RU2460687C1 - Method of producing phosphorous acid from white phosphorus - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: organic complex of palladium - tris(dibenzylidene acetone)palladium reacts with white phosphorus in a tetrahydrofuran medium. The palladium phosphides formed undergo hydrolysis at temperature 20-70°C with degassed water. Molar ratio of reactants palladium complex: white phosphorus: water is equal to 1:(1-20):(12-480). The end product is extracted by separating the residue and evaporating the filtrate in a vacuum.

EFFECT: method is environmentally safe, selective and enables to obtain phosphorous acid from simple and readily available reactants with high output.

3 cl, 1 tbl, 11 ex

Description

The invention relates to a method for producing phosphorous acid, which is widely used in the production of various phosphorus-containing compounds used as complexones, reducing agents, polymer stabilizers, biologically active compounds.

The American company "Monsanto" has developed a number of methods for producing phosphorous acid from elemental (white, yellow) phosphorus. The electrolytic production of phosphorous acid from white phosphorus is described [US 4021321, publ. 05/05/1977; US 4021322, publ. 05/03/1977]. The disadvantage of this method is that the phosphorous acid formed in the process is contaminated with impurities of phosphoric acid and chlorine and requires additional purification, and the hydrochloric acid formed as a by-product has corrosive activity. The method also requires significant energy costs.

A known method of producing phosphorous acid by oxidation of elemental phosphorus with water vapor in the gas phase [CA 2013221, publ. 1.02.1990] or gas plasma [CA 2070949, publ. 12/11/1993]. The disadvantages of these methods are the process at high temperatures (more than 1000 ° C, 1500-2500 ° C), which requires special precautions when working with elemental (white) phosphorus, as well as the formation of by-products of the polymerization of elemental (white) phosphorus - the formation of red phosphorus.

A known method of producing phosphorous acid from phosphorus sludge formed during the production of yellow phosphorus [RU 2096318, publ. 11/20/1997]. The disadvantage of this method is the use of a large amount of concentrated nitric acid and iodine.

A known method of producing phosphorous acid by the reaction of elemental (white, yellow) phosphorus with barium and calcium hydroxides in the presence of base and water [RU 2179152, publ. 02/10/2002]. Although no toxic phosphine is released under the conditions of this process, the formation of large amounts of insoluble calcium and barium sulfates and the use of excess corrosion-hazardous diluted sulfuric acid are disadvantages of the proposed method.

A known method of producing a mixture of phosphorus-containing acids under the conditions of catalytic oxidation of elemental (white, yellow) phosphorus under the influence of noble metals such as palladium and some other metals of group VIII [US 6476256, publ. November 5, 2002]. The disadvantages of this process are the formation of a mixture of phosphorus-containing acids, low yields of phosphorous acid (up to 57.4% in a mixture with other acids), the formation of toxic phosphine and the heterogeneous course of the process, since elemental (white) phosphorus is insoluble in an aqueous medium. To increase the yield of phosphorous acid in this method, it is necessary to use a special autoclave and increase the temperature to 90-150 ° C.

The listed technical solutions are analogues of the present invention. Closest to the claimed invention is a method for producing phosphorous acid by reacting an organic complex of palladium - bis (triphenylphosphine) palladium dibromide with elemental (white) phosphorus in the presence of NaBPh ₄ , followed by hydrolysis of the reaction mixture [Izvestiya Akademii Nauk. Chemical Series, 2010, 59 (6), 1094-1096], which allows to obtain phosphorous acid from elemental phosphorus in a yield of up to 75%. However, this method requires an additional activation process of the used palladium complex, which leads to contamination of the obtained product with impurities of sodium bromide. The resulting phosphorous acid is contaminated with impurities of phosphoric and pyrophosphoric acids, constituting up to 40%, and the presence of triphenylphosphine in the reaction medium leads to the formation of additional organophosphorus impurities as a result of its partial oxidation.

The objective of the invention is the creation of a new environmentally friendly, industrially acceptable and selective method for producing phosphorous acid based on simple and affordable reagents (P ₄ , H ₂ O, organic palladium complex) in high yield, expanding the range of known methods for producing phosphorous acid.

EFFECT: new selective method for producing phosphorous acid with a yield of up to 90%

The technical result is achieved by the claimed method of producing phosphorous acid from white phosphorus by the interaction of the organic complex of palladium - tris (dibenzylideneacetone) dipalladium with white phosphorus in tetrahydrofuran medium, followed by hydrolysis of the resulting palladium phosphides with degassed water in the following molar ratio of reagents - palladium complex : white phosphorus: water 1: (1-20) :( 12-480) and isolating the target product by separating the precipitate and evaporating the filtrate in vacuo.

