Poly[[tetra­aqua­(μ₆-benzene-1,2,4,5-tetra­carboxyl­ato)dicobalt(II)] dihydrate]

The asymmetric unit of the title coordination polymer, {[Co₂(C₁₀H₂O₈)(H₂O)₄]·2H₂O}_n, contains two crystallographically distinct Co^II cations, located on inversion centers. Each Co^II cation exists in an octa­hedral coordination environment formed by two water mol­ecules and four carboxyl­ate groups. The deprotonated benzene-1,2,4,5-tetra­carboxylic acid ligand, with the center of the benzene ring located on an inversion center, bridges Co^II cations to form a (3,4)-connected three-dimensional network that is topologically related to Pt₃O₄ (waserite). O—H...O hydrogen bonding between coordinated water mol­ecules and carboxylate groups helps to stabilize the crystal structure. One water molecules is disordered over two positions, with almost equal occupancies.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.004 Å
• H-atom completeness 72%
• Disorder in main residue
• R factor = 0.038
• wR factor = 0.103
• Data-to-parameter ratio = 14.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.97
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT301_ALERT_3_C Main Residue  Disorder .........................       1.00 Perc.
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....      >O31A
PLAT311_ALERT_2_C Isolated Disordered Oxygen Atom (No H's ?) .....      <O31B

Alert level G
FORMU01_ALERT_2_G  There is a discrepancy between the atom counts in the
            _chemical_formula_sum and the formula from the _atom_site* data.
            Atom count from _chemical_formula_sum:C5 H7 Co1 O7
            Atom count from the _atom_site data:  C5 H5 Co1 O7
CELLZ01_ALERT_1_G Difference between formula and atom_site contents detected.
CELLZ01_ALERT_1_G WARNING: H atoms missing from atom site list. Is this intentional?
           From the CIF: _cell_formula_units_Z    2
           From the CIF: _chemical_formula_sum  C5 H7 Co O7
           TEST: Compare cell contents of formula and atom_site data

           atom    Z*formula  cif sites diff
           C         10.00     10.00    0.00
           H         14.00     10.00    4.00
           Co         2.00      2.00    0.00
           O         14.00     14.00    0.00

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   7 ALERT level C = Check and explain
   3 ALERT level G = General alerts; check

   5 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

As shown in figure 1, a half of the Benzene-1,2,4,5-tetracarboxylic acid (H₄btec) is observed in the crystallographic asymmetric unit with center of the benzene ring located on a crystallographic 1 position. The observation of symmetrical C?O bond lengths ranges from 1.250 (2) to 1.265 (3) Å indicates that all of the carboxyl groups of the H₄btec are deprotonated to become the btec^4- anion. The asymmetric unit of the title compound contains two crystallographic distinct Co^II cations, located on crystallographic inversion centers with site occupation factor of 0.5. Each Co ion exists in an octahedral coordination environment (Table 1) formed by two water molecules and four carboxylate groups. The btec^4- ligands bridges Co ions to form a three-dimensional metal-organic framework with one-dimensional channels in the [010] direction that are occupied by disordered guest water molecules and coordinated water molecules (Fig. 2). The formula of the compound is assigned to be [Co₂(C₁₀H₂O₈)(H₂O)₄.2H₂O]_n. A Ni^II analogue, and a Co^II-btec coordination polymer with different contents of unit-cell packing were previously reported (Yang et al., 2003; Kumagai et al., 2002).

The network topology of the title compound is analyzed. The carbon atom of the carboxylate group serves as a simple three-connected node linking benzene ring and two Co ions. The benzene ring of the Benzene-1,2,4,5-tetracarboxylate ligand serves as a planar four-connected node. If coordinated water molecules are neglected, each Co ion also serves as a planar four-connected secondary building unit on the basis of four coordinated carboxylate groups. As a result, the title compound represents a new example of a (3,4)-connected net that is topologically related to Pt₃O₄ (waserite) (O'Keeffe et al., 2000; Wells, 1977).

