[Ag₄₈(C≡CtBu)₂₀(CrO₄)₇]: An Atomically Precise Silver Nanocluster Co-protected by Inorganic and Organic Ligands

The elaborate selection of capping ligands is of great importance in the synthesis of atomically precise metal nanoclusters. Organic thiolates, alkynyls, phosphines, and/or their combinations are the ligands most widely utilized to protect metal nanoclusters, while inorganic oxo anions have been almost neglected in this field. Herein, the first CrO 4 2– / t BuC≡C – co-capped Ag 48 nanocluster ( SD/Ag48, SD = SunDi) was synthesized and structurally characterized by single-crystal X-ray diffraction. The pseudo-5-fold symmetric metal skeleton of SD/Ag48 shows a core–shell structure composed of a Ag 23 cylinder encircled by an outer Ag 25 shell. Unprecedentedly, coexistence of inorganic (CrO 4 2– ) and organic ( t BuC≡C – ) ligands was observed on the surface of SD/Ag48 . The inorganic CrO 4 2– anion plays three important roles in the construction of silver nanoclusters: (i) passivating the Ag 23 kernel; (ii) connecting the core and shell; and (iii) protecting the Ag 25 shell. This nanocluster belongs to a 14e superatom system and exhibits successive molecule-like absorption bands from the visible to the ultraviolet region. This work not only establishes a fresh inorganic ligand strategy in the synthesis of silver nanoclusters but also provides a new insight into the important surface coordination chemistry of CrO 4 2– in the shape control of silver nanoclusters.