Probing the Aromaticity of Bi(metallacycloprop‐1‐ene) with Different Metals and Ligands

Abstract In recent years, there has been a growing interest in the field of adaptive aromaticity, which refers to compounds that demonstrate aromaticity in both lowest singlet and triplet states. Our previous investigation revealed the σ aromaticity of metallacycles within spiro bi(metallacycloprop‐1‐ene) units at its lowest singlet state. This ongoing interest has prompted us to delve deeper into the aromaticity of a varied assortment of bi(metallacycloprop‐1‐ene) compounds, characterized by distinct metal centers and ligands. In pursuit of this, DFT calculations have been conducted. Computational analyses show that the metallocyclic propene units in the bi(metallacycloprop‐1‐ene) M.X ( M = Re 2− , Os − , Ir / X = F , Cl , Br ) are σ adaptive aromatic, except for Ir.X , which is aromatic only in the lowest singlet state.