Acta Cryst. (2009). E65, m1511 [ doi:10.1107/S1600536809045371 ]
![[kappa]](/logos/entities/kappa_rmgif.gif)
2N1,O)copper(II)The title compound, [Cu(C5H3N2O2)2(H2O)2], is a new polymorph of the previously reported compound [Klein et al. (1982). Inorg. Chem. 21, 1891-1897]. The CuII atom, lying on an inversion center, is coordinated by two N atoms and two O atoms from two pyrazine-2-carboxylate ligands and by two water molecules in a distorted octahedral geometry with the water molecules occupying the axial sites. Intermolecular O-H
O, O-HN and C-HO hydrogen bonds connect the complex molecules into a two-dimensional layer parallel to (10
), whereas the previously reported polymorph exhibits a three-dimensional hydrogen-bonded network.
Aqueous triethylamine (0.05 ml) was added to a suspending solution of Hpzc (0.012 g, 0.1 mmol) in H2O (7 ml), followed by dropwise addition of a solution of Cu(NO3)2.3H2O (0.024 g, 0.1 mmol) in H2O (3 ml). The mixture was stirred and sealed in a 15 ml Teflon-lined stainless steel autoclave and heated at 413 K for 3 d under autogenous pressure. When the mixture was cooled to room temperature, blue block crystals of the title compound were obtained (yield 0.029 g, 85% based on Cu).
H atoms of the pyrazine ring were positioned geometrically and refined as riding atoms, with C—H = 0.93 Å and with Uiso(H) = 1.2Ueq(C). H atoms of the water molecule were located in a difference Fourier map and refined as riding, with O—H = 0.82 Å and with Uiso(H) = 1.2Ueq(O).
Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
![[Figure 1]](./is2480fig1thm.gif)
| Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry code: (i) -x, 1 - y, 2 - z.] |
![[Figure 2]](./is2480fig2thm.gif)
| Fig. 2. A part of the two-dimensional layer structure in the title compound. Dashed lines denote hydrogen bonds. |
| [Cu(C5H3N2O2)2(H2O)2] | F(000) = 350 |
| Mr = 345.76 | Dx = 1.864 Mg m−3 |
| Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2yn | Cell parameters from 2148 reflections |
| a = 6.7066 (12) Å | θ = 3.1–26.1° |
| b = 7.9041 (14) Å | µ = 1.81 mm−1 |
| c = 12.030 (2) Å | T = 293 K |
| β = 105.036 (2)° | Block, blue |
| V = 615.88 (19) Å3 | 0.29 × 0.25 × 0.20 mm |
| Z = 2 |
| Bruker SMART APEX CCD diffractometer | 1212 independent reflections |
| Radiation source: sealed tube | 1119 reflections with I > 2σ(I) |
| graphite | Rint = 0.014 |
| φ and ω scans | θmax = 26.1°, θmin = 3.1° |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→8 |
| Tmin = 0.626, Tmax = 0.711 | k = −8→9 |
| 3322 measured reflections | l = −7→14 |
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
| R[F2 > 2σ(F2)] = 0.024 | H-atom parameters constrained |
| wR(F2) = 0.071 | w = 1/[σ2(Fo2) + (0.0427P)2 + 0.1736P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.10 | (Δ/σ)max < 0.001 |
| 1212 reflections | Δρmax = 0.24 e Å−3 |
| 98 parameters | Δρmin = −0.27 e Å−3 |
| 0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.015 (3) |
| [Cu(C5H3N2O2)2(H2O)2] | V = 615.88 (19) Å3 |
| Mr = 345.76 | Z = 2 |
| Monoclinic, P21/n | Mo Kα radiation |
