Poly[[tetra­aquabis­(μ-hydroxy­acetato-κ4 O 1,O 2:O 1,O 1′)-μ2-sulfato-κ2 O:O′-dicadmium(II)] monohydrate]

Urszula Rychlewska; Beata Warzajtis; Mirjana Dj Dimitrijević; Nenad S Draskovic; Miloš I Djuran

doi:10.1107/S1600536809017255

. 2009 May 14;65(Pt 6):m648–m649. doi: 10.1107/S1600536809017255

Poly[[tetraaquabis(μ-hydroxyacetato-κ⁴ O ¹,O ²:O ¹,O ^1′)-μ₂-sulfato-κ² O:O′-dicadmium(II)] monohydrate]

Urszula Rychlewska ^a,^*, Beata Warzajtis ^a, Mirjana Dj Dimitrijević ^b, Nenad S Draskovic ^b, Miloš I Djuran ^b

PMCID: PMC2969722 PMID: 21583014

Abstract

The title compound, {[Cd₂(C₂H₃O₃)₂(SO₄)(H₂O)₄]·H₂O}_n, was obtained unintentionally in a transmetallation reaction. The crystal structure contains a two-dimensional metal–organic framework based on Cd^II–(μ-hydroxyacetato-κ⁴ O ¹,O ²:O ¹,O ^1′)–Cd^II zigzag chains joined together by bridging SO₄ anions. The resulting layers are shifted with respect to each other and are stacked along the c axis. Their construction is supported by hydrogen bonds between water molecules and between water molecules and carboxylate or sulfate groups. Neighbouring layers are bridged by hydrogen bonds between the hydroxyl substituent and a sulfate anion. The sulfate anion and solvent water molecule are located on twofold axes. The results demonstrate that care must be taken when preparing ethylenediaminetetraacetic acid-type complexes by transmetallation, in order to avoid precipitation of metal complexes with the α-hydroxyacetate ligand.

Related literature

For examples of the successful application of transmetallation reactions in the synthesis of metal(II) complexes with hexadentate 1,3-propanediaminetetraacetate and 1,4-butanediaminetetraacetate ligands, see: Radanović et al. (2003 ▶, 2004 ▶, 2007 ▶); Rychlewska et al. (2000 ▶, 2005 ▶, 2007 ▶).

Experimental

Crystal data

[Cd₂(C₂H₃O₃)₂(SO₄)(H₂O)₄]·H₂O
M _r = 561.03
Monoclinic,
a = 13.5750 (3) Å
b = 8.5777 (1)
c = 13.7734 (3) Å
β = 107.528 (2)°
V = 1529.34 (5) Å³
Z = 4
Mo Kα radiation
μ = 2.99 mm⁻¹
T = 295 K
0.30 × 0.30 × 0.20 mm

Data collection

Kuma KM4 CCD κ-geometry diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007 ▶) T _min = 0.388, T _max = 0.550
8842 measured reflections
1710 independent reflections
1602 reflections with I > 2σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.015
wR(F ²) = 0.038
S = 1.13
1710 reflections
102 parameters
H-atom parameters constrained
Δρ_max = 0.46 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2007 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2007 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS86 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP (Siemens, 1989 ▶) and Mercury (Bruno et al., 2002 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809017255/gk2209sup1.cif

e-65-0m648-sup1.cif^{(16.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809017255/gk2209Isup2.hkl

e-65-0m648-Isup2.hkl^{(84.3KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Cd1—O1	2.3584 (14)
Cd1—O2	2.3013 (14)
Cd1—O4	2.2386 (16)
Cd1—O1W	2.2731 (15)
Cd1—O2W	2.3245 (14)
Cd1—O2ⁱ	2.5937 (14)
Cd1—O3ⁱ	2.3379 (17)

Open in a new tab

Symmetry code: (i) Inline graphic .

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1W—H1W⋯O2Wⁱⁱ	0.85	1.94	2.784 (2)	170
O1W—H2w⋯O3ⁱⁱⁱ	0.85	1.88	2.723 (2)	172
O2W—H3W⋯O3W	0.85	1.88	2.720 (2)	172
O2W—H4W⋯O5ⁱ	0.85	1.82	2.648 (2)	162
O1—H1O⋯O5^iv	0.85	1.81	2.659 (2)	175
O3W—H5W⋯O4^v	0.85	2.25	2.813 (3)	124

Open in a new tab

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

Acknowledgments

This work was funded in part by the Ministry of Science and Technological Development of the Republic of Serbia (Project No. 142008). The authors are grateful to Dr Dušanka D. Radanović (Institute of Chemistry, Technology and Metallurgy, University of Belgrade) for her valuable suggestions.

