catena-Poly­[[di­aqua­bis(1H-benz­imidazole-κN³)­nickel(II)]-μ-succinato-κ²O:O′]

The crystal structure of the title compound, [Ni(C₄H₄O₄)(C₇H₆N₂)₂(H₂O)₂]_n, consists of a polymeric Ni^II complex bridged by succinate dianions. The Ni atom is located at a crystallographic inversion center. Both carboxyl groups of the succinate coordinate, in monodentate fashion, to the neighboring Ni^II atoms to form one-dimensional chains, and the chains link to each other via hydrogen bonds between the benz­imidazole and carboxyl group to form a two-dimensional supramolecular structure. The overlapped arrangement of parallel benz­imidazole ligands, with a separation of 3.350 (3) Å, suggests the existence of π–π-stacking interactions between adjacent chains.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.028
• wR factor = 0.074
• Data-to-parameter ratio = 15.3

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S1. Comment

A series of transition metal complexes bridged by dicarboxylate, such as fumarate, succinate, etc., has been prepared in the laboratory. Their crystal structures show versatile coordination modes of the carboxyl groups (Chen et al., 2003). As part of this research, the structure of the title nickel(II) complex, (I), bridged by succinate has been determined by X-ray diffraction methods.

The crystal structure consists of polymeric Ni^II complex molecules. The coordination environment around the Ni^II atom is illustrated in Fig. 1. The Ni^II atom is located in a crystallographic inversion center. Together with two water molecules, two O atoms from different succinate ligands and two imidazole N atoms coordinate to a Ni^II atom with an octahedron geometry (see Table 1). The carboxyl groups of the succinate display as monodentate ligand, the uncoordinated carboxyl O atoms form hydrogen bonding with the neighboring coordinated water.

The succinate group located around another inversion center. The planar carbon skeleton inclines to the carboxyl group with a dihedral angle of 56.6 (2)°. Carboxyl groups of the succinate coordinate to the neighboring Ni^II atoms to form the one-dimensional polymeric chains. The adjacent chains link to each other via hydrogen bonding between the benzimidazole nitrogen and carboxyl oxygen atoms, forming the two-dimensional supramolecular structure shown in Fig. 2 and Table 2.

An overlapped disposition of parallel benzimidazole ligands is observed in the crystal structure. Neighboring benzimidazole ligands, related by the symmetry transformation (-x, 1 − y, −z), are separated by 3.350 (3) Å. These findings suggest the existence of π–π-stacking interactions between adjacent polymeric chains.

S2. Experimental

NiCl₂·6H₂O (0.48 g, 2 mmol) was added to an aqueous solution (10 ml) containing succinic acid (0.24 g, 2 mmol) and NaOH (0.16 g, 4 mmol). After the mixture was refluxed for 30 min, an ethanol solution (10 ml) of benzimidazole (0.24 g, 2 mmol) was added to the above solution with continuous stirring. The solution was refluxed for 3 h, until the color changed to pale green. The reaction mixture was cooled to room temperature and filtered. Pale green single crystals were obtained from the filtrate after one week.

S3. Refinement

The H atoms on C atoms were placed in calculated positions, with C—H = 0.93–0.97 Å, and included in the final cycles of refinement as riding, with U_iso(H) = 1.2U_eq of the carrier atoms. H atoms of water were placed in calculation positions (Nardelli, 1993), and were included in the final cycles of refinement with fixed coordinates and isotropic displacement parameters of 0.08 Ų.

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 molecular structure of (I), with 50% probability displacement ellipsoids. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) −x,-y, 1 − z.]
	Fig. 2. The molecular packing diagram, with dashed lines showing hydrogen bonding.

catena-Poly[[diaquabis(1H-benzimidazole-κN³)nickel(II)]-µ-succinato- k²O:O']

Crystal data

[Ni(C4H4O4)(C7H6N2)2(H2O)2]	Z = 1
Mr = 447.08	F(000) = 232
Triclinic, P1	Dx = 1.646 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.0244 (7) Å	Cell parameters from 2206 reflections
b = 8.5982 (11) Å	θ = 2.6–27.4°
c = 8.7399 (5) Å	µ = 1.12 mm^−1
α = 100.248 (6)°	T = 298 K
β = 111.981 (7)°	Prism, green
γ = 104.734 (9)°	0.39 × 0.19 × 0.11 mm
V = 450.91 (9) Å^3

