Overcoming the Crystallization Bottleneck: A Family of Gigantic Inorganic {Pd(x)}(L) (x=84, 72) Palladium Macrocycles Discovered using Solution Techniques

The {Pd(84)}(Ac) wheel, initially discovered serendipitously, is the only reported giant palladium macrocycle—a unique structure that spontaneously assembles from small building blocks. Analogues of this structure are elusive. A new modular route to {Pd(84)}(Ac) is described, allowing incorporation of other ligands, and a new screening approach to cluster discovery. Structural assignments were made of new species from solution experiments, overcoming the need for crystallographic analysis. As a result, two new palladium macrocycles were discovered: a structural analogue of the existing {Pd(84)}(Ac) wheel with glycolate ligands, {Pd(84)}(Gly), and the next in a magic number series for this cluster family—a new {Pd(72)}(Prop) wheel decorated with propionate ligands. These findings confirm predictions of a magic number rule for the family of {Pd(x)} macrocycles. Furthermore, structures with variable fractions of functional ligands were obtained. Together these discoveries establish palladium clusters as a new class of tunable nanostructures. In facilitating the discovery of species that would not have been discovered by orthodox crystallization approaches, this work also demonstrates the value of solution‐based screening and characterization in cluster chemistry, as a means to decouple cluster formation, discovery, and isolation.