Infrared Spectrum of the Palladium Nitrosyl Complex Isolated in Solid Argon

The reaction of ground-state Pd atoms with NO during condensation in solid argon has been reinvestigated. The Pd(η1-NO) molecule, already characterized in reactions of laser-ablated Pd, is the only product observed for the reaction between one Pd atom and one nitric oxide molecule. Isotopic data on ν1, ν2, and ν3 have been measured in the mid- and far-infrared regions. These enable an independent estimate of the molecular shape on the basis of complete harmonic force-field calculations. The molecule is bent, with a Pd−N−O bond angle around 115 ± 15°, in basic agreement with theoretical predictions. This study provides a useful test for comparing the performance of various quantum mechanical methods for reproducing the spectroscopic properties. The bonding in Pd- and NiNO is analyzed using natural bonding orbital and topological methods.