Activation of methane and methane-d4 by ionic platinum clusters

Bimolecular reactions of cationic platinum clusters Pt-n(+), n = 1-24, and anionic platinum clusters Pt-n(-), n = 3-22, with CH4 and CD4 are studied under low pressure conditions in an FT-ICR mass spectrometer, using an isotopically enriched Pt-195 sample. Strongly size-dependent dehydrogenation and formation of PtnCH2+/- is observed for both charge states. Starting with n = 12, cationic clusters also afford stabilization of a [Pt-n, CH4](+) adduct, presumably the HPtnCH3+ insertion compound. Deuteration shifts the lower limit for adduct formation to n = 8. It is suggested that the strong reactivity fluctuations over a wide size range are the gas phase fingerprint of a good heterogeneous catalyst material. (C) 2006 Elsevier B.V. All rights reserved.