DE1198820B - Process for the production of tertiary phosphines - Google Patents

Description

Process for the production of tertiary phosphines. R ') (R ") P = 0 in which R, R' and R" are identical or different alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl or alkaryl radicals, where R and R 'together with the phosphorus atom is the phospholine ring of the general formula can form with an organic silicon compound which contains one or more Si-H bonds at elevated temperature. In this implementation, the otherwise difficult to reducible PP = 0 bond is reduced.

The present invention relates to a further embodiment this process for the production of tertiary phosphines and is characterized by that the reduction is carried out with a silicon tetrahalide instead of with the organic silicon compound and an alkaline earth metal, metallic zinc or aluminum, or with a silicon tetrahalide and performing hydrogen in the presence of a known hydrogenation catalyst.

As according to the main patent application, trialkyl, Tricycloalkyl, trialkenyl, tricycloalkenyl, triaryl, trialkaryl and triaralkylphosphine oxides be reduced. Depending on the reducing agent used, phospholine oxides the double bond hydrogenates or triarylphosphine oxides to tricycloalkylphosphines be reduced. The invention is particularly important for reduction of triarylphosphine oxides, e.g. B. triphenylphosphine oxide.

The silicon tetrahalide used is preferably silicon tetrachloride. The amount of silicon tetrahalide can vary within wide limits but generally between 1 and 2, preferably between 1/4 and 3/4 moles Silicon tetrahalide per mole of phosphine oxide used.

The phosphine oxides probably form with the silicon tetrahalide intermediate complexes. So was z. B. from triphenylphosphine oxide and silicon tetrachloride the complex 2 (C6H5) P0 l / SiCl4 isolated, which deals with the above Remedies to convert further to triphenylphosphine.

The method according to the invention can thus be carried out in two hours, by first preparing a complex of phosphine oxide, which in the second stage with the alkaline earth metal, metallic zinc or aluminum or with hydrogen in Is reduced in the presence of a known hydrogenation catalyst. However, will the one-step process is preferred.

In addition to alkaline earth metals, such as calcium or magnesium, or aluminum Zinc, hydrogen also comes in the presence of a known hydrogenation catalyst, such as palladium on animal charcoal, synthesis gas in the presence of homogeneous catalysts, z. B. dicobalt octacarbonyl, in question. Magnesium and zinc are preferred, in particular metallic aluminum.

It is expedient to work under a hydrogen atmosphere z. B. 0 to 200 atm. If desired, the reaction can also be carried out under nitrogen, Use argon or other inert gases.

The conversion of the phosphine oxides is expediently at increased Temperatures made, generally between 70 and 250'C. One reaction time from 1 to 5 hours is generally sufficient. The implementation can be done with a inert as well as without solvents. Suitable inert solvents are z. B.

Naphthalene, benzene, toluene, glycol diethyl ether, diethylene glycol dimethyl ether and diphenyl ether.

The reaction is expediently carried out in the liquid phase.

For this purpose, overpressure is generally required to create one or more Respondents, such as B. the silicon tetrachloride in the reaction mixture keep. So you will mostly work in the autoclave at pressures of 20 to z. B. 200 atm or more.

Apparatus and / or linings are expediently used here made of corrosion-resistant material such as glass, enamel or stainless steel. Of course other embodiments are also possible.

So one can use the phosphine oxide and the silicon tetrahalide - if desired together with hydrogen - under pressure through a pipe filled with aluminum grit send.

The phosphines which can be prepared according to the invention, in particular the triphenyl and tricyclohexylphosphine, are intermediates for vitamin A production according to Wittig's carbonyl olefination (cf.

Angew. Chemie, 72, 811 (1960)).

Example 1 55.6 g triphenylphosphine oxide (0.2 mol), 34 g SiCl4 (0.2 Mol) and 10 g of aluminum powder were placed in an autoclave. At room temperature 130 at H2 were injected and heated to 250 ° C. for 5 hours with stirring. The contents of the autoclave was introduced into 300 / o NaOH, filtered off from the precipitate and recrystallized from ethanol. Yield: 22 g triphenylphosphine, corresponds to 420 / or theory. 78 ° C.

Example 2 55 g triphenylphosphine oxide (0.2 mol) and 68 g SiCl4 (0.4 Mol) and 5 g of aluminum powder were treated as above. Yield 21 g triphenylphosphine, corresponds to 400 / o of the theory. F. 790C.

