Zigzag stacking of Ni(S2C2O2)2 2- entities in the barium bis(dithiooxalato) nickelate(II). Structural relationships with 1—D alkali analogs and conductivity properties

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Abstract
BaNi(S2C2O2)2 ·6 H2O crystallizes in the orthorombic system (space group P212121). The cell-constants are: a = 11.287(1)Å, b = 20.927(2) Å, c = 6.729(2) Å. The crystal structure has been determined using X-ray single crystal techniques and refined by full-matrix least-squares calculations to R = 0.034. It is of the one-dimensional type, consisting of flat Ni(S2C2O2)2 2- anions quite perpendicular to the direction of the c axis and stacked in a zigzag way along one of the twofold screw axis parallel to that direction, with the Ba2+ cations and water molecules filling the tunnels between the anionic columns. The anionic stacking differs from the “rooftile-like” type observed in the one-dimensional alkali derivatives of the anion Ni(S2C2O2)2 2- previously described. The room temperature powder electrical conductivity is 10-12 Ω -1 cm-1 for the barium salt, whereas it ranges from 10-9 to 10-6 Ω -1 cm-1, according to the cation, in the onedimensional alkali derivatives. These differences can be related to the different geometries of anionic stackings.