Synthetic, spectroscopic, and X-ray crystallographic studies on the uranyl(VI) complexes of the β-diketophenol ligands 1-(2-hydroxyphenyl)-1,3-butanedione and 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione

Article abstract of DOI:10.1016/S0020-1693(97)06094-5

The preparation of the mononuclear complexes [UO₂(HL¹)₂(MeOH)] and [UO₂(HL²)₂(EtOH)], the heterobinuclear complexes [UO₂Mn(L¹)₂(EtOH)] 1.5H₂O and [UO₂Mn(L²)₂(EtOH)] 2H₂O, and the oxo-ligand adducts [UO₂(HL¹)₂(Ph₃AsO) ] 2H₂O, [UO₂(HL²)₂(Ph₃PO)] and [UO₂(HL²)₂(Ph₃AsO)] (H₂L¹ = 1-(2-hydroxyphenyl)-3-butanedione and H₂L² = 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanedione) is described. The complexes have been characterized by a variety of physicochemical techniques and the crystal structures of [UO₂(HL¹)₂(EtOH)] and [UO₂(HL²)₂(EtOH)] EtOH determined. Crystals of the former are triclinic, space group P1, a = 8.076(1), b = 8.131 (1), c = 10.161 (1) A, α = 108.49(1), β = 112.26(1), γ = 89.89(1)° and Z = 1. The latter is also triclinic, space group P1, a = 12.184(3), b = 15.578(5), c = 9.035(2) A, α = 91.05(2), β = 103.20(2), γ = 73.21(2)° and Z = 2. Both complexes contain seven-coordinate uranium (VI) in a pentagonal bipyramidal geometry in which the two bidentate β-diketonato ligands and the coordinated ethanol make up the equatorial pentagonal plane. For the complex [UO₂(HL¹)₂(EtOH)] the HL¹ ligands are in a trans arrangement with respect to one another, whereas for the [UO₂(HL²)₂(EtOH)] EtOH complex the HL² ligands adopt a cis arrangement. However, in solution variable temperature ¹H NMR spectra indicate that the cis and trans isomers are in equilibrium for both complexes.