supplementary materials


HTML versionpdf versioncif file3d viewstructure factorssupplementary materialsCIF check reportsimilar papers Open access

pv2070 scheme

Acta Cryst. (2008). E64, o694    [ doi:10.1107/S1600536808006120 ]

2,5-Dimethylhexane-2,5-diyl bis(4-nitrophenyl) dicarbonate

S. Nawazish Ali, S. Begum, M. A. Winnik and A. J. Lough

Abstract top

The title structure, C22H24N2O10, contains two independent centrosymmetric molecules. The only significant difference between the molecules is the dihedral angle between the unique carbonate group (-O-CO2-) and the benzene ring, the values being 77.35 (8) and 66.42 (8)°. The crystal structure is stabilized by weak intermolecular C-H...O hydrogen bonds.

Comment top

For background information and relevant references see Ali et al. (2008). The title structure contains two independent centrosymmetric molecules labelled with suffix A and suffix B to indicate molecules A and B (see Figs. 1 and 2). The only significant difference between them is a slight difference in the dihedral angles in each molecule, between the unique carbonate group (O1/O2/O3/C7) and benzene ring (C1—C6) which is 77.35 (8)° for molecule A and 66.42 (8)° for molecule B. In addition to weak intramolecular C—H···O hydrogen bonds which may, in part, affect the conformation of each molecule, the crystal structure is stabilized by weak intermolecular hydrogen bonds (see Fig. 3).

Related literature top

For related literature, see: Ali et al. (2008).

Experimental top

A solution of 4-nitrophenylchloroformate (2.02 g, 10.0 mmol) in dry dichloromethane (25 ml) was added dropwise via a 100 ml separatory funnel into a solution of 2,5-dimethyl-2,5-hexanediol (0.74 g, 5.0 mmol) in anhydrous pyridine (0.70 g, 0.72 ml, 8.8 mmol) and dry dichloromethane (15 ml) in a 100 ml round-bottom flask. A white suspension appeared which was allowed to stir gently at room temperature for 14 h. After this time more dry dichloromethane (40 ml) was added, which dissolved the suspension and then the reaction mixture was stirred for another 6 h. Then it was quenched by adding deionized water (40 ml). The reaction mixture was transferred to a separatory funnel (250 ml), and the lower organic phase was removed. The aqueous phase was washed with dichloromethane (25 ml x 2), and all the dichloromethane solutions were combined. These were then washed with deionized water (40 ml x 2), a 1.0% solution of acetic acid (40 ml x 3) and once more with deionized water (30 ml x 2), and then dried over anhydrous magnesium sulfate and filtered. After filtration, the solvent was removed by rotary evaporator. The product was dried in air overnight in a fume hood and then in a vacuum oven for 24 h at room temperature (< 1 Torr). The desired product was obtained in a good yield (29.4 g, 90.1%) as a white solid; the product was recrystallized in dichloromethane. X-ray quality crystals were obtained after the slow evaporation of a solution of the title compound at room temperature.

Refinement top

All hydrogen atoms were placed in calculated positions with C—H = 0.95 - 0.99 Å and they were included in the refinement in the riding-model approximation with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C) for methyl C atoms.

Computing details top

Data collection: COLLECT (Nonius, 2002); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of molecule A showing displacement ellipsoids drawn at the 30% probability level [symmetry code: (a) -x + 1, -y + 1, -z]
[Figure 2] Fig. 2. The molecular structure of molecule B showing displacement ellipsoids drawn at the 30% probability level. [symmetry code: (b) -x + 2, -y - 1, -z + 1]
[Figure 3] Fig. 3. Part of the crystal structure with weak C—H···O hydrogen bonds shown as dashed lines.
2,5-Dimethylhexane-2,5-diyl bis(4-nitrophenyl) dicarbonate top
Crystal data top
C22H24N2O10Z = 2
Mr = 476.43F000 = 500
Triclinic, P1Dx = 1.410 Mg m−3
Hall symbol: -P 1Mo Kα radiation
λ = 0.71073 Å
a = 8.1829 (4) ÅCell parameters from 9940 reflections
b = 11.7024 (5) Åθ = 2.8–27.5º
c = 11.8928 (6) ŵ = 0.11 mm−1
α = 92.717 (3)ºT = 150 (2) K
β = 98.886 (2)ºNeedle, colourless
γ = 92.952 (3)º0.34 × 0.25 × 0.14 mm
V = 1121.92 (9) Å3
Data collection top
Bruker–Nonius KappaCCD
diffractometer		5069 independent reflections
Radiation source: fine-focus sealed tube3571 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.047
Detector resolution: 9 pixels mm-1θmax = 27.5º
T = 150(2) Kθmin = 2.8º
φ scans and ω scans with κ offsetsh = −10→10
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)		k = −15→15
Tmin = 0.803, Tmax = 0.985l = −15→15
9940 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)] = 0.050H-atom parameters constrained
wR(F2) = 0.132  w = 1/[σ2(Fo2) + (0.0508P)2 + 0.4455P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max = 0.001
5069 reflectionsΔρmax = 0.23 e Å−3
311 parametersΔρmin = −0.28 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
C22H24N2O10γ = 92.952 (3)º
Mr = 476.43V = 1121.92 (9) Å3
Triclinic, P1Z = 2
a = 8.1829 (4) ÅMo Kα
b = 11.7024 (5) ŵ = 0.11 mm−1
c = 11.8928 (6) ÅT = 150 (2) K
α = 92.717 (3)º0.34 × 0.25 × 0.14 mm
β = 98.886 (2)º
Data collection top
Bruker–Nonius KappaCCD
diffractometer		5069 independent reflections
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)		3571 reflections with I > 2σ(I)
Tmin = 0.803, Tmax = 0.985Rint = 0.047
9940 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.050311 parameters
wR(F2) = 0.132H-atom parameters constrained
S = 1.04Δρmax = 0.23 e Å−3
5069 reflectionsΔρmin = −0.28 e Å−3
Special details top

