[μ-6,9-Bis(carboxylatomethyl)-3,12-bis(car­boxymethyl)-3,6,9,12-tetraaza­tetradecanedioato]bis­[aqua­cobalt(II)] tetra­hydrate

The binuclear title complex, [Co₂(C₁₈H₂₆N₄O₁₂)(H₂O)₂]·4H₂O, lies about a centre of inversion, the Co^II atom being coordinated in a distorted octa­hedral arrangement defined by one water mol­ecule and N₂O₃ donors derived from one end of a 6,9-bis(carboxylatomethyl)-3,12-bis(car­boxy­methyl)-3,6,9,12-tetraaza­tetradecanedioate (H₂TTHA⁴⁻) tetra­anion. In the crystal, numerous O—H...O hydrogen bonds link the mol­ecules into a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 292 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.053
• wR factor = 0.117
• Data-to-parameter ratio = 16.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      2.641
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          2
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          6

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ?
PLAT007_ALERT_5_G Note: Number of Unrefined D-H Atoms ............          8
PLAT793_ALERT_4_G The Model has Chirality at N2      (Verify) ....          R
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600         40

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   3 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   4 ALERT level G = General information/check it is not something unexpected

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

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S1. Comment

H₆TTHA (triethylenetetraminehexaacetic acid) is a multicarboxyl ligand with ten potential coordinating sites and plays an important role in the self-assembly of various functional materials (Xu et al., 2008; Ouyang et al., 2007). In an effort to explore new enzyme-mimics involved with cobalt(II) and poly-carboxyl-group ligands, we have synthesized and crystallized the title complex, [Co₂(H₂TTHA)(H₂O)₂].4H₂O, (I), in water under ambient conditions via the reaction of Co(OH)₂ and H₆TTHA. Herein, we report its crystal structure.

The asymmetric unit of (I) comprises half a neutral [Co₂(H₂TTHA)(H₂O)₂] binuclear unit and two solvent water molecules (Fig. 1). The binuclear [Co₂(H₂TTHA)(H₂O)₂] is centrosymmetric with the midpoint of the ethylene C—C bond on an inversion centre. Each Co^II ion has a distorted octahedral geometry and is bonded to two N atoms and three carboxylate-O atoms from half of the H₂TTHA^4- ligand, as well as a water molecule. The Co1—N1 and Co1—N2 bond lengths are 2.216 (3) and 2.134 (3) Å, respectively, and the Co—O bond lengths range from 2.031 (3) to 2.120 (3) Å which are similar to those in its analogous structure (Song et al., 2003)

Analysis indicates (Spek, 2009) that in the crystal packing there are extensive O—H···O hydrogen-bond interactions (Table 1) between the O atoms of the six carboxylate/carboxylic acid groups of the H₂TTHA^4- ligand and/or the water molecules, leading to a three-dimensional array (Fig. 2).

Related literature

For related coordination complexes of species derived from triethylenetetraminehexaacetic acid, see: Ouyang et al. (2007); Xu et al. (2008). For a related structure, see: Song et al. (2003).

S2. Experimental

A mixture of Co(OH)₂ (0.18 g, 2 mmol) and H₆TTHA (0.20 g, 0.5 mmol) was stirred in H₂O (30 ml) solution for 30 min at room temperature. The resulting solution was filtered and the clear solution was left standing for two weeks. Purple crystals of (I) suitable for X-ray diffraction were obtained at the bottom of the vessel.

S3. Refinement

C-bound H atoms were positioned geometrically (C—H = 0.97 Å) and refined with U_iso= 1.2U_eq(carrier atom). The carboxyl H1 and H5 atoms are each located close to a crystallographic inversion centre between pairs of symmetry equivalent atoms of O1 and O5. Both H atoms were thus refined as 50% occupied. The O—H distances were constrained to be 0.82 Å and U_iso= 1.5U_eq(O). Water H atoms were initially found in a difference map and refined with O—H = 0.82 Å and U_iso= 1.5U_eq(O). Several reflections, i.e. (0 0 1), (0 1 0), (2 0 0) and (-4 3 2), were omitted from the refinement owing to poor agreement.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structures of the components of (I) with displacement ellipsoids drawn at the 50% probability level. Unlabelled atoms are related by the symmetry operation: 2-x, 1-y, 1-z.
	Fig. 2. Part of the crystal structure of (I), showing the formation of a three-dimensional network by hydrogen bonds (dashed lines). Hydrogen atoms not involved in hydrogen bonding have been omitted for clarity.

