Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104030409/fr1511sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270104030409/fr1511Isup2.hkl |
CCDC reference: 263034
A solution of cobalt(II) chloride hexahydrate (1.2 g, 5.0 mmol) in water (10 ml) was added dropwise to an aqueous solution (10 ml) of potassium oxalate (1.2 g, 6.2 mmol). The resulting microcrystalline precipitate of [Co(C2O4)]·2H2O was transferred to a 23 ml Teflon-lined autoclave. The autoclave was sealed, transferred to an oven and heated to 483 K for 12 h. Small pink crystals of (I), as well as dark-blue soluble crystals of cobalt(II) chloride, were obtained on slowly cooling the mixture to room temperature.
All H atoms were located from difference electron-density maps and refined isotropically with distances restrained. Please give brief details of restraints used.
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: Please provide missing information.
[Co(C2O4)(H2O)2] | F(000) = 364 |
Mr = 182.98 | Dx = 2.446 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 1356 reflections |
a = 11.707 (2) Å | θ = 3.5–27.4° |
b = 5.4487 (10) Å | µ = 3.41 mm−1 |
c = 9.6477 (19) Å | T = 298 K |
β = 126.155 (8)° | Plate, pink |
V = 496.89 (17) Å3 | 0.11 × 0.08 × 0.03 mm |
Z = 4 |
Bruker SMART APEX CCD area-detector diffractometer | 565 independent reflections |
Radiation source: fine-focus sealed tube | 542 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.020 |
ω and ϕ scans | θmax = 27.4°, θmin = 4.3° |
Absorption correction: multi-scan (SADABS; Bruker, 2003) | h = −14→8 |
Tmin = 0.708, Tmax = 0.911 | k = −5→7 |
1722 measured reflections | l = −11→12 |
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)] = 0.032 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.089 | All H-atom parameters refined |
S = 1.15 | w = 1/[σ2(Fo2) + (0.0404P)2 + 2.8955P] where P = (Fo2 + 2Fc2)/3 |
565 reflections | (Δ/σ)max < 0.001 |
50 parameters | Δρmax = 0.83 e Å−3 |
2 restraints | Δρmin = −0.72 e Å−3 |
[Co(C2O4)(H2O)2] | V = 496.89 (17) Å3 |
Mr = 182.98 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 11.707 (2) Å | µ = 3.41 mm−1 |
b = 5.4487 (10) Å | T = 298 K |
c = 9.6477 (19) Å | 0.11 × 0.08 × 0.03 mm |
β = 126.155 (8)° |
Bruker SMART APEX CCD area-detector diffractometer | 565 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2003) | 542 reflections with I > 2σ(I) |
Tmin = 0.708, Tmax = 0.911 | Rint = 0.020 |
1722 measured reflections |
R[F2 > 2σ(F2)] = 0.032 | 2 restraints |
wR(F2) = 0.089 | All H-atom parameters refined |
S = 1.15 | Δρmax = 0.83 e Å−3 |
565 reflections | Δρmin = −0.72 e Å−3 |
50 parameters |
Experimental. The crystals were extermely small. Approximately a hemisphere of diffraction data in reciprocal space were collected by a combination of three sets of exposures: two 180° ω scans and one 70° ϕ scan. Exposure times of 30 s per frame and scan widths of 0.5° were used throughout the data collection. Crystal decay was monitored by analyzing duplicate reflections, and found to be negligible, therefore no decay correction was applied. |
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 | ||
Co | 0.5000 | 0.07229 (10) | 0.7500 | 0.0092 (2) | |
O1 | 0.4127 (2) | 0.3672 (4) | 0.5768 (3) | 0.0101 (5) | |
O2 | 0.4122 (2) | 0.7782 (4) | 0.5769 (3) | 0.0101 (5) | |
O3 | 0.3249 (2) | 0.0646 (4) | 0.7572 (3) | 0.0114 (5) | |
C1 | 0.4487 (3) | 0.5748 (5) | 0.6492 (4) | 0.0087 (6) | |
H1 | 0.235 (3) | 0.111 (9) | 0.650 (4) | 0.041 (14)* | |
