ABSTRACT
The large hypouranyl ion 1.102 forms with the same ligands probably considerably weaker complexes than either U4+ or Uq+, so that the formation of soluble U(V) species is unfavourable for a wide range of natural conditions. However, the reduction of U(VI) to U(IV) in reducing environments could proceed via the oxidation state V. As U(V) seems to be stabilized in the solid phase, we argue that U(V) might prove to be a significant transitional redox state of in the marine sedimentary cycle.