The title complex, trans-{μ-2,2′-[(1,2-dioxoethane-1,2-diyl)diimino]diethanoato(4−)}bis[diaquacopper(II)] dihydrate, [Cu2(C6H4N2O6)(H2O)4]·2H2O, with a three-dimensional framework, displays a square-pyramidal coordination geometry. The structure consists of a neutral centrosymmetric binuclear unit in which the oxamide ligand has a trans geometry, is fully deprotonated and acts in a bis-tridentate fashion.
Supporting information
CCDC reference: 269995
All chemicals were of reagent grade and were used without further purification. The ligand oxamidobis(ethanoic acid), H4(obe), was synthesized by the reported method (Yu et al., 1991). The complex was prepared by the following procedure. A solution of copper(II) chloride dihydrate (68.2 mg, 0.4 mmol) dissolved in methanol (5 ml) was added dropwise to a water/methanol (20 ml, 1:5, v/v) mixture containing the ligand (0.2 mmol). An appropriate amount of piperidine was then added to adjust the pH to 7. The mixture was heated at reflux with stirring for 12 h. The precipitate was filtered off, washed with cold water, methanol and diethyl ether in turn, and then redissolved in water. Green crystals (yield 49.6 mg, 57%) were obtained from the solution after 5 d by slow evaporation at room temperature. Analysis calculated: C 16.55, H 3.70, N 6.44%; found: C 16.48, H 3.62, N 6.37%. IR (KBr pellet, cm−1): ν(O—H) 3157 (s, br), νa(COO−) 1661 (vs), ν(N—C═O) 1585 (vs), νas(COO−) 1384 (s).
H atoms attached to C atoms were positioned geometrically and were treated as riding on their parent C atoms, with C—H distances of 0.97 Å and Uiso(H) = 1.2Ueq(C). Water H atoms were located in a difference Fouier map and were included in the structure-factor calculation with fixed positional and isotropic displacement parameters [O—H = 0.83–0.90 Å; Uiso(H) = 0.08 Å2].
Data collection: SMART (Bruker, 2000); cell refinement: SMART [or SAINT?] (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); 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).
trans-{µ-2,2'-[(1,2-dioxoethane-1,2- diyl)diimino]diethanoato}bis[diaquacopper(II)] dihydrate
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Crystal data top
[Cu2(C6H4N2O6)(H2O)4]·2H2O | Z = 1 |
Mr = 435.31 | F(000) = 220 |
Triclinic, P1 | Dx = 2.064 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.870 (6) Å | Cell parameters from 1696 reflections |
b = 7.283 (7) Å | θ = 2.7–27.6° |
c = 7.929 (7) Å | µ = 3.10 mm−1 |
α = 73.693 (14)° | T = 293 K |
β = 87.795 (14)° | Block, green |
γ = 67.342 (14)° | 0.19 × 0.15 × 0.12 mm |
V = 350.3 (6) Å3 | |
Data collection top
Bruker APEX area-detector diffractometer | 1541 independent reflections |
Radiation source: fine-focus sealed tube | 1431 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.021 |
ϕ and ω scans | θmax = 27.0°, θmin = 2.7° |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | h = −5→8 |
Tmin = 0.578, Tmax = 0.689 | k = −7→9 |
2108 measured reflections | l = −9→10 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.026 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.071 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0378P)2 + 0.2235P] where P = (Fo2 + 2Fc2)/3 |
1541 reflections | (Δ/σ)max = 0.001 |
100 parameters | Δρmax = 0.37 e Å−3 |
0 restraints | Δρmin = −0.67 e Å−3 |
Crystal data top
[Cu2(C6H4N2O6)(H2O)4]·2H2O | γ = 67.342 (14)° |
