73818-10-7Relevant academic research and scientific papers
Organosilanes as Radical-based Reducing Agents with Low Hydrogen Donating Abilities
Ballestri, Marco,Chatgilialoglu, Chryssostomos,Guerra, Maurizio,Guerrini, Andrea,Lucarini, Marco,Seconi, Giancarlo
, p. 421 - 425 (2007/10/02)
Me3SiSi(H)Me2, Me3SiSiMe2Si(H)Me2, and (Me3Si)3SiSi(H)Me2 have been used as radical-based reducing agents for a variety of organic substrates.Rate constants for the reaction of primary alkyl radicals with these silanes have been measured over a range of temperature by using the neophyl rearrangement as a radical clock.Some kinetic data have also been obtained for phenyl substituted silanes.The experimental findings are complemented by ab initio MO studies, at different levels of theory, which predict the Si-H bond dissociation energies of PhSiH3, Ph2SiH2, and XSiH2SiH2-H, where X = H, Me and SiH3.The radical trapping abilities of these silanes and other common radical-based reducing agents are compared.
Kinetics of hydride transfer reactions from hydrosilanes to carbenium ions. Substituent effects in silicenium ions
Mayr, Herbert,Basso, Nib,Hagen, Gisela
, p. 3060 - 3066 (2007/10/02)
Rates of hydride transfer from hydrosilanes HSiR1R2R3 with widely varying substitution to para-substituted diarylcarbenium ions have been measured in dichloromethane solution. Generally the reactions follow a second-order rate law, -d[Ar2CH+]/dt = k2[Ar2CH+][HSiR1R2R3], and k2 is independent of the degree of ion-pairing and the nature of the counterion (exceptions are reported). The reaction rates are almost independent of solvent polarity. Kinetic isotope effects exclude an SET-type mechanism and are in accord with a polar mechanism with rate-determining formation of silicenium ions. The reactivities of para-substituted aryldimethylsilanes are linearly correlated with σp (ρ = -2.46), not with σp+. In the series H3SiHex, H2SiHex2, HSiHex3, the relative reactivities are 1.00:155:7890, and in the corresponding phenyl series the reactivity increase is much smaller (H3SiPh:H2SiPh2:HSiPh3 = 1.00:17.2:119). As a consequence, trihexylsilane is approximately two orders of magnitude more reactive than triphenylsilane though hexylsilane and phenylsilane show similar reactivities. Tris(trimethylsilyl)silane is just slightly more reactive than trimethylsilane. Replacement of hydrogen by chlorine reduces the reactivity by one order of magnitude. Variation of the electrophilicities of the hydride abstractors does not affect the relative reactivities of the silanes, i.e., constant selectivity (Ritchie-type) relationships are encountered. Correlation equations are given, which permit the calculation of hydride transfer rates from hydrosilanes to any carbenium ion on the basis of pkR+ values or the ethanolysis rate constants of the corresponding alkyl chlorides.
