Noncovalent Interactions in Compounds Based on Perchlorinated Boron Cluster as Monitored by 35Cl NQR (Review)

The article surveys the first Cl-35 NQR results on detecting and characterizing noncovalent interactions in systems assembling [B10Cl10](2-) clusters via halogen atoms. A number of compounds of decachloro-closo-decaborates with alkali metal or organic cations as well as with silver(I), copper(II) and iron(II) complexes were studied using Cl-35 NQR and X-ray diffraction. The main interest of this survey is a capability of chlorine atoms to participate in noncovalent interactions with organic cations, ligand and solvent molecules without touching upon issues of synthesis. Whereas X-ray diffraction establishes the noncovalent interactions relying on the sum of vdW radii which serves as the basic and sometimes the only experimental criterion for identifying such interactions, the Cl-35 NQR technique registers subtle perturbations in electron density distribution on the chlorine site caused by secondary interactions Cl center dot center dot center dot X. They adequately split the Cl-35 NQR spectra thus selecting from the entire set of interatomic contacts those actually induced by noncovalent interactions.