Structure and dynamics in the complex ion (UO2)(2)(CO3)(OH)(3)(-)

QC 20100525
The structure and ligand exchange dynamics of the ternary complex (UO2)(2)(CO3)(OH)(3)(-) have been investigated by EXAFS and NMR spectroscopy. Very broad signals can be observed in both the C-13 and the O-17 NMR spectra. The EXAFS data show the presence of 1.3 +/- 0.3 short uranium-oxygen distances at 2.26 Angstrom, consistent with single bonded hydroxide and 3.9 +/- 0.6 distances at 2.47 Angstrom for the other ligands in the first co-ordination shell. There is also evidence for a U ... U interaction at 3.90 Angstrom. Based on the EXAFS and NMR data we suggest the presence of three isomers with different bridge arrangements, the dominant one, C, contains 80% of the uranium and the minor ones A and B, 5 and 15%, respectively. The ligand exchange reactions between these isomers are slow. The NMR data indicate that the main reactions involve intramolecular exchanges between isomers with different positions of the non-bridging ligands in A, B and C. We suggest that these take place through water exchange as discussed earlier for other ternary uranium(VI) complexes.

Ingår i:Journal of the Chemical Society. Dalton Transactions: Royal Society of Chemistry (RSC):18, s. 3158-31611472-77731364-54471470-479X

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