JPS6126794B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to aromatic carboxylic acid primary cobalt salt compounds. More specifically, the present invention relates to a novel compound in which four methanol molecules are coordinated to a cobalt first salt of an aromatic carboxylic acid. Conventionally, cobalt salts of aromatic carboxylic acids have been used as catalysts for various oxidation reactions (see, for example, U.S. Pat. No. 2,712,549 and U.S. Pat. No. 2,715,51), as well as esterification or transesterification reactions, and as drying agents for varnishes and paints. It is known that it can be used as a rust inhibitor. These known cobalt salts of aromatic carboxylic acids, such as cobalt benzoate, and commonly known synthesis methods, such as the reaction of cobalt chloride and sodium aromatic carboxylate (for example, inorganic compounds published by Maruzen, "New Experimental Chemistry Course 8") Synthesis (see synthesis) is almost insoluble in water and various organic solvents, so
When used as a catalyst for reactions such as oxidation and esterification, the concentration of the catalyst is limited by itself, and therefore the reaction rate cannot be increased sufficiently and side reactions may occur. Also, when dissolved in various solvents and used as a drying agent or rust preventive agent for paint, it may not be possible to obtain a highly concentrated product, or it may cause problems such as clogging or unevenness during wheel feeding. . The present inventors conducted research on cobalt first salts of aromatic carboxylic acids, and as a result, discovered a compound of cobalt first salts of aromatic carboxylic acids that are soluble in organic solvents, and arrived at the present invention. That is, the present invention is based on the following general formula (1) [However, in the formula, X is a hydrogen atom, a methyl group, or -
Showing COOCH ₃ . ] This is an aromatic carboxylic acid primary cobalt salt compound represented by: The cobalt compound of the present invention represented by the above formula (1) has two aromatic carboxyl groups as ligands per cobalt atom, and also has four methanol molecules coordinated. It is a compound. If the cobalt compound of formula (1) is left in the atmosphere for a long time in the absence of methanol or left in a vacuum state, the methanol molecules will detach and eventually the coordination of methanol will occur. It is converted into a compound that exhibits the same behavior as ordinary aromatic carboxylic acid cobalt salts, which have extremely low solubility in organic solvents. This phenomenon can also be known by observing the color of the compound of formula (1). That is, the cobalt compound of the formula (1) in which the four methanols are coordinated exhibits a pale pink color, but as the coordinated methanol leaves, the color changes to purple and gradually changes to blue. In addition, it is relatively easy to return to the original state in the presence of methanol as long as all of the coordinated methanol is not released, but once the monocoordinated methanol is completely released, it is easy to return to the original state even if brought into contact with methanol. We will not return to the cobalt compound of formula (1) above, which exhibits a pale pink color. For example, after prolonged vacuum drying, the coordination of methanol was completely removed.

Compounds represented by the formula (see Example 1) and commercially available cobalt benzoate

