Silicon aluminum halides

Because carbon bonds so readily with itself, there are many hydrocarbons (see Chapter 18). Silicon forms a much smaller number of compounds with hydrogen, called the silanes. The simplest silane is silane itself, SiH4, the analog of methane. Silane is formed by the action of lithium aluminum hydride on silicon halides in ether ... 

Silane is formed by the action of lithium aluminum hydride on silicon halides in ether ... 

Halides of aluminum, silicon, and phosphorus5, tin tetrachloride, titanium tetrachloride, and antimony pentachloride6 did not form complexes with diphenyl tellurium oxide, but converted it to the corresponding diphenyl tellurium dihalide. 

Zinc may be used in place of aluminum in a similar reaction. The method also may be used for the vapor-phase hydrogenation of organo-silicon halides such as methyltrichlorosilane ... 

It is proposed3 that in this vapor-phase alkylation an alkyl of zinc or aluminum first is formed and that this reacts immediately with the silicon halide ... 

The boron halides (not BF3), like the silicon halides, are readily hydrolyzed, whereas the aluminum halides are only partially hydrolyzed in water. 

The reductions of chlorosilanes by lithium aluminum hydride, lithium hydride, and other metal hydrides, MH, offers the advantages of higher yield and purity as well as flexibility in producing a range of silicon hydrides comparable to the range of silicon halides (59). The general reaction is as follows ... 

Direct Thermal Plasma Decomposition of Halides of Aluminum, Silicon, Arsenic, and Some Other Elements of Groups 3, 4, and 5... 

The following metal compounds are used for the preparation of the catalysts oxides, metal carbonyls, halides, alkyl and allyl complexes, as well as molybdenum, tungsten, and rhenium sulfides. Oxides of iridium, osmium, ruthenium, rhodium, niobium, tantalum, lanthanum, tellurium, and tin are effective promoters, although their catalytic activity is considerably lower. Oxides of aluminum, silicon, titanium, manganese, zirconium as well as silicates and phosphates of these elements are utilized as supports. Also, mixtures of oxides are used. The best supports are those of alumina oxide and silica. 

Methods of preparation for silicides and aluminides are very similar to those used for carbides, nitrides and borides (1) synthesis by fusion or sintering, (2) reduction of the metal oxide by silicon or aluminum, (3) reaction of the metal oxide with SiOj and carbon, (4) reaction of the metal with silicon halide or (5) fused salt electrolysis. The simplest preparation method consists of... 

Silica is reduced to silicon at 1300—1400°C by hydrogen, carbon, and a variety of metallic elements. Gaseous silicon monoxide is also formed. At pressures of >40 MPa (400 atm), in the presence of aluminum and aluminum halides, silica can be converted to silane in high yields by reaction with hydrogen (15). Silicon itself is not hydrogenated under these conditions. The formation of silicon by reduction of silica with carbon is important in the technical preparation of the element and its alloys and in the preparation of silicon carbide in the electric furnace. Reduction with lithium and sodium occurs at 200—250°C, with the formation of metal oxide and silicate. At 800—900°C, silica is reduced by calcium, magnesium, and aluminum. Other metals reported to reduce silica to the element include manganese, iron, niobium, uranium, lanthanum, cerium, and neodymium (16). 

Boron differs from aluminum in showing almost no metallic properties and its resemblance to silicon is greater. Both boron and silicon form volatile, very reactive hydrides the hydride of aluminum is a polymeric solid. The halides (except BF3) hydrolyze to form boric acid and silicic acid. The oxygen chemistry of the borutes and silicates also has certain resemblances. 

It is easy to reduce anhydrous rare-earth halides to the metal by reaction of more electropositive metals such as calcium, lithium, sodium, potassium, and aluminum. Electrolytic reduction is an alternative in the production of the light lanthanide metals, including didymium, a Nd—Pr mixture. The rare-earth metals have a great affinity for oxygen, sulfur, nitrogen, carbon, silicon, boron, phosphorus, and hydrogen at elevated temperature and remove these elements from most other metals. 

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