Diammonium tricadmium tris­(sulfate) dihydroxide dihydrate

Xin Yin

doi:10.1107/S1600536811012979

. 2011 Apr 13;67(Pt 5):i31. doi: 10.1107/S1600536811012979

Diammonium tricadmium tris(sulfate) dihydroxide dihydrate

Xin Yin ^a,^*

PMCID: PMC3089235 PMID: 21754257

Abstract

The title compound, (NH₄)₂Cd₃(SO₄)₃(OH)₂(H₂O)₂, has been obtained serendipitously. It is isotypic with the heavier alkali analogues M ₂Cd₃(SO₄)₃(OH)₂(H₂O)₂ (M = K, Rb, Cs). The structure contains two Cd²⁺ ions, one in a general position and one with site symmetry m. The former Cd²⁺ ion is coordinated by three O atoms of three SO₄ groups, two hydroxide O atoms and one water O atom, the latter Cd²⁺ ion by four O atoms of four SO₄ groups and two hydroxide O atoms, both in a distorted octahedral coordination geometry. This arrangement leads to the formation of a layered framework extending parallel to (100), with the ammonium cations situated in the voids. O—H⋯O hydrogen bonds involving the water molecules, hydroxide groups and sulfate O atoms, as well as N—H⋯O hydrogen bonds between ammonium cations and sulfate O atoms consolidate the crystal packing.

Related literature

For the isotypic K and Cs analogues, see: Louer & Louer (1982 ▶), and for the Rb analogue, see: Swain & Guru Row (2006 ▶).

Experimental

Crystal data

(NH₄)₂Cd₃(SO₄)₃(OH)₂(H₂O)₂
M _r = 731.51
Orthorhombic,
a = 18.906 (3) Å
b = 7.9483 (11) Å
c = 9.9809 (13) Å
V = 1499.8 (4) Å³
Z = 4
Mo Kα radiation
μ = 4.72 mm⁻¹
T = 296 K
0.12 × 0.10 × 0.08 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.601, T _max = 0.704
7060 measured reflections
1770 independent reflections
1739 reflections with I > 2σ(I)
R _int = 0.051

Refinement

R[F ² > 2σ(F ²)] = 0.027
wR(F ²) = 0.066
S = 1.08
1770 reflections
118 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.68 e Å⁻³
Δρ_min = −1.31 e Å⁻³
Absolute structure: Flack (1983 ▶), 825 Friedel pairs
Flack parameter: −0.07 (4)

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT-Plus (Bruker, 2003 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: Mercury (Macrae et al., 2006 ▶) and DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811012979/wm2470sup1.cif

e-67-00i31-sup1.cif^{(20.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811012979/wm2470Isup2.hkl

e-67-00i31-Isup2.hkl^{(87.3KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O10—H10B⋯O7ⁱ	0.85	2.25	3.087 (5)	167
O10—H10B⋯O5ⁱⁱ	0.85	2.36	2.985 (6)	131
O9—H9A⋯O6ⁱⁱⁱ	0.85	2.18	3.029 (7)	173
O8—H8A⋯O5ⁱⁱ	0.85	2.56	3.322 (9)	150
O8—H8A⋯O5ⁱ	0.85	2.56	3.322 (9)	150
N1—H1B⋯O10^iv	0.90	2.26	2.948 (6)	133
N1—H1D⋯O4ⁱⁱ	0.90	2.18	3.077 (5)	180
N1—H1C⋯O4^v	0.90	2.19	3.074 (7)	168
N1—H1A⋯O3^vi	0.90	2.38	2.995 (6)	126
N1—H1D⋯O2ⁱⁱ	0.90	2.64	3.196 (7)	121

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

supplementary crystallographic information

Comment

The title compound, (NH₄)₂Cd₃(SO₄)₃(OH)₂(H₂O)₂, (I), formed accidentally under hydrothermal reaction conditions. Our intended target product was to synthesis a coordination compound from 1H-benzimidazole-5,6-dicarboxylate and CdSO₄^.8/3H₂O. The presence of ammonium ions in the finally obtained compound points to an internal redox process that presumably has caused a (partly) reduction of the nitrogen atoms of 1H-benzimidazole-5,6-dicarboxylate or the nitrate anions. (NH₄)₂Cd₃(SO₄)₃(OH)₂(H₂O)₂ is isotypic with other M₂Cd₃(SO₄)₃(OH)₂(H₂O)₂ members (M = K, Cs (Louer & Louer, 1982); M = Rb (Swain & Guru Row, 2006)).

The asymmetric unit of (I) is illustrated in Fig. 1. The crystal structure of (NH₄)₂Cd₃(SO₄)₃(OH)₂(H₂O)₂ is made up from two different Cd²⁺ ions (one on a general position (Cd1), one with site symmetry m (Cd2)), two sulfate ions (likewise one on a general position and the other with site symmetry m), two hydroxide groups, one water molecule and one NH₄⁺ cation. Both Cd²⁺ cations are six-coordinated in an octahedral coordination geometry. Cd2 is coordinated by four sulfate ions and two hydroxide ions, while Cd1 is coordinated by three sulfate ons, two hydroxide anions and one water molecule. There are four types of oxygen atoms in the crystal structure of the title compound. The O3 atom of one SO₄^2- anion is solely bound to the S atom, O8 and O9 represent the oxygen atoms of hydroxide groups shared by three Cd atoms, O10 is the water O atom bound to one Cd atom and all other O atoms represent sulfate O atoms coordinated to only one Cd atom.

As can be seen in Fig. 2, the Cd(1)O₆ polyhedra are connected by sharing edges of OH groups. Cd(2)O₆ octahedra and SO₄ tetrahedra are linked to these dimers via common corners, thus forming a two-dimensional network extending parallel to the bc plane. The NH₄⁺ cations are situated in the voids of the layers. Through formation of N—H···O and O—H···O hydrogen bonds a three-dimensional structure is formed. Since all water and hydroxide groups and most of the sulfate O atoms are involved in hydrogen bonding, the resulting network can be considered as relatively stable (Table 2, Fig. 3).

Experimental

All reagents were obtained from commercial sources and used without further purification. A mixture of CdSO₄^.8/3H₂O (0.2565 g, 1.0 mmol), 1H-benzimidazole-5,6-dicarboxylate (0.1236 g,0.6 mmol), CH₃CN (6 ml) and 4 ml water were added to a 23 ml Teflon-lined stainless container, which was heated to 423 K and held at that temperature for 5 days. After cooling to room temperature in 24 h, colourless crystals were recovered by filtration (yield 49% based on CdSO₄^.8/3H₂O).