In contrast to former morphological studies, the results presented here show that calcium(II) thiosulfate hexahydrate, CaS
2O
3·6H
2O, crystallizes centrosymmetrically in the pinacoidal class (point group
). The structure is characterized by chains, parallel to [100], of alternating S
2O
3 and Ca(H
2O)
6O
2 groups sharing common O atoms. The composition of each chain link is [Ca(H
2O)
6(S
2O
3)]. The geometry is analysed and compared in detail with the structural features of monoclinic strontium(II) thiosulfate pentahydrate, SrS
2O
3·5H
2O, which forms layers, parallel to (100), of alternating S
2O
3 and Sr(H
2O)
4O
5 groups connected
via common O atoms and O–O edges. Each layer contains [Sr(H
2O)
3O(S
2O
3)]
∞ as the unique repeat unit.
Supporting information
The two title alkaline earth thiosulfates were synthesized in two different ways: (a) via reaction of (NH)2S2O3 with Ca(OH)2 [or Sr(OH)2·8H2O] in aqueous solution, and crystallization of the compounds by evaporation of the solvent at room temperature; (b) via reaction of concentrated aqueous solutions of Na2S2O3·5H2O and CaCl2·2H2O (or Sr(NO3)2), and crystallization of the compounds by evaporation of the solvent at room temperature. To increase the chemical purity of the crystals the crystallization was repeated. In both cases, crystals of up to several millimeters were obtained easily. Because the aqueous solutions tend to decompose, the growth of large single crystals suitable for measurements of physical properties is more difficult; to date, all growth experiments have failed. In contrast, crystals of CaS2O3·6H2O and SrS2O3·5H2O are stable for several weeks if they are kept in inert liquids (e.g. paraffin oil). The crystal morphologies of both kinds of crystals are shown in Fig. 1.
For CaS2O3·6H2O, refinement calculations were carried out in space groups P1 and P1. The results of the centrosymmetric setting showed significantly smaller residual factors (ΔR1 = −0.0019 and ΔwR2 = −0.0106), together with lower standard uncertainties of the atomic coordinates and distances (75–80% less). We tried to detect the piezoelectric effect in order to prove the absence of the centre of symmetry. However, measurements of several crystals were ambiguous because the method is sensitive to traces of surface decomposition products. The decomposition of the crystals in the laser beam prevented our attempts of SHG power test. For SrS2O3·5H2O, distance restraints were placed on the O4—H41, O6—H61, O6—H62, O7—H71, O7—H72, O8—H81 and O8—H82 [with a target value of 0.82 (5) Å].
For both compounds, data collection: MACH-3 Server Software (Enraf-Nonius, 1993); cell refinement: MACH-3 Server Software; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 2002) and ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97.
(I) calcium(II) thiosulfate hexahydrate
top
Crystal data top
CaS2O3·6H2O | Z = 2 |
Mr = 260.32 | F(000) = 272 |
Triclinic, P1 | Dx = 1.874 Mg m−3 |
a = 5.8204 (4) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 7.4391 (7) Å | Cell parameters from 25 reflections |
c = 11.2946 (8) Å | θ = 14.6–17.5° |
α = 72.537 (6)° | µ = 1.15 mm−1 |
β = 81.447 (6)° | T = 293 K |
