Activation of Hydrogen by Sterically Modulated Coinage Metal Catalysts via Mutual Quenching of Hard/Soft Acid/Base Mismatches

To mitigate the devastating environmental impacts of climate change in the coming decades, it is imperative that we replace the use of fossil fuels with renewable energy sources such as wind, solar, and hydroelectric. As these renewable energy sources are inherently intermittent, there exists a need for sustainable mechanisms to store renewable energy for later use. While the direct use of dihydrogen (H2) as a combustible fuel would allow for energy storage without the harmful release of carbon dioxide (CO2) upon combustion, the practicality of H2 as a synthetic fuel is limited by its low volumetric energy density. Combining sustainable H2 production (e.g. electrolysis using energy from renewable sources) with subsequent carbon fixation (e.g. the hydrogenation of CO2) represents a promising pathway to the sustainable production of high-density synthetic fuels. We hypothesize that such a process could be catalyzed by an IPr**-supported catalyst containing a hard/soft acid/base (HSAB) mismatch, with a polarizable coinage metal acting as a soft acid. As such, the aim of our project is the construction of a catalogue of IPr**-supported copper, silver, and gold catalysts that we anticipate will facilitate the heterolysis of dihydrogen and subsequent hydrogenation of CO2. In the present paper, we report the synthesis and characterization of an IPr**-silver complex which will serve as a precursor to many of our proposed HSAB mismatch catalysts and discuss next steps as we construct our catalogue of catalysts.