PNNL

Abstract

We report experimental and theoretical evidence of -aromaticity, which is discovered in the Ta3O3 – cluster via a combined photoelectron spectroscopy and ab initio study. Well-resolved low-lying electronic transitions are observed in the photoelectron spectra of Ta3O3 – and are compared with ab initio calculations, which show that the Ta3O3 – cluster possesses a planar D3h triangular structure. Chemical bonding analyses reveal that among the five valence molecular orbitals responsible for the multi-center metal-metal bonding there is a completely bonding delta and orbital from the 5d atomic orbitals of Ta. The totally delocalized multi-center bond renders -aromaticity for Ta3O3 – and represents a new mode of chemical bonding. Ta3O3 – is the first -aromatic molecule confirmed experimentally and theoretically, suggesting that -aromaticity may exist in many multi-nuclear, low oxidation state transition-metal compounds.