supplementary crystallographic information

Comment

Research concerning metal–organic frameworks (MOF) has recently become important due to their potential application in a number of areas, including gas storage and catalysis. Prominent in this class of materials are frameworks that involve α-hydroxycarboxylate ligands spanning network nodes. We have recently obtained one such MOF by serendipity, when trying to synthesize cadmium(II) homometallic complex with 1,4-bdta ligand (1,4-bdta stands for 1,4-butanediaminetetraactetate) by the process of transmetallation. So far we have successfully used this strategy for obtaining M(II) complexes with both 1,3-pdta (1,3-propanediaminetetraacetate) (Rychlewska et al., 2000; Radanović et al., 2003; Radanović et al., 2004; Rychlewska et al., 2005, 2007) and 1,4-bdta ligands (Radanović et al., 2007). In this procedure, barium(II) cations, forming the homometallic barium 1,3-pdta or 1,4-bdta complex, are being exchanged by much smaller in size metal(II) cations. At the very first step of this reaction we synthesize the ligands by reacting 1,3-propanediamine (or 1,4-butanediamine) with sodium chloracetate. It turned out that, when trying to synthesize 1,4-bdta ligand, we have obtained, in the reaction mixture, besides the expected H₄-1,4-bdta, some amount of α-hydroxycarboxylic acid. Most probably, this α-hydroxycarboxylic acid has originated from the chloracetic acid when heated at pH > 10. Consequent addition of BaCl₂ to the solution resulted in formation of two types of barium(II) salts, one formed by H₄-1,4-bdta and the other by HOCH₂COOH. An attempt to exchange barium(II) by cadmium(II) cations by addition of CdSO₄ resulted in percipitation of two-dimensional homometallic MOF formed by Cd^II cations, hydroxyacetate and sulfate anions, instead of the expected Cd^II 1,4-bdta complex. This has been unequivocally established by the X-ray crystal structure analysis, the results of which are reported in this paper. We next attempted to verify this hypothetical synthetic route by synthesizing the very same Cd^II complex starting from (HOCH₂COO)₂Ba salt. For both samples we have performed elemental microanalyses and NMR measurements which confirmed their identity.

In the crystal the Cd^II nodes bind together by a singly deprotonated hydroxyacetate and doubly deprotonated sulfate linkers. The hydroxyacetate acts as a tetradentate ligand with α-hydroxyacetate group O1–C1–C2–O2 acting as a bidentate chelate to Cd1, and carboxylate group O2–C2–O3 acting as a bidentate chelate to Cd1 at 1/2 - x, 1/2 + y, 1/2 - z. The two Cd^II centers sharing the same (O2) carboxylate oxygen and bridged by the O2–C2–O3 carboxylate group are 4.736 (1) Å apart, and extend in a zigzag manner along the b-direction. Each Cd^II cation is chelated by a hydroxyacetate residue and a carboxylate group, and is coordinated by two water molecules, and one sulfate anion, resulting in a sevenfold coordination mode (Fig. 1). The hydroxyacetate anions and one coordinated water molecule (O1W) lie in the equatorial plane while the other water molecule (O2W) and the sulfate anion take the axial positions. Hence, the coordination polyhedron formed around Cd1 is a distorted pentagonal bipyramid with the in-plane cis bond angles in the range 52.37 (4)–83.68 (5)°, the smallest angle reflecting chelation by the carboxylate ligand, and with the out-of-plane trans angle of 170.76 (6)°. Sulfate anions lie on the twofold axis and connect the neighbouring Cd^II centers, related by this symmetry axis via O4 oxygen atoms. Separation of the two Cd^II metal centers bridged by the sulfate group measures 6.773 (1) Å. The sulfate bridges help to extend the basic structural motif in the a-direction, thus forming a (001) layer (Fig. 2). This polymeric two-dimensional construction is additionally supported by hydrogen bonds (Table 2) that involve crystalline water molecule, which also occupies the twofold axis (O3w). This water molecule acts as a double hydrogen bond donor to two coordinated sulfate O atoms (O4 and its symmetry equivalent) and a double hydrogen bond acceptor from the axially coordinated water molecule (O2W and its twofold equivalent). The equatorially coordinated water molecule (O1W) acts as a hydrogen bond donor to carboxylate O3 and the axially coordinated water O2W. The neighbouring two-dimensional layers are bridged by a hydrogen bond formed between a hydroxyl group (O1) acting as a hydrogen-bond donor and the uncoordinated oxygen atom (O5) from the sulfate anion. The hydrogen bond parameters are provided in Table 2.

The reported X-ray analysis allowed us to identify and structurally characterize the unintentionally synthesized two-dimensional MOF and to demonstrate that care must be taken when preparing the edta-type complexes by transmetallation to avoid precipitation of metal complexes with α-hydroxyacetate bridges. To remove the excess of Ba(II) α-hydroxyacetate, a water washing procedure should be repeated several times.

Experimental

2.56 g (0.003 mol) of CdSO₄.8H₂O were dissolved in 50 cm³ of distilled water at 70°C. To this solution, 6.27 g of solid Ba[Ba(1,4-bdta)].2H₂O containing Ba(HOCH₂COO)₂ in ratio 3:1, respectively, was added and the reaction mixture was heated at 90°C with stirring for 6 h. The precipitated BaSO₄ was removed by filtration and the filtrate was evaporated to ca 10 cm³ and then left in a refrigerator for several days. Colorless crystals of the title compound were collected, washed with ethanol, and air-dried. Yield 0.98 g (59.5%). The complex was recrystallized from hot water while cooling in a refrigerator. Analysis calculated for C₄H₁₄Cd₂O₁₄S.H₂O (FW = 561.03; m. p. 416 K): C 8.84, H 2.87, S 5.90%; found: C 8.93, H 2.83, S 6.28%.