catena-Poly[bis­[1-chloro­methyl-1,4-diazo­nia­bicyclo­[2.2.2]octane] [cadmium(II)-tri-[mu]-chlorido-[chlorido­cadmium(II)]-di-[mu]-chlorido-[chlorido­cadmium(II)]-tri-[mu]-chlorido] tetra­hydrate]

The title compound, {(C₇H₁₅N₂Cl)₂[Cd₃Cl₁₀]·4H₂O}_n, consists of 1-chloro­methyl-1,4-diazo­nia­bicyclo­[2.2.2]octane di­cations, one-dimensional inorganic chains of {[Cd₃Cl₁₀]^4-} anions and uncoordinated water mol­ecules. Each of the two independent Cd^II ions, one with site symmetry 2/m and the other with site symmetry m, is octa­hedrally coordinated by chloride ions (two with site symmetry m and one with site symmetry 2), giving rise to novel polymeric zigzag chains of corner-sharing Cd-centred octa­hedra parallel to the c axis. The organic cations, bisected by mirror planes that contain the two N atoms, three methyl­ene C atoms and the Cl atom, are ordered. Hydrogen bonds (O-H...Cl and O-H...O) between the water mol­ecules (both with O atoms in a mirror plane) and the chloride anions of neighbouring chlorido­cadmate chains form a three-dimensional supra­molecular network.

S1. Comment

As part of the general interest in molecular-based materials with functional properties, attention has been devoted to one-, two- and three-dimensional chlorocadmate(II) compounds. One-dimensional chlorocadmate(II) inorganic chains show a great variety of architectures, such as the linear chains in {[Cd₂Cl₆]^2-}_∞ (Schroder et al., 1983; Corradi et al., 1997; Costin-Hogan et al., 2008), zigzag chains (Charles et al., 1984; Corradi et al., 1997) and ribbon-like chains (Rolies & De Ranter, 1978; Bats et al., 1979; Corradi et al., 1993; Thorn et al., 2006). Against this background, we present here the title compound, (I), with a novel architecture of {[Cd₃Cl₁₀]^4-}_∞ anionic chains. As the basic building unit, the linear [Cd₃Cl₁₀]^4- trimer is interconnected by two bridging (corner-shared) Cl^- ions to form one-dimensional zigzag chains. This unique chain structure is obviously modulated by the shape of the organic cations in (I).

Compound (I) consists of 1-chloromethyl-1,4-diazoniabicyclo[2.2.2]octane cations, one-dimensional inorganic anionic chains of composition {[Cd₃Cl₁₀]^4-}_∞ and uncoordinated water molecules (Fig. 1). Two nonequivalent Cd^II ions are present in the chains with moderately distorted octahedral arrangements (Table 1). The Cd1 ion (Wyckoff site 2d, site symmetry 2/m) is coordinated by six bridging Cl^- anions [Cl2, Cl2A, Cl3, Cl3A, Cl3B and Cl3C; symmetry codes: (A) -x + 1, y, -z + 3; (B) -x + 1, -y, -z + 3; (C) x, -y, z], while the Cd2 ion (Wyckoff site 4i, site symmetry m) is surrounded by one terminal (Cl4) and five bridging (Cl2A, Cl3, Cl3C, Cl5 and Cl5C) Cl^- anions. The Cd1 and Cd2 ions are linked together by three Cl^- anions (Cl2A, Cl3 and Cl3C). The Cd2—Cd1—Cd2A and Cd1—Cd2—Cd1C angles within the chains are 180 and 135.92 (1)°, respectively, giving rise to zigzag chains of edge-sharing Cd-centred octahedra (Fig. 2).

The zigzag anionic chain in (I) is a new coordination architecture when compared with a similar compound, (C₆H₅NH₃)₄[Cd₃Cl₁₀], which contains the same trimeric [Cd₃Cl₁₀]^4- unit (Costin-Hogan et al., 2008). In that compound, the linear trimers are assembled differently from those in (I), i.e. interconnected by bridging (corner-shared) Cl^- ions, with each trimer linking four other trimers to form a two-dimensional network. Other trimeric chlorocadmate anions have been described, such as [Cd₃Cl₉]^3- in (C₆H₅NH)₃[Cd₃Cl₉], in which the trimers are interconnected by three bridging (corner-shared) Cl^- ions to give rise to one-dimensional linear chains (Jian et al., 2006).

