Room-Temperature Gas-Phase CO₂-to-C₃ Coupling by a 4f-Aromatic Cluster

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Converting carbon dioxide (CO₂) into valuable multi-carbon products (C₃ or C₃₊) at room temperature is challenging due to low selectivity and limited carbon-carbon (C-C) coupling.
• Developing efficient catalysts for CO₂ activation and C-C bond formation is crucial for sustainable chemistry.

Purpose of the Study:

• To identify novel catalysts for room-temperature CO₂ conversion into multi-carbon products.
• To elucidate the mechanism of C-C coupling in CO₂ activation mediated by f-block elements.

Main Methods:

• Mass spectrometry
• Photoelectron imaging spectroscopy
• Density functional calculations

Main Results:

• Identification of the 4f-metalla-aromatic anion PrB₂C₂^- exhibiting double aromaticity.
• Demonstration of room-temperature reaction between PrB₂C₂^- and CO₂ to form C₃B₂O₂^- with a C-C-C backbone.
• Elucidation of a three-stage C₃-chain formation mechanism involving C-C coupling, flexible Pr-X bonding, and electron shuttling.

Conclusions:

• The unique structure of PrB₂C₂^- selectively activates CO₂ towards C-C-C coupling, avoiding CO release.
• This study provides insights into f-block-mediated small-molecule activation and a new route for synthesizing C-C bonded products from CO₂.