metal-organic compounds
catena-Poly[[cobalt(II)-μ-aqua-di-μ-butanoato-κ2O:O′;κ2O:O] 0.7-hydrate]
aSt Petersburg State Institute of Technology, Moskovsky pr. 26, 190013 St Petersburg, Russian Federation, and bSt Petersburg State University, Universitetskaya nab. 7/9, 199034 St Petersburg, Russian Federation
*Correspondence e-mail: andreasfischer@mail.ru
In the title coordination polymer, {[Co(C3H7COO)2(H2O)]·0.7H2O}n, the Co2+ cation is coordinated by four bridging butanoate anions and two bridging water molecules in a severely distorted octahedral geometry. The Co2+ cations are linked by means of bridging ligands into polymeric chains along [010]. These chains are further connected to each other through hydrogen bonds involving partially occupied disordered water molecules; thus, sheets parallel to (001) are formed. One of the positions of disordered water O atom lies on a twofold axis. Two atoms of the aliphatic chain of one of the butanoate anions are disordered over two positions each.
Related literature
For properties and applications of cobalt carboxylates, see: Eremenko et al. (2009); Gates (1992); Parshall & Ittel (1992); Partenheimer (1995). For related structures, see: Jiao et al. (2000); Fischer et al. (2010).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).
Supporting information
10.1107/S1600536811019271/ya2137sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811019271/ya2137Isup2.hkl
To a solution of butyric acid (8.8 g, 100 mmol) in water (50 ml), an excess of fresh cobalt(II) carbonate hydrate, CoCO3.xH2O (x=0.35–1.00), (8.0 g, approximately 60 mmol) was added. The reaction mixture was periodically stirred in ultrasonic bath at room temperature until the liberation of carbon dioxide ceased. The unreacted CoCO3.xH2O was removed by filtration, and the filtrate was allowed to stand at room temperature for slow evaporation. After a few days, red single crystals of the title compound suitable for X-ray diffraction study precipitated. Yield 82%.
The propyl group of the bidentate carboxylate ligand is disordered over two positions in a 65:35 ratio. The solvate water molecule is disordered over two noneqivalent positions (O61—O62 = 0.76 (1) Å) with the total s.o.f. equal to 0.7 (Fig. 2); positions O61 and O62 were refined isotropically. The H atoms bound to O2 where located in the difference map and refined with O—H distances restrained to 0.95 (1) Å and Uiso(H) set to 1.5Ueq(O); other oxygen-bound H atoms where not included in
Carbon-bound H-atoms were placed in calculated positions and were included in the in the riding model approximation, with Uiso(H) set to 1.5Ueq(C) and C—H 0.96Å for the methyl groups and 1.2Ueq(C) and C—H 0.97 Å for the methylene groups.Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).[Co(C4H7O2)2(H2O)]·0.7H2O | F(000) = 1104 |
Mr = 263.75 | Dx = 1.516 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 1731 reflections |
a = 14.8377 (13) Å | θ = 2.7–23.0° |
b = 6.2597 (7) Å | µ = 1.49 mm−1 |
c = 25.743 (3) Å | T = 210 K |
β = 104.900 (3)° | Plate, red |
