PHOTOELECTRON SPECTROSCOPIC MOLECULAR ORBITAL STUDY OF SF4 AND RELATED FLUOROSULFURANES

He(I) photoelectron spectra (UPS) are reported for SF4, CF3SF3, (CF3)2SF2, Me2NSF3, (Me2N)2SF2, F3SCF2SF3, and (CF3)2S. The UPS of SF4 was interpreted on the basis of SCF-Xαscattered-wave (XαSW) calculations in which the ionization energies (IEs) of all the valence molecular orbitals (MOs) were computed by the transition-state method. MNDO MO calculations have also been performed on SF4. The observation that the F(2p) π-type orbitals are ~2 eV more stable in the equatorial than in the axial sites is consistent with a previous X-ray photoelectron spectroscopic study of SF4. The UPS of the other fluorosulfuranes were interpreted using qualitative arguments and on the basis of empirical trends in the IEs. For all the fluorosulfuranes studied here a correlation was noted between the IE of the sulfur “lone-pair” MO and the sum of the group electronegativities of the equatorial substituents. A detailed discussion of the 7a1, 3b1, 4a1, 2b2, 2b1, and 3a1MOs of SF4is presented from the standpoint of the XαSW calculations. The HOMO (7a1) involves approximately equal charge densities on the sulfur atom and each of the axial fluorine (Fa) ligands. The 3b1MO features a modicum of bonding interaction between the axial and equatorial fluorine ligands. The orbital contour map for the 2b1MO is reminiscent of the hypervalent three-center, four-electron model for Fa-S-Fabonding. © 1979, American Chemical Society. All rights reserved.