Acta Cryst. (2009). E65, i52 [ doi:10.1107/S160053680902251X ]
In an attempt to synthesize new cobalt(II) sulfate framework structures using 1,4-diazabicyclo[2.2.2]octane as a template, crystals of poly[0.35-[hexaaquacobalt(II)] [tri-![[mu]](/logos/entities/mu_rmgif.gif)
-hydroxido--sulfato-dicobalt(II)]], {[Co(H2O)6]0.35[Co2(OH)3(SO4)]}n, were obtained as a mixture with [Co(H2O)6]SO4 crystals. The crystal structure can be described as being constructed from discrete brucite-type [Co4(OH)6(SO4)2] layers, each of which is built up from edge-shared [Co(OH)6] and [Co(OH)4(OSO3)2] octahedra, with partial intercalation by [Co(H2O)6]2+ ions. The absence of ca 30% of the [Co(H2O)6]2+ cations indicates partial oxidation of cobalt(II) to cobalt(III) within the layer.
In the attempt to synthesize new cobalt(II) sulfate frameworks, crystals of I were unintentionally obtained from the hydrothermal reaction of cobalt(II) sulfate heptahydrate and 1,4-diazabicyclo[2.2.2]octane in acidic aqueous solution (pH 4.4) under autogenous pressure at 453 K for 72 h.
Hydrogen atoms were located by difference Fourier methods. The positions of these were refined subject to weak bond length restraints. Displacement parameters for the hydrogen atoms were set at 1.5 times the isotropic diaplcement parameter of the oxygen atom.
Prior to the refinement of site ocupancy of [Co(H2O)6]2+, all atoms were located using Fourier difference methods. The displacement parameters of the intercalating ion were anomalously large. There were large maxima and minima in the residual electron density: e-max = 2.59 e Å-3 (centered on Co2); e-min = -2.58 e Å-3. At this stage wR(F2) = 0.1914.
Refinement of the occupancy of the [Co(H2O)6]2+ cation resulted in a significant improvement in the quality of the fit to the data: e-max = 1.044 e Å-3; e-min = -1.046 e Å-3 and wR(F2) = 0.132.
Careful inspection of the diffraction images did not reveal any weak reflections which might indicate ordering of the partially occupied cation.
Data collection: X-AREA (Stoe & Cie, 2008); cell refinement: X-AREA (Stoe & Cie, 2008); data reduction: X-RED (Stoe & Cie, 2008); program(s) used to solve structure: SHELXS86 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 1999); software used to prepare material for publication: PLATON (Spek, 2009).
![[Figure 1]](./lh2832fig1thm.gif)
| Fig. 1. View of the crystal structure of I along the a axis showing the brucite-type [Co4(SO4)2(OH)6] layers which are intercalatated by the hydrogen bonded (dash lines) [Co(H2O)6]2+ ions. |
![[Figure 2]](./lh2832fig2thm.gif)
| Fig. 2. Polyhedral representation of the cobalt hydroxysulate layer, built up of the edge-shared [Co(OH)6] and [Co(OH)4(OSO3)2] octahedra. |
![[Figure 3]](./lh2832fig3thm.gif)
| Fig. 3. View of the extended asymmetric unit of I with atom numbering scheme. Displacement ellipsoids are drawn at the 80% probability level. |
| [Co(H2O)6]0.35[Co2(OH)3(SO4)] | Dx = 2.515 Mg m−3 |
| Mr = 323.41 | Mo Kα radiation, λ = 0.71073 Å |
| Trigonal, P3m1 | Cell parameters from 1764 reflections |
| Hall symbol: -P 3 2" | θ = 1.7–29.3° |
