Thiacalix[4]arene Etching of an Anisotropic Cu70H22Intermediate 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≡C)29(CF3COO)16]2+(Cu70), with Cl–as the template, in which the Cl@Cu59kernel adopts a distinctive metal packing mode along the bipolar direction, and the protective ligand shell exhibits corresponding site differentiation. In terms of metal nuclearity, Cu70is the largest alkynyl-stabilized Cu-hydride cluster to date. As a typical highly active intermediate, Cu70could undergo a transformation into a series of robust modularly assembled Cu clusters (B-type Cu8, A–A-type Cu22, A–B-type Cu23, and A–B–A-type Cu38) upon etching by p-tert-butylthiacalix[4]arene (H4TC4A), which could not be achieved by “one-pot” synthetic methods. Notably, the patterns of Aand Bblocks 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 Cu38could serve as a highly efficient catalyst for the cycloaddition of propargylic amines with CO2under 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.