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The crystal structure of the first acesulfame-metal complex, namely tetra­aqua­bis­[6-methyl-1,2,3-oxa­thia­zin-4(3H)-onato 2,2-dioxide-[kappa]N]­cobalt(II), [Co(C4H4NO4S)2(H2O)4], is re­ported. The CoII ion resides on a twofold axis and is coordinated by four aqua ligands defining the basal plane and by two monodentate acesulfamate ligands, via their ring N atoms, in the axial positions. Two intra- and three intermolecular hydrogen-bonding interactions stabilize the crystal structure and form an infinite three-dimensional lattice.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104028574/sk1780sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104028574/sk1780Isup2.hkl
Contains datablock I

CCDC reference: 263019

Comment top

Acesulfame (C4H5SO4N) is an oxathiazinone dioxide and systematically named as 6-methyl-1,2,3-oxathiazin-4(3H)-one 2,2-dioxide; it is also known as 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide or acetosulfam. It has been widely used as non-calorific artificial sweetener since 1988, after the FDA (US Food and Drug Administration) granted approval (Duffy & Anderson, 1998). Acesulfame was discovered by the chemist Karl Clauss in 1967 (Clauss & Jensen, 1973). Many countries have approved the use of acesulfame-K in soft drinks, candies, toothpastes, mouthwashes, cosmetics and pharmacological preparations (Mukherjee & Chakrabarti, 1997). Chemically, it bears some structural resemblance to saccharin (see scheme). \sch

The acesulfame anion, C4H4NO4S, has several potential donor atoms and thus, as a polyfunctional ligand, it can engage in N, OCO, OOSO or O coordination with different metal ions,similar to the saccharinate ligand. The chemistry of metal-artificial sweetener complexes is an interesting area of research because of the potential biological significance of such compounds; the structural literature on metal saccharinates reveals a large number of coordinated saccharinate residues (Haider et al., 1985; Icbudak et al., 2002, 2003; Naumov et al., 2001; Deng et al. 2001; Quinzani et al., 2002; Yilmaz et al. 2004). The present work describes the crystal structure of the title compound, trans-bis(acesulfamato)tetraaquacobalt(II), (I). This complex is the first reported example of a complex containing the acesulfamate ligand among several new complexes synthesized in this laboratory.

A view of the molecule of (I) and its atom-numbering scheme are shown in Fig. 1. In the structure, the CoII ion resides on a crystallographic inversion centre, coordinated by four aqua ligands defining the basal plane and by two monodentate acesulfamate ligands, through their ring N atoms, occupying the axial positions. The acesulfamate ligands in the structure are mutually trans, with their sulfonyl groups trans to each other. The bond lengths and angles of the metal-bonded acesulfamate ligands show some differences from the analogous potassium salt (Paulus, 1975). The most pronounced of these is the S1—N1—C1 bond angle, which is reduced to 117.13 (15)° [117.65 (16) in CIF table] in (I), from the corresponding value of 122.9 (2)° in the potassim salt. This obviously originates from the metal coordination of the N atom of the acesulfamate ligand. A significant deviation of −0.2430 (10) Å for atom S1 from the least-squares plane of the acesulfame ring (N1/C1—C3/O2/S1) is also observed.

From inspection of the metal-ligand bond distances in Table 1, it can be seen that the Co—N bond is longer than the Co—O bond, indicating that the Co—N bond is not very strong. This is to be expected if one considers the delocalization of negative charge away from the N atom in the ring. The negative charge is mainly localized on the sulfonyl and ring O atoms, if one compares the N1—S1 [1.5887 (18) Å] and S1—O2 [1.5987 (18) Å] bond distances with the corresponding values (1.544 and 1.624 Å, respectively) found in the potassium acesulfame salt.

