Complexes of esters of ethylenediphosphonic acid with lanthanide nitrates—synthesis and structure^†

The lanthanide complexes L₂Ln(NO₃)₃ (3) and L′ ₃[Ln(NO₃)₃]₂ (5) (Stewart and Siddall III. J Inorg Nucl Chem 1971, 33, 2965–2970) were obtained, where L is the tetraethyl ester of ethylenediphosphonic acid (2), L′ is the tetraisopropyl ester of ethylenediphosphonic acid (4), and Ln is La, Ce, Sm, Eu, and Er. In extension of a former study, they were characterized additionally with NMR spectroscopy. In contrast to the compounds of type 3, the erbium complex of the ligand L is consistent with the formula L₃[Er(NO₃)₃]₂. The crystal structure of the complex 3a (Ln = La) is determined by single crystal X-ray diffraction. The complex is found to crystallize in the monoclinic space group C2/c with a = 15.1415(4) Å, b = 14.9749(4) Å, c = 18.3887(5) Å, β = 114.129(1)ˆ, T = 153 K, V = 3805.2(2) ų, Z = 4, ρ_calc = 1.622 g/cm³, R₁ = 0.023, R2w = 0.058, S = 1.08 for all 6823 reflections. The complex 3a consists of polymer chains with bridged bidentate phosphonate ligands. The lanthanum atom is coordinated by ten oxygen atoms, six of them from the three bidentate nitrate ions, and four from the two phosphonate ligands. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:36–46, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20188