Clusters with a Zr6O8 core

Clusters with an octahedral Zr 6 O 4 (OH) 4 core are important building blocks for metal–organic framework structures and cluster-reinforced polymers. The basic chemistry of Zr 6 O 4 (OH) 4 (OOCR) 12 clusters and their dimers is reviewed, including modifications of the ligand shell and expansion of the cluster core by means of additional zirconium atoms or other transition metals. • Zr 6 O 8 is a very resilient structural unit. It can be regarded as the smallest structural section of tetragonal ZrO 2 . • In molecular clusters, the Zr 6 (O/OH) 8 unit is protected by bridging or chelating bidentate ligands, typically carboxylate ligands. • OH ions or water molecules can partly take the place of the bidentate ligands without affecting the Zr 6 O 8 core structure. • Preservation of the Zr 6 (O/OH) 8 unit is also seen in polymerization reactions of appropriately substituted clusters and in metal–organic framework structures. • The octahedral Zr 6 unit can be expanded by additional zirconium or other metal atoms, again evidencing the robustness of this building block. Clusters with the resilient Zr 6 O 4 (OH) 4 core are important building blocks for metal–organic framework structures and cluster-reinforced polymers. The triangular faces of a Zr 6 octahedron are capped by µ 3 -O and/or µ 3 -OH groups, and the Zr 6 cluster core is surrounded by a shell of organic ligands, mostly carboxylate ligands. The basic chemistry of Zr 6 O 4 (OH) 4 (OOCR) 12 clusters and their dimers is reviewed, including modifications of the ligand shell and expansion of the cluster core by means of additional zirconium atoms or other transition metals.