A new polymorph of magnesium oxalate dihydrate.

In the asymmetric unit of the title compound, catena-poly[[diaqua-magnesium(II)]-μ-oxalato], [Mg(C(2)O(4))(H(2)O)(2)](n), there is one Mg atom in an octa-hedral coordination with site symmetry 222, a unique C atom of the oxalate anion lying on a twofold axis, an O atom of the anion in a general position and a water O atom at a site with imposed twofold rotation symmetry. The Mg(2+) ions are ligated by water mol-ecules and bridged by the anions to form chains that are held together by O-H⋯O hydrogen bonds. The structure of the title compound has already been reported in a different space group [Lagier, Pezerat & Dubernat (1969 ▶). Rev. Chim. Miner.6, 1081-1093; Levy, Perrotey & Visser (1971 ▶). Bull. Soc. Chim. Fr. pp. 757-761].

Related literature

For related literature, see: Basso et al. (1997 ▶); Caric (1959 ▶); Deyrieux et al. (1973 ▶); Echigo et al. (2005 ▶); Huang & Mak (1990 ▶); Lagier et al. (1969 ▶); Le Page (1987 ▶); Lethbridge et al. (2003 ▶); Levy et al. (1971 ▶); Neder et al. (1997 ▶); Schefer & Grube (1995 ▶); Tazzoli & Domeneghetti (1980 ▶); Vanhoyland, Bouree et al. (2001 ▶); Vanhoyland, Van Bael et al. (2001 ▶).

Experimental

Crystal data

[Mg(C2O4)(H2O)2]

M = 148.36

Orthorhombic,

a = 5.3940 (11) Å

b = 12.691 (3) Å

c = 15.399 (3) Å

V = 1054.1 (4) Å3

Z = 8

Mo Kα radiation

μ = 0.29 mm−1

T = 290 K

0.30 × 0.20 × 0.15 mm

Data collection

Rigaku AFC-7R diffractometer

Absorption correction: ψ scan (Kopfmann & Huber, 1968 ▶) T min = 0.915, T max = 0.962

1110 measured reflections

483 independent reflections

321 reflections with I > 2σ(I)

R int = 0.054

3 standard reflections every 150 reflections intensity decay: 1.1%

Refinement

R[F 2 > 2σ(F 2)] = 0.034

wR(F 2) = 0.110

S = 0.97

483 reflections

27 parameters

All H-atom parameters refined

Δρmax = 0.89 e Å−3

Δρmin = −0.48 e Å−3

Data collection: Rigaku/AFC Diffractometer Control Software (Rigaku, 1994 ▶); cell refinement: Rigaku/AFC Diffractometer Control Software; data reduction: Rigaku/AFC Diffractometer Control Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ATOMS (Dowty, 1999 ▶); software used to prepare material for publication: SHELXL97.

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808015870/pv2083sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808015870/pv2083Isup2.hkl

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

[Mg(C2O4)(H2O)2]	F000 = 608
Mr = 148.36	Dx = 1.870 Mg m−3
Orthorhombic, Fddd	Mo Kα radiation λ = 0.71073 Å
Hall symbol: -F 2uv 2vw	Cell parameters from 25 reflections
a = 5.3940 (11) Å	θ = 13.0–19.6º
b = 12.691 (3) Å	µ = 0.29 mm−1
c = 15.399 (3) Å	T = 290 K
V = 1054.1 (4) Å3	Block, colourless
Z = 8	0.30 × 0.20 × 0.15 mm

Rigaku AFC-7R diffractometer	Rint = 0.054
Radiation source: fine-focus sealed tube	θmax = 32.5º
Monochromator: graphite	θmin = 4.2º
T = 290 K	h = 0→8
2θ/ω scans	k = 0→19
Absorption correction: ψ scan(Kopfmann & Huber, 1968)	l = 0→23
Tmin = 0.915, Tmax = 0.962	3 standard reflections
1110 measured reflections	every 150 reflections
483 independent reflections	intensity decay: 1.1%
321 reflections with I > 2σ(I)

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.034	All H-atom parameters refined
wR(F2) = 0.110	w = 1/[σ2(Fo2) + (0.0683P)2] where P = (Fo2 + 2Fc2)/3
S = 0.97	(Δ/σ)max < 0.001
483 reflections	Δρmax = 0.89 e Å−3
27 parameters	Δρmin = −0.48 e Å−3
Primary atom site location: structure-invariant direct methods	Extinction correction: none

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.

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 > 2sigma(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	0.3750	0.3750	0.3750	0.0163 (2)
C1	0.8750	0.3750	0.32406 (10)	0.0153 (3)
O1	0.66783 (15)	0.37630 (11)	0.28779 (5)	0.0202 (3)
O2	0.3750	0.53689 (11)	0.3750	0.0343 (4)
H2	0.399 (6)	0.578 (2)	0.3335 (16)	0.050 (7)*

	U11	U22	U33	U12	U13	U23
Mg1	0.0117 (4)	0.0237 (4)	0.0136 (4)	0.000	0.000	0.000
C1	0.0149 (6)	0.0199 (6)	0.0110 (6)	−0.0001 (8)	0.000	0.000
O1	0.0145 (4)	0.0342 (5)	0.0120 (4)	0.0012 (4)	−0.0014 (3)	−0.0018 (4)
O2	0.0631 (11)	0.0228 (7)	0.0169 (6)	0.000	0.0086 (10)	0.000

Mg1—O2i	2.0546 (15)	Mg1—O1	2.0734 (9)
Mg1—O2	2.0546 (15)	C1—O1	1.2494 (11)
Mg1—O1i	2.0734 (9)	C1—O1iv	1.2494 (11)
Mg1—O1ii	2.0734 (9)	C1—C1v	1.569 (3)
Mg1—O1iii	2.0734 (9)	O2—H2	0.84 (3)
O2i—Mg1—O2	180.0	O2i—Mg1—O1	90.45 (4)
O2i—Mg1—O1i	89.55 (4)	O2—Mg1—O1	89.55 (4)
O2—Mg1—O1i	90.45 (4)	O1i—Mg1—O1	99.26 (5)
O2i—Mg1—O1ii	89.55 (4)	O1ii—Mg1—O1	80.75 (5)
O2—Mg1—O1ii	90.45 (4)	O1iii—Mg1—O1	179.09 (8)
O1i—Mg1—O1ii	179.09 (7)	O1—C1—O1iv	126.89 (14)
O2i—Mg1—O1iii	90.45 (4)	O1—C1—C1v	116.56 (7)
O2—Mg1—O1iii	89.55 (4)	O1iv—C1—C1v	116.56 (7)
O1i—Mg1—O1iii	80.75 (5)	C1—O1—Mg1	113.06 (8)
O1ii—Mg1—O1iii	99.26 (5)	Mg1—O2—H2	128.7 (19)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1vi	0.84 (3)	1.97 (2)	2.761 (1)	158 (2)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O1i	0.84 (3)	1.97 (2)	2.761 (1)	158 (2)

Symmetry code: (i) .