The oxidation of methane with molecular oxygen using the atomic platinum cation as a catalyst, yielding methanol, formaldehyde, and higher oxidation products, has been studied both computationally and experimentally. The most relevant reaction pathways have been followed in detail. To this end a large number of stationary points, both minima and transition states, have been optimized using a hybrid density functional theory method (B3LYP). At these optimized geometries, energies have been calculated using both an empirical scaling scheme (PCI-80) and the B3LYP method employing extended basis sets with several polarization functions. Good agreement with available experimental data has been obtained. For the parts of the catalytic cycle where detailed experimental results have not been available, the new calculated results have complemented the experimental picture to reach an almost complete understanding of the reaction mechanisms. Spin−orbit effects have been incorporated using an empirical approach, which has lead to improved agreement with experiments. The new FTICR experiments reported in the present study have helped to clarify some of the most complicated reaction sequences.

The effects of 0x0 ligands on lanthanide and actinide cations have been examined for the mono-and dioxocations MO' and MO; of cerium, neodymium, thorium, and uranium by probing C-H and C-C bond activation of hydrocarbons in an FT-ICR mass spectrometer. The metal monoxide cations are readily available by reaction of the "bare" metal cations with 0,, CO,, N,O, or H,O. In the ensuing oxidation of MO', UO: is obtained by each of these oxidants, while CeO' could only be oxidized by N,O.NO, was necessary for the generation of Tho;, and NdOz could not be prepared at all. The monoxides are rather unreactive and only dehydrogenate reactive substrates such as 1-butene and 1,4-cyclohexadiene to generate the corresponding butadiene or benzene complexes. In con-

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The first catalytic oxidative activation of methane in the gas phase employs high‐vacuum conditions and Pt+ ions generated by laser desorption. In the presence of O2 the initially generated Pt+CH2 is oxidized to formic acid (65%), formaldehyde (25%), and methanol (10%). The picture on the right shows the most important part of the complicated catalytic cycle.

Relativistic coupled cluster studies are performed for the structures, dissociation energies, ionization potentials and electron affinities for Au, Au2 and Au3. The calculations show that the upward shifts of the ionization potentials and electron affinities of Aun clusters by approximately 2 eV compared to Cun or Agn base on relativistic effects. Au3+ is predicted to adopt a trigonal planar structure (D3h, A11), Au3 a E⊗ε Jahn–Teller distorted structure (C2v,2A1) 0.1 eV below the linear Σu+2 arrangement, and Au3− adopts a linear structure (1Σg+).