H2 | 0.339 (6) | 0.136 (10) | 0.859 (4) | 0.048 (15)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Co | 0.0115 (3) | 0.0058 (3) | 0.0093 (3) | 0.000 | 0.0055 (3) | 0.000 |
O1 | 0.0120 (10) | 0.0069 (10) | 0.0091 (10) | −0.0005 (8) | 0.0049 (9) | −0.0009 (8) |
O2 | 0.0127 (11) | 0.0078 (10) | 0.0086 (10) | −0.0001 (8) | 0.0057 (9) | −0.0007 (8) |
O3 | 0.0109 (11) | 0.0137 (12) | 0.0081 (10) | 0.0026 (8) | 0.0047 (9) | −0.0009 (8) |
C1 | 0.0077 (14) | 0.0102 (14) | 0.0091 (15) | −0.0006 (11) | 0.0055 (13) | −0.0012 (10) |
Co—O3 | 2.093 (2) | O2—C1 | 1.243 (4) |
Co—O2i | 2.095 (2) | C1—C1ii | 1.571 (6) |
Co—O1 | 2.099 (2) | O3—H1 | 0.98 (4) |
O1—C1 | 1.264 (4) | O3—H2 | 0.98 (4) |
O1ii—Co—O1 | 80.07 (12) | O2iii—Co—O1 | 179.81 (8) |
O2i—Co—O1 | 99.87 (9) | C1—O1—Co | 113.44 (19) |
O3—Co—O3ii | 177.70 (13) | O2—C1—O1 | 126.5 (3) |
O3—Co—O2i | 88.96 (8) | O2—C1—C1ii | 116.97 (16) |
O3—Co—O2iii | 89.28 (9) | O1—C1—C1ii | 116.52 (16) |
O2i—Co—O2iii | 80.18 (12) | Co—O3—H1 | 115 (3) |
O3—Co—O1 | 90.90 (9) | Co—O3—H2 | 116 (3) |
O3—Co—O1ii | 90.86 (9) | H1—O3—H2 | 113 (5) |
O2i—Co—O1 | 99.87 (9) | ||
O1—C1—C1ii—O1ii | −1 (1) | Co—O1—C1—C1ii | 0.7 (4) |
O1—C1—C1ii—O2ii | 179.7 (2) | Co—O2iii—C1iii—C1i | −0.2 (4) |
Symmetry codes: (i) x, y−1, z; (ii) −x+1, y, −z+3/2; (iii) −x+1, y−1, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H2···O2iv | 0.98 (4) | 1.80 (4) | 2.751 (3) | 164 (5) |
O3—H1···O1v | 0.98 (4) | 1.83 (4) | 2.772 (3) | 162 (5) |
Symmetry codes: (iv) x, −y+1, z+1/2; (v) −x+1/2, −y+1/2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Co(C2O4)(H2O)2] |
Mr | 182.98 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 298 |
a, b, c (Å) | 11.707 (2), 5.4487 (10), 9.6477 (19) |
β (°) | 126.155 (8) |
V (Å3) | 496.89 (17) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 3.41 |
Crystal size (mm) | 0.11 × 0.08 × 0.03 |
Data collection | |
Diffractometer | Bruker SMART APEX CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2003) |
Tmin, Tmax | 0.708, 0.911 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1722, 565, 542 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.648 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.032, 0.089, 1.15 |
No. of reflections | 565 |
No. of parameters | 50 |
No. of restraints | 2 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.83, −0.72 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), X-SEED (Barbour, 2001), Please provide missing information.
Co—O3 | 2.093 (2) | O1—C1 | 1.264 (4) |
Co—O2i | 2.095 (2) | O2—C1 | 1.243 (4) |
Co—O1 | 2.099 (2) | C1—C1ii | 1.571 (6) |
O1ii—Co—O1 | 80.07 (12) | O2i—Co—O2iii | 80.18 (12) |
O2i—Co—O1 | 99.87 (9) | O3—Co—O1 | 90.90 (9) |
O3—Co—O3ii | 177.70 (13) | O3—Co—O1ii | 90.86 (9) |
O3—Co—O2i | 88.96 (8) | O2i—Co—O1 | 99.87 (9) |
O3—Co—O2iii | 89.28 (9) | ||
O1—C1—C1ii—O1ii | −1 (1) | Co—O1—C1—C1ii | 0.7 (4) |
O1—C1—C1ii—O2ii | 179.7 (2) | Co—O2iii—C1iii—C1i | −0.2 (4) |
Symmetry codes: (i) x, y−1, z; (ii) −x+1, y, −z+3/2; (iii) −x+1, y−1, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H2···O2iv | 0.98 (4) | 1.80 (4) | 2.751 (3) | 164 (5) |
O3—H1···O1v | 0.98 (4) | 1.83 (4) | 2.772 (3) | 162 (5) |
Symmetry codes: (iv) x, −y+1, z+1/2; (v) −x+1/2, −y+1/2, −z+1. |
Polymeric divalent metal oxalates tend to form microcrystalline precipitates that are difficult to characterize by single-crystal X-ray diffraction. Rare prismatic crystals of whewellite {[Ca(C2O4)]·H2O} up to 100 mm long have been discovered in Kladno, Czech Republic (Korbel & Novak, 1999), and diffraction quality crystals of humboldtine {[Fe(C2O4)]·2H2O} can be found as hydrothermal deposits in coal basins.