γ = 87.282 (6)° | Parallelepiped, colourless |
V = 461.31 (7) Å3 | 0.27 × 0.25 × 0.23 mm |
Data collection top
Enraf–Nonius MACH-3 diffractometer | 2493 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed X-ray tube | Rint = 0.016 |
Graphite monochromator | θmax = 30.4°, θmin = 2.9° |
ω/2θ scans | h = −8→8 |
Absorption correction: ψ scan (MolEN; Fair, 1990) | k = −10→10 |
Tmin = 0.921, Tmax = 0.999 | l = −16→16 |
5584 measured reflections | 3 standard reflections every 60 min |
2794 independent reflections | intensity decay: 0.4% |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.019 | All H-atom parameters refined |
wR(F2) = 0.053 | w = 1/[σ2(Fo2) + (0.0286P)2 + 0.0904P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.001 |
2794 reflections | Δρmax = 0.42 e Å−3 |
158 parameters | Δρmin = −0.36 e Å−3 |
0 restraints | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.895 (13) |
Crystal data top
CaS2O3·6H2O | γ = 87.282 (6)° |
Mr = 260.32 | V = 461.31 (7) Å3 |
Triclinic, P1 | Z = 2 |
a = 5.8204 (4) Å | Mo Kα radiation |
b = 7.4391 (7) Å | µ = 1.15 mm−1 |
c = 11.2946 (8) Å | T = 293 K |
α = 72.537 (6)° | 0.27 × 0.25 × 0.23 mm |
β = 81.447 (6)° | |
Data collection top
Enraf–Nonius MACH-3 diffractometer | 2493 reflections with I > 2σ(I) |
Absorption correction: ψ scan (MolEN; Fair, 1990) | Rint = 0.016 |
Tmin = 0.921, Tmax = 0.999 | 3 standard reflections every 60 min |
5584 measured reflections | intensity decay: 0.4% |
2794 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.019 | 0 restraints |
wR(F2) = 0.053 | All H-atom parameters refined |
S = 1.06 | Δρmax = 0.42 e Å−3 |
2794 reflections | Δρmin = −0.36 e Å−3 |
158 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 | x | y | z | Uiso*/Ueq | |
Ca | 0.58378 (3) | −0.10882 (3) | 0.26757 (2) | 0.01520 (7) | |
S2 | 0.11026 (5) | 0.39277 (4) | 0.14787 (2) | 0.02340 (8) | |
S1 | 0.05190 (4) | 0.19718 (3) | 0.31591 (2) | 0.01416 (8) | |
O1 | −0.1415 (2) | 0.0778 (1) | 0.31740 (9) | 0.0283 (2) | |
O2 | −0.0090 (2) | 0.2941 (1) | 0.41232 (8) | 0.0229 (2) | |
O3 | 0.2651 (1) | 0.0853 (1) | 0.33853 (8) | 0.0230 (2) | |
O4 | 0.4996 (2) | −0.2213 (1) | 0.49796 (8) | 0.0227 (2) | |
O5 | 0.2839 (2) | −0.1002 (1) | 0.13392 (9) | 0.0255 (2) | |
O6 | 0.9226 (2) | −0.3029 (1) | 0.34210 (9) | 0.0241 (2) | |
O7 | 0.4565 (2) | −0.4274 (2) | 0.3127 (1) | 0.0397 (3) | |
O8 | 0.6280 (2) | 0.2034 (1) | 0.09372 (8) | 0.0256 (2) | |
O9 | 0.8018 (2) | −0.1907 (2) | 0.0926 (1) | 0.0329 (2) | |
H41 | 0.574 (4) | −0.175 (3) | 0.531 (2) | 0.053 (6)* | |
H42 | 0.365 (4) | −0.213 (3) | 0.520 (2) | 0.048 (6)* | |
H51 | 0.311 (3) | −0.154 (3) | 0.081 (2) | 0.037 (5)* | |
H52 | 0.173 (4) | −0.137 (3) | 0.174 (2) | 0.045 (6)* | |
H61 | 0.932 (4) | −0.416 (3) | 0.359 (2) | 0.043 (5)* | |
H62 | 0.956 (4) | −0.282 (3) | 0.397 (2) | 0.041 (5)* | |
H71 | 0.377 (4) | −0.462 (3) | 0.270 (2) | 0.052 (6)* | |
H72 | 0.468 (4) | −0.513 (4) | 0.367 (2) | 0.056 (7)* | |
H81 | 0.721 (4) | 0.258 (3) | 0.107 (2) | 0.040 (5)* | |
H82 | 0.513 (5) | 0.270 (4) | 0.098 (2) | 0.070 (8)* | |
H91 | 0.838 (5) | −0.290 (4) | 0.100 (2) | 0.064 (7)* | |
