Halohydrides

The physical properties of siUcon tetrahaUdes are Hsted in Table 1 those of the halohydrides are Hsted in Table 2. A more complex review of the physical properties of these chemicals is available (2). Detailed Hsts of properties of the colorless fuming Hquids, siUcon tetrachloride and trichlorosilane, are given in Table 3. A review of the physical and thermodynamic properties of siUcon tetrachloride is given in Reference 3. 

Magnesium does not form stable Grignard reagents with siUcon haUdes, although some siUcon halohydrides do react, forming polysilanes (15). 

The sihcon halohydrides are particularly usehil intermediate chemicals because of their abiUty to add to alkenes, as follows (19,20) ... 

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. 

Oxidative addition of other X H compounds other than H2 can also lead to the formation of hydrides. For example, silanes H S1R3 give sUyl hydrides, hydrohalic acids give halohydrides, and Orthometalation of aryl C-H gives an orthometalated aryl hydride (equations 6 and 7). 

The study of silicon halides began in the eady 1800s (1). Since then, essentially all of the monomeric silicon halides have been extensively studied and reported in the literature. These include mixed silicon halides and halohydrides. A large number of halogenated polysilanes have also been reported (1). Despite the extensive research in silicon halides, only two of these chemicals are produced on alaige industrial scale (excluding oiganohalosilanes). These are tetrachlorosilane [10026-04-7], SiCl and trichlorosilane [1025-78-2], HSiCl. ... 

Reaction of LiAlD, with halohydrides allows synthesis of specifically labeled mixed H-D compounds ... 

Two hydride phases, ThIjHg, and Thl H, with dissociation pressures at RT of ca. 10 Pa form from Thij. Other halohydrides prepared include LaljHg j, 2 0,82 ... 

In neither case does one observe the expected products from simple oxidative addition, the halohydrides, HMX, though the latter may be prepared by other methods (M = Be, Mg, Ca, Sr, Ba ). The same course is observed in organic solvents. As expected, donor solvents facilitate the reaction, and in some cases addition of MX2 has the same effect. In aqueous medium, the metals react very readily with the halacids, yielding the (hydrated) MX2 species with the following exceptions ... 

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