| a = 6.3627 (19) Å | µ = 4.80 mm−1 |
| c = 12.180 (4) Å | T = 150 K |
| V = 427.0 (2) Å3 | Plate, pale pink |
| Z = 2 | 0.21 × 0.13 × 0.03 mm |
| F(000) = 318.9 |
| Stoe IPDS2 diffractometer | 497 independent reflections |
| Radiation source: fine-focus sealed tube | 325 reflections with I > 2σ(I) |
| graphite | Rint = 0.097 |
| Detector resolution: 6.67 pixels mm-1 | θmax = 29.3°, θmin = 1.7° |
| ω scans | h = −7→8 |
| Absorption correction: multi-scan (X-RED; Stoe & Cie, 2008) | k = −7→8 |
| Tmin = 0.415, Tmax = 0.862 | l = −14→16 |
| 1663 measured reflections |
| 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)] = 0.048 | Hydrogen site location: difference Fourier map |
| wR(F2) = 0.132 | Only H-atom coordinates refined |
| S = 0.90 | w = 1/[σ2(Fo2) + (0.0839P)2] where P = (Fo2 + 2Fc2)/3 |
| 497 reflections | (Δ/σ)max < 0.001 |
| 40 parameters | Δρmax = 1.04 e Å−3 |
| 3 restraints | Δρmin = −1.05 e Å−3 |
| [Co(H2O)6]0.35[Co2(OH)3(SO4)] | Z = 2 |
| Mr = 323.41 | Mo Kα radiation |
| Trigonal, P3m1 | µ = 4.80 mm−1 |
| a = 6.3627 (19) Å | T = 150 K |
| c = 12.180 (4) Å | 0.21 × 0.13 × 0.03 mm |
| V = 427.0 (2) Å3 |
| Stoe IPDS2 diffractometer | 497 independent reflections |
| Absorption correction: multi-scan (X-RED; Stoe & Cie, 2008) | 325 reflections with I > 2σ(I) |
| Tmin = 0.415, Tmax = 0.862 | Rint = 0.097 |
| 1663 measured reflections | θmax = 29.3° |
| R[F2 > 2σ(F2)] = 0.048 | Only H-atom coordinates refined |
| wR(F2) = 0.132 | Δρmax = 1.04 e Å−3 |
| S = 0.90 | Δρmin = −1.05 e Å−3 |
| 497 reflections | Absolute structure: ? |
| 40 parameters | Flack parameter: ? |
| 3 restraints | Rogers parameter: ? |
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 | Occ. (<1) | |
| Co2 | 0.5000 | 0.0000 | 0.5000 | 0.0170 (3) | |
| Co1 | 0.0000 | 0.0000 | 0.5000 | 0.0163 (5) | |
| S1 | 0.6667 | 0.3333 | 0.2679 (2) | 0.0214 (6) | |
| O1 | 0.1717 (3) | −0.1717 (3) | 0.4215 (3) | 0.0164 (9) | |
| O2 | 0.6667 | 0.3333 | 0.3913 (6) | 0.0188 (15) | |
| O3 | 0.5403 (5) | 0.0807 (9) | 0.2298 (4) | 0.0292 (11) | |
| Co3 | 0.0000 | 0.0000 | 0.0000 | 0.0250 (11) | 0.700 (11) |
| O4 | 0.1574 (8) | 0.3148 (16) | 0.0920 (7) | 0.039 (2) | 0.700 (11) |
| H1 | 0.188 (9) | −0.188 (9) | 0.355 (3) | 0.059* | |
| H4 | 0.073 (9) | 0.353 (18) | 0.128 (5) | 0.059* | 0.700 (11) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Co2 | 0.0146 (5) | 0.0156 (6) | 0.0211 (6) | 0.0078 (3) | 0.0001 (2) | 0.0002 (4) |
| Co1 | 0.0144 (6) | 0.0144 (6) | 0.0202 (9) | 0.0072 (3) | 0.000 | 0.000 |
| S1 | 0.0220 (9) | 0.0220 (9) | 0.0203 (12) | 0.0110 (4) | 0.000 | 0.000 |
| O1 | 0.0177 (16) | 0.0177 (16) | 0.0167 (18) | 0.0111 (17) | −0.0002 (8) | 0.0002 (8) |
| O2 | 0.017 (2) | 0.017 (2) | 0.023 (4) | 0.0083 (11) | 0.000 | 0.000 |
| O3 | 0.034 (2) | 0.023 (2) | 0.027 (2) | 0.0116 (12) | −0.0034 (10) | −0.0069 (19) |
| Co3 | 0.0256 (13) | 0.0256 (13) | 0.0238 (17) | 0.0128 (7) | 0.000 | 0.000 |
| O4 | 0.034 (3) | 0.043 (5) | 0.044 (4) | 0.022 (2) | −0.0080 (18) | −0.016 (4) |
| Co2—O1 | 2.047 (3) | S1—O3ix | 1.467 (5) |
| Co2—O1i | 2.047 (3) | S1—O2 | 1.502 (7) |
| Co2—O1ii | 2.047 (3) | O1—Co2x | 2.047 (3) |
| Co2—O1iii | 2.047 (3) | O1—H1 | 0.83 (3) |
| Co2—O2 | 2.264 (4) | O2—Co2viii | 2.264 (4) |
| Co2—O2i | 2.264 (4) | O2—Co2ix | 2.264 (4) |
| Co1—O1iv | 2.121 (4) | Co3—O4xi | 2.065 (8) |
| Co1—O1iii | 2.121 (4) | Co3—O4 | 2.065 (8) |
| Co1—O1v | 2.121 (4) | Co3—O4iv | 2.065 (8) |
| Co1—O1vi | 2.121 (4) | Co3—O4vi | 2.065 (8) |
| Co1—O1 | 2.121 (4) | Co3—O4xii | 2.065 (8) |
| Co1—O1vii | 2.121 (4) | Co3—O4xiii | 2.065 (8) |
| S1—O3 | 1.467 (5) | O4—H4 | 0.82 (3) |
| S1—O3viii | 1.467 (5) | ||
| O1—Co2—O1i | 180.000 (1) | O3viii—S1—O3ix | 110.49 (19) |
| O1—Co2—O1ii | 97.8 (2) | O3—S1—O2 | 108.4 (2) |
| O1i—Co2—O1ii | 82.2 (2) | O3viii—S1—O2 | 108.4 (2) |
| O1—Co2—O1iii | 82.2 (2) | O3ix—S1—O2 | 108.4 (2) |
| O1i—Co2—O1iii | 97.8 (2) | Co2—O1—Co2x | 102.00 (17) |
| O1ii—Co2—O1iii | 180.0 (2) | Co2—O1—Co1 | 99.51 (14) |
| O1—Co2—O2 | 95.83 (13) | Co2x—O1—Co1 | 99.51 (14) |
| O1i—Co2—O2 | 84.17 (13) | Co2—O1—H1 | 112 (4) |
| O1ii—Co2—O2 | 95.83 (13) | Co2x—O1—H1 | 112 (4) |
| O1iii—Co2—O2 | 84.17 (13) | Co1—O1—H1 | 129 (7) |
| O1—Co2—O2i | 84.17 (13) | S1—O2—Co2viii | 125.79 (14) |
| O1i—Co2—O2i | 95.83 (13) | S1—O2—Co2 | 125.79 (14) |
| O1ii—Co2—O2i | 84.17 (13) | Co2viii—O2—Co2 | 89.3 (2) |
| O1iii—Co2—O2i | 95.83 (13) | S1—O2—Co2ix | 125.79 (14) |
| O2—Co2—O2i | 180.0 | Co2viii—O2—Co2ix | 89.3 (2) |
| O1iv—Co1—O1iii | 180.0 (2) | Co2—O2—Co2ix | 89.3 (2) |
| O1iv—Co1—O1v | 78.77 (13) | O4xi—Co3—O4 | 180.0 (4) |
| O1iii—Co1—O1v | 101.23 (13) | O4xi—Co3—O4iv | 86.7 (4) |
| O1iv—Co1—O1vi | 101.23 (13) | O4—Co3—O4iv | 93.3 (4) |
| O1iii—Co1—O1vi | 78.77 (13) | O4xi—Co3—O4vi | 86.7 (4) |
| O1v—Co1—O1vi | 180.00 (15) | O4—Co3—O4vi | 93.3 (4) |
| O1iv—Co1—O1 | 101.23 (13) | O4iv—Co3—O4vi | 93.3 (4) |
| O1iii—Co1—O1 | 78.77 (13) | O4xi—Co3—O4xii | 93.3 (4) |
| O1v—Co1—O1 | 78.77 (13) | O4—Co3—O4xii | 86.7 (4) |
| O1vi—Co1—O1 | 101.23 (13) | O4iv—Co3—O4xii | 86.7 (4) |
| O1iv—Co1—O1vii | 78.77 (13) | O4vi—Co3—O4xii | 180.0 (4) |
| O1iii—Co1—O1vii | 101.23 (13) | O4xi—Co3—O4xiii | 93.3 (4) |
| O1v—Co1—O1vii | 101.23 (13) | O4—Co3—O4xiii | 86.7 (4) |
| O1vi—Co1—O1vii | 78.77 (13) | O4iv—Co3—O4xiii | 180.0 (4) |
| O1—Co1—O1vii | 180.0 (2) | O4vi—Co3—O4xiii | 86.7 (4) |
| O3—S1—O3viii | 110.49 (19) | O4xii—Co3—O4xiii | 93.3 (4) |
| O3—S1—O3ix | 110.49 (19) | Co3—O4—H4 | 120 (5) |
| Symmetry codes: (i) −x+1, −y, −z+1; (ii) −x+y+1, −x, z; (iii) x−y, x, −z+1; (iv) −x+y, −x, z; (v) y, −x+y, −z+1; (vi) −y, x−y, z; (vii) −x, −y, −z+1; (viii) −y+1, x−y, z; (ix) −x+y+1, −x+1, z; (x) −y, x−y−1, z; (xi) −x, −y, −z; (xii) y, −x+y, −z; (xiii) x−y, x, −z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O1—H1···O3x | 0.83 (3) | 2.54 (5) | 3.125 (6) | 129 (4) |
| O1—H1···O3 | 0.83 (3) | 2.54 (5) | 3.125 (6) | 129 (4) |
| O4—H4···O3vi | 0.82 (3) | 1.90 (9) | 2.712 (1) | 170 (7) |
| Symmetry codes: (x) −y, x−y−1, z; (vi) −y, x−y, z. |
The authors thank the Thailand Research Fund, the Center for Innovation in Chemistry and the Thailand Toray Science Foundation for financial support. BY thanks the Royal Golden Jubilee PhD program and the Graduate School of Chiang Mai University for a Graduate Scholarship.
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Layered transition-metal hydroxides, in particular those exhibiting the brucite structure, have gained serious interest in both chemical and physical aspects. While the intercalation chemistry and potential application as catalysts are of the prime interest for the chemists, the physical interest primarily stems from the long-rang magnetic ordering in two dimensions. Examples of two dimensional triangular networks exhibiting such ordering are very rare, and the information on the crystal structures of layered materials of this type is yet rarer (Poudret, 2008). Thusfar there has been only one structure, Co5(OH)6(SO4)2(H2O)4, having the truely brucite-type magnetic layer (Ben Salah et al., 2004). The nuclear and magnetic structures, and magnetic properties of the compound were extensively reported (Ben Salah et al., 2006). The crystal structure of Co5(OH)6(SO4)2(H2O)4 consists of brucite-type cobalt hydroxide layers of edge-sharing octahedra, which are pillared by ··· O3SO—Co(H2O)4—OSO3··· groups. The compound exhibits ferromagnetic coupling with purely two dimensional magnetic ordering in an easy-plane magnet, which is a rare example of a single-layer magnet.
The crystal structure of [Co(H2O)6]x[Co4(SO4)2(OH)6] (I) where x ≈ 0.70 is closely related to that of Co5(OH)6(SO4)2(H2O)4 (Fig. 1), also comprised of brucite-type [Co4(SO4)2(OH)6] layers, each of which is built up from the edge-shared [Co(OH)6] and [Co(OH)4(OSO3)2] octahedra in the ab plane (Fig. 2). Two of three crystallographically distinct cobalt ions (Fig. 3), Co1 and Co2, are within the layers and located on the 1b and 3f Wyckoff sites, respectively. Unlike the Co5(OH)6(SO4)2(H2O)4 structure, the sulfate anion acts as a monodentate ligand and is coordinate covalently connected to the layered Co2 ion via the apical O atom, leaving the three basal O atoms pointing into the interlayered space (Fig. 3). The [Co4(SO4)2(OH)6] layers are stacked in the ABAB fashion along c, with a repeat distance of 12.180 (4) Å. In the interlayered gallery, there are intercalated discrete [Co(H2O)6]2+ ions in which the Co3 is located on the 1a site. These [Co(H2O)6]2+ ions are aligned in a way to maximize the hydrogen bonding interactions of O—H···O type between the aquo ligands and the basal O atoms of the layered sulfate pendants (Fig. 1). The orientation of the sulfate is also regulated by the hydrogen bonds established between the sulfate basal O atoms and the layered hydroxy groups. The Co—O bond length (2.065 (8) Å) within the hexaaquo ion is in good agreement with similar cations in the Cambridge Structural Database (Allen, 2002). The mean of similar Co—O distances is 2.09 (3) Å, but is notable that the majority of these structures were collected at room temperature. 97% of the structures containing cobalt hexaaquo ions are explicitly recorded at Co2+, none are recorded as Co3+.
The refined site occupancy of the intercalated [Co(H2O)6]2+ ions and the assumption of total charge neutrality imply the partial oxidation (15%) of the layer CoII to CoIII. This yields an overall composition [CoII(H2O)6]0.7[CoII3.4CoIII0.6(SO4)2(OH)6] for I .