Ligand effects in catalysis by atomically precise gold nanoclusters

Atomically precise gold nanoclusters are ideal model catalysts with well-defined compositions and tunable structures. Determination of the ligand effect on catalysis requires the use of gold nanoclusters with protecting ligands as the only variable. Two isostructural Au 38 nanoclusters, [Au 38 (L) 20 (Ph 3 P) 4 ] 2+ (L = alkynyl or thiolate), have been synthesized by a direct reduction method, and they have an unprecedented face-centered cubic (fcc)–type Au 34 kernel surrounded by 4 AuL 2 staple motifs, 4 Ph 3 P, and 12 bridging L ligands. The Au 34 kernel can be derived from the fusion of two fcc-type Au 20 via sharing a Au 6 face. Catalytic performance was studied with these two nanoclusters supported on TiO 2 (1/TiO 2 and 2/TiO 2 ) as catalysts. The alkynyl-protected Au 38 are very active (>97%) in the semihydrogenation of alkynes (including terminal and internal ones) to alkenes, whereas the thiolated Au 38 showed a very low conversion ( 2 activation. This work presents a clear demonstration that catalytic performance of gold nanoclusters can be modulated by the controlled construction of ligand spheres.