[µ-6,9-Bis(carboxylatomethyl)-3,12-bis(carboxymethyl)-3,6,9,12- tetraazatetradecanedioato]bis[aquacobalt(II)] tetrahydrate

Crystal data

[Co2(C18H26N4O12)(H2O)2]·4H2O	Z = 1
Mr = 716.38	F(000) = 372
Triclinic, P1	Dx = 1.742 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.0972 (15) Å	Cell parameters from 1506 reflections
b = 8.7025 (19) Å	θ = 2.6–23.8°
c = 11.968 (3) Å	µ = 1.31 mm^−1
α = 104.238 (4)°	T = 292 K
β = 100.986 (3)°	Plate, violet
γ = 100.425 (4)°	0.10 × 0.08 × 0.05 mm
V = 682.9 (3) Å^3

Data collection

Bruker SMART APEX CCD diffractometer	3099 independent reflections
Radiation source: fine focus sealed Siemens Mo tube	2182 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.097
0.3° wide ω exposures scans	θmax = 27.5°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 2008)	h = −9→9
Tmin = 0.881, Tmax = 0.938	k = −11→11
8012 measured reflections	l = −15→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.117	H-atom parameters constrained
S = 0.94	w = 1/[σ^2(Fo^2) + (0.047P)^2] where P = (Fo^2 + 2Fc^2)/3
3099 reflections	(Δ/σ)max < 0.001
190 parameters	Δρmax = 0.61 e Å^−3
0 restraints	Δρmin = −0.53 e Å^−3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Co1	0.72982 (7)	0.71114 (6)	0.70687 (4)	0.02486 (17)
N1	0.9888 (4)	0.6394 (4)	0.6502 (2)	0.0260 (7)
N2	0.9015 (4)	0.9540 (4)	0.7434 (2)	0.0255 (7)
O1	1.0763 (4)	0.5057 (4)	0.9155 (2)	0.0457 (8)
H1	1.0240	0.5153	0.9715	0.069*	0.50
O2	0.8739 (4)	0.6544 (3)	0.8584 (2)	0.0306 (6)
O3	0.6757 (5)	0.9168 (4)	0.4387 (2)	0.0548 (9)
O4	0.6154 (4)	0.7492 (3)	0.5486 (2)	0.0308 (6)
O5	0.6500 (4)	1.0653 (3)	0.9745 (2)	0.0401 (7)
H5	0.5449	1.0184	0.9830	0.060*	0.50
O6	0.5890 (4)	0.8431 (3)	0.8222 (2)	0.0335 (6)
O7	0.5376 (4)	0.4898 (3)	0.6630 (2)	0.0416 (7)
H7A	0.5779	0.4274	0.6978	0.062*
H7B	0.5143	0.4317	0.5943	0.062*
C1	0.9172 (5)	0.5213 (5)	0.5288 (3)	0.0322 (9)
H1A	0.8342	0.5670	0.4781	0.039*
H1B	0.8362	0.4217	0.5334	0.039*
C2	1.0911 (6)	0.5704 (5)	0.7386 (3)	0.0395 (10)
H2A	1.2292	0.6286	0.7657	0.047*
H2B	1.0851	0.4570	0.7004	0.047*
C3	1.0033 (6)	0.5803 (5)	0.8454 (3)	0.0302 (9)
C4	1.1120 (6)	0.7947 (5)	0.6468 (3)	0.0313 (9)
H4A	1.0630	0.8154	0.5719	0.038*
H4B	1.2472	0.7852	0.6518	0.038*
