Radiochemical Study of Reactions of Diethylsilylium Ions with Dibutyl Ether in the Gas and Liquid Phases

Reactions of diethylsilylium ions with dibutyl ether in the gas and liquid phases were studied radiochemically. These reactions, as those with benzene and alcohols, are accompanied by partial rearrangement of diethylsilylium ions into monoethylsilylium and dimethylsilylium ions. The extent of transformations of the (C₂H₅)₂SiT⁺ ions decreases in going from benzene to dibutyl ether, which is due to the higher energy of adduct formation with the ether, compared to benzene.     

Ion-Molecular Reactions of Diethylsilylium Ions with Alcohols in the Gas Phase

Radiochemistry was used to study reaction of tritium-labeled diethylsilylium ions with alcohols in the gas phase. The reaction involves both rearrangement of the diethylsilylium ions and isomerization of the substituent in the substrate. The hydroxyl hydrogen of the alcohol and the tritium atom of the diethyl-silylium ion undergo exchange which, however, is less vigorous that in the case of the monoethylsilylium ion. A possible reaction mechanism is proposed.     

Radiochemical study of interaction of the nucleogenic diethylgermylium cations with benzene in the gas and condensed phases

Interaction of free diethylgermylium ions with benzene in the gas and condensed phases was studied by the radiochemical method. A possible mechanism of the ion-molecular reactions was suggested. At the interaction of these ions with benzene the products of germylation of the latter were not detected. More advantageous are the processes of degermylation leading to the formation of tritium-labeled benzene. A possibility of rearrangement of the nucleogenic diethylgermylium cation into other isomeric forms was revealed, these forms were calculated by B3LYP method with the 6–31G* and cc-pVTZ basis sets.     

Radiochemical investigation of the interaction of nucleogenic diethylgermylium ions with methyl <Emphasis Type="Italic">tert</Emphasis>-butyl ether

Radiochemical method was used in the study of the interaction of free diethylgermylium cations with methyl tert-butyl ether in the gas and condensed phases, and the mechanisms of the relevant ion-molecular reactions were proposed. The most probable pathways of the (C₂H₅)₂TGe⁺ cation transformation into other isomeric forms are shown as a result of B3LYP calculation with cc-pVTZ basis set.     

Isomerization of silicenium and germenium ions in the systems C<Subscript>4</Subscript>H<Subscript>11</Subscript>M<Superscript>+</Superscript> (M = Si,Ge)

Equilibrium structures of the isomers and transition states of their interconversion in the system C₄H₁₁M⁺ (M = Si, Ge) have been obtained at theB3LYP level of theory using the cc-pVTZ basis set. The structures of these stationary points are close for Si and Ge; the most stable isomer in both systems is the tertiary cation (C₂H₅)(CH₃)₂M⁺, the second in energy is complex with ethylene [(CH₃)₂HM·C₂H₄]⁺. The secondary cation (C₂H₅)₂HM⁺ is third in energy isomer, the height of the barrier of interconversion for these three cations being practically independent on M. However, for M = Ge a substantial decrease in the energy of isomeric forms corresponding to complexes with alkanes is observed. As a result, in the system C₄H₁₁Ge⁺ the fourth in energy is isomer [(C₂H₅)Ge·C₂H₆]⁺ rather than [(C₂H₅)H₂Ge·C₂H₄]⁺ as for M = Si. Nevertheless, the height of the barriers for transition into these structures, although decreasing from M = Si to Ge, remain rather high, and the most favorable route of decomposition in both systems is the elimination of ethylene.     

New intracomplex compounds of pentacoordinate germanium. Hypogermatranes,Ge-substituted (N→Ge) 2-oxa-5-aza-1-germacyclopentanes

Russian Journal of General Chemistry -     

Gas phase reaction of nucleogenic dimethylgermylium cations with benzene

Reaction of nucleogenic dimethylgermylium cations with benzene in the gas phase was studied by the radiochemical method. The formation of the products of germylation of benzene, dimethylphenylgermane, and phenylgermane is indicative of the formation of dimethylgermylium cations by the β-decay of tritium in the molecule of dimethylditritium germane. Dimethylgermylium cations are shown to undergo a rearrangement in the course of the reaction with benzene, which is consistent with the earlier results of quantum-chemical calculations.     

Radiochemical Study of the Reactions of Diethylsilylium Ions with Hexamethyldisilazane and Isobutylamine in the Gas Phase

Ion-molecule reactions of diethylsilylium ions with hexamethyldisilazane and isobutylamine were studied radiochemically. These reactions, like the previously studied reactions of diethylsilylium ions with tert-butylaminotrimethylsilane, occur exclusively along the condensation pathway; in both cases, the diethylsilylium ion undergoes a rearrangement. The extremely low degree of rearrangement of the diethylsilylium ion and high yield of the labeled substrate in the reaction with isobutylamine are due to the presence of two labile N-H hydrogen atoms, resulting in active isotope exchange between the Si-T tritium atoms and N-H hydrogen atoms and in shorter lifetime of the condensation complex, caused by more intense bimolecular deprotonation of the complex.     

Longitudinal polarization of direct muons with p⊥ = 1.9 GeV/c produced in NN collisions

The longitudinal polarization of direct muons with 1.9 GeV/c transverse momentum produced by 70 GeV protons on the copper target has been measured to be η = ?0.41 ± 0.17.     

Effect of the Electronic Structure of Carbenium and Silylium Ions on Their Chemical Behavior

Being isoelectronic analogs, silylium and carbenium ions exhibit quite a different reactivity toward nucleophiles. This is explained by their different electronic structures and charge distributions: In silylium ions the positive charge is almost completely concentrated on the silicon atom, and hydrogen atoms on the cationic center are hydride in nature, wheteas in carbenium ions, the positive charge is uniformly distributed between the carbenoid center and hydrogen atoms.