WO2009112349A1 - Method for producing diphosphine monoxides - Google Patents

Abstract

The invention relates to a method for producing diphosphine monoxides by reacting dialkyl- or diaryl phosphine chloride with alkoxy dialkyl- or diaryl phosphine without solvents and then separating the product.

Description

 Process for the preparation of diphosphine monoxides

description

The object of the present invention relates to a process for the preparation of diphosphine monoxides by reaction of dialkyl- or diarylphosphine chloride with alkoxydialkyl- or diarylphosphine without solvent and subsequent removal of the product.

There is a great need for Diphosphinmonoxiden which can be used as flame retardants in various plastics such as epoxy resins, polyethylene and polyurethanes. 1, 1, 2,2-Tetraphenyldiphosphinmonoxid (TPDM) is hereby a preferred compound which is used as a halogen-free flame retardant for various applications in the plastics industry.

The coupling of such diphosphines is usually carried out by coupling the corresponding halophosphine with an alkoxyphosphine with elimination and simultaneous removal of the haloalkane in an inert solvent.

The preparation of TPDM can be carried out starting from diphenylphosphine chloride in the presence of metals such as sodium, lithium or magnesium and subsequent oxidation of the tetraphenyldiphosphine with air or other oxidizing agents as described by A. J Blake, G. P McQuillan, I.A. Oxton, D. Troy, J. Mol. Struct. 1982, 78, at pages 265 to 272.

^P1 \ M ^P1 \, ^Ph air ^P \, ^{Ph P1} \ / ^Ph

2 p-ci - P-P - P-P = O + O = P-P = O

Ph'Ph Ph Ph Ph Ph Ph

A disadvantage of this method is not only the two-step process control, but also the increased safety measures that must be made for the production of tetraphenyldiphosphine, as must be taken to handle the air-sensitive alkali metals and the handling of the air-sensitive products. Furthermore, in the coupling reaction large amounts of heat are released, which must be removed accordingly. Further disadvantages are that the oxidation proceeds only with low selectivity and in the reaction the formation of by-products such as tetraphenyldiphosphine dioxide can not be avoided. For use as flame retardants in plastics, however, a mixture of TPDM and tetraphenyldiphosphine dioxide is rather unsuitable because the flame retardant effect of TPDM is reduced by the tetraphenyldiphosphine dioxide. In contrast, D. Hunter, JK Michie, JA Miller, and W. Stewart describe in Phosphorus Sulfur, 1981, 10, at pages 267 to 270, the partial hydrolysis of diphenylchlorophosphine in situ with water. Also J. McKechnie, DS Payne and W. Sim describe in J. Chem. Soc. 1965 on page 3500 this reaction path to TPDM.

In this process, however, only low yield below 36 - 84% of TPDM can be achieved. Furthermore, this process also forms considerable by-products, such as tetraphenyldiphosphine dioxide and diphenylphosphine oxide, which can also reduce the flame retardant effect of TPDM if they were not previously separated from TPDM, which would be an additional work step.

Another method for preparing diphosphine monoxide is described by Inorg. Nucl. Chem. Letters 1967, Vol.3, at page 313. In this case, diphenylphosphine chloride is reacted in the presence of methoxydiphenylphosphine and benzene as the solvent.

In this process, by-products such as tetraphenyldiphosphine dioxide are formed, which can affect the flame retardancy of the TPDM and therefore have to be separated. Even after crystallization, the quality of the product obtained is not sufficient, as is the case of the deviations described in the elemental analysis (C, deviation + 0.6%) and in the melting point (in Inorg Nucl. Chem. Letters 1967, Vol.3, on page 313 described for crystallized product: 158-161 ⁰ C; measured in the product with 94% purity: 161-172 ⁰ C, see example) can be seen below. The procedure of the synthesis of TPDM from E-thoxydiphenylphosphine, which is accessible on an industrial scale, and diphenylch- lorphosphin according to the E. Fluck and H. Binder Inorg. Nucl. Chem. Letters 1967, Vol. 3, at page 313 showed that the resulting product has a purity of <90% and that the crystallization does not lead to a reduction in the content of tetraphenyldiphosphine dioxide. Due to this procedure in a solvent, however, because of the dilution (about 1 M) and the low reaction rate, the space-time yield at about 6 g / L ^* h is low. The object of the present invention is therefore to provide a process which makes it possible selectively to produce diphosphine monoxides which produce less than 10% of secondary components, which allows a simplified work-up and also has an improved reaction time.

This object is achieved by a process for preparing diphosphine monoxides of the formula I.

