The first stable dibenzosilafulvene, 9-{[8-(dimethylaminomethyl)-l-naphthyllphenylsil-1-ylium}fluoren-9-ide (Ta), was obtained in one step from 9-fluorenyllithium and chloro[8-(dimethylarninomethyl)-l-naphthyllphenylsilane as a stable solvate with THF. The structure of the zwitterionic compound 7a was established by IH, 13C, and 29Si NMR in solution and in the solid state. The reactions of compound 7a with crotonaldehyde, ethanol, and triethylethylidenephosphorane are described. 1"he data on the synthesis of alkoxy-and alkylthiochloro-9-fluorenylsilanes and their phosphortium salts are given.
The dynamic stereochemistry of silatropic rearrangements of tetrahydro-4,4,8,8-tetramethyl-4,8-disi[a-sym-indacene (dimer of 6,6-dimethyl-6-silafulvene), which exists in solution a.s an equilibrium rnixmre of two interconverting isomers, was studied. The mechanisms and complete kinetic scheme of rearrangements were established using IH, taC, and 29Si 2D quantitative EXSY NMR spectroscopy. It was tbund that the interconversion and degenerate rearrangements of the observed isomers proceed via two concurrent pathways due to the formation of different intermediates. The activation parameters of the rearrangements were determined by means of total lineshape analysis of dynamic NMR (DNMR) spectra.
= Ge (4) and Sn (5) were measured for the first time and analyzed within the framework of DFT calclations. Monomeric compounds 1 and 2 whose molecules are stabilized only through intramolecular coordination were confirmed to be isostructural. Unlike 1 and 2, plumbylene 3 is a polymer in both solution and the crystalline state; the latter was confirmed by X ray diffraction analysis. The ν s C-N stretching frequency in the CH 2 NMe 2 fragment was shown to decrease by 80-100 cm -1 owing to the formation of the coordination bond El←N. To elucidate the mechanism of a dynamic flip flop process suggested earlier based on the broadening of some signals in the NMR spectra of compounds 1 and 4, the Raman spectra of solutions of compounds 1 and 2 in THF and Py were obtained. These experiments revealed no equilibrium with participation of a stable form with one coordination bond El←N cleaved along with the starting molecule. This is consistent with the results of the corresponding quantum chemical calculations of thermo dynamic parameters. A somewhat different, more probable mechanism of the dynamic process was proposed, which involves an overturn of the CH 2 NMe 2 fragment with cleavage of the El←N bond in the transition state only.
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