Bis[μ-bis(imidazol­-1-yl)methane]bis[aqua(oxalato)copper(II)] dihydrate

The title compound, [Cu₂(C₂O₄)₂(C₇H₈N₄)₂(H₂O)₂]·2H₂O, features a centrosymmetric dinuclear complex. The Cu^II ion adopts a square-pyramidal geometry. It is coordinated by two N atoms from two bis­(N-imidazolyl)methane mol­ecules as bridging ligands, two O atoms from one oxalate anion in chelating mode and one water mol­ecule. There are several O—H...O hydrogen bonds in the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.027
• wR factor = 0.072
• Data-to-parameter ratio = 12.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.89
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT153_ALERT_1_C The su's on the Cell Axes   are Equal (x 100000)        400 Ang.
PLAT213_ALERT_2_C Atom O4      has ADP max/min Ratio .............       3.10 prola
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.38
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C8     -   C9     ...       1.54 Ang.

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.886
            Tmax scaled      0.432 Tmin scaled      0.401
PLAT794_ALERT_5_G Check Predicted Bond Valency for Cu1         (2)       2.22

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

The design and synthesis of metal–organic framework structures have received enormous attention (Lehn, 1995) in recent years. It is well known that carboxylate ligands play an important role in coordination chemistry and can adopt various binding modes such as terminal monodentate, chelating to one metal center, bridging bidentate in a syn–syn, syn–anti, and anti–anti configuration to two metal centers, and bridging tridentate to two metal centers (Policar et al., 1999; Levstein & Calvo, 1990; Rueff et al., 2001). The use of organic spacers, particularly the flexible dicarboxylates bridging ligands and rigid planar bidentate diimines (bipy or pyz) as building blocks to construct various metal assemblage is of growing interest in the field of molecular materials (Oschio & Nagashima, 1990). Recently great success has been achieved by combination of the flexible aliphatic dicarboxylates and bipy as chelating bridging ligands, which resulted in compounds having 1–three-dimensional frameworks and unique physicochemical properties (Li et al., 1997, 2000; Rodriguez-Martin et al., 2001, 2002; Lightfoot & Snedden, 1999; Maji et al., 2003; Rather & Zaworotko, 2003; Zhang et al., 2003; Liu et al., 2003). In contrast to rigid spacers, the flexible ligands, which can adopt various conformations, may induce coordination polymers with novel topologies. However, the flexible ligands containing imidazolyl groups and polycarboxylate ligands have not been well studied to date (Yang et al., 2005; Ma et al., 2003, 2004; Wen et al., 2005, 2006, 2007). Bis(N-imidazolyl)methane (L1) can be used as flexible divergent ligands to construct coordination polymer materials. As an extension of our work (Jin & Chen, 2007a,b; Jin et al., 2007), the title complex is reported here.

The compound was obtained by reacting copper chloride dihydrate, oxalic acid, and bis(N-imidazolyl)methane (L1) in basic aqueous solution and it was isolated as blue crystals. (I) is a discrete dinuclear complex, and the asymmetric unit consists of one Cu ion, one oxalate, and one bis(N-imidazolyl)methane molecule. As shown in Fig. 1, Cu ion adopts square pyramidal geometry, and each copper atom is coordinated by two nitrogen atoms from two bis(N-imidazolyl)methane as bridging ligands, two oxygen atoms from one oxalate anion in chelating mode, one water molecule, completing its tretragonal pyramidal geometry in a N₂O₃ donor set. The Cu—N distances of 1.991 (2) and 1.977 (2) Å are normal and well consistent with those of known Cu–imidazole complexes ranging from 1.876 (13) to 2.049 (8) Å (Zhu et al., 2005). The Cu—O(water) bond distance, being 2.229 (2) Å is much longer than those of the Cu—O(carboxylate) bond distance [1.954 (2) Å]. The oxalate anion acts as a bis-unidentate ligand and forms a five-membered ring with the copper ion, while two L1 and two Cu atoms form a sixteen-membered ring. The dimeric units are connected through strong hydrogen bonds with water molecules, yielding three dimensional network structure, which is illustrated in Fig. 2.

Related literature

For related literature, see: Jin & Chen (2007a,b); Jin et al. (2007); Lehn (1995); Levstein & Calvo (1990); Li et al. (1997, 2000); Lightfoot & Snedden (1999); Liu et al. (2003); Ma et al. (2003, 2004); Maji et al. (2003); Nardelli (1999); Oschio & Nagashima (1990); Policar et al. (1999); Rather & Zaworotko (2003); Rodriguez-Martin et al. (2002, 2001); Rueff et al. (2001); Sheldrick (1996); Siemens (1996); Wen et al. (2005, 2006, 2007); Yang et al. (2005); Zhang et al. (2003); Zhu et al. (2005).

