Imidazolium trans-di-aqua-dioxalato-chromate(III) dihydrate.

In the title hydrated mol-ecular salt, (C3H5N2)[Cr(C2O4)2(H2O)2]·2H2O, the complete cation is generated by a crystallographic twofold rotation axis, with one C atom lying on the rotation axis. The complete anion is generated by crystallographic inversion symmetry (Cr(III) site symmetry -1), to generate a slightly distorted CrO6 octa-hedron with trans water mol-ecules and chelating oxalate dianions. The oxalate ion is almost planar (r.m.s. deviation = 0.017 Å) and the five-membered chelate ring is a shallow envelope with the metal ion displaced by 0.126 (1) Å from the ligand atoms. The crystal structure features O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, which link the components into a three-dimensional network.

Related literature

For a related structure and background to oxalate complexes, see: Chérif et al. (2012 ▶). For the structures of n class="Chemical">salts containing the [Cr(C2O4)2(H2O)2]− anion with various cations, see: Bélombé et al. (2009 ▶); Nenwa et al. (2010 ▶); Chérif et al. (2011 ▶); Kahlenberg et al. (2011 ▶). For geometric parameters of the imidazolium cation, see: Zhu (2012 ▶); Smith & Wermuth (2010 ▶).

Experimental

Crystal data

(C3H5N2)n class="Chemical">[Cr(C2O4)2(H2O)2]·2H2O

M = 369.19

Monoclinic,

a = 10.836 (1) Å

b = 7.5409 (7) Å

c = 16.349 (3) Å

β = 93.52 (1)°

V = 1333.4 (3) Å3

Z = 4

Mo Kα radiation

μ = 0.93 mm−1

T = 298 K

0.6 × 0.4 × 0.3 mm

Data collection

Enraf–Nonius CAD-4 diffractometer

Absorption correction: ψ scan (North et al., 1968 ▶) T min = 0.647, T max = 0.757

1848 measured reflections

1452 independent reflections

1369 reflections with I > 2σ(I)

R int = 0.011

2 standard reflections every 120 min intensity decay: 2.2%

Refinement

R[F 2 > 2σ(F 2)] = 0.029

wR(F 2) = 0.086

S = 1.12

1452 reflections

124 parameters

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.55 e Å−3

Δρmin = −0.39 e Å−3

Data collection: CAD-4 EXPRESS (Duisenberg, 1992 ▶; Macíček & Yordanov, 1992 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 1999 ▶); software used to prepare material for publication: WinGX (Farrugia, 2012 ▶).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S160053681303078X/hb7157sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681303078X/hb7157Isup2.hkl

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

(C3H5N2)[Cr(C2O4)2(H2O)2]·2H2O	F(000) = 756
Mr = 369.19	Dx = 1.839 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 25 reflections
a = 10.836 (1) Å	θ = 10–15°
b = 7.5409 (7) Å	µ = 0.93 mm−1
c = 16.349 (3) Å	T = 298 K
β = 93.52 (1)°	Prism, violet
V = 1333.4 (3) Å3	0.6 × 0.4 × 0.3 mm
Z = 4

Enraf–Nonius CAD-4 diffractometer	1369 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.011
Graphite monochromator	θmax = 27.0°, θmin = 2.5°
ω/2θ scans	h = −13→13
Absorption correction: ψ scan (North et al., 1968)	k = −1→9
Tmin = 0.647, Tmax = 0.757	l = −20→1
1848 measured reflections	2 standard reflections every 120 min
1452 independent reflections	intensity decay: 2.2%

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.086	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ2(Fo2) + (0.0456P)2 + 1.7165P] where P = (Fo2 + 2Fc2)/3
1452 reflections	(Δ/σ)max < 0.001
124 parameters	Δρmax = 0.55 e Å−3
0 restraints	Δρmin = −0.39 e Å−3

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
Cr	0.7500	0.2500	0.5000	0.02258 (15)
O2	0.70111 (13)	0.12749 (18)	0.39687 (8)	0.0324 (3)
O3	0.83676 (12)	0.02646 (17)	0.52566 (8)	0.0276 (3)
O4	0.73747 (15)	−0.12361 (19)	0.33002 (9)	0.0387 (4)
O6	0.86780 (17)	0.5293 (2)	0.31972 (10)	0.0402 (4)
C1	0.83297 (15)	−0.0860 (2)	0.46642 (11)	0.0242 (4)
O1	0.59861 (14)	0.1644 (2)	0.54913 (11)	0.0424 (4)
O5	0.88681 (13)	−0.22844 (18)	0.46604 (9)	0.0334 (3)
C2	0.75010 (16)	−0.0264 (2)	0.38993 (11)	0.0264 (4)
C3	0.9690 (2)	0.1333 (3)	0.71415 (13)	0.0372 (5)
H7	0.9425	0.2337	0.6851	0.045*
N1	0.95088 (19)	−0.0291 (4)	0.69055 (13)	0.0575 (6)
C4	1.0000	−0.1396 (5)	0.7500	0.0518 (9)
H1	0.832 (3)	0.618 (4)	0.3298 (18)	0.051 (8)*
H2	0.535 (3)	0.199 (4)	0.5285 (19)	0.055 (8)*
H3	0.606 (3)	0.101 (4)	0.592 (2)	0.056 (8)*
H4	0.837 (3)	0.493 (5)	0.283 (2)	0.072 (12)*
H5	0.910 (4)	−0.078 (5)	0.636 (2)	0.085 (11)*
H6	1.0000	−0.257 (7)	0.7500	0.087 (18)*

