Synthesis,conformational preferences in gas and solution,and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations |
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Authors: | Bagrat A Shainyan Elena N Suslova Tran Dinh Phien Sergey A Shlykov Erich Kleinpeter |
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Institution: | 1. A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Division of the Russian Academy of Sciences, 1 Favorsky Street, 664033 Irkutsk, Russian Federation;2. Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang, Viet Nam;3. Department of Chemistry and Environment, Vietnam-Russian Tropical Centre, 63 Nguyen Van Huyen, Cau Giay District, Ha Noi, Viet Nam;4. Ivanovo State University of Chemistry and Technology, Research Institute for Thermodynamics and Kinetics of Chemical Processes, 7 Sheremetievskiy Ave, 153000, Ivanovo, Russian Federation;5. Chemisches Institut der Universität Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam (Golm), Germany |
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Abstract: | 1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature 13C NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Phax conformer (1-Pheq:1-Phax ratio of 20:80%, ΔG°(317?K)?=??0.87?kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of Cipso and C(1,5) carbon signals in 13C NMR spectra at 103?K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2?=?1:1:3), which is still liquid at 100?K, the 1-Pheq conformer was found to be the preferred one (1-Pheq: 1-Phax?=?77%: 23%, K?=?77/23?=?2.8; ?ΔG°?=??RT ln K (at 103?K)?=?0.44?±?0.1?kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X?=?H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Phax conformer in the gas phase and of the Pheq conformer in solution is confirmed. |
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Keywords: | 1-(Dimethylamino)-1-phenyl-1-silacyclohexane Conformational analysis Gas phase electron diffraction Low-temperature d-NMR DFT MP2 M062X/6-311G** calculations |
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