Conformational studies by dynamic NMR, 69 - Conformation and stereodynamics of aliphatic triisopropylsilanes in solution and in the solid state.
European Journal of Organic Chemistry
479 - 484.
A dynamic process has been detected in the solution C-13-NMR spectra of tBu-Si(iPr)3 (4) in the temperature range -145 degrees C to -163 degrees C, the corresponding free energy of activation being 5.5 kcal mol(-1). Molecular mechanics calculations have identified three types of conformations that are markedly more stable than all the others, but the one with the highest symmetry cannot be populated, as is evident from the appearance of the spectrum at low temperature. This spectrum can be interpreted in terms of restricted rotation of the tert-butyl group and of the isopropyl groups, leading to a structure centered around the (a,g,-g) conformation. In the case of the analogous (iPr)3SiCl derivative (5), this dynamic process was not observed in solution, but an appropriate spectrum for the same (a,g,-g) conformation was obtained by the solid-stale CP-MAS NMR spectroscopy at -100 degrees C
|Title:||Conformational studies by dynamic NMR, 69 - Conformation and stereodynamics of aliphatic triisopropylsilanes in solution and in the solid state|
|Additional information:||Journal Article FEB 310YC Anderson JE Univ London Univ Coll, Dept Chem, Gower St, London WC1H 0AJ, England EUR J ORG CHEM|
|Keywords:||ACTIVATION, ALKYL, As, BOND ROTATION, C-13, conformational analysis, dynamic, dynamic NMR, ENANTIOMERS, energy, groups, MM calculations, Molecular, MOLECULAR MECHANICS, NMR, Other, RANGE, RING INVERSION, Rotation, solid- state NMR, SPECTRA, spectroscopy, SPECTRUM, STATE, Structure, SYMMETRY, Temperature, TERM|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry|
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