Uranium complexes of cyclic O,O-bidentate ligands with the P–N–P backbone

The formation of uranium complexes of novel ligands belonging to phosphorylated 2-oxo-1,2-azaphospholane series, namely 2-ethoxy-1-diethoxyphosphoryl-2-oxo-1,2λ5-azaphospholane (1a) and both individual R∗,R∗- and R∗,S∗-diastereomers of the related 2-oxo-2-phenyl-1,2λ5-azaphospholanes 1b,c with different surrounding at the exocyclic phosphorus atom, has been studied. The structures of the complexes of ML composition obtained in the reaction with uranyl nitrate in 1:1 ratio were found to depend on the difference in donor properties of the oxygen atom of endo- and exocyclic phosphoryl groups. The ligand 1a possessing the greater difference, serves as O-monodentate one with metal–oxygen bonding via the endocyclic P O function while both isomers of 1b,c coordinate to uranyl cation in a O,O-bidentate fashion. In solutions the ML complexes reacted with air oxygen to afford (μ2-peroxo)-bridged uranium complexes [{UO2(L)NO3}2(μ2-O2)] which structures were confirmed by X-ray crystallography data.