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Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

A new hydrate of magnesium carbonate, MgCO3·6H2O

aInstitute of Inorganic Chemistry, TU Bergakademie Freiberg, Leipziger Strasse 29, D-09599 Freiberg, Germany
*Correspondence e-mail: christine.rincke@chemie.tu-freiberg.de

Edited by V. Langer, Chalmers University of Technology, Sweden (Received 30 October 2019; accepted 4 February 2020; online 13 February 2020)

During investigations of the formation of hydrated magnesium carbonates, a sample of the previously unknown magnesium carbonate hexa­hydrate (MgCO3·6H2O) was synthesized in an aqueous solution at 273.15 K. The crystal structure consists of edge-linked isolated pairs of Mg(CO3)(H2O)4 octa­hedra and noncoordinating water mol­ecules, and exhibits similarities to NiCO3·5.5H2O (hellyerite). The recorded X-ray diffraction pattern and the Raman spectra confirmed the formation of a new phase and its transformation to magnesium carbonate trihydrate (MgCO3·3H2O) at room temperature.

1. Introduction

In the MgO–H2O–CO2 system, besides the thermodynami­cally stable MgCO3 (magnesite), a variety of hydrated mag­nesium carbonates are known, which can be divided in basic magnesium carbonates, containing OH ions [Mg5(CO3)4(OH)2·nH2O and Mg(CO3)(OH)2·nH2O], and neutral mag­nesium carbonates with the com­position MgCO3·nH2O (Hopkinson et al., 2012[Hopkinson, L., Kristova, P., Rutt, K. & Cressey, G. (2012). Geochim. Cosmochim. Acta, 76, 1-13.]; Jauffret et al., 2015[Jauffret, G., Morrison, J. & Glasser, F. P. (2015). J. Therm. Anal. Calorim. 122, 601-609.]). All these phases are of significant relevance in various technological processes, in geological explorations, mineral conversion in the sequestration of CO2 and in biomineralization (Chaka & Felmy, 2014[Chaka, A. M. & Felmy, A. R. (2014). J. Phys. Chem. A, 118, 7469-7488.]). Nevertheless, there are many open questions with respect to the conditions of formation, the characterization, the crystal structure and the stability of higher hydrated neutral magnesium carbonates (Hänchen et al., 2008[Hänchen, M., Prigiobbe, V., Baciocchi, R. & Mazzotti, M. (2008). Chem. Eng. Sci. 63, 1012-1028.]; Hopkinson et al., 2012[Hopkinson, L., Kristova, P., Rutt, K. & Cressey, G. (2012). Geochim. Cosmochim. Acta, 76, 1-13.]; Rincke, 2018[Rincke, C. (2018). Dissertation, TU Bergakademie Freiberg. Freiberg, Germany.]).

The most frequently investigated neutral magnesium carbonate hydrate, MgCO3·3H2O (mineral name: nesquehonite), can be synthesized in the temperature range between 283.15 and 325.15 K (Giester et al., 2000[Giester, G., Lengauer, C. L. & Rieck, B. (2000). Mineral. Petrol. 70, 153-163.]; Frost & Palmer, 2011[Frost, R. L. & Palmer, S. J. (2011). Spectrochim. Acta A Mol. Biomol. Spectrosc. 78, 1255-1260.]; Jauffret et al., 2015[Jauffret, G., Morrison, J. & Glasser, F. P. (2015). J. Therm. Anal. Calorim. 122, 601-609.]; Hänchen et al., 2008[Hänchen, M., Prigiobbe, V., Baciocchi, R. & Mazzotti, M. (2008). Chem. Eng. Sci. 63, 1012-1028.]; Gloss, 1937[Gloss, G. (1937). Dissertation. Friedrich-Wilhelms-University of Berlin, Germany.]; Takahashi & Hokoku, 1927[Takahashi, G. & Hokoku, E. S. (1927). Bull. Imp. Hyg. Lab. 29, 165-251.]; Hopkinson et al., 2012[Hopkinson, L., Kristova, P., Rutt, K. & Cressey, G. (2012). Geochim. Cosmochim. Acta, 76, 1-13.]).

