organic compounds The molecular conformation of pentan-3-one studied in cholic acid pentan-3-one solvate

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1 organic compounds Acta Crystallographica Section C Crystal Structure Communications ISSN The molecular conformation of pentan-3-one studied in cholic acid pentan-3-one solvate in Fig. 1. Our redetermination fully confirms the conclusions of the earlier authors with respect to the host structure, but the previously published data cannot provide details about the conformation of the guest molecule. In contrast, our intensity data collected at low temperature and up to high resolution Irmgard Kalf and Ulli Englert* Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, Aachen, Germany Correspondence ullrich.englert@ac.rwth-aachen.de Received 14 March 2011 Accepted 4 May 2011 Online 12 May 2011 The crystal structure of cholic acid pentan-3-one (1/1), C 5 H 10 OC 24 H 40 O 5, has been determined in order to deduce the molecular conformation of the small volatile ketone. Data were collected at 100 K to a resolution of (sin )/ =0.91Å 1. The structure contains a hydrogen-bonded cholic acid host network, forming only van der Waals interactions with the guest pentan-3-one molecules. The ketone molecules are disordered on general positions, with two clearly identifiable conformations. The majority conformer exhibits approximate C 2 symmetry and is similar to that recently observed by microwave spectroscopy in the gas phase. Comment Many solvates of cholic acid have been studied, often with the focus on crystal engineering: Version 5.31 of the Cambridge Structural Database (CSD; Allen, 2002) contains 247 errorfree organic structures in which the steroid acts as a guest for small organic host molecules. We have recently identified cocrystallization with cholic acid as an effective strategy to obtain high-resolution data sets on low-melting compounds, provided the intensity data collections are performed at reasonably low temperatures. Crystals obtained with the odorants allyl acetate and isopropyl acetate have been of sufficient quality even for charge-density studies (Mouhib et al., 2011). We intended to obtain information about possible conformations of the small volatile molecule pentan-3-one, also known as diethyl ketone, in the solid state. In view of its relatively low melting point of ca 233 K and our previous successful experiments, we decided to grow cocrystals with cholic acid and to study the crystal structure of the title cocrystal, (I), at low temperature. The structure of (I) at room temperature has been reported previously (Caira et al., 1994a). The compound crystallizes in the space group P2 1 with lattice parameters similar to those of related compounds (Caira et al., 1994b). A displacement ellipsoid plot of the contents of the asymmetric unit is shown allow us to compare the conformation of the ketone in the solid to that in the gas phase. Although single crystals of (I) were well diffracting up to a resolution (sin )/ =0.91Å 1, the resulting intensity data are not suitable for a chargedensity study. After completion of the conventional refinement reported here, a difference Fourier synthesis shows local electron-density maxima centred on covalent bonds of the steroid host, in agreement with the expectation and in favour of a potential charge-density study. In the neighbourhood of the guest molecule, however, a less clear-cut and chemically not meaningful distribution is observed for the residual maxima, which precludes a more demanding interpretation of the electron density. Classical O HO hydrogen bonds link the cholic acid molecules into layers parallel to the (101) planes (Fig. 2 and Table 2). Pairs of the host molecules reside in a comparatively large cavity with a volume of 366 Å 3 (Spek, 2009). One of the ethyl substituents in the pentan-3-one molecule is disordered over two conformations with a (12):0.455 (12) ratio between the site occupancies. The majority conformation shown in Fig. 3(a) deviates only slightly from C 2 symmetry, in Figure 1 The molecular structure of (I), with displacement ellipsoids drawn at the 50% probability level. Atoms belonging to the minor conformer of pentan-3-one and all H atoms have been omitted for clarity. o206 # 2011 International Union of Crystallography doi: /s

