Metal cluster interaction with protons

The conjugate base of a cluster generated by deprotonation (see Section 5.1) is a Lewis base. Any metal-metal, metal boron, or boron boron bond is a potential Lewis base. The former have considerable nucleophilic character if anionic and effectively interact with electrophiles more complex than the proton. As the site of basicity is associated with framework bonding, this reaction type results in cluster building, for... 

Bivalent cations also affect the proton distribution if small cages have been filled, e.g., with Mg ions, the protons that are created during the reduction of a transition metal ion will predominantly stay in the supercages, where they interact with the metal clusters, as will be described in more detail below. Because such adducts can act as very active sites, a catalyst promoter effect of Ca and Mg on reduced Pd has therefore been attributed, in part, to the enhanced concentration of metal-proton adducts in accessible supercages (765). 

The interaction of metal clusters in zeolites with protons has been studied by isotope exchange with D2 280-283). The presence of metals or metal impurities is essential for this exchange to occur at moderate temperatures absolutely no exchange between D2 and zeolite protons in metal-free HY is detected at room temperature. In the presence of Pt or Pd, however, exchange is fast and includes all protons in the zeolite, which are detectable by their O—H vibration bands in FTIR. 

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