Data collection

Rigaku R-AXIS RAPID diffractometer	2036 independent reflections
Radiation source: fine-focus sealed tube	1913 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.015
Detector resolution: 10.00 pixels mm^-1	θmax = 27.5°, θmin = 2.6°
ω scans	h = −8→9
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −11→11
Tmin = 0.64, Tmax = 0.88	l = −11→11
4252 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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.074	H-atom parameters constrained
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0375P)^2 + 0.2892P] where P = (Fo^2 + 2Fc^2)/3
2036 reflections	(Δ/σ)max < 0.001
133 parameters	Δρmax = 0.59 e Å^−3
0 restraints	Δρmin = −0.43 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
Ni	0.5000	0.5000	0.5000	0.01674 (10)
O1	0.2572 (2)	0.26719 (15)	0.42382 (16)	0.0223 (3)
O2	0.0967 (2)	0.32317 (16)	0.59500 (17)	0.0267 (3)
O3	0.6927 (2)	0.37982 (16)	0.42754 (17)	0.0255 (3)
N1	0.2349 (3)	0.4384 (2)	−0.0384 (2)	0.0274 (3)
H1	0.1875	0.3759	−0.1428	0.033*
N3	0.3693 (2)	0.51412 (19)	0.24894 (19)	0.0220 (3)
C2	0.3061 (3)	0.3921 (2)	0.1062 (2)	0.0267 (4)
H2	0.3104	0.2847	0.1054	0.032*
C4	0.3732 (3)	0.8149 (2)	0.2864 (2)	0.0266 (4)
H4	0.4291	0.8477	0.4065	0.032*
C5	0.3231 (4)	0.9261 (3)	0.1941 (3)	0.0347 (5)
H5	0.3469	1.0356	0.2533	0.042*
C6	0.2372 (4)	0.8762 (3)	0.0130 (3)	0.0408 (5)
H6	0.2051	0.9538	−0.0451	0.049*
C7	0.1991 (4)	0.7161 (3)	−0.0812 (3)	0.0358 (5)
H7	0.1409	0.6834	−0.2014	0.043*
C8	0.2519 (3)	0.6049 (2)	0.0121 (2)	0.0240 (4)
C9	0.3368 (3)	0.6521 (2)	0.1932 (2)	0.0212 (3)
C11	0.1251 (3)	0.2230 (2)	0.4862 (2)	0.0203 (3)
C12	−0.0135 (3)	0.0370 (2)	0.4253 (2)	0.0276 (4)
H12A	0.0277	−0.0249	0.3462	0.033*
H12B	−0.1666	0.0230	0.3623	0.033*
H13	0.7902	0.3340	0.4474	0.080*
H23	0.6808	0.4112	0.3376	0.080*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.01906 (16)	0.01398 (15)	0.01748 (16)	0.00472 (11)	0.00874 (12)	0.00552 (11)
O1	0.0237 (6)	0.0179 (6)	0.0239 (6)	0.0030 (5)	0.0119 (5)	0.0061 (5)
O2	0.0324 (7)	0.0223 (6)	0.0295 (7)	0.0079 (5)	0.0185 (6)	0.0088 (5)
O3	0.0293 (7)	0.0244 (6)	0.0298 (7)	0.0129 (5)	0.0170 (6)	0.0102 (5)
N1	0.0330 (8)	0.0291 (8)	0.0174 (7)	0.0122 (7)	0.0092 (6)	0.0037 (6)
N3	0.0250 (7)	0.0195 (7)	0.0198 (7)	0.0065 (6)	0.0086 (6)	0.0064 (6)
C2	0.0298 (9)	0.0225 (9)	0.0249 (9)	0.0081 (7)	0.0102 (8)	0.0061 (7)
C4	0.0318 (10)	0.0237 (9)	0.0220 (9)	0.0089 (7)	0.0101 (8)	0.0066 (7)
C5	0.0480 (12)	0.0252 (9)	0.0353 (11)	0.0170 (9)	0.0191 (10)	0.0117 (8)
C6	0.0610 (15)	0.0406 (12)	0.0366 (12)	0.0296 (11)	0.0241 (11)	0.0252 (10)
C7	0.0500 (13)	0.0461 (12)	0.0226 (9)	0.0276 (11)	0.0175 (9)	0.0178 (9)
C8	0.0249 (8)	0.0291 (9)	0.0205 (8)	0.0115 (7)	0.0111 (7)	0.0081 (7)
C9	0.0214 (8)	0.0231 (8)	0.0203 (8)	0.0073 (7)	0.0098 (7)	0.0090 (6)
C11	0.0215 (8)	0.0184 (8)	0.0191 (8)	0.0054 (7)	0.0068 (7)	0.0087 (6)
C12	0.0326 (10)	0.0186 (8)	0.0247 (9)	−0.0004 (7)	0.0115 (8)	0.0069 (7)