H92 | 0.804 (4) | −0.140 (3) | 0.022 (2) | 0.053 (6)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ca | 0.01528 (10) | 0.01573 (10) | 0.01556 (10) | −0.00045 (7) | −0.00336 (7) | −0.00548 (7) |
S2 | 0.03031 (15) | 0.01974 (14) | 0.01709 (13) | 0.00301 (10) | −0.00222 (10) | −0.00186 (10) |
S1 | 0.01456 (12) | 0.01367 (12) | 0.01549 (12) | 0.00007 (8) | −0.00403 (8) | −0.00528 (8) |
O1 | 0.0267 (4) | 0.0241 (4) | 0.0359 (5) | −0.0094 (3) | −0.0106 (3) | −0.0074 (4) |
O2 | 0.0288 (4) | 0.0240 (4) | 0.0184 (4) | 0.0030 (3) | −0.0028 (3) | −0.0110 (3) |
O3 | 0.0211 (4) | 0.0250 (4) | 0.0228 (4) | 0.0089 (3) | −0.0064 (3) | −0.0067 (3) |
O4 | 0.0197 (4) | 0.0286 (4) | 0.0193 (4) | 0.0025 (3) | −0.0029 (3) | −0.0064 (3) |
O5 | 0.0211 (4) | 0.0330 (5) | 0.0249 (4) | −0.0023 (3) | −0.0054 (3) | −0.0112 (4) |
O6 | 0.0280 (4) | 0.0229 (4) | 0.0249 (4) | 0.0067 (3) | −0.0100 (3) | −0.0106 (3) |
O7 | 0.0493 (6) | 0.0211 (4) | 0.0485 (6) | −0.0108 (4) | −0.0279 (5) | 0.0017 (4) |
O8 | 0.0242 (4) | 0.0270 (4) | 0.0263 (4) | −0.0023 (3) | −0.0053 (3) | −0.0078 (3) |
O9 | 0.0394 (5) | 0.0382 (5) | 0.0225 (4) | 0.0106 (4) | −0.0028 (4) | −0.0134 (4) |
Geometric parameters (Å, º) top
Ca—O1i | 2.3973 (9) | Ca—O6 | 2.4854 (9) |
Ca—O7 | 2.3991 (10) | Ca—O8 | 2.5467 (10) |
Ca—O9 | 2.4066 (10) | S2—S1 | 2.0080 (4) |
Ca—O5 | 2.4584 (9) | S1—O1 | 1.4617 (9) |
Ca—O4 | 2.4626 (9) | S1—O2 | 1.4707 (8) |
Ca—O3 | 2.4834 (8) | S1—O3 | 1.4717 (8) |
| | | |
O1i—Ca—O7 | 142.21 (4) | O1i—Ca—O8 | 72.33 (3) |
O1i—Ca—O9 | 101.82 (4) | O7—Ca—O8 | 142.08 (4) |
O7—Ca—O9 | 80.01 (5) | O9—Ca—O8 | 76.21 (4) |
O1i—Ca—O5 | 144.27 (3) | O5—Ca—O8 | 72.96 (3) |
O7—Ca—O5 | 73.43 (4) | O4—Ca—O8 | 138.46 (3) |
O9—Ca—O5 | 77.80 (4) | O3—Ca—O8 | 77.25 (3) |
O1i—Ca—O4 | 80.79 (3) | O6—Ca—O8 | 122.54 (3) |
O7—Ca—O4 | 75.75 (4) | O1—S1—O2 | 109.46 (5) |
O9—Ca—O4 | 141.47 (4) | O1—S1—O3 | 111.06 (5) |
O5—Ca—O4 | 121.86 (3) | O2—S1—O3 | 109.83 (5) |
O1i—Ca—O3 | 89.13 (3) | O1—S1—S2 | 109.23 (4) |
O7—Ca—O3 | 110.24 (4) | O2—S1—S2 | 108.38 (4) |
O9—Ca—O3 | 146.50 (3) | O3—S1—S2 | 108.83 (4) |
O5—Ca—O3 | 75.15 (3) | S1—O1—Caii | 165.86 (6) |
O4—Ca—O3 | 71.15 (3) | S1—O3—Ca | 149.60 (5) |
O1i—Ca—O6 | 69.20 (3) | H41—O4—H42 | 113 (2) |
O7—Ca—O6 | 75.86 (4) | H51—O5—H52 | 109 (2) |
O9—Ca—O6 | 71.92 (3) | H61—O6—H62 | 104 (2) |
O5—Ca—O6 | 139.86 (3) | H71—O7—H72 | 104 (2) |
O4—Ca—O6 | 73.38 (3) | H81—O8—H82 | 103 (2) |
O3—Ca—O6 | 140.85 (3) | H91—O9—H92 | 108 (2) |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H41···O3iii | 0.77 (3) | 2.13 (3) | 2.8834 (13) | 166 (2) |
O4—H42···O2iv | 0.79 (2) | 2.15 (2) | 2.9035 (13) | 160 (2) |
O5—H51···O8v | 0.81 (2) | 2.09 (2) | 2.8667 (13) | 161.5 (18) |
O5—H52···O6ii | 0.74 (2) | 2.28 (2) | 2.9878 (14) | 160 (2) |
O6—H61···O2vi | 0.81 (2) | 2.08 (2) | 2.8861 (13) | 173 (2) |
O6—H62···O2iii | 0.74 (2) | 2.20 (2) | 2.9118 (12) | 165 (2) |
O7—H71···S2vii | 0.81 (2) | 2.68 (2) | 3.4904 (11) | 175 (2) |
O7—H72···O4viii | 0.75 (3) | 2.12 (3) | 2.8656 (14) | 171 (2) |
O8—H81···S2i | 0.74 (2) | 2.68 (2) | 3.4116 (10) | 168.1 (19) |
O8—H82···S2 | 0.82 (3) | 2.52 (3) | 3.3177 (10) | 164 (2) |
O9—H91···S2vi | 0.74 (3) | 2.74 (3) | 3.4437 (12) | 159 (3) |
