Redetermination of kovdorskite, Mg(2)PO(4)(OH)·3H(2)O.

The crystal structure of kovdorskite, ideally Mg(2)PO(4)(OH)·3H(2)O (dimagnesium phosphate hydroxide trihydrate), was reported previously with isotropic displacement paramaters only and without H-atom positions [Ovchinnikov et al. (1980 ▶). Dokl. Akad. Nauk SSSR.255, 351-354]. In this study, the kovdorskite structure is redetermined based on single-crystal X-ray diffraction data from a sample from the type locality, the Kovdor massif, Kola Peninsula, Russia, with anisotropic displacement parameters for all non-H atoms, with all H-atom located and with higher precision. Moreover, inconsistencies of the previously published structural data with respect to reported and calculated X-ray powder patterns are also discussed. The structure of kovdorskite contains a set of four edge-sharing MgO(6) octa-hedra inter-connected by PO(4) tetra-hedra and O-H⋯O hydrogen bonds, forming columns and channels parallel to [001]. The hydrogen-bonding system in kovdorskite is formed through the water mol-ecules, with the OH(-) ions contributing little, if any, to the system, as indicated by the long H⋯A distances (>2.50 Å) to the nearest O atoms. The hydrogen-bond lengths determined from the structure refinement agree well with Raman spectroscopic data.

Related literature

For background to kovdorskite, see: Kapustin et al. (1980 ▶); Ovchinnikov et al. (1980 ▶); Ponomareva (1990 ▶); Lake & Craven (2001 ▶). For biomaterials studies of hydrated magnesium phosphates, see: Sutor et al. (1974 ▶); Tamimi et al. (2011 ▶); Klammert et al. (2011 ▶). For applications of hydrated magnesium phosphates in the refractories industry, see: Kingery (1950 ▶, 1952 ▶); Lyon et al. (1966 ▶); Sarkar (1990 ▶). For applications of hydrated magnesium phosphate in fertilizers, see: Pelly & Bar-On (1979 ▶). For Raman spectra of related systems, see: Frost et al. (2002 ▶, 2011 ▶). For correlations between O—H streching frequencies and O—H⋯O donor–acceptor distances, see: Libowitzky (1999 ▶).

Experimental

Crystal data

Mg2PO4(OH)·3H2O

M = 214.65

Monoclinic,

a = 10.4785 (1) Å

b = 12.9336 (2) Å

c = 4.7308 (1) Å

β = 105.054 (1)°

V = 619.14 (2) Å3

Z = 4

Mo Kα radiation

μ = 0.65 mm−1

T = 293 K

0.10 × 0.09 × 0.09 mm

Data collection

Bruker APEXII CCD area-detector diffractometer

Absorption correction: multi-scan (SADABS; Sheldrick, 2005 ▶) T min = 0.938, T max = 0.944

8463 measured reflections

2231 independent reflections

2008 reflections with I > 2σ(I)

R int = 0.026

Refinement

R[F 2 > 2σ(F 2)] = 0.022

wR(F 2) = 0.056

S = 1.07

2231 reflections

129 parameters

All H-atom parameters refined

Δρmax = 0.50 e Å−3

Δρmin = −0.34 e Å−3

Data collection: APEX2 (Bruker, 2004 ▶); cell refinement: SAINT (Bruker, 2004 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812000256/wm2577sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812000256/wm2577Isup2.hkl

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

Mg2PO4(OH)·3H2O	F(000) = 440
Mr = 214.65	Dx = 2.303 Mg m−3
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yab	Cell parameters from 4644 reflections
a = 10.4785 (1) Å	θ = 2.7–32.5°
b = 12.9336 (2) Å	µ = 0.65 mm−1
c = 4.7308 (1) Å	T = 293 K
β = 105.054 (1)°	Cuboid, colorless
V = 619.14 (2) Å3	0.10 × 0.09 × 0.09 mm
Z = 4

Bruker APEXII CCD area-detector diffractometer	2231 independent reflections
Radiation source: fine-focus sealed tube	2008 reflections with I > 2σ(I)
graphite	Rint = 0.026
φ and ω scan	θmax = 32.5°, θmin = 3.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 2005)	h = −15→13
Tmin = 0.938, Tmax = 0.944	k = −15→19
8463 measured reflections	l = −7→7

