CRYSTAL-STRUCTURES OF PR(OH)3, EU(OH)3 AND TM(OH)3

The crystal structures of Pr(OH)3, Eu(OH)3 and Tm(OH)3 have been determined from single-crystal, X-ray diffraction data. The hexagonal form of these lanthanide trihydroxides crystallizes in the space group P63/m(C6h2) with two formula units per unit cell. The respective lattice constants for the trihydroxides of Pr, Er and Tm are a0 = 6.456(1), 6.352(1), and 6.221(1) A ̊and c0 = 3.769(1), 3.653(1), and 3.503(2) A ̊. The metal atom of each is 9-coordinate with two unique MO bond distances and three independent OO bond distances. These isotypic compounds have been refined to conventional residual index values of 0.0320, 0.0280 and 0.0199, respectively. Fluorescence and IR data were collected on each of the isomorphous compounds. Refined parameters from this investigation have been added to earlier studies on structural trends in the lanthanide trihydroxides. © 1979.