The local structure around the CoII ion in (I), [Co(acs)2(H2O)4], can be compared with that in [Co(sac)2(H2O)4]·2H2O (Haider et al., 1983), since both ligands have a structural resemblance, as shown in the scheme. Thus, one can conclude that the Co—Nacs distance of 2.3180 (19) Å in (I) is longer than the corresponding distance of 2.200 (1) Å in [Co(sac)2(H2O)4]·2H2O, while the two Co—Oaqua distances of 2.0338 (19) and 2.0567 (18) Å in (I) are shorter than the Co—Oaqua bond lengths of 2.060 (1) and 2.124 (2) Å, respectively, in [Co(sac)2(H2O)4]·2H2O. The angular distortions of the octahedral environment of the CoII ion in (I) also show some differences from those in the [Co(sac)2(H2O)4]·2H2O complex. The maximum deviation from an ideal O—M—O/N angle of 90° is 8.74 (9)° for (I), while it is only 2.8° for the saccharine complex.

With regard to the ligand geometry, the C—O bond length of the carbonyl group is increased by 0.012 Å in (I) compared with the potassium salt, whereas no significant changes are observed for the sulfonyl group. The bond lengths of these groups are especially important for IR studies, from which the coordination behaviour of the ligand (Grupce et al., 2001; Naumov et al., 2001) can be estimated.

The H atoms of the H2O ligands are involved in the both intra- and intermolecular hydrogen bonding with the carbonyl and sulfonyl O atoms of the acs ligand. The intramolecular O6—H6A.·O1 and O5—H5B.·O4(x + 1/2, y − 1/2, z) hydrogen bonds have H—O distances of 1.85 (4) and 2.38 (4) Å, respectively. These values indicate that the former interaction, between the H atom of one aqua ligand and the carbonyl O atom, is very strong when compared with that of the other aqua ligand H atom with the sulfonyl O atom. This is due to the fact that the carbonyl group is a more basic site than the sulfonyl group.

When the hydrogen-bond regime of the carbonyl O atom of (I) is compared with the same group of the cobalt-saccharin complex, it can be seen that they both have one intra- and one intermolecular hydrogen bond. Nevertheless, the O6—H6A.·O1 hydrogen bond [1.85 (4) Å] of the acesulfame complex is rather stronger than the corresponding bond in the saccharine complex (1.98 Å), while the O5—H5A—O1 hydrogen bond [1.935 (4) Å] is almost same as the corresponding bond in the saccharine complex (1.94 Å). This difference might originate from the difference in the chemical environments of the donors, where the both donors for the acesulfame complex are aqua ligands, while the donors are an aqua ligand and a solvate water molecule in the saccharine complex. There are also three intermolecular hydrogen-bonding interactions in the structure of (I), as given in Table 2, which stabilize the crystal structure and form an infinite three-dimensional lattice.

Experimental top

A solution of acesulfame potassium salt (0.41 g, 2 mmol) in distilled water (50 ml) was added dropwise with stirring to a hot solution of cobalt(II) perchlorate hexahydrate (0.37 g, 1 mmol) in ethanol (50 ml). The mixture was stirred at 353 K for 2 h and then evaporated to dryness in a temperature-controlled bath at 353 K. The complex which formed was separated from the KClO4 by extraction with absolute ethanol and was recrystallized from a solution in an ethanol-acetone mixture (1:1). The pink crystals which formed were filtered, washed with acetone and dried in vacuo.

Refinement top

The H atom on the ring C atom was placed in a calculated position with C—H = 0.93 Å and allowed to ride on its parent atom, with Uiso(H) = 1.2Ueq(C). The methyl H atoms were placed as an idealized methyl group with C—H = 0.96 Å, with torsion angles from the electron-density map, and were allowed to ride on the parent atom, with Uiso(H) = 1.5Ueq(C). Other H atoms were placed from the difference map and were included in the refinement, with O—H distances restrained to 0.82 (2) Å. Δρmax and Δρmin of 0.52 and −0.47 Å3 were found at distances of 0.94 and 0.86 Å from atoms O2 and Co1, respectively.