S2. Experimental

All reagents and solvents were used as obtained without further purification. The CHN elemental analyses were performed on a Perkin–Elmer elemental analyzer.

A mixture of copper chloride dihydrate (17.1 mg, 0.1 mmol), NaOH (8 mg, 0.2 mmol), and oxalic acid (12.7 mg, 0.1 mmol) in water (5 ml) was stirred for 15 min at 60 degree, then L1 (15 mg, 0.1 mmol) was added to the mixture. After stirring for 50 min, the blue precipitate was collected and dissolved in a minimum amount of ammonia. Blue single crystals of 1 were obtained by slow evaporation of the ammonia solution at ambient temperature. Yield: 30 mg, 44.7%. Anal. Calculated for C₁₈H₂₄Cu₂N₈O₁₂: C, 32.16; H, 3.57; N 16.68. Found: C, 31.96; H, 3.49; N 16.61.

S3. Refinement

All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H = 0.96 Å and O—H = 0.85 Å and U_iso set to 1.2 U_eq(parent atom). The coordinates of the water H atoms were calculated by the HYDROGEN program (Nardelli, 1999).

Computing details

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

Figures

	Fig. 1. The structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. Three dimensional network structure connected via hydrogen bonds.

bis[µ-bis(imidazol-1-yl)methane]bis[aqua(oxalato)copper(II)] dihydrate

Crystal data

[Cu2(C2O4)2(C7H8N4)2(H2O)2]·2H2O	Z = 1
Mr = 671.53	F(000) = 342
Triclinic, P1	Dx = 1.716 Mg m^−3
a = 7.970 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.770 (4) Å	Cell parameters from 2374 reflections
c = 9.913 (4) Å	θ = 2.4–28.0°
α = 117.964 (4)°	µ = 1.71 mm^−1
β = 104.582 (5)°	T = 298 K
γ = 91.773 (5)°	Block, blue
V = 649.7 (5) Å^3	0.55 × 0.53 × 0.49 mm

Data collection

Siemens SMART CCD area-detector diffractometer	2248 independent reflections
Radiation source: fine-focus sealed tube	1997 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
φ and ω scans	θmax = 25.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.453, Tmax = 0.487	k = −11→11
3367 measured reflections	l = −11→11

