Synthesis and Characterization of “Atlas-Sphere” Copper Nanoclusters: New Insights into the Reaction of Cu 2+ with Thiols
Thiolates are a widely used ligand class for the stabilization of M(0)-containing gold and silver nanoclusters. Curiously, though, very few thiolate-stabilized Cu nanoclusters are known. Herein, we report an examination of the reactivity of RSH (R = CH 2 CH 2 Ph, n-Bu, n-C 12 H 25 ) with Cu 2+ under anhydrous conditions. These reactions result in the formation of fluorescent "Atlas-sphere"-type copper thiolate nanoclusters, including [Cu 12 (SR') 6 Cl 12 ][(Cu(R'SH)) 6 ] (2, R' = n Bu) and [H(THF) 2 ] 2 [Cu 17 (SR'') 6 Cl 13 (THF) 2 (R''SH) 3 ] (3, R'' = CH 2 CH 2 Ph), which were characterized by X-ray crystallography, electrospray ionization mass spectrometry, NMR spectroscopy, as well as X-ray absorption near-edge structure and extended X-ray absorption fine structure (EXAFS) spectroscopies. Consistent with our X-ray crystallographic results, the edge energies of 2 and 3 suggest they are constructed exclusively with Cu(I) ions. Likewise, EXAFS of 2 and 3 reveals long Cu-Cu pathlengths, which is also consistent with their X-ray crystal structures. Given these results, as well as past work on Cu 2+ /thiol reactivity, we suggest that Cu(0) is unlikely to be formed by the reaction of Cu 2+ with a thiol and that previous reports of Cu(0)-containing nanoclusters synthesized by reaction of Cu 2+ with thiols are likely erroneous.