Polymeric aqua­(benz­imidazole-κN)(μ-malonato)­cobalt(II)

The crystal structure of the title compound, [Co(C₃H₂O₄)(C₇H₆N₂)(H₂O)]_n, consists of two-dimensional polymeric Co^II complex layers. The octahedral coordination around a Co^II atom is composed of a chelate malonate, two monodentate malonate anions from the adjacent asymmetric unit, a bez­imidazole ligand and a coordinated water molecule. Each malonate dianion links three Co^II atoms related by an n-glide plane to form polymeric layers in the (010) plane. π–π stacking of the benz­imidazole ligands occurs between adjacent polymeric layers, the separation between parallel benz­imidazole rings being 3.42 (2) Å.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.039
• wR factor = 0.101
• Data-to-parameter ratio = 12.2

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S1. Comment

The aromatic π–π-stacking interaction has been observed in some metal complexes with aromatic heteropolycyclic ligands, such as phenathroline, bithiazole and benzimidazole (Chen et al., 2003). A new polymeric complex, (I), with benzimidazole ligand has recently been prepared in the laboratory and its X-ray structure is presented here to show the π–π stacking occurring between the polymeric complex layers.

The crystal of (I) consists of polymeric sheets of (I). The coordination geometry around a Co^II atom is illustrated in Fig. 1. The octahedral coordination geometry is formed by a chelate malonate, two monodentate malonates from adjacent asymmetric units, a benzimidazole and a coordinated water. The malonate chelates to the Co^II atom with the terminal carboxyl groups in a boat coordination configuration. The Co—O(water) distance of 2.169 (2) Å is significantly longer than the average Co—O(carboxyl) distance of 2.092 (2) Å, ranging from 2.074 (2) to 2.121 (2) Å. The coordinated water molecule forms hydrogen bonds to the neighboring carboxyl groups, as shown in Fig. 1 and Table 2.

The malonate dianion plays as a bridging role in the structure. Each malonate dianion links three Co^II atoms, related by an n-glide plane, to form the infinite two-dimensional polymer layers along the (010) plane (Fig. 2). The molecular packing is illustrated in Fig. 3. The parallel disposition of benzimidazole rings from the neighboring polymer layers is shown in Fig. 3. The shorter separation of 3.42 (2) Å between the neighboring benzimidazole rings suggests the existence of a π–π stacking between the adjacent polymer layers.

S2. Experimental

An ethanol solution (5 ml) of benzimidazole (0.236 g, 2 mmol) was mixed with an aqueous solution (10 ml) of CoCl₂·6H₂O (0.237 g, 1 mmol) at room temperature. An aqueous solution (8 ml) containing malonic acid (0.104 g, 1 mmol) and Na₂CO₃ (0.106 g, 1 mmol) was added to the above solution with stirring at room temperature. Then the mixture was refluxed for 2 h and filtered. The pink single crystals were obtained after 5 d.

S3. Refinement

The H atoms of water were located in a difference Fourier map and were included in structure-factor calculations with fixed positional and displacement parameters of 0.05 Ų. Other H atoms were placed in calculated positions with C—H = 0.93 Å (benzimidazole) or 0.97 Å (malonate) and N—H = 0.86 Å, and included in the final cycles of refinement in riding model, with U_iso(H) = 1.2U_eq of the carrier atom.

Computing details

Data collection: PROCESS-AUTO (Rigaku Corporation, 1998); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC and Rigaku, 2002); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The coordination environment around the Co^II atom in (I) with 30% probability displacement ellipsoids. Dashed lines indicate the hydrogen bonding [symmetry codes: (i) x − 1/2, 1/2 − y, 1/2 + z; (ii) x − 1/2, 1/2 − y, z − 1/2].
	Fig. 2. The polymeric layer structure formed by malonate linkage.
	Fig. 3. The molecular packing showing the π-π stacking between benzimidazole rings.

(I)

Crystal data

[Co(C3H2O4)(C7H6N2)(H2O)]	F(000) = 604
Mr = 297.13	Dx = 1.772 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 6128 reflections
a = 6.7654 (10) Å	θ = 2.9–25.0°
b = 21.9841 (18) Å	µ = 1.56 mm^−1
c = 7.4945 (14) Å	T = 295 K
β = 91.944 (2)°	Plate, pink
V = 1114.0 (3) Å^3	0.25 × 0.18 × 0.10 mm
Z = 4