Mr = 435.31 | V = 350.3 (6) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.870 (6) Å | Mo Kα radiation |
b = 7.283 (7) Å | µ = 3.10 mm−1 |
c = 7.929 (7) Å | T = 293 K |
α = 73.693 (14)° | 0.19 × 0.15 × 0.12 mm |
β = 87.795 (14)° | |
Data collection top
Bruker APEX area-detector diffractometer | 1541 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | 1431 reflections with I > 2σ(I) |
Tmin = 0.578, Tmax = 0.689 | Rint = 0.021 |
2108 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.026 | 0 restraints |
wR(F2) = 0.071 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.37 e Å−3 |
1541 reflections | Δρmin = −0.67 e Å−3 |
100 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | |
Cu | 0.73780 (4) | 0.53068 (4) | 0.23673 (3) | 0.02237 (12) | |
N1 | 0.5643 (3) | 0.3828 (3) | 0.3331 (2) | 0.0211 (3) | |
O1 | 0.6915 (3) | 0.1363 (3) | −0.0072 (2) | 0.0354 (4) | |
O2 | 0.7700 (2) | 0.3790 (2) | 0.05608 (19) | 0.0245 (3) | |
O3 | 0.3581 (2) | 0.3369 (2) | 0.5671 (2) | 0.0249 (3) | |
O4 | 1.0407 (3) | 0.2828 (3) | 0.4064 (2) | 0.0341 (4) | |
H4A | 1.1313 | 0.3194 | 0.4430 | 0.080* | |
H4B | 1.1098 | 0.1724 | 0.3769 | 0.080* | |
O5 | 0.8686 (3) | 0.7155 (3) | 0.1139 (3) | 0.0448 (5) | |
H5A | 0.7987 | 0.8538 | 0.0747 | 0.080* | |
H5B | 0.9862 | 0.6955 | 0.0661 | 0.080* | |
O6 | 0.8870 (4) | 0.0693 (3) | 0.6909 (3) | 0.0485 (5) | |
H6A | 0.8721 | 0.1767 | 0.6101 | 0.080* | |
H6B | 0.8289 | 0.1020 | 0.7812 | 0.080* | |
C1 | 0.6828 (3) | 0.2479 (3) | 0.0875 (3) | 0.0220 (4) | |
C2 | 0.5565 (3) | 0.2321 (3) | 0.2499 (3) | 0.0229 (4) | |
H2A | 0.4111 | 0.2615 | 0.2157 | 0.027* | |
H2B | 0.6175 | 0.0932 | 0.3308 | 0.027* | |
C3 | 0.4756 (3) | 0.4182 (3) | 0.4734 (2) | 0.0196 (4) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cu | 0.02759 (17) | 0.02631 (18) | 0.02251 (16) | −0.01714 (12) | 0.01307 (10) | −0.01307 (11) |
N1 | 0.0244 (8) | 0.0259 (9) | 0.0209 (8) | −0.0150 (7) | 0.0091 (6) | −0.0121 (7) |
O1 | 0.0557 (11) | 0.0344 (9) | 0.0301 (8) | −0.0253 (8) | 0.0195 (8) | −0.0216 (7) |
O2 | 0.0296 (8) | 0.0260 (7) | 0.0235 (7) | −0.0142 (6) | 0.0123 (6) | −0.0122 (6) |
O3 | 0.0290 (8) | 0.0325 (8) | 0.0265 (7) | −0.0211 (6) | 0.0145 (6) | −0.0168 (6) |
O4 | 0.0290 (8) | 0.0378 (9) | 0.0419 (9) | −0.0150 (7) | 0.0017 (7) | −0.0183 (8) |
O5 | 0.0502 (11) | 0.0271 (9) | 0.0649 (13) | −0.0236 (8) | 0.0396 (10) | −0.0177 (8) |
O6 | 0.0663 (13) | 0.0440 (11) | 0.0344 (9) | −0.0193 (10) | 0.0200 (9) | −0.0156 (8) |
C1 | 0.0255 (9) | 0.0224 (9) | 0.0190 (9) | −0.0086 (8) | 0.0058 (7) | −0.0087 (7) |
C2 | 0.0285 (10) | 0.0261 (10) | 0.0219 (9) | −0.0157 (8) | 0.0093 (8) | −0.0127 (8) |
C3 | 0.0202 (9) | 0.0223 (9) | 0.0203 (9) | −0.0105 (7) | 0.0043 (7) | −0.0094 (7) |
Geometric parameters (Å, º) top
Cu—N1 | 1.903 (2) | O4—H4A | 0.8531 |
Cu—O2 | 1.999 (2) | O4—H4B | 0.8539 |
Cu—O3i | 2.015 (2) | O5—H5A | 0.897 |
Cu—O4 | 2.314 (2) | O5—H5B | 0.8568 |
Cu—O5 | 1.922 (2) | O6—H6A | 0.833 |
N1—C2 | 1.448 (3) | O6—H6B | 0.8541 |
N1—C3 | 1.289 (3) | C1—C2 | 1.527 (3) |
O1—C1 | 1.237 (3) | C2—H2A | 0.9700 |
O2—C1 | 1.276 (3) | C2—H2B | 0.9700 |
O3—C3 | 1.277 (3) | C3—C3i | 1.521 (4) |
O3—Cui | 2.015 (2) | | |
| | | |
N1—Cu—O2 | 82.22 (8) | H4A—O4—H4B | 107.08 |
N1—Cu—O3i | 83.85 (8) | Cu—O5—H5A | 123.07 |
N1—Cu—O4 | 94.39 (10) | Cu—O5—H5B | 132.88 |
N1—Cu—O5 | 169.86 (9) | H5A—O5—H5B | 103.02 |
O2—Cu—O3i | 165.42 (7) | H6A—O6—H6B | 109.7 |
