A Direct Carbon-13 and Nitrogen-15 NMR Study of Praseodymium(III)- and Neodymium(III)-Isothiocyanate Complex Formation in Aqueous Solvent Mixtures.

Autor: Fratiello, Anthony, Kubo-Anderson, Vicki, Lee, Rebecca, Patrick, Marquis, Perrigan, Richard, Porras, Tanya, Sharp, Amy, Wong, Kenneth
Zdroj: Journal of Solution Chemistry; Jan2001, Vol. 30 Issue 1, p77-97, 21p
Abstrakt: Multinuclear magnetic resonance spectroscopic studies of the trivalent lanthanide complexes with isothiocyanate have been completed for the praseodymium(III) and neodymium(III) ions. In water–acetone–Freon mixtures, at temperatures low enough to slow ligand exchange, usually −85 to −125°C for isothiocyanate, separate carbon-13 and nitrogen-15 NMR signals can be observed for free anion and NCS- in each metal–ion complex. For both metal ions, 15N NMR signals are observed for four complexes, displaced about +1500 ppm downfield from free NCS- for Pr3+ and about +2000 ppm for Nd3+. In the 13C NMR spectra, only three peaks are observed for the complexes of both metal anions, with signal overlap obscuring the resonance for the fourth complex. However, the metal ion coordination numbers, obtained by integration of the resonance signals, are comparable in the 15N and 13C spectra, approaching a maximum value of about 3. These spectral data indicate the formation of Ln(NCS)2+ through Ln(NCS) occurs for both lanthanides in these solvent systems, a result also observed previously for Ce3+, Sm3+, and Eu3+ in our laboratory. Attempts to study these complexes in water–methanol were unsuccessful, due to the inability to achieve low enough temperatures to slow ligand exchange sufficiently. Results for NCS- and Cl- competitive-binding studies by 35Cl NMR for both metal ions will also be described. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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