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A Persistent Ni(0)–Pentalene Complex with High Fluxionality: Does Stronger Antiaromaticity Promote Metal–Ligand Interactions?R. Kuwata, T. Imanishi, S. Hasegawa, Z. Wang, J. Usuba, K. Yasui, M. U. G. Khan, J. I. Wu*, Y. Uetake*, and A. Fukazawa*ChemRxiv, 2025, Preprint.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 analog, [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.
@article{kuwata2025a, title = {A Persistent Ni(0)–Pentalene Complex with High Fluxionality: Does Stronger Antiaromaticity Promote Metal–Ligand Interactions?}, author = {Kuwata, R. and Imanishi, T. and Hasegawa, S. and Wang, Z. and Usuba, J. and Yasui, K. and Khan, M. U. G. and Wu, J. I. and Uetake, Y. and Fukazawa, A.}, journal = {ChemRxiv}, year = {2025}, pages = {Preprint}, month = nov, doi = {10.26434/chemrxiv-2025-l8c87-v2}, url = {https://doi.org/10.26434/chemrxiv-2025-l8c87-v2}, dimensions = {true}, tab = {paper} }