catena-Poly[[[cis-aqua­bis(4-carboxy­cyclo­hexane-1-carboxyl­ato-κ²O,O′)cadmium(II)]-μ-4,4′-bipyridine-κ²N:N] monohydrate]

The title complex, {[Cd(C₈H₁₁O₄)₂(C₁₀H₈N₂)(H₂O)]·H₂O}_n, consists of linear chains formed through 4,4′-bipyridine ligands linking seven-coordinated Cd^II ions. Each Cd^II ion is in a distorted penta­gonal–bipyramidal environment, coordinated by one water ligand, two 4-carboxy­cyclo­hexane-1-carboxyl­ate ligands and one bridging 4,4′-bipyridine ligand to generate linear chains. The water mol­ecules and the Cd atom on one side, and the 4,4′-bipyridine unit on the other, are bisected by two sets of twofold axes. The carboxylate group of the 4-carboxy­cyclo­hexane-1-carboxyl ligand chelates a Cd^II ion, while the (protonated) carboxyl group forms hydrogen bonds with adjacent chains, resulting in a layered structure. This is the first reported occurrence of a dicarboxycyclo­hexane ligand exhibiting a non-bridging coordination mode.

S1. Comment

Considerable progress has recently been achieved on the crystal engineering of supramolecular architectures organized and sustained by means of coordinate covalent, supramolecular contacts (such as hydrogen bonds, π–π interaction), aurophilicity interaction (Colacio et al., 2002; Roesky & Andruh, 2003; Guilera & Steed, 1999), etc. As an excellent building block in the design and construction of supramolecular polymers, 4,4'-bipyridine (4,4'-bipy) has been widely used. On the other hand, 1,4-cyclohexanedicarboxylic acid (H₂chdc) possesses a chair-type structure with cis- and trans-conformations, which can connect metal ions in different directions; it has two carboxylate groups and it has always been reported to link metal centers in a bridging mode (Qi et al., 2003; Thirumurugan et al., 2006). In spite of its being a good candidate for the construction of hydrogen bonding networks, its supramolecular chemistry has rarely been explored and so far mixed metal–organic complexes derived from 4,4'-bipy and chdc ligands have not been reported, even though the combination of 4,4'-bipy and chdc is expected to construct an interesting variety of polymeric compounds. We report here the first occurrence of a one-dimensional Cd complex [Cd(Hchdc)₂(4,4'-bipy)(H₂O)]_n.nH₂O (I), with an unusual binding mode for the Hchdc ligand; it chelates one Cd^II ion, while its remaining (protonated) carboylate group just forms hydrogen-bonding interactions.

Complex (I) consists of linear chains formed through 4,4'-bipy ligands linking seven-coordinated Cd^II ions. As shown in Fig. 1, the Cd^II ion presents a distorted pentagonal–bipyramid geometry. The water molecules and the Cd atom on one side, and the 4,4'-bpy unit on the other, are bisected by two sets of twofold axes. Two trans-related N donors of two 4,4'-bipy ligands stand at the apical positions. Four O atoms of two carboxylate groups of two chdc ligands and one coordinated water molecule form the equatorial plane. The 4,4'-bipy ligand functions as a spacer between two Cd^II ions, the Cd···Cd separation being 11.645 (2) Å. The dihedral angle between two pyridine rings is 43.08 (3)°. As stated, the Hchdc ligand chelates one Cd^II ion through one carboxylate group, while the remaining (protonated) one does not participate in coordination, being only involved in hydrogen-bonding. This is the first reported occurrence of a chdc ligand exhibiting a non-bridging coordination mode.

To our knowledge, this is the first example in the coordination chemistry of the chdc ligand in which it does not act in a bridging mode. As shown in Fig. 2, the Cd^II ions are interlinked by 4,4'-bipy ligands to generate linear chains along the a axis. The crystalline water molecule forms two O—H···O hydrogen bonds with two coordinated carboxylate O atoms.

