Kinetically controlled synthesis of Au102(SPh)44 nanoclusters and catalytic application

Abstract

We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au₁₀₂(SPh)₄₄ nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au₁₀₂(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, Au₉₉(SPh)₄₂, instead of Au₁₀₂(SPh)₄₄, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au₁₀₂(SPh)₄₄ nanoclusters also can convert to Au₉₉(SPh)₄₂ with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO₂-supported Au₁₀₂(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(O)–R′ sulfoxides). The Au₁₀₂(SPh)₄₄/TiO₂ catalyst also shows excellent recyclability in the sulfoxidation process.