Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106026084/bm3008sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106026084/bm3008I-300sup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106026084/bm3008I-100sup3.hkl |
CCDC references: 621280; 621281
Colourless single crystals of (I) were grown from a methanol solution containing stoichiometric amounts of thiourea and oxalic acid.
For the refinement of the 100 K structure of (I), the reduced cell with a = 6.030 (1) Å, b = 7.495 (2) Å, c = 8.414 (2) Å, α = 98.334 (4)°, β = 109.525 (3)° and γ = 113.551 (3)° used in data collection was re-evaluated in the same setting as the cell of the 300 K structure and the indices of the intensity data transformed accordingly by means of the (row-wise) transformation matrix (100, 110, 001). In both structures, in the final stages of refinement H atoms were introduced in calculated positions with N—H and C—H distances set to 0.86 and 0.96 Å, respectively, for I-300, and 0.88 and 0.98 Å, respectively, for I-100. H atoms attached to N atoms were restrained to be coplanar with the non-H atoms of the tu molecule. All H atoms were then refined with a riding model, while their isotropic displacement parameters were also refined, as was the rotational orientation of the methyl group.
Data collection: APEX2 (Bruker–Nonius, 2003) for I-300; SMART (Bruker, 2004) for I-100. Cell refinement: SAINT (Bruker, 2003) for I-300; SMART for I-100. Data reduction: SAINT for I-300; SAINT (Bruker, 2004) for I-100. For both compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
2CH4N2S·C4H6O4 | Z = 1 |
Mr = 270.33 | F(000) = 142 |
TriclinicP1 | Dx = 1.379 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.1010 (3) Å | Cell parameters from 1585 reflections |
b = 7.6447 (4) Å | θ = 2.7–34.0° |
c = 8.4463 (5) Å | µ = 0.42 mm−1 |
α = 66.239 (3)° | T = 300 K |
β = 70.516 (3)° | Irregular shape, colourless |
γ = 67.479 (3)° | 0.30 × 0.20 × 0.15 mm |
V = 325.48 (3) Å3 |
Bruker Nonius X8 APEXII 4K CCD diffractometer | 2151 independent reflections |
Radiation source: sealed tube | 1463 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.019 |
Detector resolution: 0 pixels mm-1 | θmax = 34.0°, θmin = 2.7° |
φ and ω scans | h = −9→9 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | k = −11→11 |
Tmin = 0.797, Tmax = 1.000 | l = −12→12 |
4488 measured reflections |
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)] = 0.041 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.113 | Only H-atom displacement parameters refined |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0566P)2 + 0.0265P] where P = (Fo2 + 2Fc2)/3 |
2151 reflections | (Δ/σ)max < 0.001 |
81 parameters | Δρmax = 0.25 e Å−3 |
0 restraints | Δρmin = −0.21 e Å−3 |
2CH4N2S·C4H6O4 | γ = 67.479 (3)° |
Mr = 270.33 | V = 325.48 (3) Å3 |
TriclinicP1 | Z = 1 |
a = 6.1010 (3) Å | Mo Kα radiation |
b = 7.6447 (4) Å | µ = 0.42 mm−1 |
c = 8.4463 (5) Å | T = 300 K |
α = 66.239 (3)° | 0.30 × 0.20 × 0.15 mm |
β = 70.516 (3)° |
Bruker Nonius X8 APEXII 4K CCD diffractometer | 2151 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 1463 reflections with I > 2σ(I) |
