The counterintuitive aromaticity of bent metallabenzenes: A theoretical exploration

Metallabenzenes, a type of aromatic compound that includes metal atoms, have opened up new avenues for creating materials with unique properties. A distinctive feature of metallabenzenes is the significant deviation of their metal atoms from the planar configuration of the C5 ring, a phenomenon that paradoxically enhances their aromatic character. In this investigation, we propose that this counterintuitive increase in aromaticity upon geometric distortion is governed by the interactions of frontier orbitals in the σ-space. This insight not only corroborates the previously suggested role of σ-space orbitals in inducing geometric non-planarity in metallabenzenes but also underscores their pivotal contribution to the compounds' enhanced aromaticity. As a result, this work broadens the scope of the σ-control mechanism, highlighting its usefulness for the rational design of functional metalla-aromatic materials.