Based on the data of NMR ³¹ P-spectroscopy, it was found that during the implementation of the proposed method, the formation of one product occurs - phosphorous acid. Thus, in the ³¹ P {-} NMR spectrum taken from the obtained product, a doublet with a chemical shift of +3.8 ppm is observed. and the phosphorus-hydrogen interaction constant ¹ J _PH = 667 Hz.

The chemical process underlying the proposed method includes the reaction of tris (dibenzylideneacetone) dipalladium [Pd ₂ (dba) ₃ ] with white phosphorus in tetrahydrofuran medium followed by hydrolysis of the resulting palladium phosphides with degassed water (Scheme 1):

After hydrolysis, the isolation of the target product includes separation of the precipitate of the palladium compound, evaporation of the filtrate in a vacuum of an oil pump and (if necessary) additional purification by recrystallization [Guide to inorganic synthesis. T.2. Per. with him. / Ed. G. Brauer. - M .: World. 1985. - S.580-581]. In total, the process of obtaining phosphorous acid from elemental phosphorus in the presence of a palladium complex [Pd ₂ (dba) ₃ ] is presented in scheme 2:

The following examples illustrate an embodiment of the invention. All experiments were carried out in an inert atmosphere of nitrogen using standard Schlenk equipment. White phosphorus was stored under a layer of water and immediately before the experiment, it was washed successively with acetone, ethyl alcohol and ether, followed by drying in vacuum, a 0.05 M solution of white phosphorus in THF was prepared by dissolving a portion of P ₄ in an appropriate volume of solvent. The organic palladium complex [Pd ₂ (dba) ₃ ] was used by Alfa Aesar (No. 12760). The ³¹ P NMR spectra were recorded on a Bruker Avance DRX-400 NMR spectrometer at a frequency of 161.97 MHz. For clarity, the conditions for producing phosphorous acid from white phosphorus according to examples 1-11 are summarized in the table.

Example 1

To a solution containing 54.9 mg (0.06 mmol) of the complex [Pd ₂ (dba) ₃ ] in 5 ml of THF, 1.2 ml of a 0.05 M solution of white phosphorus in THF containing 7.4 mg (0.06 mmol) of P _{4 is} slowly added dropwise. After adding a solution of white phosphorus, the formation of a black amorphous precipitate of palladium phosphides is observed, which, when stirred for 1 hour, acquires crystallinity. After that, 13 μl (0.72 mmol) of degassed water was added to the reaction mixture, stirred at room temperature (20 ° C) for 10 hours, the precipitate of the palladium compound was separated, and the filtrate was evaporated in vacuo of an oil pump to obtain 12.8 mg of phosphorous acid H ₃ PO ₃ in the form of a colorless crystalline hygroscopic precipitate with a melting point of 70 ° C ( ³¹ P NMR, THF, C ₆ D ₆ -capillary, δ, 3.8 ppm (d), ¹ J _PH = 667 Hz). The yield is 65%.

Example 2

The method is carried out under the conditions of example 1, but using 2.4 ml of a 0.05 M solution of white phosphorus containing 14.8 mg (0.12 mmol) of P ₄ and 26 μl (1.44 mmol) of degassed water. Received 20.9 mg of H ₃ PO ₃ . The yield is 53%.

Example 3

The method is carried out under the conditions of example 2, but at a temperature of 50 ° C. Received 28.3 mg of H ₃ PO ₃ . The yield is 72%.

Example 4

The method is carried out under the conditions of example 1, but using 12.0 ml of a 0.05M solution of white phosphorus containing 74.0 mg (0.6 mmol) of P ₄ and 0.13 ml (7.2 mmol) of degassed water. Obtained 94.5 mg of H ₃ PO ₃ . The yield is 48%.

Example 5

The method is carried out under the conditions of example 1, but using 24.0 ml of a 0.05M solution of white phosphorus containing 148 mg (1.2 mmol) of P ₄ and 0.26 ml (14.4 mmol) of degassed water. Received 173.2 mg of H ₃ PO ₃ . The yield is 44%.

Example 6

The method is carried out under the conditions of example 2, but using 0.26 ml (14.4 mmol) of degassed water. 30.3 mg of H ₃ PO ₃ obtained. The yield is 77%.

