Carbon dioxide can be utilized as a means of storing hydrogen with an appropriate catalyst. The hydrogenation of carbon dioxide in the presence of base leads to formate. The reverse reaction, formic acid dehydrogenation, releases hydrogen. We have synthesized new bidentate ligands using pyridinol and NHC rings. The bidentate ligands have been used to form iridium catalysts, e.g. [Cp*Ir(6,6'-dhbp)Cl]Cl where 6,6'-dhbp = 6,6'-dihydroxybipyridine, that are highly active for CO2 hydrogenation. Ruthenium catalysts, e.g. [cymeneRu(6,6'-dhbp)Cl]Cl, are also highly active. A recently discovered feature of these reactions is that they require a Lewis acid co-catalyst for maximal rate enhancements. Our studies suggest that the Lewis acid binds to the oxyanion of deprotonated 6,6'-dhbp ligands. Very recent studies have shown that by modifying the Lewis acid, we can enhance a wide range of hydrogenation and dehydrogenation reactions with substrates other than CO2. We are also working on applying these concepts to the use of new pyridinol based ligands and earth abundant metal catalysts using late first row transition metals.

Pyridinol based ligands for transition metal catalyzed reduction of CO2 and related substrates: Elucidating the role of Lewis Acids

253rd National Meeting (2017)

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