Gas phase multicollisional reactions of metal cluster cations with water molecules

Reactions within complexes consisting of metal cluster cations and water mo lecules have been studied using a pulsed arc cluster source (PACS) and a re flectron time-of-flight mass spectrometer. The mass spectra obtained from m etal-water cluster ions reveals extensive dehydrogenation of the associated water molecules resulting in the formation of metal-oxide clusters of the general form M-M O-P(OH)(+) (where M=copper, barium and holmium). For clust ers with barium, and holmium, the dehydrogenation occurs from P greater tha n or equal to 1 and for copper for P greater than or equal to 3. These meta l oxide and hydroxide products are more abundant than both that of the bare metal clusters M-M(+) and the associated hydrated metal clusters M-M(+)(H2 O)(N). The stability of the metal oxide clusters as determined by the relat ive abundances of these species as a function of N and P is seen to corresp ond to oxidation numbers accessible to the metal ions. The correspondence b etween the formal oxidation number of a metal and its propensity for oxide formation is investigated. Possible mechanisms for the formation of the obs erved complex ions are proposed. For complexes containing Ho-M(+) the varia tion of the abundances with cluster size is discussed.