Electron Diffraction Study of the Molecular Structures of Sulfur Tetrafluoride (SF4) and Thionyl Tetrafluoride (SOF4)

Abstract

The molecular structures of SF₄ and SOF₄ in the gaseous state were determined by electron diffraction using sector‐microphotometer data. Both molecules were confirmed to have trigonal bipyramidal structures (C_2v symmetry), with two nonequivalent sets of F–S bond distances. The bond lengths, in terms of the center of gravity parameter, r_g, and the bond angles are as follows: $$\begin{array}{cc}{\mathrm{For\; SF}}_4:& r_g(\mathrm{equatorial\; S}–\mathrm{F}\text{)=1.542±0.005\hspace{0.17em}Å,}\\ & r_g(\mathrm{polar\; S}–\mathrm{F}\text{)=1.643±0.005\hspace{0.17em}Å,}\\ & \mathrm{\angle (}\mathrm{equatorial\; F}–\mathrm{S}–\mathrm{F}{\text{)=103.8}}^{\circ }{\text{±0.6}}^{\circ },\\ & \mathrm{\angle (}\mathrm{polar\; F}–\mathrm{S}–\mathrm{F}{\text{)=176.8}}^{\circ }{\text{±2.5}}^{\circ }.\\ {\mathrm{For\; SOF}}_4:& r_g(\mathrm{equatorial\; S}–\mathrm{F}\text{)=1.539±0.005\hspace{0.17em}Å,}\\ & r_g(\mathrm{polar\; S}–\mathrm{F}\text{)=1.602±0.005\hspace{0.17em}Å,}\\ & r_g(\mathrm{S}–\mathrm{O}\text{)=1.422±0.008\hspace{0.17em}Å,}\\ & \mathrm{\angle (}\mathrm{equatorial\; F}–\mathrm{S}–\mathrm{F}{\text{)=122.8}}^{\circ }{\text{±1.8}}^{\circ },\\ & \mathrm{\angle (}\mathrm{polar\; F}–\mathrm{S}–\mathrm{F}{\text{)=182.8}}^{\circ }{\text{±0.7}}^{\circ }.\end{array}$$ The polar F–S–F angles are measured along an arc which bisects the equatorial FSF angle.