At lower temperatures, the penta­hydrate, i.e. MgCO3·5H2O (mineral name: lansfordite), is known. Its crystal structure (monoclinic space group P21/m) was determined by Liu et al. (1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]) from a synthetic sample and by Nestola et al. (2017[Nestola, F., Kasatkin, A. V., Potapov, S. S., Chervyatsova, O. Y. & Lanza, A. (2017). Miner. Mag. 81, 1063-1071.]) from a mineral. Several possibilities are described to synthesize lansfordite (Ming & Franklin, 1985[Ming, D. W. & Franklin, W. T. (1985). Soil Sci. Soc. Am. J. 49, 1303-1308.]; Liu et al., 1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]). In order to obtain large prismatic crystals, CO2 can be bubbled through an aqueous suspension of MgO and, subsequently, the crystallization can be carried out in the filtered solution at low temperature (Liu et al., 1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]). However, the authors (Liu et al., 1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]) did not provide information about the exact CO2 pressure, the regime of temperature, the concentration of magnesium ions in the solution and the time needed for crystallization. According to Ming & Franklin (1985[Ming, D. W. & Franklin, W. T. (1985). Soil Sci. Soc. Am. J. 49, 1303-1308.]), these factors are important to avoid the formation of nesquehonite. Furthermore, the solubility of lansfordite is highly dependent on temperature and on CO2 pressure (Königsberger et al., 1999[Königsberger, E., Königsberger, L.-C. & Gamsjäger, H. (1999). Geochim. Cosmochim. Acta, 63, 3105-3119.]; Takahashi & Hokoku, 1927[Takahashi, G. & Hokoku, E. S. (1927). Bull. Imp. Hyg. Lab. 29, 165-251.]; Rincke, 2018[Rincke, C. (2018). Dissertation, TU Bergakademie Freiberg. Freiberg, Germany.]). Besides that, there are contradictory statements about the temperature and the rate of conversion of the penta­hydrate to the trihydrate. Some research groups have recorded a transition temperature between 283.15 and 288.15 K (Takahashi & Hokoku, 1927[Takahashi, G. & Hokoku, E. S. (1927). Bull. Imp. Hyg. Lab. 29, 165-251.]; Gloss, 1937[Gloss, G. (1937). Dissertation. Friedrich-Wilhelms-University of Berlin, Germany.]; Yanaťeva & Rassonskaya, 1961[Yanaťeva, O. K. & Rassonskaya, I. S. (1961). Zh. Neorg. Khim. 6, 1424-1430.]; Hill et al., 1982[Hill, R. J., Canterford, J. H. & Moyle, F. J. (1982). Miner. Mag. 46, 453-457.]; Langmuir, 1965[Langmuir, D. (1965). J. Geol. 73, 730-754.]; Ming & Franklin, 1985[Ming, D. W. & Franklin, W. T. (1985). Soil Sci. Soc. Am. J. 49, 1303-1308.]), while others observed the stability of synthesized and natural samples of lansfordite at room temperature over a period of a few months (Liu et al., 1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]; Nestola et al., 2017[Nestola, F., Kasatkin, A. V., Potapov, S. S., Chervyatsova, O. Y. & Lanza, A. (2017). Miner. Mag. 81, 1063-1071.]). Neutral magnesium carbonates with a water content greater than five units per formula are not known up to now. Such highly hydrated neutral carbonates of other bivalent metal ions have been found only for calcium, i.e. CaCO3·6H2O (ikaite; Hesse et al., 1983[Hesse, K. F., Kueppers, H. & Suess, E. (1983). Z. Kristallogr. 163, 227-231.]), and nickel, i.e. NiCO3·5.5H2O (hellyerite; Bette et al., 2016[Bette, S., Rincke, C., Dinnebier, R. E. & Voigt, W. (2016). Z. Anorg. Allg. Chem. 642, 652-659.]). Our own investigations should elucidate the conditions of formation of the magnesium carbonate hydrates.

