United States Patent (19) 11 Patent Number: 4,737,317 Wilson (45) Date of Patent: Apr. 12, 1988 54 PROCESS FOR PREPARING PHENYLDICHLOROPHOSPHINE OTHER PUBLICATIONS Kosolapoff, G. M. et al., Organic Phosphorus Com 75 Inventor: Glenn R. Wilson, Altamount, Ill. pounds, (1973), vol. 4, pp. 79-82, (Wiley-Interscience, 73 Assignee: Monsanto Company, St. Louis, Mo. Publ.). CRC Handbook of Chemistry and Physics, (1979-1980 (21) Appl. No.: 566,016 Ed.), CRC Press, Publ., pp. B-105 and C-146. (22 Filed: Dec. 27, 1983 Organic Syntheses, Coll., vol. 4, 784-785, (1963). 51) Int. Cl." ................................................ C07F 9/52 Primary Examiner-Donald B. Moyer 52 U.S. Cl. .............. 260/543 P Assistant Examiner-L. Hendriksen 58) Field of Search ..................................... 260/543 P Attorney, Agent, or Firm-Wendell W. Brooks; Arthur (56) References Cited E. Hoffman; Arnold H. Cole U.S. PATENT DOCUMENTS (57) ABSTRACT 3,029,282 4/1962 Toy et al. ............................ 260/543 Phenyldichlorophosphine is prepared by contacting 3,057,917 10/1962 Maier ......... ... 260/543 benzene with phosphorus trichloride in the vapor phase 3,210,418 10/1965 Planfetti .............................. 260/543 at a temperature from about 100° C. to about 145 C. in 3,864,394 2/1975 Via et al. ........ 260/543 P the presence of a catalyst consisting essentially of alumi 3,954,859 5/1976 Jurewicz et al. ................ 260/543 P nun metal and an activating amount of aluminum chlo ride. FOREIGN PATENT DOCUMENTS 443354 2/1969 Japan. 9 Claims, No Drawings 4,737,317 1. 2 benzene, phosphorus trichloride, and aluminum chlo PROCESS FOR PREPARING ride at reflux temperatures, and treating the resulting PHENYLDICHLOROPHOSPHINE hot reaction mixture with phosphorus oxychloride. Although these prior art processes generally provide BACKGROUND OF THE DISCLOSURE 5 the desired product, they nevertheless are limited in 1. Field of the Invention their application. Principal among these limitations, are This invention relates to a process for the preparation the drastic and severe reaction conditions which must of phenyldichlorophosphine. More particularly, this be employed which leads to the substantial production invention relates to a process for the vapor phase prepa of decomposition products. The discovery of the rela ration of phenyldichlorophosphine at temperatures 10 tively low temperature, vapor phase process of the from about 100° C. to about 145 C. in the presence of present invention is therefore believed to be a decided a catalyst consisting essentially of aluminum metal and advance in the state of the art. an activating amount of aluminum chloride. Phenyldichlorophosphine is a very useful intermedi SUMMARY OF THE INVENTION ate compound in organic synthesis. It may be used to 15 This invention is directed to a process for the vapor prepare various phosphorus-containing insecticides and phase reaction of benzene and phosphorus trichloride at to prepare the corresponding phosphonous acid, temperatures from about 100° C. to about 145 C. in the C6H6P(OH)2. Extensive quantities of phenyldichloro presence of a catalyst consisting essentially of aluminum phosphine are used each year for these purposes. metal and an activating amount of aluminum chloride. 2. Description of the Prior Art 20 Accordingly, typical objects of this invention are to Various processes for the preparation of aryldihalo provide a relatively low-temperature vapor phase pro phosphines are known in the art. The preparation of cess for the preparation of phenyldichlorophosphine aryldichlorophosphine, inter alia, is described in U.S. and to provide a vapor phase process for preparing Pat. No. 3,954,859. In this process, an aromatic hydro phenyldichlorophosphine at temperatures from about carbon selected from benzene, toluene, and xylene is 25 100 C. to about 145 C. characterized by high reactant reacted with phosphorus trichloride in the presence of a conversions and high phenyldichlorophosphine selec crystalline aluminosilicate zeolite in the hydrogen form tivity. catalyst at a temperature from 147 to 475 C. In this reaction, benzene and phosphorus trichloride yield phe These and other objects, aspects, and advantages of nyldichlorophosphine. 