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

Abstract

New salts containing bulky decachloro-closo-decaborate dianion of composition M2[B10Cl10] (M=K+ and Cs+) were synthesized and characterized using the IR, 11B NMR and 35Cl NQR spectroscopies, powder and single crystal X-ray diffractions. The potassium salt was obtained as solvate K2[B10Cl10]·3H2O, and cesium salt – as solvates Cs2[B10Cl10]·H2O and Cs2[B10Cl10]·2H2O. Using 35Cl NQR, the interatomic contacts, caused by secondary interactions, were selected of all the totality of interatomic contacts, measured by X-ray diffraction. The B–Cl…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 35Cl NQR spectra due to the alkali cations.