3,704,261 United States Patent Office Patented Nov. 28, 1972 2 materials and are not recovered from the reaction medium 3,704,261 since they form stable complexes with the alkali metal PREPARATION OF SELCON HYDRDES halides generated in the reaction. The formation of these Abe Berger, Schenectady, and Frederick M. Lewis, Buriat Hills, N.Y., assignors to General Electric Company complexes emits heat thereby requiring that the reaction No Drawing. Filed Oct. 18, 1971, Ser. No. 90,401. be closely monitored. In addition, it is generally neces in C, COTf I7/08 sary to employ corrosion resistant reaction vessels since U.S. C. 260-448.2 E 5 Claims corrosion causing materials are emitted in the reaction when alkyl aluminum halides are employed. The present invention provides a process for converting ABSTRACT OF THE DISCLOSURE 10 organosilicon halides to the corresponding hydrides which A method is provided for converting organosilicon is effective and safe. Moreover, the process of the present halides, for example, halosilanes and bis(halosilyl) hydro invention is economically feasible for commercial opera carbons, to the corresponding hydrides. Silicon halide re tions. Also the method of the present invention does duction is effected by utilizing certain organometallic not require extra-ordinary safety precautions. hydrides. SUMMARY OF THE INVENTION The process of the present invention comprises re BACKGROUND OF THE INVENTION acting: Prior to the present invention, various methods were (A) an effective amount of organometallic hydride known for reducing silicon halides as illustrated by the 20 having the structural formula: equation, ( 2 ) L (MeHR)y (1) (EI) RaSiX4-a - RaSiH4 wherein L is an alkali metal or an alkaline earth metal; y is the valence of L; Me is a metal from group III-A of where R is selected from monovalent hydrocarbon radicals 25 the periodic table; each R2 individually is a monovalent and halogenated monovalent hydrocarbon radicals, X is hydrocarbon radical such as alkyl, alkaryl, aryl, aralkyl, a halogen radical, and a is an integer equal to from 1 to 3, and cycloalkyl; and z is a whole number integer from 1 inclusive. One method that can be used to reduce silicon to 3, inclusive; and halides involves the use of lithium aluminum hydride in (B) organosilicon halide selected from organohalo an ether Solvent. Although this procedure can be satis 30 factorily employed for making a variety of silicon hydrides, silanes of formula: those skilled in the art know that it is not economically (3) RaH Six (4-a-b) feasible to utilize lithium aluminum hydride in com or bis(halosilyl) hydrocarbons of the formula: mercial operations. Other methods are shown by Jenkner, Pats. 3,043,857 and 3,100,778. These patents show the 35 (4) (3-c-d)XHRdSiR'SiReFX(3-e-r) reduction of halides of certain Group IV elements, for where R, X, and a are defined above; R is a divalent example, organohalosilanes, by the employment of sodium hydrocarbon radical; b is a whole number which has a hydride utilizing hydrogen gas under pressure, or a value equal to 0 to 2, inclusive; c is a whole number combination of sodium hydride and a promoter in the which has a value equal to 0 to 2, inclusive; d is a whole form of a metallic organic compound such as an alkyl 40 number which has a value equal to form 0 to 2, inclusive; aluminum. These methods achieve effective results but e is a whole number which has a value equal to 0 to 2, have many limitations. For example, the employment of inclusive; f is a whole number which has a value equal to in situ sodium hydride utilizing hydrogen gas under 0 to 2, inclusive; the sum of a and b has a value equal to pressure in combination with sodium metal, requires the 1 to 3, inclusive; the sum of c and d has a value equal use of high pressure equipment. Such equipment can be 45 to 0 to 2, inclusive; and the sum of e and f has a value expensive and present a safety hazard. Alternatively, equal to 0 to 2, inclusive. although the alkyl aluminum can be employed effectively to reduce organohalosilanes substituted with monovalent DESCRIPTION OF PREFERRED EMBODIMENTS hydrocarbon radicals, the use of alkyl aluminums often The present invention provides a method for preparing present problems of contamination. For example, in 50 organosilicon hydrides selected from silanes of the form instances where the boiling points of the resulting silicon ula: hydride and alkyl aluminum overlap, separation of the silicon hydride free of alkyl aluminum often can be ex (5) RaSiH4 a tremely difficult. In addition, when alkyl aluminums are and bis(silyl) hydrocarbons of the formula: employed to promote the reduction of organohalosilane, 55 reaction times can often exceed 24 hours or more and (6) (8-d)HRdSiR'SiRH(3-e) yields of the corresponding silicon hydride are low. where R, R., a, d, and e are as defined above. A recent method for reducing silicon halides wherein Radicals included by R of Formula 1 are, for example, an alkali metal hydride and an alkyl aluminum halide aryl radicals and halogenated aryl radicals, such