Tmin = 0.797, Tmax = 1.000 | Rint = 0.019 |
4488 measured reflections |
R[F2 > 2σ(F2)] = 0.041 | 0 restraints |
wR(F2) = 0.113 | Only H-atom displacement parameters refined |
S = 1.02 | Δρmax = 0.25 e Å−3 |
2151 reflections | Δρmin = −0.21 e Å−3 |
81 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. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 2.9435 (39) x - 3.8414 (33) y + 2.9792 (69) z = 0.6198 (74) * 0.0004 (0.0004) S1 * -0.0014 (0.0014) C1 * 0.0005 (0.0005) N1 * 0.0005 (0.0005) N2 Rms deviation of fitted atoms = 0.0008 2.9963 (41) x - 3.8201 (59) y + 2.9254 (66) z = 1.0508 (76) Angle to previous plane (with approximate e.s.d.) = 0.77 (14) * -0.0101 (0.0006) O1 * -0.0357 (0.0014) O2 * -0.0090 (0.0017) C2 * 0.0244 (0.0010) C3 * 0.0101 (0.0006) O1_$1 * 0.0357 (0.0014) O2_$1 * 0.0090 (0.0017) C2_$1 * -0.0244 (0.0010) C3_$1 Rms deviation of fitted atoms = 0.0226 |
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 | ||
S1 | 0.79690 (8) | 1.04238 (7) | 0.76490 (5) | 0.05309 (17) | |
O1 | 0.4260 (3) | 0.5831 (2) | 0.68082 (18) | 0.0661 (4) | |
O2 | 0.2522 (2) | 0.40966 (18) | 0.62362 (16) | 0.0568 (3) | |
N1 | 0.4719 (3) | 0.8541 (3) | 0.8433 (2) | 0.0638 (5) | |
H1 | 0.4055 | 0.7867 | 0.8227 | 0.079 (7)* | |
H2 | 0.4155 | 0.8856 | 0.9392 | 0.068 (6)* | |
N2 | 0.7416 (3) | 0.8576 (2) | 0.58133 (16) | 0.0529 (4) | |
H3 | 0.6713 | 0.7901 | 0.5645 | 0.061 (6)* | |
H4 | 0.8640 | 0.8914 | 0.5035 | 0.057 (5)* | |
C1 | 0.6612 (3) | 0.9097 (2) | 0.72725 (19) | 0.0417 (3) | |
C2 | 0.4136 (3) | 0.5026 (2) | 0.5889 (2) | 0.0506 (4) | |
C3 | 0.0840 (4) | 0.3925 (4) | 0.7941 (3) | 0.0728 (6) | |
H5 | 0.0179 | 0.5200 | 0.8133 | 0.093 (8)* | |
H6 | 0.1681 | 0.2970 | 0.8860 | 0.110 (9)* | |
H7 | −0.0452 | 0.3492 | 0.7955 | 0.131 (11)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.0602 (3) | 0.0744 (3) | 0.0456 (2) | −0.0417 (2) | 0.00909 (17) | −0.0346 (2) |
O1 | 0.0870 (9) | 0.0712 (8) | 0.0668 (8) | −0.0393 (7) | −0.0069 (7) | −0.0398 (7) |
O2 | 0.0654 (8) | 0.0624 (7) | 0.0606 (7) | −0.0311 (6) | −0.0086 (6) | −0.0288 (6) |
N1 | 0.0705 (10) | 0.0958 (12) | 0.0545 (8) | −0.0572 (9) | 0.0186 (7) | −0.0466 (8) |
N2 | 0.0613 (9) | 0.0739 (9) | 0.0431 (7) | −0.0393 (8) | 0.0076 (6) | −0.0340 (7) |
C1 | 0.0463 (8) | 0.0481 (8) | 0.0386 (7) | −0.0212 (7) | −0.0017 (6) | −0.0200 (6) |
C2 | 0.0631 (10) | 0.0446 (8) | 0.0571 (9) | −0.0195 (8) | −0.0151 (8) | −0.0231 (7) |
C3 | 0.0798 (14) | 0.0778 (14) | 0.0703 (13) | −0.0376 (12) | −0.0055 (11) | −0.0269 (12) |
S1—C1 | 1.7010 (14) | N2—C1 | 1.3269 (18) |
O1—C2 | 1.2029 (18) | N2—H3 | 0.8600 |
O2—C2 | 1.318 (2) | N2—H4 | 0.8600 |
O2—C3 | 1.452 (2) | C2—C2i | 1.525 (3) |
N1—C1 | 1.327 (2) | C3—H5 | 0.9600 |
N1—H1 | 0.8600 | C3—H6 | 0.9600 |
N1—H2 | 0.8600 | C3—H7 | 0.9600 |
C2—O2—C3 | 116.52 (14) | O1—C2—O2 | 126.07 (17) |
C1—N1—H1 | 120.0 | O1—C2—C2i | 123.5 (2) |
C1—N1—H2 | 120.0 | O2—C2—C2i | 110.40 (16) |
H1—N1—H2 | 120.0 | O2—C3—H5 | 109.5 |
C1—N2—H3 | 120.0 | O2—C3—H6 | 109.5 |
C1—N2—H4 | 120.0 | H5—C3—H6 | 109.5 |
H3—N2—H4 | 120.0 | O2—C3—H7 | 109.5 |
N2—C1—N1 | 117.77 (13) | H5—C3—H7 | 109.5 |
N2—C1—S1 | 121.18 (11) | H6—C3—H7 | 109.5 |
N1—C1—S1 | 121.05 (11) | ||