The O—H···O hydroge bonding between coordinated water molecules and carboxyl groups helps to stabilize the crystal structure (Table 2).

Related literature

For related structures, see: Kumagai et al. (2002); O'Keeffe et al. (2000); Wells (1977); Yang et al. (2003).

S2. Experimental

All reagents and solvents were used as obtained without further purification. CoCl₂.6H₂O (0.6 mmol), H₄btec (0.5 mmol) and NaOH (1.0 mmol) were dissolved in 8 ml of distilled water. The mixture was sealed in a Teflon-lined stainless steel vessel and held at 383 K for 72 h. The vessel was gradually cooled to room temperature, and red crystals suitable for crystallographic analysis were obtained after 4 d.

S3. Refinement

The C-bound H atoms were placed in calculated positions (C—H = 0.93 Å) and refined in the riding-model approximation with U_iso(H) = 1.2U_eq(C). The H atoms of the coordinated water molecules were located in a difference Fourier map, and refined as riding model with O—H distances range from 0.82 to 0.85 Å, and with U_iso(H) = 1.5U_eq(O). The PLATON SQUEEZE procedure was used to treat regions of disordered guest molecules that could not be judiciously modeled in terms of atomic sites (Spek, 2003). The number of electrons thus located, 17 per unit cell, is assigned to two molecules of water solvent and is included in the formula, formula weight, calculated density, µ and F(000). There is difference between the reported and calculated values. Two largest residual densities located from the difference Fourier map separated by 1.93 Å are assigned to two disordered guest water molecules O31A and O31B. The refinement of relative site occupation factor leads to 0.53 and 0.47 for O31A and O31B, respectively. No attempt was made to locate hydrogen atoms of the disordered guest water molecules.

Computing details

Data collection: XSCANS (Bruker, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997) and PLATON (Spek, 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The asymmetric unit, expanded to show the complete coordination of the Co ions, with displacement ellipsoids drawn at the 50% probability level. Guest water molecules are omitted for clarity. (Symmetry codes are the same as geometric tables.)
	Fig. 2. Solid-state packing diagram of the three-dimensional framework.
	Fig. 3. Topological view of the Pt3O4 related (3,4)-connected net of the titel compound. (black sphere: C atom of carboxylate group; white sphere: center of btec^4- ligand; grey sphere: Co ion.)

Poly[[tetraaqua(µ₆-benzene-1,2,4,5-tetracarboxylato)dicobalt(II)] dihydrate]

Crystal data

[Co2(C10H2O8)(H2O)4]·2H2O	Z = 2
Mr = 238.04	F(000) = 240
Triclinic, P1	Dx = 1.966 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.9362 (7) Å	Cell parameters from 34 reflections
b = 7.4559 (6) Å	θ = 5.6–12.8°
c = 8.2797 (7) Å	µ = 2.14 mm^−1
α = 90.342 (8)°	T = 298 K
β = 109.848 (7)°	Column, red
γ = 93.161 (7)°	0.3 × 0.1 × 0.1 mm
V = 402.00 (6) Å^3

Data collection

Bruker P4 diffractometer	1570 reflections with I > 2σ(I)
Radiation source: sealed tube	Rint = 0.028
Graphite monochromator	θmax = 28.0°, θmin = 2.6°
2θ/ω scans	h = −9→1
Absorption correction: ψ scan (North et al., 1968)	k = −9→9
Tmin = 0.685, Tmax = 0.811	l = −10→10
2314 measured reflections	3 standard reflections every 24 reflections
1883 independent reflections	intensity decay: 1.0%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.038	w = 1/[σ^2(Fo^2) + (0.0533P)^2 + 0.4406P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.103	(Δ/σ)max < 0.001
S = 1.05	Δρmax = 0.59 e Å^−3
1883 reflections	Δρmin = −0.77 e Å^−3
131 parameters