O2—Cu—O4 | 93.80 (8) | O1—C1—O2 | 123.9 (2) |
O3i—Cu—O4 | 91.50 (9) | O1—C1—C2 | 118.4 (2) |
O5—Cu—O2 | 96.84 (10) | O2—C1—C2 | 117.69 (17) |
O5—Cu—O3i | 96.13 (9) | N1—C2—C1 | 107.46 (17) |
O5—Cu—O4 | 95.75 (11) | N1—C2—H2A | 110.2 |
C2—N1—Cu | 117.22 (14) | C1—C2—H2A | 110.2 |
C3—N1—Cu | 116.19 (14) | N1—C2—H2B | 110.2 |
C3—N1—C2 | 126.44 (18) | C1—C2—H2B | 110.2 |
C1—O2—Cu | 115.06 (13) | H2A—C2—H2B | 108.5 |
C3—O3—Cui | 109.13 (13) | O3—C3—N1 | 129.27 (18) |
Cu—O4—H4A | 120.22 | O3—C3—C3i | 118.8 (2) |
Cu—O4—H4B | 119.42 | N1—C3—C3i | 112.0 (2) |
| | | |
O5—Cu—N1—C3 | −93.3 (4) | Cu—O2—C1—O1 | −177.96 (18) |
O2—Cu—N1—C3 | −178.61 (17) | Cu—O2—C1—C2 | 3.4 (2) |
O3i—Cu—N1—C3 | −2.89 (16) | C3—N1—C2—C1 | 179.6 (2) |
O4—Cu—N1—C3 | 88.15 (17) | Cu—N1—C2—C1 | −5.1 (2) |
O5—Cu—N1—C2 | 90.9 (4) | O1—C1—C2—N1 | −177.80 (19) |
O2—Cu—N1—C2 | 5.58 (15) | O2—C1—C2—N1 | 0.9 (3) |
O3i—Cu—N1—C2 | −178.70 (16) | Cui—O3—C3—N1 | −177.80 (19) |
O4—Cu—N1—C2 | −87.66 (16) | Cui—O3—C3—C3i | 2.0 (3) |
N1—Cu—O2—C1 | −4.95 (15) | C2—N1—C3—O3 | −2.3 (4) |
O5—Cu—O2—C1 | −174.78 (15) | Cu—N1—C3—O3 | −177.68 (18) |
O3i—Cu—O2—C1 | −22.1 (3) | C2—N1—C3—C3i | 177.8 (2) |
O4—Cu—O2—C1 | 88.97 (16) | Cu—N1—C3—C3i | 2.5 (3) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4A···O3ii | 0.8531 | 1.938 | 2.773 (3) | 166.13 |
O5—H5A···O1iii | 0.897 | 1.821 | 2.713 (4) | 172.33 |
O5—H5B···O2iv | 0.8568 | 1.873 | 2.721 (3) | 169.73 |
O6—H6B···O1v | 0.8541 | 1.923 | 2.770 (3) | 171.16 |
Symmetry codes: (ii) x+1, y, z; (iii) x, y+1, z; (iv) −x+2, −y+1, −z; (v) x, y, z+1. |
Experimental details
Crystal data |
Chemical formula | [Cu2(C6H4N2O6)(H2O)4]·2H2O |
Mr | 435.31 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.870 (6), 7.283 (7), 7.929 (7) |
α, β, γ (°) | 73.693 (14), 87.795 (14), 67.342 (14) |
V (Å3) | 350.3 (6) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 3.10 |
Crystal size (mm) | 0.19 × 0.15 × 0.12 |
|
Data collection |
Diffractometer | Bruker APEX area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2000) |
Tmin, Tmax | 0.578, 0.689 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2108, 1541, 1431 |
Rint | 0.021 |
(sin θ/λ)max (Å−1) | 0.640 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.026, 0.071, 1.06 |
No. of reflections | 1541 |
No. of parameters | 100 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.37, −0.67 |
Selected geometric parameters (Å, º) topCu—N1 | 1.903 (2) | Cu—O5 | 1.922 (2) |
Cu—O2 | 1.999 (2) | N1—C3 | 1.289 (3) |
Cu—O3i | 2.015 (2) | O3—C3 | 1.277 (3) |
Cu—O4 | 2.314 (2) | | |
| | | |
N1—Cu—O2 | 82.22 (8) | O2—Cu—O4 | 93.80 (8) |
N1—Cu—O3i | 83.85 (8) | O3i—Cu—O4 | 91.50 (9) |
N1—Cu—O4 | 94.39 (10) | O5—Cu—O2 | 96.84 (10) |
N1—Cu—O5 | 169.86 (9) | O5—Cu—O3i | 96.13 (9) |
O2—Cu—O3i | 165.42 (7) | O5—Cu—O4 | 95.75 (11) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4A···O3ii | 0.8531 | 1.938 | 2.773 (3) | 166.13 |
O5—H5A···O1iii | 0.897 | 1.821 | 2.713 (4) | 172.33 |
O5—H5B···O2iv | 0.8568 | 1.873 | 2.721 (3) | 169.73 |
O6—H6B···O1v | 0.8541 | 1.923 | 2.770 (3) | 171.16 |
Symmetry codes: (ii) x+1, y, z; (iii) x, y+1, z; (iv) −x+2, −y+1, −z; (v) x, y, z+1. |
