Poly[diaqua­(μ₃-1H-benzimidazole-5,6-dicarboxyl­ato-κ⁴N³:O⁵,O⁶:O^6′)magnesium(II)]

In the title complex, [Mg(C₉H₄N₂O₄)(H₂O)₂]_n, the Mg^II atom is six-coordinated by one N and three O atoms from three different 1H-benzimidazole-5,6-dicarboxyl­ate ligands and two O atoms from two water mol­ecules, forming a slightly distorted octa­hedral geometry. The ligand links the Mg^II centres into a three-dimensional network. Extensive N—H...O and O—H...O hydrogen bonds exist between the ligands and water mol­ecules, stabilizing the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.036
• wR factor = 0.090
• Data-to-parameter ratio = 7.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.96
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       7.01
PLAT340_ALERT_3_C Low Bond Precision on  C-C Bonds (x 1000) Ang ..          5
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          2
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         25
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         18

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.49
           From the CIF: _reflns_number_total               1143
           Count of symmetry unique reflns         1187
           Completeness (_total/calc)             96.29%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          2
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        293 K

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

   2 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
   6 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

1H-Benzimidazole-5,6-dicarboxylic acid (H₂L) can function as a multidentate ligand and several complexes formed from this ligand have been reported recently, including catena-poly[[diaqua(1,10-phenanthroline-κ²N,N') nickel(II)]-µ-L-κ²N³:O⁶] (Song, Wang, Hu et al., 2009), pentaaqua(L-κN³)cobalt(II) pentahydrate (Song, Wang, Li et al., 2009), pentaaqua(L-κN³)nickel(II) pentahydrate (Song, Wang, Qin et al., 2009) and tetraaquabis(L-κN³)cobalt(II) dimethylformamide disolvate dihydrate (Wang et al., 2009). However, the Mg complex of the H₂L ligand has not been reported up to now.

As shown in Fig. 1, the Mg^II atom is six-coordinated by one N and three O atoms from three different L ligands, and two O atoms from two water molecules (Table 1), showing a slightly distorted octahedral geometry. The equatorial plane is defined by O1W, O2W, O1ⁱ and O3ⁱ atoms, while N1 and O4ⁱⁱ occupy the axial positions [symmetry codes: (i) x, 1 - y, -1/2 + z; (ii) 1/2 + x, 1/2 + y, z]. Intermolecular O—H···O and N—H···O hydrogen bonds between the ligand and the coordinated water molecules stabilize the structure (Table 2 and Fig 2).

Related literature

For related structures of 1H-benzimidazole-5,6-dicarboxylate complexes, see: Song, Wang, Hu et al. (2009); Song, Wang, Li et al. (2009); Song, Wang, Qin et al. (2009); Wang et al. (2009).

S2. Experimental

A mixture of MgCl₂ (1.0 mmol), H₂L (0.6 mmol), CH₃CN (6 ml) and water (4 ml) was added to a 20 ml Teflon-lined stainless container, which was heated to 150°C and held at that temperature for 5 d. After cooling to room temperature, colourless crystals were recovered by filtration.

S3. Refinement

C– and N-bound H atoms were placed at calculated positions and treated as riding on the parent C or N atoms, with C—H = 0.93 and N—H = 0.86 Å, and with U_iso(H) = 1.2U_eq(C, N). The water H atoms were located in a difference Fourier map and refined as riding with a distance restraint of O—H = 0.84 Å and with U_iso(H) = 1.5U_eq(O).

Computing details

Data collection: CrystalStructure (Rigaku/MSC, 2002); cell refinement: CrystalStructure (Rigaku/MSC, 2002); data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The structure of the title compound, showing the 30% probability displacement ellipsoids. [Symmetry codes: (i) x, 1 - y, -1/2 + z; (ii) 1/2 + x, 1/2 + y, z.]
	Fig. 2. A view of the three-dimensional network structure of the title compound. Hydrogen bonds are shown as dashed lines.

Poly[diaqua(µ₃-1H-benzimidazole-5,6-dicarboxylato- κ⁴N³:O⁵,O⁶:O^6')magnesium(II)]

Crystal data

[Mg(C9H4N2O4)(H2O)2]	F(000) = 544
Mr = 264.48	Dx = 1.717 Mg m^−3
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C -2yc	Cell parameters from 4114 reflections
a = 7.4793 (15) Å	θ = 3.6–27.5°
b = 18.958 (4) Å	µ = 0.20 mm^−1
c = 7.3132 (15) Å	T = 293 K
β = 99.38 (3)°	Block, colourless
V = 1023.1 (4) Å^3	0.30 × 0.25 × 0.21 mm
Z = 4

