TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Kirpichenko, Svetlana V.
A1  - Ushakov, Igor A.
A1  - Shainyan, Bagrat A.
T1  - Conformational analysis of 3-methyl-3-silathiane and 3-fluoro-3-methyl-3-silathiane
N2  - The conformational equilibria of 3-methyl-3-silathiane 5, 3-fluoro-3-methyl-3-silathiane 6 and 1-fluoro-1- methyl-1-silacyclohexane 7 have been studied using low temperature 13C NMR spectroscopy and theoretical calculations. The conformer ratio at 103;K was measured to be about 5ax:5eq;=;15:85, 6ax:6eq;=;50:50 and 7ax:7eq;=;25:75. The equatorial preference of the methyl group in 5 (0.35;kcal;mol;1) is much less than in 3-methylthiane 9 (1.40;kcal;mol;1) but somewhat greater than in 1-methyl-1- silacyclohexane 1 (0.23;kcal;mol;1). Compounds 5-7 have low barriers to ring inversion: 5.65 (ax;;;eq) and 6.0 (eq;;;ax) kcal mol;1 (5), 4.6 (6), 5.1 (Meax;;;Meeq) and 5.4 (Meeq;;;Meax) kcal;mol;1 (7). Steric effects cannot explain the observed conformational preferences, like equal population of the two conformers of 6, or different conformer ratio for 5 and 7. Actually, by employing the NBO analysis, in particular, considering the second order perturbation energies, vicinal stereoelectronic interactions between the Si-X and adjacent C-H, C-S, and C-C bonds proved responsible.
Y1  - 2011
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/33963
SN  - 0894-3230
ER  -