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A Persistent Ni(0)-Pentalene Complex with High Fluxionality: Does Stronger Antiaromaticity Promote Metal-Ligand
Riina Kuwata1, Takefumi Imanishi1, Shota Hasegawa2
1Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.
Journal of the American Chemical Society
|May 13, 2026
Summary
This study reveals that electron-withdrawing SO2 groups enhance nickel complex stability by promoting pi-back-donation. Surprisingly, the stable nickel complex exhibits fluxional behavior in solution, with the nickel center migrating between ligand rings.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Aromaticity Studies
Background:
- Transition metal complexation is used to stabilize antiaromatic hydrocarbons.
- Factors governing coordination behavior are not fully understood.
Purpose of the Study:
- Synthesize and characterize nickel(0) complexes with benzothiophene-fused pentalene ligands.
- Investigate factors influencing coordination stability and behavior.
- Compare complexes with varying antiaromaticity and electron-accepting properties.
Main Methods:
- Synthesis and characterization of nickel(0) complexes.
- Single-crystal X-ray diffraction.
- X-ray absorption spectroscopy.
- Variable-temperature Nuclear Magnetic Resonance (NMR) spectroscopy.
- Computational analyses.
Main Results:
- A stable nickel(0) complex [Ni(cod)(1)] with a benzothiophene-S,S-dioxide-fused pentalene ligand was synthesized.
- Enhanced stability of [Ni(cod)(1)] is attributed to π-back-donation from SO2 groups lowering the LUMO energy.
- A more antiaromatic core does not guarantee stronger coordination.
- The [Ni(cod)(1)] complex displays fluxional behavior in solution via a bond shift mechanism.
Conclusions:
- Electron-withdrawing SO2 groups significantly enhance the stability of nickel complexes with pentalene ligands.
- Antiaromaticity alone does not dictate coordination strength.
- Nickel complexes with these ligands can exhibit dynamic fluxional behavior in solution.
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