Single-Not Double-3D-Aromaticity in an Oxidized Closo Icosahedral Dodecaiodo-Dodecaborate Cluster

3D-aromatic molecules with (distorted) tetrahedral, octahedral, or spherical structures are much less common than typical 2D-aromatic species or even 2D-aromatic-in-3D systems. Closo boranes, [BnHn](2-) (5 = n = 14) and carboranes are examples of compounds that are singly 3D-aromatic, and we now explore if there are species that are doubly 3D-aromatic. The most widely known example of a species with double 2D-aromaticity is the hexaiodobenzene dication, [C6I6](2+). This species shows p-aromaticity in the benzene ring and s-aromaticity in the outer ring formed by the iodine substituents. Inspired by the hexaiodobenzene dication example, in this work, we explore the potential for double 3D-aromaticity in [B12I12](0/2+). Our results based on magnetic and electronic descriptors of aromaticity together with B-11{H-1} NMR experimental spectra of boron-iodinated o-carboranes suggest that these two oxidized forms of a closo icosahedral dodecaiodo-dodecaborate cluster, [B12I12] and [B12I12](2+), behave as doubly 3D-aromatic compounds. However, an evaluation of the energetic contribution of the potential double 3D-aromaticity through homodesmotic reactions shows that delocalization in the I-12 shell, in contrast to the 10s-electron I-6(2+) ring in the hexaiodobenzene dication, does not contribute to any stabilization of the system. Therefore, the [B12I12](0/2+) species cannot be considered as doubly 3D-aromatic.

Automated summary

3D-aromatic molecules are less common than 2D-aromatic species. This study explores the potential for double 3D-aromaticity in [B12I12] (0/2+), and the results indicate that it cannot be considered as doubly 3D-aromatic.