Sequential Dihydrogen Desorption from Hydride Protected Atomically Precise Silver Clusters and the Formation of Naked Clusters in the Gas Phase

We report the formation of naked cluster ions of silver of specific nuclearities, uncontaminated by other cluster ions, derived from monolayer-protected clusters. The hydride and phosphine co-protected cluster, [Ag18(TPP)10H16]2+ (TPP, triphenylphosphine), upon activation produces the naked cluster ion, Ag17+, exclusively. The number of metal atoms present in the naked cluster is almost the same as that in the parent material. Two more naked cluster ions, Ag21+ and Ag19+, were also formed starting from two other protected clusters, [Ag25(DPPE)8H22]3+ and [Ag22(DPPE)8H19]3+, respectively (DPPE, 1,2-bis(diphenylphosphino)ethane). By systematic fragmentation, naked clusters of varying nuclei are produced from Ag17+ to Ag1+ selectively, with systematic absence of Ag10+, Ag6+, and Ag4+. A seemingly odd number of cluster ions are preferred due to the stability of the closed electronic shells. Sequential desorption of dihydrogen occurs from the cluster ion, Ag17H14+, during the formation of Agn+. A comparison of...