Towards Hexagonal Planar Nickel: A Dispersion-Stabilised Tri-Lithium Nickelate

Area of Science:

• Organometallic Chemistry
• Inorganic Chemistry

Background:

• Low-valent transition metals are crucial in catalysis.
• Organolithium ligands offer unique electronic and steric properties.
• Stabilizing highly reactive low-valent metal centers remains a challenge.

Purpose of the Study:

• To synthesize and characterize novel homoleptic organonickelate complexes.
• To investigate the nature of nickel-lithium bonding.
• To explore the role of ancillary ligands in stabilizing these complexes.

Main Methods:

• Synthesis of nickelate complexes via reaction of Ni(COD)2 and lithium aryl-acetylides with TMEDA.
• Solid-state structural analysis.
• Computational bonding analysis using QTAIM, NCI, NBO, and ELI methods.
• Preliminary reactivity studies including cross-coupling reactions.

Main Results:

• A family of homoleptic organonickelate complexes with hexagonal planar Ni(0) geometry was obtained.
• Nickel-lithium interactions were found to be repulsive, indicating tri-coordinated nickel centers.
• London dispersion forces involving TMEDA significantly stabilize the complexes.
• The nickelates undergo cross-coupling with iodobenzene to form dinickel clusters.

Conclusions:

• These complexes are rare examples of low-valent transition metals supported solely by organolithium ligands.
• The stabilization mechanism highlights the importance of non-covalent interactions.
• The reactivity demonstrates potential applications in synthesizing complex metal clusters.