as phenyl, are employed to reduce the silicon halides is described 60 chlorophenyl, napthyl, chloronapthyl, etc.; aliphatic in U.S. Pat. 3,496,206. Although the process described radicals such as for example, methyl, ethyl, n-propyl, iso in U.S. Pat. 3,496,206 overcomes many of the problems propyl, n-butyl, sec-butyl, tert-butyl, amyl, hexyl, hepty, previously encountered when converting organosilicon octyl, dodecyl, pentadecyl, octadecyl; alkenyl radicals such halides to the corresponding hydrides, it has a few as vinyl, 1-propenyl, allyl etc.; cycloalkyl radicals such as limitations. For example, alkyl aluminum halides must 65 cyclohexyl, cycloheptyl, etc.; haloalkyl radicals such as be carefully handled since they are unstable and ignite chlorobutyl, chloroamyl, chlorooctyl, chlorodecyl, etc. on exposure to oxygen or water. Also, the alkyl aluminum Radicals included by R are arylene radicals such as phen halides when contacted with the skin cause severe blister ylene, naphthylene, anthrylene, etc.; alkylene radicals such ing. Moreover, such halides are difficult to handle since as methylene, ethylene, propylene, butylene, pentylene, they are quite volatile. In addition, the use of the alkyl 70 etc. aluminum halides in such reactions is quite expensive. Organohalosilanes included by Formula 3 are, for ex The alkyl aluminum halides are relatively expensive raw ample, methyltrichlorosilane, methylphenyldichlorosilane, 3,704,261 3 4. methyldichlorosilane, ethyltrichlorosilane, ethylchlorosil hydride; sodium ethyl aluminum trihydride; sodium tri ane, n-propyltrichlorosilane, n-butyltrichlorosilane, n ethyl aluminum hydride; sodium dimethyl aluminum di amyltrichlorosilane, n-amyldichlorosilane, n-amylchloro hydride; sodium methyl ethyl aluminum dihydride; sodi silane, n-hexyltrichlorosilane, n-hexyldichlorosilane, n um triethyl aluminum hydride; sodium trimethyl alumi hexylchlorosilane, phenyltrichlorosilane, chlorophenyltri num hydride; sodium methyl aluminum trihydride, sodi chlorosilane, isopropyldichlorosilane, diphenyldichlorosil um dimethyl boron dihydride, sodium diphenyl aluminum ane, diphenylchlorosilane, n-propyl n-octyldichlorosilane, dihydride, sodium diphenyl boron dihydride, sodium di tri-n-propylchlorosilane, etc. cyclobutyl aluminum dihydride, sodium dicyclohexyl alu Bis(halosilyl) hydrocarbons included by Formula 4 are minum dihydride, sodium ethyl phenyl aluminum dihy for example, bis(chlorodimethylsilyl)methane, bis(trichlo O dride, lithium diethyl aluminum dihydride, lithium di rosilyl)methane, 1,2-bis(trichlorosilyl)ethane, 1,2-bis(di methyl aluminum dihydride, lithium diethyl boron dihy chlorosilyl)ethane, 1,3-bis(trichlorosilyl)propane, 1,4-bis dride, lithium dimethyl boron dihydride, potassium di (methyldibromosilyl)butane, 1,8-bis(dichlorosilyl)octane, ethyl aluminum dihydride, potassium dimethyl aluminum p-bis(dichlorosilyl)benzene, etc. dihydride, calcium-bis-(diethyl aluminum dihydride), and The organometallic hydrides suitable in the present in 5 magnesium-bis(diethyl aluminum dihydride). It is of vention have the following structural formula: course, understood that mixtures of such compounds can be employed in the process of the present invention. (2) L(MeH,R), Methods for preparing the aforementioned organometallic hydrides can be found in E. L. Ashby et al., Inorganic wherein L is an alkali metal or an alkaline earth metal; y 20 Chemistry, volume No. 2, page 499, 1963. is the valence of L; Me is a metal from Group II-A of The reaction between the organosilicon halides and the periodic table; each Rindividually is an alkyl radical the organometallic hydrides can achieve yields as high and/or aryl radical and/or cycloalkyl radical and/or ar as 95% in reaction times as little as a hour or less alkyl and/or alkaryl; and z is a whole number integer under atmospheric conditions. For complete conversion from 1 to 3, inclusive. Some alkali metals and alkaline earth metals which are 25 of the silicon halide to the corresponding silicon hydride, suitable constiutents of the organometallic hydrides of it is preferred that the organometallic hydride be em Formula 2 above include sodium, potassium, lithium, ployed in an amount so as to provide at least about one rubidium, cesium, magnesium, calcium, strontium, and mole of chemically combined hydrogen per mole of barium. Preferably sodium is employed as the alkali metal halogen chemically bonded to silicon metal. The present or alkaline earth metal substituents of the organometallic 30 reaction is quite useful since the organosilicon hydrides hydrides of Formula 2. can be recovered from the reaction medium free from Some metals of Group III-A of the periodic table contamination due to the organometallic hydride by which are suitable components of the organometallic hy vaporization and subsequent condensation. An organo drides employed in the present invention include boron, metallic halide corresponding to the organometallic hy aluminum, gallium, and indium. The preferred Group 35 dride reactant is formed in the reaction.