_R1 R ³ PP = O

R ² R ⁴

I wherein R ¹ -R ^{4 are} independently selected from the group of C 1 -C 16 -alkyl, C 1 -C 16 -alkenyl, C 1 -C ₆ -alkoxy, C 1 -C ₆ -alkyl-NR ² R ³ , Cs-do -cycloalkyl, C3-C10-cycloalkoxy, Cβ-Cio-aryl, Cβ-C-io-aryloxy, Cβ-Cio-aryl-Ci-Ciβ-alkyl, C6-Cio-aryl-Ci-Ci6- alkoxy, NR ² R ³ , COR ² , COOR ² and CONR ² R ³ comprising the step

a) reaction of a compound of formula II

R ¹

with an excess of the compound of formula III at temperatures in the range of 50 to 180 ⁰ C.

R ³

V - OR ⁵ R ⁴

where R ^{5 is} selected from the group of C 2 -C 16 -alkyl, C 1 -C 16 -alkenyl, C 3 -C 10 -cycloalkyl or Cβ-do-aryl !.

b) removal of the product R ⁵ Cl, which is formed in addition to the compound of the formula I, from the mixture and

c) separation of the mixture resulting from step a). The process of the invention is advantageous if the radicals R ¹ to R ^{4 are} all identical.

The process is advantageous if the radicals R ¹ to R ^{4 are} phenyl groups.

The process is advantageous if the radical R ^{5 represents} an ethyl group.

The process is advantageous if step a) is carried out at a temperature in the range from 110 to 130 ^° C.

The process according to the invention is advantageous if the separation of the compound of the formula I in step c) takes place by filtration or centrifugation.

In the process according to the invention, the radicals R ¹ to R ^{4 are} independently selected from the group of C 1 -C 18 -alkyl, C 1 -C 18 -alkenyl, C 1 -C 4 -alkoxy, d-

C 1 -C 6 -alkyl-NR ² R ³ , C ³ -C 10 -cycloalkyl, C 3 -C 10 -cycloalkoxy, Cβ-do-aryl, Cβ-Cio-aryloxy, Cβ-

C ₁ -C 10 -aryl-C ₁ -C ₆ -alkyl, C ₆ -C 10 -aryl-C ₁ -C 16 -alkoxy, NR ² R ³ , COR ² , COOR ² and CONR ² R ³ , are preferred, C 1 -C 16 -alkyl and Cβ- do-arvl groups.

Preferred C 1 -C 16 -alkyl groups are methyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, isobutyl, hexyl, octyl, decyl, dodecyl, tetradecyl, 2-ethylhexyl and 2-methyl.

Propyl-heptyl.

Preferred Cβ-Cio-aryl groups are phenyl and naphthyl. Particularly preferred

Phenyl.

It is very particularly preferred if the radicals R ¹ and R ² and R ³ and R ^{4 are} identical. Especially preferred for R ¹ and R ^{2 is} the phenyl group and for R ³ and R ^{4 is} the phenyl, ethyl and allyl group. Especially preferred is especially when R ¹ to R ^{4 are} phenyl groups.

In the compound of the formula III, the group R 5 is selected from the group of C 2 -C 16 -alkyl, C 1 -C 16 -alkenyl, C 3 -C 10 -cycloalkyl or C 6 -C 10 -aryl.

Preferred C2-C16 alkyl groups are selected from the group of ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, i-butyl, decyl, dodecyl, tetradecyl or 2-ethylhexyl.

Preference is given to the ethyl, n-propyl, i-propyl group. The ethyl group is very particularly preferred. The preferred C 1 -C 16 -alkenyl group is AIIyI.

Preferred C 3 -C 10 -cycloalkyl groups are selected from the group of cyclopentyl and cyclohexyl.

Preferred Cβ-C-io-arvl groups are selected from the group of phenyl, naphthyl, ToIyI, dimethylphenyl and methoxyphenyl. Particularly preferably, the group R 5 is selected from the group of ethyl and

Iyi. The reaction is carried out in the presence of temperatures in the range from 50 to 180 ^° C., more preferably in the range from 80 to 160 ^° C., very particularly preferably in the range from 110 to 130 ^° C.

During step a), an excess of the compound of formula III is added to the compound of formula II. The ratio of compounds of the formula II to III is thus 1: 5, more preferably 1: 2.4.

The process according to the invention can be operated both batchwise, semi-batch and continuously. Preference is given to a semi-batch or continuous procedure. Quite particularly preferred is a continuous mode of operation.

