Hydroxy carboxylate substituted oxozirconium clusters

Abstract

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-β-naphthoic acid and salicylic acid, respectively. The naphthoate-substituted cluster has a rather open structure, the dianion of 1-hydroxy-β-naphthoic 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 salicylate-substituted cluster is highly condensed and contains the octahedral Zr6O4(OH)4 core also found in other oxozirconium clusters. Four salicylate ligands bridge edges of the Zr6 octahedron via their COO group; their phenolic OH groups do not coordinate to a metal atom. The other eight salicylate ligands are dianionic. Each of them bridges an edge of the Zr6 octahedron via their COO group and additionally chelates one of the zirconium atoms condensed to the Zr6 cluster core by their phenolate oxygen and one of the oxygen atoms of the COO group.