Secondary interactions in decachloro-closo-decaborates of alkali metals M2[B10Cl10] (M = K+ and Cs+): 35Cl NQR and X-ray studies

New salts containing bulky decachloro-doso-decaborate dianion of composition M-2[B10Cl10] (M = K+ and Cs+) were synthesized and characterized using the IR, B-11 NMR and Cl-35 NQR spectroscopies, powder and single crystal X-ray diffractions. The potassium salt was obtained as solvate K-2[B10Cl10]center dot 3H(2)0, and cesium salt as solvates Cs-2[B10Cl10]center dot H2O and Cs2[B10Cl10]center dot 2H20. Using Cl-35 NQR, the interatomic contacts, caused by secondary interactions, were selected of all the totality of interatomic contacts, measured by X-ray diffraction. The B-CI center dot center dot center dot H secondary bonds were identified in all the compounds, whereas no contributions to the electric field gradient on the appropriate chlorine atoms were registered from cations M (M = K or Cs). The high coordination numbers of alkali ions screened the effective positive charge on them leading to insignificant perturbation of the chlorine electron density distribution which resulted in negligibly small splitting of the Cl-35 NQR spectra due to the alkali cations. (C) 2016 Elsevier Ltd. All rights reserved.