Lanthanide complexes with a chelating methylenediphosphonate

Reaction of lanthanide (Ln) triflates with tetrakis(O-isopropyl)methylenediphosphonate (L) in a 2:1 ratio afforded [Ln(L)2(OTf)2(OH2)2](OTf). In the crystal structure (Ln = Nd), the 8-coordinated metal atom is chelated by the phosphoryl groups of the two phosphonate ligands, and only bonded to two monodentate triflates. This is in contrast with [Ln(L)2(NO3)2](CH3CN)2 (Ln = Ce, Pr, Nd) where all nitrates are bonded and bidentate. When the L:Ln ratio was increased to 4:1, [Ln(L)4](OTf)3(CH3CN)3 was obtained (Ln = La), in which the triflates are no longer bonded to the metal.