Silicon halides metal hydrides

The distinction between between mono- and dinuclear metal complexes is only a formal one in terms of bonding (consider one substituent at silicon the second metal atom instead of an organic group, halide, or hydride substituent). The structural and spectroscopic features related to the three-center bond should therefore be more or less the same as previously discussed. 

The reaction may involve the intermediate formation of a metal hydride which undergoes metathesis with the silicon halide, but no evidence for such a mechanism has been accumulated. 

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... 

The intermediate metal hydride has been isolated on occasion for Co and Mn , and Eq. (b) has actually been used to prepare silicon-metal bonds (see 5.2.3.2.2.). Inspection of Table 1 reveals the ease of reaction of Co2(CO)g compared with the other carbonyls. Normally this reaction is performed simply by condensing volatile silane onto the carbonyl in the absence of solvent and then allowing rapid reaction in the liquid phase at room temperature, but for the remaining carbonyls it is necessary to use elevated temperatures and sealed, evacuated tubes. The products are volatile and readily purified by vacuum fractionation or sublimation, but are often oxygen and moisture sensitive. The route is most efficient for RjSi derivatives of Co, Mn and Re, which are not generally obtainable by the reactions of silicon halides with metal carbonyl anions (see S.8.3.3.I.). In this way lCo(SiR,)(CO -] = Et, Phj, Clj -, (OEt)j, F/, ... 

The reductions of chlorosilanes by lithium aluminum hydride, lithium hydride, and other metal hydrides, MH, offers the advantages of higher yield and purity as well as flexibility in producing a range of silicon hydrides comparable to the range of silicon halides (59). The general reaction is as follows ... 

In the processes described above a silicon halide, ethoxide, or hydride is brought into reaction always with an organic derivative of another metal however, a Si-C bond can also be formed by treating a silylmetal compound, e.g., (triphenylsilyl)-potassium308 or -lithium309 with an aryl or alkyl halide, thus ... 

Silicon, as the heavier homolog of carbon, is fourfold coordinated in its compounds in most cases. This is, for example, reflected by the chemistry of silicates [1]. In these naturally occurring compounds, the silicon atoms are almost exclusively found in Si04-coordination. The situation is similar for synthetic solids, such as extended binary phases like pure silica zeolite-type frameworks [2], SiS2, SiC or Si3N4, and related more complex ternary and multinary solids [3], This is also valid for molecular silicon halides, hydrides, and metal organic (e.g., silicon alkoxides) as well as organometaUic silicon compounds [3, 4],... 

Silicon, like carbon, is relatively inactive at ordinary temperatures. But, when heated, it reacts vigorously with the halogens (fluorine, chlorine, bromine, cmd iodine) to form halides and with certain metals to form silicides. It is unaffected by all acids except hydrofluoric. At red heat, silicon is attacked by water vapor or by oxygen, forming a surface layer of silicon dioxide. When silicon and carbon are combined at electric furnace temperatures of 2,000 to 2,600 °C (3,600 to 4700 °F), they form silicon carbide (Carborundum = SiC), which is an Importeint abrasive. When reacted with hydrogen, silicon forms a series of hydrides, the silanes. Silicon also forms a series of organic silicon compounds called silicones, when reacted with various organic compounds. 

Boron differs from aluminum in showing almost no metallic properties and its resemblance to silicon is greater. Both boron and silicon form volatile, very reactive hydrides the hydride of aluminum is a polymeric solid. The halides (except BF3) hydrolyze to form boric acid and silicic acid. The oxygen chemistry of the borutes and silicates also has certain resemblances. 

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