2 organic compounds Experimental Single crystals of (I) were obtained by dissolving cholic acid (30 mg, 0.07 mmol) in pentan-3-one (10 ml) at 313 K. Slow evaporation over a period of ca 7 d at room temperature afforded colourless plates. The crystal fragment chosen for the diffraction experiment was cut to an appropriate size while covered with mother liquor and transferred directly to the stream of cold N 2 (100 K) on the diffractometer. Figure 2 Packing diagram of (I), viewed along [010], showing the hydrogenbonded layers of cholic acid host molecules in black and the pentan-3-one guest molecules in grey. Crystal data C 5 H 10 OC 24 H 40 O 5 M r = Monoclinic, P2 1 a = (7) Å b = (5) Å c = (8) Å = (3) Data collection Bruker SMART APEX CCD diffractometer measured reflections Refinement R[F 2 >2(F 2 )] = wr(f 2 ) = S = reflections 357 parameters 26 restraints V = (14) Å 3 Z =2 Mo K radiation = 0.08 mm 1 T = 100 K mm independent reflections 9042 reflections with I > 2(I) R int = H atoms treated by a mixture of independent and constrained refinement max = 0.69 e Å 3 min = 0.44 e Å 3 good agreement with the experimental results for the gasphase conformation obtained from Fourier transform microwave spectroscopy, and also with the expectation from theory (Nguyen & Stahl, 2011). The minority conformer (Fig. 3b) is less symmetrical and belongs to point group C 1. The only previous low-temperature crystal structure containing pentan- 3-one (Goldup et al., 2008) shows an unexpected C C C bond angle of 141 in one of the ethyl substituents and therefore does not allow one to deduce the conformation of this molecule reliably. Table 1 Selected geometric parameters (Å, ). O1 C (2) O2 C (2) O3 C (2) O4 C (2) O5 C (2) C1 C (3) C2 C (3) C3 C (3) O6 C25 C (3) O6 C25 C28A (3) C26 C25 C28A (3) O6 C25 C28B (5) O6 C (4) C25 C (5) C25 C28A (5) C25 C28B (7) C26 C (5) C28A C29A (10) C28B C29B (12) C26 C25 C28B (5) C25 C26 C (2) C25 C28A C29A (7) C29B C28B C (8) O6 C25 C26 C (5) O6 C25 C28A C29A 17.7 (9) O6 C25 C28B C29B 66.6 (12) Figure 3 The molecular conformations of pentan-3-one in (I), showing (a) the major conformer, similar to the gas-phase structure, and (b) the minor conformer. A total of 22 similarity restraints (C C distances, C C C angles and displacement parameters for split positions) were used to model the disordered ethyl group of the solvent molecule. Coordinates and isotropic displacement parameters were refined for H atoms attached to O atoms, with O H distances restrained to 0.85 (2) Å. H atoms attached to C atoms were treated as riding, with C H = 0.98 Å for CH 3,C H=0.99Åfor CH 2 and C H = 1.00 Å for CH groups, and with U iso (H) = 1.2 or 1.5U eq (C). Methyl groups were allowed to rotate about their local threefold axes. In the absence of significant anomalous scattering effects, the Flack (1983) parameter is indeterminate. The absolute structure is assigned on the basis of the known configuration of the chiral cholic acid molecule. Friedel pairs were not merged. Data collection: SMART (Bruker, 2001); cell refinement: SMART; data reduction: SAINT-Plus (Bruker, 1999); program(s) used to solve Kalf and Englert C 5 H 10 OC 24 H 40 O 5 o207

