Assembly of a Heterometallic Cu(II)-Pd(II) Cage by Post-assembly Metal Insertion.

Porous structures based on multi-metallic motifs are receiving growing interest, but their general preparation still remains a challenge. Here, we report the self-assembly and structure of a Cu II metal-organic cage (MOC) that is functionalized with free bis(pyrazolyl)methane sites. The homometallic Cu 4 L 4 cage is isolated as a water-stable crystalline solid, and its formation is dependent on metal-ligand stoichiometry and the pre-organization of the Cu 2 paddlewheel. We show by X-ray diffraction and SEM-EDX that Pd II chloride can be quantitatively inserted into the free chelating sites of the MOC to yield a [Cu 4 (L(PdCl 2 )) 4 ] structure. Moreover, the solvent employed in the metalation dictates the solid-state isomerism of the heterometallic cage─a further handle to control the MOC's structural diversity and permanent porosity.