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Electron diffraction study of the molecular structure of gaseous 1,1-dibromo-3,3,5,5-tetramethyl-1-stanna-3,5-disila-4-oxacyclohexane,Br2Sn(CH2SiMe2)2O
Authors:A V Belyakov  A V Golubinskii  L V Vilkov  V I Shiryaev  E M Styopina  E A Kovalyova  V S Nikitin
Institution:(1) Institute of Technology, 198019 St. Petersburg, Russian Federation;(2) Chemical Department of M. V. Lomonosov, Moscow State University, Leninskie Gory, 119899 Moscow, Russian Federation;(3) State Research Institute of Chemistry and Technology of Organoelement Compounds, 38 sh. Enthusiastov, 111123 Moscow, Russian Federation
Abstract:The molecular structure of gaseous Br2Sn(CH2SiMe2)2O was studied by electron diffraction. The six-membered ring has a chair conformation whereas the entire molecule possessesC s symmetry. The existence of a boat conformer cannot be completely excluded. The results of theoretical calculations for a twisted-boat conformation are at variance with the experimental data. Steric strain caused by mutual repulsion of the two axial methyl groups is reduced to the tilt of the Me2Si fragments in opposite directions. This results in an increase (up to 26°C) in the angle formed by the bisector of the CM-Si-CM angle with the CcSiO plane. The main geometrical parameters are as follows:r g (Å): Si-O 1.708(20); Si-CM 1.862(20); Si-Cc 1.882(9); Sn-C 2.108(26); Sn-Br 2.456(3); C-H 1.099(30); gammaagr (degr.): C-Sn-C 105(2); Br-Sn-Br 107.9(1.2); Si-O-Si 129.6(3); CM-Si-CM 112; Si-C-H 113 (fixed value in accordance with experiment); Cc-Si-O 107(2); Sn-C-Si 109(2); torsion angles: phiv(Si-C) 52(2); phiv(Si-O) 62(1); phiv(Cc-Sn) 54(1). The average amplitudes were fixed at the values calculated from the force field. Structural parameters of molecules with similar structures were analyzed and compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 384–387, February, 1993.
Keywords:1  1-dibromo-3  3  5  5-tetramethyl-1-stanna-3  5-disila-4-oxacyclohexane  structure  gas phase electron diffraction
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