Poly[[μ(2)-aqua-tetraaquadi-μ(3)-malonato-nickel(II)strontium(II)] dihydrate]

Abstract

The unit-cell parameters for the title mixed-metal coordination polymer, {[NiSr(C(3)H(2)O(4))(2)(H(2)O)(5)]·2H(2)O}(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 Sr(2+) ion is bonded to five O atoms from three different malonate dianions and four water mol-ecules, displaying a distorted tricapped trigonal-prismatic coordination geometry. Two malonate dianions, two water mol-ecules and one Ni(2+) ion build up a dianionic [Ni(C(3)H(2)O(4))(2)(H(2)O)(2)](2-) unit incorporating a slightly distorted NiO(6) octa-hedron, 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 mol-ecules 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.

Fig. 1.

A view of the structure of (I), showing the coordination environment for Sr and Ni atoms; displacement ellipsoids were drawn at the 30% probability level [Symmetry codes: (i) -x + 1, -y + 1, -z + 1; (ii) x, -y + 1/2, z + 1/2; (iii) -x + 2, -y + 1, -z + 1; (iv) x, -y + 1/2, z - 1/2].

Fig. 2.

The packing diagram of (I), viewed down the a axis, showing its 20-membered structure and water cluster in the direaction of bc plane.

Fig. 3.

The packing diagram of (I), showing hydrogen-bonding interactions between the [Ni(mal)2(H2O)2]2- dianions and water molecules, viewed down the c axis.