Interaction of metal ions with humic-like models. Part 5. The crystal and molecular structure of diaquabis(2,6-dihydroxybenzoato)-dioxouranium(VI) octahydrate

Abstract

The crystal and molecular structure of the complex [UO 2(DHB) 2(H 2O) 2]·8H 2O (DHB = 2,6-di- hydroxybenzoato) has been determined from single- crystal X-ray analysis and refined to a final R value of 0.033 for 3620 observed reflections. The complex crystallizes in the monoclinic system, space group C2/ m, with a = 6.704(3), b = 20.171(6), c = 9.454(4) Å and Z = 2. The coordination about the uranyl group, which is linear, involves two bidentate carboxylate groups and two water molecules in trans positions giving rise to an irregular hexagonal bipyramid. Intra- molecular hydrogen bonds between phenolic and carboxylate groups forming six-membered rings allow the molecule to be nearly planar. Spectroscopic (IR, NMR and electronic absorption) data and thermal properties of the compound are also reported.