Electroreductive Synthesis of Nickel(0) Complexes

Area of Science:

• Organometallic Chemistry
• Catalysis
• Electrochemistry

Background:

• Nickel catalysts are crucial for organic transformations, with Ni(0) sources being effective precatalysts.
• Traditional synthesis of Ni(0) precatalysts relies on pyrophoric aluminum-hydride reductants, posing safety and atom-economy challenges.
• Existing methods often lack reproducibility and require cryogenic temperatures.

Purpose of the Study:

• To develop a scalable, reproducible, and safer method for synthesizing low-valent nickel precatalysts.
• To establish an electrochemical route for generating Ni(0) complexes from readily available Ni(II) salts.
• To facilitate the broader application of nickel catalysis in organic synthesis.

Main Methods:

• Preparative scale reduction of Ni(II) salts using electrolysis.
• Standardization of the electrochemical procedure for robustness and reproducibility.
• Development of an electrochemical recirculating flow process for large-scale synthesis.
• Implementation of an in situ reduction protocol for generating catalytic Ni(0).

Main Results:

• Successful synthesis of various Ni(0) and Ni(II) complexes, including bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2].
• Demonstration of a robust and reproducible electrochemical method for Ni(0) precatalyst preparation.
• Scalability of the method via an electrochemical recirculating flow process.
• Viability of in situ generation of Ni(0) for catalytic applications.

Conclusions:

• Electrochemical reduction provides a superior alternative to traditional methods for synthesizing Ni(0) precatalysts.
• This approach enhances safety, reproducibility, and scalability in organometallic complex preparation.
• The developed method is expected to accelerate the adoption of electrochemistry for synthesizing low-valent nickel complexes in research and industry.