O9—H92···O5v | 0.78 (2) | 2.20 (2) | 2.9034 (15) | 151 (2) |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z; (iii) −x+1, −y, −z+1; (iv) −x, −y, −z+1; (v) −x+1, −y, −z; (vi) x+1, y−1, z; (vii) x, y−1, z; (viii) −x+1, −y−1, −z+1. |
(II) strontium(II) thiosulfate pentahydrate
top
Crystal data top
SrS2O3·5H2O | F(000) = 1152 |
Mr = 289.84 | Dx = 2.234 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 21.005 (3) Å | Cell parameters from 25 reflections |
b = 8.1371 (6) Å | θ = 13.3–16.3° |
c = 10.587 (1) Å | µ = 6.75 mm−1 |
β = 107.78 (1)° | T = 293 K |
V = 1723.2 (3) Å3 | Parallelepiped, colourless |
Z = 8 | 0.25 × 0.24 × 0.22 mm |
Data collection top
Enraf–Nonius MACH-3 diffractometer | 1605 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed X-ray tube | Rint = 0.085 |
Graphite monochromator | θmax = 30.5°, θmin = 2.0° |
ω/2θ scans | h = −29→29 |
Absorption correction: ψ scan (MolEN; Fair, 1990) | k = −11→11 |
Tmin = 0.889, Tmax = 1.000 | l = −15→15 |
6468 measured reflections | 3 standard reflections every 60 min |
2614 independent reflections | intensity decay: −14.6% |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.031 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.082 | w = 1/[σ2(Fo2) + (0.0259P)2 + 3.0808P] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max = 0.001 |
2614 reflections | Δρmax = 0.95 e Å−3 |
141 parameters | Δρmin = −0.91 e Å−3 |
7 restraints | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0032 (2) |
Crystal data top
SrS2O3·5H2O | V = 1723.2 (3) Å3 |
Mr = 289.84 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 21.005 (3) Å | µ = 6.75 mm−1 |
b = 8.1371 (6) Å | T = 293 K |
c = 10.587 (1) Å | 0.25 × 0.24 × 0.22 mm |
β = 107.78 (1)° | |
Data collection top
Enraf–Nonius MACH-3 diffractometer | 1605 reflections with I > 2σ(I) |
Absorption correction: ψ scan (MolEN; Fair, 1990) | Rint = 0.085 |
Tmin = 0.889, Tmax = 1.000 | 3 standard reflections every 60 min |
6468 measured reflections | intensity decay: −14.6% |
2614 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.031 | 7 restraints |
wR(F2) = 0.082 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.95 e Å−3 |
2614 reflections | Δρmin = −0.91 e Å−3 |
141 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 | x | y | z | Uiso*/Ueq | |
Sr | 0.22283 (2) | 0.32297 (4) | 0.18777 (3) | 0.0163 (1) | |
S1 | 0.17449 (5) | 0.0349 (1) | 0.44696 (9) | 0.0145 (2) | |
S2 | 0.07481 (5) | 0.0426 (2) | 0.3831 (1) | 0.0278 (3) | |
O1 | 0.1993 (2) | 0.1444 (3) | 0.5616 (3) | 0.0226 (6) | |
O2 | 0.1974 (2) | −0.1352 (3) | 0.4834 (3) | 0.0226 (6) | |
O3 | 0.2003 (1) | 0.0841 (3) | 0.3370 (3) | 0.0217 (6) | |
O4 | 0.3164 (2) | 0.0957 (4) | 0.2264 (3) | 0.0205 (6) | |
O5 | 0.1563 (2) | 0.5201 (4) | −0.0071 (3) | 0.0245 (7) | |
O6 | 0.4344 (2) | 0.2605 (5) | 0.3485 (4) | 0.0396 (9) | |
O7 | 0.0932 (2) | 0.2606 (6) | 0.1285 (5) | 0.049 (1) | |
O8 | 0.0212 (3) | 0.4853 (8) | 0.3819 (7) | 0.095 (2) | |
H41 | 0.322 (3) | 0.073 (7) | 0.162 (4) | 0.06 (2)* | |
H42 | 0.358 (3) | 0.144 (6) | 0.269 (5) | 0.046 (17)* | |
H51 | 0.166 (3) | 0.604 (6) | 0.005 (5) | 0.027 (15)* | |
H52 | 0.114 (3) | 0.524 (7) | −0.043 (6) | 0.054 (19)* | |
H61 | 0.431 (3) | 0.320 (6) | 0.401 (5) | 0.046 (19)* | |
