A family of lead clusters with precious metal cores

Gold nanoparticles have been used for centuries, both for decoration and in medical applications. More recently, many of the major advances in cluster chemistry have involved well-defined clusters containing tens or hundreds of atoms, either with or without a ligand shell. In this paper we report the synthesis of two gold/lead clusters, [Au₈Pb₃₃]^6- and [Au₁₂Pb₄₄]^8-, both of which contain nido [Au@Pb₁₁]^3- icosahedra surrounding a core of Au atoms. Analogues of these large clusters are not found in the corresponding Ag chemistry: instead, the Ag-centered nido icosahedron, [Ag@Pb₁₁]^3-, is the only isolated product. The structural chemistry, along with the mass spectrometry which shows the existence of [Au₂Pb₁₁]^2- but not [Ag₂Pb₁₁]^2-, leads us to propose that the former species is the key intermediate in the growth of the larger clusters. Density functional theory indicates that secondary π-type interactions between the [Au@Pb₁₁]^3- ligands and the gold core play a significant part in stabilizing the larger clusters.