3 organic compounds Table 2 Hydrogen-bond geometry (Å, ). D HA D H HA DA D HA O1 H1O4 i 0.87 (3) 1.84 (3) (2) 160 (4) O3 H3O2 i 0.83 (2) 2.08 (2) (2) 160 (2) O4 H4O5 ii 0.86 (2) 1.81 (2) (19) 165 (2) O5 H5O3 ii 0.82 (2) 2.10 (3) (2) 157 (2) Symmetry codes: (i) x þ 1; y þ 1 2 ; z þ 2; (ii) x; y 1 2 ; z þ 1. 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. Halima Mouhib and Wolfgang Stahl are acknowledged for the fruitful co-operation in our project dedicated to the conformation of volatile compounds in the gas and solid phases. Supplementary data for this paper are available from the IUCr electronic archives (Reference: BI3016). Services for accessing these data are described at the back of the journal. References Allen, F. H. (2002). Acta Cryst. B58, Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA. Bruker (2001). SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Caira, M. R., Nassimbeni, L. R. & Scott, J. L. (1994a). J. Chem. Crystallogr. 24, Caira, M. R., Nassimbeni, L. R. & Scott, J. L. (1994b). J. Chem. Soc. Perkin Trans. 2, pp Flack, H. D. (1983). Acta Cryst. A39, Goldup, S. M., Leigh, D. A., Lusby, P. J., McBurney, R. T. & Slawin, A. M. Z. (2008). Angew. Chem. Int. Ed. 47, Mouhib, H., Jelisavac, D., Stahl, W., Wang, R., Kalf, I. & Englert, U. (2011). ChemPhysChem, 12, Nguyen, H. V. L. & Stahl, W. (2011). ChemPhysChem, doi: /cphc Sheldrick, G. M. (2008). Acta Cryst. A64, Spek, A. L. (2009). Acta Cryst. D65, o208 Kalf and Englert C 5 H 10 OC 24 H 40 O 5

4 [ The molecular conformation of pentan-3-one studied in cholic acid pentan-3- one solvate Irmgard Kalf and Ulli Englert Computing details Data collection: SMART (Bruker, 2001); cell refinement: SMART (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 1999); 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). cholic acid pentan-3-one (1/1) Crystal data C 5 H 10 O C 24 H 40 O 5 M r = Monoclinic, P2 1 Hall symbol: P 2yb a = (7) Å b = (5) Å c = (8) Å β = (3) V = (14) Å 3 Z = 2 Data collection Bruker SMART APEX CCD diffractometer Radiation source: Incoatec microsource Multilayer optics monochromator ω scans measured reflections independent reflections Refinement Refinement on F 2 Least-squares matrix: full R[F 2 > 2σ(F 2 )] = wr(f 2 ) = S = reflections 357 parameters 26 restraints Primary atom site location: structure-invariant direct methods F(000) = 544 D x = Mg m 3 Mo Kα radiation, λ = Å Cell parameters from 4097 reflections θ = µ = 0.08 mm 1 T = 100 K Fragment, colourless mm 9042 reflections with I > 2σ(I) R int = θ max = 40.4, θ min = 1.7 h = k = l = Secondary atom site location: difference Fourier map Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement w = 1/[σ 2 (F o2 ) + (0.085P) P] where P = (F o 2 + 2F c2 )/3 (Δ/σ) max = Δρ max = 0.69 e Å 3 Δρ min = 0.44 e Å 3 sup-1

5 Special details 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 F 2 against ALL reflections. The weighted R-factor wr and goodness of fit S are based on F 2, conventional R-factors R are based on F, with F set to zero for negative F 2. The threshold expression of F 2 > σ(f 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 ) x y z U iso */U eq Occ. (<1) O (14) (18) (11) (3) H (2) (5) (3) (11)* O (14) (19) (12) (3) O (13) (17) (10) (3) H (18) (3) (19) (6)* O (12) (16) (10) (3) H (2) (2) (2) (7)* O (14) (17) (10) (3) H (2) (3) (19) (7)* C (18) (2) (14) (4) C (19) (3) (16) (4) H2A * H2B * C (18) (3) (15) (4) H3A * H3B * C (16) (2) (13) (3) H4A * C (17) (2) (13) (3) H5A * C (16) (2) (13) (3) C (16) (2) (13) (3) H * C (16) (2) (13) (3) H8A * H8B * C (16) (2) (13) (3) H * C (17) (2) (13) (3) H * C (17) (2) (13) (3) H * C (18) (2) (14) (4) H12A * H12B * sup-2

6 C (16) (2) (13) (3) H * C (17) (2) (13) (3) H14A * H14B * C (17) (2) (13) (3) H * C (17) (2) (14) (3) H16A * H16B * C (17) (2) (14) (3) H17A * H17B * C (16) (2) (13) (3) C (18) (3) (15) (4) H19A * H19B * H19C * C (16) (2) (13) (3) H * C (18) (2) (14) (4) H21A * H21B * C (18) (2) (15) (4) H22A * H22B * C (17) (2) (14) (4) H23A * H23B * H23C * C (19) (2) (15) (4) H24A * H24B * H24C * O (18) (3) (16) (6) C (2) (5) (2) (7) C (2) (3) (3) (7) H26A * H26B * C (2) (4) (2) (7) H27A * H27B * H27C * C28A (5) (8) (3) (15) (12) H28A * (12) H28B * (12) C29A (13) (14) (8) (2) (12) H29A * (12) sup-3