30 the invention, which will become apparent to those In U.S. Pat. No. 3,864,394 is described a process skilled in the art from the accompanying description wherein phenyldichlorophosphine (phenylphospho and claims are achieved by the process disclosed herein nous dichloride) is prepared by reacting chlorobenzene, for the preparation of phenyldichlorophosphine which phosphorus trichloride, and elemental phosphorus in an comprises contacting benzene with phosphorus trichlo autoclave at a temperature from about 275 C. to about 35 ride in the vapor phase at a temperature from about 100' 400 C. for a period of time from about 0.25 hour to C. to about 145 C. in the presence of a catalyst consist about 30 hours. ing essentially of aluminum metal and an activating U.S. Pat. No. 3,210,418 discloses the preparation of amount of anhydrous aluminum chloride. phenyldichlorophosphine by reacting benzene with DESCRIPTION OF THE PREFERRED phosphorus trichloride at a temperature of 725 C. in 40 the presence of a homogeneous gaseous catalyst, for EMBODIMENTS example, molecular oxygen, halogens, or nitrogen ox In accordance with this invention, phenyldichloro ides, which function as a free radical promoter. phosphine (also known as phenylphosphonous dichlo In U.S. Pat. No. 3,057,917 is described a process for ride) is prepared by a vapor phase process which com preparing, inter alia, arylhalophosphines which com 45 prises contacting benzene with phosphorus trichloride prises reacting an aryl halide, in the vapor phase, with in the vapor phase at a temperature from about 100 C. red phosphorus in the presence or absence of a metal to about 145 C. in the presence of a catalyst consisting catalyst selected from the group consisting of copper, essentially of aluminum metal and an activating amount nickel, silver, tin, antimony, and alloys of copper with at of aluminum chloride. The process is characterized by least one other metal of the group of metals. The aryl 50 high reactant conversion and high phenyldichlorophos dihalophosphine reportedly is the predominant species. phine selectivity. U.S. Pat. No. 3,029,282 describes a process for the The catalyst essential for use in the present invention preparation of phenyldichlorophosphine wherein ben consists essentially of aluminum metal and an activating Zene and phosphorus trichloride are reacted attempera amount of aluminum chloride. The aluminum metal can tures of at least 350° C. in the presence of chloroben 55 exist in any convenient form which can provide the zene. The presence of chlorobenzene reportedly in necessary surface to catalyze the desired reaction be creases the reaction rate, decreases decomposition tween the benzene and the phosphorus trichloride to products, and improves the quality of the phenyldi yield phenyldichlorophosphine. Suitable forms for the chlorophosphine. aluminum metal include aluminum wire (conveniently In Japanese Pat. No. Sho 44(1969-3354 a process for 60 shaped into a coil) and particulate aluminum metal. In the preparation of phenyldichlorophosphine is de general, aluminum wire is preferred. scribed whereinbenzene and phosphorus trichloride are The amount of aluminum metal employed in the in reacted at a temperature of 550° C. to 850 C. in the stant process is not narrowly critical. All that is neces presence of carbon tetrachloride. sary is that the aluminum metal is employed in an Finally, in an article in Organic Syntheses, Coll. Vol. 4, 65 amount sufficient to catalyze the reaction between the 784-785 (1963), there is disclosed a process for the prep benzene and phosphorus trichloride. Although larger or aration of phenyldichlorophosphine which comprises smaller amounts can be employed, if desired, an amount reacting in the liquid phase a homogeneous solution of of aluminum from about 0.10 mole to about 1.0 mole per 4,737,317 3 4 mole of phosphorus trichloride is generally sufficient, num chloride) contained in a suitable vessel. Similarly, with about 0.40 mole to about 0.70 mole being pre in a continuous operation, the vaporized reactant may ferred. be contacted in the presence of a moving or ebullient In addition to the aluminum metal, the catalyst also bed of (particulate) catalyst. includes a catalyst activating amount of aluminum chlo Following the reaction of the benzene with the phos ride. The actual amount of aluminum chloride em phorus trichloride, the reaction mixture is treated for ployed is not critical. All that is necessary is that an the recovery of, or the gas chromatographic analysis amount sufficient to activate the catalyst and initiate for, the phenyldichlorophosphine product. The reac reaction between the benzene and phosphorus trichlo tion mixture is cooled and diluted with benzene. To the ride is present. A trace amount, for example, 0.000010 to O resultant mixture is added a calculated amount of p 0.0010 gram per gram of aluminum metal, is usually dioxane (calculated from the weight loss of the alumi sufficient although, if desired, both larger and smaller nun metal catalyst) to decompose the aluminum-con amounts may be employed. taining phenyldichlorophosphine complex. The freed As previously noted, contact of the benzene with the phenyldichlorophosphine product is then analyzed by phosphorus trichloride in the presence of the catalyst is