Thiacalix[4]arene Etching of an Anisotropic Cu 70 H 22 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@Cu 70 H 22 (PhC≡C) 29 (CF 3 COO) 16 ] 2+ ( Cu 70 ), with Cl - as the template, in which the Cl@Cu 59 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 CO 2 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.