Poly[tetra­aqua-di-μ4-malonato-barium(II)cadmium(II)]

Ming-Lin Guo; Wen-Jun Gao; Cong-Cong Luo; Long Liu

doi:10.1107/S1600536810049780

. 2010 Dec 4;67(Pt 1):m23–m24. doi: 10.1107/S1600536810049780

Poly[tetraaqua-di-μ₄-malonato-barium(II)cadmium(II)]

Ming-Lin Guo ^a,^*, Wen-Jun Gao ^a, Cong-Cong Luo ^a, Long Liu ^a

PMCID: PMC3050201 PMID: 21522548

Abstract

In the title complex, [BaCd(C₃H₂O₄)₂(H₂O)₄]_n, the Ba^II atoms, located on crystallographic twofold axes, adopt slightly distorted square-antiprismatic coordination geometries, while the Cd^II atoms, which lie on crystallographic centres of symmetry, have a distorted octahedral coordination. Each malonate dianion binds two different Cd^II atoms and two different Ba^II atoms. This connectivity generates alternating layers along [100] in the structure, with one type containing Cd^II cations and malonate dianions, while the other is primarily composed of Ba^II ions and coordinated water molecules. The water molecules also participate in extensive O—H⋯O hydrogen bonding.

Related literature

For structural studies on the malonate dianion with its versatile coordination patterns, see: Delgado et al. (2004 ▶). For related structures, see Djeghri et al. (2005 ▶); Guo & Guo (2006 ▶).

Experimental

Crystal data

[BaCd(C₃H₂O₄)₂(H₂O)₄]
M _r = 525.90
Orthorhombic,
a = 18.809 (4) Å
b = 6.9224 (14) Å
c = 9.6849 (19) Å
V = 1261.0 (4) Å³
Z = 4
Mo Kα radiation
μ = 4.85 mm⁻¹
T = 294 K
0.24 × 0.20 × 0.10 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2000 ▶) T _min = 0.370, T _max = 0.662
5716 measured reflections
1103 independent reflections
978 reflections with I > 2σ(I)
R _int = 0.059

Refinement

R[F ² > 2σ(F ²)] = 0.060
wR(F ²) = 0.161
S = 1.06
1103 reflections
94 parameters
H-atom parameters constrained
Δρ_max = 1.94 e Å⁻³
Δρ_min = −1.24 e Å⁻³

Data collection: SMART (Bruker, 1997 ▶); cell refinement: SAINT (Bruker, 1997 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810049780/sj5064sup1.cif

e-67-00m23-sup1.cif^{(20.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810049780/sj5064Isup2.hkl

e-67-00m23-Isup2.hkl^{(54.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Ba1—O4ⁱ	2.794 (9)
Ba1—O6	2.809 (10)
Ba1—O4	2.854 (9)
Ba1—O5	2.877 (10)
Cd1—O2ⁱⁱ	2.227 (10)
Cd1—O3	2.227 (9)
Cd1—O1ⁱⁱⁱ	2.364 (8)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O6—H6B⋯O5ⁱⁱⁱ	0.87	2.08	2.893 (14)	157
O6—H6A⋯O1^iv	0.85	1.99	2.781 (13)	156
O5—H5B⋯O6ⁱ	0.87	2.19	2.919 (15)	141
O5—H5A⋯O2ⁱⁱ	0.84	2.01	2.810 (14)	159

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

We thank Tianjin Polytechnic University for financial support.

supplementary crystallographic information

Comment

The malonate dianion, with two neighboring carboxylate groups, is a very flexible ligand. Its basic coordination mode is as a chelate via two distal carboxylate oxygen atoms to form a six-membered ring and the coordinating ability of the nonchelating oxygen atoms makes the formation of polymeric networks possible (Djeghri et al., 2005; Guo & Guo, 2006). On the other hand, malonate can also coordinate in monodentate, chelated bidentate and bridging modes to create various molecular architectures (Delgado et al., 2004). Herein, we report the structure of the title heterobimetallic malonate complex, (I). It and the chemically similar complex poly[tetraaqua-di-mu4-malonato-barium(II)zinc(II)] (Guo & Guo, 2006) are isotypic.

The asymmetric unit in the structure of (I) comprises half a Ba^II cation, half a Cd^II cation, a complete malonate dianion defined by C1—C3/O1—O4 and two independent water molecules involving O5 and O6. Fig. 1 shows a symmetry-expanded view which displays the full coordination of the Ba²⁺ and Cd²⁺ centers. Selected geometric parameters are given in Table 1.

The Ba²⁺ cation, lying on a crystallographic twofold axis, is eight-coordinate, bonded to oxygen atoms of four different malonate groups and four water molecules with Ba—O distances ranging from 2.793 (9) to 2.878 (10) Å. The Ba polyhedra may be described as slightly distorted square antiprisms. They share edges to form chains propagating along c.

The Cd²⁺ cations, lie on crystallographic centres of symmetry, and have distorted octahedral coordination, with O2 and O3 of two bidentate malonate anions at the equatorial sites and two O1 atoms from two other malonate anions at the apical sites.

Also evident in Fig. 1 is the variability of the coordination modes of the malonate dianion with monodentate (O1), bidentate chelating (O2 and O3) and bridging (O4) bonding modes all present.

The structure as a whole consists of two distinct types of layer, both parallel to (100) and stacked alternately in the direction of a. The first of these (Fig. 2) is composed entirely of Cd^II ions and malonate dianions and occurs at x = 0 and 1/2. The other type of layer, type 2, alternating with the first and centred on x = 1/4 and 3/4 contains, primarily, the Ba ions and the water molecules. Two forms of connectivity occur within the type 2 layers. First of all O4 atoms on the surfaces of the type 1 layers create chains of edge sharing Ba polyhedra propagating along c and at the same time link the two types of layer and complete the three-dimensional connectivity of the structure. The interlayer connectivity is further enhanced by the hydrogen bonds of the form O5—H5A···O2^iv and O6—H6A···O1^vi given in Table 2.

Experimental

The title complex was prepared under continuous stirring with successive addition of malonic acid (0.43 g, 4 mmol), cadmium(II) chloride (0.37 g, 2 mmol) and Ba(OH)₂.8H₂O (0.63 g, 2 mmol) to distilled water (40 ml) at room temperature. After filtration, slow evaporation over a period of a week at room temperature provided colorless plate-like crystals of (I).