Send to:

Choose Destination
See comment in PubMed Commons below
Dalton Trans. 2013 Sep 28;42(36):13101-11. doi: 10.1039/c3dt51191j. Epub 2013 Jul 22.

Uranyl-halide complexation in N,N-dimethylformamide: halide coordination trend manifests hardness of [UO2]2+.

Author information

  • 1Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, 152-8550 Tokyo, Japan.


Complexation of [UO2](2+) with Cl(-), Br(-), and I(-) in N,N-dimethylformamide (DMF) was studied by UV-vis absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) to clearly differentiate halide coordination strengths to [UO2](2+). In the Cl(-) system, it was clarified that the Cl(-) coordination to [UO2](2+) in DMF proceeds almost quantitatively. The coordination number of Cl(-) almost quantitatively increases up to 4, i.e., the limiting complex is [UO2Cl4](2-). Logarithmic gross stability constants of [UO2Cl(x)](2-x) (x = 1-4) were evaluated as log β1 = 9.67, log β2 = 15.49, log β3 = 19.89, and log β4 = 24.63 from UV-vis titration experiments. The EXAFS results well demonstrated not only the Cl(-) coordination, but also the DMF solvation in the equatorial plane of [UO2](2+). The interaction of Br(-) and I(-) with [UO2](2+) in DMF was also investigated. As a result, the Br(-) coordination to [UO2](2+) stops at the second step, i.e., only [UO2Br](+) and UO2Br2 were observed. The molecular structure of each occurring species was confirmed by EXAFS. The evaluated log βx values of [UO2Br(x)](2-x) (x = 1, 2) are 3.45 and 5.42, respectively. The much smaller log βx than those of [UO2Cl(x)](2-x) indicates that Br(-) is a much weaker ligand to [UO2](2+) than Cl(-). The EXAFS experiments revealed that the presence of I(-) in the test solution does not modify any coordination structure around [UO2](2+). Thus, I(-) does not form any stable [UO2](2+) complexes in DMF. Consequently, the stability of the halido complexes of [UO2](2+) in DMF is exactly in line with the hardness order of halides.

PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Royal Society of Chemistry
    Loading ...
    Write to the Help Desk