Silicon tetrahalide

Similar results are obtained for dre deposition of the carbides of these metals using methane as a source of carbon, atrd silicon tetrahalides for the preparation of silicides. These reactions are more complex than dre preparation of the diborides because of the number of carbides atrd silicides that the tratrsition metals form, some of which have wide ranges of non-stoichiometry. The control of the ratio of the partial pressures of dre ingoing gases is therefore important as a process variable. 

A highly explosive liquid [1]. Early attempts failed to isolate it but prepared numerous other explosive compounds. Reaction of dichlorine hexoxide with silicon tetrachloride or tetrabromide gave an explosive solid, apparently a perchlorato oligosiloxane. Silver perchlorate and silicon tetrahalides in ether gave explosive volatile organics, perhaps ethyl perchlorate. Replacing ether by acetonitrile as solvent, a solid (di)acetonitrile adduct of the tetraperchlorate precipitated, described as exceptionally explosive even in the smallest quantities [2],... 

Silicon combines with halogens at elevated temperatures forming silicon tetrahalides. With chlorine, reaction occurs at 450°C forming silicon tetrachloride, SiCh. The tetrahalides also are obtained when sdicon is heated with anhydrous hydrogen chloride, bromide and iodide ... 

An extension of the latter type of interaction may be found in, for example, the suggestion that in the Silicon tetrahalides the central atom 3d orbitals act as r-acceptors for the lone pair electrons on the halogen atoms. In resonance terms this amounts to the contribution of the ionic double-bond structures to the ground state of the molecule (Fig. 4). 

What is the most commonly produced silicon tetrahalide How is it used Why might its toxicological properties be similar to those of HC1 ... 

While silicon tetrahalides also form adducts with amine N-oxides (Me3NO, pyO or bipyO)134, the reaction of Si2Clg with bipyO results in a redox reaction under cleavage of the Si—Si bond135 (equation 73). 

T. Gilson, M. Webster, and G. P. McQuillan The Stereochemistry of Addition Compounds of Silicon Tetrahalides, Studied by Their Spectra in the Caesium Bromide Region. J. chem. Soc. 1964, 238—44. 

Kakiuchi, Y. The normal vibrations of some silicon tetrahalides as calculated by the Urey-Bradley field. Bull. chem. Soc. Japan 26, 260-261 (1953). 

It follows that in this method of cocondensation one may employ even an unsubstituted silicon tetrahalide or orthoester in the mixture as a source of tetrafunctional groups. The unsubstituted SiX4 (where X is a halogen or ester group) hydrolyzes to the hypothetical ortho-silicic acid, Si(OH)4, and this cocondenses with the equally hypothetical organosilanediol to incorporate the silica unit within the polymeric structure ... 

In the early 19th century, Gay-Lussac discovered F Si 2 NHj. Three years later Davy obtained the same compound and Davy and Berzelius synthesized other compounds of six-coordinate silicon fluorosilicic acid, HjPiFg], and its salts, the hexafluorosilicates In the second half of the last century adducts of silicon tetrahalides with tertiary amines were synthesized . In 1903 Dilthey investigated silicon diketonates containing six-coordinate silicon In the first half of our century the possibility of the presence of Si(OH)g ions in silica was widely discussed Interest in five- and six-coordinate silicon compounds increased in the second half of the present century. As a result, new classes of silicon compounds with an expanded coordination sphere were discovered and were studied by various physical and chemical methods. Specific biological activity was observed for some of the compounds and promising ways of their practical application were planned... 

The physical properties of silicon tetrahalides are listed in Table 1 those of the halohydrides are listed in Table 2. A more complex review of the physical properties of these chemicals is available (2). Detailed lists of properties of the colorless fuming liquids, silicon tetrachloride and trichlorosilane, are given in Table 3. A review of the physical and thermodynamic properties of silicon tetrachloride is given in Reference 3. 

The water is retained by the sulphuric acid, and the SiF4 is freed from HF by passing it over dry NaF. The other silicon tetrahalides are generally made by direct combination with the halogen. Mixed tetrahalides such as SiFgCl and SiClgBrg have also been obtained (Schumb, 1942). 

Novel Hypercoordinate Silicon Complexes from Silicon Tetrahalides and Bidentate <0,N> Donor Ligands... 

Table 13.3 Selected physical properties of the carbon and silicon tetrahalides.

A further method often used for preparation of organosilicon compounds is a Wurtz-type synthesis in which a silicon tetrahalide is condensed with an alkyl or aryl halide by means of metallic sodium in ether or a hydrocarbon solvent 313... 

If an alkyl- or aryl-silicon halide is used in place of the silicon tetrahalide, unsymmetrical organosilicon compounds can be synthesized in this way.314... 

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