Unusual Fluorine Substitution Effect on S···Cl Bonding between Sulfides and Atomic Chlorine

A theoretical investigation on the interaction of various sulfides and their fluorinated counterparts (H2S, HSF, F2S, CH3SH, CH3SF, CH2FSH, CH2FSF, NH2SH, NH2SF) with atomic chlorine has been carried out using density functional theory (DFT) based LC-BLYP/aug-cc-pVTZ and sophisticated ab initio CCSD(T)/aug-cc-pVQZ methods. The present study is intended to discuss the influence of the substituents implanted at the sulfur atom on the bonding parameters. The optimized geometries reveal that intermolecular S···Cl distances are short and range between 2.423 and 2.561 A. A strong contraction of the S–F bond is also predicted. Two-center–three-electron S···Cl bonds are formed; the interaction energies are large and range from −33.9 to −70.1 kJ mol–1. Very surprisingly, the interaction energies are greater and the intermolecular distances are shorter for F-substituted sulfides than for unsubstituted ones. This is in complete contrast with the lower proton affinities and less negative electrostatic potentials of f...