Phosphinous Acid–Phosphinito Tetra-Icosahedral Au(52) Nanoclusters for Electrocatalytic Oxygen Reduction

[Image: see text] While the formation of superatomic nanoclusters by the three-dimensional assembly of icosahedral units was predicted in 1987, the synthesis and structural determination of such clusters have proven to be incredibly challenging. Herein, we employ a mixed-ligand strategy to prepare phosphinous acid–phosphinito gold nanocluster Au(52)(HOPPh(2))(8)(OPPh(2))(4)(TBBT)(16) with a tetra-icosahedral kernel. Unlike expected, each icosahedral Au(13) unit shares one vertex gold atom with two adjacent units, resulting in a “puckered” ring shape with a nuclearity of 48 in the kernel. The phosphinous acid–phosphinito ligand set, which consists of two phosphinous acids and one phosphinito motif, has strong intramolecular hydrogen bonds; the π–π stacking interactions between the phosphorus- and sulfur-based ligands provide additional stabilization to the kernel. Highly stable Au(52)(HOPPh(2))(8)(OPPh(2))(4)(TBBT)(16) serves as an effective electrocatalyst in the oxygen reduction reaction. Density functional theory calculations suggest that the phosphinous acid–phosphinito ligands provide the most active sites in the electrochemical catalysis, with O* formation being the rate-determining step.