Ag13-Centered Cuboctahedral Architecture in Inorganic Cluster Chemistry: A DFT Investigation.

The bonding in the [Ag13{μ3-Fe(CO)4}8]3-/5- clusters, which exhibit an Ag13-centered cuboctahedral core, has been analyzed and rationalized by DFT calculations. Not considering the interaction with its encapsulated atom, the empty [Ag12{μ3-Fe(CO)4}8]4- cage can be considered as the assembly of 12 linearly coordinated 14-electron AgI metal centers. Adding a supplementary Ag+ at the center allows some covalent delocalized bonding which to some extent tends to reduce the electron deficiency of the 14-electron centers. Adding now two electrons strengthens the delocalized bonding between the encapsulated atom and its host, making [Ag13{μ3-Fe(CO)4}8]5- a superatom with two jellium (5s-type) electrons. TDDFT calculations predict near-IR absorption for this penta-anion, because of the presence of an a1g HOMO in the middle of an energy gap. Luminescence in the same optical range is also suggested. Other related cubococtahedral species, such as [Ag23(SH)16]-, a model for the known 8-electron [Au23(SR)16]- species which exhibits a bicapped centered dodecahedral kernel structure, have also been investigated.