Experimental. multi-scan from symmetry-related measurements SORTAV (Blessing 1995)

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
O1A0.45560 (16)0.14403 (11)0.12248 (12)0.0314 (3)
O2A0.19552 (18)0.20327 (12)0.11199 (15)0.0434 (4)
O3A0.40180 (16)0.30199 (10)0.04414 (12)0.0287 (3)
O4A0.3070 (2)−0.32743 (12)0.32493 (14)0.0421 (4)
O5A0.33546 (19)−0.21668 (14)0.47827 (13)0.0415 (4)
N1A0.3299 (2)−0.23269 (14)0.37471 (15)0.0307 (4)
C1A0.4142 (2)0.05054 (15)0.18498 (16)0.0250 (4)
C2A0.3979 (3)0.06818 (16)0.29791 (18)0.0310 (5)
H2AA0.40710.14370.33230.037*
C3A0.3682 (2)−0.02484 (17)0.36098 (17)0.0299 (4)
H3AA0.3569−0.01460.43910.036*
C4A0.3553 (2)−0.13300 (15)0.30750 (16)0.0238 (4)
C5A0.3715 (2)−0.15112 (16)0.19471 (16)0.0273 (4)
H5AA0.3621−0.22650.16020.033*
C6A0.4016 (2)−0.05742 (16)0.13248 (17)0.0277 (4)
H6AA0.4135−0.06760.05450.033*
C7A0.3338 (2)0.21770 (15)0.09375 (17)0.0279 (4)
C8A0.3008 (2)0.39869 (15)0.00122 (17)0.0267 (4)
C9A0.2301 (3)0.45775 (16)0.09795 (18)0.0333 (5)
H9AA0.13590.41060.11570.050*
H9AB0.19300.53270.07510.050*
H9AC0.31580.46810.16560.050*
C10A0.1670 (3)0.35357 (17)−0.09497 (19)0.0351 (5)
H10A0.08440.3054−0.06460.053*
H10B0.21640.3080−0.15080.053*
H10C0.11330.4180−0.13190.053*
C11A0.4289 (2)0.47525 (15)−0.04470 (16)0.0267 (4)
H11A0.47520.4303−0.10370.032*
H11B0.37220.5393−0.08220.032*
O1B0.96232 (16)−0.15529 (11)0.35566 (12)0.0303 (3)
O2B0.70189 (17)−0.19261 (12)0.39066 (14)0.0420 (4)
O3B0.91508 (15)−0.30493 (10)0.44521 (11)0.0261 (3)
O4B0.8268 (2)0.33919 (12)0.20273 (13)0.0450 (4)
O5B0.82071 (18)0.25161 (11)0.03819 (12)0.0338 (3)
N1B0.8330 (2)0.25233 (13)0.14248 (14)0.0272 (4)
C1B0.9163 (2)−0.05454 (15)0.30242 (17)0.0252 (4)
C2B0.9283 (2)−0.05045 (15)0.18834 (17)0.0274 (4)
H2BA0.9575−0.11590.14710.033*
C3B0.8973 (2)0.05059 (15)0.13453 (16)0.0263 (4)
H3BA0.90310.05530.05570.032*
C4B0.8580 (2)0.14393 (14)0.19799 (16)0.0235 (4)
C5B0.8458 (2)0.14058 (16)0.31213 (16)0.0265 (4)
H5BA0.81840.20640.35350.032*
C6B0.8747 (2)0.03886 (16)0.36517 (17)0.0285 (4)
H6BA0.86590.03350.44350.034*
C7B0.8420 (2)−0.21728 (15)0.39835 (17)0.0265 (4)
C8B0.8149 (2)−0.39774 (15)0.49142 (16)0.0238 (4)
C9B0.6938 (2)−0.45765 (16)0.39468 (18)0.0313 (5)
H9BA0.6058−0.40660.36930.047*
H9BB0.6450−0.52780.42110.047*
H9BC0.7521−0.47730.33100.047*
C10B0.7291 (3)−0.34772 (17)0.58539 (18)0.0326 (5)
