Uranyl ion complexes with aminoalcoholbis(phenolate) [O,N,O,O′] donor ligands

Abstract

The reaction between uranyl nitrate hexahydrate and phenolic ligand precursor N, N-bis(2-hydroxy-3,5-dimethylbenzyl)-2-aminoethanol (H 3L1) in acetonitrile without base affords the dinuclear uranyl complex [(UO 2) 2(H 2L1) 2(NO 3) 2] ( 1); in the presence of base, the mononuclear complex [UO 2(H 2L1) 2] · 2H 2O ( 2) is formed. Ligand N, N-bis(2-hydroxy-5- t-butyl-3-methylbenzyl)-2-aminoethanol (H 3L2) affords a uranyl complex of formula [UO 2(H 2L2) 2] · 2CH 3CN ( 3); ligand N, N-bis(2-hydroxy-3,5-dimethylbenzyl)-3-amino-1-propanol (H 3L3) affords a uranyl complex of formula [UO 2(H 2L3) 2] ( 4); whilst ligand N, N-bis(2-hydroxy-5- t-butyl-3-methylbenzyl)-3-amino-1-propanol (H 3L4), used as the hydrochloride, affords a uranyl complex of formula [UO 2(H 2L4) 2] ( 5). A solid complex with uranyl ion could not be formed using the ligand N, N-bis(2-hydroxy-3,5-di- t-butylbenzyl)-2-aminoethanol. The molecular structures of 1– 5 were verified by X-ray crystallography whereby it was ascertained that 1 is a dialkoxo-bridged dinuclear uranyl complex with a U to L ratio of 1:1. The other complexes 2– 5 form in a molar ratio of 1:2 (U to L) and bear similar mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands forming an equatorial plane and resulting in a centrosymmetric structure for the uranyl ion.