H62 | 0.435 (4) | 0.331 (8) | 0.288 (7) | 0.11 (3)* | |
H71 | 0.084 (6) | 0.199 (11) | 0.065 (8) | 0.19 (6)* | |
H72 | 0.086 (3) | 0.206 (7) | 0.182 (5) | 0.050 (19)* | |
H81 | 0.007 (6) | 0.594 (7) | 0.378 (11) | 0.172 (17)* | |
H82 | −0.008 (3) | 0.430 (11) | 0.413 (8) | 0.155 (18)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Sr | 0.02321 (19) | 0.01178 (16) | 0.01336 (17) | 0.00018 (18) | 0.00490 (12) | 0.00032 (16) |
S1 | 0.0179 (4) | 0.0122 (4) | 0.0127 (4) | 0.0004 (4) | 0.0040 (3) | −0.0001 (3) |
S2 | 0.0169 (5) | 0.0366 (6) | 0.0277 (6) | 0.0005 (5) | 0.0038 (4) | −0.0038 (5) |
O1 | 0.0283 (16) | 0.0200 (15) | 0.0169 (13) | −0.0012 (12) | 0.0027 (12) | −0.0039 (11) |
O2 | 0.0308 (16) | 0.0133 (13) | 0.0235 (15) | 0.0027 (12) | 0.0080 (13) | 0.0030 (11) |
O3 | 0.0260 (15) | 0.0234 (15) | 0.0164 (14) | 0.0006 (13) | 0.0074 (12) | 0.0032 (12) |
O4 | 0.0252 (16) | 0.0225 (15) | 0.0148 (15) | −0.0018 (13) | 0.0075 (13) | 0.0007 (12) |
O5 | 0.0331 (19) | 0.0189 (16) | 0.0198 (16) | −0.0027 (15) | 0.0056 (14) | 0.0003 (13) |
O6 | 0.041 (2) | 0.038 (2) | 0.041 (2) | −0.0023 (18) | 0.0148 (18) | −0.002 (2) |
O7 | 0.037 (2) | 0.052 (3) | 0.058 (3) | 0.004 (2) | 0.014 (2) | 0.028 (2) |
O8 | 0.055 (3) | 0.081 (4) | 0.138 (5) | 0.003 (3) | 0.013 (3) | 0.008 (4) |
Geometric parameters (Å, º) top
Sr—O2i | 2.568 (3) | Sr—O2ii | 2.840 (3) |
Sr—O4ii | 2.624 (3) | Sr—S1ii | 3.3968 (10) |
Sr—O3 | 2.637 (3) | Sr—Srii | 4.3213 (4) |
Sr—O4 | 2.638 (3) | S1—O1 | 1.467 (3) |
Sr—O5 | 2.650 (3) | S1—O2 | 1.477 (3) |
Sr—O7 | 2.651 (4) | S1—O3 | 1.481 (3) |
Sr—O1iii | 2.672 (3) | S1—S2 | 1.9952 (14) |
Sr—O3ii | 2.730 (3) | | |
| | | |
O2i—Sr—O4ii | 142.02 (9) | O7—Sr—O3ii | 136.18 (11) |
O2i—Sr—O3 | 92.12 (9) | O1iii—Sr—O3ii | 79.47 (8) |
O4ii—Sr—O3 | 106.44 (9) | O2i—Sr—O2ii | 62.94 (10) |
O2i—Sr—O4 | 70.56 (9) | O4ii—Sr—O2ii | 115.37 (9) |
O4ii—Sr—O4 | 146.82 (4) | O3—Sr—O2ii | 136.02 (8) |
O3—Sr—O4 | 69.63 (9) | O4—Sr—O2ii | 68.04 (8) |
O2i—Sr—O5 | 77.27 (10) | O5—Sr—O2ii | 72.80 (10) |
O4ii—Sr—O5 | 67.10 (10) | O7—Sr—O2ii | 129.47 (13) |
O3—Sr—O5 | 139.83 (10) | O1iii—Sr—O2ii | 108.68 (9) |
O4—Sr—O5 | 137.39 (10) | O3ii—Sr—O2ii | 50.48 (8) |
O2i—Sr—O7 | 75.64 (14) | O1—S1—O2 | 110.35 (16) |
O4ii—Sr—O7 | 80.53 (13) | O1—S1—O3 | 111.29 (16) |
O3—Sr—O7 | 68.99 (11) | O2—S1—O3 | 106.92 (17) |
O4—Sr—O7 | 124.44 (12) | O1—S1—S2 | 109.39 (13) |
O5—Sr—O7 | 70.85 (12) | O2—S1—S2 | 110.02 (13) |
O2i—Sr—O1iii | 143.40 (9) | O3—S1—S2 | 108.83 (12) |
O4ii—Sr—O1iii | 74.55 (9) | O1—S1—Sriv | 123.04 (12) |
O3—Sr—O1iii | 69.25 (8) | O2—S1—Sriv | 55.71 (12) |
O4—Sr—O1iii | 73.41 (9) | O3—S1—Sriv | 51.38 (11) |
O5—Sr—O1iii | 136.92 (9) | S2—S1—Sriv | 127.50 (5) |
O7—Sr—O1iii | 121.85 (13) | H41—O4—H42 | 99 (5) |
O2i—Sr—O3ii | 111.05 (8) | H51—O5—H52 | 104 (6) |
O4ii—Sr—O3ii | 68.43 (9) | H61—O6—H62 | 98 (6) |
O3—Sr—O3ii | 148.32 (3) | H71—O7—H72 | 102 (8) |
O4—Sr—O3ii | 97.24 (9) | H81—O8—H82 | 105 (9) |
O5—Sr—O3ii | 68.94 (10) | | |
Symmetry codes: (i) x, −y, z−1/2; (ii) −x+1/2, y+1/2, −z+1/2; (iii) −x+1/2, −y+1/2, −z+1; (iv) −x+1/2, y−1/2, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H41···O5v | 0.75 (4) | 1.98 (4) | 2.725 (4) | 171 (6) |
