Synthesis and properties of scandium, yttrium and lanthanum periodates. Crystal structures of Y(H2O)3{IO4(OH)2} and Y(H2O)2(IO3)3

The reaction of periodic acid or alkali-metal periodates with aqueous solutions of scandium, yttrium or lanthanum salts formed white M(H2O)3{IO4(OH)2} (M=Sc, Y or La). The compounds are insoluble in water, but dissolve in hot aqueous H5IO6 or mineral acids. They were characterised by analysis, IR, UV–Vis spectroscopy and TGA. The X-ray crystal structure of Y(H2O)3{IO4(OH)2} shows the presence of octahedral IO6 (IO 1.840(4)–1.943(4) Å) and eight-coordinate YO8 (YO 2.321(5)–2.475(4) Å) residues linked via edge sharing into chains. The solution chemistry of [M(H2O)n]3+ in the presence of H5IO6 has been partially explored by 45Sc, 89Y and 139La NMR spectroscopy. Attempts to isolate periodate complexes with different stoichiometries have been unsuccessful. Crystals of the iodate complex Y(H2O)2(IO3)3 were also obtained and the X-ray crystal structure shows the expected pyramidal IO3 − groups and eight-coordinate Y (YO 2.290(5)–2.457(5) Å).