7 H29B * (12) H29C * (12) C28B (7) (15) (6) (2) (12) H28C * (12) H28D * (12) C29B (18) (2) (10) (3) (12) H29D * (12) H29E * (12) H29F * (12) Atomic displacement parameters (Å 2 ) U 11 U 22 U 33 U 12 U 13 U 23 O (9) (6) (7) (6) (6) (5) O (9) (6) (8) (6) (6) (6) O (8) (6) (6) (5) (5) (5) O (8) (5) (6) (5) (5) (5) O (9) (6) (5) (6) (5) (5) C (10) (8) (7) (7) (7) (6) C (12) (10) (10) (8) (8) (8) C (10) (8) (8) (7) (7) (6) C (9) (7) (7) (6) (6) (6) C (10) (7) (7) (6) (6) (6) C (9) (6) (7) (6) (6) (5) C (10) (6) (7) (6) (6) (5) C (10) (6) (7) (6) (6) (6) C (9) (6) (7) (6) (6) (5) C (10) (6) (7) (6) (6) (5) C (10) (6) (7) (6) (6) (5) C (11) (7) (8) (7) (7) (6) C (9) (7) (7) (6) (6) (6) C (10) (6) (7) (6) (7) (6) C (10) (7) (7) (6) (6) (6) C (10) (7) (8) (6) (7) (6) C (10) (7) (8) (7) (7) (6) C (9) (7) (7) (6) (6) (6) C (11) (9) (9) (8) (8) (7) C (10) (6) (7) (6) (6) (5) C (11) (7) (8) (7) (7) (6) C (11) (7) (9) (7) (7) (6) C (10) (7) (7) (7) (7) (6) C (11) (8) (8) (7) (8) (6) O (12) (16) (11) (11) (9) (10) C (14) (2) (13) (13) (10) (13) C (15) (12) (18) (10) (13) (12) C (17) (12) (18) (11) (14) (12) C28A (3) (3) (2) (2) (19) (2) C29A (4) (5) (3) (4) (3) (3) sup-4

8 C28B (4) (6) (4) (4) (3) (4) C29B (7) (9) (4) (7) (4) (5) Geometric parameters (Å, º) O1 C (2) C15 C (2) O1 H (18) C15 H O2 C (2) C16 C (3) O3 C (2) C16 H16A 0.99 O3 H (17) C16 H16B 0.99 O4 C (2) C17 C (3) O4 H (17) C17 H17A 0.99 O5 C (2) C17 H17B 0.99 O5 H (17) C18 C (3) C1 C (3) C19 H19A 0.98 C2 C (3) C19 H19B 0.98 C2 H2A 0.99 C19 H19C 0.98 C2 H2B 0.99 C20 C (2) C3 C (3) C20 H C3 H3A 0.99 C21 C (3) C3 H3B 0.99 C21 H21A 0.99 C4 C (3) C21 H21B 0.99 C4 C (3) C22 H22A 0.99 C4 H4A 1.00 C22 H22B 0.99 C5 C (3) C23 H23A 0.98 C5 C (3) C23 H23B 0.98 C5 H5A 1.00 C23 H23C 0.98 C6 C (3) C24 H24A 0.98 C6 C (2) C24 H24B 0.98 C6 C (2) C24 H24C 0.98 C7 C (3) O6 C (4) C7 H C25 C (5) C8 C (2) C25 C28A (5) C8 H8A 0.99 C25 C28B (7) C8 H8B 0.99 C26 C (5) C9 C (2) C26 H26A 0.99 C9 C (3) C26 H26B 0.99 C9 H C27 H27A 0.98 C10 C (3) C27 H27B 0.98 C10 C (2) C27 H27C 0.98 C10 H C28A C29A (10) C11 C (3) C28A H28A 0.99 C11 H C28A H28B 0.99 C12 C (3) C29A H29A 0.98 C12 H12A 0.99 C29A H29B 0.98 C12 H12B 0.99 C29A H29C 0.98 C13 C (3) C28B C29B (12) C13 C (3) C28B H28C 0.99 sup-5

