Acta Cryst. (2008). E64, m458-m459 [ doi:10.1107/S1600536808003759 ]
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2O,O')zinc(II)The monomeric title ZnII complex, [Zn(C7H4BrO2)2(H2O)2], contains two 4-bromobenzoate (BB) ligands and two coordinated water molecules around a ZnII atom on a twofold rotation axis. The BB ions act as bidentate ligands, with two very dissimilar coordination distances. The sixfold coordination around the ZnII may be described as highly distorted octahedral, with the two aqua ligands arranged cis. Hydrogen bonding involving the carboxylate O atoms has an effect on the delocalization in the carboxylate groups. In the crystal structure, intermolecular O-H
O hydrogen bonds link the molecules into chains parallel to the c axis and stacked along the b axis.
The title compound, (I), was prepared by the reaction of ZnSO4 (1.61 g, 10 mmol) in H2O (100 ml) and p-bromobenzoate (4.00 g, 20 mmol) in H2O (100 ml). The mixture was filtered and set aside to crystallize at ambient temperature for several days, giving colorless single crystals.
H atoms of water molecules were located in difference syntheses and refined isotropically with restrains [O—H = 0.97 (7) and 0.95 (8) Å; Uiso(H) = 0.09 (4) and 0.09 (4) Å2]. The remaining H atoms were positioned geometrically with C—H = 0.93 Å, for aromatic H atoms and constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C).
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
![[Figure 1]](./bg2161fig1thm.gif)
| Fig. 1. A drawing of the title molecule with the atom-numbering scheme. The displacement ellipsoids are drawn at the 50% probability level [symmetry code: (i) 2 - x, y, 1/2 - z]. |
| [Zn(C7H4BrO2)2(H2O)2] | F000 = 976 |
| Mr = 501.43 | Dx = 2.099 Mg m−3 |
| Monoclinic, C2/c | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -C 2yc | Cell parameters from 25 reflections |
| a = 26.9067 (3) Å | θ = 6.7–10.8º |
| b = 5.0704 (4) Å | µ = 6.61 mm−1 |
| c = 12.0371 (5) Å | T = 294 (2) K |
| β = 104.95 (2)º | Block, colourless |
| V = 1586.6 (2) Å3 | 0.25 × 0.20 × 0.15 mm |
| Z = 4 |
| Enraf–Nonius TurboCAD-4 diffractometer | Rint = 0.031 |
| Radiation source: fine-focus sealed tube | θmax = 26.3º |
| Monochromator: graphite | θmin = 3.1º |
| T = 294(2) K | h = −33→0 |
| non–profiled ω scans | k = −6→0 |
| Absorption correction: ψ scan (North et al., 1968) | l = −14→15 |
| Tmin = 0.214, Tmax = 0.370 | 3 standard reflections |
| 1648 measured reflections | every 120 min |
| 1613 independent reflections | intensity decay: 1% |
| 1133 reflections with I > 2σ(I) |
| 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)] = 0.063 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.166 | w = 1/[σ2(Fo2) + (0.1112P)2] where P = (Fo2 + 2Fc2)/3 |