The mineral humboldtine crystallizes in the space group C2/c and consists of one-dimensional chains of [FeII(C2O4)(H2O)2] units with bridging oxalate ions (Caric, 1959). One-dimensional coordination polymers are important for studying fundamental theoretical aspects of magnetism in the solid state.
Metal oxalates have also been subjected to detailed thermal analyses and the results used in establishing theoretical concepts applicable to solid-state reactions (see, for example, Coetzee et al., 1994). Two different forms of ferrous oxalate dihydrate (α and β) have been characterized (Deyrieux & Peneloux, 1969), but the α form, humboldtine, is the more common. Powder diffraction patterns of the α-oxalates [M(C2O4)]·2H2O (M = Mg, Mn, Fe, Co, Ni and Zn) have been indexed in the monoclinic space group C2/c with nearly identical cell parameters. The crystal structures of α-oxalates [M(C2O4)]·2H2O (M = Mn, Co, Ni and Zn) have been studied by Lagier et al. (1969) and Deyrieux et al. (1973) using powder diffraction.
The atomic coordinates of humboldtine have been used as starting values for a least-squares refinement based on fitting the calculated and observed intensity profiles of a powder diffraction pattern of microcrystalline [Mn(C2O4)]·two-dimensional2O (Śledzińska et al., 1987). These results, and diffraction studies on single crystals of [Zn(C2O4)]·2H2O (Bacsa, 1995), confirm that these oxalates are isostructural and isomorphous. A new hydrated phase of cobalt oxalate crystallizes in the triclinic space group P1 with similar cell parameters to the α-forms (Castillo et al., 2004). Here, we report the crystal structure of the title compound, (I), prepared by hydrothermal methods. \sch
The structure of (I) consists of infinite chains of [Co(C2O4)(H2O)2] units which lie on twofold symmetry axes parallel to the b axis (Fig. 1). The neighbouring chains are parallel but displaced by 0.787 (1) Å relative to each other along the b axis. In this arrangement, the H atoms of the water molecules are in favourable positions for donating normal hydrogen bonds to oxalate O atoms (Fig. 2). This network of hydrogen bonds is in an up-down arrangement along these chains, i.e. when an oxalate O accepts a hydrogen bond above the [Co(C2O4)]n plane, the next O atom on the same side of the chain accepts a bond below the plane of the oxalate group. The separation of the CoII atoms along the chains coincides with the repeat distance of the b axis. The closest interchain spacing is 4.9 Å, and the CoII atoms are located on crystallographic planes with indices (200) and with a repeat distance of 5.853 (1) Å. The reflection (200) in the powder diffraction patterns of the α-oxalates is the most intense, and studies (Masuda et al., 1987) show that crystals of these oxalates have perfect cleavage planes parallel to the (100) plane.
The oxalate ions in (I) are bis-bidentate and bridge the Co atoms sideways rather than head-on, i.e. each oxalate ion forms two five-membered chelate rings rather than two four-membered rings. The O.·O distance [2.700 (3) versus 2.239 (3) Å Source of reference value?] in this arrangement is better for forming a stable octahedral coordination geometry about each CoII atom with slight distortion.
The bridging oxalate ions and Co atoms are nearly planar within experimental error, and since the chains lie on twofold axes, the entire [Co(C2O4)]n system is also planar. This planarity suggests the existence of delocalized bonding involving all the equatorial atoms. The C—C bond distance is slightly longer than that typically found in other oxalates (Cambridge Structural Database, Version?; Allen, 2002). According to the bond-valence model (Brown, 2002), this bond should be an electron-pair bond and have a distance of 1.54 Å. Electron density that would be expected to be within this bond is likely to have been transferred to the C—O and Co—O bonds, resulting in a longer bond (Mak & Zhou, 1992).
The water molecule is tilted toward atom O1 and away from atom O2 (within each chain). The O—Co—O(H2O) coordination angles are close to the ideal octahedral values, but the O—Co—O angles within the two unique chelate rings are acute, while the remaining unique angle is obtuse. The bond angle of the carboxylate O—C—O group is 126.5 (3)°. The ideal O—C—O angle in the oxalate ion is close to 120°. This bond angle widens to accommodate the Co atom. However, this angle is rigid and distorts to a lesser extent than the coordination angles. The two pairs of Co—O equatorial bonds are the same within experimental error. The axial Co—O(H2O) bond is almost exactly the same length as the equatorial bonds.
The structure of (I) is held together by an ordered network of coordination and hydrogen bonds. A disruption of any of these is likely to break the chains. Therefore, the crystals are small but diffract well, perhaps indicating a nearly perfectly ordered structure.