Hydride Locations and Planar σ‐Aromaticity in Hydrido‐Coinage‐Metal Clusters

Abstract

The atomic‐scale analysis of hydrides within metal clusters remains challenging due to the difficulties in performing spatially resolved characterization experiments. One important issue is understanding how hydrogens bond to metal atoms and their positions. The classification of hydride as either a ligand or doped metal is a difficult problem due to its different impacts on electronic structures of coinage metal (Cu, Ag, and Au) clusters. Here, geometric characteristics, stability and electronic properties of MnH (M=Cu, Ag and Au; n=2–9) clusters are investigated in detail. We find that structure transitions of CunH and AgnH occur at n=5, while all AunH are more inclined to planar configurations, where H atoms prefer to be located on the bridge positions of M−M regardless of different sizes and configurations. Among them, the planar M5H clusters have the same structural framework and higher stability than their neighbors. The AIMD simulations demonstrate that these three clusters still show excellent thermal stability at 700 K. The molecular orbitals and AdNDP analyses reveal that the M5H clusters exhibit three six‐center two‐electron σ bonds throughout whole structural spaces and conform to σ aromaticity rule, which are also further confirmed by the ELF, LOL and NICSzz‐scan analyses.