| S = 1.04 | (Δ/σ)max < 0.001 |
| 1613 reflections | Δρmax = 1.42 e Å−3 |
| 113 parameters | Δρmin = −1.83 e Å−3 |
| 4 restraints | Extinction correction: none |
| Primary atom site location: structure-invariant direct methods |
| [Zn(C7H4BrO2)2(H2O)2] | V = 1586.6 (2) Å3 |
| Mr = 501.43 | Z = 4 |
| Monoclinic, C2/c | Mo Kα |
| a = 26.9067 (3) Å | µ = 6.61 mm−1 |
| b = 5.0704 (4) Å | T = 294 (2) K |
| c = 12.0371 (5) Å | 0.25 × 0.20 × 0.15 mm |
| β = 104.95 (2)º |
| Enraf–Nonius TurboCAD-4 diffractometer | 1133 reflections with I > 2σ(I) |
| Absorption correction: ψ scan (North et al., 1968) | Rint = 0.031 |
| Tmin = 0.214, Tmax = 0.370 | 3 standard reflections |
| 1648 measured reflections | every 120 min |
| 1613 independent reflections | intensity decay: 1% |
| R[F2 > 2σ(F2)] = 0.063 | 4 restraints |
| wR(F2) = 0.166 | H atoms treated by a mixture of independent and constrained refinement |
| S = 1.04 | Δρmax = 1.42 e Å−3 |
| 1613 reflections | Δρmin = −1.83 e Å−3 |
| 113 parameters |
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. |
| x | y | z | Uiso*/Ueq | ||
| Br | 1.22102 (3) | 1.19239 (18) | 0.64660 (7) | 0.0502 (4) | |
| Zn | 1.0000 | 0.0782 (2) | 0.2500 | 0.0335 (4) | |
| O1 | 1.0587 (2) | 0.3361 (10) | 0.2873 (4) | 0.0342 (12) | |
| O2 | 1.0366 (2) | 0.2503 (10) | 0.4458 (4) | 0.0379 (12) | |
| O3 | 0.9709 (2) | −0.1998 (10) | 0.3320 (4) | 0.0404 (13) | |
| H31 | 0.960 (4) | −0.19 (2) | 0.403 (5) | 0.09 (4)* | |
| H32 | 0.953 (4) | −0.343 (15) | 0.289 (7) | 0.09 (4)* | |
| C1 | 1.0641 (3) | 0.3712 (14) | 0.3959 (6) | 0.0314 (16) | |
| C2 | 1.1029 (3) | 0.5711 (14) | 0.4540 (5) | 0.0292 (16) | |
| C3 | 1.0994 (3) | 0.6756 (16) | 0.5586 (6) | 0.0361 (17) | |
| H3 | 1.0732 | 0.6214 | 0.5909 | 0.043* | |
| C4 | 1.1352 (3) | 0.8615 (16) | 0.6150 (6) | 0.0404 (19) | |
| H4 | 1.1329 | 0.9337 | 0.6845 | 0.048* | |
| C5 | 1.1735 (3) | 0.9357 (14) | 0.5673 (6) | 0.0316 (16) | |
| C6 | 1.1776 (3) | 0.8399 (17) | 0.4632 (7) | 0.0415 (19) | |
| H6 | 1.2036 | 0.8983 | 0.4311 | 0.050* | |
| C7 | 1.1418 (3) | 0.6525 (17) | 0.4067 (6) | 0.0392 (18) | |
| H7 | 1.1442 | 0.5826 | 0.3369 | 0.047* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Br | 0.0509 (6) | 0.0389 (5) | 0.0485 (5) | −0.0172 (4) | −0.0093 (4) | 0.0011 (4) |
| Zn | 0.0403 (7) | 0.0166 (6) | 0.0429 (7) | 0.000 | 0.0097 (5) | 0.000 |
| O1 | 0.050 (3) | 0.028 (3) | 0.021 (2) | 0.001 (2) | 0.002 (2) | −0.006 (2) |
| O2 | 0.049 (3) | 0.030 (3) | 0.031 (3) | −0.014 (2) | 0.005 (2) | 0.000 (2) |
| O3 | 0.068 (4) | 0.023 (3) | 0.030 (3) | −0.009 (3) | 0.012 (3) | −0.004 (2) |
| C1 | 0.038 (4) | 0.026 (4) | 0.027 (3) | 0.005 (3) | 0.000 (3) | −0.001 (3) |
| C2 | 0.039 (4) | 0.019 (3) | 0.023 (3) | 0.001 (3) | −0.003 (3) | −0.003 (3) |
