Menshutkin's {(Arene)·nSbX3} Molecular CompoundsExploring the Correlation between Crystal Structures and Nuclear Quadrupole Resonance Spectra

Abstract

By use of data from the literature to assign 35Cl, 81Br, 121Sb, and 123Sb nuclear quadrupole resonance (NQR) frequencies to particular atoms, an attempt is made to correlate crystal structures of a number of {(arene)·nSbX3} (X = Cl, Br) Menshutkin molecular compounds with their NQR spectra. Comparing NQR spectra of crystalline neat SbX3 (X = Cl, Br) with those of the molecular compounds shows well-established effects due to the perturbations introduced by changes in the detailed structures of the networks of SbX3 moieties and in the interactions of Sb atoms with the arene moieties. NQR spectra are much more sensitive in this regard than the changes in interatomic distances that are among the main quantitative outcomes of crystal structure analysis. Although a qualitative pattern can be discerned that associates the frequency of the 35Cl NQR spectra with the different structural roles of the crystallographically independent chlorines, it has not been possible to identify particular interactions with the differences found in the NQR frequencies. Generalizations based on NQR spectra do not appear currently achievable, and it seems likely that the spectra of the various molecular compounds will require explanation on an individual basis.