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Hydrated aluminum cluster cations Al + (H 2 O) n with n ) 3-50 were stored in a collision-free environment, and their unimolecular fragmentation induced by the room temperature "black body" infrared background was studied. An interesting size-dependent intracluster reaction resulting in oxidation of the aluminum cation and elimination of molecular hydrogen was observed. The results are discussed and compared with similar recent studies of hydrated magnesium clusters.

Reactions of platinum-argon complexes Pt + Ar m , m ) 1-6, with methane (CH 4 ) and methane-d 4 (CD 4 ) 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 + CH 4 with CD 4 and H 2 O provide evidence for the inserted hydrido-methyl complex HPt + CH 3 which is corroborated by high-level DFT calculations. No isotopic scrambling is observed for the reaction of Pt + CH 4 with CD 4 (and the reverse reaction). This is attributed to the inability of the platinum cation to form more than three covalent bonds.

Trapped hydrated aluminum cluster ions are studied by FT-ICR mass spectrometry on a time scale of several seconds. Blackbody radiation, besides causing the fragmentation of the cluster by stepwise loss of individual water molecules, induces in hydrated aluminum clusters Al + (H 2 O) n an intracluster reaction yielding hydrated hydroxide and releasing molecular hydrogen. Local deviations of the individual rate constants for the water loss process from a linear size dependence are due to increased rigidity of certain sizes due to the formation of stabilizing hydrogen-bonded bridges. In comparison with previously studied hydrated ions, surface versus internal solvation is discussed. The preferential occurrence of the intracluster reaction in the size region of n ) 11-24 is attributed to a concerted proton-transfer mechanism, in which a chain of at least two water molecules is needed to transfer a proton between two first solvation shell water molecules, leading to formation of an Al(OH) 2 + (H 2 O) n hydrated aluminum dihydroxide cation and molecular hydrogen. The Al + (H 2 O) n species with n g 13 and all investigated Al(OH) 2 + (H 2 O) m species are able to react with and "dissolve" HCl. The maximum number of HCl molecules in the cluster strongly depends on the number of water molecules available for solvation. The presence of HCl in the cluster removes the upper limit for the intracluster reaction, which leads to the formation of molecular hydrogen, driven by blackbody radiation. This is taken as further evidence for the validity of the proton-transfer mechanism.

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