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

[Image: see text] 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, [B(n)H(n)](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, [C(6)I(6)](2+). 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 [B(12)I(12)](0/2+). Our results based on magnetic and electronic descriptors of aromaticity together with (11)B{(1)H} NMR experimental spectra of boron-iodinated o-carboranes suggest that these two oxidized forms of a closo icosahedral dodecaiodo-dodecaborate cluster, [B(12)I(12)] and [B(12)I(12)](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 10σ-electron I(6)(2+) ring in the hexaiodobenzene dication, does not contribute to any stabilization of the system. Therefore, the [B(12)I(12)](0/2+) species cannot be considered as doubly 3D-aromatic.