2. Experimental

2.1. Synthesis and crystallization

To obtain crystals of MgCO3·6H2O suitable for single-crystal diffraction analysis (see V11 in Table S1 of the supporting information), carbon dioxide was bubbled through a suspension of magnesium oxide in deionized water (3.1 g, Magnesia M2329, p.a.) for 22 h at 273.15 K. After that, the solution was filtered and stored without stirring at 273.15 K for 16 d until the product crystallized. The product was filtered off for characterization by powder X-ray diffraction and Raman spectroscopy. For intensity data collection, a prismatic crystal of MgCO3·6H2O was recovered from a droplet of its mother liquor and mounted rapidly in the cold (200 K) stream of nitro­gen gas of the diffractometer.

2.2. Powder X-ray diffraction

The powder X-ray diffraction (PXRD) patterns were taken for phase identification with a Bruker D8 Discover laboratory powder diffrac­tometer in the Bragg–Brentano set-up (Cu Kα1 radiation, Vantec 1 detector). The samples were prepared as flat plates and measured at low temperatures (about 273.15 K) with a home-made cooling box (Rincke, 2018[Rincke, C. (2018). Dissertation, TU Bergakademie Freiberg. Freiberg, Germany.]).

2.3. Raman spectroscopy

The Raman spectra were recorded shortly after synthesis with a Bruker RFS100/S FT spectrometer at room temperature (Nd/YAG laser, wavelength of the laser = 1064 nm).

2.4. Refinement

Crystal data, data collection and structure refinement details are given in Table 1[link]. The positions of the H atoms could be located from residual electron-density maxima after further refinement and were refined isotropically.

Table 1
Experimental details

Crystal data
Chemical formula MgCO3·6H2O
Mr 192.42
Crystal system, space group Orthorhombic, Pbam
Temperature (K) 200
a, b, c (Å) 12.3564 (18), 6.5165 (7), 9.9337 (11)
V3) 799.87 (17)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.24
Crystal size (mm) 0.7 × 0.55 × 0.15
 
Data collection
Diffractometer Stoe IPDS 2T
Absorption correction Integration (Coppens, 1970[Coppens, P. (1970). Crystallographic Computing, edited by F. R. Ahmed, S. R. Hall & C. P. Huber, pp. 255-270. Copenhagen: Munksgaard.])
Tmin, Tmax 0.694, 0.887
No. of measured, independent and observed [I > 2σ(I)] reflections 8319, 1143, 965
Rint 0.036
(sin θ/λ)max−1) 0.687
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.029, 0.085, 1.18
No. of reflections 1143
No. of parameters 83
H-atom treatment All H-atom parameters refined
Δρmax, Δρmin (e Å−3) 0.23, −0.26
Computer programs: X-AREA (Stoe & Cie, 2015[Stoe & Cie (2015). X-AREA and X-RED. Stoe & Cie, Darmstadt, Germany.]), X-RED (Stoe & Cie, 2015[Stoe & Cie (2015). X-AREA and X-RED. Stoe & Cie, Darmstadt, Germany.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2016 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), DIAMOND (Brandenburg, 2017[Brandenburg, K. (2017). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

3. Results and discussion

3.1. Conditions of formation and characterization of magnesium carbonate hexa­hydrate

On the basis of the information of Liu et al. (1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]) for the formation of lansfordite, CO2 was bubbled through aqueous MgO suspensions with various concentrations. After filtration of the solution, the product crystallized at low temperature (273.15–278.15 K), while the CO2 pressure was decreased by slow degassing of the CO2 and the solubility product of the carbonate was exceeded. The detailed experimental conditions are given in the supporting information (see Table S1). Characterization of the product with PXRD revealed that nesquehonite is formed at low MgO concentrations, while an unknown phase crystallizes from the solutions at higher Mg2+ concentrations, near the solubility of lansfordite at p(CO2) = 1 bar [m(Mg2+) = 0.386 mol kg−1(H2O) at 273.15 K] (Königsberger et al., 1999[Königsberger, E., Königsberger, L.-C. & Gamsjäger, H. (1999). Geochim. Cosmochim. Acta, 63, 3105-3119.]; Rincke, 2018[Rincke, C. (2018). Dissertation, TU Bergakademie Freiberg. Freiberg, Germany.]). Fig. 1[link] shows the PXRD pattern of the new product phase in com­parison with the reference data for MgCO3·3H2O and MgCO3·5H2O. The com­position of this unknown phase was determined by single-crystal diffraction as MgCO3·6H2O. The penta­hydrate was not found in our investigations.

