Direct 1H, 13C, and 15N NMR Study of Lanthanum(III), Thulium(III), and Ytterbium(III) Complex Formation with Nitrate and Isothiocyanate

摘要

An 1H, 13C, and 15N NMR study has been completed for the complexes of La(III), Tm(III), and Yb(III) with nitrate and isothiocyanate in aqueous solvent mixtures. Signals for four complexes are observed for both the Tm3+–NO3 − and Yb3+–NO3 − solutions, with the species identified as the mono-, di-, tetra-, and either the penta - or hexanitrato. These results are consistent with those determined for the nitrate complexes of the Ce(III)–Eu(III) metal ions. The chemical shifts for the Tm(III) and Yb(III) nitrate complexes indicate a pseudocontact binding mechanism prevails. The complexes of diamagnetic La(III) with NO3 − produce three signals in the 15NO3 − spectra, with assignments paralleling those observed with the paramagnetic lanthanides. Three complexes are formed in the La3+–NCS− solutions, with signals assigned to the mono-, di-, and triisothiocyanato species.