STRUCTURAL REFINEMENT OF LACO(CN)6.5H2O

Lanthanum hexacyanocobaltate pentahydrate, LaCo(CN)6·5H2O, crystallizes in a hexagonal unit cell, space group P63/m (C6h2, No. 176), with a0 = 7.507(2) A ̊ and c0 = 14.343(4) A ̊. Single crystal X-ray diffraction data have been collected on an Enraf Nonius Cad-4 automated diffractometer, complete to 2θ = 70°. The final least-squares refinement based on 533 independent reflections yields a residual index value of 0.039. The calculated density for two molecules in the unit cell is 2.106 g-cm-3 [ρ{variant}obs = 2.094(7) g-cm-3]. The trivalent lanthanum metal atoms are linked to the cobalt atoms by cyanide bridging. Three of the five water molecules are strongly coordinated and two are uncoordinated occupying holes in the structure along the threefold axis. Dehydration, fluorescence, and spectroscopic analyses gave also been done on single crystals of LaCo(CN)6·5H2O. The important bond lengths are: LaN = 2.616 Å; CoC = 1.887 Å; La-0(2) = 2.602 Å; and CN = 1.156 Å. © 1979.