A noteworthy feature of complex (I) is the two-dimensional hydrogen-bonding network (Fig. 3 and Table 2). Two uncoordinated and two coordinated carboxylate groups, one aqua ligand and one crystalline water molecule are linked through hydrogen-bonding interactions to form a butterfly-like unit. From a topological point of view such six-membered butterfly-like units can be represented as a (3,6) net (Li et al., 2004).

S2. Experimental

A mixture of CdCl₂ (0.184 g, 1 mmol), 1,4-cyclohexanedicarboxylic acid (0.087 g, 0.5 mmol), 4,4'-bipy (0.078 g, 0.5 mmol) and water (18 ml) was sealed in a 25 ml Teflon-lined stainless steel reactor and was heated at 433 K for 3 d. On completion of the reaction, the reactor was cooled slowly to room temperature and the mixture was filtered, giving colorless single crystals suitable for X-ray analysis.#

S3. Refinement

H atoms bonded to C atoms were positioned geometrically [aromatic C—H = 0.93 Å and aliphatic C—H = 0.97–0.98 Å; U_iso(H) = 1.2U_eq(C)]. H atoms bonded to O atoms were located in a difference Fourier map and refined freely; their displacement parameters were set to 1.2U_eq(O).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Bergerhoff et al., 1996); software used to prepare material for publication: SHELXTL (Siemens, 1996).

Figures

	Fig. 1. A view of the title compound, showing 30% probability displacement ellipsoids [symmetry code: (a) −x + 1, y, −z + 1/2; (b) −x, y, 1/2 − z; (c) x − 1, y, z].
	Fig. 2. The chain structure of the title compound. Hydrogen bonds are drawn as dashed lines. H atoms not involved in these interactions have been omitted.
	Fig. 3. The two-dimensional hydrogen-bonding network with (3,6) topology. Hydrogen bonds are drawn as dashed lines. H atoms not involved in these interactions have been omitted.

catena-Poly[[[cis-aquabis(4-carboxycyclohexane-1-carboxylato- κ²O,O')cadmium(II)]-µ-4,4'-bipyridine-κ²N:N] monohydrate]

Crystal data

[Cd(C8H11O4)2(C10H8N2)(H2O)]·H2O	F(000) = 1328
Mr = 646.96	Dx = 1.603 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 7205 reflections
a = 11.6450 (2) Å	θ = 2.2–25.0°
b = 15.1490 (2) Å	µ = 0.88 mm^−1
c = 15.1940 (2) Å	T = 130 K
V = 2680.38 (7) Å^3	Prism, yellow
Z = 4	0.50 × 0.34 × 0.23 mm

Data collection

Siemens SMART 1K CCD area-detector diffractometer	2353 independent reflections
Radiation source: fine-focus sealed tube	2319 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.015
ϕ and ω scans	θmax = 25.0°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −13→13
Tmin = 0.59, Tmax = 0.82	k = −18→18
15765 measured reflections	l = −10→18

