In carbon dioxide utilization by cyclometalated five-membered ring products, the following compounds are used in
four types of applications:
1. 2-Phenylpyrazole iridium compounds, pincer phosphine iridium compounds and 2-phenylimidazoline iridium
compounds are used as catalysts for both formic acid production from CO2 and H2, and hydrogen production from
the formic acid. This formic acid can be a useful agent for H2 production and storage for fuel cell electric vehicles.
2. Other chemicals, e.g., dimethyl carbonate, methane, methanol and CO, are produced with dimethylaminomethylphenyltin
compounds, pincer phosphine iridium compounds, pincer phosphine nickel compound and ruthenium carbene compound or
2-phenylpyridine iridium compounds, and phenylbenzothiazole iridium compounds as the catalysts for the reactions with CO2.
3. The five-membered ring intermediates of cyclometalation reactions with the conventional substrates react with carbon dioxide to afford
their many types of carboxylic acid derivatives.
4. Carbon dioxide is easily immobilized at room temperature with immobilizing agents such as pincer phosphine nickel compounds, pincer
phosphine palladium compounds, pincer N,N-dimethylaminomethyltin compounds and tris(2-pyridylthio)methane zinc compounds.