Silsesquioxane-Protected Silver Superatom

Silsesquioxanes as versatile organic–inorganic hybrids with terminal siloxyl sites have been utilized to construct diverse metallasilsesquioxane complexes, yet their niche in silver nanoclusters remains largely unexplored. Herein, we report the first silsesquioxane-protected superatomic silver nanocluster, [Ag 40 (Ph 4 Si 4 O 8 ) 6 ( t BuC≡C) 8 ] ( Ag40 ), acquired through an “adaptive multipath synthesis” that circumvents the long-standing limitations imposed by hard and soft acids and bases principles in Ag(I) coordination chemistry. Single-crystal X-ray diffraction analysis reveals a kernel-shell architecture: a face-centered-cubic Ag 16 8+ kernel, encapsulated by a [Ag 24 (Ph 4 Si 4 O 8 ) 6 ] cage and t BuC≡C – ligands. Synthetic methodology studies indicate that the macrocyclic all-cis- T 4: Ph 4 Si 4 O 8 4– ligands can be accessed via three distinct routes: in situ generation, pre -synthesis, and hierarchical -synthesis, all of which involve the hydrolytic condensation of PhSi(OR) 3 (R = Me, Et). Of these, the hierarchical approach addresses the limitations of the other two routes (poor stereochemical control in the in situ route and delayed supersaturation-induced slow crystallization in the pre -synthesis route), improving both the reproducibility and the growth efficiency of the Ag40 crystals. The mass spectrometry analysis not only provides compelling evidence for in situ transformation from cis, cis -T 3 to all-cis -T 4 ligands but also reveals the assembly pathways for the Ag 40 nanocluster either in pre -synthesis or in hierarchical -synthesis, underscoring the dynamic transformation of cyclic oligomeric silsesquioxanes and its critical role in capturing the ultrasmall subvalent silver kernel. Notably, Ag40 exhibits superatomic 1D→1P transition-dominated red phosphorescent emission, persisting in nondegassed solutions. As the highest-nuclearity oligosiloxane-capped metal cluster and first superatomic silver-silsesquioxane species, Ag40 establishes a paradigm for silica-supported superatom synthesis and advances hard-base-protected coinage metal nanoclusters.