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)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.072	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0326P)^2 + 0.2553P] where P = (Fo^2 + 2Fc^2)/3
2248 reflections	(Δ/σ)max = 0.001
181 parameters	Δρmax = 0.37 e Å^−3
0 restraints	Δρmin = −0.36 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
Cu1	0.86641 (4)	0.71911 (3)	0.95989 (3)	0.02912 (12)
N1	0.7745 (3)	0.3018 (2)	0.5408 (2)	0.0287 (5)
N2	0.8596 (3)	0.5362 (2)	0.7528 (2)	0.0285 (5)
N3	0.5694 (3)	0.1755 (2)	0.2769 (2)	0.0276 (5)
N4	0.3642 (3)	0.2364 (2)	0.1309 (2)	0.0296 (5)
O1	1.1180 (2)	0.7196 (2)	1.0468 (2)	0.0360 (4)
O2	1.3453 (2)	0.8662 (2)	1.2644 (2)	0.0414 (5)
O3	0.9116 (2)	0.9180 (2)	1.1597 (2)	0.0450 (5)
O4	1.1263 (3)	1.0719 (3)	1.3829 (3)	0.0731 (8)
O5	0.7390 (3)	0.5676 (2)	1.0311 (2)	0.0476 (5)
H11	0.7729	0.4808	1.0134	0.071*
H12	0.7205	0.6120	1.1217	0.071*
O6	0.6384 (3)	0.7255 (3)	0.3125 (3)	0.0540 (6)
H13	0.5560	0.7690	0.2849	0.081*
H14	0.7054	0.8012	0.3997	0.081*
C1	0.6634 (4)	0.1548 (3)	0.4106 (3)	0.0338 (6)
H1A	0.7356	0.0746	0.3750	0.041*
H1B	0.5795	0.1197	0.4486	0.041*
C2	0.7277 (3)	0.4185 (3)	0.6587 (3)	0.0305 (6)
H2	0.6164	0.4162	0.6720	0.037*
C3	0.9981 (3)	0.4921 (3)	0.6917 (3)	0.0363 (6)
H3	1.1099	0.5524	0.7345	0.044*
C4	0.9473 (3)	0.3485 (3)	0.5607 (3)	0.0388 (7)
H4	1.0155	0.2923	0.4966	0.047*
C5	0.4070 (3)	0.2121 (3)	0.2547 (3)	0.0304 (6)
H5A	0.3350	0.2192	0.3176	0.036*
C6	0.5059 (3)	0.2145 (3)	0.0727 (3)	0.0337 (6)
H6	0.5134	0.2241	−0.0147	0.040*
C7	0.6329 (3)	0.1769 (3)	0.1621 (3)	0.0329 (6)
H7	0.7422	0.1561	0.1481	0.040*
C8	1.1908 (3)	0.8376 (3)	1.1850 (3)	0.0282 (5)
C9	1.0674 (3)	0.9537 (3)	1.2509 (3)	0.0376 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.02589 (18)	0.02280 (18)	0.02358 (18)	0.00912 (12)	0.00161 (12)	0.00222 (13)
N1	0.0313 (11)	0.0211 (10)	0.0221 (11)	0.0085 (9)	0.0015 (9)	0.0044 (9)
N2	0.0268 (10)	0.0248 (11)	0.0233 (11)	0.0069 (9)	0.0035 (9)	0.0053 (9)
N3	0.0298 (11)	0.0194 (10)	0.0231 (11)	0.0072 (8)	0.0017 (9)	0.0052 (8)
N4	0.0274 (10)	0.0269 (11)	0.0254 (11)	0.0068 (9)	0.0029 (9)	0.0083 (9)
O1	0.0299 (9)	0.0274 (10)	0.0279 (10)	0.0134 (8)	0.0017 (8)	−0.0011 (8)
O2	0.0283 (10)	0.0393 (11)	0.0388 (11)	0.0068 (8)	−0.0026 (8)	0.0115 (9)
O3	0.0334 (10)	0.0353 (11)	0.0360 (11)	0.0169 (8)	0.0021 (9)	−0.0027 (9)
O4	0.0508 (13)	0.0559 (14)	0.0430 (13)	0.0166 (11)	0.0006 (11)	−0.0239 (11)
O5	0.0670 (13)	0.0411 (11)	0.0494 (12)	0.0287 (10)	0.0295 (11)	0.0269 (10)
O6	0.0396 (11)	0.0561 (14)	0.0495 (13)	0.0163 (10)	0.0099 (10)	0.0142 (11)
C1	0.0451 (15)	0.0194 (12)	0.0249 (13)	0.0063 (11)	0.0005 (11)	0.0065 (11)
C2	0.0291 (13)	0.0274 (13)	0.0257 (13)	0.0063 (11)	0.0065 (11)	0.0067 (11)
C3	0.0276 (13)	0.0396 (16)	0.0280 (14)	0.0039 (11)	0.0053 (11)	0.0076 (12)
C4	0.0318 (14)	0.0427 (16)	0.0285 (14)	0.0147 (12)	0.0102 (11)	0.0061 (12)
C5	0.0283 (13)	0.0287 (14)	0.0271 (13)	0.0072 (11)	0.0075 (11)	0.0086 (11)
C6	0.0337 (14)	0.0369 (15)	0.0280 (14)	0.0102 (11)	0.0086 (11)	0.0141 (12)
C7	0.0283 (13)	0.0317 (14)	0.0298 (14)	0.0099 (11)	0.0073 (11)	0.0085 (11)
C8	0.0266 (13)	0.0239 (13)	0.0273 (13)	0.0052 (10)	0.0043 (11)	0.0092 (11)
C9	0.0362 (15)	0.0269 (14)	0.0312 (15)	0.0074 (11)	0.0068 (12)	0.0014 (12)

Geometric parameters (Å, º)