| C3 | 0.045 (4) | 0.041 (4) | 0.026 (3) | −0.012 (4) | 0.014 (3) | −0.008 (3) |
| C4 | 0.054 (5) | 0.035 (4) | 0.030 (4) | −0.011 (4) | 0.008 (3) | −0.009 (3) |
| C5 | 0.037 (4) | 0.024 (3) | 0.025 (3) | −0.006 (3) | −0.007 (3) | 0.003 (3) |
| C6 | 0.043 (4) | 0.043 (5) | 0.040 (4) | −0.007 (4) | 0.014 (4) | 0.002 (4) |
| C7 | 0.044 (4) | 0.050 (5) | 0.023 (3) | −0.006 (4) | 0.007 (3) | −0.009 (3) |
| Br—C5 | 1.901 (7) | C1—C2 | 1.494 (10) |
| Zn—O1 | 2.010 (5) | C2—C3 | 1.392 (10) |
| Zn—O1i | 2.010 (5) | C2—C7 | 1.376 (11) |
| Zn—O2 | 2.468 (5) | C3—H3 | 0.9300 |
| Zn—O2i | 2.468 (5) | C4—C3 | 1.393 (10) |
| Zn—O3 | 1.993 (5) | C4—H4 | 0.9300 |
| Zn—O3i | 1.993 (5) | C5—C4 | 1.354 (11) |
| O1—C1 | 1.289 (8) | C5—C6 | 1.375 (11) |
| O2—C1 | 1.230 (9) | C6—H6 | 0.9300 |
| O3—H31 | 0.97 (7) | C7—C6 | 1.399 (11) |
| O3—H32 | 0.95 (8) | C7—H7 | 0.9300 |
| O1—Zn—O1i | 98.8 (3) | O2—C1—Zn | 70.5 (4) |
| O1—Zn—O2 | 57.27 (18) | O2—C1—O1 | 120.1 (7) |
| O1i—Zn—O2 | 94.62 (19) | O2—C1—C2 | 123.0 (6) |
| O1—Zn—O2i | 94.62 (19) | C2—C1—Zn | 165.9 (5) |
| O1i—Zn—O2i | 57.27 (18) | C3—C2—C1 | 118.7 (7) |
| O2—Zn—O2i | 138.6 (3) | C7—C2—C1 | 121.6 (6) |
| O3i—Zn—O1 | 100.6 (2) | C7—C2—C3 | 119.7 (7) |
| O3—Zn—O1 | 137.4 (2) | C2—C3—C4 | 120.0 (7) |
| O3i—Zn—O1i | 137.4 (2) | C2—C3—H3 | 120.0 |
| O3—Zn—O1i | 100.6 (2) | C4—C3—H3 | 120.0 |
| O3i—Zn—O2 | 127.7 (2) | C3—C4—H4 | 120.4 |
| O3—Zn—O2 | 83.58 (18) | C5—C4—C3 | 119.1 (7) |
| O3i—Zn—O2i | 83.58 (18) | C5—C4—H4 | 120.4 |
| O3—Zn—O2i | 127.7 (2) | C4—C5—Br | 117.6 (5) |
| O3i—Zn—O3 | 90.0 (3) | C4—C5—C6 | 122.5 (7) |
| C1—O1—Zn | 101.1 (5) | C6—C5—Br | 119.8 (6) |
| C1—O2—Zn | 81.5 (4) | C5—C6—C7 | 118.3 (7) |
| Zn—O3—H32 | 119 (6) | C5—C6—H6 | 120.8 |
| Zn—O3—H31 | 131 (6) | C7—C6—H6 | 120.8 |
| H32—O3—H31 | 106 (4) | C2—C7—C6 | 120.3 (7) |
| O1—C1—Zn | 49.6 (4) | C2—C7—H7 | 119.8 |
| O1—C1—C2 | 116.8 (7) | C6—C7—H7 | 119.8 |
| O1i—Zn—O1—C1 | 89.0 (4) | O1—C1—C2—C7 | −19.9 (10) |
| O2—Zn—O1—C1 | −0.8 (4) | O2—C1—C2—C7 | 162.8 (7) |
| O2i—Zn—O1—C1 | 146.6 (4) | Zn—C1—C2—C3 | 146.9 (18) |
| O3i—Zn—O1—C1 | −129.1 (4) | Zn—C1—C2—C7 | −33 (2) |
| O3—Zn—O1—C1 | −27.4 (6) | O1—C1—C2—C3 | 160.3 (7) |
| C1i—Zn—O1—C1 | 118.5 (4) | O2—C1—C2—C3 | −17.0 (11) |
| O1—Zn—O2—C1 | 0.9 (4) | C1—C2—C3—C4 | 179.7 (7) |
| O1i—Zn—O2—C1 | −96.7 (4) | C7—C2—C3—C4 | −0.1 (12) |
| O2i—Zn—O2—C1 | −53.4 (4) | C1—C2—C7—C6 | −180.0 (7) |
| O3i—Zn—O2—C1 | 78.2 (5) | C3—C2—C7—C6 | −0.2 (12) |
| O3—Zn—O2—C1 | 163.1 (5) | C5—C4—C3—C2 | −0.8 (12) |
| C1i—Zn—O2—C1 | −78.8 (6) | Br—C5—C4—C3 | 179.4 (6) |
| Zn—O1—C1—O2 | 1.6 (8) | C6—C5—C4—C3 | 1.9 (12) |
| Zn—O1—C1—C2 | −175.8 (5) | Br—C5—C6—C7 | −179.6 (6) |
| Zn—O2—C1—O1 | −1.3 (6) | C4—C5—C6—C7 | −2.1 (12) |
