We call iodabenzene a cyclic (CH)5I molecule. A planar iodabenzene would have 8 π electrons, a situation best avoided by an out-of-plane distortion to a bird-like geometry. The electronic structure and charge distribution of this molecule resemble those of Meisenheimer complexes, derivatives of (CH)5CH2 -. A similar substitution strategy, of π-acceptors in ortho and para positions, works in both cases to planarize and stabilize such derivatives. Some 40 kcal/mol (73 kcal/mol for the unsubstituted case) below the bird, a classical 5-iodocyclopentadiene structure awaits, reached through a bicyclic transition state. The calculated activation barrier for the highly exothermic reaction to a classical Lewis structure nevertheless make us optimistic about the chances of detecting and even isolating the bird isomer.

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Persistent URL dx.doi.org/10.1021/jacs.7b03388
Journal American Chemical Society Journal
Rawashdeh, A.M. (Abdel Monem), Chakkingal Parambil, P. (Priyakumari), Zeng, T, & Hoffmann, R. (Roald). (2017). An Iodabenzene Story. American Chemical Society Journal, 139(20), 7124–7129. doi:10.1021/jacs.7b03388