Toward the Solution Synthesis of the Tetrahedral Au20 Cluster

We report solution synthesis of the recently discovered tetrahedral Au{sub 20} cluster coordinated with eight PPh{sub 3} (Ph = Phenyl) ligands. The composition and molecular weight of the Au{sub 20} (PPh{sub 3}){sub 8} complex were confirmed by the isotopic pattern of its doubly charged cation using high resolution mass spectrometry. Collision-induced dissociation experiment showed that four PPh{sub 3} can be easily dissociated from Au{sub 20} (PPh{sub 3}){sub 8}{sup 2+}, resulting in a highly stable Au{sub 20} (PPh{sub 3}){sub 4}{sup 2+} molecule. This observation is consistent with the tetrahedral structure, in which the four apex sites are expected to be strongly bound to the PPh{sub 3} ligands, and is confirmed by theoretical calculations, which predicted a highly stable Au{sub 20} (PH{sub 3}){sub 4} complex with Au-PH{sub 3} bond energies of {approx}1 eV. The current experimental and theoretical observations suggest that large quantity of ligand-stabilized tetrahedral Au{sub 20} can be obtained, opening the door for exploring its anticipated novel chemical, optical, and catalytical properties.