Salts silicon compounds

The study of compounds containing pentacoordinate silicon atoms currently represents one of the main areas of research in silicon chemistry. This is evident from the numerous reviews and proceedings published on this topic in recent years.112 Most of the pentacoordinate silicon compounds described in the literature are either salts with A5.S7-silicate anions or neutral silicon complexes with a 4+1 coordination to silicon. This review deals with a completely different class of pentacoordinate silicon compounds zwitterionic A S /-silicatcs. These molecular compounds contain a pentacoordinate (formally negatively charged) silicon atom and a tetracoordinate (formally positively charged) nitrogen atom. 

Of course, any tetrahedral atom, not just caibon, that has four different groups bonded to it is a chirality center, and compounds containing such atoms will exist as a pair of enantiomers. Many such compounds have been prepared and resolved, including the following quaternary ammonium salt and the silicon compound ... 

Silyl cyclopentadienes1,2 3 have been formed through the interaction of a cyclopentadienide prepared in situ with an appropriate silicon halide however, purification of the desired product required filtration, removal of solvent, and vacuum distillation at elevated temperatures. The synthesis of the silicon compounds, C5H5(SiH3) and C5H4(CH3)(SiH3), described here utilizes a low-temperature reaction between liquid bromosilane and the salt K[RC5H4] (where R = H, CH3), in a 1 2 mole ratio, respectively.4 5... 

The oxidation of silanes also can be accomplished by solutions of potassium permanganate, mercuric salts, ferric compounds, and cupric salts. Plain water also will oxidize the silicon-hydrogen bond in the presence of hydroxyl ions as catalysts 6... 

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... 

Silicon halides (especially the readily available chlorides) are probably the most synthetically useful and versatile monomeric inorganic silicon compounds. They may readily be reduced to hydrides, hydrolyzed to silanols (and subsequently to siloxanes), treated with other protic species such as alcohols, carboxylic acids, amines, and thiols to give SiA)R, Si-0C(0)R, Si NR2, and Si SR species respectively, used to make sUyl pseudohalogen derivatives by treatment with silver or alkali metal salts, for example, treated with sodium... 

Salts of Grignard and analogous compounds are placed under the formula of the hydroxide. Organic silicon compounds are treated in the same manner when only one acid group is present. If more than one acid group is present, the salt is indexed under its own formula. 

They are often blended into compounds that are developed for injection molding applications. Where such an additive is absent, molded components tend to stick to mold surfaces. To prevent this, mold surfaces must be treated between every cycle, or they can be coated with a range of semipermanent mold release treatments. Inclusion of an internal release agent prevents mold surface build-up, surface charring, and simplifies production. Internal mold release agents may include hydrocarbons, alcohols, carboxylic acids, halogenated compounds, ketones, carboxylic acid esters, amides, metal salts, and silicone compounds. 

PZCs/IEPs of sparingly soluble salts (other than combination of two or more sparingly soluble oxides) are presented in Tables 3.1568 through 3.1910. PZCs/IEPs of silicon carbide and nitride are also presented in this section. Salt-type compounds composed entirely of sparingly soluble oxides are discussed in Section 3.3. In the studies devoted to the effect of water-soluble salts with an anion or cation in common with the sparingly soluble salt of interest, the IEP has been defined in terms of concentration of these salts (ions) in addition to (or rather than) pH. 

No optically active five-coordinated silicon compounds have been obtained. However a chiral hexacoordinate silicon trisacetylacetonate cation (23) has been resolved by Dhar, Doron, and Kirschner (40) through the separation of diaste-reomeric dibenzoyl-d-tartrate salts (eq. [21]). 

Hypervalent silicon compounds have found wide utility in organic synthesis. In general, pentacoordinated anionic silicates are more reactive toward nucleophiles than are tetracoordinated silanes. For example, Mes2SiF2 is unreactive toward water, while (the 18-crown-6 potassium salt of) Mes2SiF3 is completely hydrolyzed within minutes. Similarly, the pentacoordinate anion HSi(OEt)4 is an effective reducing agent for aldehydes, ketones, and esters at or below room temperature (Scheme 2) no such reaction occurs with HSi(OEt)3. The difference in relative reactivities of hypervalent and nonhypervalent species is relevant to the intermediates proposed in Section 7.6. 

The alkali metal salts of the six-coordinate anion (61) may readily be prepared (equation 61) by using Si02 (or Si(OMe)4) as starting material, thus forming monomeric silicon compounds from the polymeric Si02 without the need for the isolation of elemental silicon. 

Among the salts of Group 14 elements, silicon compounds are especially sensitive to moisture and they easily react with water and ethanol at room temperature to give the corresponding dithiocarboxylic acids [7,12,13]. In contrast. 

This section contains miscellaneous organic compounds of As, B, P, Si, S, Se, Te, and ammonium and metal salts of their acids, and salts of their bases. See other sections and chapters for further entries of sulfur, phosphorous and silicon compounds and for sulfur heterocyclic compounds see section on Heterocyclic Compounds ,... 

We were able to prepare salen silicon complexes by reaction of the salen ligand as free acid (Scheme 2) or sodium salt (Scheme 1) with the corresponding chloro silicon compound. It is also possible to use Si2Cl6 as starting compound to get (salen )SiCl2 (Scheme 2). 

Examples of volatile nonmetallic compounds are very familiar methane, ammonia, water. Examples of involatile compounds are silicon carbide (SiC) and silica (Si02). The former is manufactured by heating silica with graphite and is sold under the name carborundum. The commereial produet is black, but when pure it is colourless. It melts at about 2700 C. Pure silica also forms colourless crystals, melting to a colourless liquid at about 1600 °C and boiling at about 2400 C. Both compounds are insulators. Conductivity measurements have also been made on liquid silica, in which state it remains a poor conductor (cf salt-like compounds). 

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