V = 2310.6 (4) Å3 | 0.10 × 0.08 × 0.03 mm |
Z = 8 |
Bruker APEXII CCD diffractometer | 2731 independent reflections |
Radiation source: fine-focus sealed tube | 1752 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.096 |
ϕ and ω scans | θmax = 27.7°, θmin = 1.6° |
Absorption correction: multi-scan (SADABS; Bruker, 2007) | h = −19→19 |
Tmin = 0.301, Tmax = 0.351 | k = −8→8 |
12584 measured reflections | l = −33→33 |
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)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.096 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.82 | w = 1/[σ2(Fo2) + (0.0493P)2] where P = (Fo2 + 2Fc2)/3 |
2731 reflections | (Δ/σ)max < 0.001 |
156 parameters | Δρmax = 0.62 e Å−3 |
2 restraints | Δρmin = −0.58 e Å−3 |
[Co(C4H7O2)2(H2O)]·0.7H2O | V = 2310.6 (4) Å3 |
Mr = 263.75 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 14.8377 (13) Å | µ = 1.49 mm−1 |
b = 6.2597 (7) Å | T = 210 K |
c = 25.743 (3) Å | 0.10 × 0.08 × 0.03 mm |
β = 104.900 (3)° |
Bruker APEXII CCD diffractometer | 2731 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2007) | 1752 reflections with I > 2σ(I) |
Tmin = 0.301, Tmax = 0.351 | Rint = 0.096 |
12584 measured reflections |
R[F2 > 2σ(F2)] = 0.042 | 2 restraints |
wR(F2) = 0.096 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.82 | Δρmax = 0.62 e Å−3 |
2731 reflections | Δρmin = −0.58 e Å−3 |
156 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 | Occ. (<1) | |
Co1 | 0.75276 (3) | 0.06070 (7) | 0.255905 (16) | 0.02732 (14) | |
O1 | 0.75332 (18) | −0.4281 (4) | 0.37058 (9) | 0.0446 (6) | |
O2 | 0.69231 (15) | 0.3197 (3) | 0.29117 (9) | 0.0306 (5) | |
HO2A | 0.6277 (13) | 0.294 (6) | 0.2786 (13) | 0.046* | |
HO2B | 0.715 (2) | 0.410 (5) | 0.3222 (10) | 0.046* | |
O3 | 0.88459 (16) | 0.1401 (3) | 0.29628 (9) | 0.0383 (6) | |
O4 | 0.75018 (16) | −0.2058 (3) | 0.30335 (8) | 0.0330 (5) | |
O5 | 0.61852 (16) | −0.0070 (3) | 0.21419 (9) | 0.0382 (6) | |
O61 | 0.5000 | 0.3285 (15) | 0.2500 | 0.073 (3)* | 0.60 |
O62 | 0.4987 (6) | 0.3237 (17) | 0.2794 (4) | 0.083 (2)* | 0.40 |
C1 | 0.7659 (2) | −0.2489 (5) | 0.35404 (13) | 0.0318 (8) | |
C2 | 0.8038 (3) | −0.0718 (6) | 0.39244 (13) | 0.0452 (9) | |
H2A | 0.7651 | 0.0535 | 0.3814 | 0.054* | |
H2B | 0.8659 | −0.0373 | 0.3893 | 0.054* | |
C3 | 0.8095 (4) | −0.1141 (7) | 0.45058 (15) | 0.0655 (13) | |
H3A | 0.8476 | −0.2399 | 0.4619 | 0.079* | |
H3B | 0.7474 | −0.1450 | 0.4543 | 0.079* | |
C4 | 0.8496 (4) | 0.0687 (9) | 0.48730 (18) | 0.0932 (18) | |
H4A | 0.9131 | 0.0923 | 0.4864 | 0.140* | |
H4B | 0.8474 | 0.0349 | 0.5233 | 0.140* | |
H4C | 0.8137 | 0.1956 | 0.4756 | 0.140* | |
C5 | 0.9218 (2) | 0.3213 (6) | 0.30284 (12) | 0.0318 (7) | |
C6 | 1.0235 (2) | 0.3339 (7) | 0.33334 (17) | 0.0537 (11) | |
H6A | 1.0615 | 0.3540 | 0.3082 | 0.064* | 0.65 |
H6B | 1.0421 | 0.2010 | 0.3524 | 0.064* | 0.65 |
H6C | 1.0476 | 0.4689 | 0.3241 | 0.064* | 0.35 |
H6D | 1.0544 | 0.2149 | 0.3210 | 0.064* | 0.35 |
C71 | 1.0404 (5) | 0.5282 (15) | 0.3753 (3) | 0.079 (3) | 0.65 |
