33335-65-8Relevant academic research and scientific papers
Kinetic hydricity of silane hydrides in the gas phase
Xu, Jiahui,Krajewski, Allison E.,Niu, Yijie,Kiruba, G. S. M.,Lee, Jeehiun K.
, p. 8002 - 8008 (2019/09/06)
Herein, gas phase studies of the kinetic hydricity of a series of silane hydrides are described. An understanding of hydricity is important as hydride reactions figure largely in many processes, including organic synthesis, photoelectrocatalysis, and hydrogen activation. We find that hydricity trends in the gas phase differ from those in solution, revealing the effect of solvent. Calculations and further experiments, including H/D studies, were used to delve into the reactivity and structure of the reactants. These studies also represent a first step toward systematically understanding nucleophilicity and electrophilicity in the absence of solvent.
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.