[Formula] (Wako Pure Chemicals) remains insoluble even when heated under reflux with methanol for a long time,
It was observed that the soluble cobalt compound represented by formula (1) coordinated with methanol does not easily return. In order to obtain the compound of the formula (1) in which four methanol molecules are coordinated, it is necessary to perform the treatment under specific conditions as described below, for example. The characteristics of the cobalt compound of formula (1) of the present invention are as follows:
It is soluble in organic solvents, and unlike ordinary cobalt aromatic carboxylic acid which is not coordinated with methanol, it is soluble in various organic solvents.
Such organic solvents include relatively polar organic solvents, such as alcohols such as methanol, ethanol and isopropanol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aldehydes such as acetaldehyde and benzaldehyde; acetic acid and propion. Fatty acids such as acids; Esters such as ethyl acetate and ethyl benzoate; Halogenated hydrocarbons such as chloroform and trichloroethylene; Aprotic polar solvents such as acetonitrile, nitromethane, N・N'-dimethylformamide, and sulfolane; Examples include aromatic hydrocarbons such as benzene, toluene, and xylene. In addition, by dissolving the aromatic carboxylic acid in a small amount of methanol and then mixing it, the aromatic carboxylic acid can be dissolved in less polar solvents that are difficult to dissolve directly, such as aliphatic hydrocarbons such as n-hexane, cyclohexane, and petroleum ether. It is possible to obtain a homogeneous solution of 1 cobalt salt. The thus obtained homogeneous solution of the cobalt aromatic carboxylic acid salt uniformly dissolved in various organic solvents can be used efficiently for various purposes depending on the purpose. An example of a useful use of the organic solvent-soluble cobalt salt represented by the above formula (1) is when it is used as a catalyst for oxidation reactions, esterification, and transesterification reactions. A particularly effective example is the so-called solvent-free oxidation of alkyl-substituted aromatic compounds such as toluene, para-xylene, methyl para-toluic acid, etc. without using an acetic acid solvent. With conventional insoluble cobalt salt compounds, the catalyst is not uniformly dissolved in the reaction system, resulting in an induction period before the reaction starts, a slow reaction rate, or a corresponding increase in side reactions. However, by using the soluble cobalt aromatic carboxylate shown by the above formula (1), it is uniformly dissolved in the reaction system from the beginning, so there is no reduction in the induction period, reaction rate, side reactions, etc. can be suppressed. Furthermore, similar effects can be seen in solventless transesterification reactions of aromatic carboxylic acid esters. The aromatic carboxylic acid cobalt salt compound of the general formula (1) in the present invention exhibits an endothermic reaction when the four methanols are released, and the methanol is converted into methanol without completing the removal of the methanol and the reaction. Taking advantage of the fact that it returns to the original compound (1) when brought into contact, the cycle of endotherm and exotherm can be repeated. This can also be used as a thermal and light energy absorber in thermal storage systems that absorb solar energy. In addition, due to its high solubility, it can also be used as a dryer (drying agent additive) for lacquer, paint, etc. The compound represented by the above formula (1) can be prepared, for example, by the following method. Commercially available cobalt acetate [Co(OCOCH ₃ ) ₂・4H ₂ O] and a slight excess of the following formula (2) [Here, X represents H, _-CH3 or _-COOCH3 . ] A divalent cobalt anhydride aromatic compound obtained by heating the aromatic carboxylic acid represented by the formula in a solvent with a boiling point higher than that of acetic acid to distill off water and acetic acid and replace acetate ions with the aromatic carboxylic acid ions. For any of the carboxylates, crystals exhibiting a deep purple color can be obtained, and by immediately recrystallizing this compound from methanol or a solvent containing methanol, the aromatic carbon of cobalt represented by the above formula (1) can be obtained. Acid salts can be obtained. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Commercially available cobalt acetate tetrahydrate [Co
(OCOCH ₃ ) ₂・4H ₂ O〕0.01 mol and para-toluic acid

[Formula] Heat and dissolve 0.025 mol in about 20 ml of methanol, and add 100 mol of xylene to this.
ml and heated on an oil bath at normal pressure to gradually distill off the solvent. The distillate contains the solvents methanol and xylene, as well as water and acetic acid. The distillate was titrated using a 0.1N aqueous solution of caustic soda and the amount of acetic acid distilled was determined.
It was found that 95% of acetic acid had been distilled out. Add about 10ml of methanol to the distillation residue to dissolve it, and then add 50ml of it again.
of xylene is added and distilled off by heating on an oil bath. When the amount of acetic acid distilled was determined by alkaline titration together with the second distillate, it was confirmed that 200 mmol (100%) of acetic acid had been distilled. Add 10ml of methanol to dissolve the resulting distillation residue, then add 100ml of toluene and heat on an oil bath to 100-110℃.
When methanol is almost completely distilled off, blue-purple crystals begin to precipitate. After sufficient crystals have formed, heat the mixture to remove the solvent toluene and excess para-toluic acid. Repeat this operation twice to thoroughly remove excess para-toluic acid. The obtained divalent cobalt paratoluate was 3.18g.