The presence of organic cations (generally protonated amines) and solvent molecules, as spacers between the inorganic anions, can modulate the distances between chains or layers and give rise to distinctive hydrogen-bonding features and structural packings. In (I), the chains run along the c axis and are well separated by 1-chloromethyl-1,4-diazoniabicyclo[2.2.2]octane cations and water molecules, and there are rich intermolecular hydrogen-bonding interactions. The O1—H1C···Cl3ⁱ [symmetry code: (i) -x + 3/2, -y + 1/2, -z + 2] hydrogen bonds between the uncoordinated water molecules and the bridging Cl^- anions of the inorganic chains contribute to the formation of two-dimensional supramolecular anionic layers in the bc plane (Fig. 3). Between adjacent anionic layers, the organic cations and water molecules pack with an ABA' sequence as a multilayer structure along the b axis. The A and A' layers are composed of organic cations, while the B layer is composed of water molecules. The N2—H2B···O1 hydrogen bonds between 1-chloromethyl-1,4-diazoniabicyclo[2.2.2]octane cations and water molecules make the chloromethyl tails of the organic cations between the A and A' layers orient face-to-face, contributing to the stability of the crystal packing. The O2—H2C···Cl4 and O2—H1D···O1 hydrogen bonds with the terminal Cl^- anions from adjacent anionic layers and water molecules generate a three-dimensional network.

In (I), the 1-(chloromethyl)-1,4-diazoniabicyclo[2.2.2]octane cation is ordered due to the confinement of the C—H···Cl interactions. By contrast, the 1,4-diazoniabicyclo[2.2.2]octane cation is found to be disordered in several cases, including the 1:1 salts with perchloric acid (Katrusiak, 2000), trichromate (Ding et al., 2004), biphenol (Ferguson et al., 1998) and fluoroborate (Budzianowski et al., 2008).

Our interest in chlorocadmate complexes rests on their potential as molecule-based ferroelectrics. Temperature-dependent dielectric constant measurements were performed on a powder sample in order to see whether (I) is a ferroelectric (Ye et al., 2006; Fu et al., 2007; Zhao et al. 2008; Zhang et al., 2008; Ye et al. 2009). Unfortunately, the compound has no dielectric anomalies in the temperature range 93–353 K, suggesting that it might be only a paraelectric.

S2. Experimental

1, 4-Diazabicyclo[2.2.2]octane (5.6 g, 0.05 mol) was added to dichloromethane (20 ml) and the mixture was refluxed for 8 h. On standing for about 16 h at room temperature, a white precipitate of 1-(chloromethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium chloride was obtained. The title compound was synthesized by adding a solution of 1-(chloromethyl)-1,4-diazabicyclo[2.2.2]octan-1-ium chloride (1.97 g, 10 mmol) in HCl (37%, 20 ml) to a solution of cadmium chloride (8 mmol) in H₂O (20 ml). After a few weeks, colourless hygroscopic block crystals of (I) were obtained on slow evaporation of the solvent.

S3. Refinement

Considering it is meaningless to find H atoms from a difference Fourier map in a crystal containing such heavy atoms as Cd, all H atoms were generated geometrically and refined using a riding model, with N—H = 0.90, C—H = 0.96 or O—H = 0.85 Å, and with U_iso(H) = 1.2U_eq(C,N) or 1.5U_eq(O).

H atoms bonded to O atoms were generated according to the possible directions of the hydrogen bonds, as well as the supposition of sp³ hybridization of the O atoms. First of all, atom O1 is the acceptor in an N—H···O hydrogen bond. Geometric analysis shows that hydrogen bonds may also form between O atoms, and between O and Cl atoms. For the hydrogen bond between atoms O1 and O2, not enough structural information can be obtained to determine which one is the donor and which the acceptor, and therefore one possibility was chosen. Three H atoms were generated on O1 by linking atoms N2 and O1, and then the command Hadd 3 in the XP program (Reference?) was used so that atom O1 has a tetrahedral geometry. One of the three H atoms is located on a special position (mirror) and this O—H bond points to atom O2, while the other two are mirror symmetry-related and may be involved in the O—H···Cl hydrogen bond. Similarly, four H atoms bonded to atom O2 can be generated. One is located on the mirror and the O—H bond points to atom O1, two are mirror related and may be involved in O—H···Cl hydrogen bonds, and the last one cannot be involved in any hydrogen bond so it is omitted. To maintain a sensible geometry, one of the two neighbouring H atoms in the mirror has to be omitted. We omitted the one bonded to atom O1 as one possibility.