Data collection

Rigaku/MSC Mercury CCD diffractometer	1143 independent reflections
Radiation source: fine-focus sealed tube	1096 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
ω scans	θmax = 27.5°, θmin = 3.6°
Absorption correction: multi-scan (REQAB; Jacobson, 1998)	h = −9→9
Tmin = 0.943, Tmax = 0.960	k = −24→24
4611 measured reflections	l = −8→9

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.090	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.04P)^2 + 2P] where P = (Fo^2 + 2Fc^2)/3
1143 reflections	(Δ/σ)max < 0.001
163 parameters	Δρmax = 0.38 e Å^−3
2 restraints	Δρmin = −0.25 e Å^−3

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

	x	y	z	Uiso*/Ueq
Mg1	0.27807 (16)	0.68928 (5)	0.63241 (16)	0.0172 (3)
O1	0.4349 (4)	0.37147 (14)	0.9888 (4)	0.0234 (5)
O2	0.5047 (4)	0.37926 (16)	0.7087 (4)	0.0317 (7)
O3	0.1320 (4)	0.28489 (12)	0.8699 (4)	0.0237 (6)
O4	−0.0733 (4)	0.28304 (12)	0.6132 (3)	0.0236 (6)
N1	0.0678 (5)	0.61142 (15)	0.6633 (5)	0.0214 (6)
N3	−0.2035 (5)	0.56134 (16)	0.6122 (5)	0.0271 (7)
H3	−0.3196	0.5577	0.5874	0.033*
C1	0.0380 (5)	0.31481 (16)	0.7326 (5)	0.0173 (6)
C2	0.0549 (5)	0.39389 (16)	0.7123 (5)	0.0182 (7)
C3	−0.1002 (5)	0.43318 (18)	0.6560 (5)	0.0223 (7)
H2	−0.2127	0.4116	0.6240	0.027*
C4	−0.0816 (5)	0.50629 (18)	0.6490 (5)	0.0206 (7)
C5	0.0876 (5)	0.53907 (17)	0.6828 (5)	0.0184 (7)
C6	0.2438 (5)	0.49930 (18)	0.7332 (5)	0.0185 (7)
H1	0.3574	0.5206	0.7531	0.022*
C7	0.2259 (4)	0.42738 (16)	0.7529 (4)	0.0154 (6)
C8	0.3985 (5)	0.38839 (17)	0.8204 (5)	0.0173 (7)
C9	−0.1073 (6)	0.62155 (18)	0.6224 (6)	0.0262 (8)
H9	−0.1599	0.6659	0.6023	0.031*
O1W	0.4663 (4)	0.65596 (14)	0.8537 (4)	0.0289 (6)
H1W	0.4573	0.6408	0.9598	0.043*
H2W	0.5355	0.6911	0.8601	0.043*
O2W	0.1388 (5)	0.75021 (15)	0.7982 (5)	0.0374 (8)
H3W	0.0660	0.7342	0.8639	0.056*
H4W	0.1176	0.7927	0.7704	0.056*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mg1	0.0191 (6)	0.0134 (4)	0.0184 (5)	−0.0004 (4)	0.0009 (4)	0.0004 (4)
O1	0.0186 (13)	0.0310 (13)	0.0202 (12)	0.0004 (10)	0.0019 (11)	0.0074 (10)
O2	0.0247 (16)	0.0462 (17)	0.0253 (14)	0.0133 (12)	0.0075 (12)	0.0005 (12)
O3	0.0274 (14)	0.0165 (11)	0.0235 (12)	−0.0008 (10)	−0.0074 (11)	0.0006 (9)
O4	0.0281 (15)	0.0195 (12)	0.0203 (13)	−0.0067 (10)	−0.0045 (11)	0.0014 (9)
N1	0.0215 (16)	0.0167 (13)	0.0265 (15)	0.0018 (11)	0.0058 (12)	0.0039 (11)
N3	0.0147 (16)	0.0249 (14)	0.0400 (19)	0.0032 (12)	−0.0009 (14)	0.0065 (13)
C1	0.0195 (17)	0.0151 (13)	0.0175 (16)	−0.0016 (12)	0.0043 (14)	−0.0002 (11)
C2	0.0197 (18)	0.0150 (14)	0.0192 (16)	−0.0024 (12)	0.0008 (14)	0.0015 (12)
C3	0.0184 (18)	0.0204 (16)	0.0274 (19)	−0.0040 (13)	0.0011 (15)	0.0023 (13)
C4	0.0151 (19)	0.0216 (16)	0.0244 (18)	0.0023 (12)	0.0011 (14)	0.0045 (13)
C5	0.0191 (17)	0.0160 (14)	0.0203 (16)	−0.0019 (12)	0.0035 (14)	0.0016 (12)
C6	0.0129 (16)	0.0198 (15)	0.0224 (17)	−0.0022 (11)	0.0018 (14)	0.0008 (12)
C7	0.0151 (16)	0.0178 (14)	0.0134 (14)	0.0002 (12)	0.0027 (13)	−0.0002 (11)
C8	0.0154 (17)	0.0154 (14)	0.0204 (17)	−0.0024 (11)	0.0007 (14)	−0.0011 (11)
C9	0.024 (2)	0.0208 (16)	0.034 (2)	0.0068 (14)	0.0050 (17)	0.0067 (14)
O1W	0.0340 (15)	0.0271 (13)	0.0225 (12)	−0.0071 (11)	−0.0043 (12)	0.0052 (10)
O2W	0.0486 (19)	0.0219 (12)	0.0476 (19)	0.0063 (12)	0.0251 (16)	−0.0022 (12)

