Molybdenum Hydride Complexes Work Magic On Formic Acid

Simple organic molecules such as methanol and formic acid are attractive chemical storehouses for hydrogen produced using sunlight and other alternative energy sources. Most catalysts for stripping hydrogen off the compounds to power fuel cells or for other uses incorporate precious metals such as ruthenium and iridium, prompting chemists to seek less expensive but equally versatile metals for the job. Michelle C. Neary and Gerard Parkin of Columbia University have found one candidate in molybdenum (Chem. Sci. 2015, DOI: 10.1039/c4sc03128h). The researchers used a series of cyclopentadienyl molybdenum hydride complexes containing a varying number—from zero to three—of carbon monoxide or trimethylphosphine ligands. Depending on the ligand composition and reaction conditions, the catalyst dehydrogenates formic acid to form H₂ and CO₂ or induces formic acid disproportionation to form methanol along with CO₂ and water. Further still, the catalyst can use formic acid as a reagent to transfer hydrogen to ketones and aldehydes to prepare alcohols. The ability to redirect the activity of the catalyst from dehydrogenation to disproportionation or transfer hydrogenation by altering the ligand lineup could be important for renewable energy development, the researchers suggest.