (2) After the reaction was completed, diethyl ether and water were each added under nitrogen atmosphere to wash the mixture three times. Subsequently, the resulting solid was dissolved in dichloromethane, and anhydrous sodium sulfate was added to remove water from the solution. The solvent was removed from the filtrate to obtain a red solid.

[0081] (3) The red solid was separated by column chromatography on a chromatographic silica gel column to obtain a red solid product.

[0082] (4) The resulting red solid was dissolved in dichloromethane by liquid phase diffusion, and diethyl ether and n-hexane were sequentially added. After the mixture was left to stand for 2 weeks, coordination complex 4 was obtained as a red acicular crystal.

[0083] Yield: 25%.

[0084] .sup.1H NMR (400 MHz, CDCl.sub.3): ?9.677-9.689 (d, 1H), ?9.552-9.565 (d, 1H), ?8.045-8.091 (t, 2H), ?7.847-7.868 (d, 2H), ?7.738-7.796 (m, 2H), ?7.485-7.528 (m, 1H), ?7.430-7.442 (d, 1H), ?7.132-7.178 (m, 2H), ?7.026-7.062 (m, 1H), ?6.892-6.928 (m, 1H), ?6.779-6.813 (m, 1H), ?6.724 (s, 1H), ?3.290 (s, 3H), ?3.019 (s, 3H) ppm, ?2.744 (s, 3H) ppm, ?2.460 (s, 3H) ppm.

[0085] IR (KBr, cm.sup.?1): 3603 (m), 2916 (s), 2497 (m), 1682 (s), 1589 (m), 1521 (w), 1444 (s), 1414 (w), 1323 (w), 1261 (w), 1198 (w), 1153 (w), 1078 (s), 1012 (w), 766 (s), 729 (w), 679 (w), 430 (m).

5. Preparation of Coordination Complex 5 [Ru(K.SUP.3.N,NN-mdpe)(bpy)(Cl)] Target Product

[0086] ##STR00008##

[0087] (1) cis-[Ru(dmso).sub.4(Cl).sub.2] (1.088 g, 2.248 mmol), 2,5-dipyridyl-3-methyl-4-acetylpyrrole (0.623 g, 2.248 mmol), bipyridine (0.351 g, 2.247 mmol) and a base were dissolved in an organic solvent (50 mL) under nitrogen atmosphere. The solution was stirred and heated to 100? C. and was reacted for 12 h.

[0088] (2) After the reaction was completed, toluene, diethyl ether and water were each added under nitrogen atmosphere to wash the mixture three times. Subsequently, the resulting solid was dissolved in dichloromethane, and anhydrous sodium sulfate was added to remove water from the solution. The solvent was removed from the filtrate to obtain a red solid.

[0089] (3) The resulting red solid was dissolved in dichloromethane by liquid phase diffusion, and diethyl ether and n-hexane were sequentially added. After the mixture was left to stand for 2 weeks, coordination complex 5 was obtained as a red acicular crystal.

[0090] Yield: 30%.

[0091] .sup.1H NMR (400 MHz, CDCl.sub.3): ?10.443-10.457 (d, 1H), ?8.906-8.927 (d, 1H), ?8.159-8.179 (d, 1H), ?7.913-7.932 (d, 1H), ?7.787-7.826 (t, 1H), ?7.709-7.722 (d, 1H), ?7.612-7.645 (t, 1H), ?7.454-7.505 (t, 1H), ?7.249-7.351 (m, 2H), ?7.087-7.110 (t, 2H), ?6.847-6.886 (m, 2H), ?6.406-6.475 (m, 2H), ?2.794 (s, 3H), ?2.603 (s, 3H).

[0092] IR (KBr, cm.sup.?1): 3095 (w), 3059 (m), 1631 (m), 1589 (s), 1460 (s), 1417 (m), 1354 (w), 1340 (w), 1242 (w), 1136 (s), 1020 (w), 982 (w), 945 (w), 754 (m), 619 (w).

6. Gas Chromatography Experiments

[0093] (1) Gas chromatography was used to determine the gas composition during the reactions, and the conditions are as follows: the potential is not less than 0.5 V vs Cp.sub.2Fe.sup.+/0, and the electrolyte is an organic solution containing 0-0.1 mM coordination complex 1, 2, 3, 4 or 5, 0.1 M [NBu.sub.4][PF.sub.6], and 0-2.5 M NH.sub.3.

[0094] (2) At different time stages of electrolysis, 100 ?L of upper gas was drawn off with a gastight syringe and injected into a gas chromatograph to obtain the gas composition and content in the electrolytic cell.

[0095] The results are as follows: after 24 h of electrolysis, 375.4 ?mol H.sub.2 and 7.4 ?mol N.sub.2 were produced with coordination complex 1, 459.5 ?mol H.sub.2 and 6.32 ?mol N.sub.2 were produced with coordination complex 2, and 1458.35 ?mol H.sub.2 and 10.55 ?mol N.sub.2 were produced with coordination complex 3. After 48 h of electrolysis, 86.08 ?mol H.sub.2 and 5.85 ?mol N.sub.2 were produced with coordination complex 5. The gas chromatography experiments reveals that the ratio of H.sub.2 to N.sub.2 in the system ranges from 10:1 to 200:1, which is much higher than the ratio of hydrogen to nitrogen in an ammonia molecule (3:1). During the electrolysis, the positive electrode products were all NH.sub.2NH.sub.2 in addition to N.sub.2, and no NO.sub.2.sup.?, NO.sub.3.sup.? and the like were produced.

7. Ultraviolet-Visible Spectroscopy Experiments

[0096] (1) To a 10 mL cuvette, 0.4 mL of the electrolysis solution, 0.5 mL of HCl (0.6 mol/L) solution and 0.5 mL of p-C.sub.9H.sub.11NO in ethanol were added. The mixture was diluted with water to 10 mL and reacted for 1 h.

[0097] (2) 0.5 mL of the reaction mixture was diluted to 10 mL in a 10 mL cuvette. The absorption intensity at 455 nm was measured on an ultraviolet-visible spectrometer, and the NH.sub.2NH.sub.2 content in the electrolysis solution was obtained from the NH.sub.2NH.sub.2 concentration-455 nm absorbance standard curve through the measured intensity.

[0098] The results are as follows: after 24 h of electrolysis, 341.2 ?mol, 423.0 ?mol and 1380.04 ?mol NH.sub.2NH.sub.2 were produced with coordination complexes 1, 2 and 3, respectively.

[0099] The main method of the present invention for preparing coordination complexes 1, 2, 3, 4 and 5 and the characteristics of electrocatalytic ammonia oxidation are shown and described above.

[0100] It will be understood by those skilled in the art that the present invention is not limited to the examples described above. The examples described above and the descriptions in the specification are only intended to illustrate the principles and procedures of the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention, and these changes and improvements all fall within the protection scope of the present invention. The protection scope of the present invention is defined by the appended claims and equivalents thereof.