Noncovalent interactions in perchlorinated sulfonium and ammonium derivatives of closo-decaborate anion: 35Cl NQR and crystal structure

Abstract

Three salts of perchlorinated sulfonium and ammonium derivatives of tetrabuthylammonium nonachloro-closo-decaborate, (n-Bu4N)2[2-B10Cl9-cyclo-S(CH2)4S-B10Cl9] (1), (n-Bu4N)[2-B10Cl9-cyclo-S(C2H4)2O] (2) and (n-Bu4N)[1-B10Cl9N(n-Pr3)] (3) are synthesized and characterized using IR, 11B, 1H, 13C NMR, X-Ray and 35Cl NQR-spectroscopy. The noncovalent interactions involving chlorine atoms were identified by 35Cl NQR spectra. The results were discussed in comparison with those of X-ray diffraction analysis which are based on measuring contacts shorter than the sum of van der Waals (vdW) radii of atoms. It has been found that the crystal lattice of 2 exhibits dynamic properties strongly different from those of 1 and 3. Whereas the 35Cl NQR spectra of the latters were extremely wide (up to 1200 kHz), the spectrum of 2 demonstrated a narrowing of almost an order of magnitude (up to 120 kHz) which indicated a significant weakening of the tendency for the formation of intermolecular bonds by chlorine atoms of this cluster.