The preparation of the mononuclear complexes [UO 2 (HL 1 ) 2 (MeOH)] and [UO 2 (HL 2 ) 2 (EtOH)], the heterobinuclear complexes [UO 2 Mn(L 1 ) 2 (EtOH)] 1.5H 2 O and [UO 2 Mn(L 2 ) 2 (EtOH)] 2H 2 O, and the oxo-ligand adducts [UO 2 (HL 1 ) 2 (Ph 3 AsO)] 2H 2 O, [UO 2 (HL 2 ) 2 (Ph 3 PO)] and [UO 2 (HL 2 ) 2 (Ph 3 AsO)] (H 2 L 1 = 1-(2-hydroxyphenyl)-3-butanedione and H 2 L 2 = 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 [UO 2 (HL 1 ) 2 (EtOH)] and [UO 2 (HL 2 ) 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) 9, 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) 9, 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 [UO 2 (HL 1 ) 2 (EtOH)] the HL 1 ligands are in a trans arrangement with respect to one another, whereas for the [UO 2 (HL 2 ) 2 (EtOH)] EtOH complex the HL 2 ligands adopt a cis arrangement. However, in solution variable temperature 1 H NMR spectra indicate that the cis and trans isomers are in equilibrium for both complexes.