C5	1.1076 (6)	0.9363 (5)	0.7487 (3)	0.0351 (10)
H5A	1.1622	0.9181	0.8237	0.042*
H5B	1.1887	1.0362	0.7446	0.042*
C6	0.8262 (6)	1.0170 (5)	0.6438 (3)	0.0362 (10)
H6A	0.9377	1.0745	0.6224	0.043*
H6B	0.7507	1.0950	0.6706	0.043*
C7	0.6972 (6)	0.8852 (5)	0.5344 (3)	0.0330 (9)
C8	0.8807 (6)	1.0525 (5)	0.8581 (3)	0.0310 (9)
H8A	0.8829	1.1632	0.8554	0.037*
H8B	0.9912	1.0565	0.9215	0.037*
C9	0.6896 (6)	0.9799 (5)	0.8838 (3)	0.0284 (8)
O8	0.5622 (5)	0.2722 (4)	0.7785 (3)	0.0729 (11)
H8C	0.5855	0.3176	0.8501	0.109*
H8D	0.4441	0.2302	0.7658	0.109*
O9	0.3797 (6)	0.3141 (5)	0.9602 (4)	0.1021 (15)
H9A	0.3722	0.2969	1.0237	0.153*
H9B	0.2845	0.3520	0.9418	0.153*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.0255 (3)	0.0292 (3)	0.0196 (3)	0.0075 (2)	0.0068 (2)	0.0049 (2)
N1	0.0287 (17)	0.0341 (18)	0.0182 (15)	0.0108 (14)	0.0098 (13)	0.0076 (13)
N2	0.0281 (17)	0.0298 (17)	0.0190 (15)	0.0065 (14)	0.0094 (13)	0.0057 (13)
O1	0.055 (2)	0.068 (2)	0.0344 (16)	0.0356 (17)	0.0201 (15)	0.0306 (16)
O2	0.0338 (15)	0.0446 (17)	0.0198 (13)	0.0194 (13)	0.0112 (12)	0.0102 (12)
O3	0.077 (2)	0.055 (2)	0.0289 (16)	0.0015 (17)	0.0066 (16)	0.0207 (15)
O4	0.0358 (16)	0.0321 (15)	0.0222 (13)	0.0067 (12)	0.0031 (12)	0.0077 (12)
O5	0.0412 (17)	0.0452 (18)	0.0286 (15)	0.0088 (14)	0.0185 (13)	−0.0050 (13)
O6	0.0301 (15)	0.0372 (16)	0.0306 (15)	0.0082 (13)	0.0126 (12)	0.0010 (13)
O7	0.0489 (18)	0.0369 (17)	0.0311 (16)	0.0011 (14)	0.0062 (14)	0.0051 (13)
C1	0.033 (2)	0.034 (2)	0.030 (2)	0.0091 (18)	0.0158 (18)	0.0037 (18)
C2	0.045 (3)	0.057 (3)	0.031 (2)	0.029 (2)	0.018 (2)	0.021 (2)
C3	0.031 (2)	0.037 (2)	0.0220 (19)	0.0077 (18)	0.0068 (17)	0.0078 (17)
C4	0.027 (2)	0.035 (2)	0.031 (2)	0.0057 (17)	0.0105 (17)	0.0063 (18)
C5	0.027 (2)	0.039 (2)	0.033 (2)	−0.0019 (18)	0.0085 (18)	0.0038 (19)
C6	0.051 (3)	0.032 (2)	0.026 (2)	0.0106 (19)	0.0110 (19)	0.0079 (18)
C7	0.036 (2)	0.041 (2)	0.025 (2)	0.0128 (19)	0.0092 (18)	0.0110 (18)
C8	0.036 (2)	0.032 (2)	0.0201 (19)	0.0051 (18)	0.0072 (17)	0.0009 (16)
C9	0.030 (2)	0.033 (2)	0.0223 (19)	0.0117 (18)	0.0046 (17)	0.0078 (17)
O8	0.073 (3)	0.077 (3)	0.064 (2)	0.005 (2)	0.010 (2)	0.027 (2)
O9	0.121 (4)	0.106 (4)	0.115 (4)	0.058 (3)	0.069 (3)	0.043 (3)

Geometric parameters (Å, º)

