CO Activation and Hydrogenation by Palladium Hydride Cluster Anions.

Mass spectrometric analysis of the anionic products of interaction between palladium hydride anions, PdH, and carbon dioxide, CO, in a reaction cell shows an efficient generation of the PdHCO intermediate and isolated formate product. Multiple isomers of the PdHCO intermediates are identified by a synergy between negative ion photoelectron spectroscopy and quantum-chemical calculations. It is shown that a direct mechanism, in which the H atom in PdH directly activates and hydrogenates CO, leads to the formation of the formate product. An indirect mechanism, on the other hand, leads to a stable HPdCO structure, where CO is chemisorbed onto the Pd atom.