Isolation of a Star‐Shaped Uranium(V/VI) Cluster from the Anaerobic Photochemical Reduction of Uranyl(VI)

Abstract

Actinide oxo clusters are an important class of compounds due to their impact on actinide migration in the environment. The photolytic reduction of uranyl(VI) has potential application in catalysis and spent nuclear fuel reprocessing, but the intermediate species involved in this reduction have not yet been elucidated. Here we show that the photolysis of partially hydrated uranyl(VI) in anaerobic conditions leads to the reduction of uranyl(VI), and to the incorporation of the resulting UV species into the stable mixed‐valent star‐shaped UVI/UV oxo cluster [U(UO2)5(μ3‐O)5(PhCOO)5(Py)7] (1). This cluster is only the second example of a UVI/UV cluster and the first one associating uranyl groups to a non‐uranyl(V) center. The UV center in 1 is stable, while the reaction of uranyl(V) iodide with potassium benzoate leads to immediate disproportionation and formation of the U12IVU4VO24 cluster {[K(Py)2]2[K(Py)]2[U16O24(PhCOO)24(Py)2]} (5).

Recent advances in uranium-containing polyoxometalates

“…21a and b). 128 The photolytic reduction of uranyl resulted in these mixed-valence U-oxo-clusters. Two similar mixed-valence U-oxo-clusters, [U(UO 2 ) 5 (μ 3 -O) 5 (PhCOO) 5 (Py) 7 ] and [U(UO 2 ) 5 (μ 3 -O) 5 (PhCOO) 5 (Py) 7 ] [UO 2 (PhCOO) 2 (Py) 2 ]•2Py, were synthesized using a photolysis procedure with UO 2 (NO 3 ) 2 in pyridine and the vapor diffusion of hexane into the pyridine reaction mixture.…”