Carbon Dioxide To Methanol Via Silanes

Chemists and chemical engineers are on the lookout for new ways to utilize the abundant CO₂ generated from burning fossil fuels as a feedstock to make commodity chemicals and fuels. Siti Nurhanna Riduan, Yugen Zhang, and Jackie Y. Ying of Singapore's Institute of Bioengineering & Nanotechnology report progress toward this goal by converting CO₂ to methanol via N-heterocyclic carbene catalysts (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200806058). The researchers combined CO₂ with different imidazolium-based carbenes and then added diphenylsilane as a hydrogen source; subsequently hydrolyzing each reaction mixture with water formed methanol, with better than 90% yield under optimized conditions. Hydrosilylation of CO₂ is not new, the researchers point out; others have used transition-metal catalysts to carry out the reaction in the past. But the Singapore team describes their reaction as the first to use N-heterocyclic carbene catalysts for hydrosilylation, and they say the carbenes are more efficient at hydrosilylation of CO₂ than previously reported transition-metal catalysts. The method offers a potentially economical, metal-free approach to CO₂ utilization, the researchers conclude, especially if the expensive silane is replaced with an alternative hydrogen source.