DE102013202524A1 - Preparing monopotassium-2,4,6-trifluorobenzene-1,3,5-tricarboxylate useful for preparing metal-organic frameworks, comprises oxidizing 3,5-dimethyl-2,4,6-trifluorobenzoic acid or its salt with potassium permanganate - Google Patents

Abstract

Preparing monopotassium-2,4,6-trifluorobenzene-1,3,5-tricarboxylate (I), comprises oxidizing 3,5-dimethyl-2,4,6-trifluorobenzoic acid or its salt with potassium permanganate. Independent claims are also included for: (1) (I), preferably crystalline (I) prepared by the above method; and (2) metal-organic frameworks which as linker component comprises 2,4,6-trifluorobenzene-1,3,5-tricarboxylate structure, and are obtainable by reacting (I) with precursor compounds of metallic nodes of the metal-organic frameworks.

Description

The invention relates to monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate, i.e., the monopotassium salt of trifluorotriminic acid, a process for its preparation and its use for the preparation of MOFs.

Background of the invention

Metal-organic frameworks (MOFs) are discussed as gas storage facilities (including for hydrogen). Theoretical work predicts an increased hydrogen uptake capacity and stronger binding of hydrogen to the MOF pores when perfluorinated linkers are used. In addition, MOFs with perfluorinated linkers are attributed a higher chemical and thermal capacity and special adsorption properties in the hydrophobic region. The most commonly used linkers in the synthesis of MOFs to date are the anions of terephthalic acid and trimesic acid. Such MOFs are for example in US 5,648,508 . EP-A-0 790 253 . M. O'Keeffe et al., J. Solid State Chem. 152: 3-20 (2000) . H. Li et al., Nature 402: 276-279 (1999) . M. Eddaoudi et al., Topics in Catalysis 9: 105-111 (1999) . Chen et al., Science 291: 1021-1023 (2001) . DE-A-101 11 230 . DE-A 10 2005 053430 . WO-A 2007/054581 . WO-A 2005/049892 and WO-A 2007/023134 described. Beyond that mentioned WO 99/05151 MOFs from 1,3,5-benzenetricarboxylates which may optionally have halogen atoms at the free positions of the benzene. However, concrete halogenated compounds are not mentioned.

The synthesis of perfluorinated trimesic acid (C ₆ F ₃ (COOH) ₃ ) has so far only been described very insufficiently twice in the literature (VE Platonov et al., Jr. B. Acad Sci. USSR Ch (English translation) 2606-2608 (1968) ; VE Platonov Zhurnal Organicheskoi Khimii 27: 2183-2191 (1991) ) by oxidation of perfluoromesitylene. Neither an isolated product nor its properties have been studied. Moreover, the preparation of triiodotricitylene and permanganate triiodotric acid is known (eg US 2005/0070735 ). However, the application of this process for the preparation of trifluorotrimesic acid is not known.

Brief description of the invention

• (1) ein Verfahren zur Herstellung von Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylat, umfassend die Oxidation von 3,5-Dimethyl-2,4,6-trifluorbenzoesäure bzw. eines Salzes von 3,5-Dimethyl-2,4,6-trifluorbenzoesäure mit Kaliumpermanganat und optional nachfolgendes Ausfällen des Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylats;
• (2) eine bevorzugte Ausführungsform des Verfahrens (1), zur Herstellung von kristallinem Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylat, umfassend die folgenden Schritte (a) Erhitzen einer Lösung von 3,5-Dimethyl-2,4,6-trifluorbenzoesäure bzw. eines Salzes von 3,5-Dimethyl-2,4,6-trifluorbenzoesäure mit Kaliumpermanganat, (b) Abfiltern des ausgefallenen Braunsteins, (c) Einengen und Ansäuern des Filtrates und (d) Ausfällen und Abtrennen des Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylats,
• (3) Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylat, insbesondere kristallines Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylat, das nach dem Verfahren nach (2) erhältlich ist;
• (4) Verwendung des Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylats nach (3) zur Herstellung von Metall-organischen Gerüsten (MOFs); und
• (5) Metall-organische Gerüste (MOFs), die als Linkerkomponente eine 2,4,6-trifluorbenzol-1,3,5-tricarboxylatstruktur aufweisen und durch Umsetzen von Monokalium-2,4,6-trifluorbenzol-1,3,5-tricarboxylat nach (3) mit Präkursorverbindungen der metallischen Knotenpunkte des MOFs erhältlich sind.