Computing details top

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 2002); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Burnett & Johnson, 1996); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. A view of the molecule of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry code: (i) 1 − x, y, 1/2 − z.]
[Figure 2] Fig. 2. A view of the structure of (I) along the b direction, with 10% probability displacement ellipsoids. Dashed lines illustrate the hydrogen bonds. Carbon-bound H atoms have been omitted for clarity.
tetraaquabis[6-methyl-1,2,3-oxathiazin-4(3H)-onato 2,2-dioxide-κN]cobalt(II) top
Crystal data top
[Co(C4H4NO4S)2(H2O)4]F(000) = 932
Mr = 455.28Dx = 1.877 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 9609 reflections
a = 13.2321 (14) Åθ = 2.8–25.9°
b = 8.9874 (6) ŵ = 1.39 mm1
c = 13.9519 (15) ÅT = 293 K
β = 103.854 (8)°Prismatic, pink
V = 1610.9 (3) Å30.37 × 0.25 × 0.19 mm
Z = 4
Data collection top
Stoe IPDS 2
diffractometer
1548 independent reflections
Radiation source: fine-focus sealed tube1249 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.072
Detector resolution: 6.67 pixels mm-1θmax = 25.8°, θmin = 2.8°
ω scansh = 1616
Absorption correction: integration
(X-RED32; Stoe & Cie, 2002)
k = 1010
Tmin = 0.516, Tmax = 0.736l = 1616
9404 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.028H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.068 w = 1/[σ2(Fo2) + (0.0411P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.95(Δ/σ)max < 0.001
1548 reflectionsΔρmax = 0.53 e Å3
132 parametersΔρmin = 0.47 e Å3
2 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0063 (5)
Crystal data top
[Co(C4H4NO4S)2(H2O)4]V = 1610.9 (3) Å3
Mr = 455.28Z = 4
Monoclinic, C2/cMo Kα radiation
a = 13.2321 (14) ŵ = 1.39 mm1
b = 8.9874 (6) ÅT = 293 K
c = 13.9519 (15) Å0.37 × 0.25 × 0.19 mm
β = 103.854 (8)°
Data collection top
Stoe IPDS 2
diffractometer
1548 independent reflections
Absorption correction: integration
(X-RED32; Stoe & Cie, 2002)
1249 reflections with I > 2σ(I)
Tmin = 0.516, Tmax = 0.736Rint = 0.072
9404 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0282 restraints
wR(F2) = 0.068H atoms treated by a mixture of independent and constrained refinement
S = 0.95Δρmax = 0.53 e Å3
1548 reflectionsΔρmin = 0.47 e Å3
132 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.35857 (17)0.0802 (2)0.02858 (16)0.0284 (5)
C20.26472 (18)0.0853 (3)0.05037 (17)0.0340 (5)
H20.26420.14710.10400.041*
C30.18027 (18)0.0078 (3)0.05076 (17)0.0322 (5)
C40.0832 (2)0.0008 (3)0.1292 (2)0.0470 (7)
H4A0.09040.06090.18410.070*
H4B0.02640.03740.10410.070*
H4C0.06980.10040.15040.070*
N10.35994 (14)0.0053 (2)0.11368 (14)0.0298 (4)
O10.43932 (12)0.14231 (19)0.01671 (12)0.0376 (4)
O20.17748 (13)0.0866 (2)0.02721 (13)0.0422 (4)
O30.26230 (14)0.1852 (2)0.18210 (15)0.0543 (5)
O40.20238 (15)0.0697 (2)0.17197 (15)0.0532 (5)
O50.55118 (14)0.1749 (2)0.17469 (13)0.0360 (4)
O60.57325 (17)0.1511 (2)0.18566 (17)0.0499 (5)
Co10.50000.00522 (5)0.25000.02744 (16)
S10.25144 (4)0.04628 (7)0.13242 (4)0.03036 (18)
H6A0.545 (3)0.155 (3)0.130 (2)0.052 (10)*
H6B0.632 (3)0.175 (4)0.196 (3)0.083 (13)*
H5A0.550 (3)0.164 (4)0.1185 (15)0.066 (11)*
H5B0.6028 (18)0.222 (3)0.201 (2)0.059 (10)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0266 (11)0.0330 (13)0.0255 (12)0.0006 (9)0.0062 (9)0.0009 (9)
C20.0330 (12)0.0443 (14)0.0235 (12)0.0015 (10)0.0047 (10)0.0048 (10)
C30.0305 (11)0.0374 (13)0.0265 (12)0.0007 (10)0.0025 (9)0.0014 (10)
