Silicon—hydrogen bonds reactions with

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. 

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... 

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. 

Thus in vessels of fused quartz the silanes do not react with water,9 but the alkali extracted by the water from an ordinary glass flask (or from chips of ordinary glass introduced into the silica vessel) suffices to catalyze the reaction. The hydrogen is liberated quantitatively from any silion-hydrogen bond by dilute solutions of the alkalies, one molecule of hydrogen for each silicon-hydrogen bond. 

Copper complexes derived from bis(-2,6-dichlorophenyle-dene)-( 15,25)-1,2-diaminocyclohexane (11) catalyze various reactions such as Diels-Alder reaction, aziridination (eq 20), cyclopropanation, and silyl enol ether addition to pyruvate esters. Although the scope of these reactions may be sometimes limited, enantioselectivities are generally high. The same complex (with copper(I) salts) catalyzes the asymmetric insertion of silicon- hydrogen bond into carbenoids. ... 

Silicon-hydrogen bonds form in reactions of alkali-metal hydrides with Si,H, ... 

Attempts to initiate a desirable second insertion of PhN=C=X into the remaining silicon-hydrogen bond in compounds 6a or 6b failed. However, if a 10-fold excess of PhN=C=X (X = S, O) is used, trimers of phenylisothiocyanate (8a) or phenylisocyanate (8b) are formed. The latter can also be obtained in much better yields by direct reaction of 1 with a 10-fold excess of PhN=C=X. 

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