Ruthenium-Catalyzed Reduction of Carbon Dioxide to Formaldehyde

Abstract

Functionalization of CO₂ is a challenging goal and precedents exist for the generation of HCOOH, CO, CH₃OH, and CH₄ in mild conditions. In this series, CH₂O, a very reactive molecule, remains an elementary C₁ building block to be observed. Herein we report the direct observation of free formaldehyde from the borane reduction of CO₂ catalyzed by a polyhydride ruthenium complex. Guided by mechanistic studies, we disclose the selective trapping of formaldehyde by in situ condensation with a primary amine into the corresponding imine in very mild conditions. Subsequent hydrolysis into amine and a formalin solution demonstrates for the first time that CO₂ can be used as a C₁ feedstock to produce formaldehyde