σ Aromaticity of the Bimetallic Au5Zn+ Cluster

Abstract
Experimental and theoretical evidence for a "sigma aromatic" bimetallic cluster is presented. A mass spectrometric analysis of AuNZn+ (N = 2-44) photofragments shows Au5Zn+ to be very abundant, proving its high stability. Calculations predict that Au5Zn+ has a planar geometry and six valence s electrons occupying delocalized sigma-bonded molecular orbitals in a manner similar to that of aromatic organic compounds, except for their nodal properties in the molecular plane. The delocalized sigma electrons provide diamagnetic ring currents, suggesting Au5Zn+ is aromatic.