The Platinum Hydrido-Methyl Complex:  A Frozen Reaction Intermediate?

Reactions of platinum−argon complexes Pt+Ar m , m = 1−6, with methane (CH4) and methane-d 4 (CD4) were investigated by means of FT-ICR mass spectrometry and DFT calculations. Ligand exchange reactions are observed for Pt+Ar m , m = 2−6, in which up to four argon ligands are replaced by methane. In contrast the bare platinum ion and platinum solvated with one argon ligand lead to the formation of a platinum−carbene complex. Gibbs free enthalpies from ligand exchange reactions of Pt+CH4 with CD4 and H2O provide evidence for the inserted hydrido−methyl complex HPt+CH3 which is corroborated by high-level DFT calculations. No isotopic scrambling is observed for the reaction of Pt+CH4 with CD4 (and the reverse reaction). This is attributed to the inability of the platinum cation to form more than three covalent bonds.