Reactions with silicon halides

Silicon tetraisothiocyanate, reaction with 2,6-dimethylaniline to yield 2,6-diraethylphenyl thiourea, 46, 70 Silver cyanide, reaction with alkyl halides in synthesis of isocyanides, 46, 77... 

Silicon halides react with complex hydrides to form silanes. Complex hydrides used are LiAlH and to a lesser extent MBH (M = Li, Na, K) . Reductions are carried out in aprotic ether solvents, e.g., Et O, glymes, THE or n-BUjO. These reactions are adaptable to Si—D bond synthesis (see 1.6.7.1.2). Typical syntheses of monosilanes are shown in Table 1. Chlorosilanes are preferred the fluorides react less readily. Bromo- and iodosilanes react easily but offer no advantage over the more available chlorides. ... 

In practice vapours of the hydrocarbon halide, e.g. methyl chloride, are passed through a heated mixture of the silicon and copper in a reaction tube at a temperature favourable for obtaining the optimum yield of the dichlorosilane, usually 250-280°C. The catalyst not only improves the reactivity and yield but also makes the reaction more reproducible. Presintering of the copper and silicon or alternatively deposition of copper on to the silicon grains by reduction of copper (I) chloride is more effective than using a simple mixture of the two elements. The copper appears to function by forming unstable copper methyl, CUCH3, on reaction with the methyl chloride. The copper methyl then decomposes into free methyl radicals which react with the silicon. 

Amorphous Si3N4 powder from silicon halides and ammonia at high temperature.P lP l The powder can also be produced by using the same reaction at 1000°C in an RF plasma with a mean particle size of 0.05-0.1... 

Interesting cyclic ionic species are obtained from the reactions of di(phosphazenyl)silanes with silicon halides at room temperature ... 

Analogously to linear silicon halides, SigMenX does not react with Na[Co(CO>4]. However Na[Co(CO)3PPh3] and Na[Fe(CO)2cp] result in the respective transition metal-substituted silicon rings after reaction with SigMei X or 1,4-Si6Mei0X2. 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

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