Orientation and Conformation of Methyl Pyruvate on Ni(111)

The molecular orientation and conformation of methyl pyruvate on Ni(111) 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.