Example 7

The method is carried out under the conditions of example 6, but at a temperature of 50 ° C. Obtained 33.1 mg of H ₃ PO ₃ . The yield is 84%.

Example 8

The method is carried out under the conditions of example 6, but at a temperature of 70 ° C. Received 35.4 mg of H ₃ PO ₃ . The yield is 90%.

Example 9

The method is carried out under the conditions of example 6, but using 0.52 ml (28.9 mmol) of degassed water. Received 18.9 mg of H ₃ PO ₃ . The yield is 48%.

Example 10

The method is carried out under the conditions of example 9, but at a temperature of 50 ° C. Received 19.3 mg of H ₃ PO ₃ . The yield is 49%.

Example 11

The method is carried out under the conditions of example 9, but at a temperature of 70 ° C. Received 22.8 mg of H ₃ PO ₃ . The yield is 58%.

The experiments were carried out at the following molar ratios of the reagents: complex [Pd ₂ (dba) ₃ ]: white phosphorus: water 1: (1-20) :( 12-480). The indicated ratios are sufficient to obtain the target product, and as can be seen from the table, the best yields of phosphorous acid (examples 6-8) are achieved with a molar ratio of the complex [Pd ₂ (dba) ₃ ]: white phosphorus 1: 2. Increasing the amount of water used, i.e. more than 120 mol per 1 mol of phosphorus, leads to the formation of dilute solutions and complicates the isolation of the product and, ultimately, to reduce the yield. It was found that the temperature at which the hydrolysis of the resulting palladium phosphides is carried out also affects the yield of the target product. The optimal conditions for implementing the method are as follows:

the molar ratio of the complex [Pd ₂ (dba) ₃ ]: white phosphorus: water 1: 2: 240;

- hydrolysis at a temperature of 50-70 ° C.

Thus, the proposed method for producing phosphorous acid from white phosphorus is environmentally friendly, because the formation of by-products, including toxic phosphine, does not occur, it is economical, because the process proceeds under homogeneous conditions at room temperature or when heated to 70 ° C, it is selective (phosphorous acid is formed as the only product), based on simple and affordable starting reagents (white phosphorus, H ₂ O, commercially available palladium complex) with the yield of the target product up to 90%.

Table Conditions for the production of phosphorous acid from white phosphorus No pp Reagents Yield ^* H ₃ PO _3, % [Pd ₂ (dba) ₃ ] mg [Pd ₂ (dba) ₃ ] mmol P ₄ mg P ₄ mmol H ₂ O, μl H ₂ O, mmol T, ° C The molar ratio [Pd ₂ (dba) ₃ ]: P ₄ : H ₂ O one 54.9 0.06 7.4 0.06 13 0.72 twenty 1: 1: 12 65 2 54.9 0.06 14.8 0.12 26 1.44 twenty 1: 2: 24 53 3 54.9 0.06 14.8 0.12 26 1.44 fifty 1: 2: 24 72 four 54.9 0.06 74.0 0.6 130 7.2 twenty 1: 10: 120 48 5 54.9 0.06 148.0 1.2 260 14.4 twenty 1: 20: 240 44 6 54.9 0.06 14.8 0.12 260 14.4 twenty 1: 2: 240 77 7 54.9 0.06 14.8 0.12 260 14.4 fifty 1: 2: 240 84 8 54.9 0.06 14.8 0.12 260 14.4 70 1: 2: 240 90 9 54.9 0.06 14.8 0.12 520 28.8 twenty 1: 2: 480 48 10 54.9 0.06 14.8 0.12 520 28.8 fifty 1: 2: 480 49 eleven 54.9 0.06 14.8 0.12 520 28.8 70 1: 2: 480 58 * The yields of phosphorous acid H ₃ PO _{3 are} determined relative to the white phosphorus reacted

Claims (3)

1. A method of producing phosphorous acid from white phosphorus, comprising reacting an organic palladium complex with white phosphorus in tetrahydrofuran medium followed by hydrolysis of the resulting palladium phosphides with degassed water and isolating the target product, characterized in that tris (dibenzylidene acetone) dipalladium is used as the organic complex of palladium the following molar ratio of reactants: palladium complex: white phosphorus: water 1: (1-20) :( 12-480). 2. The method of producing phosphorous acid according to claim 1, characterized in that the hydrolysis is carried out at a temperature of 20-70 ° C. 3. The method of producing phosphorous acid according to claim 1, characterized in that the selection of the target product includes separation of the precipitate and evaporation of the filtrate in vacuum.