Cobalt Catalyzed Hydrogen Evolution
Authors:Stephanie Laga, Smaranda Marinescu
Mentor:Harry Gray, Arnold O. Beckman Professor of Chemistry, California Institute of Technology
Hydrogen production through the reduction of water has emerged as an important strategy for the storage of renewable energy in chemical bonds. Hydrogenase enzymes that contain iron and nickel cofactors evolve hydrogen catalytically from water near the thermodynamic potential. However, the large size and relative instability of these enzymes under aerobic conditions has led to the development of well-defined molecular catalysts that can produce hydrogen in a non-biological system. Synthetic cobalt complexes are being investigated as catalysts for the production of hydrogen from acidic solutions. The targeted cobalt complexes are supported by a triphos ligand (1,1,1-tris(diphenylphosphinomethyl)ethane) framework, which allows for facile tuning of the reduction potentials by introduction of electron-withdrawing or electron-donating aryl groups. Here, we investigate the synthesis and study of cobalt complexes supported by a triphos ligand substituted with electron donors, such as, p-CH3O-C6H4. The desired ligand is synthesized though a coupling reaction between the diaryl phosphine and 1,3-dichloro-2-(chloromethyl)-2-methylpropane in the presence of KOtBu. The synthesized ligand was combined with cobalt(II) iodide, and the crystals generated were interrogated by X-ray crystallography. Preliminary results indicate that these cobalt complexes catalyze the dehydrogenation of formic acid with good efficiency. The reaction conditions are currently being optimized.