| a = 6.7066 (12) Å | µ = 1.81 mm−1 |
| b = 7.9041 (14) Å | T = 293 K |
| c = 12.030 (2) Å | 0.29 × 0.25 × 0.20 mm |
| β = 105.036 (2)° |
| Bruker SMART APEX CCD diffractometer | 1212 independent reflections |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1119 reflections with I > 2σ(I) |
| Tmin = 0.626, Tmax = 0.711 | Rint = 0.014 |
| 3322 measured reflections | θmax = 26.1° |
| R[F2 > 2σ(F2)] = 0.024 | H-atom parameters constrained |
| wR(F2) = 0.071 | Δρmax = 0.24 e Å−3 |
| S = 1.10 | Δρmin = −0.27 e Å−3 |
| 1212 reflections | Absolute structure: ? |
| 98 parameters | Flack parameter: ? |
| 0 restraints | Rogers parameter: ? |
| x | y | z | Uiso*/Ueq | ||
| Cu1 | 0.0000 | 0.5000 | 1.0000 | 0.03498 (16) | |
| O1 | −0.0727 (2) | 0.61455 (15) | 0.85150 (10) | 0.0366 (3) | |
| O2 | −0.1196 (2) | 0.56084 (18) | 0.66400 (11) | 0.0410 (3) | |
| N1 | 0.0637 (2) | 0.30822 (17) | 0.90970 (11) | 0.0281 (3) | |
| N2 | 0.0994 (2) | 0.0660 (2) | 0.74999 (14) | 0.0379 (4) | |
| C1 | 0.1310 (3) | 0.1525 (2) | 0.94293 (15) | 0.0323 (4) | |
| H1 | 0.1685 | 0.1252 | 1.0208 | 0.039* | |
| C2 | 0.1451 (3) | 0.0321 (2) | 0.86246 (19) | 0.0388 (4) | |
| H2 | 0.1880 | −0.0765 | 0.8874 | 0.047* | |
| C3 | 0.0352 (3) | 0.2226 (2) | 0.71834 (15) | 0.0334 (4) | |
| H3 | 0.0033 | 0.2509 | 0.6407 | 0.040* | |
| C4 | 0.0146 (2) | 0.3439 (2) | 0.79692 (14) | 0.0277 (4) | |
| C5 | −0.0665 (3) | 0.5207 (2) | 0.76592 (16) | 0.0299 (4) | |
| O1W | 0.3669 (2) | 0.63676 (18) | 1.04173 (12) | 0.0483 (4) | |
| H1A | 0.3551 | 0.7207 | 1.0796 | 0.058* | |
| H1B | 0.4636 | 0.5788 | 1.0781 | 0.058* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Cu1 | 0.0529 (2) | 0.0279 (2) | 0.0235 (2) | 0.00894 (12) | 0.00891 (15) | −0.00016 (10) |
| O1 | 0.0516 (8) | 0.0285 (6) | 0.0285 (7) | 0.0070 (5) | 0.0085 (5) | 0.0008 (5) |
| O2 | 0.0550 (8) | 0.0383 (7) | 0.0252 (7) | 0.0039 (6) | 0.0022 (6) | 0.0042 (6) |
| N1 | 0.0298 (7) | 0.0275 (7) | 0.0256 (7) | 0.0002 (5) | 0.0050 (5) | 0.0003 (6) |
| N2 | 0.0438 (9) | 0.0331 (8) | 0.0380 (9) | 0.0012 (7) | 0.0127 (7) | −0.0059 (7) |
| C1 | 0.0343 (9) | 0.0327 (9) | 0.0287 (9) | 0.0030 (7) | 0.0059 (7) | 0.0043 (7) |
| C2 | 0.0417 (10) | 0.0292 (9) | 0.0468 (12) | 0.0066 (7) | 0.0139 (9) | 0.0022 (8) |
| C3 | 0.0356 (9) | 0.0352 (9) | 0.0287 (9) | −0.0023 (7) | 0.0073 (7) | −0.0023 (7) |
| C4 | 0.0271 (8) | 0.0292 (8) | 0.0258 (8) | −0.0022 (6) | 0.0049 (6) | −0.0005 (6) |
| C5 | 0.0299 (8) | 0.0287 (8) | 0.0292 (10) | −0.0006 (6) | 0.0039 (7) | 0.0010 (7) |
| O1W | 0.0578 (9) | 0.0406 (8) | 0.0456 (8) | 0.0054 (6) | 0.0116 (7) | −0.0037 (6) |
| Cu1—O1 | 1.9486 (12) | C1—C2 | 1.378 (3) |
| Cu1—N1 | 1.9753 (14) | C1—H1 | 0.9300 |
| Cu1—O1W | 2.6143 (14) | C2—H2 | 0.9300 |
| O1—C5 | 1.279 (2) | C3—C4 | 1.379 (2) |
| O2—C5 | 1.227 (2) | C3—H3 | 0.9300 |
| N1—C1 | 1.336 (2) | C4—C5 | 1.510 (2) |
| N1—C4 | 1.340 (2) | O1W—H1A | 0.82 |
| N2—C3 | 1.333 (3) | O1W—H1B | 0.82 |
| N2—C2 | 1.335 (3) | ||
| O1i—Cu1—O1 | 180.0 | N1—C1—H1 | 119.8 |
| O1i—Cu1—N1i | 83.73 (5) | C2—C1—H1 | 119.8 |
| O1—Cu1—N1i | 96.27 (5) | N2—C2—C1 | 122.29 (18) |
