Uranyl(VI) complexes of [O,N,O,N ']-type diaminobis(phenolate) ligands: Syntheses, structures and extraction studies

: Sopo H, Lehtonen A, Sillanpaa R

Publisher: PERGAMON-ELSEVIER SCIENCE LTD

: 2008

Polyhedron

: POLYHEDRON

: 27

: 1

: 95

: 104

: 10

: 0277-5387

DOI: https://doi.org/10.1016/j.poly.2007.08.047

The syntheses and crystal structures of four new uranyl complexes with [O,N,O,N']-type ligands are described. The reaction between uranyl nitrate hexahydrate and the phenolic ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N',N'-dimethylethylenediamine)], H(2)L1 in a 1:2 molar ratio (M to L), yields a uranyl complex with the formula [UO2(HL1)(NO3)]center dot CH3CN (1). In the presence of a base (triethylamine, one mole per ligand mole) with the same molar ratio, the uranyl complex [UO2(HL1)21 (2) is formed. The reaction between uranyl nitrate hexahydrate and the ligand [(NN-bis(2-hydroxy-3,5-di-t-butylbenzyl)-N,N'-dimethylethylenediamine)], H2L2, yields a uranyl complex with the formula [UO2(HL2)(NO3)]center dot 2CH(3)CN (3) and the ligand [N-(2-pyridyimethyl)-N,N-bis(2-hydroxy-3,5-dimethylbenzyl)amine], H2L3, in the presence of a base yields a uranyl complex with the formula [UO2(HL3)(2)]center dot 2CH(3)CN (4). The molecular structures of 1-4 were verified by X-ray crystallography. The complexes 1-4 are zwitter ions with a neutral net charge. Compounds 1 and 3 are rare neutral mononuclear [UO2(HLn)(NO3)] complexes with the nitrate bonded in eta(2)-fashion to the uranyl ion. Furthermore, the ability of the ligands H(2)L1-H(2)L4 to extract the uranyl ion from water to dichloromethane, and the selectivity of extraction with ligands H(2)L1, H(3)L5 (N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-3-amino-1-propanol), H(2)L6 center dot HCl (N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane center dot HCl) and H3L7 center dot HCl (NN-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-6-amino-1-hexanol center dot HCI) under varied chemical conditions were studied. As a result, the most efficient and selective ligand for uranyl ion extraction proved to be H(3)L7 center dot HCl. (C) 2007 Elsevier Ltd. All rights reserved.

crystal structures, phenolate ligands, uranyl complex, uranyl ion extraction