Protonated vinylidenediphosphonate of rare-earth elements

The preparation and properties of rare-earth element (Ln) compounds with vinylidenediphosphonic acid (CH 2 =C(PO 3 H 2 ) 2 (H 4 L) were described. The composition of these compounds is LnHL . nH 2 O, where n = 3.5 (La-Sm), 3 (Eu-Tm, Y), 4 (Yb, Lu), or 2 (Nd, Eu). The complexes were characterized by elemental analysis, X-ray powder diffraction, thermal analysis, and IR spectroscopy.