- Pentacoordinate dihydridosilicates: Synthesis, structure, and aspects of their reactivity
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The reactions of H- with trialkoxysilanes provide a unique and facile entry to anionic pentacoordinate dihydridosilicates [H2Si(OR)3]-, isolated as stable crystalline products in the case of bulky R groups (R = i-Pr, s-Bu, c-C6H11). Their dynamic behavior (R = i-Pr and s-Bu) has been investigated by 29Si and variable-temperature 1H NMR. Intramolecular exchange of H atoms between axial and equatorial sites is indicated and was found to be significantly dependant on the nature of the solvent. Compared to HSi(OR)3, K[H2Si(OR)3] are versatile reagents: (1) the silicon atom is an electrophilic center and this leads to nucleophilic displacements of the alkoxy groups with Grignard reagents and organolithiums; (2) they are able to reduce very easily carbonyl derivatives to alcohols without any catalyst; (3) they react with primary halides through an ionic mechanism leading to the alkane; (4) the reaction with benzylic halides is more complex and affords the dimer as the major product, the formation of which can be explained by a SET process; (5) the ability to donate one electron is confirmed in the reaction with Cp(CO)2FeI and by direct ESR observation of stable radical intermediates.
- Corriu, Robert J. P.,Guérin, Christian,Henner, Bernard J. L.,Wang, Qunjie
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- BIOREMEDIATION USING CO-METABOLISM SUBSTRATES
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Certain disclosed embodiments concern a bioremediation composition comprising microbial cells, at least one co-metabolism substrate to induce selected enzyme production by the microbial cells, and a bead or gel encapsulating the microbial cells, such as bacterial or fungi cells, and the at least one co-metabolism substrate. For certain embodiments, the substrate is a slow release compound, such as an orthosilicate that hydrolyzes to produce an alcohol growth substrate. Embodiments of a method for using the composition to transform contaminants of concern also are disclosed.
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- Reaction of silicon with alcohols in autoclave
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A reaction of activated silicon with alcohols in an autoclave at 240—270 °C was studied. It was found that primary alcohols form tetraalkoxysilanes Si(OR)4 with high selectivity (up to 97%), while the secondary PriOH gave a mixture of compounds HSi(OPri)3, Si(OPri)4, HSi(OPri)2OSi(OPri)2H, HSi(OPri)2OSi(OPri)3, and Si(OPri)3OSi(OPri)3 with the predominance of trialkoxysilane (up to 67%). Carrying out the reaction under the indicated conditions has the advantage of experimental simplicity, reagent availability, high conversion of silicon, good isolated yields of products.
- Krylova,Egorov,Nefedov
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p. 260 - 266
(2017/07/11)
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- Precursors for silica or metal silicate films
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A composition selected from the group consisting of bis(tert-butoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-butoxy)silanol, bis(tert-pentoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-pentoxy)silanol, bis(tert-pentoxy)(tert-butoxy)silanol, bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof; its use to form a metal or metalloid silicate layer on a substrate and the synthesis of the mixed alkoxysilanols.
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Page/Page column 3
(2008/06/13)
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- PRECURSORS FOR SILICA OR METAL SILICATE FILMS
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A composition selected from the group consisting of bis(tert-butoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-butoxy)silanol, bis(tert-pentoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-pentoxy)silanol, bis(tert-pentoxy)(tert-butoxy)silanol, bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof; its use to form a metal or metalloid silicate layer on a substrate and the synthesis of the mixed alkoxysilanols.
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Page/Page column 2
(2008/06/13)
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- Orthosilicate-mediated esterification of monosubstituted phosphinic acids
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(matrix presented) Monosubstituted phosphinic acids are esterified with orthosilicates in excellent yields. Phosphinylidene-containing acids react selectively under these conditions, while disubstituted phosphinic acids and phosphonic acids remain unchanged. One-pot procedures are also described for the preparation of phosphinate esters from an alcohol. This novel method provides a convenient and general alternative to more commonly employed conditions such as diazomethane or carbodiimide.
- Dumond, Yves R.,Baker, Rhonda L.,Montchamp, Jean-Luc
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p. 3341 - 3344
(2007/10/03)
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- Contributions to the chemistry of silicon-sulphur compounds LVI. The imidazole catalyzed alcoholysis of the isosteric isobutyl(isopropoxy)silanethiols i-Bun(i-PrO)3-nSiSH (n = 0-3)
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The kinetics of the imidazole-catalyzed alcoholysis of the isosteric silanethiols i-Bun(i-PrO)3-nSiSH (I) with n = 0-3 in benzene and acetonitrile have been investigated.The alcoholysis of Si-S bond in I is generally first order with respect to both the silanethiol and the catalyst.At low alcohol concentrations the order with respect to alcohol tends to be zero.A mechanism involving an attack of a nucleophilic catalyst on silicon in I in the rate-determining step is proposed.In MeCN solution the reactivities of silanethiols decrease in the sequence i-Bu(i-PrO)2SiSH > i-Bu2(i-PrO)SiSH > (i-PrO)3SiSH > i-Bu3SiSH.The anomeric effect seems to determine the conformations and the reactivities of these silanethiols.
- Pikies, J.,Wojnowski W.
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p. 305 - 312
(2007/10/02)
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- Hetero-?-Systeme XVI. Alkoxysilylene (Alkoxysilandiyle)
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Dimethoxysilylene (2) reacts with acetylene or dimethylacetylene to form 1,4-disilacyclohexadienes in very good yields.The known addition reactions of dichloro or dimethylsilylene with olefins cannot be carried out, with the exception of the addition to 2,3-dimethylbutadiene.The UV spectrum of dimethylsilylene is also markedly different from those of alkylsubstituted silylenes.The UV absorptions of matrix-isolated alkoxysilylenes, prepared by thermolytically induced flash extrusion from disilanes or benzosilepines, show a surprisingly large hypsochromic shift.This effect can be correlated with semi-empirical calculations.
- Maier, G.,Reisenauer, H. P.,Schoettler, K.,Wessolek-Kraus, U.
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