Crystal structure of potassium dihydroxyhexacarbonatedizirconate hexahydrate K6[Zr2(OH)2(CO3)6]�6H2O

Aqueous Chemistry of Zirconium(IV) in Carbonate Media

“…Recently, we have presented our investigation about the coordination mode of carbonate ions in [Zr(CO 3 ) 4 ] 4À in aqueous solution and the kinetic behavior of this complex [8]. We now have determined the nature and the stoichiometry of carbonatohydroxo complexes of Zr 4 by potentiometry, dialysis, and 13 C-and 17 O-NMR spectroscopy, and we suggest structures for these species.…”

“…4,b, the protonation of the two basicities of CO 3 2À is effective at pH 7.5 and 3.5 and requires 3 and 9 H equiv. In the presence of Zr 4 , the protonation curve is displaced to the left, and shows also two equivalence points at the same pH, but for 1 and 7 H equiv.…”

“…Our results can be easily compared to the behavior of [(UO 2 ) 3 (CO 3 ) 6 ] 6À [9], which showed only one broad peak at 215 ppm in its 17 O-NMR spectrum for its three bridging and three bidentate carbonato ligands. In Zr 4 , as well as in uranyl complexes, the broadness of the peak of coordinated carbonate ions may be due to quadrupolar relaxation and/or to a fast exchange process. 13 C-NMR Data.…”

“…We now have determined the nature and the stoichiometry of carbonatohydroxo complexes of Zr 4 by potentiometry, dialysis, and 13 C-and 17 O-NMR spectroscopy, and we suggest structures for these species.…”

“…Considering the hypothesis proposed earlier, the general mechanism in Eqn. 3 can be written, where the formation of [Zr(OH) 4 ] is concomitant with the apparition of a solid phase.…”