catena-Poly­[[di­aqua­bis­(benz­imidazole-κN)­cobalt(II)]-μ-fumarato-κ²O¹:O⁴]

The title polymeric complex, [Co(μ-C₄H₂O₄)(C₇H₆N₂)₂(H₂O)₂]_n, displays a one-dimensional chain structure bridged by fumarate dianions. In the crystal structure, the polymeric chains are linked to each other by hydrogen bonds. The overlapped arrangement and the short separation of 3.35 (2) Å suggest the existence of π–π stacking between parallel benz­imidazole rings. The Co^II atom exists in a centrosymmetric octahedral geometry.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.045
• wR factor = 0.113
• Data-to-parameter ratio = 12.2

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .....       0.99
PLAT341_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang..          8

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

The aromatic π–π-stacking interaction has shown to be correlated with the electron transfer in some biological system (Deisenhofer & Michel, 1989). As part of investigation on the π–π-stacking interaction in metal complexes (Chen, 2003), the title polymeric Co^II complex, (I), with the benzimidazole ligand has recently been prepared in the laboratory.

The coordination environment around the Co^II atom in (I) is illustrated in Fig. 1. The Co^II atom is located at an inversion center and possesses an octahedral coordinate geometry formed by benzimidazole molecules, water molecules and fumarate dianions with the normal geometry parameters (Table 1). The carboxyl group of the fumarate dianion coordinates in a monodentate manner to the Co^II atom. The uncoordinated carboxyl O atom (O2) is hydrogen bonded to the neighboring benzimidazole and coordinated water molecules (Fig. 1).

Each fumarate dianion bridges two Co^II atoms through both terminal carboxyl groups to form polymeric complex chains as shown in Fig. 2. Adjacent polymeric chains link each other by hydrogen bonds (Table 2). The overlapped arrangement of benzimidazole rings is observed between the adjacent complex molecules related by an inversion center (Fig. 3). The shorter separation of 3.35 (2) Å between neighboring parallel benzimidazole rings suggests the existence of the π–π stacking.

S2. Experimental

An ethanol solution (5 ml) of benzimidazole (0.24 g, 2 mmol) was mixed with an aqueous solution (5 ml) of CoCl₂·6H₂O (0.24 g, 1 mmol) at room temperature. After refluxing the solution for 30 min, an aqueous solution (5 ml) containing fumaric acid (0.12 g, 1 mmol) and NaOH (0.08 g, 2 mmol) was added. The mixture was refluxed for 1 h and filtered. The pink single crystals were obtained after 2 d.

S3. Refinement

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

Computing details

Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; 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) and XP (Siemens, 1994); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The coordination environment around the Co^II atom in (I), with 50% probability displacement ellipsoids. Dashed lines indicate the hydrogen bonding [symmetry codes: (i)-x, −y, 1 − z; (ii) 1 − x, 1 − y, 2 − z; (iii) −x, 1 − y, 1 − z; (iv) 1 − x, 1 − y, 1 − z].
	Fig. 2. The molecular packing diagram, dashed lines indicate the hydrogen bonging between adjacent polymeric chains.
	Fig. 3. A diagram showing the π–π stacking between neighboring benzimidazole rings [symmetry code: (v) 2 − x, 1 − y, 2 − z].

(I)

Crystal data

[Co(C4H2O4)(C7H6N2)2(H2O)2]	Z = 1
Mr = 445.29	F(000) = 229
Triclinic, P1	Dx = 1.625 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.0668 (10) Å	Cell parameters from 1988 reflections
b = 8.5150 (12) Å	θ = 2.0–23.0°
c = 8.7929 (13) Å	µ = 0.99 mm^−1
α = 99.358 (11)°	T = 150 K
β = 113.322 (13)°	Prism, pink
γ = 102.787 (12)°	0.32 × 0.30 × 0.22 mm
V = 454.95 (13) Å^3

Data collection

Bruker SMART CCD diffractometer	1623 independent reflections
Radiation source: fine-focus sealed tube	996 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.053
ω and ϕ scans	θmax = 25.2°, θmin = 2.6°
Absorption correction: empirical (using intensity measurements) (SADABS; Bruker, 1999)	h = −8→4
Tmin = 0.722, Tmax = 0.802	k = −9→10
2497 measured reflections	l = −10→10

