With silicon-hydrogen bonds

The oxidative addition of silanes (with silicon-hydrogen bonds) to coordinatively unsaturated metal complexes is one of the most elegant methods for the formation of metal-silicon bonds. Under this heading normally reactions are considered which yield stable silyl metal hydrides. However, in some cases the oxidative addition is accompanied by a subsequent reductive elimination of, e.g., hydrogen, and only the products of the elimination step can be isolated. Such reactions are considered in this section as well. 

Radu NS, Tilley TD (1995) Autocatalytic mechanism for o-htnid metathesis reactirais of (t -C5Me5)2SmCH(SiMe3)2 with silicon-hydrogen bonds. J Am Chem Soc 117 5863... 

The hydrogen content Ch greatly influences structure and consequently electronic and optoelectronic properties. An accurate measurement of Ch can be made with several ion-beam-based methods see e.g. Arnold Bik et al. [54]. A much easier accessible method is Fourier-transform infrared transmittance (FTIR) spectroscopy. The absorption of IR radiation is different for different silicon-hydrogen bonding configurations. The observed absorption peaks have been indentified [55-57] (for an overview, see Luft and Tsuo [6]). The hydrogen content can be determined from the absorption peak at 630 cm , which includes... 

III. Hydrogen Interaction with Silicon Dangling Bonds... 

It was noted in the early study by Pankove et al. (1985) that the hydrogen vibrational frequency appropriate to the H—B pair was in the range consistent with a hydrogen bonded to a silicon but was in fact somewhat smaller than that expected for an isolated hydrogen connected to a single silicon. Generally, if an atom becomes more confined, the frequency is expected to increase. It was suggested that the frequency reduction was due to a three-body effect well known in molecules. 

Table I includes the relative bond dissociation enthalpies obtained for some group 14 hydrides by photoacoustic calorimetry,7 10 The data demonstrate that, for the trialkyl-substituted series, the bond strengths decrease by 6.5 and 16.5 kcal/mol on going from silane to germane and to stannane, respectively. The silicon-hydrogen bonds can be dramatically weakened by successive substitution of the Me3Si group at the Si-H functionality. A substantial decrease in the bond strength is also observed by replacing alkyl with methylthio groups.

The most complete mechanistic studies have been made with trisubstituted silanes, which initially undergo an exclusive silicon-hydrogen bond cleavage. Retention of configuration occurs in the ozonolysis of 1-decahydronaphthylcyclohexylmethylsilane 68 to the corresponding hydroxide ... 

Methods for the detection of placement and quantitation of Si-H, Si-OH and Si-0 groups in molecular weight components of silicones of the polydimethylsiloxane type have been developed using SEC-IR and SEC-UV on-line techniques. In the case of silanols, problems with partial hydrogen bonding were overcome by use of 1,4-dioxane mobile phase. For phenyl groups, methylene chloride was effective for qualitative measurements and THF yielded quantitative results at high sensitivity. 

Burger. P. and Bergman, R.G. (1993) Facile intermolecular activation of carbon-hydrogen bonds in methane and other hydrocarbons and silicon-hydrogen bonds in silanes with the iridium(III) complex Cp (PMe3)Ir (CH3)(OTf). J. Am. Chem. Soc., 115 (22). 10462-10463. 

None of these difficulties arise when hydrosilylation is promoted by metal catalysts. The mechanism of the addition of silicon-hydrogen bond across carbon-carbon multiple bonds proposed by Chalk and Harrod408,409 includes two basic steps the oxidative addition of hydrosilane to the metal center and the cis insertion of the metal-bound alkene into the metal-hydrogen bond to form an alkylmetal complex (Scheme 6.7). Interaction with another alkene molecule induces the formation of the carbon-silicon bond (route a). This rate-determining reductive elimination completes the catalytic cycle. The addition proceeds with retention of configuration.410 An alternative mechanism, the insertion of alkene into the metal-silicon bond (route b), was later suggested to account for some side reactions (alkene reduction, vinyl substitution).411-414... 

The photoelectrochemistry at atomically well-defined semiconductor surfaces is one of the current topics related to the nanostructuring of the semiconductor surfaces. Most studies have been made on silicon (Si) surfaces, and it is now well established that hydrogen fluoride (HF)-etched Si surfaces are terminated mainly with Si-hydrogen bonds (SiH , n = 1, 2, or 3)14-171 and that, for Si (111), successive etching with 40% ammonium fluoride (NH4F) produces atomically flat Si(l 11) surfaces, terminated mainly with monohydride (= Si-H).18-221 Alkali etching under negatively applied biases also produces similar atomically flat Si (111) surfaces.231... 

Certain reactions of silyl—alkali metal compounds, such as coupling of (CH3) (C6H5)3 BSiLi with appropriate chlorosilanes (51) and hydrolysis of [(CH3)3Si]3SiLi (63), lead to the formation of organopolysilanes with the silicon-hydrogen bond. There have been few reports of such synthesis. 

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