Complexation of Cu(II) and Ni(II) by nitrilotriacetate intercalated in Zn-Cr layered double hydroxides

Direct and indirect anion exchange methods have been used to intercalate a [Zn(II)2-Cr-III] lamellar double hydroxide (LDH), with [Cu(nta)](-) and [Ni(nta)](-) (nta = nitrilotriacetate). For the direct method, a solution of the pre-formed complexes was used to intercalate the LDH while for the indirect method the anionic nta ligand was intercalated, the product was isolated and then reacted with a solution of the metal ion to produce the intercalated complex. LDH phases with vertical and tilted orientations of the complex are proposed to account for the formation of products with basal spacings of 14 and 12 Angstrom, respectively. The preferred arrangement varies with the metal ion, temperature and synthetic method. For the indirect method, two metal salt counter anions, viz., sulfate and tosylate, displaced the metal complex from the interlayer while chloride and nitrate competed poorly for the interlayer positions.