GAS-PHASE DEHYDROGENATION OF SATURATED AND AROMATIC CYCLIC HYDROCARBONS BY PT-N(-4)() (N=1)

Small platinum clusters are readily generated by electron ionization o f Pt-4(PF3)(8) in an FT-ICR mass spectrometer. Pt-n(+) (n = 1-4), clus ter ions of a given n value may then be isolated and reacted with a va riety of gaseous saturated and aromatic cyclic hydrocarbons. The prese nt experiments thus illuminate catalytic dehydrogenation behavior inte rmediate between that of single-atom and bulk platinum. Extensive chem isorption (dehydrogenation of the hydrocarbon) and physisorption (nond issociative adsorption of intact neutral reagent molecule on the clust er) occur, depending on the particular reagent species. For example, e ach of the clusters exhibits chemisorption with at least one Ligand fo r every neutral reactant species except for hexafluorobenzene. In gene ral, the extent of chemisorption increases with cluster size. Also, so me of the reactions do not proceed by a previously proposed C-H bond i nsertion mechanism. The detailed reaction pathways and product relativ e yields depend on the metal cluster ion, the reagent neutral species, and the stability of the final product.