O4—H42···O6 | 0.94 (6) | 1.83 (6) | 2.767 (5) | 174 (5) |
O5—H51···O1vi | 0.71 (5) | 2.19 (5) | 2.898 (4) | 174 (6) |
O5—H52···O8vi | 0.85 (6) | 1.87 (6) | 2.720 (6) | 175 (6) |
O6—H61···S2iii | 0.75 (4) | 2.58 (4) | 3.320 (4) | 166 (6) |
O6—H62···S2ii | 0.86 (4) | 2.46 (4) | 3.321 (4) | 173 (8) |
O7—H71···S2i | 0.82 (5) | 2.72 (5) | 3.518 (6) | 168 (11) |
O7—H72···S2 | 0.77 (4) | 2.58 (4) | 3.346 (5) | 172 (6) |
O8—H81···O6vii | 0.93 (5) | 2.00 (8) | 2.841 (7) | 150 (11) |
O8—H82···O7viii | 0.89 (5) | 2.20 (5) | 2.994 (7) | 148 (2) |
Symmetry codes: (i) x, −y, z−1/2; (ii) −x+1/2, y+1/2, −z+1/2; (iii) −x+1/2, −y+1/2, −z+1; (v) −x+1/2, −y+1/2, −z; (vi) x, −y+1, z−1/2; (vii) x−1/2, y+1/2, z; (viii) −x, y, −z+1/2. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | CaS2O3·6H2O | SrS2O3·5H2O |
Mr | 260.32 | 289.84 |
Crystal system, space group | Triclinic, P1 | Monoclinic, C2/c |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 5.8204 (4), 7.4391 (7), 11.2946 (8) | 21.005 (3), 8.1371 (6), 10.587 (1) |
α, β, γ (°) | 72.537 (6), 81.447 (6), 87.282 (6) | 90, 107.78 (1), 90 |
V (Å3) | 461.31 (7) | 1723.2 (3) |
Z | 2 | 8 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 1.15 | 6.75 |
Crystal size (mm) | 0.27 × 0.25 × 0.23 | 0.25 × 0.24 × 0.22 |
|
Data collection |
Diffractometer | Enraf–Nonius MACH-3 diffractometer | Enraf–Nonius MACH-3 diffractometer |
Absorption correction | ψ scan (MolEN; Fair, 1990) | ψ scan (MolEN; Fair, 1990) |
Tmin, Tmax | 0.921, 0.999 | 0.889, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5584, 2794, 2493 | 6468, 2614, 1605 |
Rint | 0.016 | 0.085 |
(sin θ/λ)max (Å−1) | 0.712 | 0.714 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.019, 0.053, 1.06 | 0.031, 0.082, 1.04 |
No. of reflections | 2794 | 2614 |
No. of parameters | 158 | 141 |
No. of restraints | 0 | 7 |
H-atom treatment | All H-atom parameters refined | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.42, −0.36 | 0.95, −0.91 |
Selected bond lengths (Å) for (I) topCa—O1i | 2.3973 (9) | Ca—O6 | 2.4854 (9) |
Ca—O7 | 2.3991 (10) | Ca—O8 | 2.5467 (10) |
Ca—O9 | 2.4066 (10) | S2—S1 | 2.0080 (4) |
Ca—O5 | 2.4584 (9) | S1—O1 | 1.4617 (9) |
Ca—O4 | 2.4626 (9) | S1—O2 | 1.4707 (8) |
Ca—O3 | 2.4834 (8) | S1—O3 | 1.4717 (8) |
Symmetry code: (i) x+1, y, z. |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H41···O3ii | 0.77 (3) | 2.13 (3) | 2.8834 (13) | 166 (2) |
O4—H42···O2iii | 0.79 (2) | 2.15 (2) | 2.9035 (13) | 160 (2) |
O5—H51···O8iv | 0.81 (2) | 2.09 (2) | 2.8667 (13) | 161.5 (18) |
O5—H52···O6v | 0.74 (2) | 2.28 (2) | 2.9878 (14) | 160 (2) |
O6—H61···O2vi | 0.81 (2) | 2.08 (2) | 2.8861 (13) | 173 (2) |
O6—H62···O2ii | 0.74 (2) | 2.20 (2) | 2.9118 (12) | 165 (2) |
O7—H71···S2vii | 0.81 (2) | 2.68 (2) | 3.4904 (11) | 175 (2) |
O7—H72···O4viii | 0.75 (3) | 2.12 (3) | 2.8656 (14) | 171 (2) |
O8—H81···S2i | 0.74 (2) | 2.68 (2) | 3.4116 (10) | 168.1 (19) |
O8—H82···S2 | 0.82 (3) | 2.52 (3) | 3.3177 (10) | 164 (2) |
O9—H91···S2vi | 0.74 (3) | 2.74 (3) | 3.4437 (12) | 159 (3) |
O9—H92···O5iv | 0.78 (2) | 2.20 (2) | 2.9034 (15) | 151 (2) |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, −y, −z+1; (iii) −x, −y, −z+1; (iv) −x+1, −y, −z; (v) x−1, y, z; (vi) x+1, y−1, z; (vii) x, y−1, z; (viii) −x+1, −y−1, −z+1. |