| O1i—Cu1—N1 | 96.27 (5) | N2—C2—H2 | 118.9 |
| O1—Cu1—N1 | 83.73 (5) | C1—C2—H2 | 118.9 |
| N1i—Cu1—N1 | 180.0 | N2—C3—C4 | 122.17 (16) |
| O1W—Cu1—N1 | 95.50 (5) | N2—C3—H3 | 118.9 |
| O1W—Cu1—O1 | 89.03 (5) | C4—C3—H3 | 118.9 |
| O1W—Cu1—N1i | 84.50 (5) | N1—C4—C3 | 120.37 (16) |
| O1W—Cu1—O1i | 90.97 (5) | N1—C4—C5 | 115.01 (15) |
| C5—O1—Cu1 | 114.57 (11) | C3—C4—C5 | 124.60 (16) |
| C1—N1—C4 | 118.16 (14) | O2—C5—O1 | 126.37 (16) |
| C1—N1—Cu1 | 130.31 (12) | O2—C5—C4 | 118.61 (16) |
| C4—N1—Cu1 | 111.33 (11) | O1—C5—C4 | 115.02 (15) |
| C3—N2—C2 | 116.61 (16) | H1A—O1W—H1B | 109 |
| N1—C1—C2 | 120.36 (16) |
| Symmetry codes: (i) −x, −y+1, −z+2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O1W—H1A···O2ii | 0.82 | 1.99 | 2.796 (2) | 168 |
| O1W—H1B···N2iii | 0.82 | 2.33 | 3.041 (2) | 145 |
| C1—H1···O2iii | 0.93 | 2.42 | 3.226 (2) | 144 |
| Symmetry codes: (ii) x+1/2, −y+3/2, z+1/2; (iii) x+1/2, −y+1/2, z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O1W—H1A···O2i | 0.82 | 1.99 | 2.796 (2) | 168 |
| O1W—H1B···N2ii | 0.82 | 2.33 | 3.041 (2) | 145 |
| C1—H1···O2ii | 0.93 | 2.42 | 3.226 (2) | 144 |
| Symmetry codes: (i) x+1/2, −y+3/2, z+1/2; (ii) x+1/2, −y+1/2, z+1/2. |
The authors thank Changchun Institute of Applied Chemistry for supporting this work.
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Pyrazinecarboxylates have been extensively studied as excellent bridging ligands in the coordination chemistry research (Dong et al., 2000; Kubota et al., 2006; Luo et al., 2004; Ptasiewicz-Bak et al., 1995). The structure and magnetic properties of a copper(II) complex with the pyrazine-2-carboxylate (pzc) ligand (polymorph I) has been reported by Klein et al. (1982). We report here the structure of a new polymorph (polymorph II) of the title compound.
The polymorph II crystallizes in the monoclinic space group P21/n (polymorph I in P21/c). The CuII atom, lying on an inversion center, is six-coordinated in a distorted octahedral geometry, defined by two O atoms and two N atoms from two pzc ligands in the equatorial plane and two water molecules in the axial positions (Table 1 and Fig. 1). Weak coordination exists between the CuII center and the coordinated water molecule, with a Cu—O distance of 2.6143 (14) Å, due to Jahn-Teller effects. The bond lengths and angles are in normal ranges (Chutia et al., 2009; Klein et al., 1982). The coordinated water molecule donates its two H atoms to an uncoordinated carboxylate O atom and a pyrazine N atom of the neighboring molecules (Table 2 and Fig. 2). One complex molecule is linked to four neighboring molecules through these O—H···O and O—H···N hydrogen bonds, forming a two-dimensional layer in the (1 0 1) plane. Weak C—H···O hydrogen bond (Table 2) stabilizes the layer structure. In the previously reported polymorph I, the water molecule forms two O—H···O hydrogen bonds with a coordinated carboxylate O atom and an uncoordinated carboxylate O atom. One complex molecule is linked to six neighboring molecules, leading to a three-dimensional network.