Au54(Et3P)18Cl12: a structurally related cluster to Au32(Et3P)12Cl8 gives insight into the formation process

Abstract

The reaction of Et₃PAuCl with NaBH₄ in EtOH leads to the metalloid gold cluster Au₃₂(Et₃P)₁₂Cl₈ (Au₃₂) or Au₅₄(Et₃P)₁₈Cl₁₂ (Au₅₄) depending on the work-up procedure of the reaction mixture. The molecular structure of Au₅₄ is determined by X-ray diffraction and can be described as a fusion of two Au₃₂ clusters showing a similar solubility. The metalloid cluster Au₅₄ can be either described by a shell model or as a combination of tetrahedral Au₄X units (X = Cl, Et₃P); edge and face sharing, whereas tetrahedral Au₄ units are a central motif in gold cluster chemistry. This novel Au₅₄ gold cluster gives another unique insight into the formation or decomposition process of metalloid clusters, indicating that Au₃₂ and Au₅₄ form from a single yet unknown cluster source.