Connection of Metallamacrocycles via Dynamic Covalent Chemistry: A Versatile Method for the Synthesis of Molecular Cages

A modular approach for the synthesis of cage structures is described. Reactions of [(arene)RuCl<sub>2</sub>]<sub>2</sub> [arene = <i>p</i>-cymene, 1,3,5-C<sub>6</sub>H<sub>3</sub>Me<sub>3</sub>, 1,3,5-C<sub>6</sub>H<sub>3</sub>(<i>i</i>-Pr)<sub>3</sub>] with formyl-substituted 3-hydroxy-2-pyridone ligands provide trinuclear metallamacrocycles with pendant aldehyde groups. Subsequent condensation reactions with di- and triamines give molecular cages with 3, 6, or 12 Ru centers in a diastereoselective and chemoselective (self-sorting) fashion. Some of the cages can also be prepared in one-pot reactions by mixing [(arene)RuCl<sub>2</sub>]<sub>2</sub> with the pyridone ligand and the amine in the presence of base. The cages were comprehensively analyzed by X-ray crystallography. The diameter of the largest dodecanuclear complex is ∼3 nm; the cavity sizes range from 290 to 740 Å<sup>3</sup>. An amine exchange process with ethylenediamine allows the clean conversion of a dodecanuclear cage into a hexanuclear cage without disruption of the metallamacrocyclic structures.