Geometric parameters (Å, º)

Mg1—N1	2.195 (3)	C1—C2	1.514 (4)
Mg1—O1^i	2.051 (3)	C2—C3	1.384 (5)
Mg1—O3^i	2.106 (3)	C2—C7	1.416 (5)
Mg1—O4^ii	2.113 (3)	C3—C4	1.395 (5)
Mg1—O1W	2.063 (3)	C3—H2	0.9300
Mg1—O2W	2.074 (3)	C4—C5	1.395 (5)
O1—C8	1.259 (4)	C5—C6	1.388 (5)
O2—C8	1.241 (4)	C6—C7	1.380 (5)
O3—C1	1.263 (4)	C6—H1	0.9300
O4—C1	1.257 (4)	C7—C8	1.499 (5)
N1—C9	1.310 (5)	C9—H9	0.9300
N1—C5	1.384 (4)	O1W—H1W	0.8401
N3—C9	1.345 (5)	O1W—H2W	0.8400
N3—C4	1.383 (5)	O2W—H3W	0.8399
N3—H3	0.8600	O2W—H4W	0.8400
O1^i—Mg1—O1W	81.69 (12)	C7—C2—C1	120.7 (3)
O1^i—Mg1—O2W	174.71 (15)	C2—C3—C4	117.5 (3)
O1W—Mg1—O2W	93.18 (14)	C2—C3—H2	121.2
O1^i—Mg1—O3^i	85.34 (12)	C4—C3—H2	121.3
O1W—Mg1—O3^i	166.51 (13)	N3—C4—C3	133.6 (3)
O2W—Mg1—O3^i	99.68 (13)	N3—C4—C5	104.4 (3)
O1^i—Mg1—O4^ii	95.02 (12)	C3—C4—C5	122.0 (3)
O1W—Mg1—O4^ii	90.61 (11)	N1—C5—C6	129.5 (3)
O2W—Mg1—O4^ii	83.68 (12)	N1—C5—C4	110.1 (3)
O3^i—Mg1—O4^ii	86.80 (11)	C6—C5—C4	120.3 (3)
O1^i—Mg1—N1	98.87 (12)	C7—C6—C5	118.2 (3)
O1W—Mg1—N1	97.00 (12)	C7—C6—H1	120.9
O2W—Mg1—N1	82.98 (13)	C5—C6—H1	120.9
O3^i—Mg1—N1	88.65 (12)	C6—C7—C2	121.4 (3)
O4^ii—Mg1—N1	164.98 (12)	C6—C7—C8	115.4 (3)
C8—O1—Mg1^iii	126.4 (2)	C2—C7—C8	123.2 (3)
C1—O3—Mg1^iii	139.4 (2)	O2—C8—O1	123.3 (3)
C1—O4—Mg1^iv	130.8 (2)	O2—C8—C7	117.5 (3)
C9—N1—C5	104.8 (3)	O1—C8—C7	119.0 (3)
C9—N1—Mg1	125.8 (2)	N1—C9—N3	113.2 (3)
C5—N1—Mg1	127.6 (3)	N1—C9—H9	123.4
C9—N3—C4	107.4 (3)	N3—C9—H9	123.4
C9—N3—H3	126.3	Mg1—O1W—H1W	133.0
C4—N3—H3	126.3	Mg1—O1W—H2W	97.9
O4—C1—O3	123.8 (3)	H1W—O1W—H2W	111.1
O4—C1—C2	117.6 (3)	Mg1—O2W—H3W	124.6
O3—C1—C2	118.6 (3)	Mg1—O2W—H4W	119.1
C3—C2—C7	120.4 (3)	H3W—O2W—H4W	111.8
C3—C2—C1	118.9 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···O1^v	0.86	2.29	2.992 (4)	138
O1W—H1W···O2^iii	0.84	1.84	2.651 (4)	163
O1W—H2W···O3^ii	0.84	1.92	2.734 (4)	164
O2W—H3W···O4^iii	0.84	2.27	3.068 (4)	160
O2W—H4W···O2^vi	0.84	1.87	2.685 (4)	164

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