|||||||||||||||||US005354918A United States Patent 19 11) Patent Number: 5,354,918 Ohsaki et al. 45) Date of Patent: Oct. 11, 1994 (54 HIGHLY PURE MONOALKYLPHOSPHINE OTHER PUBLICATIONS (75) Inventors: Hiromi Ohsaki; Kazuyuki Asakura, Hoff et al., Journal of Organic Chemistry, (24) pp. both of Joetsu: Masashi Sugiya, 356-359, 1959. Tokyo; Yutaka Demura; Tomio Chemical Abstracts, vol. 117, 1992, Columbus, Ohio, Yanai, both of Kohriyama, all of US; abstract No. 171693s, & JP-A-04 149 187 (Nippon Japan Mining Co., Ltd.). Primary Examiner-Johann Richter 73) Assignees: Shin-Etsu Chemical Co., Ltd.; Nippon Assistant Examiner-Margaret J. Page Chemical Industrial Co., Ltd., both of Japan Attorney, Agent, or Firm-Parkhurst, Wendel & Rossi 57 ABSTRACT (21) Appl. No.: 91,363 The method for preparing a monoalkylphosphine of high purity comprises reacting phosphine and an alkene (22 Filed: Jul. 15, 1993 in the presence of an anhydrous alkanesulfonic acid as a catalyst in a solvent having a boiling point higher than that of the monoalkylphosphine produced. The result 30 Foreign Application Priority Data ing monoalkylphosphine is brought into contact with an Jul. 17, 1992 JP Japan .................................. 4-1904.87 alkali solution to remove the catalyst, which is a sulfur Nov. 9, 1992 JP Japan .... ... 4-298629 atom-containing compound, remaining in the solution. Mar. 12, 1993 JP Japan .................................... 5-51806 The reaction solution from which the remaining cata Mar. 22, 1993 JP Japan .................................... 5-61775 lyst is removed is then brought into contact with alkali metal hydrides or alkaline earth metal hydrides to elimi 51) Int. Cl. ................................................ C07F 9/50 nate any moisture remaining in the reaction solution. 52 U.S. Cl. ............... The alkali metal hydride is preferably sodium hydride 58 Field of Search ............................................ 568/8 or lithium aluminum hydride, while the alkaline earth metal hydride is preferably calcium hydride. The result (56) References Cited ing monoalkylphosphine is isolated through distillation and the compound in a gaseous or liquid state is brought U.S. PATENT DOCUMENTS into contact with and passed through a layer of active 2,584,112 2/1952 Brown . carbon to remove other impurities present therein. 4,922,025 5/1990 Hoelderich et al................... 568/4 5,041,676 8/1991 Hofmann ................................ 568/8 9 Claims, No Drawings 5,354,918 1. 2 HIGHLY PURE MONOALKYLPHOSPHINE SUMMARY OF THE INVENTION The present invention has been completed for elimi BACKGROUND OF THE INVENTION nating the foregoing drawbacks associated with the The present invention relates to a highly pure mo conventional techniques and accordingly, an object of noalkylphosphine and a method for preparing the same. the present invention is to provide an industrially effec The highly pure monoalkylphosphine is useful as a tive method for efficiently and safely preparing, in high material for use in the epitaxial growth of compound production efficiency, a monoalkylphosphine useful as a semiconductors. starting material for epitaxial crystal-growth, which has Recently, compound semiconductors have widely 10 a high purity level commonly required for the starting material used in the production of a compound semicon been used in various fields such as light emitting diodes, ductor. semiconductor lasers and high electron mobility transis The inventors of this invention have conducted vari tors (HEMT). As a method for preparing a compound ous studies on the basis of the foregoing facts and, as a semiconductor, there has widely been used an epitaxial 15 result, have found out a method for preparing a mo crystal-growth technique such as a Metalorganic noalkylphosphine of high purity in a high yield. Thus, Chemical Vapor Deposition (MOCVD) method. Com the inventors of this invention have completed the pres pound semiconductors prepared by such an epitaxial ent invention. crystal-growth technique include, for instance, Group The method for preparing a monoalkylphosphine of III-V compound semiconductors in which phosphine 20 high purity according to the present invention com containing a phosphorus atom is often used as a source prises reacting phosphine and an alkene in the presence for phosphorus atom, a Group V element. of a catalyst comprising at least one member selected Phosphines are highly toxic and suffer from a prob from the group consisting of anhydrous alkanesulfonic lem of safety. Recently, there has been proposed the use acids represented by the following general formula (I): of monoalkylphosphorous atom-containing compounds 25 as sources of phosphorus atom, one of group V ele R-SO2H (I) ments, and they have attracted