Selected bond lengths (Å) for (II) topSr—O2i | 2.568 (3) | Sr—O3ii | 2.730 (3) |
Sr—O4ii | 2.624 (3) | Sr—O2ii | 2.840 (3) |
Sr—O3 | 2.637 (3) | S1—O1 | 1.467 (3) |
Sr—O4 | 2.638 (3) | S1—O2 | 1.477 (3) |
Sr—O5 | 2.650 (3) | S1—O3 | 1.481 (3) |
Sr—O7 | 2.651 (4) | S1—S2 | 1.9952 (14) |
Sr—O1iii | 2.672 (3) | | |
Symmetry codes: (i) x, −y, z−1/2; (ii) −x+1/2, y+1/2, −z+1/2; (iii) −x+1/2, −y+1/2, −z+1. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H41···O5iv | 0.75 (4) | 1.98 (4) | 2.725 (4) | 171 (6) |
O4—H42···O6 | 0.94 (6) | 1.83 (6) | 2.767 (5) | 174 (5) |
O5—H51···O1v | 0.71 (5) | 2.19 (5) | 2.898 (4) | 174 (6) |
O5—H52···O8v | 0.85 (6) | 1.87 (6) | 2.720 (6) | 175 (6) |
O6—H61···S2iii | 0.75 (4) | 2.58 (4) | 3.320 (4) | 166 (6) |
O6—H62···S2ii | 0.86 (4) | 2.46 (4) | 3.321 (4) | 173 (8) |
O7—H71···S2i | 0.82 (5) | 2.72 (5) | 3.518 (6) | 168 (11) |
O7—H72···S2 | 0.77 (4) | 2.58 (4) | 3.346 (5) | 172 (6) |
O8—H81···O6vi | 0.93 (5) | 2.00 (8) | 2.841 (7) | 150 (11) |
O8—H82···O7vii | 0.89 (5) | 2.20 (5) | 2.994 (7) | 148 (2) |
Symmetry codes: (i) x, −y, z−1/2; (ii) −x+1/2, y+1/2, −z+1/2; (iii) −x+1/2, −y+1/2, −z+1; (iv) −x+1/2, −y+1/2, −z; (v) x, −y+1, z−1/2; (vi) x−1/2, y+1/2, z; (vii) −x, y, −z+1/2. |
Because of its distinct asymmetric morphology, many textbooks on crystallography use calcium thiosulfate hexahydrate as the classic example of a compound that crystallizes in the triclinic pedial class (point group 1; Fig. 1a). It is of historical interest that CaS2O3·6H2O served Mitscherlich (1826) as an example and proof of the existence of the so-called `diclinic' crystal system. Not until 1862 did Zepharovich (1862) assign these crystals to the triclinic system; his description agrees well with the results of our morphological studies. Earlier morphological studies are summarized by Groth (1908).
Surprisingly, we found no structural information about CaS2O3·6H2O in the literature. The crystal structures of hydrated thiosulfates of alkaline earth cations are known for MgS2O3·6H2O (Nardelli et al., 1962; Baggio et al., 1969; Elerman et al., 1982, 1983) and BaS2O3·H2O (Manojlović-Muir, 1975; Nardelli & Fava, 1962, Aka et al., 1980) only. Both compounds were investigated in detail by X-ray and neutron diffraction methods. Further structural analyses of thiosulfates with divalent cations were performed for CdS2O3·2H2O (Baggio et al., 1997) and NiS2O3·6H2O (Elerman et al., 1975), which are isostructural with the magnesium compound. All structurally known thiosulfates of divalent cations are hydrated and crystallize in centrosymmetric space groups. The present paper, which presents the crystal structures of CaS2O3·6H2O and SrS2O3·5H2O, extends our knowledge of the crystal chemistry of the alkaline earth thiosulfates. Until now, for both compounds, only the unit-cell parameters have been given in the literature (Keglevich, 1958). In contrast to the results of earlier morphological studies, our structure analysis, based on single-crystal X-ray diffraction data, shows that CaS2O3·6H2O crystallizes in the triclinic pinacoidal point group.