C40.0334 (13)0.0621 (18)0.0383 (15)0.0077 (12)0.0054 (11)0.0014 (13)
N10.0228 (9)0.0407 (11)0.0243 (9)0.0051 (8)0.0021 (7)0.0032 (8)
O10.0281 (8)0.0569 (11)0.0280 (9)0.0092 (7)0.0071 (7)0.0057 (8)
O20.0342 (9)0.0520 (11)0.0350 (10)0.0149 (8)0.0024 (8)0.0051 (8)
O30.0369 (10)0.0553 (12)0.0626 (13)0.0136 (9)0.0041 (9)0.0280 (10)
O40.0426 (10)0.0657 (13)0.0576 (13)0.0033 (9)0.0246 (10)0.0145 (10)
O50.0349 (10)0.0491 (11)0.0251 (9)0.0079 (8)0.0095 (8)0.0002 (8)
O60.0366 (11)0.0641 (13)0.0411 (13)0.0201 (9)0.0063 (9)0.0170 (10)
Co10.0256 (2)0.0323 (3)0.0248 (2)0.0000.00681 (17)0.000
S10.0240 (3)0.0388 (3)0.0268 (3)0.0052 (2)0.0031 (2)0.0045 (2)
Geometric parameters (Å, º) top
C1—O11.251 (3)O2—S11.5987 (18)
C1—N11.361 (3)O3—S11.4188 (18)
C1—C21.450 (3)O4—S11.409 (2)
C2—C31.315 (3)O5—Co12.0567 (18)
C2—H20.9300O5—H5A0.787 (18)
C3—O21.387 (3)O5—H5B0.814 (18)
C3—C41.475 (3)O6—Co12.0338 (19)
C4—H4A0.9600O6—H6A0.78 (3)
C4—H4B0.9600O6—H6B0.79 (4)
C4—H4C0.9600Co1—O6i2.0338 (19)
N1—S11.5887 (18)Co1—O5i2.0567 (18)
N1—Co12.3180 (19)Co1—N1i2.3180 (19)
O1—C1—N1120.2 (2)Co1—O5—H5B120 (2)
O1—C1—C2119.2 (2)H5A—O5—H5B109 (3)
N1—C1—C2120.5 (2)Co1—O6—H6A108 (2)
C3—C2—C1124.0 (2)Co1—O6—H6B132 (3)
C3—C2—H2118.0H6A—O6—H6B113 (3)
C1—C2—H2118.0O6i—Co1—O692.60 (14)
C2—C3—O2120.2 (2)O6—Co1—O5i171.08 (8)
C2—C3—C4127.8 (2)O6—Co1—O592.12 (9)
O2—C3—C4111.9 (2)O5i—Co1—O584.25 (10)
C3—C4—H4A109.5O6—Co1—N1i87.83 (8)
C3—C4—H4B109.5O6—Co1—N188.95 (8)
H4A—C4—H4B109.5O5i—Co1—N198.80 (7)
C3—C4—H4C109.5O5—Co1—N184.69 (7)
H4A—C4—H4C109.5N1i—Co1—N1175.34 (9)
H4B—C4—H4C109.5O4—S1—O3117.54 (13)
C1—N1—S1117.65 (16)O4—S1—N1111.59 (11)
C1—N1—Co1125.22 (14)O3—S1—N1110.32 (11)
S1—N1—Co1115.44 (10)O4—S1—O2106.81 (12)
C3—O2—S1117.13 (15)O3—S1—O2102.54 (11)
Co1—O5—H5A119 (2)N1—S1—O2107.07 (10)
O1—C1—C2—C3170.7 (2)C1—N1—Co1—O5i167.11 (17)
N1—C1—C2—C37.5 (4)S1—N1—Co1—O5i28.11 (12)
C1—C2—C3—O20.4 (4)C1—N1—Co1—O583.78 (18)
C1—C2—C3—C4177.2 (2)S1—N1—Co1—O5111.44 (11)
O1—C1—N1—S1169.38 (17)C1—N1—S1—O482.58 (19)
C2—C1—N1—S112.4 (3)Co1—N1—S1—O483.40 (14)
O1—C1—N1—Co14.9 (3)C1—N1—S1—O3144.81 (18)
C2—C1—N1—Co1176.92 (16)Co1—N1—S1—O349.20 (15)
C2—C3—O2—S127.0 (3)C1—N1—S1—O233.96 (19)
C4—C3—O2—S1155.79 (18)Co1—N1—S1—O2160.05 (10)
C1—N1—Co1—O6i101.08 (18)C3—O2—S1—O478.07 (19)
S1—N1—Co1—O6i63.70 (12)C3—O2—S1—O3157.73 (17)
C1—N1—Co1—O68.44 (18)C3—O2—S1—N141.60 (19)
S1—N1—Co1—O6156.34 (12)
Symmetry code: (i) x+1, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H5A···O1ii0.79 (2)1.94 (2)2.719 (2)175 (4)
O5—H5B···O3i0.81 (3)2.14 (3)2.780 (3)136 (2)
O5—H5B···O4iii0.81 (3)2.38 (3)3.051 (3)141 (2)
O6—H6A···O10.78 (3)1.85 (4)2.589 (3)160 (4)
O6—H6B···O3iv0.79 (4)2.18 (4)2.913 (3)156 (4)
Symmetry codes: (i) x+1, y, z+1/2; (ii) x+1, y, z; (iii) x+1/2, y1/2, z; (iv) x+1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formula[Co(C4H4NO4S)2(H2O)4]
Mr455.28
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)13.2321 (14), 8.9874 (6), 13.9519 (15)
β (°) 103.854 (8)
V3)1610.9 (3)
Z4
Radiation typeMo Kα
µ (mm1)1.39
Crystal size (mm)0.37 × 0.25 × 0.19
Data collection
DiffractometerStoe IPDS 2
diffractometer
Absorption correctionIntegration
(X-RED32; Stoe & Cie, 2002)
Tmin, Tmax0.516, 0.736
No. of measured, independent and
observed [I > 2σ(I)] reflections
9404, 1548, 1249
Rint0.072
(sin θ/λ)max1)0.613
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.068, 0.95
No. of reflections1548
No. of parameters132
No. of restraints2
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.53, 0.47