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)] = 0.022	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.067	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0389P)^2 + 2.4163P] where P = (Fo^2 + 2Fc^2)/3
2353 reflections	(Δ/σ)max = 0.001
187 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.51 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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
Cd1	0.5000	0.256617 (12)	0.2500	0.01347 (10)
O1	0.45642 (11)	0.21948 (8)	0.39961 (8)	0.0169 (3)
O1W	0.5000	0.10611 (16)	0.2500	0.0410 (7)
H1	0.522 (3)	0.073 (2)	0.207 (2)	0.049*
O2	0.47473 (12)	0.36168 (9)	0.37437 (9)	0.0186 (3)
O3	0.10817 (13)	0.58653 (9)	0.49414 (9)	0.0242 (3)
H3O	0.084 (2)	0.6258 (17)	0.4607 (16)	0.029*
O4	0.09878 (15)	0.50486 (10)	0.37250 (10)	0.0345 (4)
N1	0.30290 (17)	0.26912 (12)	0.23973 (10)	0.0150 (4)
C1	0.24431 (16)	0.34095 (12)	0.21330 (11)	0.0167 (4)
H1A	0.2854	0.3890	0.1919	0.020*
C2	0.12610 (16)	0.34671 (12)	0.21650 (12)	0.0169 (4)
H2A	0.0888	0.3978	0.1981	0.020*
C3	0.06353 (19)	0.27500 (15)	0.24769 (10)	0.0151 (4)
C4	0.12410 (17)	0.19982 (13)	0.27414 (13)	0.0168 (4)
H4A	0.0851	0.1504	0.2947	0.020*
C5	0.24177 (17)	0.19979 (13)	0.26945 (12)	0.0166 (4)
H5A	0.2811	0.1496	0.2876	0.020*
C6	0.38757 (16)	0.31591 (12)	0.51290 (11)	0.0156 (4)
H6A	0.4254	0.2769	0.5554	0.019*
C7	0.39910 (16)	0.41027 (13)	0.54771 (12)	0.0183 (4)
H7A	0.4784	0.4290	0.5415	0.022*
H7B	0.3808	0.4106	0.6100	0.022*
C8	0.32157 (16)	0.47705 (12)	0.50065 (12)	0.0167 (4)
H8A	0.3484	0.4850	0.4407	0.020*
H8B	0.3265	0.5336	0.5304	0.020*
C9	0.19544 (15)	0.44625 (12)	0.49916 (12)	0.0150 (4)
H9A	0.1666	0.4435	0.5597	0.018*
C10	0.18713 (15)	0.35465 (11)	0.45781 (12)	0.0151 (4)
H10A	0.2134	0.3571	0.3973	0.018*
H10B	0.1077	0.3354	0.4577	0.018*
C11	0.26005 (16)	0.28859 (12)	0.50920 (12)	0.0173 (4)
H11A	0.2539	0.2310	0.4817	0.021*
H11B	0.2305	0.2838	0.5687	0.021*
C12	0.44409 (14)	0.29972 (12)	0.42342 (11)	0.0132 (4)
C13	0.12770 (15)	0.51430 (12)	0.44886 (12)	0.0161 (4)
O2W	0.5000	0.50188 (17)	0.2500	0.0411 (7)
H2	0.492 (2)	0.466 (2)	0.296 (2)	0.049*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.01055 (15)	0.01481 (14)	0.01505 (15)	0.000	0.00374 (6)	0.000
O1	0.0181 (7)	0.0146 (6)	0.0180 (7)	0.0013 (5)	0.0005 (5)	−0.0015 (5)
O1W	0.070 (2)	0.0157 (12)	0.0372 (14)	0.000	0.0385 (12)	0.000
O2	0.0212 (6)	0.0162 (7)	0.0183 (7)	−0.0009 (5)	0.0039 (6)	0.0019 (6)
O3	0.0363 (9)	0.0160 (7)	0.0203 (7)	0.0095 (6)	−0.0004 (6)	−0.0006 (6)
O4	0.0568 (10)	0.0233 (7)	0.0233 (8)	0.0146 (7)	−0.0170 (7)	−0.0031 (6)
N1	0.0134 (9)	0.0194 (8)	0.0121 (8)	−0.0010 (7)	0.0005 (6)	−0.0023 (6)
C1	0.0171 (9)	0.0195 (9)	0.0135 (9)	−0.0030 (7)	0.0006 (7)	0.0008 (7)
C2	0.0196 (9)	0.0173 (9)	0.0138 (9)	0.0015 (7)	−0.0026 (7)	0.0002 (7)
C3	0.0144 (11)	0.0192 (10)	0.0116 (9)	−0.0002 (9)	−0.0023 (6)	−0.0026 (7)
C4	0.0156 (9)	0.0161 (9)	0.0187 (9)	−0.0012 (8)	−0.0020 (8)	0.0010 (8)
C5	0.0167 (10)	0.0165 (9)	0.0168 (8)	−0.0010 (8)	−0.0014 (8)	−0.0009 (7)
C6	0.0171 (9)	0.0178 (9)	0.0118 (9)	0.0033 (7)	−0.0008 (7)	0.0021 (7)
C7	0.0171 (9)	0.0226 (10)	0.0152 (9)	0.0015 (7)	−0.0036 (7)	−0.0031 (8)
C8	0.0178 (10)	0.0148 (8)	0.0177 (9)	−0.0005 (8)	−0.0005 (7)	−0.0029 (7)
C9	0.0156 (9)	0.0168 (9)	0.0126 (8)	0.0017 (7)	0.0017 (7)	−0.0005 (7)
C10	0.0135 (9)	0.0158 (9)	0.0161 (9)	−0.0013 (7)	0.0021 (7)	0.0004 (7)
C11	0.0179 (10)	0.0165 (9)	0.0176 (9)	0.0002 (7)	0.0051 (8)	0.0036 (7)
C12	0.0072 (8)	0.0184 (9)	0.0139 (8)	0.0007 (7)	−0.0032 (7)	0.0009 (7)
C13	0.0131 (8)	0.0166 (9)	0.0186 (9)	−0.0012 (7)	0.0021 (7)	0.0007 (7)
O2W	0.083 (2)	0.0154 (11)	0.0249 (13)	0.000	0.0057 (11)	0.000