Computing details

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of (I), showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Dashed lines indicate the intramolecular hydrogen bonds. [Symmetry codes: (A) -x + 1, y, -z + 3; (B) -x + 1, -y, -z + 3; (C) x, -y, z.]
	Fig. 2. The chlorocadmate chains in (I), formed by corner-shared linear {[Cd3Cl10]^4-}∞ trimers running along the c axis separated by 1-chloromethyl-1,4-diazoniabicyclo[2.2.2]octane cations and water molecules. Dashed lines indicate hydrogen bonds. H atoms bonded to C atoms have been omitted for clarity.
	Fig. 3. A view of the packing of (I), along the a axis. Dashed lines indicate hydrogen bonds. The organic dications and the O2 water molecules have been omitted for clarity.

catena-Poly[bis[1-chloromethyl-1,4-diazoniabicyclo[2.2.2]octane] [cadmium(II)-tri-µ-chlorido-[chloridocadmium(II)]-di-µ-chlorido- [chloridocadmium(II)]-tri-µ-chlorido] tetrahydrate]

Crystal data

(C7H15ClN2)2[Cd3Cl10]·4H2O	F(000) = 1060
Mr = 1089.08	Dx = 2.200 Mg m^−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2y	Cell parameters from 2488 reflections
a = 20.218 (14) Å	θ = 2.8–27.5°
b = 7.968 (4) Å	µ = 2.93 mm^−1
c = 10.208 (5) Å	T = 293 K
β = 91.288 (13)°	Prism, colourless
V = 1644.1 (16) Å^3	0.30 × 0.25 × 0.20 mm
Z = 2