In CaS2O3·6H2O, the geometry and the bonding properties of the S2O32− anions are closely related to those in MgS2O3·6H2O (e.g. Elerman et al., 1983) and NiS2O3·6H2O (Elerman et al., 1975). The bond angles around atom S1 deviate from the ideal tetrahedral arrangement only slightly [mean 109.5 (9)°]; the angles and lengths correspond to the π-bonding character of the S—O [mean 1.468 (6) Å] and S—S bonds. Within the standard uncertainties, the S—S distance is equal to those in magnesium and nickel thiosulfate hexahydrate.
The Ca2+ cations are eightfold coordinated by O atoms of six symmetry-independent water molecules and of two S2O3 groups [(Ca—O)mean = 2.45 (5) Å] to form a distorted square antiprism [Ca(H2O)6O2]. All water molecules are included in the coordination sphere of the Ca2+ cation.
The main characteristics of the CaS2O3·6H2O structure are chains, parallel to [100], of alternating [S2O3] and [Ca(H2O)6O2] groups, which are connected via common O atoms (Fig. 2). Each chain link has the composition [Ca(H2O)6(S2O3)]. The arrangement of the atoms, [—Ca—O—S—O—]∞, builds up a zigzag chain in which the Ca atoms are turned towards atoms O1 to form the shortest Ca—O distance inside the Ca coordination polyhedron. Inside the chain, all [S2O3] and all [Ca(H2O)6O2] polyhedra are aligned in the same manner.
A system of hydrogen bonds plays an important role in the stability of the structure. Hydrogen bonds between water molecules and between water molecules and terminal S atoms exist among the chain links and inside the chains (Fig. 3).
As expected, in SrS2O3·5H2O, the bond distances and angles of the S2O32− anions are similar to those in BaS2O3·H2O (e.g. Manojlović-Muir, 1975) and CaS2O3·6H2O. The S—S distance is, however, significantly shorter than that in CaS2O3·6H2O (Δd = −0.013 Å) and longer than that in BaS2O3·H2O (Δd = 0.016 Å), while the S—O distances [mean 1.475 (7) Å] are almost equal. The mean bond angles are nearly ideal tetrahedral [(O—S—O)mean = 109 (2)° and (S—S—O)mean = 109.4 (6)°], but the O2—S1—O3 angle differs significantly from the average. The thiosulfate group serves as a bidentate ligand. As a result, the O2···O3 distance in the coordination sphere of the Sr2+ cation is shortened.
The Sr2+ cation is ninefold coordinated by O atoms of four water molecules (2 × O4, O5 and O7) and four S2O32− anions (one bidentate and three monodentate groups), with a mean distance of 2.67 (8) Å. The coordination polyhedron, like that in CaS2O3·6H2O, can be described as a distorted squared antiprism, although it is capped by an additional atom (O2) to form an [Sr(H2O)4O5] unit.
The main features of the SrS2O3·5H2O structure are layers, parallel to (100), of alternating [S2O3] and [Sr(H2O)4O5] groups sharing common O atoms and O···O edges, with [Sr(H2O)3O(S2O3)]∞ as the unique repeat unit (Fig. 4). The unit cell consists of two layers with a thickness of about 7 Å each and a separation of about 3.5 Å (Fig. 5). The core of the layer is built up from differently oriented symmetry-equivalent [Sr(H2O)4O5] groups, while [S2O3] groups together with water molecules form the border of the layer. All terminal S atoms are directed towards the space between the layers. Both border atoms (S2 and O7) show high thermal motion parallel to the layer plane. Their large anisotropic vibration indicates weak interaction between the layers.
In contrast to that of the Ca compound, the structure of SrS2O3·5H2O contains water molecules outside the coordination sphere of the alkaline earth atom. Two of the five symmetrically independent water molecules (O6 and O8) are positioned between the layers. Both water molecules connect the polyhedron layer via hydrogen bonds to water molecules O4, O5 and O7, which belong to the Sr coordination sphere (Fig. 5). Inside the polyhedron layer, hydrogen bonds exist between water molecules O6 and O7 and terminal atoms S2. As for the Ca compound, the angles between the S—S bond and the H atoms of the bridges are about 90°, whereas the bridge itself is almost linear.