Trichlorosilanes reactions

The next step is the hydrogen reduction of the trichlorosilane (Reaction 2 above). The end product is a poly crystalline silicon rod up to 200 mm in diameter and several meters in length. The resulting EGS material is extremely pure with less than 2 ppm of carbon and only a few ppb of boron and residual donors. The Czochralski pulling technique is used to prepare large single crystals of silicon, which are subsequently sliced into wafers for use in electronic devices.1 1... 

The silanization reaction has been used for some time to alter the wetting characteristics of glass, metal oxides, and metals [44]. While it is known that trichlorosilanes polymerize in solution, only very recent work has elucidated the mechanism for surface reaction. A novel FTIR approach allowed Tripp and Hair to prove that octadecyl trichlorosilane (OTS) does not react with dry silica. 

The formation of silicon carbide, SiC (carborundum), is prevented by the addition of a little iron as much of the silicon is added to steel to increase its resistance to attack by acids, the presence of a trace of iron does not matter. (Addition of silicon to bronze is found to increase both the strength and the hardness of the bronze.) Silicon is also manufactured by the reaction between silicon tetrachloride and zinc at 1300 K and by the reduction of trichlorosilane with hydrogen. 

The reaction of hydrosilanes with butadiene is different from other reactions. Different products are obtained depending on the structurelof the hydrosilanes and the reaction conditions. Trimethylsiiane and other trialkylsilanes react to give the I 2 adduct, namely the l-trialkylsilyl-2,6-octadiene 74, in high yields[67-69]. Unlike other telomers which have the 2,7-octadienyl chain, the 2,6-octadienyl chain is formed by hydrosilylation. On the other hand, the 1 I adduct 75 (l-trichlorosilyl-2-butene)is formed selectively with trichlorosilane, which is more reactive than trialkylsilanes[69]. The Reaction gives the Z form stereoselectively[70]. A mixture of the I 1 and I 2 adducts (83.5 and 5.2%) is... 

UsuaHy, trichlorosilane, trialkoxysilane, methyl dichlorosHane, and methyl dialkoxysHane are used. For example, the reaction of trichlorosilane with aHyl methacrylate is as foHows ... 

At equihbrium the vapors are predominantly hydrogen and sihcon tetrachlorides. However, these can be easily removed from the trichlorosilane and recycled. A once-common commercial manufacturing procedure for sihcon tetrachloride was the reaction of chlorine gas with sihcon carbide. 

Trichlorosilane. The primary production process for trichlorosilane is the direct reaction of hydrogen chloride gas and sihcon metal in a fluid-bed reactor. Although this process produces both trichlorosilane and sihcon tetrachloride, production of the latter can be minimi2ed by proper control of the reaction temperature (22). A significant amount of trichlorosilane is also produced by thermal rearrangement of sihcon tetrachloride in the presence of hydrogen gas and sihcon. 

Dkect synthesis is the preparative method that ultimately accounts for most of the commercial siUcon hydride production. This is the synthesis of halosilanes by the dkect reaction of a halogen or haUde with siUcon metal, siUcon dioxide, siUcon carbide, or metal sihcide without an intervening chemical step or reagent. Trichlorosilane is produced by the reaction of hydrogen chloride and siUcon, ferrosiUcon, or calcium sihcide with or without a copper catalyst (82,83). Standard purity is produced in a static bed at 400—900°C. 

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. 

Notes. This method can be made fully reproducible by using a pre-activated catalyst. For a 100mmol scale reaction, the above catalyst solution (several drops) was mixed with the alk-l-yne (several mmol) and trichlorosilane (several mmol), and the total heated under reflux for ca. 1 h. After cooling,... 

Silicon Epitaxy. Silicon epitaxial films have superior properties. The applications are, however, limited by the high temperature of deposition, which is generally above 1000°C. These reactions use chlorinated compounds of silicon (tetrachloride, trichlorosilane, or dichlorosilane) as precursors as follows ... 

Most SiC deposition systems involve the Si-C-H-Cl chemical combination. Avery commonly used reaction is the decomposition of methyl trichlorosilane (MTS) P CP" ]... 

Beta SiC powder from the decomposition of methyl-trichlorosilane (MTS) in the presence of hydrogen in an argon plasma. Also from the gaseous thermal decomposition of tetramethylsilane, Si(CH3)4, in a flowthrough reactor between 850 and 1500°CP 1 and by the reaction of acetylene and silane. 

