Redetermination of the hexa-gonal struvite analogue Cs[Mg(OH(2))(6)](PO(4)).

The structure of the hexa-gonal modification of caesium hexa-aqua-magnesium 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 PO(4) tetra-hedra (3m. symmetry) are on the Ni positions and the complex [Mg(OH(2))(6)] octa-hedra (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 cubocta-hedral 12-coordination by the O atoms of the water mol-ecules.

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 = 360.29

Hexagonal,

a = 6.8827 (8) Å

c = 11.9188 (16) Å

V = 488.97 (10) Å3

Z = 2

Mo Kα radiation

μ = 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 > 2σ(I)

R int = 0.025

Refinement

R[F 2 > 2σ(F 2)] = 0.016

wR(F 2) = 0.034

S = 1.29

368 reflections

39 parameters

4 restraints

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.40 e Å−3

Δρmin = −0.31 e Å−3

Absolute structure: Flack (1983 ▶), with 164 Friedel pairs

Flack parameter: −0.01 (3)

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.

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808023283/br2080sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808023283/br2080Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Cs[Mg(H2O1)6](PO4)	Z = 2
Mr = 360.29	F000 = 348
Hexagonal, P63mc	Dx = 2.447 Mg m−3
Hall symbol: P 6c -2c	Mo Kα radiation λ = 0.71073 Å
a = 6.8827 (8) Å	Cell parameters from 1544 reflections
b = 6.8827 (8) Å	θ = 3.4–25.9º
c = 11.9188 (16) Å	µ = 4.04 mm−1
α = 90º	T = 293 (2) K
β = 90º	Block, colourless
γ = 120º	0.46 × 0.38 × 0.38 mm
V = 488.97 (10) Å3

Stoe IPDS diffractometer	368 independent reflections
Radiation source: fine-focus sealed tube	367 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.025
T = 293(2) K	θmax = 25.7º
ω scans	θmin = 3.4º
Absorption correction: numerical(HABITUS; Herrendorf, 1997)	h = −8→8
Tmin = 0.213, Tmax = 0.327	k = −8→8
5412 measured reflections	l = −12→13

Refinement on F2	Hydrogen site location: difference Fourier map
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.016	w = 1/[σ2(Fo2) + (0.0029P)2 + 0.8141P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.034	(Δ/σ)max < 0.001
S = 1.29	Δρmax = 0.40 e Å−3
368 reflections	Δρmin = −0.31 e Å−3
39 parameters	Extinction correction: none
4 restraints	Absolute structure: Flack (1983), with 164 Friedel pairs
Primary atom site location: structure-invariant direct methods	Flack parameter: −0.01 (3)
Secondary atom site location: difference Fourier map

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.

	x	y	z	Uiso*/Ueq
Cs	0.3333	0.6667	0.02181 (4)	0.03126 (15)
Mg	0.6667	0.3333	0.1436 (2)	0.0159 (5)
P	0.0000	0.0000	0.29985 (14)	0.0137 (5)
O1	0.1220 (2)	0.2440 (4)	0.3413 (3)	0.0173 (6)
O2	0.0000	0.0000	0.1707 (5)	0.0189 (13)
O3	0.3747 (6)	0.1873 (3)	0.0521 (3)	0.0265 (9)
O4	0.5229 (3)	0.0458 (5)	0.2427 (3)	0.0282 (8)
H1	0.243 (8)	0.122 (4)	0.094 (5)	0.048 (9)*
H2	0.350 (12)	0.175 (6)	−0.021 (4)	0.048 (9)*
H3	0.397 (8)	−0.010 (14)	0.272 (5)	0.048 (9)*

	U11	U22	U33	U12	U13	U23
Cs	0.02671 (16)	0.02671 (16)	0.0404 (3)	0.01335 (8)	0.000	0.000
Mg	0.0158 (8)	0.0158 (8)	0.0160 (16)	0.0079 (4)	0.000	0.000
P	0.0139 (5)	0.0139 (5)	0.0134 (13)	0.0069 (2)	0.000	0.000
O1	0.0172 (9)	0.0139 (13)	0.0195 (17)	0.0070 (7)	−0.0023 (6)	−0.0046 (12)
O2	0.0177 (19)	0.0177 (19)	0.021 (4)	0.0089 (10)	0.000	0.000
O3	0.0142 (14)	0.0406 (14)	0.016 (3)	0.0071 (7)	−0.0023 (11)	−0.0012 (5)
O4	0.0191 (11)	0.0252 (19)	0.042 (2)	0.0126 (10)	0.0096 (7)	0.0191 (15)