C3—O1—C2—C2i | −178.4 (3) | O2—C2—C2i—O1i | −0.6 (3) |
O1—C2—C2i—O2i | 0.6 (3) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.86 | 2.26 | 3.0413 (17) | 150 |
N2—H3···O1 | 0.86 | 2.30 | 3.0683 (19) | 149 |
N2—H3···O2i | 0.86 | 2.45 | 3.1498 (16) | 139 |
N1—H2···S1ii | 0.86 | 2.57 | 3.4292 (15) | 172 |
N2—H4···S1iii | 0.86 | 2.53 | 3.3791 (14) | 167 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+2, −z+2; (iii) −x+2, −y+2, −z+1. |
2CH4N2S·C4H6O4 | Z = 1 |
Mr = 270.33 | F(000) = 142 |
TriclinicP1 | Dx = 1.443 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.030 (1) Å | Cell parameters from 962 reflections |
b = 7.511 (2) Å | θ = 2.7–28.1° |
c = 8.414 (2) Å | µ = 0.43 mm−1 |
α = 65.613 (4)° | T = 100 K |
β = 70.475 (3)° | Irregular shape, colourless |
γ = 66.168 (3)° | 0.30 × 0.20 × 0.15 mm |
V = 311.01 (12) Å3 |
Bruker SMART CCD area-detector diffractometer | 1288 independent reflections |
Radiation source: sealed tube | 1091 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.023 |
φ and ω scans | θmax = 28.1°, θmin = 2.7° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −7→7 |
Tmin = 0.754, Tmax = 1.000 | k = −9→9 |
2389 measured reflections | l = −11→10 |
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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.103 | Only H-atom displacement parameters refined |
S = 1.11 | w = 1/[σ2(Fo2) + (0.0565P)2 + 0.0376P] where P = (Fo2 + 2Fc2)/3 |
1288 reflections | (Δ/σ)max < 0.001 |
81 parameters | Δρmax = 0.46 e Å−3 |
0 restraints | Δρmin = −0.39 e Å−3 |
2CH4N2S·C4H6O4 | γ = 66.168 (3)° |
Mr = 270.33 | V = 311.01 (12) Å3 |
TriclinicP1 | Z = 1 |
a = 6.030 (1) Å | Mo Kα radiation |
b = 7.511 (2) Å | µ = 0.43 mm−1 |
c = 8.414 (2) Å | T = 100 K |
α = 65.613 (4)° | 0.30 × 0.20 × 0.15 mm |
β = 70.475 (3)° |
Bruker SMART CCD area-detector diffractometer | 1288 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 1091 reflections with I > 2σ(I) |
Tmin = 0.754, Tmax = 1.000 | Rint = 0.023 |
2389 measured reflections |
R[F2 > 2σ(F2)] = 0.040 | 0 restraints |
wR(F2) = 0.103 | Only H-atom displacement parameters refined |
S = 1.11 | Δρmax = 0.46 e Å−3 |
1288 reflections | Δρmin = −0.39 e Å−3 |
81 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. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 2.8226 (42) x - 3.7160 (39) y + 2.9421 (79) z = 0.6123 (87) * 0.0022 (0.0005) S1 * -0.0076 (0.0018) C1 * 0.0027 (0.0006) N1 * 0.0027 (0.0006) N2 Rms deviation of fitted atoms = 0.0044 2.8882 (45) x - 3.6757 (65) y + 2.9054 (71) z = 1.0589 (83) Angle to previous plane (with approximate e.s.d.) = 0.82 (16) * -0.0117 (0.0007) O1 * -0.0425 (0.0015) O2 * -0.0136 (0.0021) C2 * 0.0296 (0.0010) C3 * 0.0117 (0.0007) O1_$1 * 0.0425 (0.0015) O2_$1 * 0.0136 (0.0021) C2_$1 * -0.0296 (0.0010) C3_$1 Rms deviation of fitted atoms = 0.0274 |
Refinement. This structure was solved and refined initially on the basis of the reduced unit cell with a = 6.030 (1), b = 7.495 (2), c = 8.414 (2) A and alpha = 98.334 (4), beta = 109.525 (3), gamma = 113.551 (3) °. and then re-refined with the unit cell adjusted for conformity with the same (type 1) setting used for the I-300 structure (see crystal data) and the indices subject to the (row-wise) transformation matrix (-1 0 0 / -1 - 1 0 / 0 0 1). |