The reinforcing fibers are usually CVD SiC or modified aluminum oxide. A common matrix material is SiC deposited by chemical-vapor infiltration (CVI) (see Ch. 5). The CVD reaction is based on the decomposition of methyl-trichlorosilane at 1200°C. Densities approaching 90% are reported.b l Another common matrix material is Si3N4 which is deposited by isothermal CVI using the reaction of ammonia and silicon tetrachloride in hydrogen at 1100-1300°C and a total pressure of 5 torr.l" " ] The energy of fracture of such a composite is considerably higher than that of unreinforced hot-pressed silicon nitride. 

FIGURE 4.4 The production of polycrystalline silicon for the eleetronics industry involves several ehemieal steps aimed at the reduetion of impurities. These inelude (1) reaction of metallurgical grade silicon to produce a mixture of chlorosilanes, (2) distillation of trichlorosilane, and (3) reduction of trichlorosilane to polycrystalline silicon. Excerpted by special permission from Chemical Engineering, June 10, 1985. Copyright 1985 by McGraw-Hill, Inc., New York, NY 10020. 

More recently, P-cored derivative (116) was prepared from a straightforward combination of a Heck coupling, to afford an intermediate functionalised stil-bene phosphine oxide (114),a Horner-Wittig reaction yielding the phosphine oxide (115), and finally trichlorosilane reduction (Scheme 31) [89]. Using similar strategies, both the valence isoelectronic N- (117) and C- (118) cored dendrimers have been prepared (Scheme 31). 

To prepare multifunctionalized symmetric organosilicon compounds by the polyalkylation of benzene. (2-chloroethyi)trichlorosilane and (3-chloropropyl)tri-chlorosilane were reacted with benzene. Polyalkylations of benzene with (2-chloroethyl)silane and (3-chloropropyl)silane were carried out in the presence of aluminum chloride catalyst at a reaction temperature of 80 C. The reaction of benzene with excess (2-chloroethyI )trichlorosilanes afforded pcralkylated product, hexakis(2-(trichlorosilyl)ethyl)benzene in good yield (70%). ... 

The reaction of benzene with excess (3-chloropropyl)trichlorosilane afforded peralkylated product, hexakis(3-(trichlorosilyl)propyl)benzene. in moderate yield... 

In extension of the alkylation reactions to polychlorobenzenes, polychlorinated benzenes such as 1,2,4-trichlorobenzene and 1,2,., 4-tetrachlorobenzene were alkylated with (l,2-dichloroethyl)trichlorosilanes in the presence of aluminum chloride catalyst. Although the electron-withdrawing chlorine substituents on the ring deactivated the electrophilic substitution reaction, the alkylation... 

The transfer of alkylsilane monolayers onto mica was explored by Knobler and coworkers [331]. Monolayers of octadecyltrichlorosilane (OTS) were spread at the water-air interface. The trichlorosilane head groups rapidly undergo hydrolysis and cross-linking reactions to produce two-dimensional polysiloxanes on acidic subphases. On less acidic subphases, the polymerization rate is slower and the monolayer can be spread and transferred before the polymerization is significant. The II-A isotherm for OTS spread on... 

Concerning enantioselective processes, Fujihara and Tamura have proved that palladium NPs containing (S)-BINAP (2,2 -bis(diphenylphosphino)-l,l -binaphthyl) as chiral stabiliser, catalyse the hydrosilylation of styrene with trichlorosilane, obtaining (S)-l-phenylethanol as the major isomer (ee = 75%) [42]. In contrast, the palladium complex [Pd(BINAP)(C3H5)]Cl is inactive for the same reaction [43]. 

Mixing trichlorosilane, acetonitrile and diphenylsulphoxide, carried out at 10°C, detonated. This accident was put down to the exothermic addition reaction of the silicon-hydrogen bond on the carbon-nitrogen triple bond of nitrile. Other interpretations are possible for instance, the effect of traces of hydrogen chloride formed by the hydrolysis of chlorosilane on acetonitrile. 

In all of these cases, paUadium-catalyzed hydrosilylation proceeds via hydropalla-dation followed by reductive elimination of alkyl- and silyl group from the palladium. In the reaction of o-aUylstyrene (24) with trichlorosilane, which gives hydrosilylation products on the styrene double bond 25 and cycUzed product 26, the hy-dropalladation process is supported by the absence of side products which would result from the intermediate of the silylpaUadation process (Scheme 3-11) [37]. 

For the asymmetric hydrosilylation of 1,3-cyclohexadiene (42) (Scheme 3-17), the enantioselectivity is higher in the reaction with phenyldifluorosilane than that with trichlorosilane or methyidichlorosilane. The reaction of 42 with phenyldifluorosilane in the presence of a palladium catalyst coordinated with ferrocenylphosphine... 

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