Hydroxy carboxylate substituted oxozirconium clusters

The oxozirconium clusters Zr6O2(OPr)(16)(OOC-C10H6O)(2)(PrOH)(2) and Zr10O6 (OH)(4)(OOC-C6H4OH)(8)(OOC-C6H4O)(8). 6 PrOH were obtained in quantitative yield, when Zr(OPr)(4) was reacted with a 10-fold excess of 1-hydroxy-beta- naphthoic acid and salicylic acid, respectively. The naphthoate-substituted cluster has a rather open structure, the dianion of 1-hydroxy-beta-naphtho ic acid acting as a tetradentate ligand. The carboxylate group chelates one zirconium atom, and one oxygen of the carboxy group and the aryloxy group chelate a neighboring zirconium atom. In contrast, the structure of the sal icylate-substituted cluster is highly condensed and contains the octahedral Zr6O4(OH)(4) core also found in other oxozirconium clusters. Four salicyla te ligands bridge edges of the Zr-6 octahedron via their COO group; their p henolic OH groups do not coordinate to a metal atom. The other eight salicy late ligands are dianionic. Each of them bridges an edge of the Zr-6 octahe dron via their COO group and additionally chelates one of the zirconium ato ms condensed to the Zr-6 cluster core by their phenolate oxygen and one of the oxygen atoms of the COO group.