Synthesis and Characterization of Adducts between SF4 and Oxygen Bases: Examples of O···S(IV) Chalcogen Bonding

Lewis acid–base adducts between SF4 and the oxygen bases tetrahydrofuran, cyclopentanone, and 1,2-dimethoxyethane were synthesized and characterized by Raman spectroscopy and X-ray crystallography. Crystal structures of (SF4·OC4H8)2, SF4·(OC4H8)2, SF4·CH3OC2H4OCH3, and SF4·(OC5H8)2 show weak S···O chalcogen bonding interactions ranging from 2.662(2) to 2.8692(9) Å. Caffeine, which has three Lewis basic sites, was reacted with SF4 and one aliquot of HF forming C8H10N4O2·2SF4·HF, which was also characterized by X-ray crystallography. Density functional theory calculations aided in the assignment of the vibrational spectra of (SF4·OC4H8)2, SF4·(OC4H8)2, SF4·CH3OC2H4OCH3, and SF4·(OC5H8)2. Bonding was studied by natural bond order and the quantum theory of atoms in molecules analyses.