No abstract

The X-ray scattering from moderately concentrated dioxouranium(VI) carbonate solutions with the major part of uranium bound in the trinuclear complex (U02)3(C03)66" has been measured. A model for the structure of this complex consistent with the scattering data and compatible with 13C NMR data is suggested. The complex is triangular with a U-U distance of 4.946 (5) A. There are two sets of coordinated carbonate ions, three bridging and three terminal ones. The latter are bonded through two oxygens to uranium. The bridges are formed through bidentate coordination of the carbonate ion to two uranium atoms. The overall symmetry of the complex is close to Dih, and each uranium(VI) has an approximately hexagonal-bipyramidal coordination geometry, similar to those found in e.g. U02C03(s) and K4[U02(C03)3](s). The 13C NMR chemical shifts for the two types of carbonate ions in the complex have been determined to be 168.7 and 167.3 ppm, respectively, from Me4Si.

No abstract