[Figure 1]
Figure 1
Powder XRD pattern of MgCO3·6H2O at low temperature (∼273.15 K, Cu Kα radiation) and reference data for MgCO3·3H2O (PDF 20-0669) and MgCO3·5H2O (PDF 80-1641).

Large prismatic crystals of MgCO3·6H2O were obtained while using a longer time of crystallization of 16 d (see V11 in Table S1 of the supporting information). These crystals, which are partly inter­grown, convert in a few minutes at room temperature into the typical needles of MgCO3·3H2O (Fig. 2[link]). The process of phase transformation could also be seen by means of Raman spectroscopy (Fig. 3[link]). The assignments of the band positions in com­parison with the spectra of nesquehonite and lansfordite are given in the supporting information (Table S2).

[Figure 2]
Figure 2
Microscopic image of prismatic MgCO3·6H2O crystals (framed in black) which are partly inter­grown. The red-framed crystals are the typical needles of the transformation product MgCO3·3H2O.
[Figure 3]
Figure 3
Raman spectrum of MgCO3·6H2O (black) in com­parison with the transformation product MgCO3·3H2O (red) after storage at room temperature.

3.2. Crystal structure of magnesium carbonate hexa­hydrate

Magnesium carbonate hexa­hydrate crystallizes in the ortho­rhom­bic space group Pbam (No. 55). The Mg1 atom is located on a twofold axis of symmetry. Atoms C1, O1 and O5, and the water mol­ecule H6A—O6—H6B are positioned on a mirror plane.

Isolated pairs of edge-linked Mg(CO3)2(H2O)4 octa­hedra are the main building blocks in the crystal structure (Fig. 4[link]). The crystal structure differs significantly from those of MgCO3·3H2O and MgCO3·5H2O; MgCO3·3H2O exhibits a monoclinic crystal structure consisting of infinite chains along [010], formed by corner-sharing MgO6 octa­hedra and CO3 groups, which link three MgO6 octa­hedra by two common corners and one edge (Giester et al., 2000[Giester, G., Lengauer, C. L. & Rieck, B. (2000). Mineral. Petrol. 70, 153-163.]). In the monoclinic crystal structure of MgCO3·5H2O, the characteristic building units are isolated octa­hedra of [Mg(CO3)2(H2O)4]2− and [Mg(H2O)6]2+ (Liu et al., 1990[Liu, B., Zhou, X., Cui, X. & Tang, J. (1990). Sci. China Ser. B, 33, 1350-1356.]).

[Figure 4]
Figure 4
Illustration of the main building block in the crystal structure of MgCO3·6H2O, showing isolated pairs of edge-linked Mg(CO3)2(H2O)4 octa­hedra [symmetry codes: (ii) −x + 1, −y, z; (iii) −x + 1, −y, −z + 1; (iv) x, y, −z + 1].

The MgO octa­hedra in MgCO3·6H2O are slightly distorted (Table 2[link]).

Table 2
Selected geometric parameters (Å, °)

Mg1—O1 2.1043 (8) C1—O4 1.2840 (11)
Mg1—O2 2.0859 (8) C1—O1 1.2978 (17)
Mg1—O3 2.0672 (8)    
       
O3—Mg1—O2 86.12 (3) O1—Mg1—O1ii 81.25 (5)
O2—Mg1—O2i 95.28 (5) O4—C1—O4iii 120.41 (13)
O3—Mg1—O1 91.46 (4) O4—C1—O1 119.79 (6)
O2—Mg1—O1 91.74 (3) Mg1—O1—Mg1ii 98.75 (5)
Symmetry codes: (i) -x+1, -y, z; (ii) -x+1, -y, -z+1; (iii) x, y, -z+1.

The carbonate units are linked in a monodentate manner to two magnesium ions across the O1 atom. They are planar and exhibit C2v symmetry, because the C1—O1 bond is a little longer than the C1—O4 bond. Furthermore, the O1—C1—O4 angle is a little narrower than the O4—C1—O4iv angle (see Table 2[link] for numerical data and symmetry code).