Data collection

Rigaku Mercury2 diffractometer	1975 independent reflections
Radiation source: fine-focus sealed tube	1830 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 28.5714 pixels mm^-1	θmax = 27.5°, θmin = 2.0°
CCD profile fitting scans	h = −26→26
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −10→10
Tmin = 0.420, Tmax = 0.560	l = −13→13
8541 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.023	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.085	H-atom parameters constrained
S = 1.30	w = 1/[σ^2(Fo^2) + (0.0456P)^2 + 1.3462P] where P = (Fo^2 + 2Fc^2)/3
1975 reflections	(Δ/σ)max = 0.001
103 parameters	Δρmax = 0.80 e Å^−3
0 restraints	Δρmin = −0.99 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.87905 (19)	0.0000	0.8529 (3)	0.0407 (9)
H1C	0.8985	0.0871	0.8251	0.061*
O2	0.7385 (3)	0.0000	0.8222 (6)	0.0763 (15)
H2D	0.7800	0.0000	0.8380	0.114*
H2C	0.7228	−0.0871	0.8581	0.114*	0.50
Cl1	0.71971 (6)	0.0000	1.48396 (13)	0.0398 (3)
C1	0.8067 (2)	0.0000	1.4854 (4)	0.0298 (10)
H1A	0.8228	−0.0975	1.5313	0.036*
C2	0.9073 (2)	0.0000	1.3591 (5)	0.0358 (12)
H2A	0.9219	−0.0976	1.4068	0.043*
C3	0.9370 (2)	0.0000	1.2253 (4)	0.0316 (10)
H3A	0.9642	0.0976	1.2152	0.038*
C4	0.81064 (16)	−0.1540 (4)	1.2728 (3)	0.0288 (7)
H4A	0.7632	−0.1564	1.2647	0.035*
H4B	0.8248	−0.2524	1.3198	0.035*
C5	0.84045 (17)	−0.1529 (4)	1.1382 (3)	0.0282 (7)
H5A	0.8670	−0.2515	1.1270	0.034*
H5B	0.8058	−0.1536	1.0723	0.034*
N1	0.83266 (16)	0.0000	1.3481 (3)	0.0184 (7)
N2	0.88228 (18)	0.0000	1.1242 (3)	0.0233 (7)
H2B	0.9002	0.0000	1.0432	0.028*
Cd1	0.5000	0.0000	1.5000	0.02361 (14)
Cd2	0.546334 (14)	0.0000	1.16976 (3)	0.02254 (12)
Cl2	0.57419 (5)	0.0000	1.70499 (10)	0.0264 (2)
Cl3	0.56864 (4)	0.22614 (10)	1.36156 (7)	0.02908 (19)
Cl4	0.66354 (6)	0.0000	1.09508 (13)	0.0430 (3)
Cl5	0.5000	0.22249 (13)	1.0000	0.0232 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.053 (2)	0.040 (2)	0.0291 (18)	0.000	0.0073 (16)	0.000
O2	0.063 (3)	0.085 (4)	0.080 (4)	0.000	−0.014 (3)	0.000
Cl1	0.0289 (6)	0.0524 (8)	0.0387 (6)	0.000	0.0141 (5)	0.000
C1	0.029 (2)	0.039 (3)	0.021 (2)	0.000	0.0031 (17)	0.000
C2	0.0178 (19)	0.066 (4)	0.023 (2)	0.000	−0.0027 (17)	0.000
C3	0.0206 (19)	0.049 (3)	0.026 (2)	0.000	0.0012 (17)	0.000
C4	0.0349 (16)	0.0182 (14)	0.0336 (17)	−0.0065 (12)	0.0077 (13)	−0.0049 (13)
C5	0.0396 (17)	0.0218 (15)	0.0229 (14)	−0.0036 (13)	−0.0012 (13)	−0.0039 (12)
N1	0.0177 (15)	0.0201 (16)	0.0174 (15)	0.000	0.0003 (12)	0.000
N2	0.0274 (18)	0.0274 (18)	0.0152 (16)	0.000	0.0016 (13)	0.000
Cd1	0.0296 (2)	0.0264 (2)	0.0148 (2)	0.000	−0.00042 (16)	0.000
Cd2	0.02610 (18)	0.02544 (19)	0.01597 (17)	0.000	−0.00222 (12)	0.000
Cl2	0.0262 (5)	0.0291 (5)	0.0238 (5)	0.000	−0.0049 (4)	0.000
Cl3	0.0377 (4)	0.0261 (4)	0.0233 (4)	−0.0085 (3)	−0.0016 (3)	−0.0015 (3)
Cl4	0.0242 (5)	0.0694 (9)	0.0354 (6)	0.000	−0.0010 (5)	0.000
Cl5	0.0286 (5)	0.0231 (5)	0.0180 (4)	0.000	0.0000 (4)	0.000

Geometric parameters (Å, º)