H10D0.6399−0.30110.55210.049*
H10E0.8095−0.29980.63960.049*
H10F0.6825−0.41010.62510.049*
C11B0.9494 (2)−0.47459 (15)0.54251 (16)0.0253 (4)
H11C1.0257−0.42940.60310.030*
H11D0.8965−0.53810.57870.030*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O1A0.0291 (7)0.0220 (7)0.0461 (9)0.0043 (5)0.0117 (6)0.0132 (6)
O2A0.0266 (8)0.0360 (8)0.0714 (12)0.0030 (6)0.0125 (8)0.0251 (8)
O3A0.0282 (7)0.0183 (6)0.0414 (8)0.0018 (5)0.0084 (6)0.0096 (6)
O4A0.0550 (10)0.0235 (8)0.0503 (10)−0.0004 (7)0.0155 (8)0.0077 (7)
O5A0.0457 (9)0.0531 (10)0.0296 (8)0.0092 (7)0.0114 (7)0.0165 (7)
N1A0.0301 (9)0.0307 (9)0.0337 (10)0.0059 (7)0.0079 (7)0.0117 (8)
C1A0.0237 (10)0.0199 (9)0.0322 (11)0.0028 (7)0.0047 (8)0.0081 (8)
C2A0.0342 (11)0.0217 (9)0.0377 (12)0.0015 (8)0.0089 (9)−0.0037 (8)
C3A0.0324 (11)0.0332 (11)0.0253 (10)0.0048 (8)0.0073 (8)0.0013 (8)
C4A0.0219 (9)0.0231 (9)0.0269 (10)0.0035 (7)0.0033 (8)0.0072 (8)
C5A0.0338 (11)0.0201 (9)0.0277 (10)0.0021 (8)0.0035 (8)0.0013 (8)
C6A0.0332 (11)0.0268 (10)0.0236 (10)0.0015 (8)0.0050 (8)0.0043 (8)
C7A0.0301 (11)0.0194 (9)0.0347 (11)0.0008 (8)0.0062 (9)0.0047 (8)
C8A0.0292 (10)0.0183 (9)0.0332 (11)0.0034 (7)0.0041 (8)0.0078 (8)
C9A0.0367 (12)0.0233 (10)0.0425 (13)0.0021 (8)0.0138 (10)0.0039 (9)
C10A0.0339 (11)0.0282 (10)0.0414 (13)−0.0031 (9)0.0008 (10)0.0046 (9)
C11A0.0311 (10)0.0199 (9)0.0295 (11)−0.0015 (8)0.0061 (8)0.0057 (8)
O1B0.0283 (7)0.0230 (7)0.0421 (8)0.0046 (5)0.0088 (6)0.0145 (6)
O2B0.0258 (8)0.0334 (8)0.0699 (11)0.0072 (6)0.0095 (7)0.0238 (8)
O3B0.0249 (7)0.0193 (6)0.0347 (8)0.0021 (5)0.0038 (6)0.0096 (6)
O4B0.0749 (12)0.0198 (7)0.0374 (9)0.0108 (7)−0.0020 (8)−0.0018 (6)
O5B0.0410 (8)0.0312 (8)0.0286 (8)0.0025 (6)0.0017 (6)0.0096 (6)
N1B0.0316 (9)0.0214 (8)0.0275 (9)0.0006 (7)0.0003 (7)0.0060 (7)
C1B0.0226 (9)0.0185 (9)0.0352 (11)0.0024 (7)0.0043 (8)0.0092 (8)
C2B0.0299 (10)0.0189 (9)0.0340 (11)0.0022 (8)0.0065 (8)0.0011 (8)
C3B0.0288 (10)0.0239 (9)0.0266 (10)0.0000 (8)0.0056 (8)0.0041 (8)
C4B0.0247 (9)0.0176 (9)0.0278 (10)0.0011 (7)0.0016 (8)0.0057 (7)
C5B0.0311 (10)0.0213 (9)0.0278 (10)0.0053 (8)0.0048 (8)0.0025 (8)
C6B0.0319 (11)0.0274 (10)0.0281 (10)0.0041 (8)0.0081 (8)0.0065 (8)
C7B0.0276 (10)0.0211 (9)0.0313 (11)0.0029 (8)0.0037 (8)0.0068 (8)
C8B0.0261 (10)0.0176 (9)0.0286 (10)0.0000 (7)0.0067 (8)0.0041 (7)
