Bonding features in Appel's salt from the orbital-free quantum crystallographic perspective
Екатерина В. Барташевич, A.I. Stash, Irina D. Yushina, Mikhail E. Minyaev, Oleg Bol’shakov, Олег А. Ракитин, Vladimir G. Tsirelson
Abstract
Bonding properties in the crystal of 4,5-dichloro-l,2,3-dithiazolium chloride (Appel's salt) were studied using a combination of single-crystal high-resolution X-ray diffraction data and the orbital-free quantum crystallography approach. A QTAIM-based topological model shows the proximity of S—C and S—N bonds to the sesquialteral type and establishes the low S—S bond order in the l,2,3-dithiazolium heterocycle. It is found that the electrostatic potential carries the traces of a common positive area on the junction of interatomic zero-flux surfaces of S1 and S2 atomic basins; meanwhile the exchange energy density per particle shows perfectly here two separate minima through which the two bond paths run. Thus, the pair intermolecular interactions Cl − ...S1 and Cl − ...S2 formed by the common chloride anion placed near the center of the S—S bond are categorized as chalcogen bonds.