Data collection

Rigaku R-AXIS RAPID diffractometer	1995 independent reflections
Radiation source: fine-focus sealed tube	1828 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
Detector resolution: 10.00 pixels mm^-1	θmax = 25.3°, θmin = 1.9°
ω scans	h = −7→8
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −26→26
Tmin = 0.672, Tmax = 0.851	l = −9→8
7470 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)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.101	H-atom parameters constrained
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0401P)^2 + 2.9317P] where P = (Fo^2 + 2Fc^2)/3
1995 reflections	(Δ/σ)max < 0.001
163 parameters	Δρmax = 0.44 e Å^−3
0 restraints	Δρmin = −0.79 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
Co	0.26052 (7)	0.289972 (19)	0.63585 (6)	0.02086 (16)
O1	0.4298 (4)	0.24088 (11)	0.8214 (3)	0.0300 (6)
O2	0.6051 (4)	0.16303 (11)	0.9275 (3)	0.0269 (5)
O3	0.4191 (4)	0.24378 (11)	0.4439 (3)	0.0275 (5)
O4	0.6116 (4)	0.17026 (11)	0.3451 (3)	0.0311 (6)
O5	0.0569 (4)	0.21376 (11)	0.6355 (3)	0.0298 (6)
N1	0.4732 (4)	0.36040 (13)	0.6495 (4)	0.0274 (6)
N2	0.7638 (5)	0.40225 (16)	0.6099 (5)	0.0404 (8)
H2	0.8860	0.4051	0.5829	0.048*
C1	0.6553 (6)	0.35196 (18)	0.5971 (5)	0.0343 (9)
H1	0.7025	0.3150	0.5560	0.041*
C2	0.6855 (7)	0.5098 (2)	0.7054 (6)	0.0484 (11)
H2A	0.8075	0.5276	0.6857	0.058*
C3	0.5322 (8)	0.5430 (2)	0.7686 (7)	0.0539 (12)
H3	0.5500	0.5843	0.7914	0.065*
C4	0.3503 (8)	0.5164 (2)	0.7995 (7)	0.0534 (12)
H4	0.2501	0.5403	0.8445	0.064*
C5	0.3136 (6)	0.45587 (18)	0.7655 (6)	0.0387 (9)
H5	0.1909	0.4386	0.7861	0.046*
C6	0.4671 (6)	0.42154 (16)	0.6991 (5)	0.0296 (8)
C7	0.6530 (6)	0.44825 (18)	0.6716 (5)	0.0363 (9)
C8	0.5074 (5)	0.18934 (15)	0.8041 (4)	0.0221 (7)
C9	0.4775 (6)	0.15551 (15)	0.6285 (4)	0.0266 (7)
H9A	0.3448	0.1387	0.6235	0.032*
H9B	0.5693	0.1216	0.6276	0.032*
C10	0.5052 (5)	0.19316 (15)	0.4609 (4)	0.0223 (7)
H51	−0.0311	0.2197	0.5455	0.050*
H52	−0.0252	0.2131	0.7403	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co	0.0245 (3)	0.0208 (3)	0.0173 (2)	0.00066 (18)	0.00094 (17)	−0.00023 (17)
O1	0.0428 (15)	0.0258 (13)	0.0209 (12)	0.0077 (11)	−0.0051 (11)	−0.0029 (10)
O2	0.0310 (13)	0.0251 (12)	0.0241 (12)	0.0036 (10)	−0.0059 (10)	0.0018 (10)
O3	0.0373 (14)	0.0247 (12)	0.0210 (12)	0.0079 (11)	0.0076 (10)	0.0022 (10)
O4	0.0449 (16)	0.0232 (12)	0.0258 (13)	0.0024 (11)	0.0101 (11)	0.0004 (10)
O5	0.0313 (14)	0.0334 (14)	0.0245 (13)	−0.0037 (11)	−0.0014 (10)	0.0008 (10)
N1	0.0289 (16)	0.0228 (14)	0.0304 (16)	−0.0013 (12)	−0.0006 (12)	−0.0008 (12)
N2	0.0273 (17)	0.0406 (19)	0.053 (2)	−0.0059 (15)	0.0007 (15)	−0.0050 (16)
C1	0.033 (2)	0.0293 (19)	0.041 (2)	0.0011 (16)	0.0017 (17)	−0.0050 (16)
C2	0.057 (3)	0.038 (2)	0.050 (3)	−0.020 (2)	−0.002 (2)	0.000 (2)
C3	0.078 (4)	0.025 (2)	0.059 (3)	−0.007 (2)	0.000 (3)	−0.005 (2)
C4	0.076 (4)	0.031 (2)	0.054 (3)	0.014 (2)	0.007 (2)	−0.004 (2)
C5	0.040 (2)	0.032 (2)	0.045 (2)	0.0041 (17)	0.0088 (18)	0.0009 (17)
C6	0.039 (2)	0.0232 (17)	0.0261 (18)	0.0006 (15)	−0.0015 (15)	−0.0001 (14)
C7	0.044 (2)	0.030 (2)	0.034 (2)	−0.0092 (17)	−0.0057 (17)	−0.0001 (16)
C8	0.0202 (16)	0.0250 (17)	0.0212 (16)	−0.0025 (13)	0.0030 (13)	0.0019 (13)
C9	0.037 (2)	0.0208 (16)	0.0225 (17)	0.0005 (14)	0.0016 (14)	0.0009 (13)
C10	0.0250 (17)	0.0217 (16)	0.0199 (16)	−0.0037 (13)	−0.0008 (13)	−0.0025 (13)