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Co1	0	0	0.5	0.01624 (16)
Co2	0.5	0.5	0.5	0.01426 (16)
O1	0.1694 (3)	0.2325 (3)	0.6119 (3)	0.0223 (4)
O2	0.4875 (3)	0.3576 (3)	0.7123 (3)	0.0227 (4)
O3	0.2645 (3)	−0.1283 (3)	0.5378 (3)	0.0268 (5)
O4	0.5570 (3)	−0.2620 (3)	0.6499 (2)	0.0175 (4)
O21	0.0391 (4)	0.0928 (4)	0.2669 (3)	0.0342 (6)
H21A	0.151	0.1538	0.2826	0.051*
H21B	−0.0337	0.0886	0.1656	0.051*
O22	0.1793 (3)	0.5155 (3)	0.3953 (3)	0.0265 (5)
H22A	0.1224	0.6092	0.404	0.04*
H22B	0.1421	0.4397	0.4559	0.04*
O31A	−0.0980 (8)	0.2254 (8)	−0.0766 (7)	0.0469 (18)	0.527 (8)
O31B	−0.1415 (13)	0.4510 (14)	0.0178 (11)	0.089 (4)	0.473 (8)
C1	0.3523 (4)	0.2411 (4)	0.7155 (3)	0.0155 (5)
C2	0.4193 (4)	0.1081 (4)	0.8574 (3)	0.0150 (5)
C3	0.4640 (4)	−0.0677 (4)	0.8333 (3)	0.0136 (5)
C4	0.4246 (4)	−0.1563 (4)	0.6596 (3)	0.0145 (5)
C5	0.4549 (4)	0.1741 (4)	1.0238 (3)	0.0163 (5)
H5A	0.4241	0.2912	1.0399	0.02*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.0143 (3)	0.0151 (3)	0.0165 (3)	0.00031 (19)	0.0018 (2)	−0.00175 (19)
Co2	0.0178 (3)	0.0117 (3)	0.0122 (2)	−0.00056 (19)	0.00392 (19)	−0.00044 (18)
O1	0.0210 (10)	0.0161 (10)	0.0224 (10)	−0.0007 (8)	−0.0018 (8)	0.0031 (8)
O2	0.0236 (11)	0.0234 (11)	0.0181 (9)	−0.0065 (8)	0.0042 (8)	0.0048 (8)
O3	0.0238 (11)	0.0343 (13)	0.0170 (10)	0.0117 (9)	−0.0015 (8)	−0.0091 (9)
O4	0.0177 (9)	0.0163 (9)	0.0170 (9)	0.0033 (7)	0.0035 (8)	−0.0042 (7)
O21	0.0222 (11)	0.0541 (16)	0.0214 (11)	−0.0087 (11)	0.0028 (9)	0.0053 (10)
O22	0.0219 (10)	0.0225 (11)	0.0346 (12)	0.0025 (9)	0.0088 (9)	−0.0006 (9)
O31A	0.038 (3)	0.059 (4)	0.040 (3)	−0.001 (3)	0.009 (2)	0.004 (3)
O31B	0.068 (6)	0.092 (7)	0.067 (5)	−0.026 (5)	−0.023 (4)	0.007 (5)
C1	0.0210 (13)	0.0127 (12)	0.0120 (11)	0.0002 (10)	0.0048 (10)	−0.0032 (9)
C2	0.0143 (12)	0.0158 (12)	0.0127 (11)	−0.0026 (10)	0.0025 (10)	−0.0019 (9)
C3	0.0140 (12)	0.0147 (12)	0.0107 (11)	−0.0023 (9)	0.0032 (9)	−0.0035 (9)
C4	0.0174 (12)	0.0129 (12)	0.0130 (11)	−0.0008 (10)	0.0052 (10)	−0.0026 (9)
C5	0.0201 (13)	0.0131 (12)	0.0158 (12)	0.0007 (10)	0.0062 (10)	−0.0018 (9)

Geometric parameters (Å, º)

