B. A. Gostevskii

Quantum-chemical calculations of NMR chemical shifts of organic molecules: X. Dynamic equilibrium effects in the 29Si NMR spectra of silacycloalkanes

Dynamic equilibria related to change of the coordination number of the silicon atom in bis[N-(dimethylamino) imidato-N′,O]silacycloalkanes in solution were studied by theoretical calculations and experimental measurement of the 29Si NMR chemical shifts. Silacyclopentane derivatives were found to exist in solution as mixtures of species with six- and five-coordinate silicon atoms, and silacyclohexane derivatives, as mixtures of five- and four-coordinate silicon compounds.

Quantum-chemical calculations of NMR chemical shifts of organic molecules: VII. Intramolecular coordination effect in the 29Si NMR spectra of siletanes

The effects of intramolecular N→Si coordination and electronic and conformational factors on the chemical shift of 29Si nucleus in silacyclobutane (siletane) derivatives were studied by quantum-chemical methods. Intramolecular coordination induces upfield shift of the 29Si resonance on the average by 50 ppm when the coordination number of the silicon atom increases by unity. The state of conformational equilibrium of siletane derivatives critically affects the accuracy of δSi predictions.

Peculiarities of the reaction of alkali metal bis(trimethylsilyl)amides with halobenzenes

Lithium and sodium bis(trimethylsilyl)amides react with fluoro-, bromo-, and chlorobenzenes in THF or toluene to give a mixture of N,N-bis(trimethylsilyl)aniline and N,2-bis(trimethylsilyl)aniline. The latter compound is resulted from 1,3-shift of the trimethylsilyl group from nitrogen to ortho-carbon atom of the benzene ring. Effects of the solvent, halogen, and alkali metal nature as well as the reaction conditions on the ratio of isomers were examined. Reaction of iodobenzene with sodium bis(trimethylsilyl)amide in THF produces N,N-bis(trimethylsilyl)aniline and 2-iodo-N,N-bis(trimethylsilyl)aniline, while in toluene a mixture of three products, two indicated above and N,N-bis(trimethylsilyl)benzylamine, was obtained.

Reaction of a stable silylene with tetrahydrofuran

Reduction of 1,3-di-tert-butyl-2,2-dichloro-2,3-dihydro-1H-1,3,2-diazasilole with metallic potassium gave, instead of a stable silylene, 1,3-di-tert-butyl-2,3-dihydro-1H-1,3,2λ2-diazasilylolene, a product of insertion of the latter into the carbon-oxygen bond of tetrahydrofuran, 1,4-di-tert-butyl-6-oxa-1,4-diaza-5-silaspiro[4,5]dec-2-ene.

Synthesis of volatile bis[bis(trimethylsilyl)amide]-substituted boron derivatives

General strategy for the synthesis of organoboron compounds containing bis(trimethylsilyl)amide substituents has been suggested.

N -(Silylmethyl)ureas: synthesis, properties, and structure

The data on the synthesis methods, properties, and structural specific features of N-(silylmethyl)ureas are systematized.

Influence of the polarization effect on the donor properties of 1-phenylsilatrane

A new mechanism of the dipole—induced dipole polarization interaction was considered to explain an anomalous increase in the +I effect in a 1-phenylsilatrane molecule with the pentacoordinated Si atom. The interaction through the space between the silatrane cage having a high dipole moment and easily polarizable aromatic phenyl substituent induces dipole that adds the influence of the inductive effect along the bonds, which is characteristic of usual silatranes. The high inductive constant σI calculated for 1-phenylsilatrane on the basis of chemical shifts δC of aromatic carbon atoms was interpreted as a superelectronodonor effect in silatranes. However, the polarization effect through the space leads to a substantial change in the chemical shifts δC for the phenyl group in the direction that formally corresponds to the enhancement of the +I effect transmitted via the bonds. It is shown for the first time that the inductive effect in silatranes is not constant and varies according to the polarizability of the substituent at the Si atom.

Hydrosilylation of Methylhydrosilyl Derivatives of 1,1-Dimethylhydrazine

Heating of dimethyl(2,2-dimethylhydrazino)silane and methylbis(2,2-dimethylhydrazino)silane with 1-hexene or styrene in the presence of a catalytic amount of rhodium dicarbonylacetylacetonate gives rise to adducts by the terminal carbon atom (yields 45-84%). The same reactions with phenylacetylene give complex mixtures of products formed primarily by disproportionation of the starting organosilicon reagents.