Reactions of Platinum−Carbene Clusters PtnCH2+ (n = 1−5) with O2, CH4, NH3, and H2O: Coupling Processes versus Carbide Formation

Abstract

The gas-phase reactions of the platinum−carbene clusters PtnCH2+ (n = 2−5) with the substrates O2, CH4, NH3, and H2O have been investigated by FT-ICR mass spectrometry and compared with previous results for the mononuclear homologue PtCH2+. The ion−molecule reactions of the clusters PtnCH2+ with O2 and CH4 are similar to the corresponding processes observed for PtCH2+. In contrast, a surprising difference evolves in the reactions with NH3 and H2O. Whereas PtCH2+ mediates carbon−heteroatom bond formation as an attractive way toward methane functionalization, the homologous clusters fail in this regard and exclusively yield the carbide complexes PtnC+·NH3 and PtnC+·H2O, respectively. The differences in reactivities have been analyzed further by means of kinetic isotope effects, H/D-exchange reactions, and energy-dependent collision-induced dissociations of PtnCH2+. Essentially, the higher stabilities of the platinum−carbide clusters PtnC+ compared to PtC+ cause the change in reactivity. This conclusion is c...