O1—H1C	0.8500	N1—C4^i	1.510 (4)
O2—H2D	0.8500	N2—C5^i	1.492 (4)
O2—H2C	0.8500	N2—H2B	0.9100
Cl1—C1	1.759 (5)	Cd1—Cl2^ii	2.5471 (15)
C1—N1	1.508 (5)	Cd1—Cl2	2.5471 (15)
C1—H1A	0.9601	Cd1—Cl3^ii	2.6940 (12)
C2—C3	1.504 (6)	Cd1—Cl3^iii	2.6940 (12)
C2—N1	1.510 (5)	Cd1—Cl3^i	2.6940 (12)
C2—H2A	0.9602	Cd1—Cl3	2.6940 (12)
C3—N2	1.495 (6)	Cd2—Cl4	2.506 (2)
C3—H3A	0.9600	Cd2—Cl5^iv	2.6364 (11)
C4—N1	1.510 (4)	Cd2—Cl5	2.6364 (11)
C4—C5	1.513 (4)	Cd2—Cl3	2.6914 (12)
C4—H4A	0.9600	Cd2—Cl3^i	2.6914 (12)
C4—H4B	0.9597	Cd2—Cl2^ii	2.7771 (19)
C5—N2	1.492 (4)	Cl2—Cd2^ii	2.7771 (19)
C5—H5A	0.9601	Cl5—Cd2^iv	2.6364 (11)
C5—H5B	0.9601
H2D—O2—H2C	107.2	Cl2^ii—Cd1—Cl2	180.0
N1—C1—Cl1	111.2 (3)	Cl2^ii—Cd1—Cl3^ii	97.48 (4)
N1—C1—H1A	109.4	Cl2—Cd1—Cl3^ii	82.52 (4)
Cl1—C1—H1A	109.4	Cl2^ii—Cd1—Cl3^iii	97.48 (4)
C3—C2—N1	110.5 (4)	Cl2—Cd1—Cl3^iii	82.52 (4)
C3—C2—H2A	109.6	Cl3^ii—Cd1—Cl3^iii	83.96 (5)
N1—C2—H2A	109.5	Cl2^ii—Cd1—Cl3^i	82.52 (4)
N2—C3—C2	108.8 (4)	Cl2—Cd1—Cl3^i	97.48 (4)
N2—C3—H3A	110.0	Cl3^ii—Cd1—Cl3^i	96.04 (5)
C2—C3—H3A	109.8	Cl3^iii—Cd1—Cl3^i	180.000 (1)
N1—C4—C5	109.8 (2)	Cl2^ii—Cd1—Cl3	82.52 (4)
N1—C4—H4A	110.0	Cl2—Cd1—Cl3	97.48 (4)
C5—C4—H4A	109.8	Cl3^ii—Cd1—Cl3	180.0
N1—C4—H4B	109.2	Cl3^iii—Cd1—Cl3	96.04 (5)
C5—C4—H4B	109.8	Cl3^i—Cd1—Cl3	83.96 (5)
H4A—C4—H4B	108.2	Cl4—Cd2—Cl5^iv	97.15 (4)
N2—C5—C4	109.3 (3)	Cl4—Cd2—Cl5	97.15 (4)
N2—C5—H5A	109.7	Cl5^iv—Cd2—Cl5	84.51 (5)
C4—C5—H5A	109.8	Cl4—Cd2—Cl3	94.43 (4)
N2—C5—H5B	110.1	Cl5^iv—Cd2—Cl3	168.41 (2)
C4—C5—H5B	109.7	Cl5—Cd2—Cl3	94.54 (4)
H5A—C5—H5B	108.2	Cl4—Cd2—Cl3^i	94.43 (4)
C1—N1—C4	111.6 (2)	Cl5^iv—Cd2—Cl3^i	94.54 (4)
C1—N1—C4^i	111.6 (2)	Cl5—Cd2—Cl3^i	168.41 (2)
C4—N1—C4^i	108.7 (3)	Cl3—Cd2—Cl3^i	84.06 (5)
C1—N1—C2	107.4 (3)	Cl4—Cd2—Cl2^ii	170.31 (4)
C4—N1—C2	108.7 (2)	Cl5^iv—Cd2—Cl2^ii	90.01 (4)
C4^i—N1—C2	108.7 (2)	Cl5—Cd2—Cl2^ii	90.01 (4)
C5—N2—C5^i	109.5 (4)	Cl3—Cd2—Cl2^ii	78.43 (3)
C5—N2—C3	110.3 (2)	Cl3^i—Cd2—Cl2^ii	78.43 (3)
C5^i—N2—C3	110.3 (2)	Cd1—Cl2—Cd2^ii	82.62 (5)
C5—N2—H2B	108.9	Cd2—Cl3—Cd1	81.60 (4)
C5^i—N2—H2B	108.9	Cd2^iv—Cl5—Cd2	95.49 (5)
C3—N2—H2B	108.9

Symmetry codes: (i) x, −y, z; (ii) −x+1, −y, −z+3; (iii) −x+1, y, −z+3; (iv) −x+1, −y, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1C···Cl3^v	0.85	2.52	3.283 (3)	150
O2—H2D···O1	0.85	2.00	2.851 (7)	173
O2—H2C···Cl4	0.85	2.81	3.201 (6)	110
N2—H2B···O1	0.91	1.98	2.769 (5)	144

Symmetry code: (v) −x+3/2, −y+1/2, −z+2.