The main building blocks are arranged in a sheet-like pattern, perpendicular to the c axis (Figs. 5[link]a and 5b). Within a sheet, every second main building unit is shifted along the [[1 \over 2], [1 \over 2], 0] direction and rotated by 90°. Consequently, a zigzag-like stacking order results (Fig. 5[link]c). The main building units in a sheet are linked by hydrogen bridging bonds (Fig. 6[link] and Table 3[link]). The sheets are separated by layers of noncoordinating water mol­ecules in the (001) plane.

Table 3
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O5—H5⋯O2iii 0.812 (18) 2.068 (19) 2.8545 (12) 162.9 (18)
O6—H6B⋯O5ii 0.87 (3) 1.93 (3) 2.7662 (19) 161 (2)
O6—H6A⋯O5iv 0.76 (3) 1.99 (3) 2.7137 (19) 160 (3)
O3—H3B⋯O4v 0.788 (19) 2.025 (19) 2.8055 (12) 170.7 (18)
O3—H3A⋯O4vi 0.93 (2) 1.77 (2) 2.7001 (12) 174.1 (18)
O2—H2B⋯O4iii 0.92 (2) 1.70 (2) 2.5868 (12) 162 (2)
O2—H2A⋯O6 0.84 (2) 1.91 (2) 2.7417 (13) 168.7 (18)
Symmetry codes: (ii) -x+1, -y, -z+1; (iii) x, y, -z+1; (iv) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]; (v) [x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]; (vi) -x+1, -y+1, -z+1.
[Figure 5]
Figure 5
Projection of the crystal structure of MgCO3·6H2O (a) in the a direction, (b) in the b direction and (c) in the c direction.
[Figure 6]
Figure 6
Part of the crystal structure of MgCO3·6H2O, showing the intra­layer hydrogen bonds (dashed lines).

All the atoms of the noncoordinating H6A—O6—H6B mol­ecule are located in the (001) plane, whereas in the H5—O5—H5i mol­ecule, only the O5 atom is situated in this plane (Fig. 7[link]). The (001) plane is also the mirror plane of this mol­ecule. The noncoordinating water mol­ecules are linked by hydrogen bridging bonds both in the (001) plane among themselves and with the MgO octa­hedra. Thus, the crystal structure is three-dimensional crosslinked (Fig. 7[link]).

[Figure 7]
Figure 7
Part of the crystal structure of MgCO3·6H2O, showing the inter­layer hydrogen bonds (dashed lines). The (001) plane is shown in blue.

3.3. Comparison with crystal structures of other carbonate hydrates of bivalent metal ions

Other neutral carbonate hydrates of bivalent metal ions with a water content greater than five units per formula are only known for calcium (CaCO3·6H2O) and nickel (NiCO3·5.5H2O). Like the title com­pound, these phases can be synthesized only at low temperatures of about 273.15 K and are transformed at room temperature to CaCO3 (Coleyshaw et al., 2003[Coleyshaw, E. E., Crump, G. & Griffith, W. P. (2003). Spectrochim. Acta A Mol. Biomol. Spectrosc. 59, 2231-2239.]) and amorphous nickel carbonate (Bette et al., 2016[Bette, S., Rincke, C., Dinnebier, R. E. & Voigt, W. (2016). Z. Anorg. Allg. Chem. 642, 652-659.]; Rincke, 2018[Rincke, C. (2018). Dissertation, TU Bergakademie Freiberg. Freiberg, Germany.]), respectively.

The crystal structure of CaCO3·6H2O is significantly different from that of MgCO3·6H2O for the very reason that the coordination number of the cation in CaCO3·6H2O is eight and not six as in MgCO3·6H2O (Dickens & Brown, 1970[Dickens, B. & Brown, W. E. (1970). Inorg. Chem. 9, 480-486.]; Hesse et al., 1983[Hesse, K. F., Kueppers, H. & Suess, E. (1983). Z. Kristallogr. 163, 227-231.]).