C9B0.0285 (11)0.0262 (10)0.0382 (12)0.0015 (8)0.0016 (9)0.0020 (9)
C10B0.0363 (12)0.0293 (10)0.0346 (12)0.0070 (9)0.0110 (9)0.0034 (9)
C11B0.0310 (10)0.0194 (9)0.0260 (10)0.0036 (7)0.0042 (8)0.0043 (8)
Geometric parameters (Å, °) top
O1A—C7A1.366 (2)O1B—C7B1.367 (2)
O1A—C1A1.407 (2)O1B—C1B1.406 (2)
O2A—C7A1.190 (2)O2B—C7B1.187 (2)
O3A—C7A1.316 (2)O3B—C7B1.317 (2)
O3A—C8A1.498 (2)O3B—C8B1.502 (2)
O4A—N1A1.223 (2)O4B—N1B1.223 (2)
O5A—N1A1.230 (2)O5B—N1B1.228 (2)
N1A—C4A1.469 (2)N1B—C4B1.467 (2)
C1A—C6A1.374 (3)C1B—C2B1.378 (3)
C1A—C2A1.377 (3)C1B—C6B1.381 (3)
C2A—C3A1.383 (3)C2B—C3B1.387 (2)
C2A—H2AA0.9500C2B—H2BA0.9500
C3A—C4A1.381 (3)C3B—C4B1.378 (3)
C3A—H3AA0.9500C3B—H3BA0.9500
C4A—C5A1.376 (3)C4B—C5B1.379 (3)
C5A—C6A1.384 (2)C5B—C6B1.387 (2)
C5A—H5AA0.9500C5B—H5BA0.9500
C6A—H6AA0.9500C6B—H6BA0.9500
C8A—C10A1.511 (3)C8B—C9B1.516 (3)
C8A—C9A1.519 (3)C8B—C10B1.519 (3)
C8A—C11A1.525 (3)C8B—C11B1.528 (2)
C9A—H9AA0.9800C9B—H9BA0.9800
C9A—H9AB0.9800C9B—H9BB0.9800
C9A—H9AC0.9800C9B—H9BC0.9800
C10A—H10A0.9800C10B—H10D0.9800
C10A—H10B0.9800C10B—H10E0.9800
C10A—H10C0.9800C10B—H10F0.9800
C11A—C11Ai1.520 (4)C11B—C11Bii1.521 (4)
C11A—H11A0.9900C11B—H11C0.9900
C11A—H11B0.9900C11B—H11D0.9900
C7A—O1A—C1A116.31 (14)C7B—O1B—C1B117.15 (14)
C7A—O3A—C8A120.17 (14)C7B—O3B—C8B120.21 (14)
O4A—N1A—O5A123.51 (16)O4B—N1B—O5B123.32 (15)
O4A—N1A—C4A118.20 (16)O4B—N1B—C4B118.17 (16)
O5A—N1A—C4A118.28 (17)O5B—N1B—C4B118.51 (15)
C6A—C1A—C2A121.84 (16)C2B—C1B—C6B122.14 (16)
C6A—C1A—O1A118.27 (17)C2B—C1B—O1B117.05 (16)
C2A—C1A—O1A119.75 (17)C6B—C1B—O1B120.58 (17)
C1A—C2A—C3A119.51 (18)C1B—C2B—C3B119.05 (17)
C1A—C2A—H2AA120.2C1B—C2B—H2BA120.5
C3A—C2A—H2AA120.2C3B—C2B—H2BA120.5
C4A—C3A—C2A118.28 (18)C4B—C3B—C2B118.51 (17)
C4A—C3A—H3AA120.9C4B—C3B—H3BA120.7
C2A—C3A—H3AA120.9C2B—C3B—H3BA120.7
C5A—C4A—C3A122.46 (16)C3B—C4B—C5B122.79 (16)
C5A—C4A—N1A118.76 (16)C3B—C4B—N1B118.54 (16)
C3A—C4A—N1A118.74 (17)C5B—C4B—N1B118.65 (16)
C4A—C5A—C6A118.76 (17)C4B—C5B—C6B118.48 (17)
C4A—C5A—H5AA120.6C4B—C5B—H5BA120.8
C6A—C5A—H5AA120.6C6B—C5B—H5BA120.8
C1A—C6A—C5A119.15 (18)C1B—C6B—C5B119.02 (18)
C1A—C6A—H6AA120.4C1B—C6B—H6BA120.5
C5A—C6A—H6AA120.4C5B—C6B—H6BA120.5
O2A—C7A—O3A129.64 (17)O2B—C7B—O3B130.08 (17)
O2A—C7A—O1A124.14 (16)O2B—C7B—O1B124.12 (16)
O3A—C7A—O1A106.22 (15)O3B—C7B—O1B105.79 (15)
O3A—C8A—C10A109.33 (15)O3B—C8B—C9B109.34 (14)
