Silicon hydrides silanes

CaSi-j (Si-Si 248pm) — as in puckered graphite layer SrSii, a-ThSi2 (Si -Si 239 pm closely related to AIBt), a-USi-j 

Silanes Si IF , 2 re now known as unbran-ched and branched chains (up to n = 8) and as cyclic compounds Si H2/i (n = 5,6). Silanes are colourless gases or volatile liquids they 

Combination of these various methods has led to a vast number of derivatives in which H is progressively replaced by one or more monofunctional group such as F, Cl, Br, I, CN, R, Ar, OR, SH, SR, NH2, NR2, etc. i The cyclic silanes SisHm and Si6Hi2 were prepared in the late 1970s via (SiPh) which were themselves the first known homocyclic silane derivatives (F. S. Kipping, 1921)  

WlBERO and E. Amberoer, Hydrides of the Elements of Main Groups I-IV, Chap. 7, pp. 462- 638, Elsevier, Amsterdam, 1971. A comprehensive review of compounds containing Si-H bonds over 700 references. 

SiH3l in partieular is a valuable synthetie intermediate and some of its reaetions are summarized in Table 9.6. SiH3l is a dense, eolourless, mobile liquid, mp —57.0°, bp 4-45.4°, d(15°) 2.035gem  

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Silicon hydride (Silane) (SiH4) Explosive Rapid... 

The stmcture used as the basis of the nomenclature is silane SiH4 corresponding to methane CH4. Silicon hydrides of the type SiH3(SiH2) SiH ... 

Silane coupling agents are generally synthesized through addition of silicon hydrides to unsaturated organic molecules ... 

The hydrogen abstraction from the Si-H moiety of silanes is fundamentally important for these reactions. Kinetic studies have been performed with many types of silicon hydrides and with a large variety of radicals and been reviewed periodically. The data can be interpreted in terms of the electronic properties of the silanes imparted by substituents for each attacking radical. In brevity, we compared in Figure 1 the rate constants of hydrogen abstraction from a variety of reducing systems by primary alkyl radicals at ca. 80°C. ... 

The reaction of thiyl radicals with silicon hydrides (Reaction 8) is the key step of the so-called polariiy-reversal catalysis in the radical chain reduction. The reaction is strongly endothermic and reversible with alkyl-substituted silanes (Reaction 8). For example, the rate constants fcsH arid fcgiH for the couple triethylsilane/ 1-adamantanethiol are 3.2 x 10 and 5.2xlO M s respectively. 

Reactions of silicon hydrides with m-(R3P)2PtCl2 (R = Bu, Ph) have been widely investigated. Alkyl- and aryl-silanes underwent metathetical H/Cl exchange [Eq, (18) (R = Et, Ph, PhCHj, C.H.j)] (55). 

A diaryldihydrosilane with a hexacoordinated silicon center, produced through intramolecular coordination, is reported not to react with benzaldehyde, although the silane is capable of reducing silver ion to silver metal.113 There is also a report of a heptacoordinate silicon hydride species with the ability to transfer hydride to trityl cation while remaining inactive toward methanol.108114... 

In some cases, elements having electronegativities too low to give ionic bonding with hydrogen also tend to be unreactive, so that direct combination of the elements is not feasible. In such cases, the procedure just described can be used to prepare the hydride. For example, silicon hydride, SiH4 (known as silane), can be produced by the reactions... 

The reaction of carbon-centered radicals with silicon hydrides is of great importance in chemical transformations under reducing conditions where an appropriate silane is either the reducing agent or the mediator for the formation of new bonds.23... 

Silicones can be prepared in such a way that they contain only one percent or less of vinyl groups and silicon hydrides, which undergo a catalytic hydrosilylation reaction to give the desired cross-linking (Figure 18.3). Vinyl silanes are made by Si-H addition to acetylene, and thus two hydrosilylations are involved. 

The kinetic data for halogenated carbon-centred radicals with silicon hydrides are also numerous and a few examples are shown in Table 3.2. The kinetic data for perfluoroalkyl radicals were obtained by competition of the appropriate silane with the addition to an olefin [16-18]. The kinetic deuterium isotope effects (/ h/ d) on the attack of on the Si—D bond of... 

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