Toward the solution synthesis of the tetrahedral Au20 cluster

We report the observation in solution of the recently discovered tetrahedral Au-20 cluster coordinated with eight PPh3 (Ph = phenyl) ligands. The composition and molecular weight of the Au-20(PPh3)(8) complex were confirmed by the isotopic pattern and accurate mass measurement of its doubly charged cation using high-resolution mass spectrometry. A collision-induced dissociation experiment showed that four PPh3 ligands can be easily removed from Au-20(PPh3)(8), resulting in a highly stable Au-20(PPh3)(4)(2+) ion. This observation is consistent with the tetrahedral Au-20, in which the four apex sites are expected to bond to the PPh3 ligands strongly, and is confirmed by theoretical calculations that predict a highly stable Au-20(PH3)(4) Complex with Au-PH3 bond energies of similar to1 eV. The current experimental and theoretical observations suggest that large quantities of ligand-stabilized tetrahedral Au-20 can be obtained, opening the door for exploring its anticipated novel chemical, optical, and catalytic properties.