Dioxouranium(Vl) complexes with pentadentate bases containing acetal groups

Abstract

The new ligands [(OCH 3) 2CHHOC 6H 2ClCH N(CH 2) 2] 2NH, H 2(NAC), and [(OCH 3) 2CHHOC 6 H 2ClCHN(CH 2) 2] 2S, H 2(SAC), and the related uranyl complexes [UO 2(NAC)] and [UO 2(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. [UO 2(SAC)] is monoclinic, space group P2 1/ n, with a = 20.591(5), b = 11.948(8), c = 11.780(8) Å, β = 90.11(3)°; D c = 1.86 g cm −3 for Z = 4. The structure was refined to the conventional R of 4.6%. [UO 2(NAC)] is tetragonal, space group P4 12 12, with a = 12.605(8) and c = 17.801(5) Å; D c = 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 UO 2 2+ leading to seven-coordinated uranium in a distorted bipyramidal coordination geometry. Selected bond distances for [UO 2(SAC)] are: UO (uranyl) 1.77 Å (mean), UO (ligand) 2.22 Å (mean), UN 2.61 Å, (mean) and US 3.003(3) Å. In [UO 2- (NAC)] the corresponding values are: UO (uranyl) 1.72 Å, UO (ligand) 2.21 Å (mean), UN 2.56 Å, and UNH 2.60 Å.