65146-94-3Relevant articles and documents
The γ-silicon effect. IV. The solvolysis mechanism of 3-(aryldimethylsilyl)propyl p-toluenesulfonates
Fujiyama,Nakashima,Kim,Fujio,Tsuno
, p. 429 - 438 (2007/10/03)
The solvolysis of 3-(aryldimethylsilyl)propyl p-toluenesulfonates was described based on the effects of substituents, solvents, and deuterium isotope, in comparison with the γ-silyl-assisted solvolysis of 3-(aryldimethylsilyl)-2,2-dimethylpropyl toluenesulfonates. The solvent effect on the simple γ-silyl assisted system showed the nucleophilic assistance of solvent, but failed to correlate linearly with the extended Winstein-Grunwald equation, substantiating that the reaction should not proceed through either the formation of the cation intermediate of the SN2 mechanism. This suggested that the reaction occurs in competition between γ-silyl-assisted (kSi) and solvent-assisted (ks) pathways, and that the competition ratio varies with solvents and with aryl substituents. Product analysis revealed that the former pathway gave only cyclopropane and the latter gave only the substitution products. Using product ratios, the overall rate constant (kt) value could be dissected into the partial rate constants kSi and ks for the two pathways. The effects of aryl substitutes at the γ-silyl atom on kSi pathway were correlated with unexalted σ°(normal substituent constant) parameter, giving the ρ values of -1.0 in 60E and -1.32 in 97Tw, and reflecting the delocalization of incipient carbocationic charge by participation of the Si-Cγ bond. The substituent effects on the ks pathway were negligible, which is in line with the remote reaction center in the concerted SN2 mechanism.
Inter- and intramolecular experimental and calculated equilibrium isotope effects for (silox)2((t)Bu3SiND)TiR + RH (silox = (t)Bu3SiO): Inferred kinetic isotope effects for RH/D addition to transient (silox)2Ti
Slaughter, Legrande M.,Wolczanski, Peter T.,Klinckman, Thomas R.,Cundari, Thomas R.
, p. 7953 - 7975 (2007/10/03)
Intermolecular equilibrium isotope effects (EIEs) were measured (26.5 °C) and calculated for (silox)2((t)Bu3SiND)TiR(D) (1-ND-R(D)) + R(H)H ? (silox)2((t)Bu3SiNH)TiR(H) (1-R(H)) + R(D)D: R(H)H/R(D)D = CH4/
Reactions of FeCH3+ and CoCH3+ with Aliphatic Alkenes and Alkynes in the Gas Phase
Jacobson, D. B.,Freiser, B. S.
, p. 5876 - 5883 (2007/10/02)
The gas-phase reactions of FeCH3+ and CoCH3+ with a variety of alkenes are described by using Fourier transform mass spectrometry (FTMS).FeCH3+ is unreactive with ethene, while CoCH3+ reacts with ethene to yield the allyl product CoC3H53.This reaction presumably proceeds by initial methyl migratory insertion into coordinated ethene to form a Co(propyl)+ complex which subsequently dehydrogenates.Reactions with alkenes containing labile hydrogens α to the double bond proceed by initial elimination of methane to form an activated ?-allyl complex which may subsequently decompose further.Both FeCH3+ and CoCH3+ undergo migratory insertion into coordinated butadiene generating a ?-pentenyl complex which undergoes dehydrogenation.In addition, both FeCH3+ and CoCH3+ appear to insert into ethyne, generating a vinyl species which dehydrogenates to form MC3H3+.These results suggest the following order for methyl migratory insertation into C-C multiple bonds: butadiene ca. ethyne > ethene.Decomposition of M(C5H9)+ species proceeds by initial skeletal rearrangement to a linear structure followed by dehydrocyclization to generate M-c-C5H5+.A stable Co(pentadienyl)+ species was generated and is distinguishable from the corresponding Co(cyclopentyl)+ complex by H/D exchange with deuterium.Finally, D0(Fe+-pentadienyl) is found to exceed 70 +/- 6 kcal/mol and D0(Co+-pentadienyl) exceeds 62 +/- 5 kcal/mol.