H71A | 1.1063 | 0.5620 | 0.3874 | 0.095* | 0.65 |
H71B | 1.0070 | 0.6546 | 0.3590 | 0.095* | 0.65 |
C81 | 1.0027 (8) | 0.450 (3) | 0.4231 (4) | 0.092 (4) | 0.65 |
H81A | 1.0102 | 0.5616 | 0.4495 | 0.138* | 0.65 |
H81B | 1.0369 | 0.3262 | 0.4390 | 0.138* | 0.65 |
H81C | 0.9378 | 0.4150 | 0.4103 | 0.138* | 0.65 |
C72 | 1.0412 (9) | 0.272 (3) | 0.3901 (5) | 0.072 (4) | 0.35 |
H72A | 1.1054 | 0.2295 | 0.4055 | 0.087* | 0.35 |
H72B | 0.9991 | 0.1616 | 0.3960 | 0.087* | 0.35 |
C82 | 1.014 (3) | 0.536 (5) | 0.4137 (14) | 0.128 (16)* | 0.35 |
H82A | 0.9483 | 0.5481 | 0.4091 | 0.192* | 0.35 |
H82B | 1.0349 | 0.6452 | 0.3933 | 0.192* | 0.35 |
H82C | 1.0459 | 0.5517 | 0.4510 | 0.192* | 0.35 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Co1 | 0.0312 (2) | 0.0181 (2) | 0.0311 (2) | 0.0017 (2) | 0.00511 (17) | −0.00010 (19) |
O1 | 0.0666 (17) | 0.0335 (14) | 0.0332 (13) | −0.0048 (14) | 0.0119 (11) | 0.0038 (12) |
O2 | 0.0299 (12) | 0.0232 (11) | 0.0383 (13) | −0.0021 (11) | 0.0079 (10) | −0.0033 (10) |
O3 | 0.0349 (13) | 0.0251 (12) | 0.0491 (15) | 0.0021 (10) | 0.0005 (11) | −0.0009 (10) |
O4 | 0.0445 (14) | 0.0238 (11) | 0.0284 (13) | 0.0018 (11) | 0.0054 (10) | 0.0019 (9) |
O5 | 0.0379 (13) | 0.0244 (13) | 0.0465 (14) | 0.0047 (10) | 0.0002 (11) | −0.0018 (9) |
C1 | 0.0345 (19) | 0.0289 (18) | 0.0308 (19) | 0.0022 (14) | 0.0062 (15) | 0.0002 (13) |
C2 | 0.059 (2) | 0.041 (2) | 0.0350 (19) | −0.006 (2) | 0.0108 (17) | −0.0055 (17) |
C3 | 0.091 (3) | 0.065 (3) | 0.035 (2) | −0.005 (3) | 0.006 (2) | −0.0091 (19) |
C4 | 0.134 (5) | 0.090 (4) | 0.049 (3) | −0.013 (4) | 0.013 (3) | −0.028 (3) |
C5 | 0.0287 (17) | 0.0374 (19) | 0.0292 (18) | −0.0027 (16) | 0.0070 (14) | −0.0018 (14) |
C6 | 0.030 (2) | 0.064 (3) | 0.062 (3) | 0.001 (2) | 0.0039 (18) | 0.002 (2) |
C71 | 0.040 (4) | 0.106 (7) | 0.080 (6) | −0.007 (4) | −0.004 (4) | −0.036 (5) |
C81 | 0.072 (6) | 0.142 (14) | 0.053 (5) | 0.003 (8) | −0.004 (5) | −0.029 (8) |
C72 | 0.040 (7) | 0.113 (14) | 0.051 (8) | −0.006 (7) | −0.010 (6) | 0.015 (8) |
Co1—O3 | 2.027 (2) | C4—H4A | 0.9599 |
Co1—O5 | 2.049 (2) | C4—H4B | 0.9599 |
Co1—O4 | 2.074 (2) | C4—H4C | 0.9599 |
Co1—O4i | 2.105 (2) | C5—O5i | 1.253 (4) |
Co1—O2 | 2.163 (2) | C5—C6 | 1.512 (5) |
Co1—O2ii | 2.217 (2) | C6—C72 | 1.468 (13) |
O1—C1 | 1.231 (4) | C6—C71 | 1.604 (8) |
O2—Co1i | 2.217 (2) | C6—H6A | 0.9700 |
O2—HO2A | 0.943 (18) | C6—H6B | 0.9700 |
O2—HO2B | 0.966 (18) | C6—H6C | 0.9702 |
O3—C5 | 1.254 (4) | C6—H6D | 0.9699 |
O4—C1 | 1.293 (4) | C71—C81 | 1.555 (17) |
O4—Co1ii | 2.105 (2) | C71—H71A | 0.9700 |
O5—C5ii | 1.253 (4) | C71—H71B | 0.9700 |
O61—O62iii | 0.763 (10) | C81—H81A | 0.9599 |
O61—O62 | 0.763 (10) | C81—H81B | 0.9599 |
O62—O62iii | 1.53 (2) | C81—H81C | 0.9599 |
C1—C2 | 1.496 (4) | C72—C82 | 1.84 (4) |
C2—C3 | 1.501 (5) | C72—H72A | 0.9700 |
C2—H2A | 0.9700 | C72—H72B | 0.9700 |
C2—H2B | 0.9700 | C82—H82A | 0.9599 |
C3—C4 | 1.506 (6) | C82—H82B | 0.9599 |
C3—H3A | 0.9700 | C82—H82C | 0.9599 |
C3—H3B | 0.9700 | ||
O3—Co1—O5 | 177.71 (9) | H4B—C4—H4C | 109.5 |
O3—Co1—O4 | 93.25 (9) | O5i—C5—O3 | 125.0 (3) |