Cu1—O3	1.9537 (19)	O3—C9	1.262 (3)
Cu1—O1	1.9717 (19)	O4—C9	1.227 (3)
Cu1—N2	1.977 (2)	O5—H11	0.8499
Cu1—N4^i	1.991 (2)	O5—H12	0.8499
Cu1—O5	2.229 (2)	O6—H13	0.8500
N1—C2	1.342 (3)	O6—H14	0.8500
N1—C4	1.373 (3)	C1—H1A	0.9700
N1—C1	1.456 (3)	C1—H1B	0.9700
N2—C2	1.313 (3)	C2—H2	0.9300
N2—C3	1.376 (3)	C3—C4	1.345 (4)
N3—C5	1.345 (3)	C3—H3	0.9300
N3—C7	1.362 (3)	C4—H4	0.9300
N3—C1	1.456 (3)	C5—H5A	0.9300
N4—C5	1.322 (3)	C6—C7	1.350 (4)
N4—C6	1.372 (3)	C6—H6	0.9300
N4—Cu1^i	1.991 (2)	C7—H7	0.9300
O1—C8	1.273 (3)	C8—C9	1.542 (4)
O2—C8	1.224 (3)
O3—Cu1—O1	83.29 (7)	N3—C1—H1A	109.5
O3—Cu1—N2	169.00 (9)	N1—C1—H1A	109.5
O1—Cu1—N2	90.02 (8)	N3—C1—H1B	109.5
O3—Cu1—N4^i	91.17 (8)	N1—C1—H1B	109.5
O1—Cu1—N4^i	165.88 (8)	H1A—C1—H1B	108.1
N2—Cu1—N4^i	93.33 (8)	N2—C2—N1	111.1 (2)
O3—Cu1—O5	97.83 (9)	N2—C2—H2	124.4
O1—Cu1—O5	101.59 (8)	N1—C2—H2	124.4
N2—Cu1—O5	92.04 (9)	C4—C3—N2	109.8 (2)
N4^i—Cu1—O5	92.01 (9)	C4—C3—H3	125.1
C2—N1—C4	107.3 (2)	N2—C3—H3	125.1
C2—N1—C1	127.3 (2)	C3—C4—N1	106.0 (2)
C4—N1—C1	125.3 (2)	C3—C4—H4	127.0
C2—N2—C3	105.8 (2)	N1—C4—H4	127.0
C2—N2—Cu1	125.91 (17)	N4—C5—N3	110.4 (2)
C3—N2—Cu1	127.46 (17)	N4—C5—H5A	124.8
C5—N3—C7	107.7 (2)	N3—C5—H5A	124.8
C5—N3—C1	124.9 (2)	C7—C6—N4	109.4 (2)
C7—N3—C1	127.2 (2)	C7—C6—H6	125.3
C5—N4—C6	106.1 (2)	N4—C6—H6	125.3
C5—N4—Cu1^i	126.32 (17)	C6—C7—N3	106.4 (2)
C6—N4—Cu1^i	127.45 (18)	C6—C7—H7	126.8
C8—O1—Cu1	113.30 (15)	N3—C7—H7	126.8
C9—O3—Cu1	113.63 (16)	O2—C8—O1	126.3 (2)
Cu1—O5—H11	118.7	O2—C8—C9	119.4 (2)
Cu1—O5—H12	117.8	O1—C8—C9	114.3 (2)
H11—O5—H12	110.1	O4—C9—O3	125.5 (3)
H13—O6—H14	103.0	O4—C9—C8	119.0 (2)
N3—C1—N1	110.6 (2)	O3—C9—C8	115.4 (2)
O3—Cu1—N2—C2	−164.4 (4)	C1—N1—C2—N2	−177.8 (2)
O1—Cu1—N2—C2	143.2 (2)	C2—N2—C3—C4	0.4 (3)
N4^i—Cu1—N2—C2	−50.5 (2)	Cu1—N2—C3—C4	170.18 (19)
O5—Cu1—N2—C2	41.6 (2)	N2—C3—C4—N1	−0.6 (3)
O3—Cu1—N2—C3	27.7 (5)	C2—N1—C4—C3	0.5 (3)
O1—Cu1—N2—C3	−24.6 (2)	C1—N1—C4—C3	178.1 (2)
N4^i—Cu1—N2—C3	141.7 (2)	C6—N4—C5—N3	−0.1 (3)
O5—Cu1—N2—C3	−126.2 (2)	Cu1^i—N4—C5—N3	176.06 (15)
O3—Cu1—O1—C8	1.64 (18)	C7—N3—C5—N4	0.1 (3)
N2—Cu1—O1—C8	172.90 (18)	C1—N3—C5—N4	174.5 (2)
N4^i—Cu1—O1—C8	69.1 (4)	C5—N4—C6—C7	0.1 (3)
O5—Cu1—O1—C8	−95.02 (19)	Cu1^i—N4—C6—C7	−176.04 (17)
O1—Cu1—O3—C9	−2.0 (2)	N4—C6—C7—N3	0.0 (3)
N2—Cu1—O3—C9	−54.8 (5)	C5—N3—C7—C6	0.0 (3)
N4^i—Cu1—O3—C9	−169.0 (2)	C1—N3—C7—C6	−174.2 (2)
O5—Cu1—O3—C9	98.9 (2)	Cu1—O1—C8—O2	−179.4 (2)
C5—N3—C1—N1	−92.8 (3)	Cu1—O1—C8—C9	−1.1 (3)
C7—N3—C1—N1	80.5 (3)	Cu1—O3—C9—O4	−179.4 (3)
C2—N1—C1—N3	86.0 (3)	Cu1—O3—C9—C8	1.9 (3)
C4—N1—C1—N3	−91.2 (3)	O2—C8—C9—O4	−0.9 (4)
C3—N2—C2—N1	−0.1 (3)	O1—C8—C9—O4	−179.3 (3)
Cu1—N2—C2—N1	−170.06 (16)	O2—C8—C9—O3	177.9 (2)
C4—N1—C2—N2	−0.3 (3)	O1—C8—C9—O3	−0.6 (4)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H14···O4^ii	0.85	1.98	2.804 (3)	164
O6—H13···O2^iii	0.85	1.97	2.797 (3)	165
O5—H12···O6^iv	0.85	1.98	2.823 (3)	169
O5—H11···O1^v	0.85	2.05	2.895 (3)	170

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