Computer programs: X-AREA (Stoe & Cie, 2002), X-AREA, X-RED (Stoe & Cie, 2002), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Burnett & Johnson, 1996), WinGX (Farrugia, 1999).

Selected geometric parameters (Å, º) top
C1—O11.251 (3)O2—S11.5987 (18)
C1—N11.361 (3)O3—S11.4188 (18)
C1—C21.450 (3)O4—S11.409 (2)
C2—C31.315 (3)O5—Co12.0567 (18)
N1—S11.5887 (18)O6—Co12.0338 (19)
N1—Co12.3180 (19)
C1—N1—S1117.65 (16)O6—Co1—N1i87.83 (8)
O6i—Co1—O692.60 (14)O6—Co1—N188.95 (8)
O6—Co1—O592.12 (9)O5i—Co1—N198.80 (7)
O5i—Co1—O584.25 (10)O5—Co1—N184.69 (7)
Symmetry code: (i) x+1, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H5A···O1ii0.79 (2)1.94 (2)2.719 (2)175 (4)
O5—H5B···O3i0.81 (3)2.14 (3)2.780 (3)136 (2)
O5—H5B···O4iii0.81 (3)2.38 (3)3.051 (3)141 (2)
O6—H6A···O10.78 (3)1.85 (4)2.589 (3)160 (4)
O6—H6B···O3iv0.79 (4)2.18 (4)2.913 (3)156 (4)
Symmetry codes: (i) x+1, y, z+1/2; (ii) x+1, y, z; (iii) x+1/2, y1/2, z; (iv) x+1/2, y+1/2, z.
 

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