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

Lewis acid–base adducts between SF 4 and the oxygen bases tetrahydrofuran, cyclopentanone, and 1,2-dimethoxyethane were synthesized and characterized by Raman spectroscopy and X-ray crystallography. Crystal structures of (SF 4 ·OC 4 H 8 ) 2, SF 4 ·(OC 4 H 8 ) 2, SF 4 ·CH 3 OC 2 H 4 OCH 3, and SF 4 ·(O═C 5 H 8 ) 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 SF 4 and one aliquot of HF forming C 8 H 10 N 4 O 2 ·2SF 4 ·HF, which was also characterized by X-ray crystallography. Density functional theory calculations aided in the assignment of the vibrational spectra of (SF 4 ·OC 4 H 8 ) 2, SF 4 ·(OC 4 H 8 ) 2, SF 4 ·CH 3 OC 2 H 4 OCH 3, and SF 4 ·(O═C 5 H 8 ) 2 . Bonding was studied by natural bond order and the quantum theory of atoms in molecules analyses.