A Superatom Pt21- Cluster with Unique Stability and Aromaticity.

Platinum (Pt) clusters are vital in catalysis due to their stability and reactivity, yet their structure-property relationships remain inadequately comprehended. This study examines the stability of Ptn- (n = 6-35) clusters as a function of size and their reactions with varying doses of common gases. We find two predominant clusters, Pt10- and Pt21-, surviving sufficient N2 gas reactions. The Pt10- cluster derives its stability from a tetrahedral geometry, whereas Pt21- adopts a spheroidal and three-layer (7+7+7) structure with D6h symmetry, exhibiting superatomic orbital features and inorganic aromaticity. Adjacent clusters such as the cage-structured Pt22- and Pt23-, along with low-symmetry or distorted smaller Ptn- clusters (n = 11-20), further contrast the unique stability of the trilaminar superatom Pt21-. These findings elucidate critical structural and electronic factors that govern Pt cluster stability, enlightening atomic-level design of Pt catalysts with modest stability, devoid of N2 contamination and poisoning effects.