Di-niobium gold clusters: Multiply-bonded Nb2 dimer coordinated equatorially by Au atoms

Abstract

We report a joint experimental and theoretical investigation on the structures and bonding of a series of di-niobium gold clusters, Nb2Aux− (x = 2–5), using photoelectron spectroscopy and density functional calculations. Well-resolved spectral features are observed for the Nb2Aux− clusters at different photon energies. Global minimum searches coupled with density functional calculations are performed to find the low-lying structures of the bimetallic clusters. Vertical detachment energies are calculated and compared with the experimental spectra to determine the global minimum structures. The Nb2Aux− (x = 2–5) clusters are found to feature a multiply-bonded Nb2 dimer coordinated equatorially by the Au atoms with Dxh symmetries for x = 2–5, respectively. Each Au atom interacts with the Nb2 dimer via a 3-center delocalized σ bond, while there are no Au…Au interactions. The NbNb bond length is found to increase as the number of gold atoms increases in the Nb2Aux− (x = 2–5) clusters, as a result of the decrease of the bond order for the Nb2 moiety from x = 2 to 5.