Ligand accommodation causes altered reactivity of silver clusters with iodomethane: superatomic stability of Ag9I2+ in mimicking XeF2

Exploring metal cluster reactivity with alkyl halides enables to understand the related chemical mechanism of metal surfaces in terms of active sites. Here we report a study of Ag-n(+)(n = 1-27) clusters reacting with iodomethane by a flow tube apparatus in tandem with a customized triple quadrupole mass spectrometer. Strong even/odd alternation of the Ag-n(+) is observed in their reactions with CH3I, where silver clusters with even-number, Ag-2n(+), find favorable products of Ag2nI1,3+ series, while the Ag-2n-1(+) clusters form Ag2n-1I2,4+ products. Interestingly, Ag-9(+) shows up with prominent mass abundance but allows for the formation of Ag9I2+, which finds an echo with the formation of Ag10I3+. We illustrate the enhanced stability of Ag9I2+ and Ag10I3+ by showing their significantly enlarged highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps and balanced charge distribution compared with the bare metal clusters, respectively. Also elucidated, is the superatomic nature of these bare and iodinated silver clusters, especially Ag9I2+ which mimics the rare-gas compound XeF2. This study expands a vivid example of special and general superatoms, and enriches the general knowledge on how a ligand stabilizes a metal cluster.

Automated summary

This study explores the chemical mechanism of metal surfaces in terms of active sites through the reactivity of metal clusters with alkyl halides. The results show that silver clusters exhibit strong even/odd alternation in their reactions with iodomethane, forming different products based on the number of silver atoms in the clusters. Additionally, the study elucidates the superatomic nature of iodinated silver clusters and how ligands stabilize metal clusters.