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Cooperative Reactivity Induced by All-Gallium Coordination at Nickel
Johannes Stephan1,2, Raphael Bühler1,2, Fabrizio E Napoli1,2
1Chair of Inorganic and Metal-Organic Chemistry, Department of Chemistry, TUM School of Natural Sciences, Technical University of Munich, Lichtenbergstraße 4, D-85748 Garching, Germany.
Inorganic Chemistry
|July 18, 2025
Summary
Researchers report a novel nickel/gallium complex that dimerizes acetonitrile, forming a unique ligand. This reaction showcases unusual reactivity and a large kinetic isotope effect, suggesting proton tunneling is involved in this mixed-metal catalysis.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Coordination Chemistry
Background:
- Mixed-metal complexes exhibit synergistic effects, enabling small-molecule activation and novel reactivity.
- Nickel and gallium complexes are of interest due to their diverse catalytic properties.
Purpose of the Study:
- To investigate the reactivity of a nickel/gallium complex fragment, specifically [Ni(GaCp*)4]2+.
- To explore the potential for small-molecule activation and ligand formation at this unique metal center.
Main Methods:
- Synthesis and characterization of the nickel/gallium complex.
- Reaction studies involving acetonitrile as a substrate.
- Density Functional Theory (DFT) calculations to elucidate the reaction mechanism.
Main Results:
- The nickel/gallium complex successfully dimerized acetonitrile to form a nacnac-type β-diketiminate ligand.
- The GaCp* ligand exhibited Lewis acidity, facilitating bond activation at the gallium center.
- A large kinetic isotope effect (KIE) of 28 was observed, indicating significant proton tunneling.
Conclusions:
- The proximity of nickel and gallium, along with a Ga-rich coordination sphere, is crucial for the observed reactivity.
- The study demonstrates an "umpolung" reactivity at the gallium center, acting as an electrophilic site for bond activation.
- The significant KIE highlights the importance of quantum mechanical effects, specifically proton tunneling, in this catalytic process.
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