9 C13 H C28B H28D 0.99 C14 C (3) C29B H29D 0.98 C14 H14A 0.99 C29B H29E 0.98 C14 H14B 0.99 C29B H29F 0.98 C1 O1 H1 102 (3) C16 C15 H C7 O3 H (18) C15 C16 C (15) C11 O4 H4 110 (2) C15 C16 H16A C15 O5 H5 108 (2) C17 C16 H16A O2 C1 O (2) C15 C16 H16B O2 C1 C (19) C17 C16 H16B O1 C1 C (17) H16A C16 H16B C1 C2 C (17) C16 C17 C (15) C1 C2 H2A C16 C17 H17A C3 C2 H2A C18 C17 H17A C1 C2 H2B C16 C17 H17B C3 C2 H2B C18 C17 H17B H2A C2 H2B H17A C17 H17B C2 C3 C (16) C19 C18 C (15) C2 C3 H3A C19 C18 C (15) C4 C3 H3A C17 C18 C (15) C2 C3 H3B C19 C18 C (15) C4 C3 H3B C17 C18 C (15) H3A C3 H3B C9 C18 C (15) C24 C4 C (15) C18 C19 H19A C24 C4 C (17) C18 C19 H19B C5 C4 C (15) H19A C19 H19B C24 C4 H4A C18 C19 H19C C5 C4 H4A H19A C19 H19C C3 C4 H4A H19B C19 H19C C4 C5 C (15) C10 C20 C (15) C4 C5 C (15) C10 C20 C (15) C6 C5 C (15) C21 C20 C (14) C4 C5 H5A C10 C20 H C6 C5 H5A C21 C20 H C22 C5 H5A C6 C20 H C23 C6 C (15) C20 C21 C (15) C23 C6 C (14) C20 C21 H21A C20 C6 C (14) C22 C21 H21A C23 C6 C (15) C20 C21 H21B C20 C6 C (14) C22 C21 H21B C7 C6 C (15) H21A C21 H21B O3 C7 C (14) C21 C22 C (15) O3 C7 C (14) C21 C22 H22A C8 C7 C (15) C5 C22 H22A O3 C7 H C21 C22 H22B C8 C7 H C5 C22 H22B C6 C7 H H22A C22 H22B sup-6

10 C7 C8 C (15) C6 C23 H23A C7 C8 H8A C6 C23 H23B C9 C8 H8A H23A C23 H23B C7 C8 H8B C6 C23 H23C C9 C8 H8B H23A C23 H23C H8A C8 H8B H23B C23 H23C C8 C9 C (14) C4 C24 H24A C8 C9 C (15) C4 C24 H24B C10 C9 C (14) H24A C24 H24B C8 C9 H C4 C24 H24C C10 C9 H H24A C24 H24C C18 C9 H H24B C24 H24C C20 C10 C (15) O6 C25 C (3) C20 C10 C (14) O6 C25 C28A (3) C11 C10 C (14) C26 C25 C28A (3) C20 C10 H O6 C25 C28B (5) C11 C10 H C26 C25 C28B (5) C9 C10 H C25 C26 C (2) O4 C11 C (15) C25 C26 H26A O4 C11 C (15) C27 C26 H26A C12 C11 C (16) C25 C26 H26B O4 C11 H C27 C26 H26B C12 C11 H H26A C26 H26B C10 C11 H C26 C27 H27A C11 C12 C (15) C26 C27 H27B C11 C12 H12A H27A C27 H27B C13 C12 H12A C26 C27 H27C C11 C12 H12B H27A C27 H27C C13 C12 H12B H27B C27 H27C H12A C12 H12B C25 C28A C29A (7) C14 C13 C (15) C25 C28A H28A C14 C13 C (14) C29A C28A H28A C12 C13 C (15) C25 C28A H28B C14 C13 H C29A C28A H28B C12 C13 H H28A C28A H28B C18 C13 H C29B C28B C (8) C15 C14 C (16) C29B C28B H28C C15 C14 H14A C25 C28B H28C C13 C14 H14A C29B C28B H28D C15 C14 H14B C25 C28B H28D C13 C14 H14B H28C C28B H28D H14A C14 H14B C28B C29B H29D O5 C15 C (16) C28B C29B H29E O5 C15 C (15) H29D C29B H29E C14 C15 C (15) C28B C29B H29F O5 C15 H H29D C29B H29F C14 C15 H H29E C29B H29F sup-7