Co1—O7	2.031 (3)	C1—C1^i	1.527 (7)
Co1—O4	2.043 (2)	C1—H1A	0.9700
Co1—O6	2.094 (2)	C1—H1B	0.9700
Co1—O2	2.120 (2)	C2—C3	1.516 (5)
Co1—N2	2.134 (3)	C2—H2A	0.9700
Co1—N1	2.216 (3)	C2—H2B	0.9700
N1—C2	1.477 (4)	C4—C5	1.515 (5)
N1—C4	1.486 (4)	C4—H4A	0.9700
N1—C1	1.490 (4)	C4—H4B	0.9700
N2—C8	1.478 (4)	C5—H5A	0.9700
N2—C6	1.480 (4)	C5—H5B	0.9700
N2—C5	1.490 (5)	C6—C7	1.514 (5)
O1—C3	1.272 (4)	C6—H6A	0.9700
O1—H1	0.8200	C6—H6B	0.9700
O2—C3	1.226 (4)	C8—C9	1.509 (5)
O3—C7	1.230 (4)	C8—H8A	0.9700
O4—C7	1.286 (4)	C8—H8B	0.9700
O5—C9	1.267 (4)	O8—H8D	0.8200
O5—H5	0.8200	O8—H8C	0.8200
O6—C9	1.237 (4)	O8—H8D	0.8200
O7—H7A	0.8201	O9—H9A	0.8200
O7—H7B	0.8200	O9—H9B	0.8200
O7—Co1—O4	92.28 (11)	N1—C2—H2A	108.9
O7—Co1—O6	97.80 (11)	C3—C2—H2A	108.9
O4—Co1—O6	102.38 (10)	N1—C2—H2B	108.9
O7—Co1—O2	87.25 (11)	C3—C2—H2B	108.9
O4—Co1—O2	172.02 (10)	H2A—C2—H2B	107.7
O6—Co1—O2	85.56 (10)	O2—C3—O1	125.6 (3)
O7—Co1—N2	172.89 (11)	O2—C3—C2	120.8 (3)
O4—Co1—N2	82.40 (11)	O1—C3—C2	113.6 (3)
O6—Co1—N2	78.85 (11)	N1—C4—C5	111.0 (3)
O2—Co1—N2	98.68 (11)	N1—C4—H4A	109.4
O7—Co1—N1	100.97 (11)	C5—C4—H4A	109.4
O4—Co1—N1	93.72 (10)	N1—C4—H4B	109.4
O6—Co1—N1	154.68 (11)	C5—C4—H4B	109.4
O2—Co1—N1	78.57 (10)	H4A—C4—H4B	108.0
N2—Co1—N1	84.15 (11)	N2—C5—C4	110.7 (3)
C2—N1—C4	112.2 (3)	N2—C5—H5A	109.5
C2—N1—C1	112.8 (3)	C4—C5—H5A	109.5
C4—N1—C1	110.5 (3)	N2—C5—H5B	109.5
C2—N1—Co1	108.9 (2)	C4—C5—H5B	109.5
C4—N1—Co1	103.8 (2)	H5A—C5—H5B	108.1
C1—N1—Co1	108.1 (2)	N2—C6—C7	113.7 (3)
C8—N2—C6	111.9 (3)	N2—C6—H6A	108.8
C8—N2—C5	112.3 (3)	C7—C6—H6A	108.8
C6—N2—C5	111.7 (3)	N2—C6—H6B	108.8
C8—N2—Co1	108.2 (2)	C7—C6—H6B	108.8
C6—N2—Co1	107.5 (2)	H6A—C6—H6B	107.7
C5—N2—Co1	104.7 (2)	O3—C7—O4	124.8 (4)
C3—O1—H1	109.5	O3—C7—C6	117.7 (4)
C3—O2—Co1	116.4 (2)	O4—C7—C6	117.5 (3)
C7—O4—Co1	115.5 (2)	N2—C8—C9	110.6 (3)
C9—O5—H5	109.5	N2—C8—H8A	109.5
C9—O6—Co1	114.6 (2)	C9—C8—H8A	109.5
Co1—O7—H7A	113.6	N2—C8—H8B	109.5
Co1—O7—H7B	117.3	C9—C8—H8B	109.5
H7A—O7—H7B	99.1	H8A—C8—H8B	108.1
N1—C1—C1^i	113.9 (4)	O6—C9—O5	124.5 (4)
N1—C1—H1A	108.8	O6—C9—C8	120.5 (3)
C1^i—C1—H1A	108.8	O5—C9—C8	114.9 (3)
N1—C1—H1B	108.8	H8D—O8—H8C	99.3