special interest recently as a substitute for phosphine since the use thereof per (wherein R represents an alkyl group having 1 to 4 mits the formation of epitaxial growth films having a carbon atoms) in an organic solvent having a boiling low carbon content as an impurity and they are less 30 point higher than that of the monoalkylphosphine pro toxic than phosphine. duced. As methods for preparing monoalkylphosphines, In particular, the reaction solution obtained through there have been known, for instance, those comprising the foregoing reaction is preferably brought into reducing phosphonium chloride or phosphorous acid contact with an alkali solution for the removal of the (see, for instance, Z. anorg. allg. Chem., 1978, 443, p. 35 catalyst remaining therein. It is further preferred that, 42). However, these methods never permit the prepara after contacting the reaction solution with the alkali tion of a highly pure monoalkylphosphines since they solution, the reaction solution is brought into contact employ metallic catalysts in the reduction and suffer with a hydride of alkali metal and/or a hydride of alka from a problem of contamination with metal impurities. line earth metal since this ensures the removal of the Moreover, they include a production process requiring remaining water in the reaction solution. The resulting a long time period which results in a decrease of the monoalkylphosphine in a gaseous state or in the form of a solution is preferably brought into contact with and yield of a desired product and makes the practice passed through an active carbon layer to thus remove thereof in an industrial scale unfavorable. In addition, J. other coexisting impurities present therein. Org. Chem., 1959, 24, p. 356 discloses another method 45 for preparing a monoalkylphosphine, which comprises DESCRIPTION OF THE PREFERRED reacting phosphine with an olefin. This method makes EMBODIMENTS the mass production of monoalklphosphines substan Phosphine used as a starting material in the method tially easier. However, this method includes a reaction for preparing a highly pure monoalkylphosphine ac in an aqueous system since it requires the use of an 50 cording to the present invention may be those obtained aqueous solution of an alkanesulfonic acid as a catalyst by any method, but preferably used are highly pure and accordingly, the method is liable to cause the for products each having a very low content of metallic mation of secondary and tertiary phosphine compounds and/or oxidative impurities. as by-products whose removal is quite difficult and Alkenes used as another starting material are linear or which inevitably lead to a decrease in the yield of the 55 branched unsaturated aliphatic hydrocarbons prefera desired product. bly having 2 to 16 carbon atoms. Specific examples Moreover, if impurities originated from the catalyst thereof include isobutene, 2-methyl-1-butene, 2-ethyl-1- used are present in the resulting alkylphosphine, the butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 2,3,3- compound semiconductor formed from a crystal pre trimethyl-1-butene, 2,3-dimethyl-1-hexene, 2-ethyl-1- pared through the epitaxial growth of the phosphine hexene, isooctene, 2-methyl-1-heptene, 2,2,4-trimethyl does not exhibit desired electrical and optical properties 1-pentene, 2,4-dimethyl-1-hexene, 2,2,4-trimethyl-1- at all. For this reason, an alkylphosphine for use in the hexene, 2-methyl-1-nonene, triisobutylene and tet production of a compound semiconductor is in general raisobutylene. purified by high precision distillation. However, such One of the features of the present invention is to use high precision distillation in itself has not yet permitted 65 a reaction solvent selected from those each having a the preparation of any monoalkylphosphine having a boiling point higher than that of the resulting monoalk purity required for the production of a compound semi ylphosphine. This is because the difference between the conductor. boiling points of the monoalkylphosphine and the sol 5,354,918 3 4. vent used permits the recovery of the monoalkylphos obtained can be further enhanced if it is treated in the phine of high purity through distillation of the reaction following manner. solution or optional precision distillation performed An alkali solution is added to the organic phase to after the completion of the reaction. Such reaction sol remove the sulfur atom-containing compound used as vents are preferably saturated aliphatic hydrocarbons, the catalyst. As the alkali solution, there may be used, in particular those having 8 to 18 carbon atoms. Specific for instance, an aqueous solution of an alkali compound examples thereof are n-octane, isooctane, n-nonane, selected from the group consisting of hydroxides of