Geometric parameters (Å, º)

Cd1—O1W	2.280 (2)	C4—C5	1.372 (3)
Cd1—N1	2.3083 (19)	C4—H4A	0.9300
Cd1—N1^i	2.3083 (19)	C5—H5A	0.9300
Cd1—O1^i	2.3961 (13)	C6—C7	1.530 (3)
Cd1—O1	2.3961 (13)	C6—C12	1.530 (2)
Cd1—O2	2.4880 (13)	C6—C11	1.543 (3)
Cd1—O2^i	2.4880 (13)	C6—H6A	0.9800
Cd1—C12	2.7916 (18)	C7—C8	1.533 (3)
Cd1—C12^i	2.7916 (18)	C7—H7A	0.9700
O1—C12	1.276 (2)	C7—H7B	0.9700
O1W—H1	0.87 (3)	C8—C9	1.541 (3)
O2—C12	1.251 (2)	C8—H8A	0.9700
O3—C13	1.312 (2)	C8—H8B	0.9700
O3—H3O	0.83 (3)	C9—C13	1.506 (2)
O4—C13	1.216 (2)	C9—C10	1.526 (2)
N1—C1	1.346 (3)	C9—H9A	0.9800
N1—C5	1.347 (3)	C10—C11	1.527 (2)
C1—C2	1.380 (3)	C10—H10A	0.9700
C1—H1A	0.9300	C10—H10B	0.9700
C2—C3	1.391 (3)	C11—H11A	0.9700
C2—H2A	0.9300	C11—H11B	0.9700
C3—C4	1.399 (3)	O2W—H2	0.89 (3)
C3—C3^ii	1.481 (4)
O1W—Cd1—N1	94.71 (4)	C5—C4—C3	119.27 (19)
O1W—Cd1—N1^i	94.71 (4)	C5—C4—H4A	120.4
N1—Cd1—N1^i	170.59 (9)	C3—C4—H4A	120.4
O1W—Cd1—O1^i	76.42 (3)	N1—C5—C4	123.03 (19)
N1—Cd1—O1^i	99.54 (5)	N1—C5—H5A	118.5
N1^i—Cd1—O1^i	82.69 (5)	C4—C5—H5A	118.5
O1W—Cd1—O1	76.42 (3)	C7—C6—C12	114.78 (15)
N1—Cd1—O1	82.69 (5)	C7—C6—C11	110.34 (15)
N1^i—Cd1—O1	99.54 (5)	C12—C6—C11	109.80 (14)
O1^i—Cd1—O1	152.84 (6)	C7—C6—H6A	107.2
O1W—Cd1—O2	129.77 (3)	C12—C6—H6A	107.2
N1—Cd1—O2	83.18 (5)	C11—C6—H6A	107.2
N1^i—Cd1—O2	90.79 (5)	C6—C7—C8	113.81 (15)
O1^i—Cd1—O2	153.61 (4)	C6—C7—H7A	108.8
O1—Cd1—O2	53.46 (4)	C8—C7—H7A	108.8
O1W—Cd1—O2^i	129.77 (3)	C6—C7—H7B	108.8
N1—Cd1—O2^i	90.79 (5)	C8—C7—H7B	108.8
N1^i—Cd1—O2^i	83.18 (5)	H7A—C7—H7B	107.7
O1^i—Cd1—O2^i	53.46 (4)	C7—C8—C9	111.61 (15)
O1—Cd1—O2^i	153.61 (4)	C7—C8—H8A	109.3