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.113	H-atom parameters constrained
S = 0.91	w = 1/[σ^2(Fo^2) + (0.0269P)^2 + 0.2058P] where P = (Fo^2 + 2Fc^2)/3
1623 reflections	(Δ/σ)max < 0.001
133 parameters	Δρmax = 0.51 e Å^−3
0 restraints	Δρmin = −0.50 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	0.5000	0.5000	0.5000	0.0168 (3)
O1	0.2738 (5)	0.2672 (4)	0.4332 (4)	0.0183 (9)
O2	0.1069 (5)	0.3189 (4)	0.5978 (4)	0.0173 (8)
O3	0.2983 (5)	0.6180 (4)	0.5682 (4)	0.0194 (9)
N1	0.7701 (6)	0.5607 (5)	1.0466 (5)	0.0190 (10)
H1	0.8158	0.6230	1.1493	0.023*
N3	0.6309 (6)	0.4838 (5)	0.7561 (5)	0.0179 (10)
C2	0.6941 (8)	0.6059 (6)	0.8993 (6)	0.0201 (13)
H2	0.6862	0.7132	0.8974	0.024*
C4	0.6366 (8)	0.1839 (6)	0.7264 (6)	0.0204 (13)
H4	0.5786	0.1505	0.6068	0.025*
C5	0.6938 (9)	0.0747 (7)	0.8255 (7)	0.0269 (14)
H5	0.6712	−0.0352	0.7697	0.032*
C6	0.7858 (8)	0.1247 (7)	1.0094 (6)	0.0277 (14)
H6	0.8256	0.0485	1.0706	0.033*
C7	0.8158 (8)	0.2843 (7)	1.0963 (7)	0.0247 (13)
H7	0.8717	0.3170	1.2158	0.030*
C8	0.7606 (7)	0.3943 (6)	1.0008 (6)	0.0176 (12)
C9	0.6715 (8)	0.3471 (6)	0.8175 (6)	0.0161 (12)
C11	0.1553 (8)	0.2211 (6)	0.5030 (6)	0.0169 (12)
C12	0.0596 (8)	0.0350 (6)	0.4656 (6)	0.0207 (13)
H12	0.0862	−0.0350	0.3889	0.025*
H31	0.2250	0.5256	0.6003	0.050*
H32	0.1829	0.6475	0.5039	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co	0.0184 (6)	0.0157 (6)	0.0172 (6)	0.0054 (5)	0.0089 (5)	0.0045 (5)
O1	0.022 (2)	0.017 (2)	0.0192 (19)	0.0031 (16)	0.0141 (17)	0.0045 (16)
O2	0.024 (2)	0.012 (2)	0.022 (2)	0.0062 (16)	0.0152 (17)	0.0050 (16)
O3	0.017 (2)	0.021 (2)	0.025 (2)	0.0078 (16)	0.0107 (17)	0.0097 (17)
N1	0.025 (3)	0.018 (3)	0.011 (2)	0.007 (2)	0.007 (2)	0.001 (2)
N3	0.022 (2)	0.016 (3)	0.021 (2)	0.007 (2)	0.014 (2)	0.007 (2)
C2	0.029 (3)	0.012 (3)	0.020 (3)	0.006 (2)	0.013 (3)	0.004 (2)
C4	0.028 (3)	0.018 (3)	0.018 (3)	0.006 (2)	0.012 (3)	0.006 (2)
C5	0.042 (4)	0.017 (3)	0.032 (3)	0.013 (3)	0.024 (3)	0.010 (3)
C6	0.035 (4)	0.032 (4)	0.022 (3)	0.020 (3)	0.011 (3)	0.016 (3)
C7	0.025 (3)	0.032 (4)	0.017 (3)	0.014 (3)	0.007 (3)	0.008 (3)
C8	0.014 (3)	0.020 (3)	0.016 (3)	0.003 (2)	0.007 (2)	−0.001 (3)
C9	0.019 (3)	0.018 (3)	0.018 (3)	0.006 (2)	0.012 (2)	0.010 (2)
C11	0.018 (3)	0.019 (3)	0.014 (3)	0.007 (2)	0.006 (2)	0.007 (2)
C12	0.029 (3)	0.015 (3)	0.026 (3)	0.008 (2)	0.021 (3)	0.003 (2)

Geometric parameters (Å, º)

Co—O1	2.075 (3)	C4—C5	1.392 (7)
Co—N3	2.110 (4)	C4—C9	1.402 (7)
Co—O3	2.125 (3)	C4—H4	0.93
O1—C11	1.253 (5)	C5—C6	1.428 (7)
O2—C11	1.278 (5)	C5—H5	0.93
O3—H31	0.987	C6—C7	1.372 (7)
O3—H32	0.905	C6—H6	0.93
N1—C2	1.348 (6)	C7—C8	1.375 (7)
N1—C8	1.387 (6)	C7—H7	0.93
N1—H1	0.86	C8—C9	1.425 (6)
N3—C2	1.338 (6)	C11—C12	1.502 (7)
N3—C9	1.399 (6)	C12—C12^i	1.315 (8)
C2—H2	0.93	C12—H12	0.93
O1—Co—N3	87.60 (13)	C4—C5—H5	118.7
O1—Co—O3	89.97 (12)	C6—C5—H5	118.7
N3—Co—O3	85.64 (14)	C7—C6—C5	120.5 (5)
C11—O1—Co	128.1 (3)	C7—C6—H6	119.8
Co—O3—H31	98.1	C5—C6—H6	119.8
Co—O3—H32	131.6	C6—C7—C8	117.8 (5)
H31—O3—H32	100.1	C6—C7—H7	121.1
C2—N1—C8	106.9 (4)	C8—C7—H7	121.1
C2—N1—H1	126.5	C7—C8—N1	132.4 (5)
C8—N1—H1	126.5	C7—C8—C9	122.4 (5)
C2—N3—C9	103.7 (4)	N1—C8—C9	105.1 (4)
C2—N3—Co	126.9 (3)	N3—C9—C4	129.7 (5)
C9—N3—Co	129.4 (3)	N3—C9—C8	109.7 (4)
N3—C2—N1	114.5 (5)	C4—C9—C8	120.6 (5)
N3—C2—H2	122.8	O1—C11—O2	125.3 (5)
N1—C2—H2	122.8	O1—C11—C12	116.0 (4)
C5—C4—C9	116.0 (5)	O2—C11—C12	118.6 (4)
C5—C4—H4	122.0	C12^i—C12—C11	124.1 (6)
C9—C4—H4	122.0	C12^i—C12—H12	117.9
C4—C5—C6	122.7 (5)	C11—C12—H12	117.9

Symmetry code: (i) −x, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H31···O2	0.99	1.77	2.712 (5)	159
O3—H32···O2^ii	0.91	1.99	2.871 (5)	163
N1—H1···O2^iii	0.86	2.01	2.827 (5)	158

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