Ironing Out Formic Acid

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Science  09 Jul 2010:
Vol. 329, Issue 5988, pp. 121
DOI: 10.1126/science.329.5988.121-c

Some biomass transformations, such as pathways that deoxygenate sugars, produce formic acid as a by-product, and the options for downstream use of large amounts of it have been limited. Boddien et al. now report a photocatalytic route for liberating hydrogen from formic acid. Previous catalysts for this reaction used noble metals, but after screening a range of more abundant transition metals, the authors discovered that effective catalysts formed in situ from an iron carbonyl cluster [Fe3(CO)12], a polydentate nitrogen-donating ligand, and triphenylphosphine. Under irradiation with the visible light from a 300-W xenon arc lamp, these catalysts generated hydrogen from formic acid solutions stabilized with triethylamine; the best examples had turnover frequencies up to 200 per hour and turnover numbers exceeding 100. Extensive spectroscopic studies implicated photogenerated iron hydrides as active species.

J. Am. Chem. Soc. 132, 10.1021/ja100925n (2010).

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