d Orbitals in Compounds of Second-Row Elements. I. SF6

Abstract

Selfconsistent molecular orbital methods. XXIII. A polarizationtype basis set for secondrow elementsOptimum exponent values for 3s, 3p, and 3d orbitals of sulfur in SF6 have been calculated in an electrostatic approximation. The sulfur electrons are perturbed by fluorine potentials appropriate to self-consistent field wave functions for the fluorine orbitals, and the energy minimized with respect to wave-function exponents. The optimum values are ka,= 2.0, kap= 1.6, and kad= 1.2, corresponding to expansion of 3s and 3p orbitals, and contraction of 3d, compared with free-atom values. The values are remarkably stable to changes in valence-orbital configurations as between SF6, S+F6-, S++F6-, and even S-F 6 +. They are also little affected by change in hybridization at fluorine, and should therefore be suitable for use in the construction of molecular wave functions.Although the calculated energies include no exchange terms they are still of some interest. They suggest for example that the promotion energy to the configuration sp3rJlof sulfur (estimated to be 25-31 eV) can be compensated by the energy of molecule formation.

Sulfonyl Chloride Kinetics. Part II. Solvolysis of a Series of Benzenesulfonyl Chlorides: An Unexpected Heat Capacity Variation

“…Similar conclusions can be drawn from data for S02F2 (25). From the above evidence we conclude that the stereochemistry of the RS02CI molecules may be considered as a distorted tetrahedron but with shortened S-0 bonds due to pn-dn interaction (26). The question of importance here is how this initial state structure will alter in the pre-/liminary activation and how the resulting activated molecule will influence the approach of the displacing nucleophile.…”

Ab initio calculations, using a small Gaussian basis set, of the electronic structure of the sulphate ion

“…Semi-empirical molecular orbital calculations of varying degrees of complexity [ 1-41 have been inconclusive in their discussion of the bonding in these molecules and have highlighted the problems of the size of the sulphur 3d orbital and the suitable parameters to use in such calculations. Atomic SCF calculations of various configurations of the sulphur atom [5] have shown that d orbitals may be of suitable size for engaging in molecular bonding, and it has been suggested [6] that participation of d orbitals in bonding should be possible if their energies are substantially lowered by ligands.…”

“…When sulphur is bonded to more electronegative elements such as oxygen, it has been suggested [6] that the larger formal charge on the sulphur atom may lead to atomic 3d orbitals of sufficiently low energy to be important in bonding. One such system which has been the subject of a number of semi-empirical studies is the sulphate dinegative ion.…”

On partitioning the overlap charge density in self‐consistent charge molecular‐orbital calculations

“…were taken from Clementi [ll], except for the 3d suIfur orbital which was taken to have an orbital exponent of 1.2 [12], and the manganese 4p orbital, which was taken from Oleari and coworkers [ 131.…”

“…The basis sets consisted of 2s and 2p orbitals on oxygen, 3d, 4s, and 4p orbitals on manganese and 3s, 3p, and 3d orbitals on sulfur. Atomic orbitals for the 3P state of sulfur, 3P state of oxygen, and 6S state of manganese were taken from Clementi [ll], except for the 3d suIfur orbital which was taken to have an orbital exponent of 1.2 [12], and the manganese 4p orbital, which was taken from Oleari and coworkers [ 131.…”