Structural studies of lanthanide nitrate--dimethyl--diphenylpyridine-2,6-dicarboxyamide complexes

Fujiwara, Asako ; Nakano, Yoshiharu*; Yaita, Tsuyoshi; Okuno, Kenji*

The tridentate ligand -dimethyl--diphenylpyridine-2,6-dicarboxyamide (DMDPhPDA) and the corresponding lanthanum complex [La(NO)(DMDPhPDA)] have been prepared and structurally characterised. In the lanthanum complex, two DMDPhPDA molecules coordinated to La(III) in a tridentate fashion and to three nitrate ions in a bidentate fashion make the lanthanum atom 12-coordinate. The stability constants determined by spectrophotometric titration suggest that [Ln(DMDPhPDA)] is the primary product in nitrate media and [Ln(DMDPhPDA)] is difficult to form. However, [Ln(DMDPhPDA)] could not be distinguished in C NMR spectra. The C NMR titration results imply that a fast ligand exchange process takes place.