Precious Metal−Molecular Oxygen Complexes: Neon Matrix Infrared Spectra and Density Functional Calculations for M(O2), M(O2)2 (M = Pd, Pt, Ag, Au)

Laser-ablated palladium, platinum, silver, and gold atoms react with molecular oxygen in excess neon during condensation at 4 K. Reaction products, M-(η 2 -OO), M-(η 2 -OO) 2 (M = Pd, Pt), PtO, PtO 2, AuO 2, M-(η 1 -OO) (M = Ag, Au), and anions Ag-(η 1 -OO) -, Au-(η 1 -OO) 2 -, are identified from isotopic shifts and splittings in their matrix infrared spectra. Density functional theory (BPW91 and B3LYP) calculations are performed on the product molecules for comparison of calculated frequencies and 16 O/ 18 O isotopic ratios. Doping with CCl 4 to serve as an electron trap eliminates the anion bands, which further supports the anion identifications. The reaction mechanism and comparison with argon matrix experiments are discussed. The AuOO complex exhibits an unusually large neon−argon matrix shift, which suggests increased charge transfer in the more polarizable argon matrix.