S···π Chalcogen Bonds between SF2 or SF4 and C-C Multiple Bonds

Area of Science:

• Computational Chemistry
• Noncovalent Interactions
• Supramolecular Chemistry

Background:

• Chalcogen bonds are analogous to hydrogen bonds, involving a chalcogen atom acting as an electrophile.
• Sulfur halides like SF2 and SF4 possess potential for forming such interactions due to sulfur's electron configuration.

Purpose of the Study:

• To investigate the formation and characteristics of chalcogen bonds between SF2/SF4 and unsaturated hydrocarbons.
• To elucidate the binding energies, geometries, and electronic factors governing these noncovalent interactions.

Main Methods:

• Utilized MP2 ab initio calculations to model interactions between SF2/SF4 and ethene, ethyne, 1,3-butadiene, and benzene.
• Analyzed binding energies, bond lengths, and charge transfer pathways.

Main Results:

• Chalcogen bonds formed between the sulfur atom and the π-system of hydrocarbons, with sulfur positioned above a C=C bond.
• Binding energies ranged from 3.3 to 6.6 kcal/mol; SF2 formed stronger bonds than SF4, except with benzene.
• Shortest chalcogen bonds were observed in cis-butadiene complexes, and S-F bonds elongated upon complexation.

Conclusions:

• Charge transfer from the π-bonds to SFx σ*(SF) antibonding orbitals is the primary driving force for these interactions.
• SF2's sulfur lone pair facilitates stronger charge transfer compared to SF4 in most systems studied.
• The findings provide insights into the nature of chalcogen bonding involving sulfur-containing molecules.