Single─Not Double─3D-Aromaticity in an Oxidized 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. boranes, [BH] (5 ≤ ≤ 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, [CI]. This species shows π-aromaticity in the benzene ring and σ-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 [BI]. Our results based on magnetic and electronic descriptors of aromaticity together with B{H} NMR experimental spectra of boron-iodinated -carboranes suggest that these two oxidized forms of a icosahedral dodecaiodo-dodecaborate cluster, [BI] and [BI], 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 shell, in contrast to the 10σ-electron I ring in the hexaiodobenzene dication, does not contribute to any stabilization of the system. Therefore, the [BI] species cannot be considered as doubly 3D-aromatic.