Reactions of platinum-argon complexes Pt+Arm, 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+Arm, 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 hydride-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 land the reverse reaction). This is attributed to the inability of the platinum cation to form more than three covalent bonds.