Crystal structure of (4-amino-3,5-di-chloro-pyridine-κN 1)dioxidobis(pentane-2,4-dionato-κ2 O,O')uranium(VI) methanol hemisolvate.

Abstract

Uran-yl(VI) complexes have been researched in many laboratories due to their relevance to actinide coordination chemistry and nuclear fuel reprocessing. The asymmetric unit of the title uranyl complex, [U(C₅H₇O₂)₂O₂(C₅H₄Cl₂N₂)]·0.5CH₃OH or [UO₂(acac)₂(4-amino-3,5-di-chloro-pyridine)]·0.5CH₃OH, contains two crystallographically independent uran-yl(VI) complex mol-ecules and one methanol solvent mol-ecule. Each U^VI atom adopts a UNO₆ penta-gonal-bipyramidal coordination geometry, in which two uranyl O atoms occupy the axial positions, whereas four O atoms from two chelating bidentate acac ligands and one N atom from a 4-amino-3,5-di-chloro-pyridine ligand define the equatorial plane. The U=O bond lengths are 1.757 (10) and 1.807 (11) Å for one independent mol-ecule and 1.752 (11) and 1.766 (11) Å for the other, while the U=O(acac) and U-N bond lengths lie in the ranges 2.302 (11)-2.384 (10) Å and 2.591 (13)-2.645 (13) Å, respectively. The bond lengths around the U atoms decrease in the order U-N > U-Oacac > U=O. The uranyl units are slightly bent, with O=U=O angles of 177.0 (5) and 176.5 (5)°. In the crystal, the methanol solvent mol-ecule is linked to the amino group in the coordinated ligand by an inter-molecular N-H⋯O hydrogen bond [N⋯O = 2.90 (2) Å], which is likely to contribute to the low-symmetry crystal arrangement.