Structure and Properties of 2,2-Dihydroxymalonates of Trivalent Y, Lanthanides, Pu and Am

摘要

The M—O bond lengths in the lanthanide series show a well-known behaviour due to lanthanide contraction, including so-called "gadolinium break". All three bond lengths show a good linear correlation with Shannon ionic radii for Y~(3+) and Ln~(3+) ions with coordination number 9. Nevertheless, the slopes of these dependences are different (0.957(16) for OH-groups, 0.85(2) for carboxylate groups and 1.080(17) for water molecules) and differ from unity due to a layer nature of the structures. The ionic radii for Pu~(3+) and Am~(3+) with coordination number 9 are absent in the Shannon system of ionic radii. From our data, we can propose the values 1.172 and 1.156 A for Pu~(3+), and Am~(3+), respectively. In all crystals the structure is stabilized through extensive hydrogen bonding involving carboxylic and hydroxyl groups and water molecules.