Poly[[μ2-aqua-tetraaquadi-μ3-malonatonickel(II) strontium(II)] dihydrate]

Abstract

The unit-cell parameters for the title mixed-metal coordination polymer, {[NiSr(C3H2O4)2(H2O) 5]·2H2O}n, which is isostructural with its Co-containing analogue, were reported previously [Gil de Muro et al. (1999). Eur. J. Inorg. Chem. pp. 935-943]; the full crystal structure including a description of the hydrogen bonding is reported here. The Sr2+ ion is bonded to five O atoms from three different malonate dianions and four water molecules, displaying a distorted tricapped trigonal-prismatic coordination geometry. Two malonate dianions, two water molecules and one Ni2+ ion build up a dianionic [Ni(C3H2O4) 2(H2O)2]2- unit incorporating a slightly distorted NiO6 octahedron, which coordinates to three nearby Sr 2+ ions. This arrangement creates a metal-organic framework having a 20-membered ring with four Ni and six Sr atoms lying in the bc plane. The coordinated and uncoordinated water molecules are responsible for the formation of two D5 hydrogen-bonded water chains within the 20-membered ring and they are linked into an R4 water cluster via two bifurcated O - H⋯(O,O) links.