The yield is 96.7% as [Formula]. The blue-purple crystals obtained here are then heated and dissolved in methanol and allowed to cool, yielding pink scale-like crystals. After drying this crystal under reduced pressure (10 mmHg), take a portion of it, add 12N hydrochloric acid to decompose it, and then measure the cobalt content by EDTA titration (Reference: "New Experimental Chemistry Course 9" Analytical Chemistry [1] P338) The result is 12.51% (

[Formula] is Co theoretical value 1288%). In addition, organic substances generated by hydrochloric acid decomposition were extracted with chloroform and subjected to gas chromatography [Model: Shimadzu GC-6A, Column: Shimadzu Tenax GC 1m, Temperature 90℃, Carrier gas
After confirming the presence of methanol with N ₂ ] and converting para-toluic acid into para-toluic acid methyl ester with a diazomethane ether solution, gas chromatography [Model: Hitachi 063, Column: Polyethylene glycol 20M 5%, Length: 2 meters, 100°C than 7
When analyzed using carrier gas nitrogen and heating at a rate of °C/min, it was found to be 59.80% by weight in terms of para-toluic acid.
It was hot.
[

Theoretical amount calculated as free para-toluic acid as [Formula]: 59.53
%]. On the other hand, the chloroform layer was washed with water and then evaporated to dryness, yielding almost pure para-toluic acid of 59.60% relative to the original crystals, which showed good agreement with the above gas chromatography results. A portion of this crystal was weighed in advance and vacuum dried (2 mmHg) in a vacuum desiccator overnight. As the color of the crystal changed from pink to blue, it also lost 269% of its weight. [ The theoretical weight reduction is 28.0%]. The dried blue crystals were decomposed with 12N concentrated hydrochloric acid, and cobalt and paratoluic acid were quantified using the method described above. As a result, cobalt was 17.41% and paratoluic acid was 82.20%.

[Formula], the theoretical amount is 17.90% as cobalt atoms and 82.71% as free para-toluic acid]. As a result, the composition formula of the pink scaly crystals obtained by recrystallization from methanol is It can be shown as The compositional formula of the blue crystals obtained by drying in vacuum for a long time is that methanol is out of coordination.

[KBr ^- disk unit is cm ^-1 , inside the box indicates absorption intensity w = weak, m = medium, s = strong, vs = particularly strong]

619 (m), 690 (w), 761 (s), 845 (w),
1018(w), 1112(w), 1176(s), 1290
(m), 1405 (vs), 1545 (wide width 1520-1560)
(vs), 1598 (s), 1610cm ^-1 (vs), 2930cm ^-1
(w)3040(w)

[Formula] 619cm ^-1 (m), 690 (m), 758 (s), 810
(s), 845cm ^-1 (w), 1015 (w), 1109 (w),
1140 (w), 1178cm ^-1 (s), 1292 (w), 1405
(vs), 1540 (wide width 1530-1560) (vs), 1595
(vs), 2930cm ^-1 (w), 3040cm ^-1 (w) Example 2 and Comparative Examples 1 and 2 Composition formula obtained in Example 1

The solubility of the crystal represented by the formula in various solvents was examined. At the same time, the composition formula obtained in Example 1

Crystals represented by [Formula] (Comparative Example 1) and cobalt chloride in methanol
Prepared by the reaction of CoCl ₂ 6H ₂ O and 2 times the mole of para-toluic acid potassium salt

[Formula] Salt (Comparative Example 2) This is a comparison of solubility.

【table】

[Table] Examples 3 and 4 In the same manner as in Example 1, benzoic acid and terephthalic acid monomethyl ester were used instead of para-toluic acid, and both divalent cobalt salts containing methanol as a ligand were obtained as pink crystals. Ta. Their composition formulas and analysis results are shown in the table below.

[Table] Example 5 and Comparative Example 3 Composition formula obtained in Example 3

The solubility of the divalent cobalt salt compound represented by the formula and commercially available cobalt benzoate (compositional formula Co(OCO-〇) ₂ , manufactured by Wako Pure Chemical Industries, Ltd.) in various organic solvents is compared.

【table】

Claims (1)

[Claims] 1 The following general formula (1) [However, in the formula, X is a hydrogen atom, a methyl group, or -
Showing COOCH ₃ . ] An aromatic carboxylic acid primary cobalt salt compound represented by: