Silicon, nucleophilic displacement

The reaction of the carbonyl metallates with chlorosilanes (Eq. (5)) can be considered to be a nucleophilic displacement at the silicon followed by NaCl elimination. Several arguments support this view First of all, strong dipolar aprotic... 

In the case of anionic systems, following the ideas of Diinitz [6], crystal structure (C) is a good model of an intermediate in which a nucleophile attacks a silicon atom included in a pentacoordinated anionic structure. Such an intermediate occurs during the nucleophilic displacement illustrated in Scheme 3. 

The second step is now the study of the reactivity of these hexacoordinated silicon species towards nucleophiles in order to obtain Si-C or SiH bond formation. The nucleophilic attack takes place at silicon with displacement of catechol and formation of organosilanes. 

Although carbon and silicon both belong to the same group of periodic table and many of the silicon compounds resemble carbon compounds, but the chemical reactivity of silicon in organosilicon compounds is more comparable to that of hydrogen because many nucleophilic displacements at... 

SN2 nucleophilic displacements at the silicon atom are much more facile, particularly with elements which are more electronegative. Compounds of the type R3SiX (X = leaving group) hydrolyse rapidly in aqueous solutions. 

This is why SN2 type of displacements are more facile at the silicon atom than at the carbon. This is particularly so with nucleophiles derived from the more electronegative element. In compounds of the type of R3SiX (where X = leaving group), the nucleophilic displacements and hydrolysis in aqueous media occur rapidly. 

Nucleophilic displacement reactions at silicon are very useful for formation of bonds from silicon to carbon and to electronegative elements. Some examples are ... 

Nucleophilic Displacement at Silicon Recent Developments and Mechanistic... 

In recent years, mainly from the 1960s on, a great number of stereochemical studies of substitution at silicon by nucleophiles have been carried out. The earlier work, up to 1964, is the subject of an important monograph by Sommer (/) more recent studies have also been summarized by him (2) and others [see Prince (2) and Fleming (4)] in comprehensive surveys. Recently, we collected the main known features in this area (5). The intent of this chapter is to focus upon the latest developments concerning nucleophilic displacement at silicon and to survey the following topics ... 

Frontier-orbital approximations. A consistently useful frontier-orbital approximation for nucleophilic displacement at silicon was ex-... 

NUCLEOPHILIC DISPLACEMENT AT SILICON CONTROLLING FACTORS OF THE STEREOCHEMISTRY... 

In conclusion, all these observations suggest the presence of a five-coordinate silicon intermediate both in nucleophilic displacements at silicon and in the racemization of halosilanes as previously suggested (5, 59). The ability to form a pentacoordinate silicon adduct is not controlled by the electronegativity of the substituents at silicon, but by the tendency of the Si—X bond to be stretched under the influence of a nucleophile ... 

NUCLEOPHILIC DISPLACEMENTS AT SILICON A RATIONALIZATION OF THE STEREOCHEMISTRY BY A FRONTIER-ORBITAL APPROXIMATION... 

Cryptand Effect on the Stereochemistry and Rate of Nucleophilic Displacements at Silicon... 

Studies in the stereochemistry of nucleophilic displacements at silicon over the past few years have been numerous. Significant progress has been achieved in establishing the controlling factors of the stereochemistry (i) the lability of the leaving group, (ii) the electronic character of the nucleophile, and (iii) the bond angles at silicon. 

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