Orientation and conformation of methyl pyruvate on Ni(111)

The molecular orientation and conformation of methyl pyruvate on Ni(lll) was studied in the temperature range 105-220 K. The full monolayer formed at 105 K was found to be almost exclusively in the bidentate cis-conformation, with the molecular plane oriented perpendicular to the surface, in contrast, the low coverage layer at 105 K was found to be composed of a mixture of trans- and cis-methyl pyruvate. However, direct exposure at 200-220 K yielded exclusively cis-bidentate adsorption at all coverages. The observation of the preferred cis-bidentate species is at odds with the adsorption geometry and conformation usually assumed in rationalizations of the enantioselective hydrogenation of methyl pyruvate on chiral-compound modified platinum metal particle catalysts.