O5—Co1—O4 | 88.83 (9) | O5i—C5—C6 | 117.4 (3) |
O3—Co1—O4i | 92.23 (9) | O3—C5—C6 | 117.6 (3) |
O5—Co1—O4i | 85.85 (9) | C72—C6—C5 | 113.7 (6) |
O4—Co1—O4i | 170.17 (8) | C72—C6—C71 | 64.7 (7) |
O3—Co1—O2 | 92.90 (9) | C5—C6—C71 | 110.6 (4) |
O5—Co1—O2 | 85.58 (9) | C72—C6—H6A | 135.4 |
O4—Co1—O2 | 106.47 (9) | C5—C6—H6A | 109.5 |
O4i—Co1—O2 | 81.38 (9) | C71—C6—H6A | 109.5 |
O3—Co1—O2ii | 90.30 (9) | C72—C6—H6B | 46.7 |
O5—Co1—O2ii | 90.99 (9) | C5—C6—H6B | 109.5 |
O4—Co1—O2ii | 80.77 (9) | C71—C6—H6B | 109.5 |
O4i—Co1—O2ii | 91.05 (8) | H6A—C6—H6B | 108.1 |
O2—Co1—O2ii | 171.88 (6) | C72—C6—H6C | 119.3 |
Co1—O2—Co1i | 91.73 (8) | C5—C6—H6C | 107.5 |
Co1—O2—HO2A | 103 (2) | C71—C6—H6C | 60.0 |
Co1i—O2—HO2A | 114 (2) | H6A—C6—H6C | 53.8 |
Co1—O2—HO2B | 134 (2) | H6B—C6—H6C | 142.7 |
Co1i—O2—HO2B | 87 (2) | C72—C6—H6D | 98.2 |
HO2A—O2—HO2B | 119 (3) | C5—C6—H6D | 106.4 |
C5—O3—Co1 | 128.7 (2) | C71—C6—H6D | 142.9 |
C1—O4—Co1 | 137.4 (2) | H6A—C6—H6D | 58.5 |
C1—O4—Co1ii | 123.4 (2) | H6B—C6—H6D | 53.8 |
Co1—O4—Co1ii | 97.58 (9) | H6C—C6—H6D | 110.7 |
C5ii—O5—Co1 | 132.3 (2) | C81—C71—C6 | 105.6 (8) |
O62iii—O61—O62 | 175 (3) | C81—C71—H6C | 142.4 |
O61—O62—O62iii | 2.3 (13) | C6—C71—H6C | 36.9 |
O1—C1—O4 | 122.3 (3) | C81—C71—H71A | 110.6 |
O1—C1—C2 | 120.8 (3) | C6—C71—H71A | 110.6 |
O4—C1—C2 | 116.9 (3) | H6C—C71—H71A | 92.6 |
C1—C2—C3 | 116.3 (3) | C81—C71—H71B | 110.6 |
C1—C2—H2A | 108.2 | C6—C71—H71B | 110.6 |
C3—C2—H2A | 108.2 | H6C—C71—H71B | 87.8 |
C1—C2—H2B | 108.2 | H71A—C71—H71B | 108.7 |
C3—C2—H2B | 108.2 | C6—C72—C82 | 95.4 (14) |
H2A—C2—H2B | 107.4 | C6—C72—H72A | 112.7 |
C2—C3—C4 | 113.8 (4) | C82—C72—H72A | 112.7 |
C2—C3—H3A | 108.8 | C6—C72—H72B | 112.7 |
C4—C3—H3A | 108.8 | C82—C72—H72B | 112.7 |
C2—C3—H3B | 108.8 | H72A—C72—H72B | 110.2 |
C4—C3—H3B | 108.8 | C72—C82—H82A | 109.5 |
H3A—C3—H3B | 107.7 | C72—C82—H82B | 109.5 |
C3—C4—H4A | 109.5 | H82A—C82—H82B | 109.5 |
C3—C4—H4B | 109.5 | C72—C82—H82C | 109.5 |
H4A—C4—H4B | 109.5 | H82A—C82—H82C | 109.5 |
C3—C4—H4C | 109.5 | H82B—C82—H82C | 109.5 |
H4A—C4—H4C | 109.5 |
Symmetry codes: (i) −x+3/2, y+1/2, −z+1/2; (ii) −x+3/2, y−1/2, −z+1/2; (iii) −x+1, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | [Co(C4H7O2)2(H2O)]·0.7H2O |
Mr | 263.75 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 210 |
a, b, c (Å) | 14.8377 (13), 6.2597 (7), 25.743 (3) |
β (°) | 104.900 (3) |
V (Å3) | 2310.6 (4) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 1.49 |
Crystal size (mm) | 0.10 × 0.08 × 0.03 |
Data collection | |
Diffractometer | Bruker APEXII CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2007) |
Tmin, Tmax | 0.301, 0.351 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12584, 2731, 1752 |
Rint | 0.096 |
(sin θ/λ)max (Å−1) | 0.654 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.096, 0.82 |
No. of reflections | 2731 |
No. of parameters | 156 |
No. of restraints | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.62, −0.58 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2008), publCIF (Westrip, 2010).
