VORONOI-DIRICHLET POLYHEDRA OF URANIUM ATOMS AND 18-ELECTRON RULE IN CARBONATE-CONTAINING URANYL COMPLEXES

In terms of a model of interatomic interactions that considers crystal structure as Voronoi-Dirichlet subdivision, the electron donor charac teristics of carbonate ions are determined, and the corelation between the composition and structure of known carbonate-containing uranyl co mplexes is analyzed. It is electron-donor Ligand properties that mainl y affect the composition and properties of stable complexes formed in similar aqueous salt systems containing uranyl ions, carbonate or nitr ate ions, and water molecules. In particular, in the UO22+-CO32--H2O s ystem the [UO2(CO3)(3)](4-) containing uranium atom with 18-electron ( N-U = 18) valence shell. is the most stable. In the UO22+-NO3--H2O sys tem the most stable complex is [UO2(NO3)(2) . 2E(2)O] (N-U = 17.8), wh ereas any other uranyl complexes [including [UO2(NO3)(3)](-) (N-U = 17 .1)] are unstable and readily decompose in aqueous solutions.