In situ reaction monitoring reveals a diastereoselective ligand exchange reaction between the intrinsically chiral Au38(SR)24 and chiral thiols
Journal of the American Chemical Society | 12 Dec 2012
S Knoppe, R Azoulay, A Dass and T Bürgi
The ligand exchange reaction between racemic Au38(2-PET)24 (2-PET: 2-phenylethylthiolate) clusters and enantiopure 1,1'-binapththyl-2,2'-dithiol (BINAS) was monitored in situ using a chiral HPLC approach. In the first exchange step, a clear preference of R-BINAS towards the left-handed enantiomer of Au38(2-PET)24 is observed (about four times faster than reaction with the right-handed enantiomer). The second exchange step is drastically slowed compared to the first step. BINAS substitution deactivates the cluster for further exchange, which is attributed to (stereo)electronic effects. The results constitute the first example of a ligand exchange reaction in a thiolate-protected gold cluster with directed enrichment of a defined species in the product mixture. This may open new possibilities for the design of nanomaterials with tailored properties.
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