Charge Density of Intra‐ and Intermolecular Halogen Contacts

Abstract

Remarkably short contacts involving halogen atoms, although well documented decades ago, have recently found increasing interest as potentially relevant in the context of crystal engineering. X-ray diffraction data of sufficient quality and resolution allow to experimentally determine the charge density in crystals featuring such contacts and hence to associate this observable quantity with effects of molecular packing. Results from charge density studies covering interhalogen contacts over a distance range significantly shorter and considerably longer than mere van-der-Waals contacts are reported, and their relevance for the crystal chemistry of the compounds under investigation is discussed. A first trend for intra- and intermolecular Cl···Cl interactions indicates that the shortest among these contacts, with a distance of ca. 3.2 Å, can compete with weak hydrogen bonds

Insight into trifluoromethylation – experimental electron density for Togni reagent I

“…[23][24][25] Such advanced structure models based on aspherical scattering factors have also been applied in the study of halogen bonds. [26][27][28][29][30] In this contribution, we provide direct experimental information for the electronic situation in Togni reagent I, 1; in particular, we analyze the charge distribution around the hypervalent iodine atom.…”

The many flavours of halogen bonds – message from experimental electron density and Raman spectroscopy

“…Several among the latter ionic compounds formed crystals of only standard quality but others proved sufficient for an experimental electron-density study . Together with earlier results from our group (Wang et al, 2009(Wang et al, , 2012(Wang et al, , 2013) and those mentioned above (Bui et al, 2009;Hathwar et al, 2010), we can compile 18 examples of interchlorine contacts for which details of the experimental charge densities and properties of the bond critical points (bcps) are…”

Hydrogen-Bonded and Halogen-Bonded: Orthogonal Interactions for the Chloride Anion of a Pyrazolium Salt

“…We are not aware of experimental charge density studies on I···Cl halogen bonds and therefore cannot compare for I1···Cl1 to other structures of the same class but we have encountered similar values for the shortest Cl···Cl contacts investigated by high resolution X-ray diffraction [ 49 , 50 ]. Geometric and electronic parameters of the classical N–H···Cl hydrogen bond may be compared to the situation in bis(2-chloropyridinium) tetrachloridozincate; for the latter compound, the electron density was established experimentally [ 51 ].…”