An efficient synthesis of the monopotassium salt of trifluorotriminic acid was now found starting from the commercially available 2,4,6-trifluoro-3,5-dimethylbenzoic acid. This monopotassium salt is water-soluble and therefore suitable for syntheses of MOFs in an aqueous medium with trifluorotrimesate as a linker. The invention thus relates

• (1) a process for producing monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate comprising the oxidation of 3,5-dimethyl-2,4,6-trifluorobenzoic acid and a salt of 3, respectively, 5-dimethyl-2,4,6-trifluorobenzoic acid with potassium permanganate and optional subsequent precipitation of monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate;
• (2) A preferred embodiment of process (1) for the preparation of crystalline monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate, comprising the following steps: (a) heating a solution of 3,5-dimethyl -2,4,6-trifluorobenzoic acid or a salt of 3,5-dimethyl-2,4,6-trifluorobenzoic acid with potassium permanganate, (b) filtering off the precipitated manganese dioxide, (c) concentration and acidification of the filtrate and (d) precipitation and separating the monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate,
• (3) Monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate, especially crystalline monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate, obtainable by the method of (2) is;
• (4) Use of monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate according to (3) for the production of metal-organic frameworks (MOFs); and
• (5) metal-organic frameworks (MOFs) having as a linker component a 2,4,6-trifluorobenzene-1,3,5-tricarboxylate structure and by reacting monopotassium 2,4,6-trifluorobenzene-1,3,5 tricarboxylate according to (3) are obtainable with precursor compounds of the metallic nodes of the MOFs.

Detailed description of the invention

Aspects (1) and (2) of the invention described above relate to processes for the preparation of monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate or crystalline monopotassium 2,4,6-trifluorobenzene-1, respectively. 3,5-tricarboxylate.

In the process according to aspect (2), it is preferred that the process takes place in aqueous solution. Accordingly, an aqueous solution is used in step (a), preferably 100 to 500 ml of water per g of 3,5-dimethyl-2,4,6-trifluorobenzoic acid to be oxidized. Further, it is preferred that the salt of 3,5-dimethyl-2,4,6-trifluorobenzoic acid used in step (a) is in situ by addition of 3,5-dimethyl-2,4,6-trifluorobenzoic acid with a base, preferably in equimolar ratio is generated. Preferably, in step (a), the potassium salt of 3,5-dimethyl-2,4,6-trifluorobenzoic acid is reacted, which is obtainable, for example, by in situ reaction of the acid with equimolar amounts of KOH.

It is further preferred that the reaction of step (a) takes place at pH 7-14, this can be done by adding a suitable buffer such as magnesium chloride. It is also preferred that 4-8, preferably 4.2-6.8 equivalents of potassium permanganate (based on the 3,5-dimethyl-2,4,6-trifluorobenzoic acid to be oxidized) are used.

It is also preferred that reaction (a) be carried out with heating to reflux temperature (preferably for 12 to 48 hours), e.g. is effected by an oil bath temperature of 90 to 130 ° C.

Step (b) may be accomplished by conventional filtration with a blue band filter.

It is further preferred that in step (c) first the volume of the solution is reduced, preferably the volume is reduced to less than 10% of the starting volume (with water to about 10 ml per g of 3,5-dimethyl-2 originally used, 4,6-trifluorobenzoic acid or less).

The acidification in step (c) is preferably carried out by adding a mineral acid, e.g. Hydrochloric acid, adjusting a pH of 2 or lower.

The crystallization in step (d) is preferably carried out with cooling to below 0 ° C.

The process of aspect (2) may further comprise a step (e) of recrystallizing the product obtained in step (d), preferably from water.

It is further preferred that the reaction of aspect (1) and (2), in particular steps (a) and (c) of aspect (2), be carried out in plastic or Teflon vessels to prevent contamination of the product with KBF ₄ and K ₂ SiF ₆ to prevent.

Aspects (4) and (5) of the invention relate to the production of MOFs. This can be done under usual conditions, as detailed in WO 2012/077030 described by reacting the salt of trifluorotrimesin with a precursor compound of the metallic node, z. B. a complexed salt ion of the metallic node.

The invention is explained in more detail below with reference to the following examples. However, these are not to be considered as limiting the invention

Examples

Example 1: General procedure for the synthesis of monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate (1).

1 g (4.9 mmol, 1 eq) of 3,5-dimethyl-2,4,6-trifluorobenzoic acid was suspended in 300 ml of water, treated with 0.3 g of potassium hydroxide (4.9 mmol, 1 eq) and boiled heated. To the solution was added 3.25 g (20.5 mmol, 4.2 eq) of potassium permanganate. The mixture was then refluxed for 24 h, whereupon the violet suspension discolored and manganese precipitated. This was filtered off with suction through Blauband filter and the clear, colorless filtrate was concentrated to about 10 ml. It was with conc. Hydrochloric acid (w = 37%) in a plastic vessel acidified (pH = 1), wherein after about 20 min. a white solid precipitated in the freezer. This was filtered with suction and recrystallized from water. In this way, single crystals could be obtained for single crystal structure analysis. Yield: 0.65 g (2.1 mmol, 44% of theory); Mp .: 250 ° C (decomp.).
¹⁹ F NMR (282 MHz, D ₂ O) = -110.64 ppm (s, 3F).
¹³ C-NMR (75 MHz, C, F-APT, D ₂ O) = 164.55 ppm (s), 157.75 ppm (s), 111.15 ppm (s).
IR (in cm ^-1 ): 3467 (m), 3043 (m), 2981 (m), 2640 (w), 2522 (m), 2483 (m), 1974 (w), 1733 (s), 1619 ( s), 1457 (m), 1425 (w), 1396 (m), 1263 (s), 1214 (m), 1103 (m), 879 (m), 869 (m), 806 (w), 744 ( m), 674 (m), 484 (m), 453 (w).
MS (EI, 20 eV): m / z = 220, 203, 176, 159, 131, 44, 36, 18.
Elemental analysis: _{ber: 35.77%;.} C _exp. : 35.48%; _Calc .: 0.67%; H _exp. : 0.68%. Example 2: Reaction parameters in the synthesis of monopotassium 2,4,6-trifluorotrimesic acid