11 O2 C1 C2 C (3) C14 C15 C16 C (2) O1 C1 C2 C (18) C15 C16 C17 C (2) C1 C2 C3 C (18) C16 C17 C18 C (16) C2 C3 C4 C (2) C16 C17 C18 C (2) C2 C3 C4 C (17) C16 C17 C18 C (2) C24 C4 C5 C (2) C8 C9 C18 C (19) C3 C4 C5 C (16) C10 C9 C18 C (18) C24 C4 C5 C (17) C8 C9 C18 C (19) C3 C4 C5 C (2) C10 C9 C18 C (14) C4 C5 C6 C (2) C8 C9 C18 C (14) C22 C5 C6 C (17) C10 C9 C18 C (17) C4 C5 C6 C (15) C14 C13 C18 C (17) C22 C5 C6 C (16) C12 C13 C18 C (2) C4 C5 C6 C (2) C14 C13 C18 C (2) C22 C5 C6 C (15) C12 C13 C18 C (16) C23 C6 C7 O (15) C14 C13 C18 C (19) C20 C6 C7 O (19) C12 C13 C18 C (19) C5 C6 C7 O (2) C11 C10 C20 C (2) C23 C6 C7 C (18) C9 C10 C20 C (14) C20 C6 C7 C (18) C11 C10 C20 C (14) C5 C6 C7 C (14) C9 C10 C20 C (18) O3 C7 C8 C (18) C23 C6 C20 C (19) C6 C7 C8 C (19) C7 C6 C20 C (19) C7 C8 C9 C (2) C5 C6 C20 C (14) C7 C8 C9 C (14) C23 C6 C20 C (2) C8 C9 C10 C (18) C7 C6 C20 C (15) C18 C9 C10 C (14) C5 C6 C20 C (17) C8 C9 C10 C (16) C10 C20 C21 C (15) C18 C9 C10 C (19) C6 C20 C21 C (19) C20 C10 C11 O (18) C20 C21 C22 C5 8.5 (2) C9 C10 C11 O (19) C4 C5 C22 C (16) C20 C10 C11 C (14) C6 C5 C22 C (19) C9 C10 C11 C (19) O6 C25 C26 C (5) O4 C11 C12 C (19) C28A C25 C26 C (4) C10 C11 C12 C (2) C28B C25 C26 C (5) C11 C12 C13 C (2) O6 C25 C28A C29A 17.7 (9) C11 C12 C13 C (2) C26 C25 C28A C29A (6) C12 C13 C14 C (16) C28B C25 C28A C29A 55.7 (9) C18 C13 C14 C (2) O6 C25 C28B C29B 66.6 (12) C13 C14 C15 O (15) C26 C25 C28B C29B (10) C13 C14 C15 C (2) C28A C25 C28B C29B 55.7 (12) O5 C15 C16 C (16) Hydrogen-bond geometry (Å, º) D H A D H H A D A D H A O1 H1 O4 i 0.87 (3) 1.84 (3) (2) 160 (4) O3 H3 O2 i 0.83 (2) 2.08 (2) (2) 160 (2) sup-8

12 O4 H4 O5 ii 0.86 (2) 1.81 (2) (19) 165 (2) O5 H5 O3 ii 0.82 (2) 2.10 (3) (2) 157 (2) Symmetry codes: (i) x+1, y+1/2, z+2; (ii) x, y 1/2, z+1. sup-9