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

Dipankar Sutradhar; Sumitra Bhattarai; Therese Zeegers-Huyskens; Asit K Chandra

doi:10.1021/acs.jpca.8b04495

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

J Phys Chem A. 2018 Sep 13;122(36):7142-7150. doi: 10.1021/acs.jpca.8b04495. Epub 2018 Aug 31.

Authors

Dipankar Sutradhar¹, Sumitra Bhattarai¹, Therese Zeegers-Huyskens², Asit K Chandra¹

Affiliations

¹ Department of Chemistry, Centre for Advanced Studies , North-Eastern Hill University , 793022 Shillong , India.
² Department of Chemistry , University of Leuven , B-3001 Heverlee , Belgium.

PMID: 30122037
DOI: 10.1021/acs.jpca.8b04495

Abstract

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 Å. 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 fluorinated sulfides. AIM analysis, the charge transfer from the sulfur atom to the Cl atom, and the spin densities on the Cl and S atoms are considered to explain this unusual behavior. The hyperconjugation energies from the LP(F) to the σ*(S-Cl) antibonding orbital can be considered as one of the stabilizing factors for the greater stability of the fluorinated complexes over the nonfluorinated ones.