However, the radii of nickel and magnesium ions are very similar and actually the crystal structures of NiCO3·5.5H2O and MgCO3·6H2O exhibit similarities. Both crystal structures consist of isolated edge-linked pairs of M(CO3)(H2O)4 (M = Mg or Ni), which are the main building units and are arranged in sheets, together with noncoordinating water mol­ecules, perpendicular to the c axis. The symmetry of NiCO3·5.5H2O is lower; it crystallizes in the monoclinic group P2/n. As a consequence, there are two crystallographically different Ni atoms. In contrast to MgCO3·6H2O, in NiCO3·5.5H2O, the NiO octa­hedra of Ni2 are not rotated by 90° (Bette et al., 2016[Bette, S., Rincke, C., Dinnebier, R. E. & Voigt, W. (2016). Z. Anorg. Allg. Chem. 642, 652-659.]).

4. Conclusion

A new neutral magnesium carbonate with the previously unknown high water content of six units per formula, i.e. MgCO3·6H2O, was produced by passing gaseous CO2 through an aqueous suspension of MgO and storing the filtered solution at 273.15 K. The X-ray diffraction pattern and Raman spectra confirmed the formation of the new phase and its transformation to MgCO3·3H2O. MgCO3·5H2O was not found in our study. Obviously, the formation conditions of magnesium carbonate hydrates depend on the concentration of the MgO suspension, the CO2 pressure, the temperature regime and the time of storage. Therefore, it would be useful to carry out further systematic investigations on the chemical kinetics of the formation of the magnesium carbonate hydrates.

The crystal structure of MgCO3·6H2O differs significantly from the other known magnesium carbonate hydrates, because the main building units are isolated pairs of edge-linked Mg(CO3)(H2O)4 octa­hedra and free water mol­ecules in the (001) plane, but it exhibits similarities to the nickel salt, NiCO3·5.5H2O (hellyerite).

Supporting information


Computing details top

Data collection: X-AREA (Stoe & Cie, 2015); cell refinement: X-AREA (Stoe & Cie, 2015); data reduction: X-RED (Stoe & Cie, 2015); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2017); software used to prepare material for publication: publCIF (Westrip, 2010).

