Lanthanide complexes with phosphine oxide and phosphonate ligands

The complexes LnL'(3).xH(2)O (4) and LnL "(3).xH(2)O (5) were obtained from the reaction of 2-(diphenylphosphinoyl)-2-phenylethenol [L'H, (1)], diethy l (2-oxo-1-phenyl)ethylphosphonate [L " H, (2)] and several lanthanide nitr ates (3). Two different procedures were applied: in methanol-water solution and potassium hydroxide (procedure A) or in anhydrous tetrahydrofuran and sodium (procedure B). The IR and NMR data prove the enolate structure of th e complexes and bidentate coordination of the metals by the ligands. On the basis of these spectral data, all complexes have a chelate structure. Only the diamagnetic lanthanum derivatives (4a and 5a) can be identified as mix tures of (Z)- and (E)-isomers by NMR spectroscopy. The coordinating power o f the phosphine oxide (1) is used to separate lanthanum ions from aqueous s olutions by liquid-liquid extraction.