Investigated reaction parameters:

Reaction temperature: The synthesis should be carried out in Teflon flasks, since use of glass flasks at high temperatures (oil bath> 130 ° C) leads to reaction with the glass wall. This could be detected by contamination of the products with KBF ₄ and K ₂ SiF ₆ . Nevertheless, both reactions can be carried out in glass flasks, if the temperature is chosen between 90 ° C and 130 ° C and the reaction mixture is stirred well.

pH: The pH value must not be less than 7. The reaction works well in the range of pH 7 to pH 14. By adding 3eq magnesium chloride, the pH can be kept constant at about 9-10. This does not affect the yield.

Acidification with HCl _(aq) after the reaction must be carried out in a plastic container. The use of glass vessels leads to contamination with K ₂ SiF ₆ and KBF ₄ .

The results are summarized in Table 1 below.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5648508 [0002]
• EP 0790253 A [0002]
• DE 10111230 A [0002]
• DE 102005053430 A [0002]
• WO 2007/054581 A [0002]
• WO 2005/049892 A [0002]
• WO 2007/023134 A [0002]
• WO 99/05151 [0002]
• US 2005/0070735 [0003]
• WO 2012/077030 [0015]

Cited non-patent literature

• M. O'Keeffe et al., J. Solid State Chem. 152: 3-20 (2000) [0002]
• H. Li et al., Nature 402: 276-279 (1999) [0002]
• M. Eddaoudi et al., Topics in Catalysis 9: 105-111 (1999) [0002]
• Chen et al., Science 291: 1021-1023 (2001) [0002]
• (VE Platonov et al., Jr. B. Acad Sci. USSR Ch (English translation) 2606-2608 (1968) [0003]
• VE Platonov Zhurnal Organicheskoi Khimii 27: 2183-2191 (1991) [0003]

Claims (10)

 A process for the preparation of monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate comprising the oxidation of 3,5-dimethyl-2,4,6-trifluorobenzoic acid or of a salt of 3,5-dimethyl 2,4,6-trifluorobenzoic acid with potassium permanganate. A process according to claim 1, in particular for the preparation of crystalline monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate, comprising the following steps (a) heating a solution of 3,5-dimethyl-2,4,6-trifluorobenzoic acid or a salt of 3,5-dimethyl-2,4,6-trifluorobenzoic acid with potassium permanganate, (b) filtering off the precipitated manganese dioxide, (c) concentration and acidification of the filtrate and (d) precipitating and separating the monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate. The method of claim 2, wherein in step (a) (i) using an aqueous solution, preferably 100 to 500 ml of water per g of 3,5-dimethyl-2,4,6-trifluorobenzoic acid, and / or (ii) the salt of 3,5-dimethyl-2,4,6-trifluorobenzoic acid is generated by adding 3,5-dimethyl-2,4,6-trifluorobenzoic acid with a base, preferably in an equimolar ratio, and / or (iii) reacting the potassium salt of 3,5-dimethyl-2,4,6-trifluorobenzoic acid; and or (iv) the reaction is at pH 7-14, and / or (v) 4-8, preferably 4.2-6.8 equivalents of potassium permanganate are used, and / or (vi) the reaction is carried out with heating to reflux temperature, preferably for 12 to 48 hours. Method according to claim 2 or 3, wherein in step (c) (i) the volume of the solution is reduced to less than 10% of the initial volume, and / or (ii) the acidification comprises the addition of a mineral acid, especially hydrochloric acid, with adjustment of a pH of 2 or lower. Method according to one or more of claims 2 to 4, wherein step (d) taking place under cooling to below 0 ° C.  Method according to one or more of claims 2 to 5, further comprising step (e), recrystallizing the product obtained in step (d). Method according to one or more of claims 1 to 6, wherein the reaction takes place in plastic or Teflon vessels. Monokalium-2,4,6-trifluorobenzene-1,3,5-tricarboxylate, in particular crystalline monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate, which is obtained by a process according to one or more of claims 2 to 7 is available. Use of the monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate according to claim 8 for the preparation of metal-organic frameworks (MOFs). Metal-organic frameworks (MOFs) which have a 2,4,6-trifluorobenzene-1,3,5-tricarboxylate structure as the linker component and by reacting monopotassium 2,4,6-trifluorobenzene-1,3,5-tricarboxylate according to Claim 8 are available with precursor compounds of the metallic nodes of the MOF.