COORDINATION (HYDRATION) OF RARE-EARTH IONS IN AQUEOUS CHLORIDE SOLUTIONS FROM X-RAY-DIFFRACTION .1. TBCL3, DYCL3, ERCL3, TMCL3, AND LUCL3

The rare earth aquo complex, [RE(H2O)8]3+, has been identified in concentrated (3.2-3.6 m) aqueous TbCl3, DyCl3, ErCl3, TmCl3, and LuCl3 solutions from x-ray diffraction measurements. The inner sphere water coordination of the rare earth ion was obtained from quantitative resolution of the radial distribution functions. In each solution the rare earth ion has eight water nearest neighbors with the average RE3+-H2O distances being 2.409, 2.396, 2.369, 2.358, and 2.338Å for TbCl 3, DyCl3, ErCl3, TmCl3, and LuCl3, respectively. The average RE3+⋯Cl - ion pair distances are near 4.8Å. © 1979 American Institute of Physics.