Co1—O3 | 2.027 (2) | Co1—O4i | 2.105 (2) |
Co1—O5 | 2.049 (2) | Co1—O2 | 2.163 (2) |
Co1—O4 | 2.074 (2) | Co1—O2ii | 2.217 (2) |
Symmetry codes: (i) −x+3/2, y+1/2, −z+1/2; (ii) −x+3/2, y−1/2, −z+1/2. |
Footnotes
‡Additional correspondence author, e-mail: vladgeo17@mail.ru.
References
Brandenburg, K. (2008). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Bruker, (2007). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker, (2009). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Eremenko, I. L., Sidorov, A. A. & Kiskin, M. A. (2009). Magnetic nanoparticles, edited by S. P. Gubin, pp. 349–391. Weinheim: Wiley-VCH. Google Scholar
Fischer, A. I., Gurzhiy, V. V. & Belyaev, A. N. (2010). Acta Cryst. E66, m1498. Web of Science CSD CrossRef IUCr Journals Google Scholar
Gates, B. C. (1992). Catalytic Chemistry. New York: Wiley-Interscience. Google Scholar
Jiao, X.-D., Guzei, I. A. & Espenson, J. H. (2000). Z. Kristallogr. New Cryst. Struct. 215, 173–174. CAS Google Scholar
Parshall, G. W. & Ittel, S. D. (1992). Homogenous Catalysis. New York: Wiley-Interscience. Google Scholar
Partenheimer, W. (1995). Catal. Today, 23, 69–158. CrossRef CAS Web of Science Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
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Cobalt carboxylates are of great importance because of their application in homogeneous oxidation catalysis (Gates, 1992; Parshall & Ittel, 1992; Partenheimer, 1995), and their interesting magnetic properties (Eremenko et al., 2009). Recently, we have reported on the crystal structure of the polymeric cobalt(II) propionate dihydrate, which was prepared by the reaction of cobalt(II) carbonate hydrate with aqueous propionic acid (Fischer et al., 2010). We found that the use of butyric acid instead of propionic acid leads to an analogous product, {[Co(C3H7COO)2(H2O)].0.7H2O}n (I). This salt, named as cobalt(II) butyrate 1.7-hydrate, is interesting for us as a starting reagent for the preparation of the mixed-valence cobalt carboxylates.
The crystal structure of the title compound contains one independent Co2+ cation coordinated by four O atoms of four bridging butyrates and two O atoms of bridging water molecules in a severely distorted octahedral coordination (Fig. 1). The cis-angles about the Co atom range from 80.77 (9) to 106.47 (9)°, the Co—O bond lengths are in the range of 2.027 (2) – 2.217 (2) Å; this data correlates with the angles and the distances in cobalt(II) acetate dihydrate with similar structure (Jiao et al., 2000) as well as isostructural cobalt(II) propionate dihydrate (Fischer et al., 2010). The structure of the title compound features infinite chains with composition ∞[Co(C3H7COO)4/2(H2O)2/2] running along [010]. The Co···Co minimum distance in the chain is equal to 3.1436 (7) Å. The bridging butyrate groups adopt two coordination modes, monodentate and syn-syn bidentate. The bidentate group has C—O bonds of practically equal length, 1.253 (4) and 1.254 (4) Å, whereas monodentate group has different C—O bond lengths, 1.231 (4) and 1.293 (4) Å. The chains are connected to each other through O—H···O hydrogen bonds involving partially occupied disordered water molecules; as a result, the sheets parallel to the (001) plane are produced (Fig. 2). The O61 atom of disordered solvate water molecule occupies a special position on the twofold axis.