Tetrachlorosilane

SiCl4 is a clear, colourless liquid which fumes in open air. Its boiling point is 57.6 °C. It can be produced by chlorination of a mixture of coke with silicon dioxide or silicon carbide, or both. There is a patented process [39] for reacting SiOj, SiC and coke with chlorine in a fluid bed reactor. The gaseous reaction product runs through a separator to remove solid impurities. Thereafter it is condensed and distilled. 

Trichlorosilane HSiClj is produced from the reaction of elemental silicon with hydrochloric acid (Eq. 2.1)  

The presence of iron promotes this reaction. For example, dry hydrochloric acid was passed at 290-310°C over ferrosilicon (90% silicon) to produce trichlorosilane in 77% yield [40]. Trichlorosilane can also be produced at 400 °C from a mixture of tetrachlorosilane, hydrogen and elemental silicon [41]. (Eq. 2.2)  

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Only three inorganic halosilanes are produced on a large iadustrial scale, ie, tetrachlorosilane [10026-04-7] tetrafluorosilane [7783-61-17, and trichlorosilane. 

Oxidation. Sihcon haUdes are stable to oxygen at room temperature, but react at elevated temperatures to form, ia the case of chlorides, oxychlorosilanes. Tetrachlorosilane reacts at 950—970°C to form hexachlorodisiloxane (160,161). 

Protic Materials. The hydrolytic behavior of tetrachlorosilane was described by Mendeleyev (164), and is summarized herein. Orthosihcic acid formed by the action of water on tetrachlorosilane ... 

The heat of reaction of tetrachlorosilane with an excess of water is 290.0 kJ /mol (69.3 kcal/mol). The reaction of tetraduorosilane with excess water contrasts with the other halosilanes, because it leads to formation of hexaduorosiUcic acid and a hydrous siUca. 

Reduction/Reaction with Hydrogen. Tetraduorosilane reacts with hydrogen only above 2000°C. Tetrachlorosilane can be reduced by hydrogen at 1200°C. Tetraio do silane can be reduced to sihcon at 1000°C (165). Reduction of tetraduorosilane with potassium metal to sihcon was the first method used to prepare sihcon (see Silicon and silicon alloys). The reduction of sihcon tetrachloride by ziac metal led to the first semiconductor-grade sihcon (166,167). 

Sodium and magnesium do not react with tetrachlorosilane at room temperature, but do so at elevated temperatures and ia the presence of polar aprotic solvents at moderately elevated temperatures. The Wurtz-Fittig coupling of organosilanes to form disilanes (168) and polysdanes (169) is usually accomphshed usiag molten sodium ia toluene or xylene. 

Manufacturing. Tetrachlorosilane can be manufactured directly by the reaction of chlorine on sihcon metal or ferrosiUcon at 500°C or sihcon carbide (170). 

The production of sihcon tetrachloride by these methods was abandoned worldwide in the early 1980s. Industrial tetrachlorosilane derives from two processes associated with trichlorosilane, the direct reaction of hydrogen chloride on sihcon primarily produced as an intermediate for fumed sihca production, and as a by-product in the disproportionation reaction of trichlorosilane to silane utilized in microelectronics. Substantial quantities of tetrachlorosilane are produced as a by-product in the production of zirconium tetrachloride, but this source has decreased in the 1990s owing to reduction in demand for zirconium in nuclear facihties (see Nuclearreactors). The price of tetrachlorosilane varies between l/kg and 25/kg, depending on grade and container. 

Many chlorine compounds, including methyl chlorosilanes, such as ClSi(CH2)3, Cl2Si(CH3)2, Cl3Si(CH3) tetrachlorosilane [10026-04-7] SiCl chlorine, CI2 and carbon tetrachloride, CCl, can completely react with molecular surface hydroxyl groups to form hydrochloric acid (40), which then desorbs from the gel body in a temperature range of 400—800°C, where the pores are still interconnected. Carbon tetrachloride can yield complete dehydration of ultrapure gel—siUca optical components (3,23). 

Preparation, Properties and Reactions of Tetra(alkoxy)-, Tetra(acetoxy)-, Tetra(dialkylamino)-, and Tetrachlorosilanes... 

When there is no diluent, organic acid chlorides and metal halides react very violently with DMSO. This goes for acetyl chloride, benzenesulphonyl (C6H5SO2CI), cyanuryl chloride, phosphorus and phosphoryl trichlorides, tetrachlorosilane, sulphur, thionyl, and sulphuryl chlorides. With oxalyl chloride, the reaction is explosive at ambient temperature, but can be controlled at -60°C in a solution with dichloromethane. The dangerous reactions are thought to be... 

Tetrachlorosilane was added to aqueous ethanol (the presence of water was accidental). There was no proper stirring during this operation, which led to the formation of two liquid layers of compounds that did not react. The very fast and exothermic reaction of the alcoholysis-hydrolysis of chlorosilane started violently and the large compoundion of hydrogen chloride caused the reactor to detonate. 

With tetrachlorosilane, sodium metal gives rise to mixtures that are explosive on impact. This situation is exactly similar to the one with tetrachloromethane. 

Tetrachlorosilane, or Tetrabromosilane, or Titanium tetrachloride, and Diethyl ether Schmeisser, M., Angew. Chem., 1955, 67, 499... 

In absence of diluent or other effective control of reaction rate, the sulfoxide reacts violently or explosively with the following acetyl chloride, benzenesul-fonyl chloride, cyanuric chloride, phosphorus trichloride, phosphoryl chloride, tetrachlorosilane, sulfur dichloride, disulfur dichloride, sulfuryl chloride or thionyl chloride [1], These violent reactions are explained in terms of exothermic polymerisation of formaldehyde produced under a variety of conditions by interaction of the sulfoxide with reactive halides, acidic or basic reagents [2], Oxalyl chloride reacts explosively with DMSO at ambient temperature, but controllably in dichloromethane at -60°C [3]. 

The solid residue of the preparation from lithium powder, trimethylsilyl chloride, tetrachlorosilane and methyllithium may be highly pyrophoric. Caution in quenching into dilute acid is advised. 

The transmetalation of trimethylsilylphosphanes with germanium and tin halides is a useful way to prepare compounds with P—Ge and P—Sn bonds by simple chlorosilane elimination. The reverse reaction, i. e. formation of P—Si bonds by chlorosilane cleavage of germyl- and stannylphosphanes has not yet been reported. Recently, we observed that hexachlorodisilane "transsilylates di-r-butyl(trimethyl-silyl)phosphane 1 much faster than tetrachlorosilane to give trichlorosilylphosphane 2 ... 

Treatment of urazole 381 with ethyl isocyanatoformate gives a quantitative yield of ethyl ester 382 and its cyclization at 160 °C affords 383 in only 35% yield but a yield of 85% is obtained only if the ethanol formed is trapped with tetrachlorosilane (Scheme 58) <1999M327>. 

Tetracarbon monofluoride, 1362 Tetrachlorodiphosphane, 4171 Tetrachlorosilane, 4173 Tetraiododiphosphane, 4637 Thiazyl fluoride, 4306... 

Silica gel is a three-dimensional polymer of silicic acid, usually synthesized from tetrachlorosilane or sodium silicic acid. The reaction is as follows ... 

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