DIOXOURANIUM(VI) COMPLEXES WITH PENTADENTATE BASES CONTAINING ACETAL GROUPS

The new ligands [(OCH3)2CHHOC6H2ClCH N(CH2)2]2NH, H2(NAC), and [(OCH3)2CHHOC6 H2ClCHN(CH2)2]2S, H2(SAC), and the related uranyl complexes [UO2(NAC)] and [UO2(SAC)] have been prepared and characterized by infrared, 1H and 13C NMR and electronic spectroscopy. Thermogravimetric and mass spectrometry data are also reported. The crystal structures of the complexes have been determined by X-ray crystallography. [UO2(SAC)] is monoclinic, space group P21/n, with a = 20.591(5), b = 11.948(8), c = 11.780(8) Å, β = 90.11(3)°; Dc = 1.86 g cm-3 for Z = 4. The structure was refined to the conventional R of 4.6%. [UO2(NAC)] is tetragonal, space group P41212, with a = 12.605(8) and c = 17.801(5) Å; Dc = 1.87 g cm-3 for Z = 4. The structure was refined to the conventional R of 5.7%. In both compounds the pentadentate dianionic ligand binds equatorially to UO22+ leading to seven-coordinated uranium in a distorted bipyramidal coordination geometry. Selected bond distances for [UO2(SAC)] are: UO (uranyl) 1.77 Å (mean), UO (ligand) 2.22 Å (mean), UN 2.61 Å, (mean) and US 3.003(3) Å. In [UO2- (NAC)] the corresponding values are: UO (uranyl) 1.72 Å, UO (ligand) 2.21 Å (mean), UN 2.56 Å, and UNH 2.60 Å. © 1987.