| Zn—O2—C1—C2 | 175.9 (7) | C2—C7—C6—C5 | 1.2 (12) |
| Symmetry codes: (i) −x+2, y, −z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O3—H31···O2ii | 0.97 (7) | 1.82 (6) | 2.746 (7) | 157 (9) |
| O3—H32···O1iii | 0.95 (8) | 1.86 (8) | 2.765 (7) | 160 (9) |
| Symmetry codes: (ii) −x+2, −y, −z+1; (iii) −x+2, y−1, −z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O3—H31···O2i | 0.97 (7) | 1.82 (6) | 2.746 (7) | 157 (9) |
| O3—H32···O1ii | 0.95 (8) | 1.86 (8) | 2.765 (7) | 160 (9) |
| Symmetry codes: (i) −x+2, −y, −z+1; (ii) −x+2, y−1, −z+1/2. |
The authors acknowledge the purchase of the CAD-4 diffractometer under grant DPT/TBAG1 of the Scientific and Technical Research Council of Turkey.
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Transition metal complexes with biochemical molecules show interesting physical and/or chemical properties, through which they may find applications in biological systems (Antolini et al., 1982). Some benzoic acid derivatives, such as 4-aminobenzoic acid, have been extensively reported in coordination chemistry, as bifunctional organic ligands, due to the varieties of their coordination modes (Chen & Chen, 2002, Amiraslanov et al., 1979; Hauptmann et al., 2000).
The structure-function-coordination relationships of the arylcarboxylate ion in ZnII complexes of benzoic acid derivatives may also change depending on the nature and position of the substituted groups on the benzene ring, the nature of the additional ligand molecule or solvent, and the pH and temperature of synthesis, as in CoII complexes (Shnulin et al., 1981; Antsyshkina et al., 1980; Adiwidjaja et al., 1978). When pyridine and its derivatives are used instead of water molecules, the structure is completely different (Catterick et al., 1974).
The solid-state structures of anhydrous zinc(II) carboxylates include one-dimensional (Guseinov et al., 1984; Clegg et al., 1986a), two-dimensional (Clegg et al., 1986b, 1987) and three-dimensional (Capilla & Aranda, 1979) polymeric motifs of different types, while discerete monomeric complexes with octahedral or tetrahedral coordination geometry are found if water or other donor molecules are coordinated to Zn (van Niekerk et al., 1953; Usubaliev et al., 1992). In hexaaquazinc(II) bis(4-hydroxybenzoate) dihydrate, [Zn(H2O)6](4-HOC6H4COO)2.2H2O, [(II); Musaev et al., 1983], which is isostructural with the corresponding MgII, CoII, NiII and MnII compounds, the carboxylate ion lies outside the coordination sphere of the Zn atom, while [Zn(4-HOC6H4COO)2].4C5H5N [(III); Nadzhafov et al., 1981], forms a clathrate, consisting of [Zn(4-HOC6H4COO)2(C5H5N)2] units with tetrahedral coordination geometry and free pyridine molecules.
