Storing redox equivalent in the phenalenyl backbone towards catalytic multi-electron reduction

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Multi-electron reduction is crucial for chemical and biological transformations.
• Efficient electron storage and transfer are key challenges in catalysis.

Purpose of the Study:

• To achieve multi-electron reduction of carboxylic acids via a hydrosilylation pathway.
• To elucidate the role of a redox-active ligand in storing electrons and hydride equivalents.

Main Methods:

• Utilized a cobalt complex with a redox-active phenalenyl backbone, Co(PLY-O,O)2(THF)2.
• Investigated the catalytic reduction pathway, including single electron transfer (SET).
• Isolated and characterized key reaction intermediates and employed deuterium labeling experiments.

Main Results:

• Successfully accomplished multi-electron reduction of a carboxylic acid.
• Demonstrated that the phenalenyl ligand backbone stores electrons and hydride equivalents.
• Proved storage of redox equivalents in a C-H bond of the PLY backbone via ligand dearomatization.

Conclusions:

• The redox-active phenalenyl ligand plays a central role in orchestrating the multi-electron reduction.
• This work presents a rare example of a ligand actively participating in redox processes beyond metal coordination.
• The metal center fine-tunes catalyst electronics and maintains structural integrity.