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Updated: Sep 24, 2025

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Complexation and bonding studies on [Ru(NO)(H2O)5]3+ with nitrate ions by using density functional theory calculation
Akane Kato1, Masashi Kaneko2, Satoru Nakashima1,3
1Graduate School of Advanced Science and Engineering, Hiroshima University 1-3-1, Kagamiyama Higashi-Hiroshima Hiroshima 739-8526 Japan.
Abstract:
Complexation reactions of ruthenium-nitrosyl complexes in HNO3 solution were investigated by density functional theory (DFT) calculations in order to predict the stability of Ru species in high-level radioactive liquid waste (HLLW) solution. The equilibrium structure of [Ru(NO)(NO3)3(H2O)2] obtained by DFT calculations reproduced the experimental Ru-ligand bond lengths and IR frequencies reported previously. Comparison of the Gibbs energies among the geometrical isomers for [Ru(NO)(NO3) (H2O)5- ](3- revealed that the complexation reactions of the ruthenium-nitrosyl complexes with NO3 - proceed via the NO3 - coordination to the equatorial plane toward the Ru-NO axis. We also estimated Gibbs energy differences on the stepwise complexation reactions to succeed in reproducing the fraction of Ru-NO species in 6 M HNO3 solution, such as in HLLW, by considering the association energy between the Ru-NO species and the substituting ligands. Electron density analyses of the complexes indicated that the strength of the Ru-ligand coordination bonds depends on the stability of the Ru species and the Ru complex without NO3 - at the axial position is more stable than that with NO3 -, which might be attributed to the difference in the trans influence between H2O and NO3 -. Finally, we demonstrated the complexation kinetics in the reactions x = 1 → x = 2. The present study is expected to enable us to model the precise complexation reactions of platinum-group metals in HNO3 solution.
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