Preparation of N,N-Dialkylcarbamato Lanthanide Complexes by Extraction of Lanthanide Ions from Aqueous Solution into Hydrocarbons

Lanthanides are easily extracted as N,N-dibutylcarbamato complexes from aqueous solutions of their chlorides into heptane solutions of dibutylamine saturated with CO2. The products are recovered in high yields and are soluble in hydrocarbons. The derivatives [Ln­(O2CNBu2)3]n [Ln = Nd (1), Eu (2), Tb (3)], [NH2Bu2]2[Ln4(CO3)­(O2CNBu2)12] [Ln = Tb (4), Sm (5), Eu (6)], and [Sm4(CO3)­(O2CNBu2)10], 7, have thus been obtained. The crystal and molecular structure of 4 has been solved; the samarium and europium complexes 5 and 6 were found to be isostructural. Mass spectra of the complexes 1–3, 4, and 7 (in MeCN/toluene) reveal that equilibria are present in solution. Compound 2 has been reacted in toluene with NHBz2 in the presence of CO2 affording [NH2Bz2]­[Eu­(O2CNBz2)4], 8, through a ligand exchange process. By thermal treatment, 8 afforded [Eu­(O2CNBz2)3]n, 9. With a similar procedure [Sm­(O2CNBz2)3]n, 10, was obtained from 5. According to the photoluminescence study carried out on solid samples of 2, 4, 5, 7, and 8, the metal centered f–f transitions represent the only effective way to induce lanthanide luminescence in these complexes.