The Crystal and Molecular Structure of Heavy Lanthanoid(III) Chloroacetates in the Hydrated Form, [M3ClCH2CO2)9(H2O)4]n·nH2O (M=Gd, Dy, Er, and Yb)

The crystal and molecular structures of the chloroacetato complexes of gadolinium(III), erbium(III), and ytterbium(III) indicated in the title were determined by the single-crystal X-ray diffraction method. In addition to these three complexes, the isomorphous dysprosium(III) salt was also obtained. Their chemical composition, M3L9·5H2O (where M=Gd, Dy, Er, or Yb; HL=chloroacetic acid), is the same as that of the light lanthanoid(III) (La–Eu) chloroacetates, though the latter crystals are monoclinic. The cell constants of the ytterbium(III) salt, for example, are: triclinic, space group P1, a=13.278(10), b=13.624(6), c=12.067(4) Å α=96.62(3), β=100.68(5), γ=67.40(4)°, Z=2 (including 6 metal atoms). There are three kinds of crystallographically independent metal atoms; Yb(1), Yb(2), and Yb(3): Yb(1) and Yb(2) are octa-coordinated (square-antiprism geometry) and Yb(3) is ennea-coordinated (monocapped square-antiprism geometry). Two oxygen atoms around the last type of the metal atom are the more separated in the higher atomic-number lanthanoid(III) complex, while the other M–O bond lengths decrease, depending on the increase of the metal atomic number. The metal atoms are bridged by carboxylate ions in a chair form along the [111] axis, though in a way different from that of the light lanthanoid(III) complexes.