An Atomically Precise Pyrazolate‐Protected Copper Nanocluster Exhibiting Exceptional Stability and Catalytic Activity

Abstract The synthesis of atomically precise copper nanoclusters (Cu‐NCs) with high chemical stability is a prerequisite for practical applications, yet still remains a long‐standing challenge. Herein, we have prepared a pyrazolate‐protected Cu‐NC ( Cu8 ), which exhibited exceptional chemical stability either in solid‐state or in solution. The crystals of Cu8 are still suitable for single crystal X‐ray diffraction analysis even after being treated with boiling water, 8 wt % H 2 O 2 , high concentrated acid (1 M HCl) or saturated base (≈20 M KOH), respectively. More importantly, the structure of Cu8 in solution also remained intact toward oxygen, organic acid (100 eq. HOAc) or base (400 eq. dibutylamine) confirmed by 1 H NMR and UV/Vis analysis. Taking advantage of high alkali‐resistant, Cu8 illustrates excellent catalytic activity for the synthesis of indolizines, and it can be reused for at least 10 cycles without losing catalytic performance.