Aqueous Zirconium Complexes. II. Mixed Chelates 1

Zr(IV) chelates in which not all of the coordination sites . of the metal are satisfied by a multidentate ligand are found to combine with one or two additional moles of a second multidentate ligand to form more completely coordinated compounds which are more stable than those formed by either ligand alone. Particularly simple and stable are the mixed chelates with one mole of EDTA plus one mole of pyrocatechol-3,5-disulfonate, chromotropic salt, 8- hydroxyquinoline-5-sulfonate, oxalic acid, or acetylacetone; one mole of 1,2- diaminocyclohexanetetraacetic acid plus one mole of pyrocatechol-3,5-disulfonate, oxalic acid, 8hydroxyquinoline-5-sulfonate, or acetylacetone; one mole of N- hydroxyethylethylenediaminetriacetic acid plus one mole of procatechol-3,5- disulfonate, or 8-hydroxyquinoline-5-sulfonate; and one mole of nitrilotriacetic acid plus two moles of pyrocatechol-3,5-disulfonate. Other combinations yield soluble Zr(IV) chelate systems which are also quite stable but are somewhat less well-defined. (auth)