	U11	U22	U33	U12	U13	U23
Cr	0.0263 (2)	0.0204 (2)	0.0200 (2)	0.00213 (14)	−0.00693 (15)	0.00055 (13)
O2	0.0411 (7)	0.0286 (7)	0.0257 (6)	0.0078 (6)	−0.0137 (5)	−0.0039 (5)
O3	0.0326 (7)	0.0246 (6)	0.0242 (6)	0.0035 (5)	−0.0095 (5)	0.0005 (5)
O4	0.0485 (8)	0.0352 (8)	0.0306 (7)	0.0058 (6)	−0.0109 (6)	−0.0097 (6)
O6	0.0554 (10)	0.0333 (8)	0.0311 (8)	0.0038 (7)	−0.0030 (7)	−0.0006 (6)
C1	0.0222 (8)	0.0235 (8)	0.0262 (8)	−0.0013 (6)	−0.0029 (6)	0.0014 (7)
O1	0.0296 (8)	0.0528 (10)	0.0441 (9)	0.0015 (7)	−0.0030 (7)	0.0219 (8)
O5	0.0326 (7)	0.0260 (7)	0.0408 (8)	0.0062 (5)	−0.0053 (6)	−0.0010 (6)
C2	0.0277 (8)	0.0267 (9)	0.0242 (8)	−0.0009 (7)	−0.0045 (7)	−0.0010 (7)
C3	0.0401 (11)	0.0382 (11)	0.0335 (10)	0.0124 (9)	0.0040 (8)	0.0118 (9)
N1	0.0402 (10)	0.0946 (19)	0.0362 (10)	0.0027 (11)	−0.0099 (8)	−0.0193 (11)
C4	0.0457 (18)	0.0294 (16)	0.080 (3)	0.000	0.0024 (17)	0.000

Cr—O3i	1.963 (1)	C1—O5	1.223 (2)
Cr—O3	1.963 (1)	C1—C2	1.560 (2)
Cr—O2	1.967 (1)	O1—H2	0.79 (4)
Cr—O2i	1.967 (1)	O1—H3	0.85 (3)
Cr—O1i	1.979 (2)	C3—N1	1.295 (3)
Cr—O1	1.979 (2)	C3—C3ii	1.315 (4)
O2—C2	1.284 (2)	C3—H7	0.9300
O3—C1	1.286 (2)	N1—C4	1.363 (3)
O4—C2	1.224 (2)	N1—H5	1.04 (4)
O6—H1	0.80 (3)	C4—N1ii	1.363 (3)
O6—H4	0.73 (4)	C4—H6	0.89 (5)
O3i—Cr—O3	180.0	O5—C1—O3	126.15 (16)
O3i—Cr—O2	96.89 (5)	O5—C1—C2	120.02 (16)
O3—Cr—O2	83.11 (5)	O3—C1—C2	113.83 (14)
O3i—Cr—O2i	83.11 (5)	Cr—O1—H2	116 (2)
O3—Cr—O2i	96.89 (5)	Cr—O1—H3	119 (2)
O2—Cr—O2i	180.0	H2—O1—H3	125 (3)
O3i—Cr—O1i	91.78 (7)	O4—C2—O2	125.83 (17)
O3—Cr—O1i	88.22 (7)	O4—C2—C1	119.95 (16)
O2—Cr—O1i	89.52 (7)	O2—C2—C1	114.21 (15)
O2i—Cr—O1i	90.48 (7)	N1—C3—C3ii	108.99 (13)
O3i—Cr—O1	88.22 (7)	N1—C3—H7	125.5
O3—Cr—O1	91.78 (7)	C3ii—C3—H7	125.5
O2—Cr—O1	90.48 (7)	C3—N1—C4	108.7 (2)
O2i—Cr—O1	89.52 (7)	C3—N1—H5	130 (2)
O1i—Cr—O1	180.0	C4—N1—H5	122 (2)
C2—O2—Cr	114.16 (11)	N1ii—C4—N1	104.7 (3)
C1—O3—Cr	114.36 (11)	N1ii—C4—H6	127.67 (16)
H1—O6—H4	107 (3)	N1—C4—H6	127.67 (15)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H1···O4iii	0.80 (3)	2.20 (3)	2.984 (2)	168 (3)
O6—H4···O4iv	0.72 (3)	2.16 (3)	2.878 (2)	174 (4)
O1—H2···O5v	0.79 (3)	1.93 (3)	2.717 (2)	173 (3)
O1—H3···O6i	0.85 (3)	1.75 (3)	2.601 (2)	176 (3)
N1—H5···O3	1.04 (4)	2.07 (3)	2.926 (2)	137 (2)
C3—H7···O2i	0.93	2.25	3.088 (3)	150

Table 1

Selected bond lengths (Å)

Cr—O3	1.963 (1)
Cr—O2	1.967 (1)
Cr—O1	1.979 (2)

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O6—H1⋯O4i	0.80 (3)	2.20 (3)	2.984 (2)	168 (3)
O6—H4⋯O4ii	0.72 (3)	2.16 (3)	2.878 (2)	174 (4)
O1—H2⋯O5iii	0.79 (3)	1.93 (3)	2.717 (2)	173 (3)
O1—H3⋯O6iv	0.85 (3)	1.75 (3)	2.601 (2)	176 (3)
N1—H5⋯O3	1.04 (4)	2.07 (3)	2.926 (2)	137 (2)
C3—H7⋯O2iv	0.93	2.25	3.088 (3)	150

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