Elucidating the Structures of Intermediate Fragments during Stepwise Dissociation of Monolayer-Protected Silver Clusters

Fragmentation dynamics of ligated coinage metal clusters reflects their structural and bonding properties. So far methodological challenges limited probing structures of the fragments. Herein, we resolve the geometric structures of the primary fragments of [Ag₂₉L₁₂]³⁻, i.e. [Ag₂₄L₉]²⁻, [Ag₁₉L₆]⁻ and [Ag₅L₃]⁻ (L is 1,3-benzene dithiolate). For this, we used trapped ion mobility mass spectrometry to determine collision cross sections of the fragments and compared them to structures calculated by density functional theory. We also report that following two sequential [Ag₅L₃]⁻ elimination steps, further dissociation of [Ag₁₉L₆]⁻ also involves a new channel of Ag₂ loss and Ag−S and C−S bond cleavages. This reflects a competition between retaining the electronic stability of 8 e⁻ superatom cluster cores and increasing steric strain of ligands and staples. These results are also of potential interest for future soft-landing deposition studies aimed at probing catalytic behavior of Ag clusters on supports.