Dinickel Active Sites Supported by Redox-Active Ligands

Area of Science:

• Organometallic Chemistry
• Catalysis
• Materials Science

Background:

• Multinuclear active sites in enzymes and heterogeneous catalysts are common, but rare in homogeneous catalysis.
• Single metal systems dominate organometallic chemistry, limiting exploration of cooperative effects.
• Metal-metal covalent bonding offers unique electronic configurations impacting substrate binding and reactivity.

Purpose of the Study:

• To explore the use of binucleating redox-active ligands for stabilizing multinuclear active sites.
• To investigate dinickel complexes supported by naphthyridine-diimine (NDI) ligands for catalytic applications.
• To demonstrate how cooperative effects in dinickel systems can solve problems intractable for monometallic catalysts.

Main Methods:

• Synthesis and characterization of dinickel complexes featuring redox-active NDI ligands.
• Evaluation of catalytic activity in reactions involving two-electron redox processes.
• Investigation of substrate activation and bond cleavage through cooperative dinickel action.

Main Results:

• Dinickel NDI complexes promote two-electron redox processes with metals remaining in a Ni(I)-Ni(I) state.
• Catalysts effectively dimerize aryl azides, avoiding product inhibition seen in mononickel systems.
• Dinickel complexes activate strong bonds, such as the C-C bond in norbornadiene, via cooperative oxidative addition.

Conclusions:

• Metal-metal bonding in dinickel complexes enables challenging catalytic steps and modulates reaction thermodynamics.
• The (NDI)Ni2 system provides a robust platform for exploring cooperative effects in catalysis.
• Further exploration with different transition metals and ligand classes is expected to yield new catalytic discoveries.