O2—Cd1—O2^i	100.46 (6)	C9—C8—H8A	109.3
O1W—Cd1—C12	103.53 (4)	C7—C8—H8B	109.3
N1—Cd1—C12	79.21 (5)	C9—C8—H8B	109.3
N1^i—Cd1—C12	98.56 (5)	H8A—C8—H8B	108.0
O1^i—Cd1—C12	178.74 (5)	C13—C9—C10	112.34 (15)
O1—Cd1—C12	27.14 (5)	C13—C9—C8	107.42 (14)
O2—Cd1—C12	26.61 (5)	C10—C9—C8	109.98 (15)
O2^i—Cd1—C12	126.50 (5)	C13—C9—H9A	109.0
O1W—Cd1—C12^i	103.53 (4)	C10—C9—H9A	109.0
N1—Cd1—C12^i	98.56 (5)	C8—C9—H9A	109.0
N1^i—Cd1—C12^i	79.21 (5)	C9—C10—C11	110.49 (15)
O1^i—Cd1—C12^i	27.14 (5)	C9—C10—H10A	109.6
O1—Cd1—C12^i	178.74 (5)	C11—C10—H10A	109.6
O2—Cd1—C12^i	126.50 (5)	C9—C10—H10B	109.6
O2^i—Cd1—C12^i	26.61 (5)	C11—C10—H10B	109.6
C12—Cd1—C12^i	152.95 (7)	H10A—C10—H10B	108.1
C12—O1—Cd1	93.96 (11)	C10—C11—C6	112.22 (15)
Cd1—O1W—H1	126 (2)	C10—C11—H11A	109.2
C12—O2—Cd1	90.36 (11)	C6—C11—H11A	109.2
C13—O3—H3O	109.6 (17)	C10—C11—H11B	109.2
C1—N1—C5	117.56 (19)	C6—C11—H11B	109.2
C1—N1—Cd1	126.20 (14)	H11A—C11—H11B	107.9
C5—N1—Cd1	116.04 (14)	O2—C12—O1	120.92 (16)
N1—C1—C2	123.11 (18)	O2—C12—C6	122.13 (16)
N1—C1—H1A	118.4	O1—C12—C6	116.93 (15)
C2—C1—H1A	118.4	O2—C12—Cd1	63.03 (9)
C1—C2—C3	119.02 (18)	O1—C12—Cd1	58.90 (9)
C1—C2—H2A	120.5	C6—C12—Cd1	167.52 (12)
C3—C2—H2A	120.5	O4—C13—O3	123.36 (17)
C2—C3—C4	118.01 (19)	O4—C13—C9	123.27 (17)
C2—C3—C3^ii	122.63 (13)	O3—C13—C9	113.28 (16)
C4—C3—C3^ii	119.35 (14)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1···O4^iii	0.87 (3)	1.82 (3)	2.672 (2)	168 (3)
O3—H3O···O1^iv	0.83 (3)	1.76 (3)	2.5855 (19)	172 (2)
O2W—H2···O2	0.89 (3)	1.99 (3)	2.858 (2)	165 (3)

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