C1^i—C1—H1B	108.8	H8C—O8—H8D	99.3
H1A—C1—H1B	107.7	H9A—O9—H9B	104.7
N1—C2—C3	113.2 (3)
O7—Co1—N1—C2	−76.1 (3)	O4—Co1—O6—C9	−99.2 (3)
O4—Co1—N1—C2	−169.1 (2)	O2—Co1—O6—C9	80.1 (3)
O6—Co1—N1—C2	61.1 (4)	N2—Co1—O6—C9	−19.6 (3)
O2—Co1—N1—C2	8.8 (2)	N1—Co1—O6—C9	29.1 (4)
N2—Co1—N1—C2	108.9 (3)	C2—N1—C1—C1^i	−67.4 (5)
O7—Co1—N1—C4	164.2 (2)	C4—N1—C1—C1^i	59.1 (5)
O4—Co1—N1—C4	71.1 (2)	Co1—N1—C1—C1^i	172.2 (4)
O6—Co1—N1—C4	−58.6 (3)	C4—N1—C2—C3	109.8 (4)
O2—Co1—N1—C4	−110.9 (2)	C1—N1—C2—C3	−124.6 (3)
N2—Co1—N1—C4	−10.8 (2)	Co1—N1—C2—C3	−4.6 (4)
O7—Co1—N1—C1	46.8 (2)	Co1—O2—C3—O1	−164.1 (3)
O4—Co1—N1—C1	−46.3 (2)	Co1—O2—C3—C2	15.6 (5)
O6—Co1—N1—C1	−176.0 (2)	N1—C2—C3—O2	−6.9 (5)
O2—Co1—N1—C1	131.7 (2)	N1—C2—C3—O1	172.8 (3)
N2—Co1—N1—C1	−128.2 (2)	C2—N1—C4—C5	−79.2 (4)
O4—Co1—N2—C8	127.7 (2)	C1—N1—C4—C5	154.0 (3)
O6—Co1—N2—C8	23.4 (2)	Co1—N1—C4—C5	38.2 (3)
O2—Co1—N2—C8	−60.3 (2)	C8—N2—C5—C4	161.8 (3)
N1—Co1—N2—C8	−137.7 (2)	C6—N2—C5—C4	−71.5 (4)
O4—Co1—N2—C6	6.6 (2)	Co1—N2—C5—C4	44.6 (3)
O6—Co1—N2—C6	−97.7 (2)	N1—C4—C5—N2	−59.1 (4)
O2—Co1—N2—C6	178.6 (2)	C8—N2—C6—C7	−134.5 (3)
N1—Co1—N2—C6	101.2 (2)	C5—N2—C6—C7	98.6 (4)
O4—Co1—N2—C5	−112.3 (2)	Co1—N2—C6—C7	−15.7 (4)
O6—Co1—N2—C5	143.4 (2)	Co1—O4—C7—O3	165.6 (3)
O2—Co1—N2—C5	59.7 (2)	Co1—O4—C7—C6	−15.6 (4)
N1—Co1—N2—C5	−17.8 (2)	N2—C6—C7—O3	−159.4 (4)
O7—Co1—O2—C3	88.1 (3)	N2—C6—C7—O4	21.6 (5)
O6—Co1—O2—C3	−173.8 (3)	C6—N2—C8—C9	93.7 (4)
N2—Co1—O2—C3	−95.8 (3)	C5—N2—C8—C9	−139.8 (3)
N1—Co1—O2—C3	−13.7 (3)	Co1—N2—C8—C9	−24.7 (3)
O7—Co1—O4—C7	−179.9 (3)	Co1—O6—C9—O5	−165.2 (3)
O6—Co1—O4—C7	81.6 (3)	Co1—O6—C9—C8	10.9 (4)
N2—Co1—O4—C7	4.8 (3)	N2—C8—C9—O6	10.2 (5)
N1—Co1—O4—C7	−78.8 (3)	N2—C8—C9—O5	−173.3 (3)
O7—Co1—O6—C9	166.7 (3)

Symmetry code: (i) −x+2, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O1^ii	0.82	1.68	2.483 (5)	168
O5—H5···O5^iii	0.82	1.67	2.481 (5)	170
O7—H7A···O8	0.82	1.84	2.616 (4)	157
O7—H7B···O4^iv	0.82	1.95	2.732 (4)	159
O8—H8D···O3^iv	0.82	2.37	2.745 (5)	109
O8—H8C···O9	0.82	2.15	2.719 (5)	127
O9—H9A···O2^v	0.82	2.48	3.067 (4)	130
O9—H9A···O6^v	0.82	2.45	3.217 (5)	157

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