Geometric parameters (Å, º)

Co—O1	2.074 (2)	N2—H2	0.86
Co—O4^i	2.085 (2)	C1—H1	0.93
Co—O3	2.087 (2)	C2—C3	1.366 (7)
Co—N1	2.114 (3)	C2—C7	1.392 (6)
Co—O2^ii	2.121 (2)	C2—H2A	0.93
Co—O5	2.169 (2)	C3—C4	1.389 (7)
O1—C8	1.257 (4)	C3—H3	0.93
O2—C8	1.259 (4)	C4—C5	1.375 (6)
O3—C10	1.260 (4)	C4—H4	0.93
O4—C10	1.252 (4)	C5—C6	1.390 (6)
O5—H51	0.894	C5—H5	0.93
O5—H52	0.977	C6—C7	1.409 (6)
N1—C1	1.319 (5)	C8—C9	1.520 (5)
N1—C6	1.396 (5)	C9—C10	1.521 (5)
N2—C1	1.329 (5)	C9—H9A	0.97
N2—C7	1.350 (5)	C9—H9B	0.97
O1—Co—O4^i	89.07 (10)	C3—C2—C7	117.7 (4)
O1—Co—O3	85.63 (10)	C3—C2—H2A	121.1
O4^i—Co—O3	174.47 (10)	C7—C2—H2A	121.1
O1—Co—N1	89.38 (11)	C2—C3—C4	121.3 (4)
O4^i—Co—N1	90.12 (11)	C2—C3—H3	119.3
O3—Co—N1	91.41 (11)	C4—C3—H3	119.3
O1—Co—O2^ii	174.61 (10)	C5—C4—C3	122.1 (4)
O4^i—Co—O2^ii	96.27 (10)	C5—C4—H4	118.9
O3—Co—O2^ii	89.04 (10)	C3—C4—H4	118.9
N1—Co—O2^ii	89.91 (10)	C4—C5—C6	117.3 (4)
O1—Co—O5	86.27 (10)	C4—C5—H5	121.3
O4^i—Co—O5	90.10 (10)	C6—C5—H5	121.3
O3—Co—O5	87.98 (10)	C5—C6—N1	130.4 (4)
N1—Co—O5	175.65 (11)	C5—C6—C7	120.5 (4)
O2^ii—Co—O5	94.39 (9)	N1—C6—C7	109.1 (3)
C8—O1—Co	128.5 (2)	N2—C7—C2	134.7 (4)
C8—O2—Co^iii	123.5 (2)	N2—C7—C6	104.3 (3)
C10—O3—Co	127.4 (2)	C2—C7—C6	121.0 (4)
C10—O4—Co^iv	131.0 (2)	O1—C8—O2	123.3 (3)
Co—O5—H51	107.13	O1—C8—C9	119.1 (3)
Co—O5—H52	112.87	O2—C8—C9	117.6 (3)
H51—O5—H52	103.1	C8—C9—C10	115.6 (3)
C1—N1—C6	104.6 (3)	C8—C9—H9A	108.4
C1—N1—Co	121.6 (2)	C10—C9—H9A	108.4
C6—N1—Co	133.8 (3)	C8—C9—H9B	108.4
C1—N2—C7	109.7 (3)	C10—C9—H9B	108.4
C1—N2—H2	125.2	H9A—C9—H9B	107.4
C7—N2—H2	125.2	O4—C10—O3	124.0 (3)
N1—C1—N2	112.4 (3)	O4—C10—C9	116.3 (3)
N1—C1—H1	123.8	O3—C10—C9	119.6 (3)
N2—C1—H1	123.8

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H52···O3^i	0.98	1.85	2.689 (3)	143
O5—H51···O1^ii	0.89	1.90	2.672 (3)	143
N2—H2···O2^iv	0.86	2.43	3.078 (4)	132

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