Short Sb···Sb Contacts in Polymorphic Tris( p‐ Tolyl)Antimony: A Hallmark of Organoantimony(III) Solid‐State Chemistry?

ABSTRACT

Discovery of a polymorph of tris( p‐ tolyl)antimony(III) reveals solid‐state supramolecular dimers connected through short, attractive Sb∙∙∙Sb contacts that, based on theoretical calculations and a systematic screen of the Cambridge Structural Database (CSD), could be an overlooked hallmark of the solid‐state and supramolecular chemistry of trivalent organoantimony(III) compounds. While the previously reported crystal structure of tris( p‐ tolyl)antimony(III) is known to exhibit phenyl embrace motifs, resembling the arsenic or phosphorus analogs, the new polymorph exhibits supramolecular dimers characterized by direct Sb∙∙∙Sb contacts shorter than the sum of the van der Waals radii, and stabilized by a significant dimer dissociation energy of ca. −26 kJ mol ⁻¹ established by periodic density‐functional calculations. Theoretical analysis indicates that the contacts are attractive and dispersion‐dominated, with an overview of the CSD showing that such direct Sb···Sb contacts are not unique to this polymorphic form of tris( p‐ tolyl)antimony(III) but appear to be a more general feature of trivalent organoantimony in the solid state. Specifically, the CSD shows that dimers based on short Sb···Sb contacts are found across a number of organoantimony structures, including some of the simplest representatives of the series, such as triphenyl‐ and trimethylantimony, for which the dimer interaction energy is herein calculated to be ca. −13 kJ mol ⁻¹ .