Salts based on perchlorinated closo-dodecaborate anion: First 35Cl NQR studies and crystal structure

Abstract

Three salts based on perchlorinated closo-dodecaborate anion, Cs2[B12Cl12]∗2MeCN (1), K2[B12Cl12]∗7MeCN (2), and (Ph4P)2[B12Cl12] (3) were synthesized and characterized using 11В, 1Н, 13С NMR, X-ray diffraction and 35Cl nuclear quadrupole resonsnce (NQR) spectroscopy. The latter was for the first time applied for identification of noncovalent interactions Cl⋯X in closo-dodecaborate clusters. Subtle perturbations of the cluster electron density caused by weak noncovalent Cl⋯X interactions were detected hence selecting from the whole totality of measured interatomic ​« ​short ​» ​contacts those which really participated in noncovalent interactions. It has been shown that X-ray structural information based on measuring the distances between atomic nuclei can be substantially supplemented with the 35Cl NQR data on the features of the electronic distribution in these compounds. According to the 35Cl NQR results, the alkali cations in 2∗7MeCN, unlike in 1∗2MeCN, do not participate in noncovalent interactions with Cl atoms whereas the X-ray diffraction analysis found a number of K⋯Cl distances shorter than the sum of vdW radii.