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Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
Synthesis, structure, and 15N NMR studies of paramagnetic lanthanide complexes obtained by reduction of dinitrogen
William J Evans1, Daniel B Rego, Joseph W Ziller
1Department of Chemistry, University of California, Irvine, CA 92697-2025, USA.
Abstract:
The recently discovered LnZ3/M and LnZ2Z'/M methods of reduction (Ln = lanthanide; M = alkali metal; Z, Z' = monoanionic ligands that allow these combinations to generate "LnZ2" reactivity) have been applied to provide the first crystallographically characterized dinitrogen complexes of cerium, [C5Me5)2(THF)Ce]2(mu-eta2.eta2-N2) and [(C5Me4H)2(THF)Ce]2(mu-eta2.eta2-N2), so that the utility of 15N NMR spectroscopy with paramagnetic lanthanides could be determined. [(C5Me5)2(THF)Pr]2(mu-eta2.eta2-N2) and [(C5Me4H)2(THF)Pr]2(mu-eta2.eta2-N2) were also synthesized, crystallographically characterized, and studied by 15N NMR methods. The data were compared to those of [(C5Me5)2Sm]2(mu-eta2.eta2-N2). [(C5Me5)2(THF)Ce]2(mu-eta2.eta2-N2) and [(C5Me5)2(THF)Pr]2(mu-eta2.eta2-N2) are unlike their (C5Me4H)1- analogs in that the solvating THF molecules are cis rather than trans. Structural information on precursors, (C5Me4H)3Ce, (C5Me4H)3Pr, and the oxidation product [(C5Me5)2Ce]2(mu-O) is also presented.
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