Many research efforts have been dedicated to studying oxamide-bridged transition metal complexes because of their expected magnetic properties and biological relevance (Santana et al., 2004; Messori et al., 2003; Kou et al., 2003). One of the most outstanding characteristics of oxamide ligands is their versatile bonding mode with metal ions, which makes it practical to design tunable molecular materials with extended structures (Li et al., 1998; Lloret, Julve et al., 1992 or Lloret, Sletten et al., 1992?). Taking into account the above facts and in continuation of our work on polynuclear complexes with bridging oxamide groups (Li et al., 2003), in this paper, we describe the synthesis of a new binuclear copper(II) complex, [Cu2(obe)(H2O)4]·2H2O, (I), using oxamidobis(ethanoate) {obe; 2,2'-[(1,2-dioxoethane-1,2-diyl)diimino]diethanoate} as bridging ligand. The crystal structure of (I) was determined in order to examine the effect of pH upon the bonding mode of the obe ligand with copper(II).
The molecular structure of (I) is illustrated in Fig. 1. Single-crystal X-ray analysis reveals that the complex contains a neutral centrosymmetric binuclear molecule in which the oxamide ligand has a trans geometry, is fully deprotonated and acts in a bis-tridentate fashion. The Cu atom has a square-pyramidal coordination geometry, with three atoms (N1, O2 and O3) from the oxamide ligand and one water molecule (O5) in the basal plane, and with one water molecule (O4) in the apical position. The deviations of atoms N1, O2, O3 and O5 from the least-squares plane through these atoms are 0.0408 (10), 0.0365 (9), 0.0358 (8) and 0.0315 (7))Å, respectively, while the Cu atom is displaced 0.1322 (9) Å from this plane. The Cu—O distance of 2.314 (2) Å in the axial direction is longer than those in the basal plane by 0.315, 0.299, and 0.392 Å (Table 1). The Cu···Cu separation within each binuclear unit is 5.228 (4) Å.
As shown in Fig. 2, a two-dimensional network paralleling the crystal plane (1, 0, 1) is formed via hydrogen bonding between the coordinated water molecule (O5) in the basal plane and atoms O1 and O2 from the carboxylate group (the hydrogen bonding geometries are listed in Table 2). Moreover, through hydrogen bonds between the other coordinated water molecule (O4), in the apical position, and atom O3 of the oxamide group, the two-dimensional hydrogen-bonding network is assembled into a three-dimensional supramolecular structure (Fig. 3), in which the uncoordinated water molecules participate by hydrogen bonding to atom O1(x, y, z + 1).
Compared with the previously reported complex {[Cu(H2obe)(H2O)3].4H2O}n (Lloret, Julve et al., 1992 or Lloret, Sletten et al., 1992?), which was obtained from aqueous solutions of copper(II) nitrate trihydrate and H4(obe) in a 1:1 molar ratio at a pH of ~3 by slow evaporation, the present complex has two important differences in the obe ligand. The previously reported complex consists of one-dimensional [Cu(H2obe)]n chains in which the ligand is deprotonated only at the terminal carboxylate groups and is bis-monodentate, and the N1—C3 and O3—C3 bond distances in the oxamide group are 1.326 (1) and 1.228 (1) Å. In the present complex, the ligand is fully deprotonated, not only at the carboxylate groups but also at the oxamide group. The deprotonation at atom N1 and copper coordination at atoms N1 and O3 lead to highly significant changes in the N1—C3 [1.289 (3) Å] and O3—C3 [1.277 (3) Å] bond distances, which indicate a more effective π delocalization in the NCO fragment.