Evaluation of N-Heterocyclic Carbene Counterparts of Classical Gold Clusters; Bonding Properties of Octahedral CAu6, Icosahedral Au13Cl2, and Bi-icosahedral Au25Cl2 Cores from Relativistic DFT Calculations

Abstract

Gold clusters are useful templates for nanosized species retaining a distinctive size-dependent behavior. Usually, a ligand-protected shell passivates such clusters, where their properties can be potentially tuned by introduction of versatile ligands. Here, we explored the recent addition to the well-explored gold–phosphine chemistry, introducing N-heterocyclic carbine (NHC) ligands as characterized by the octahedral carbon-centered CAu6 core, in [CAu6(NHC)6]2+. Our results show their similar bonding patterns in such discrete clusters, with slight preference for the later ligands, enabling the proposition of medium-sized species featuring the predominant icosahedral Au13 structure. NHC counterparts for Au13Cl2(dppe) and Au25Cl2(PPh3)10(SR)5 clusters, denoting both icosahedral and bi-icosahedral central cores, where the bonding features patterns and favorable stability, remain similar to that observed for their phosphine parents and [CAu6(NHC)6]2+ clusters, shedding light on other feasible members for expl...