Kinetically controlled synthesis of Au-102(SPh)(44) nanoclusters and catalytic application

摘要

We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au-102(SPh)(44) nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au-102(SPh)(44) nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au-99(SPh)(42), instead of Au-102(SPh)(44), is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 degrees C). Interestingly, the Au-102(SPh)(44) nanoclusters also can convert to Au-99(SPh)(42) with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au-102(SPh)(44) nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S(vO)-R' sulfoxides). The Au-102(SPh)(44)/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process.