[Cu-61(S(t)Etu)(26)S6C16H14](+) : A Core-Shell Superatom Nanocluster with a Quasi-J(36) Cu-19 Core and an "18-Crown-6" Metal-Sulfide-like Stabilizing Belt

Although core–shell copper metal nanoclusters are important emerging materials for practical applications and fundamental scientific research, their synthesis lags behind that of gold and silver nanoclusters–challenged by copper’s much lower half-cell reduction potential, M(I)/M(0). To overcome this synthetic hurdle, we introduce a simple reaction strategy, involving the mild reducing agent borane tert-butylamine complex, to produce a core–shell superatom copper nanocluster, [Cu61(StBu)26S6Cl6H14]+ (−StBu; tert-butyl thiolate), which is the largest Cu(0)-containing structurally-solved core–shell copper cluster to-date. The nanocluster exhibits a quasi-elongated triangular gyrobicupola (quasi-J36,J36 = Johnson solid) Cu19 core and a shell held together by a novel “18-crown-6” metal-sulfide-like belt. Because of its stability, this cluster displays a single molecular ion peak in mass spectrometry measurements without any cluster fragmentation signals—a first observation of its kind for copper nanoclusters that paves the way for researchers to study nanocluster composition, charge, stability, and reaction mechanisms with atomic precision that only mass spectrometry could afford.