Absolute configuration retention of a configurationally labile ligand during dynamic processes of thiolate protected gold clusters

• Published in: Chemical science (Cambridge) 2021-07, Vol.12 (27), p.9413-9419
• Main Authors: Wang, Yanan, Makkonen, Esko, Chen, Xi, Bürgi, Thomas
• Format: Article
• Language: English
• Subjects: Chemistry; Heat exchange; Ligands; Metal clusters; Monolayers; Racemization
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d1sc01702k

Monolayer protected metal clusters are dynamic nanoscale objects. For example, the chiral Au 38 (2-PET) 24 cluster (2-PET: 2-phenylethylthiolate) racemizes at moderate temperature. In addition, ligands and metal atoms can easily exchange between clusters. Such processes are important for applications of monolayer protected metal clusters; however, the mechanistic study of such processes turns out to be challenging. Here we use a configurationally labile, axially chiral ligand, biphenyl-2,2′-dithiol (R/S-BiDi), as a probe to study dynamic cluster processes. It is shown that the ligand exchange of free R/S-BiDi on a chiral Au 38 (2-PET) 24 cluster is diastereospecific. Using chiral chromatography, isolated single diastereomers of the type anticlockwise/clockwise-Au 38 (2-PET) 22 (R/S-BiDi) 1 could be isolated. Upon heating, the cluster framework racemizes, while the R/S-BiDi ligand does not. These findings demonstrate that during cluster racemization and/or ligand exchange between clusters, the R/S-BiDi ligand is sufficiently confined, thus preventing its racemization, and exclude the possibility that the ligand desorbs from the cluster surface. The ligand exchange between a configurationally labile BiDi ligand and intrinsically chiral Au 38 gold nanoclusters is diastereoselective. More importantly, the adsorbed ligand retains its configuration during dynamic cluster processes.