Example 3 27.8 g triphenylphosphine oxide, 17 g silicon tetrachloride and 2.5 g of aluminum powder were heated to 150 ° C. under 100 atm. hydrogen for 4 hours. The reaction product was introduced into 300 / o NaOH and the insoluble residue recrystallized from ethanol. Yield: 15.2 g of triphenylphosphine, corresponds to 58% the theory. F. 80 "C Example 4 27.8 g triphenylphosphine oxide, 17 g silicon tetrachloride and 2.5 g of zinc dust were heated for 4 hours at 100 at H2 and to 250 "C. It was worked up as above. Yield: 12.8 g triphenylphosphine, corresponds to 490 / o der Theory. F. 80 "C Example 5 27.8 g triphenylphosphine oxide, 17 g SiCl4 and 3 g aluminum dust were heated to 150 ° C. for 8 hours at 100 at H2. Work-up was carried out as above.

Yield: 17.1 g tripbenylphosphine, corresponds to 65.30 / o of theory. F. 80 "C.

Example 6 27.8 g of triphenylphosphine oxide were dissolved in 100 ml of benzene. 10 g of silicon tetrachloride were added dropwise to this. After a while a complex fell of the composition 2 (C6Hs) 3P = O 1 SiCl4. This complex was recrystallized from hot benzene.

Analysis: C36H30Cl4O2P2Si M = 726 Calculated ... C 59.55, H 4.1, Cl 19.54; Found ... C 60.8, H 3.9, Cl 18.7.

18.5 g of this complex were treated with 0.8 g of aluminum powder for 4 hours heated to 200 "C at 50 at N2.

The reaction product was recrystallized from ethanol to give 4.8 g triphenylphosphine, corresponds to 37% of theory. F. 80 "C. The residue passed from 6.1 g triphenylphosphine oxide, corresponds to 430 / o of theory.

Example 7 27.8 g triphenylphosphine oxide, 17 g silicon tetrachloride and 1 g of palladium animal charcoal were heated to 200 ° C. under 150 atm. hydrogen for 5 hours. The reaction product was introduced into 300 / o NaOH, filtered off and washed with water and recrystallized from ethanol. Yield of triphenylphosphine 2.7 g, corresponds 100 / o of theory. F. 80 "C.

Example 8 7 g of triphenylphosphine oxide and 2.2 g of silicon tetrachloride were mixed with 0.2 g of a benzene solution of Co2 (CO) 8. The reaction mixture was heated to 200 "C at 100 at CO and H2 1) for 5 hours and then in 300 / o NaOH entered. The crystals which precipitated out were recrystallized from ethanol. Yield 2 g triphenylphosphine, corresponds to 300/0 of theory. F. 78 "C.

Claims (7)

Claims: 1. Further development of the process according to patent application S 80694 IVb / l2o for the production of tertiary phosphines by reducing phosphine oxides of the general formula R (R ') (R ") P = O in which formula R, R' and R" are the same or various alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl or alkaryl radicals, where R and R 'together with the phosphorus atom represent the phospholine ring of the general formula can form with an organic silicon compound which contains one or more Si-H bonds at elevated temperature, characterized in that the reduction is carried out with a silicon tetrahalide and an alkaline earth metal, metallic zinc or aluminum or with a silicon tetrahalide instead of the organic silicon compound and carrying out hydrogen in the presence of a known hydrogenation catalyst. 2. The method according to claim 1, characterized in that the Implementation with silicon tetrachloride as silicon tetrahalide. 3. The method according to claim 1 and 2, characterized in that one the reaction using 1/4 to 2 moles of silicon tetrahalide per mole of phosphine oxide performs. 4. The method according to claim 1 to 3, characterized in that one in a first stage first a complex compound of phosphine oxide and silicon tetrahalide produces which in a second stage with one of those defined in claim 1 reducing agent is implemented. 5. The method according to claim 1 to 4, characterized in that the Reaction is carried out under pressure in the liquid phase. 6. The method according to claim 1 to 5, characterized in that the Implementation is carried out at a pressure between 20 and 200 atmospheres. 7. The method according to claim 1 to 6, characterized in that the Implementation is carried out at a temperature between 70 and 250 "C. ~~~~~~~ In Publications considered: Journal of Inorganic and General Chemistry, 299, 1959, pp. 58 to 68; Chemical Reports, 91, 1958, pp. 1583 to 1588, and 92, 1959, p. 2091.