Structure and thermochemistry of β-silicon carbenium ions in the gas phase

Abstract

Both protonation of trimethylvinylsilane and addition of Me3Si+ to ethylene in the gas phase produce the cation Me3Si(CH2CH2)+, with 39 kcal mol-1 stabilization energy relative to ethyl cation; however, chloride abstraction from Me3SiCHCICH3 yields a mixture of ions resulting from competing methyl and hydrogen shifts in the nascent silylcarbenium ion.

Single transition state in the transfer of a neutral phosphoryl group between phenoxide ion nucleophiles in aqueous solution

“…The sterically hindered ' nucleophiles (2,4,6-trichlorophenolate ion, 2,6-dichlorophenolate ion, and 2,6-dimethylphenolate ion) and the data for acetate ion have reactivities well below those predicted from the regression line (eq 4) and may include some general-base component. The sterically hindered ' nucleophiles (2,4,6-trichlorophenolate ion, 2,6-dichlorophenolate ion, and 2,6-dimethylphenolate ion) and the data for acetate ion have reactivities well below those predicted from the regression line (eq 4) and may include some general-base component.…”

Bob Squires: “Reactive organic intermediates. Benzynes, trimethylenemethane and beyond”

“…He strived to make and characterize species that had been proposed as transient intermediates in important organic, 35,42-44 inorganic 45, 46 and organometallic 47-49 reactions, whose spectroscopic characterization was of fundamental interest, 26,50,51 or whose mere existence was controversial. [52][53][54][55][56] Bob viewed the gas phase as the synthetic chemists' wonderland, because the absence of a reactive medium allows one to create "all kinds of exotic creatures in which the traditional notions of stability are tossed out of the window". While many of the ion synthetic methods that he and his students invented arose from a recognized need and deliberate action, many others were born of complete serendipity: they were looking for one thing, and found another.…”

Theoretical Gas‐Phase Stabilities of α‐Trimethylsilyl‐Substituted Tertiary Carbenium Ions

“…The differences were ascribed to steric effects. [6,8,9] Gas-phase experiments by Schwarz showed that α-silyl carbenium ions easily undergo 1,2-methyl and 1,2-H shifts to the β-silylcarbenium ions, [10,11] a fact which further complicates the situation. In theoretical studies, the SiMe 3 group effect is often extrapolated from the simple SiH 3 model calculations, while the influence of several silyl groups on the stability of an adjacent tertiary carbenium ion has not been explored so far.…”