Despite the long-standing use of transition metal complexation for stabilizing antiaromatic hydrocarbons, the underlying factors that govern their coordination behavior remain unclear. A Ni(0) complex, [Ni(cod)(1)], featuring a benzothiophene-S,S-dioxide-fused pentalene ligand, was synthesized and characterized, and compared to a benzothiophene-fused analogue, [Ni(cod)(2)], which bears a more antiaromatic yet less electron-accepting pentalene ligand. Single-crystal X-ray diffraction, X-ray absorption spectroscopy, and variable-temperature NMR, combined with computational analyses, reveal that the enhanced stability of [Ni(cod)(1)] arises primarily from substantial π-back-donation facilitated by strongly electron-withdrawing SO2 groups that lower the LUMO energy of 1. Comparisons to [Ni(cod)(2)] further demonstrate that a more antiaromatic core does not necessarily lead to stronger coordination to the Ni center. Surprisingly, the robust [Ni(cod)(1)] complex is fluxional in solution; the Ni center migrates reversibly between the two five-membered rings of the pentalene ligand via a bond shift mechanism.

Abstract. On the occasion of celebrating the 100th anniversary of the Bulletin of the Chemical Society of Japan (BCSJ), this Account summarizes major topic

Antiaromatic π-electron systems provide unique electronic features arising from the cyclic conjugation of 4n π-electrons, yet synthetic access to strongly antiaromatic heteroarene-fused scaffolds rema...

Antiaromatic π-electron systems provide unique electronic features arising from the cyclic conjugation of 4n π-electrons, yet synthetic access to strongly antiaromatic heteroarene-fused scaffolds rema...

Transition metal complexation has long served as a strategy for stabilizing antiaromatic hydrocarbons. However, the underlying factors that govern their coordination behavior are not yet fully underst...

Ortho-quinodimethane made under mild conditions from common reagents