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

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≡C)₂₉(CF₃COO)₁₆]²⁺ (Cu), 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 is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu, A-A-type Cu, A-B-type Cu, and A-B-A-type Cu) upon etching by p-tert-butylthiacalix[4]arene (H₄TC₄A), 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 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.