Structure of potassium sodium orthoperiodate(VII) tetrahydrate

K2Na[H2IO6].4H2O, Mr=398.17, triclinic, Panti 1, a=6.7201 (5), b=7.3601 (4), c=10.7671 (6) A, α=97.607 (5), β=108.002 (5), γ=93.935 (6)0, V=498.62 A3, Z=2, Dm=2.70, Dx=2.652 Mg m-3, λ(Mo Kα)=0.71073 A, μ=40.838 cm-1, F(000)=384, T=295 K, R=0.0184 for 5751 observed unique reflections. The [H2IO6]3- anion has octahedral geometry, the OH groups are next to each other and the I-OH bonds are on average 0.14 (1) A longer than the I-O bonds. The structure consists of (H2O)4Na[μ-(OH)2]IO4 double octahedra, which are linked by hydrogen bonds of medium strength, and two independent potassium ions. The coordination polyhedra of the potassium ions are trigonal prismatic and very irregular with coordination numbers 6 and 9, respectively. (orig.)