x | y | z | Uiso*/Ueq | ||
S1 | 0.79627 (10) | 1.04454 (9) | 0.76423 (7) | 0.0222 (2) | |
O1 | 0.4253 (3) | 0.5868 (2) | 0.6801 (2) | 0.0263 (4) | |
O2 | 0.2484 (3) | 0.4119 (2) | 0.6241 (2) | 0.0231 (4) | |
N1 | 0.4667 (4) | 0.8560 (3) | 0.8425 (2) | 0.0261 (5) | |
H1 | 0.3993 | 0.7852 | 0.8221 | 0.047 (8)* | |
H2 | 0.4072 | 0.8901 | 0.9404 | 0.027 (7)* | |
N2 | 0.7414 (3) | 0.8572 (3) | 0.5804 (2) | 0.0221 (4) | |
H3 | 0.6704 | 0.7863 | 0.5635 | 0.037 (8)* | |
H4 | 0.8679 | 0.8919 | 0.5007 | 0.024 (6)* | |
C1 | 0.6578 (4) | 0.9115 (3) | 0.7258 (3) | 0.0184 (4) | |
C2 | 0.4115 (4) | 0.5047 (3) | 0.5893 (3) | 0.0214 (5) | |
C3 | 0.0801 (5) | 0.3967 (4) | 0.7968 (3) | 0.0283 (5) | |
H5 | 0.0138 | 0.5305 | 0.8158 | 0.048 (9)* | |
H6 | 0.1698 | 0.2939 | 0.8910 | 0.038 (7)* | |
H7 | −0.0563 | 0.3553 | 0.7997 | 0.039 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.0253 (3) | 0.0289 (3) | 0.0201 (3) | −0.0169 (2) | 0.0017 (2) | −0.0116 (2) |
O1 | 0.0334 (9) | 0.0273 (9) | 0.0271 (9) | −0.0158 (7) | −0.0038 (7) | −0.0126 (7) |
O2 | 0.0265 (8) | 0.0274 (9) | 0.0216 (8) | −0.0156 (7) | −0.0017 (7) | −0.0091 (7) |
N1 | 0.0308 (11) | 0.0368 (11) | 0.0219 (10) | −0.0233 (9) | 0.0067 (8) | −0.0170 (9) |
N2 | 0.0254 (10) | 0.0314 (11) | 0.0172 (10) | −0.0182 (9) | 0.0031 (8) | −0.0115 (8) |
C1 | 0.0201 (10) | 0.0181 (10) | 0.0178 (10) | −0.0083 (8) | −0.0026 (8) | −0.0053 (8) |
C2 | 0.0238 (11) | 0.0202 (11) | 0.0234 (11) | −0.0088 (9) | −0.0063 (9) | −0.0068 (9) |
C3 | 0.0316 (13) | 0.0325 (13) | 0.0255 (13) | −0.0176 (11) | −0.0030 (10) | −0.0084 (10) |
S1—C1 | 1.709 (2) | N2—C1 | 1.323 (3) |
O1—C2 | 1.202 (3) | N2—H3 | 0.8800 |
O2—C2 | 1.316 (3) | N2—H4 | 0.8800 |
O2—C3 | 1.458 (3) | C2—C2i | 1.535 (5) |
N1—C1 | 1.327 (3) | C3—H5 | 0.9800 |
N1—H1 | 0.8800 | C3—H6 | 0.9800 |
N1—H2 | 0.8800 | C3—H7 | 0.9800 |
C2—O2—C3 | 115.50 (17) | O1—C2—O2 | 126.7 (2) |
C1—N1—H1 | 120.0 | O1—C2—C2i | 123.4 (3) |
C1—N1—H2 | 120.0 | O2—C2—C2i | 110.0 (2) |
H1—N1—H2 | 120.0 | O2—C3—H5 | 109.5 |
C1—N2—H3 | 120.0 | O2—C3—H6 | 109.5 |
C1—N2—H4 | 120.0 | H5—C3—H6 | 109.5 |
H3—N2—H4 | 120.0 | O2—C3—H7 | 109.5 |
N2—C1—N1 | 118.0 (2) | H5—C3—H7 | 109.5 |
N2—C1—S1 | 120.96 (16) | H6—C3—H7 | 109.5 |
N1—C1—S1 | 120.99 (16) | ||
C3—O1—C2—C2i | −177.7 (3) | O2—C2—C2i—O1i | −0.2 (4) |
O1—C2—C2i—O2i | 0.2 (4) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.88 | 2.20 | 2.989 (2) | 150 |
N2—H3···O1 | 0.88 | 2.24 | 3.019 (2) | 148 |
N2—H3···O2i | 0.88 | 2.40 | 3.123 (2) | 139 |
N1—H2···S1ii | 0.88 | 2.53 | 3.405 (2) | 172 |
N2—H4···S1iii | 0.88 | 2.49 | 3.3494 (19) | 167 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+2, −z+2; (iii) −x+2, −y+2, −z+1. |
Experimental details
(I-300) | (I-100) | |
Crystal data | ||
Chemical formula | 2CH4N2S·C4H6O4 | 2CH4N2S·C4H6O4 |
Mr | 270.33 | 270.33 |
Crystal system, space group | TriclinicP1 | TriclinicP1 |
Temperature (K) | 300 | 100 |
a, b, c (Å) | 6.1010 (3), 7.6447 (4), 8.4463 (5) | 6.030 (1), 7.511 (2), 8.414 (2) |
α, β, γ (°) | 66.239 (3), 70.516 (3), 67.479 (3) | 65.613 (4), 70.475 (3), 66.168 (3) |
V (Å3) | 325.48 (3) | 311.01 (12) |
Z | 1 | 1 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.42 | 0.43 |
Crystal size (mm) | 0.30 × 0.20 × 0.15 | 0.30 × 0.20 × 0.15 |
Data collection | ||
Diffractometer | Bruker Nonius X8 APEXII 4K CCD diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.797, 1.000 | 0.754, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4488, 2151, 1463 | 2389, 1288, 1091 |
Rint | 0.019 | 0.023 |
(sin θ/λ)max (Å−1) | 0.786 | 0.662 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.041, 0.113, 1.02 | 0.040, 0.103, 1.11 |
No. of reflections | 2151 | 1288 |
No. of parameters | 81 | 81 |
H-atom treatment | Only H-atom displacement parameters refined | Only H-atom displacement parameters refined |
Δρmax, Δρmin (e Å−3) | 0.25, −0.21 | 0.46, −0.39 |
Computer programs: APEX2 (Bruker–Nonius, 2003), SMART (Bruker, 2004), SAINT (Bruker, 2003), SMART, SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), SHELXL97.
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.86 | 2.26 | 3.0413 (17) | 150 |
N2—H3···O1 | 0.86 | 2.30 | 3.0683 (19) | 149 |
N2—H3···O2i | 0.86 | 2.45 | 3.1498 (16) | 139 |
N1—H2···S1ii | 0.86 | 2.57 | 3.4292 (15) | 172 |
N2—H4···S1iii | 0.86 | 2.53 | 3.3791 (14) | 167 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+2, −z+2; (iii) −x+2, −y+2, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.88 | 2.20 | 2.989 (2) | 150 |
N2—H3···O1 | 0.88 | 2.24 | 3.019 (2) | 148 |
N2—H3···O2i | 0.88 | 2.40 | 3.123 (2) | 139 |
N1—H2···S1ii | 0.88 | 2.53 | 3.405 (2) | 172 |
N2—H4···S1iii | 0.88 | 2.49 | 3.3494 (19) | 167 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, −y+2, −z+2; (iii) −x+2, −y+2, −z+1. |
(I-300) | (I-100) | (II)a | |
C2—C2i | 1.525 (3) | 1.535 (5) | 1.534 (4) |
O1—C2 | 1.2029 (18) | 1.202 (3) | 1.186 (3) |
O2—C2 | 1.318 (2) | 1.316 (3) | 1.324 (3) |
O2—C3 | 1.452 (2) | 1.458 (3) | 1.451 (3) |
O1—C2—O2 | 126.07 (17) | 126.7 (2) | 126.2 (2) |
O1—C2—C2i | 123.5 (2) | 123.4 (3) | 124.1 (2) |
O2—C2—C2i | 110.40 (16) | 110.0 (2) | 109.6 (2) |
C2—O2—C3 | 116.52 (14) | 115.50 (17) | 115.5 (2) |
a Data for equivalent bonds and angles from Jones et al. (1989). Symmetry code: (i) -x + 1, -y + 1, -z + 1. |
Intermolecular interactions play a definitive role in crystal engineering. Indeed, the varied strength of hydrogen bonds plays a key role in designing new crystals. In this field, the crystal structures of complexes show a delicate interplay of strong and weak hydrogen bonds. Apart from the varied strength, their directional nature and flexibility can also be utilized to create new materials with specific physical properties. It is known that the melting point of dimethyl oxalate is 327 K and is higher than that of related carboxylic acid esters. This has been explained as being due to the stabilization of the crystal by weak intermolecular hydrogen bonds, i.e. C—H···O hydrogen bonds between the methyl groups and the carbonyl groups in this compound. Dimethyl oxalate (dmox) is the simplest molecule in the series of symmetric diesters and its structure is already known (Dougill & Jeffery, 1953; Jones et al., 1989). X-ray analysis of the compound at room temperature showed that the molecule has a planar trans–trans configuration. It crystallizes in space group P21/n with unit-cell parameters a = 3.891 (1), b = 11.879 (2), c = 6.213 (2) Å and β = 103.32 (2)°. To our knowledge, no complex of dmox has been reported to date.
Thiourea (tu) is known to form crystalline inclusion compounds with a range of guest molecules of appropriate size and shape (Takemoto & Sonoda, 1984; Hollingsworth & Harris, 1996). These compounds exhibit a wide range of interesting and important fundamental physico-chemical properties (Harris, 1990). A complex of diethyl oxalate (detox) with tu has been reported (Chitra et al., 2005) and is isostructural with the complex reported here. It is interesting to compare the geometric parameters and hydrogen bonding of the present complex, (I), with pure dmox, (II), and the tu:detox (2:1) complex, (III).
Data for (I) were obtained at 300 K, (I-300), and 100 K, (I-100), but on the basis of reduced unit cells differing in the choice of the unit-cell edge b. For ease of comparison of the structures, the 100 K unit cell and Miller indices were transformed for conformity with the 300 K case (see later). The asymmetric unit of (I) consists of one-half of a dmox molecule, which is completed by the operation of a crystallographic centre of symmetry, and a complete tu molecule (Fig. 1). The bond lengths and bond angles of the molecules in (I) are in the usual ranges and, as exemplified in Table 3 for dmox, insensitive to inclusion in the complex or temperature. The tu and dmox molecules in (I) are, in themselves, planar and, for the asymmetric unit used in both refinements, coplanar within 1°.
The molecules in (I) are interconnected by N—H···S and N—H···O hydrogen-bonds (Tables 1 and 2) to form sheets parallel to (111) (Fig. 2). The N—H···S hydrogen bonds connect the tu molecules to form zigzag chains. The N—H···O hydrogen bonds employ the O atoms of dmox as acceptors to interconnect adjacent chains of tu molecules and complete the connectivity within the layer. Precisely the same arrangement is found in the structure of (III) (Chitra et al., 2005). Complex (III) differs from (I) in having a larger cell edge a and longer N···S distances in the chains, somewhat more linear than they are in (I), of tu molecules in order to accommodate the larger detox molecule. The smaller size of the unit cell of (I) at 100 K compared with its size at 300 K is evident from values given in the crystal data tables below. The effect of cooling, bringing about closer packing of the molecules, is also evident in the change in the hydrogen-bond geometries, especially the D···A distances, in Tables 1 and 2. Assessment of the shrinkage of the unit cell upon cooling based upon the reduced cells used in data collection but not, as indicated above, for the refinement of the structure at 100 K exaggerates the effect. This is misleading because it fails to recognize that b is chosen differently in the two reduced cells. The disparity in the choice of b in the reduced cells creates an interesting situation for cell search algorithms which employ cell reduction as part of their search strategy.