[Ag15H13(DPPH)5]2+ and [Ag27H22(DPPB)7]3+: Two New Hydride and Phosphine Co-Protected Clusters and Their Fragmentation Leading to Naked Clusters, Ag13+ and Ag25+

Here, we report the synthesis of two new hydride and phosphine coprotected clusters [Ag15H13(DPPH)5]2+ (DPPH = 1,6-bis(diphenylphosphino)hexane) and [Ag27H22(DPPB)7]3+ (DPPB = 1,4-bis(diphenylphosphino)butane). The cluster composition was confirmed by high-resolution electrospray ionization mass spectrometric (HRESI MS) studies and also by other supporting data. To the best of our knowledge, the newly synthesized [Ag15H13(DPPH)5]2+ and [Ag27H22(DPPB)7]3+ clusters are the smallest and the largest known hydride and phosphine coprotected silver clusters, respectively, synthesized in the solution phase. Collision-induced dissociation (CID) was used to probe their fragmentation pattern in the gas phase, which also supported their compositions. During the CID experiment, naked clusters Ag13+ and Ag25+ got formed starting from the ligated Ag15 and Ag27 clusters, respectively, where the number of metal atoms remained nearly the same as in the parent clusters. Collision energy-dependent fragmentation pathways of the formation of naked clusters have been explored in detail. We suggest that silver clusters protected by hydride and phosphine ligands may become useful precursors to make new naked clusters in the gas phase.