Molecular Structures of 5-Thiabicyclo[2.1.1]hexane and 7-Thianorbornane as Studied by Gas Electron Diffraction

Abstract

Abstract Molecular structures of 5-thiabicyclo[2.1.1]hexane and 7-thianorbornane (7-thiabicyclo[2.2.1]heptane) were studied by gas electron diffraction. For 7-thianorbornane the rotational constants obtained by Hirota et al. by microwave spectroscopy were also taken into account. Least-squares analyses gave the following rg bond distances and valence angles (rα for 5-thiabicyclo[2.1.1]hexane and rav for 7-thianorbornane): for 5-thiabicyclo[2.1.1]hexane, (C1–C2, C2–C3)av=1.539±0.016 Å, C1–C6=1.564±0.024 Å, C–S=1.865±0.004 Å, (C–H)av=1.110±0.008 Å, ∠C–S–C=69.5±0.6 ° and the dihedral angles (C1SC4)-(C1C2C3C4)=115.2±1.7° and (C1C6C4)-(C1C2C3C4)=116.1±2.4°; for 7-thianorbornane, C1–C2=1.538±0.006 Å, C2–C3=1.561±0.015 Å, C–S=1.837±0.004 Å, (C–H)av=1.115±0.008 Å, ∠C–S–C=80.2±0.8 °, the dihedral angle (C1C2C3C4)-(C4C5C6C1)=115.0±1.2° and ∠C1H–C–H=106±5°. The uncertainties represent the estimated limits of experimental error. The C–S bond length in 5-thiabicyclo[2.1.1]hexane is longer than that in dimethyl sulfide by 0.06 Å and that in 7-thianorbornane by 0.03 Å. The C–S–C angle in 5-thiabicyclo[2.1.1]hexane is smaller than that in dimethyl sulfide by about 30° and that in 7-thianorbornane by about 11°. The C1–C6 bond in 5-thiabicyclo[2.1.1]hexane is longer than the weighted average of the C1–C2 and C2–C3 bond lengths. The C1–C2 bond in 7-thianorbornane is longer than the C2–C3 bond.