(IUCr) Redetermination of the hexagonal struvite analogue Cs[Mg(OH2)6](PO4)

Volume 64
Part 8
Page i50
August 2008

Received 16 July 2008
Accepted 23 July 2008
Online 31 July 2008

Key indicators
Single-crystal X-ray study
T = 293 K
Mean (Mg-O) = 0.004 Å
R = 0.016
wR = 0.034
Data-to-parameter ratio = 9.4
Details

Redetermination of the hexagonal struvite analogue Cs[Mg(OH₂)₆](PO₄)

Matthias Weil ^a ^*

^aInstitute for Chemical Technologies and Analytics, Division of Structural Chemistry, Vienna University of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria
Correspondence e-mail: mweil@mail.zserv.tuwien.ac.at

The structure of the hexagonal modification of caesium hexaaquamagnesium phosphate has been redetermined from single-crystal X-ray data. The previous refinement from photographic data [Ferrari, Calvaca & Nardelli (1955). Gazz. Chim. Ital. 85, 1232-1238] was basically confirmed, but with all H atoms located and with all non H-atoms refined with anisotropic displacement parameters. The structure can be derived from the NiAs structure type: the PO₄ tetrahedra (3m. symmetry) are on the Ni positions and the complex [Mg(OH₂)₆] octahedra (3m. symmetry) are on the As positions. The building units are connected to each other by hydrogen bonds. The Cs⁺ cations (3m. symmetry) are located in the voids of this arrangement and exhibit a distorted cuboctahedral 12-coordination by the O atoms of the water molecules.

Related literature

The crystal structure of struvite, NH₄[Mg(OH₂)₆](PO₄), was reported by Whitaker & Jeffery (1970a,b). Structure determinations of the hexagonal and cubic forms of Cs[Mg(OH₂)₆](PO₄) were performed by Ferrari et al. (1955) and Massa et al. (2003), respectively. Crystal growth of struvite-like compounds using the gel diffusion technique was reported by Banks et al. (1975). For general background, see: Flack (1983).

Experimental

Crystal data

Cs[Mg(H₂O)₆](PO₄)
M_r = 360.29
Hexagonal, P 6₃ m c
a = 6.8827 (8) Å
c = 11.9188 (16) Å
V = 488.97 (10) Å³
Z = 2
Mo K radiation
= 4.04 mm^-1
T = 293 (2) K
0.46 × 0.38 × 0.38 mm

Data collection

Stoe IPDS diffractometer
Absorption correction: numerical (HABITUS; Herrendorf, 1997) T_min = 0.213, T_max = 0.327
5412 measured reflections
368 independent reflections
367 reflections with I > 2(I)
R_int = 0.025

Refinement

R[F² > 2(F²)] = 0.016
wR(F²) = 0.034
S = 1.29
368 reflections
39 parameters
4 restraints
H atoms treated by a mixture of independent and constrained refinement
_max = 0.40 e Å^-3
_min = -0.31 e Å^-3
Absolute structure: Flack (1983), with 164 Friedel pairs
Flack parameter: -0.01 (3)

Table 1
Selected bond lengths (Å)

Cs-O3ⁱ	3.469 (5)
Cs-O4ⁱ	3.470 (4)
Cs-O4ⁱⁱ	3.742 (4)
Mg-O3	2.054 (4)
Mg-O4	2.082 (3)
P-O1	1.536 (3)
P-O2	1.539 (6)
Symmetry codes: (i) -y, x-y, z; (ii) $[y, -x+y+1, z-{\script{1\over 2}}]$ .

Table 2
Hydrogen-bond geometry (Å, °)

D-HA	D-H	HA	DA	D-HA
O3-H1O2	0.93 (4)	1.71 (4)	2.643 (5)	180 (6)
O3-H2O1ⁱⁱⁱ	0.88 (4)	1.76 (5)	2.630 (5)	168 (7)
O4-H3O1^iv	0.83 (4)	1.85 (4)	2.672 (3)	177 (8)
Symmetry codes: (iii) $[y, -x+y, z-{\script{1\over 2}}]$ ; (iv) -x+y, -x, z.

Data collection: EXPOSE in IPDS Software (Stoe & Cie, 1998); cell refinement: CELL in IPDS Software; data reduction: INTEGRATE in IPDS Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2004); software used to prepare material for publication: SHELXL97.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2080 ).

Acknowledgements

The author thanks B. Müller (University of Ulm, Germany) for collecting the intensity data.

References

Banks, E., Chianelli, R. & Korenstein, R. (1975). Inorg. Chem. 14, 1634-1639.
Dowty, E. (2004). ATOMS for Windows. Shape Software, Kingsport, Tennessee, USA.
Ferrari, A., Calvaca, L. & Nardelli, M. (1955). Gazz. Chim. Ital. 85, 1232-1238.
Flack, H. D. (1983). Acta Cryst. A39, 876-881.
Herrendorf, W. (1997). HABITUS. University of Giessen, Germany.
Massa, W., Yakubovich, O. V. & Dimitrova, O. V. (2003). Acta Cryst. C59, i83-i85.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Stoe & Cie (1998). IPDS Software. Stoe & Cie, Darmstadt, Germany.
Whitaker, A. & Jeffery, J. W. (1970a). Acta Cryst. B26, 1429-1440.
Whitaker, A. & Jeffery, J. W. (1970b). Acta Cryst. B26, 1440-1444.

inorganic compounds

Redetermination of the hexagonal struvite analogue Cs[Mg(OH2)6](PO4)