O3A—C8A—C9A110.37 (15)O3B—C8B—C10B110.06 (14)
C10A—C8A—C9A112.18 (17)C9B—C8B—C10B112.45 (16)
O3A—C8A—C11A101.78 (14)O3B—C8B—C11B101.83 (14)
C10A—C8A—C11A110.03 (16)C9B—C8B—C11B113.03 (15)
C9A—C8A—C11A112.64 (16)C10B—C8B—C11B109.62 (15)
C8A—C9A—H9AA109.5C8B—C9B—H9BA109.5
C8A—C9A—H9AB109.5C8B—C9B—H9BB109.5
H9AA—C9A—H9AB109.5H9BA—C9B—H9BB109.5
C8A—C9A—H9AC109.5C8B—C9B—H9BC109.5
H9AA—C9A—H9AC109.5H9BA—C9B—H9BC109.5
H9AB—C9A—H9AC109.5H9BB—C9B—H9BC109.5
C8A—C10A—H10A109.5C8B—C10B—H10D109.5
C8A—C10A—H10B109.5C8B—C10B—H10E109.5
H10A—C10A—H10B109.5H10D—C10B—H10E109.5
C8A—C10A—H10C109.5C8B—C10B—H10F109.5
H10A—C10A—H10C109.5H10D—C10B—H10F109.5
H10B—C10A—H10C109.5H10E—C10B—H10F109.5
C11Ai—C11A—C8A114.72 (19)C11Bii—C11B—C8B114.71 (19)
C11Ai—C11A—H11A108.6C11Bii—C11B—H11C108.6
C8A—C11A—H11A108.6C8B—C11B—H11C108.6
C11Ai—C11A—H11B108.6C11Bii—C11B—H11D108.6
C8A—C11A—H11B108.6C8B—C11B—H11D108.6
H11A—C11A—H11B107.6H11C—C11B—H11D107.6
Symmetry codes: (i) −x+1, −y+1, −z; (ii) −x+2, −y−1, −z+1.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C5A—H5AA···O5Biii0.952.593.112 (2)115
C5B—H5BA···O5Aiv0.952.523.205 (2)129
C11A—H11B···O3Ai0.992.532.888 (2)101
C11A—H11B···O4Bi0.992.543.502 (2)165
C11B—H11C···O4Bv0.992.583.546 (2)164
C11B—H11D···O3Bii0.992.492.862 (2)102
Symmetry codes: (iii) −x+1, −y, −z; (iv) −x+1, −y, −z+1; (i) −x+1, −y+1, −z; (v) −x+2, −y, −z+1; (ii) −x+2, −y−1, −z+1.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C5A—H5AA···O5Bi0.952.593.112 (2)115
C5B—H5BA···O5Aii0.952.523.205 (2)129
C11A—H11B···O3Aiii0.992.532.888 (2)101
C11A—H11B···O4Biii0.992.543.502 (2)165
C11B—H11C···O4Biv0.992.583.546 (2)164
C11B—H11D···O3Bv0.992.492.862 (2)102
Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y, −z+1; (iii) −x+1, −y+1, −z; (iv) −x+2, −y, −z+1; (v) −x+2, −y−1, −z+1.
Acknowledgements top

The authors acknowledge the Higher Education Commission (HEC) of Pakistan, Materials and Manufacturing Ontario (MMO), Canada, NSERC Canada and the University of Toronto for funding.

references
References top

Ali, S. N., Begum, S., Winnik, M. A. & Lough, A. J. (2008). Acta Cryst. E64, o281–?.

Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435–?.

Blessing, R. H. (1995). Acta Cryst. A51, 33–38.

Nonius (2002). COLLECT. Nonius BV, Delft, The Netherlands.

Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.