ABSTRACT
Gold chemistry and the synthesis of colloidal gold have always caught the attention of scientists. While Faraday was investigating the physical properties of colloidal gold in 1857 without probably knowing anything about the exact structure of the molecules, 150 years later the working group of Kornberg synthesized the first structurally characterized multi-shell metalloid gold cluster with more than 100 Au atoms, Au102(SR)44. After this ground-breaking result, many smaller and bigger metalloid gold clusters have been discovered to gain a better understanding of the formation process and the physical properties. In this review, first of all, a general overview of past investigations is given, leading to metalloid gold clusters with staple motifs in the ligand shell, highlighting structural differences in the cores of these clusters. Afterwards, the influence of the synthetic procedure on the outcome of the reactions is discussed, focusing on recent results from our group. Thereby, newly found structural motifs are taken into account and compared to the existing ones. Finally, a short outlook on possible subsequent reactions of these metalloid gold clusters is given.
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.
ABSTRACT
Three multi-shell metalloid gold clusters of the composition Au32 (R3 P)12 Cl8 (R=Et, n Pr, n Bu) were synthesized in a straightforward fashion by reducing R3 PAuCl with NaBH4 in ethanol. The Au32 core comprises two shells, with the inner one constituting a tilted icosahedron and the outer one showing a distorted dodecahedral arrangement. The outer shell is completed by eight chloride atoms and twelve R3 P groups. The inner icosahedron shows bond lengths typical for elemental gold while the distances of the gold atoms in the dodecahedral arrangement are in the region of aurophilic interactions. Quantum-chemical calculations illustrate that the Jahn-Teller effect observed within the cluster core can be attributed to the electronic shell filling. The easily reproducible synthesis, good solubility, and high yields of these clusters render them perfect starting points for further research.
ABSTRACT
Reducing (Ph3P)AuSC(SiMe3)3 with l-Selectride® gives the medium-sized metalloid gold cluster Au70S20(PPh3)12. Computational studies show that the phosphine bound Au-atoms not only stabilize the electronic structure of Au70S20(PPh3)12, but also behave as electron acceptors leading to auride-like gold atoms on the exterior.
ABSTRACT
The reduction of (Ph3 P)AuCl with NaBH4 in the presence of HSC(SiMe3 )3 , leads to one of the largest metalloid gold clusters: Au108 S24 (PPh3 )16 (1). Within 1 an octahedral Au44 core of gold atoms arranged as in Au metal is surrounded by 48â oxidized Au atoms of an Au48 S24 shell, a novel building block in gold chemistry. The protecting Au48 S24 shell is completed by additional 16â Au(PPh3 ) units, leading to a complete protection of the gold core. Within 1 the Au-Au distances get more molecular on going from the center to the ligand shell. Cluster 1 represents novel structural motives in the field of metalloid gold clusters which also are partly typical for metal atoms in metalloid clusters: Mn Rm (n>m).