Geometric parameters (Å, º)

Ni—O1	2.0733 (12)	C2—H2	0.930
Ni—O1^i	2.0733 (12)	C4—C5	1.386 (3)
Ni—N3^i	2.0774 (14)	C4—C9	1.395 (3)
Ni—N3	2.0774 (14)	C4—H4	0.930
Ni—O3^i	2.1028 (13)	C5—C6	1.402 (3)
Ni—O3	2.1028 (13)	C5—H5	0.930
O1—C11	1.255 (2)	C6—C7	1.374 (3)
O2—C11	1.274 (2)	C6—H6	0.930
O3—H13	0.852	C7—C8	1.396 (3)
O3—H23	0.857	C7—H7	0.930
N1—C2	1.346 (2)	C8—C9	1.403 (2)
N1—C8	1.381 (2)	C11—C12	1.519 (2)
N1—H1	0.860	C12—C12^ii	1.523 (3)
N3—C2	1.318 (2)	C12—H12A	0.970
N3—C9	1.399 (2)	C12—H12B	0.970
O1—Ni—N3^i	89.63 (5)	C5—C4—H4	121.1
O1^i—Ni—N3^i	90.37 (5)	C9—C4—H4	121.1
O1—Ni—N3	90.37 (5)	C4—C5—C6	121.14 (19)
O1^i—Ni—N3	89.63 (5)	C4—C5—H5	119.4
O1—Ni—O3^i	90.09 (5)	C6—C5—H5	119.4
O1^i—Ni—O3^i	89.91 (5)	C7—C6—C5	121.95 (19)
N3^i—Ni—O3^i	86.82 (6)	C7—C6—H6	119.0
N3—Ni—O3^i	93.18 (6)	C5—C6—H6	119.0
O1—Ni—O3	89.91 (5)	C6—C7—C8	116.83 (18)
O1^i—Ni—O3	90.09 (5)	C6—C7—H7	121.6
N3^i—Ni—O3	93.18 (6)	C8—C7—H7	121.6
N3—Ni—O3	86.82 (6)	N1—C8—C7	132.46 (17)
C11—O1—Ni	128.20 (11)	N1—C8—C9	105.44 (16)
Ni—O3—H13	153.31	C7—C8—C9	122.09 (18)
Ni—O3—H23	98.14	C4—C9—N3	130.81 (16)
H13—O3—H23	106.84	C4—C9—C8	120.20 (17)
C2—N1—C8	107.32 (15)	N3—C9—C8	108.99 (16)
C2—N1—H1	126.3	O1—C11—O2	124.76 (15)
C8—N1—H1	126.3	O1—C11—C12	117.57 (16)
C2—N3—C9	105.01 (15)	O2—C11—C12	117.67 (16)
C2—N3—Ni	126.03 (13)	C11—C12—C12^ii	112.42 (18)
C9—N3—Ni	128.92 (12)	C11—C12—H12A	109.1
N3—C2—N1	113.25 (17)	C12^ii—C12—H12A	109.1
N3—C2—H2	123.4	C11—C12—H12B	109.1
N1—C2—H2	123.4	C12^ii—C12—H12B	109.1
C5—C4—C9	117.79 (18)	H12A—C12—H12B	107.9

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2^iii	0.86	2.06	2.871 (2)	156
O3—H13···O2^iv	0.85	2.09	2.878 (2)	153
O3—H23···O2^i	0.86	2.24	2.688 (2)	112

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