Co1—O1	2.065 (2)	O3—C4	1.250 (3)
Co1—O1^i	2.065 (2)	O4—C4	1.264 (3)
Co1—O3^i	2.046 (2)	O4—Co2^v	2.0996 (19)
Co1—O3	2.046 (2)	O21—H21A	0.8472
Co1—O21	2.151 (2)	O21—H21B	0.8188
Co1—O21^i	2.151 (2)	O22—H22A	0.8359
Co2—O2^ii	2.083 (2)	O22—H22B	0.8447
Co2—O2	2.083 (2)	C1—C2	1.508 (4)
Co2—O4^iii	2.0996 (19)	C2—C3	1.392 (4)
Co2—O4^iv	2.0996 (19)	C2—C5	1.395 (3)
Co2—O22	2.105 (2)	C3—C5^vi	1.398 (4)
Co2—O22^ii	2.105 (2)	C3—C4	1.511 (3)
O1—C1	1.265 (3)	C5—C3^vi	1.398 (4)
O2—C1	1.250 (3)	C5—H5A	0.93
O3^i—Co1—O3	180.00 (12)	O4^iv—Co2—O22^ii	96.15 (8)
O3^i—Co1—O1	89.65 (9)	O22—Co2—O22^ii	180.0000 (10)
O3—Co1—O1	90.35 (9)	C1—O1—Co1	125.58 (19)
O3^i—Co1—O1^i	90.35 (9)	C1—O2—Co2	126.83 (18)
O3—Co1—O1^i	89.65 (9)	C4—O3—Co1	137.74 (18)
O1—Co1—O1^i	180	C4—O4—Co2^v	126.45 (17)
O3^i—Co1—O21	94.40 (10)	Co1—O21—H21A	113.9
O3—Co1—O21	85.60 (10)	Co1—O21—H21B	134.3
O1—Co1—O21	85.35 (9)	H21A—O21—H21B	111.6
O1^i—Co1—O21	94.65 (9)	Co2—O22—H22A	121.8
O3^i—Co1—O21^i	85.60 (10)	Co2—O22—H22B	99.9
O3—Co1—O21^i	94.40 (10)	H22A—O22—H22B	105.4
O1—Co1—O21^i	94.65 (9)	O2—C1—O1	124.3 (3)
O1^i—Co1—O21^i	85.35 (9)	O2—C1—C2	115.2 (2)
O21—Co1—O21^i	180.0000 (10)	O1—C1—C2	120.4 (2)
O2^ii—Co2—O2	180.0000 (10)	C3—C2—C5	119.3 (2)
O2^ii—Co2—O4^iii	91.12 (8)	C3—C2—C1	124.0 (2)
O2—Co2—O4^iii	88.88 (8)	C5—C2—C1	116.4 (2)
O2^ii—Co2—O4^iv	88.88 (8)	C2—C3—C5^vi	119.4 (2)
O2—Co2—O4^iv	91.12 (8)	C2—C3—C4	124.2 (2)
O4^iii—Co2—O4^iv	180	C5^vi—C3—C4	116.4 (2)
O2^ii—Co2—O22	86.24 (9)	O3—C4—O4	123.9 (2)
O2—Co2—O22	93.76 (9)	O3—C4—C3	119.9 (2)
O4^iii—Co2—O22	96.15 (8)	O4—C4—C3	116.1 (2)
O4^iv—Co2—O22	83.85 (8)	C2—C5—C3^vi	121.4 (2)
O2^ii—Co2—O22^ii	93.76 (9)	C2—C5—H5A	119.3
O2—Co2—O22^ii	86.24 (9)	C3^vi—C5—H5A	119.3
O4^iii—Co2—O22^ii	83.85 (8)

Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1, −y+1, −z+1; (iii) x, y+1, z; (iv) −x+1, −y, −z+1; (v) x, y−1, z; (vi) −x+1, −y, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O21—H21A···O4^iv	0.85	2.03	2.864 (3)	169
O21—H21B···O31A	0.82	2.17	2.876 (6)	144
O22—H22A···O3^iii	0.84	2.25	2.848 (3)	129
O22—H22B···O1	0.84	1.99	2.790 (3)	157

Symmetry codes: (iii) x, y+1, z; (iv) −x+1, −y, −z+1.