Anion photoelectron spectroscopy of PdCO− and PdCN: Reactivity of Pd−

Abstract

The ground electronic states of PdCO−/PdCO and PdCN−/PdCN are investigated using anion photoelectron spectroscopy (PES). The electron affinity of PdCO− is determined to be 0.604±0.010 eV. The anion PES of PdCO− exhibits a single, vibrationally resolved electronic band assigned to the Σ+1+e−←2Σ+ anion to neutral transition. The neutral carbonyl stretch is resolved and measured to be 2140±60 cm−1. There is an additional, partially resolved 350±40 cm−1 vibrational progression that is attributed to Pd–CO relative motion. The PES of PdCN− exhibits a single peak at 2.543±0.007 eV, which is the electron affinity of PdCN. This vertical electronic band is tentatively assigned to the Σ+2+e−←1Σ+ transition. The highest occupied molecular orbital of both the anion and neutral is described as a nonbonding spd hybrid orbital on Pd that does not affect the ionic bond of the neutral Pd+⋅CN− core. The various reactions of Pd and Pd− with methanol and acetonitrile along with other reactants that may be present in the ion source are considered.