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)], diethyl (2-oxo-1-phenyl)ethylphosphonate [L " H, (2)] and several lanthanide nitrates (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 the 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 mixtures of (Z)- and (E)-isomers by NMR spectroscopy. The coordinating power of the phosphine oxide (1) is used to separate lanthanum ions from aqueous solutions by liquid-liquid extraction.