Jean-Claude Bunzli - Lanthanide-Nitrate Interaction in Anhydrous Acetonitrile and Coordination Numbers of the Lanthanide Ions - Ft-Ir Study

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  Bunzli,J.C.G., MilicicTang,A., Mabillard,C. Helvetica Chimica   Acta 1993 76 (3) 1292-1304

  Abstract: The interaction between lanthanide   ions Ln(III)(Ln = La, Nd, Sm-Dy, Er, Yb) and nitrate ions is   investigated by FT-IR spectroscopy in dilute anhydrous MeCN   solution. The work is performed for ratios R = [NO3-]t/[Ln(III)]t   ranging from 0 to 8 and for solutions generally 0.05 M in   Ln(III), prepared from anhydrous lanthanide perchlorates   Ln(ClO4)3. When nitrate is progressively added to the Ln(ClO4)3   solutions, the formation of [Ln(NO3)n](3-n)+ species is clearly   evidenced by the FT-IR spectra. All the NO3- ions are coordinated   and bidentate. A quantitative study was performed using the nu1   and nu6 vibrational modes for coordinated NO3- ions. The average   coordination numbers estimated for Nd, Eu, Th, and Er in   solutions of trinitrates arc 9.0, 9.1, 8.3, and 8.2, respectively   (+/- 0.3 unit). In presence of an excess NO-, these numbers   become 9.8, 10.2, 10.0, 9.8, 9.9, and 9.9 (+/- 0.3 unit) for La,   Nd, Eu, Tb, Er, and Yb, respectively. No hexanitrate species   forms under the experimental conditions used (R up to 8). The   structural aspect of the various nitrate species is also   investigated. In the pentanitrate species, all the ligands appear   to be equivalent, while large inequivalences are observed for   Ln(NO3)3 solutions. Since for the latter most of the absorption   bands assigned to nitrate vibrations contain several components,   a curve-fitting procedure has been used for decomposing the nu2,   nu4, and nu6 vibrations. There is a considerable difference   between Ln(III) ions, the nitrate inequivalences being larger in   the middle of the series

  Address (URL): WOS:A1993LC36500015