[Cu61(StBu)26S6Cl6H14]+: A Core–Shell Superatom Nanocluster with a Quasi‑J36 Cu19 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.尽管核壳铜金属纳米团簇（core–shell copper metal nanoclusters）是兼具实际应用价值与基础科研意义的新兴材料，但其合成进度却落后于金、银纳米团簇——这一困境源于铜极低的半电池还原电势（half-cell reduction potential）M(I)/M(0)。为攻克该合成难题，我们提出一种简便反应策略，使用温和还原剂硼烷叔丁胺复合物（borane tert-butylamine complex），成功制备出核壳超原子铜纳米团簇[Cu₆₁(StBu)₂₆S₆Cl₆H₁₄]⁺（其中-StBu为叔丁基硫醇盐（tert-butyl thiolate））。该团簇是目前已解析结构的含Cu(0)核壳铜团簇中尺寸最大的一例。该纳米团簇拥有准伸长三角回转双杯形（quasi-J36，其中J36指约翰逊多面体（Johnson solid））的Cu₁₉内核，其外壳由一种新型"18-冠-6"类金属硫化物带束缚结合。得益于优异的稳定性，该团簇在质谱（mass spectrometry）检测中仅呈现单一分子离子峰，未出现任何团簇碎裂信号——这在铜纳米团簇中尚属首次观测到，为研究者以原子级精度开展纳米团簇组成、电荷、稳定性及反应机制研究铺平了道路，而该精度唯有质谱技术可实现。