The structure determination of the title compound, (I), a zinc complex with two bromobenzoate (BB) ligands and two water molecules, was undertaken in order to determine the ligand properties of (BB) and also to compare the results obtained with those reported previously.
In the monomeric title complex, [Zn(C7H4O2Br)2(H2O)2], (I), the Zn atom lies on a on a twofold rotation axis and is surrounded by two 4-bromobenzoate (BB), acting as bidentate ligands, and two coordinated water molecules (Fig. 1).
The Zn coordination polyhedron is formed by four clear basal bonds and two close contacts of the symmetry related O2 and O2i atoms, [(i) 2 - x, y, 1/2 - z, Zn···O2 = 2.468 (5) Å, in double dashed lines in Fig. 1] occupying apical positions and completing the six-coordination; this distance is greater than the sum of the corresponding ionic radii (2.14 Å; Day & Selbin, 1969), but similar Zn···O contacts have already been reported, viz.: 2.50 (1) Å in (III), 2.494 (8) Å in [Zn(p—H2NC6H4COO)2]n.1.5nH2O [(IV); Amiraslanov et al., 1980], 2.404 (2) Å in [Zn(C6H6N2O2)2(C7H5O3)2] [(V), (Necefoğlu et al., 2002] and 2.458 (3) Å in [Zn(C7H4O2F)2(C6H6N2O)2].H2O [(VI); Hökelek et al., 2008]. The sixfold coordination around ZnII may thus be described as highly distorted octahedral (Table 1), with the two aqua ligands arranged cis.
In the binuclear complex [Zn2(C7H5O3)4(C10H14N2O)2(H2O)2] [(VII); Hökelek & Necefoğlu, 1996], the average Zn—O bond length [1.953 (2) Å] is shorter than the corresponding value in (I) [2.157 (5) Å], but Zn is four coordinate. In complexes (V), [Zn(C7H4FO2)2(DENA)2(H2O)2] [(VIII); Hökelek et al., 2007] and [Zn(C7H5O3)(OH2)3(C6H6N2O)].C7O3H5 [(IX); Hökelek & Necefoğlu, 2001), (where Zn atoms are five, six and five coordinates) the average Zn—O bond lengths are 2.107 (2) Å, 2.117 (2) Å and 2.047 (5) Å, respectively. In (I), the O1—Zn···O2 angle is 57.27 (18)°. The corresponding O—M···O (where M is a metal) angles are 58.79 (6)° in (V), 57.04 (10)° in (VI), 58.3 (3)° in (VII) and 55.2 (1)° in [Cu(Asp)2(py)2] (where Asp is acetylsalicylate and py is pyridine) [(X); Greenaway et al., 1984].
The near equality of C1—O1 [1.289 (8) Å] and C1—O2 [1.230 (9) Å] bonds in the carboxylate group indicates a delocalized bonding arrangement, rather than localized single and double bonds, as in (V) and [Mn(C9H10NO2)2(H2O)4].2H2O [(XI); Hökelek & Necefoğlu, 2007]. This may be due to the intermolecular hydrogen bonds of the carboxyl O atoms (Table 2). The Zn atom is out of the least-squares plane of the carboxyl group (O1/C1/O2) by 0.055 (1) Å. The dihedral angle between the planar carboxyl group and the benzene ring (C2–C7) is 18.62 (44)°. The corresponding value is reported as 5.54 (43)° in (XI).
The molecules of (I) are linked by intermolecular O—H···O hydrogen bonds (Table 2), forming infinite chains along the [001] direction, which are in turn stacked along the b axis.