The product R ⁵ Cl formed during the reaction in addition to the compound of the formula I is removed from the reaction mixture. The removal can be carried out by methods known to those skilled in the art, such as stripping, distillation, extraction or phase separation. The process procedure is preferably selected such that the R ⁵ Cl formed in the reaction is gaseous and is produced in such amounts that it can be distilled off safely during the reaction. This is preferably realized by a controlled addition of the compound of formula II to the compound of formula III.

The compound of the formula I which is formed by this process is preferably precipitated as a solid. Some compounds of formula I are also oils. The compound of formula I is then separated from the reaction solution obtained after step b). The separation can be carried out by the methods known to those skilled in the art, such as filtration, centrifuging, extraction, distillation and sublimation.

The product obtained by the process according to the invention may, if appropriate, be subjected to a further purification step once more. Possible purification steps here are recrystallization, washing of the crystallizate, followed by removal of the wash solution under reduced pressure, distillation, sublimation. Preference is given to washing the crystals under ISb or Ar atmosphere, followed by removal of the washing solution under reduced pressure. All organic solvents selected from the group of toluene, xylene, dibutyl ether, alkanes such as hexane, heptane and petroleum ether or mixtures thereof are suitable for washing the crystals.

Examples

Example 1 (according to the invention) Ethoxydiphenylphosphine (552.6 g, 2.40 mol) is placed in a stirred flask and heated to 120 ⁰ C internal temperature. Within 1 h chlorodiphenylphosphine (220.6 g, 1, 0mol) is added dropwise so that the resulting ethyl chloride can be safely removed. It is stirred for a further hour at reaction temperature and then cooled. The crystals are filtered off and washed with toluene. It is dried at the best possible oil pump vacuum and 100 ⁰ C. This gives 347.7 g (0.9 mol) of 1, 1, 2,2-Tetraphenyldiphosphinmonoxid (90% yield) with a purity of 95% (m / m). ³¹ p NMR (toluene-D8): -22.9 (d, ¹ J 224 Hz); 35.1 (d, ¹ J 224 Hz). Bp 172-175 ° C (vacuum).

Example 2 (Comparative Example)

Chlorodiphenylphosphine (22.1 g, 0.1 mol) in toluene (200 ml) is placed in a stirred flask and heated to 100-1 15 ⁰ C internal temperature. Within 2h Ethoxydiphe- nylphosphin (23.03 g, 0.1 mol) is added dropwise. It is stirred for 11 hours under reflux and then cooled. The conversion after 11 hours is 36% according to ³¹ P NMR. The crystals are filtered off and washed with toluene. It is dried at oil pump vacuum and 100 ⁰ C. 1, 1, 2,2-Tetraphenyldiphosphinmonoxid (12.20 g, 31% yield) with a purity of 85% (m / m). 31 P NMR (toluene-D8): - 22.9 (d, U 224 Hz); 35.1 (d, U 224 Hz).

Claims

claims 1. A process for preparing diphosphine monoxides of the formula I. R ^{1 R3} \ P-P = O 'wherein R ¹ -R ^{4 are} independently selected from the group of C _T Cie-alkyl, C ₁ -C ₆ -alkenyl, C ₁ -C ₆ -alkoxy, C ₁ -C ₆ -alkyl-NR ² R ³ , C ₃ -C 10 -cycloalkyl, C ₃ - C 10 -cycloalkoxy, Cβ-do-aryl, C6-Cio-aryloxy, C6-Cio-aryl-Ci-Ci6-alkyl, Cβ-Cio-aryl-Ci-Cie-alkoxy, NR ² R ³ , COR ² , COOR ² and CONR ² R ³ comprising the step a) reaction of a compound of formula II R ¹

with an excess of the compound of formula III at temperatures in the range of 50 to 180 ⁰ C. R ³ V - OR ⁵ R ⁴ wherein R ^{5 is} selected from the group of C ₂ -C 16 -alkyl, C ₁ -C 16 -alkenyl, C ₃ -C 10 -cycloalkyl or C 6 -C 10 -aryl. b) removal of the product R ⁵ Cl, which is formed in addition to the compound of the formula I, from the mixture and c) separation of the mixture resulting from step a). 2. The method of claim 1, wherein the radicals R ¹ to R ^{4 are} all identical. 3. The method according to any one of claims 1 to 2, wherein the radicals R ¹ to R ^{4 are} phenyl groups. 4. The method according to any one of claims 1 to 3, wherein the radical R ^{5 represents} an ethyl group. 5. The method according to any one of claims 1 to 4, wherein in step a) at a temperature in the range of 1 10 to 130 ⁰ C is used. 6. The method according to any one of claims 1 to 5, wherein the separation of the Compound of formula I in step c) by filtration or centrifugation.