Cs—O3i	3.469 (5)	Mg—O3	2.054 (4)
Cs—O3ii	3.469 (5)	Mg—O3v	2.054 (4)
Cs—O3iii	3.469 (5)	Mg—O4ix	2.082 (3)
Cs—O3iv	3.469 (5)	Mg—O4	2.082 (3)
Cs—O3v	3.469 (5)	Mg—O4v	2.082 (3)
Cs—O3	3.469 (5)	Mg—Csx	4.2306 (10)
Cs—O4i	3.470 (4)	Mg—Csxi	4.2306 (10)
Cs—O4iv	3.470 (4)	Mg—Csxii	4.508 (3)
Cs—O4v	3.470 (4)	P—O1	1.536 (3)
Cs—O4vi	3.742 (4)	P—O1iv	1.536 (3)
Cs—O4vii	3.742 (4)	P—O1xiii	1.536 (3)
Cs—O4viii	3.742 (4)	P—O2	1.539 (6)
Mg—O3ix	2.054 (4)
O3i—Cs—O3ii	51.51 (11)	O3v—Cs—O4vii	97.18 (5)
O3i—Cs—O3iii	67.77 (11)	O3—Cs—O4vii	118.02 (7)
O3ii—Cs—O3iii	118.93 (2)	O4i—Cs—O4vii	112.101 (19)
O3i—Cs—O3iv	118.93 (2)	O4iv—Cs—O4vii	145.46 (3)
O3ii—Cs—O3iv	165.52 (11)	O4v—Cs—O4vii	145.46 (3)
O3iii—Cs—O3iv	51.51 (11)	O4vi—Cs—O4vii	46.74 (8)
O3i—Cs—O3v	118.93 (2)	O3i—Cs—O4viii	118.02 (7)
O3ii—Cs—O3v	67.77 (11)	O3ii—Cs—O4viii	97.18 (5)
O3iii—Cs—O3v	165.52 (11)	O3iii—Cs—O4viii	118.02 (7)
O3iv—Cs—O3v	118.93 (2)	O3iv—Cs—O4viii	97.18 (5)
O3i—Cs—O3	165.52 (11)	O3v—Cs—O4viii	71.50 (7)
O3ii—Cs—O3	118.93 (2)	O3—Cs—O4viii	71.50 (7)
O3iii—Cs—O3	118.93 (2)	O4i—Cs—O4viii	145.46 (3)
O3iv—Cs—O3	67.77 (11)	O4iv—Cs—O4viii	145.46 (3)
O3v—Cs—O3	51.51 (11)	O4v—Cs—O4viii	112.101 (19)
O3i—Cs—O4i	48.58 (7)	O4vi—Cs—O4viii	46.74 (8)
O3ii—Cs—O4i	48.58 (7)	O4vii—Cs—O4viii	46.74 (8)
O3iii—Cs—O4i	88.12 (6)	O3ix—Mg—O3	94.42 (16)
O3iv—Cs—O4i	117.22 (7)	O3ix—Mg—O3v	94.42 (16)
O3v—Cs—O4i	88.12 (6)	O3—Mg—O3v	94.42 (16)
O3—Cs—O4i	117.22 (7)	O3ix—Mg—O4ix	87.27 (10)
O3i—Cs—O4iv	88.12 (6)	O3—Mg—O4ix	177.5 (2)
O3ii—Cs—O4iv	117.22 (7)	O3v—Mg—O4ix	87.27 (10)
O3iii—Cs—O4iv	48.58 (7)	O3ix—Mg—O4	87.27 (10)
O3iv—Cs—O4iv	48.58 (7)	O3—Mg—O4	87.27 (10)
O3v—Cs—O4iv	117.22 (7)	O3v—Mg—O4	177.5 (2)
O3—Cs—O4iv	88.12 (6)	O4ix—Mg—O4	90.98 (19)
O4i—Cs—O4iv	68.67 (8)	O3ix—Mg—O4v	177.5 (2)
O3i—Cs—O4v	117.22 (7)	O3—Mg—O4v	87.27 (10)
O3ii—Cs—O4v	88.12 (6)	O3v—Mg—O4v	87.27 (10)
O3iii—Cs—O4v	117.22 (7)	O4ix—Mg—O4v	90.98 (19)
O3iv—Cs—O4v	88.12 (6)	O4—Mg—O4v	90.98 (19)
O3v—Cs—O4v	48.58 (7)	O1—P—O1iv	110.17 (14)
O3—Cs—O4v	48.58 (7)	O1—P—O1xiii	110.17 (14)
O4i—Cs—O4v	68.67 (8)	O1iv—P—O1xiii	110.17 (14)
O4iv—Cs—O4v	68.67 (8)	O1—P—O2	108.76 (14)
O3i—Cs—O4vi	97.18 (5)	O1iv—P—O2	108.76 (14)
O3ii—Cs—O4vi	118.02 (7)	O1xiii—P—O2	108.76 (14)
O3iii—Cs—O4vi	71.50 (7)	Mg—O3—Csx	96.63 (6)
O3iv—Cs—O4vi	71.50 (7)	Mg—O3—Cs	96.63 (6)
O3v—Cs—O4vi	118.02 (7)	Csx—O3—Cs	165.52 (11)
O3—Cs—O4vi	97.18 (5)	Mg—O3—H1	116 (4)
O4i—Cs—O4vi	145.46 (3)	Mg—O3—H2	132 (5)
O4iv—Cs—O4vi	112.101 (19)	H1—O3—H2	113 (6)
O4v—Cs—O4vi	145.46 (3)	Mg—O4—Csx	96.07 (16)
O3i—Cs—O4vii	71.50 (7)	Mg—O4—Csxii	97.31 (14)
O3ii—Cs—O4vii	71.50 (7)	Csx—O4—Csxii	166.63 (10)
O3iii—Cs—O4vii	97.18 (5)	Mg—O4—H3	125 (4)
O3iv—Cs—O4vii	118.02 (7)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1···O2	0.93 (4)	1.71 (4)	2.643 (5)	180 (6)
O3—H2···O1xiv	0.88 (4)	1.76 (5)	2.630 (5)	168 (7)
O4—H3···O1xiii	0.83 (4)	1.85 (4)	2.672 (3)	177 (8)

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) ; (ii) .

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H1⋯O2	0.93 (4)	1.71 (4)	2.643 (5)	180 (6)
O3—H2⋯O1iii	0.88 (4)	1.76 (5)	2.630 (5)	168 (7)
O4—H3⋯O1iv	0.83 (4)	1.85 (4)	2.672 (3)	177 (8)

Symmetry codes: (iii) ; (iv) .