Cation-templated synthesis of a Fe₄Co₂₀ cyanometallate cluster

Despite significant progress in the synthesis of cyanometallate complexes with well-defined structures and tunable magnetic properties, the construction of high-nuclearity cyanometallate clusters remains a major synthetic challenge. Herein, we report the successful preparation of a high-nuclearity Fe/Co cyanometallate cage, Fe₄Co₂₀, using a hierarchical, cation-templated assembly strategy. This approach involves the incorporation of a preorganized Co₄ subcluster into a "super-square" framework through cyanide bridging, directed by a tetraethylammonium (NEt₄⁺) cation acting as a structure-directing template with an approximately square geometry. Within the resulting discrete cluster, the cobalt centers exhibit diverse coordination environments, including N₂O₂, N₂O₄, and N₃Cl, giving rise to an exceptional degree of structural complexity. Magnetic studies reveal dominant antiferromagnetic interactions, with no evidence of long-range magnetic ordering down to 2 K. This work highlights the potential of cation-templated synthesis as an effective strategy for constructing complex cyanometallate clusters with tunable magnetic and functional properties.