Comparative investigation of the solution species [U(CO)] and the crystal structure of Na[U(CO)]12HO

Hennig, C.*; Ikeda, Atsushi  ; Emmerling, F.*; Kraus, W.*; Bernhard, G.*

The coordination of the limiting U(IV) carbonate species in aqueous solution was investigated by comparing its structure parameters with those of the complex preserved in a crystal structure. The U(IV) carbonate complex in the crystal structure was identified as a [U(CO)] anionic complex. This monomeric anion complex forms a network with charge compensating Na+ cations and HO ligands. U L3-edge EXAFS spectra were collected from the solid Na[U(CO)]12HO and the corresponding solution. The obtained data indicate the identity of the [U(CO)] complex in solid and solution states. The high negative charge of the [U(CO)] anionic complex is compensated by Na+ cations. In the solid state the Na+ cations form a bridging network between the [U(CO)] anion complex, while in the liquid state they seem to be located closer at the anionic complex anion.