Synthesis and structure of AUO2(n-C3H7COO)3 (A = Rb or Cs) and RbUO2(n-C4H9COO)3

With the aim of exploring the effect of the counter ion and the length of the alkyl chain on crystal structures of tris(monocarboxylato)uranylates of alkali metals, all the known to date data were systematized and three novel butyrate and valerate complexes of the uranyl ion were prepared and characterized using X-ray crystallography and IR spectroscopy. The novel compounds have the AUO2(n-C3H7COO)3 (А = Rb (I) or Cs (II)) and RbUO2(n-C4H9COO)3 (III) composition. The majority of compounds with the A[UO2L3] composition (A = Na+, K+, Rb+ or Cs+; L = acetate, acrylate, propionate, butyrate and valerate) crystallize in chiral space groups. Although the main structural units of these complexes are mononuclear anionic tris(monocarboxylato)uranylate(VI) complexes with a hexagonal bipyramidal geometry of the uranium(VI) atom, the coordination polyhedron of the alkali cation and the crystal symmetry are strongly affected by the ratio between the cation radius and the length of the alkyl chain.

Graphical abstractAll known tris(monocarboxylato)uranylates of alkali metals were systematized. The effect of the counter ion A and the length of the alkyl chain of the carboxylate ligand L on the crystal structure of the AUO2L3·nH2O complexes was explored. Three novel butyrate and valerate complexes of the uranyl ion were characterized using X-ray crystallography and FTIR spectroscopy.Figure optionsDownload full-size imageDownload as PowerPoint slide