Construction and two-dimensional assembly of double-shell Na@Sn 6 L 6 @Sn 3 L 3 clusters through tetrahedral citrate ligands.

Herein we report double-shell Na@Sn 6 L 6 @Sn 3 L 3 clusters and their further assembly into a 2D layer, which belongs to a rare Sn-oxo coordination cage-based extended structure. Tetrahedral citrate ligands with multiple coordination sites play key roles in such hierarchical assembly.