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Communication

Structural and Kinetic Studies on Uranyl(V) Carbonate Complex Using ¹³C NMR Spectroscopy

Supporting Info

Koichiro Mizuoka,^† Ingmar Grenthe,^‡ and Yasuhisa Ikeda*^†

Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550, Japan, and Department of Chemistry, Royal Institute of Technology (KTH), S-10044 Stockholm, Sweden

Inorg. Chem., 2005, 44 (13), pp 4472–4474

DOI: 10.1021/ic050308x

Publication Date (Web): June 2, 2005

†

Tokyo Institute of Technology.

‡

Royal Institute of Technology (KTH).

To whom correspondence should be addressed. Tel and Fax: +81-3-5734-3061. E-mail: yikeda@nr.titech.ac.jp.

Abstract

We have measured ¹³C NMR spectra of uranyl(V) carbonate complex in D₂O solution containing 1.003 M Na₂¹³CO₃ at various temperatures. Two singlet signals corresponding to free and coordinated CO₃²^- were observed at 169.13 and 106.70 ppm, respectively. From the peak area ratio, the structure of the uranyl(V) carbonate complex was determined as [U^VO₂(CO₃)₃]⁵^-. Furthermore, kinetic analyses of the exchange reaction of free and coordinated CO₃²^- in [U^VO₂(CO₃)₃]⁵^- were carried out using ¹³C NMR line-broadening. As a result, the first-order rate constant at 298 K and the activation parameters for CO₃²^- exchange reaction in [U^VO₂(CO₃)₃]⁵^- were evaluated as 1.13 × 10³ s^-¹ and ΔH = 62.0 ± 0.7 kJ·mol^-¹, ΔS = 22 ± 3 J·mol^-¹·K^-¹, respectively. We suggest that the exchange follows a dissociative mechanism as in the corresponding [U^VIO₂(CO₃)₃]⁴^- complex.