Magnesium carbonate hexahysrate top
Crystal data top
MgCO3·6H2ODx = 1.598 Mg m3
Mr = 192.42Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PbamCell parameters from 9707 reflections
a = 12.3564 (18) Åθ = 2.7–27.0°
b = 6.5165 (7) ŵ = 0.24 mm1
c = 9.9337 (11) ÅT = 200 K
V = 799.87 (17) Å3Prism, colorless
Z = 40.7 × 0.55 × 0.15 mm
F(000) = 408
Data collection top
Stoe IPDS 2T
diffractometer
1143 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus965 reflections with I > 2σ(I)
Plane graphite monochromatorRint = 0.036
Detector resolution: 6.67 pixels mm-1θmax = 29.2°, θmin = 3.3°
rotation method scansh = 1616
Absorption correction: integration
(Coppens, 1970)
k = 78
Tmin = 0.694, Tmax = 0.887l = 1311
8319 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.029All H-atom parameters refined
wR(F2) = 0.085 w = 1/[σ2(Fo2) + (0.0483P)2 + 0.1805P]
where P = (Fo2 + 2Fc2)/3
S = 1.18(Δ/σ)max < 0.001
1143 reflectionsΔρmax = 0.23 e Å3
83 parametersΔρmin = 0.26 e Å3
0 restraints
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Mg10.5000000.0000000.33923 (5)0.01691 (15)
C10.61245 (11)0.3494 (2)0.5000000.0176 (3)
O10.55574 (8)0.18176 (16)0.5000000.0189 (2)
O20.55982 (7)0.20756 (12)0.19775 (8)0.02241 (19)
O30.35722 (6)0.16456 (13)0.32879 (9)0.0230 (2)
O40.64098 (6)0.43100 (12)0.61217 (8)0.0228 (2)
O50.40386 (10)0.3240 (2)1.0000000.0294 (3)
O60.69316 (10)0.0585 (2)0.0000000.0277 (3)
H2A0.6079 (17)0.167 (3)0.1436 (18)0.039 (5)*
H2B0.5913 (18)0.305 (3)0.252 (3)0.057 (6)*
H3A0.3553 (17)0.302 (3)0.3545 (18)0.043 (5)*
H3B0.2986 (16)0.124 (3)0.3454 (16)0.033 (4)*
H6A0.755 (2)0.062 (4)0.0000000.039 (7)*
H6B0.678 (2)0.071 (5)0.0000000.040 (7)*
H50.4421 (17)0.310 (3)0.9341 (18)0.048 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Mg10.0166 (2)0.0156 (3)0.0185 (2)0.00105 (17)0.0000.000
C10.0141 (6)0.0140 (6)0.0246 (6)0.0010 (5)0.0000.000
O10.0199 (5)0.0155 (5)0.0213 (5)0.0044 (4)0.0000.000
O20.0227 (4)0.0227 (4)0.0219 (4)0.0016 (3)0.0023 (3)0.0024 (3)
O30.0174 (4)0.0188 (4)0.0328 (4)0.0004 (3)0.0011 (3)0.0025 (3)
O40.0230 (4)0.0174 (4)0.0281 (4)0.0031 (3)0.0031 (3)0.0031 (3)
O50.0228 (6)0.0363 (7)0.0290 (6)0.0013 (5)0.0000.000
O60.0220 (6)0.0280 (6)0.0331 (6)0.0022 (5)0.0000.000
Geometric parameters (Å, º) top
Mg1—O12.1043 (8)O3—H3A0.93 (2)
Mg1—O22.0859 (8)O3—H3B0.788 (19)
Mg1—O32.0672 (8)O5—H50.812 (18)
C1—O41.2840 (11)O5—H5i0.812 (18)
C1—O11.2978 (17)O6—H6A0.76 (3)
O2—H2A0.84 (2)O6—H6B0.87 (3)
O2—H2B0.92 (2)
O3—Mg1—O286.12 (3)O3ii—Mg1—Mg1iii92.87 (3)
O2—Mg1—O2ii95.28 (5)O3—Mg1—Mg1iii92.87 (3)
O3—Mg1—O191.46 (4)O2ii—Mg1—Mg1iii132.36 (3)
O2—Mg1—O191.74 (3)O2—Mg1—Mg1iii132.36 (3)
O1—Mg1—O1iii81.25 (5)O1iii—Mg1—Mg1iii40.63 (2)
O4—C1—O4iv120.41 (13)O1—Mg1—Mg1iii40.63 (2)
O4—C1—O1119.79 (6)O4iv—C1—O1119.79 (6)
Mg1—O1—Mg1iii98.75 (5)C1—O1—Mg1iii130.58 (2)
O3ii—Mg1—O3174.25 (5)C1—O1—Mg1130.58 (2)
O3ii—Mg1—O2ii86.12 (3)Mg1—O2—H2A118.3 (12)
O3—Mg1—O2ii90.01 (3)Mg1—O2—H2B101.9 (14)
O3ii—Mg1—O290.01 (3)H2A—O2—H2B106.9 (19)
O3ii—Mg1—O1iii91.46 (4)Mg1—O3—H3A120.5 (13)
O3—Mg1—O1iii92.91 (4)Mg1—O3—H3B126.9 (13)
O2ii—Mg1—O1iii91.74 (3)H3A—O3—H3B103.9 (18)
O2—Mg1—O1iii172.90 (4)H5—O5—H5i107 (3)
O3ii—Mg1—O192.91 (4)H6A—O6—H6B105 (3)
O2ii—Mg1—O1172.91 (4)
Symmetry codes: (i) x, y, z+2; (ii) x+1, y, z; (iii) x+1, y, z+1; (iv) x, y, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O5—H5···O2iv0.812 (18)2.068 (19)2.8545 (12)162.9 (18)
O6—H6B···O5iii0.87 (3)1.93 (3)2.7662 (19)161 (2)
O6—H6A···O5v0.76 (3)1.99 (3)2.7137 (19)160 (3)
O3—H3B···O4vi0.788 (19)2.025 (19)2.8055 (12)170.7 (18)
O3—H3A···O4vii0.93 (2)1.77 (2)2.7001 (12)174.1 (18)
O2—H2B···O4iv0.92 (2)1.70 (2)2.5868 (12)162 (2)
O2—H2A···O60.84 (2)1.91 (2)2.7417 (13)168.7 (18)
Symmetry codes: (iii) x+1, y, z+1; (iv) x, y, z+1; (v) x+1/2, y+1/2, z+1; (vi) x1/2, y+1/2, z+1; (vii) x+1, y+1, z+1.
 

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