tetrakis(N,N'-diethyl-2,3-dihydroxyterephthalamide)-zirconium(IV) tetra-anion 4K+ ions and solvent molecules been removed for clarity Reference: CCDC Structure ICICAZ: C.J. Gramer, K.N. Raymond, Inorg. Chem. , Vol 43, 2004, p. 6397