Insights into the electronic structure of disulfur tetrafluoride isomers from generalized valence bond theory

Sulfur and fluorine can participate in a variety of bonding motifs, lending significant diversity to their chemistry. Prior work has identified three distinct minima for disulfur tetrafluoride (S₂F₄) compounds: two FSSF₃ isomers and one SSF₄ species. We used a combination of sophisticated explicitly correlated coupled cluster calculations and generalized valence bond (GVB) theory to characterize the electronic structure of these species as well as additional stationary points on the potential energy surface with F₂SSF₂ connectivity. On the singlet surface, the two stationary points considered in this work with an F₂SSF₂ structure are first- or second-order saddle points and not minima. However, on the triplet surface, we discovered a novel C₂ symmetric F₂SSF₂ minimum that was anticipated from the structure of an excited state (³B₁) of SF₂. Analysis using the GVB wave function in conjunction with the recoupled pair bonding model developed by our group provides a straightforward explanation of the bonding in all of the S₂F₄ structures considered here. In addition, the model predicted the existence of the F₂SSF₂(³B) minimum.