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.022	All H-atom parameters refined
wR(F2) = 0.056	w = 1/[σ2(Fo2) + (0.0278P)2 + 0.150P] where P = (Fo2 + 2Fc2)/3
S = 1.07	(Δ/σ)max = 0.001
2231 reflections	Δρmax = 0.50 e Å−3
129 parameters	Δρmin = −0.34 e Å−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.014 (2)

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
Mg1	0.15418 (3)	0.48809 (3)	0.04828 (7)	0.00906 (8)
Mg2	0.49666 (3)	0.21171 (3)	0.93433 (7)	0.00854 (8)
P1	0.21969 (2)	0.321419 (19)	0.59573 (5)	0.00682 (7)
O1	0.34918 (7)	0.26654 (6)	0.58522 (15)	0.01002 (14)
O2	0.13841 (7)	0.24609 (5)	0.73290 (15)	0.01022 (14)
O3	0.14008 (7)	0.35212 (6)	0.28575 (14)	0.01018 (14)
O4	0.25621 (7)	0.41919 (6)	0.78609 (15)	0.01050 (14)
OH5	0.01976 (7)	0.56414 (5)	0.22485 (15)	0.00943 (13)
OW6	0.16539 (8)	0.64623 (6)	−0.12401 (16)	0.01279 (14)
OW7	0.32209 (8)	0.53186 (7)	0.35888 (18)	0.01745 (16)
OW8	0.48594 (8)	0.34594 (7)	1.16317 (18)	0.01686 (16)
H1	0.0319 (18)	0.5627 (14)	0.419 (4)	0.034 (5)*
H2	0.160 (2)	0.6770 (16)	−0.298 (5)	0.051 (6)*
H3	0.2345 (18)	0.6736 (13)	−0.005 (4)	0.030 (4)*
H4	0.3228 (19)	0.5108 (14)	0.536 (4)	0.035 (5)*
H5	0.353 (3)	0.591 (2)	0.371 (5)	0.070 (8)*
H6	0.4269 (19)	0.3840 (15)	1.068 (4)	0.038 (5)*
H7	0.468 (3)	0.3322 (18)	1.312 (6)	0.063 (7)*

	U11	U22	U33	U12	U13	U23
Mg1	0.00832 (15)	0.00862 (16)	0.00998 (15)	0.00010 (12)	0.00191 (11)	−0.00105 (11)
Mg2	0.00828 (15)	0.00792 (16)	0.00926 (15)	0.00010 (12)	0.00198 (11)	−0.00018 (11)
P1	0.00668 (11)	0.00727 (12)	0.00646 (11)	0.00097 (8)	0.00160 (7)	0.00004 (7)
O1	0.0086 (3)	0.0122 (3)	0.0093 (3)	0.0028 (3)	0.0025 (2)	−0.0001 (2)
O2	0.0105 (3)	0.0093 (3)	0.0120 (3)	0.0004 (3)	0.0051 (2)	0.0011 (2)
O3	0.0106 (3)	0.0101 (3)	0.0082 (3)	0.0000 (3)	−0.0006 (2)	0.0015 (2)
O4	0.0115 (3)	0.0097 (3)	0.0105 (3)	−0.0007 (3)	0.0033 (2)	−0.0028 (2)
OH5	0.0103 (3)	0.0095 (3)	0.0082 (3)	0.0003 (2)	0.0018 (2)	0.0000 (2)
OW6	0.0143 (3)	0.0130 (3)	0.0106 (3)	−0.0037 (3)	0.0024 (3)	0.0006 (3)
OW7	0.0181 (4)	0.0163 (4)	0.0149 (4)	−0.0043 (3)	−0.0011 (3)	−0.0001 (3)
OW8	0.0172 (4)	0.0150 (4)	0.0162 (4)	0.0034 (3)	0.0004 (3)	−0.0031 (3)

