Thiacalix[4]arene Etching of an Anisotropic Cu₇₀H₂₂ Intermediate for Accessing Robust Modularly Assembled Copper Nanoclusters

Atom-precise metal nanoclusters (NCs) with large bulk (nuclearity >60) are important species for insight into the embryonic phase of metal nanoparticles and their top-down etching synthesis. Herein, we report a metastable rod-shaped 70-nuclei copper-hydride NC, [Cl@Cu70H22(PhC equivalent to C)(29)(CF3COO)(16)](2+ )(Cu-70), with Cl- as the template, in which the Cl@Cu59 kernel adopts a distinctive metal packing mode along the bipolar direction, and the protective ligand shell exhibits corresponding site differentiation. In terms of metal nuclearity, Cu-70 is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu-70 could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu-8 , A-A-type Cu-22 , A-B-type Cu-23, and A-B-A-type Cu-38) upon etching by p-tert-butylthiacalix-[4]-arene (H(4)TC(4)A), which could not be achieved by "one-pot" synthetic methods. Notably, the patterns of A and B blocks in the Cu NCs could be effectively modulated by employing appropriate counterions and blockers, and the modular assembly mechanism was illustrated through comprehensive solution chemistry analysis using HR-ESI-MS. Furthermore, catalytic investigations reveal that Cu(38 )could serve as a highly efficient catalyst for the cycloaddition of propargylic amines with CO2 under mild conditions. This work not only enriched the family of high-nuclear copper-hydride NCs but also provided new insights into the growth mechanism of metal NCs.