Mg1—O4i	2.0407 (8)	Mg2—OW8	2.0644 (9)
Mg1—OH5ii	2.0553 (8)	Mg2—O1	2.0720 (7)
Mg1—OW7	2.0573 (9)	Mg2—O3v	2.0991 (8)
Mg1—OH5	2.0641 (8)	Mg2—OW6iv	2.2798 (8)
Mg1—O3	2.1124 (8)	P1—O3	1.5390 (7)
Mg1—OW6	2.2162 (8)	P1—O4	1.5419 (7)
Mg2—O2iii	2.0365 (8)	P1—O1	1.5434 (7)
Mg2—OH5iv	2.0427 (8)	P1—O2	1.5436 (7)
O4i—Mg1—OH5ii	89.62 (3)	O2iii—Mg2—O1	91.09 (3)
O4i—Mg1—OW7	93.92 (3)	OH5iv—Mg2—O1	92.98 (3)
OH5ii—Mg1—OW7	173.58 (4)	OW8—Mg2—O1	89.96 (3)
O4i—Mg1—OH5	167.00 (3)	O2iii—Mg2—O3v	90.97 (3)
OH5ii—Mg1—OH5	79.87 (3)	OH5iv—Mg2—O3v	84.20 (3)
OW7—Mg1—OH5	97.28 (3)	OW8—Mg2—O3v	92.33 (3)
O4i—Mg1—O3	94.58 (3)	O1—Mg2—O3v	176.63 (3)
OH5ii—Mg1—O3	83.55 (3)	O2iii—Mg2—OW6iv	172.77 (3)
OW7—Mg1—O3	90.82 (3)	OH5iv—Mg2—OW6iv	78.34 (3)
OH5—Mg1—O3	91.84 (3)	OW8—Mg2—OW6iv	87.62 (3)
O4i—Mg1—OW6	95.35 (3)	O1—Mg2—OW6iv	87.90 (3)
OH5ii—Mg1—OW6	101.25 (3)	O3v—Mg2—OW6iv	89.74 (3)
OW7—Mg1—OW6	83.77 (3)	O3—P1—O4	109.62 (4)
OH5—Mg1—OW6	79.40 (3)	O3—P1—O1	110.58 (4)
O3—Mg1—OW6	168.99 (3)	O4—P1—O1	108.00 (4)
O2iii—Mg2—OH5iv	94.57 (3)	O3—P1—O2	109.98 (4)
O2iii—Mg2—OW8	99.54 (3)	O4—P1—O2	110.63 (4)
OH5iv—Mg2—OW8	165.53 (4)	O1—P1—O2	107.99 (4)

D—H···A	D—H	H···A	D···A	D—H···A
OH5—H1···OW6vi	0.892 (17)	2.497 (18)	3.2408 (10)	141.3 (15)
OH5—H1···OH5vii	0.892 (17)	2.511 (18)	3.2033 (14)	134.9 (15)
OW6—H2···O1viii	0.90 (2)	1.77 (2)	2.6518 (10)	165.3 (19)
OW6—H3···O2ix	0.869 (18)	1.849 (19)	2.7097 (10)	170.4 (17)
OW7—H4···O4	0.88 (2)	1.93 (2)	2.7221 (11)	149.4 (17)
OW7—H5···O2ix	0.83 (3)	2.07 (3)	2.8513 (11)	157 (2)
OW8—H6···O4	0.83 (2)	1.99 (2)	2.7647 (11)	156.7 (18)
OW8—H7···O1vi	0.79 (3)	2.19 (3)	2.9294 (11)	156 (2)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
OH5—H1⋯OW6i	0.892 (17)	2.497 (18)	3.2408 (10)	141.3 (15)
OH5—H1⋯OH5ii	0.892 (17)	2.511 (18)	3.2033 (14)	134.9 (15)
OW6—H2⋯O1iii	0.90 (2)	1.77 (2)	2.6518 (10)	165.3 (19)
OW6—H3⋯O2iv	0.869 (18)	1.849 (19)	2.7097 (10)	170.4 (17)
OW7—H4⋯O4	0.88 (2)	1.93 (2)	2.7221 (11)	149.4 (17)
OW7—H5⋯O2iv	0.83 (3)	2.07 (3)	2.8513 (11)	157 (2)
OW8—H6⋯O4	0.83 (2)	1.99 (2)	2.7647 (11)	156.7 (18)
OW8—H7⋯O1i	0.79 (3)	2.19 (3)	2.9294 (11)	156 (2)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .