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Acta Cryst. (2012). E68, m1325-m1326    [ doi:10.1107/S1600536812040950 ]

2-Aminopyridinium trans-diaquabis(oxalato-[kappa]2O,O)chromate(III)

J. Nenwa, G. Bebga, S. Martin, M. M. Bélombé, M. Mbarki and B. P. T. Fokwa

Abstract top

In the title hybrid salt, (C5H7N2)[Cr(H2O)2(C2O4)2], the CrIII ion is coordinated in a slightly distorted octahedral environment by four O atoms from two oxalate ligands in the equatorial plane and by two water O atoms in the axial sites. The 2-aminopyridinium cation is disordered over two sets of sites in a 0.800 (7):0.200 (7) ratio. In the crystal, N-H...O and O-H...O hydrogen bonds connect the components into a three-dimensional network. The crystal studied was an inversion twin with components in a ratio 0.75 (2):0.25 (2).

Comment top

The coordination chemistry of oxalates (C2O42-) continues to receive considerable attention, largely due to the ability of this ion to act as a remarkably flexible ligand system in complexations with a wide range of metal ions (Martin et al., 2007). In the course of recent years, a few organic–inorganic hybrid salts of the form A[Cr(H2O)2(C2O4)2].xH2O (A+ = aromatic iminium cation, 0 ≤ x ≤ 1) have been reported (Bélombé et al., 2009; Nenwa et al., 2010; Chérif et al., 2011; Chérif, Abdelhak et al., 2012; Chérif, Zid et al., 2012). These salts form crystal structures for which a set of interesting solid state properties, magnetic interactions, optical and/or optoelectronic effects, or combinations thereof may be expected. With the pyridinium core cation for instance, the resulting salts diversely crystallize in non-centrosymmetric space groups Fdd2 and Pna21 (Chérif, Abdelhak et al., 2012, 2011), or in the centrosymmetric space groups P21/c (Chérif, Zid et al., 2012) and C2/c (Nenwa et al., 2010), depending on the nature of the subtituent and/or the position of substitution. In the present contribution, we report the structure of a homologous salt in the non-centrosymmetric I2/a space group.

The asymmetric unit of the title compound is shown in Fig. 1. The main geometrical features of the [C5H7N2]+ cation are in agreement with those found in salts with similar cationic entities (Bélombé et al., 2009; Nenwa et al., 2010; Chérif et al., 2011; Chérif, Abdelhak et al., 2012; Chérif, Zid et al., 2012). The CrIII ion adopts a slightly distorted octahedral coordination environment involving four oxalate O atoms (O13, O14, O21, O23) in equatorial sites and two water O atoms (OW1, OW2) in axial sites. The equatorial Cr—O distances are shorter than the axial Cr—O distances. The bond distances in the complex anion (Table 1) are comparable with those reported for the 4-dimethylaminopyridinium compound (Nenwa et al., 2010).

In the crystal structure, intermolecular N—H···O (carbonyl) and O—H···O hydrogen bonds (Table 2, Fig. 2) connect the components into a three-dimensional network.

Related literature top

For general background to the coordination chemistry of oxalates, see: Martin et al. (2007). For the structural characterization of organic–inorganic salts containing the [Cr(H2O)2(C2O4)2]- anion, see: Bélombé et al. (2009); Nenwa et al. (2010); Chérif et al. (2011); Chérif, Abdelhak et al. (2012); Chérif, Zid et al. (2012).

Experimental top

A mixture of 2-aminopyridine (1 mmol, 100 mg) and oxalic acid (2 mmol, 260 mg) was dissolved in 30 ml of ethanol. An aqueous solution (20 ml) of CrCl3.6H2O (1 mmol, 266.5 mg) was added in successive small portions and stirred for 4 h continuously. The final blue–violet solution obtained was left at room temperature and crystals suitable for X-ray diffraction were obtained after a few days.

Refinement top

The H atoms were positioned geometrically, with C—H, N—H distances of 0.95 and 0.86 Å respectively, and constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C,N). The water H atoms were initially located in a difference Fourier map and refined with distance restraints of d(O—H1) = 0.83 (2) with all Uiso(H) values restained to have the same value.

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2010); software used to prepare material for publication: WinGX Farrugia (1999).

Figures top
[Figure 1] Fig. 1. The asymmetric unit of the title compound with displacement ellipsoids drawn drawn at the 50% probability level. The minor component of disorder in the cation is not shown.
[Figure 2] Fig. 2. Crystal packing of the title compound, showing the components linked via N—H···O and O—H···O hydrogen bonds (dashed lines) forming a three-dimensional network. The disorder is not shown.
2-Aminopyridinium trans-diaquabis(oxalato-κ2O,O)chromate(III) top
Crystal data top
(C5H7N2)[Cr(H2O)2(C2O4)2]F(000) = 732
Mr = 359.20Dx = 1.843 Mg m−3
Monoclinic, IaMo Kα radiation, λ = 0.71073 Å
Hall symbol: I -2yaCell parameters from 3716 reflections
a = 6.8627 (14) Åθ = 2.4–30.7°
b = 19.434 (4) ŵ = 0.94 mm−1
c = 9.854 (2) ÅT = 100 K
β = 99.90 (3)°Prism, blue
V = 1294.7 (5) Å30.23 × 0.15 × 0.10 mm
Z = 4
Data collection top
Bruker SMART APEX CCD
diffractometer		3716 independent reflections
Radiation source: fine-focus sealed tube3391 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.035
φ and ω scansθmax = 30.7°, θmin = 2.4°
Absorption correction: multi-scan
(SADABS; Bruker, 2004)		h = −9→9
Tmin = 0.811, Tmax = 0.912k = −27→26
9645 measured reflectionsl = −13→13
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.039H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.088 w = 1/[σ2(Fo2) + (0.0372P)2 + 2.2822P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max < 0.001
3716 reflectionsΔρmax = 0.52 e Å−3
241 parametersΔρmin = −0.30 e Å−3
21 restraintsAbsolute structure: Flack (1983), 1793 Friedel pairs
Primary atom site location: structure-invariant direct methodsFlack parameter: 0.25 (2)
Crystal data top
(C5H7N2)[Cr(H2O)2(C2O4)2]V = 1294.7 (5) Å3
Mr = 359.20Z = 4
Monoclinic, IaMo Kα radiation
a = 6.8627 (14) ŵ = 0.94 mm−1
b = 19.434 (4) ÅT = 100 K
c = 9.854 (2) Å0.23 × 0.15 × 0.10 mm
β = 99.90 (3)°
Data collection top
Bruker SMART APEX CCD
diffractometer		3716 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2004)		3391 reflections with I > 2σ(I)
Tmin = 0.811, Tmax = 0.912Rint = 0.035
9645 measured reflectionsθmax = 30.7°
Refinement top
R[F2 > 2σ(F2)] = 0.039H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.088Δρmax = 0.52 e Å−3
S = 1.04Δρmin = −0.30 e Å−3
3716 reflectionsAbsolute structure: Flack (1983), 1793 Friedel pairs
241 parametersFlack parameter: 0.25 (2)
21 restraints
Special details top

Experimental. A mixture of 2-aminopyridine (1 mmol, 100 mg) and oxalic acid (2 mmol, 260 mg) was dissolved in 30 ml of ethanol. An aqueous solution (20 ml) of CrCl3.6H2O (1 mmol, 266.5 mg) was added in successive small portions and stirred for 4 h continuously. The final blue-violet solution obtained was left at room temperature and crystals suitable for X-ray diffraction were obtained after a few days.

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Cr10.19814 (16)0.342519 (16)0.68436 (13)0.01109 (9)
C110.2455 (5)0.48129 (16)0.7396 (4)0.0177 (7)
C120.1032 (5)0.47555 (17)0.6004 (3)0.0195 (7)
O110.2936 (4)0.53790 (12)0.7885 (3)0.0321 (6)
O120.0359 (4)0.52679 (12)0.5348 (3)0.0282 (6)
O140.3031 (4)0.42294 (13)0.7934 (3)0.0183 (5)
O130.0649 (4)0.41336 (12)0.5602 (3)0.0180 (5)
C210.2715 (5)0.20807 (17)0.7621 (3)0.0135 (6)
C220.1519 (5)0.20649 (17)0.6142 (4)0.0145 (6)
O220.0979 (3)0.26575 (12)0.5654 (2)0.0155 (5)
O210.3152 (3)0.26885 (12)0.8085 (2)0.0134 (5)
O240.3136 (5)0.15470 (11)0.8242 (3)0.0221 (7)
O230.1161 (5)0.15033 (11)0.5525 (3)0.0201 (6)
OW1−0.0319 (4)0.33987 (10)0.7854 (3)0.0145 (5)
OW20.4360 (4)0.34394 (10)0.5912 (3)0.0180 (5)
N10.2574 (5)0.01644 (13)0.7419 (4)0.0213 (9)0.800 (7)
H1A0.32240.02710.82410.026*0.800 (7)
H1B0.21000.04920.68390.026*0.800 (7)
N20.3078 (5)−0.09776 (18)0.7994 (3)0.0141 (8)0.800 (7)
H20.3733−0.08400.87940.017*0.800 (7)
C10.2309 (6)−0.04927 (14)0.7051 (4)0.0134 (8)0.800 (7)
C60.1323 (6)−0.0728 (2)0.5772 (4)0.0150 (8)0.800 (7)
H60.0779−0.04090.50800.018*0.800 (7)
C50.1146 (6)−0.1417 (2)0.5524 (4)0.0180 (9)0.800 (7)
H50.0494−0.15740.46500.022*0.800 (7)
C40.1916 (6)−0.19022 (15)0.6546 (4)0.0161 (9)0.800 (7)
H40.1756−0.23820.63830.019*0.800 (7)
C30.2877 (6)−0.1664 (2)0.7750 (4)0.0152 (9)0.800 (7)
H30.3429−0.19800.84470.018*0.800 (7)
N1A0.161 (2)0.0179 (4)0.6157 (15)0.031 (4)*0.200 (7)
H1A10.20890.04790.67960.037*0.200 (7)
H1A20.09950.03230.53480.037*0.200 (7)
N2A0.275 (2)−0.0690 (6)0.7682 (10)0.021 (3)*0.200 (7)
H2A10.3211−0.03700.82850.025*0.200 (7)
C1A0.180 (2)−0.0492 (4)0.6414 (12)0.011 (3)*0.200 (7)
C6A0.101 (2)−0.1015 (6)0.5499 (9)0.007 (3)*0.200 (7)
H6A0.0292−0.09000.46170.009*0.200 (7)
C5A0.129 (3)−0.1687 (5)0.5876 (14)0.024 (5)*0.200 (7)
H5A0.0816−0.20390.52340.028*0.200 (7)
C4A0.227 (2)−0.1868 (5)0.7210 (16)0.020 (4)*0.200 (7)
H4A0.2377−0.23350.74980.024*0.200 (7)
C3A0.303 (2)−0.1361 (7)0.8054 (11)0.018 (4)*0.200 (7)
H3A0.3775−0.14710.89300.022*0.200 (7)
HW1A0.016 (6)0.3359 (17)0.867 (2)0.028*
HW1B−0.099 (5)0.3728 (13)0.764 (4)0.028*
HW2A0.406 (6)0.3418 (16)0.5044 (19)0.028*
HW2B0.485 (5)0.3815 (12)0.600 (4)0.028*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cr10.01435 (16)0.00763 (14)0.01064 (15)0.0002 (2)0.00028 (11)0.0000 (2)
C110.0265 (17)0.0098 (12)0.0212 (14)−0.0049 (11)0.0168 (13)−0.0041 (10)
C120.0276 (17)0.0154 (15)0.0190 (15)0.0026 (12)0.0138 (13)0.0021 (12)
O110.0492 (16)0.0181 (11)0.0355 (14)−0.0159 (10)0.0257 (12)−0.0135 (10)
O120.0499 (15)0.0123 (10)0.0273 (12)0.0118 (10)0.0205 (11)0.0068 (9)
O140.0220 (11)0.0174 (12)0.0157 (10)−0.0056 (9)0.0036 (9)−0.0046 (9)
O130.0271 (13)0.0100 (11)0.0181 (11)0.0048 (8)0.0071 (10)0.0029 (8)
C210.0142 (13)0.0143 (15)0.0134 (13)0.0026 (11)0.0067 (10)0.0014 (11)
C220.0155 (14)0.0128 (14)0.0167 (14)−0.0029 (11)0.0068 (11)−0.0014 (11)
O220.0213 (12)0.0118 (12)0.0133 (10)−0.0012 (8)0.0029 (9)−0.0013 (8)
O210.0150 (10)0.0115 (11)0.0126 (10)0.0021 (8)−0.0008 (8)0.0015 (8)
O240.0332 (15)0.0117 (12)0.0247 (14)0.0056 (9)0.0147 (11)0.0070 (8)
O230.0277 (13)0.0115 (11)0.0239 (13)−0.0059 (9)0.0121 (10)−0.0076 (8)
OW10.0145 (12)0.0110 (11)0.0185 (12)0.0034 (7)0.0047 (10)0.0008 (7)
OW20.0208 (14)0.0133 (12)0.0198 (12)−0.0025 (7)0.0031 (10)−0.0011 (7)
N10.0254 (17)0.0137 (14)0.0246 (16)−0.0009 (11)0.0033 (13)−0.0023 (11)
N20.0150 (15)0.0179 (19)0.0084 (13)0.0007 (12)−0.0013 (11)0.0031 (12)
C10.016 (2)0.0140 (14)0.011 (2)0.0005 (12)0.0032 (15)0.0028 (12)
C60.0124 (17)0.020 (2)0.0107 (16)0.0040 (14)−0.0026 (13)−0.0003 (15)
C50.0127 (17)0.024 (2)0.0158 (18)0.0029 (16)−0.0016 (13)−0.0073 (16)
C40.0159 (18)0.0116 (14)0.020 (2)−0.0013 (14)0.0019 (19)−0.0036 (12)
C30.0151 (18)0.0116 (17)0.0193 (19)−0.0014 (14)0.0039 (14)−0.0011 (14)
Geometric parameters (Å, º) top
Cr1—O221.949 (2)N2—C11.364 (4)
Cr1—O131.960 (2)N2—H20.8800
Cr1—O141.962 (2)C1—C61.402 (5)
Cr1—O211.963 (2)C6—C51.363 (5)
Cr1—OW22.006 (3)C6—H60.9500
Cr1—OW12.007 (3)C5—C41.414 (5)
C11—O111.223 (4)C5—H50.9500
C11—O141.285 (4)C4—C31.337 (5)
C11—C121.545 (4)C4—H40.9500
C12—O121.233 (4)C3—H30.9500
C12—O131.285 (4)N1A—C1A1.331 (4)
C21—O241.214 (4)N1A—H1A10.8800
C21—O211.283 (4)N1A—H1A20.8800
C21—C221.545 (3)N2A—C3A1.359 (5)
C22—O231.253 (4)N2A—C1A1.363 (5)
C22—O221.278 (4)N2A—H2A10.8800
OW1—HW1A0.816 (18)C1A—C6A1.402 (5)
OW1—HW1B0.796 (18)C6A—C5A1.363 (5)
OW2—HW2A0.846 (18)C6A—H6A0.9500
OW2—HW2B0.803 (18)C5A—C4A1.414 (6)
N1—C11.331 (3)C5A—H5A0.9500
N1—H1A0.8800C4A—C3A1.337 (6)
N1—H1B0.8800C4A—H4A0.9500
N2—C31.358 (4)C3A—H3A0.9500
O22—Cr1—O1394.80 (11)C3—N2—C1122.9 (3)
O22—Cr1—O14176.23 (12)C3—N2—H2118.6
O13—Cr1—O1482.55 (9)C1—N2—H2118.6
O22—Cr1—O2183.15 (7)N1—C1—N2117.3 (4)
O13—Cr1—O21176.38 (11)N1—C1—C6125.5 (4)
O14—Cr1—O2199.63 (11)N2—C1—C6117.2 (3)
O22—Cr1—OW288.05 (9)C5—C6—C1119.8 (3)
O13—Cr1—OW291.94 (10)C5—C6—H6120.1
O14—Cr1—OW289.36 (10)C1—C6—H6120.1
O21—Cr1—OW290.98 (10)C6—C5—C4121.1 (3)
O22—Cr1—OW193.02 (9)C6—C5—H5119.5
O13—Cr1—OW190.31 (10)C4—C5—H5119.5
O14—Cr1—OW189.68 (10)C3—C4—C5117.9 (3)
O21—Cr1—OW186.82 (9)C3—C4—H4121.0
OW2—Cr1—OW1177.42 (14)C5—C4—H4121.0
O11—C11—O14126.0 (4)C4—C3—N2121.1 (3)
O11—C11—C12120.1 (3)C4—C3—H3119.4
O14—C11—C12113.9 (3)N2—C3—H3119.4
O12—C12—O13124.1 (3)C1A—N1A—H1A1120.0
O12—C12—C11122.0 (3)C1A—N1A—H1A2120.0
O13—C12—C11114.0 (3)H1A1—N1A—H1A2120.0
C11—O14—Cr1114.8 (2)C3A—N2A—C1A122.7 (4)
C12—O13—Cr1114.8 (2)C3A—N2A—H2A1118.6
O24—C21—O21125.9 (3)C1A—N2A—H2A1118.6
O24—C21—C22120.0 (4)N1A—C1A—N2A117.8 (5)
O21—C21—C22114.1 (3)N1A—C1A—C6A125.0 (5)
O23—C22—O22125.6 (4)N2A—C1A—C6A117.1 (3)
O23—C22—C21120.2 (4)C5A—C6A—C1A120.0 (4)
O22—C22—C21114.2 (3)C5A—C6A—H6A120.0
C22—O22—Cr1114.4 (2)C1A—C6A—H6A120.0
C21—O21—Cr1113.8 (2)C6A—C5A—C4A120.9 (4)
Cr1—OW1—HW1A106 (3)C6A—C5A—H5A119.6
Cr1—OW1—HW1B108 (3)C4A—C5A—H5A119.6
HW1A—OW1—HW1B117 (3)C3A—C4A—C5A117.8 (4)
Cr1—OW2—HW2A113 (3)C3A—C4A—H4A121.1
Cr1—OW2—HW2B109 (3)C5A—C4A—H4A121.1
HW2A—OW2—HW2B100 (3)C4A—C3A—N2A121.3 (4)
C1—N1—H1A120.0C4A—C3A—H3A119.4
C1—N1—H1B120.0N2A—C3A—H3A119.4
H1A—N1—H1B120.0
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
OW1—HW1A···O23i0.82 (2)1.86 (2)2.660 (4)166 (3)
OW1—HW1B···O11ii0.80 (2)1.92 (2)2.663 (3)156 (4)
OW2—HW2A···O24iii0.85 (2)1.78 (2)2.621 (4)172 (4)
OW2—HW2B···O12iv0.80 (2)1.95 (2)2.687 (3)153 (4)
N1—H1A···O12v0.882.333.183 (5)164
N1—H1B···O230.882.383.251 (4)171
N2—H2···O13v0.882.022.865 (3)159
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) x−1/2, −y+1, z; (iii) x, −y+1/2, z−1/2; (iv) x+1/2, −y+1, z; (v) x+1/2, y−1/2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
OW1—HW1A···O23i0.816 (18)1.86 (2)2.660 (4)166 (3)
OW1—HW1B···O11ii0.796 (18)1.92 (2)2.663 (3)156 (4)
OW2—HW2A···O24iii0.846 (18)1.782 (19)2.621 (4)172 (4)
OW2—HW2B···O12iv0.803 (18)1.95 (2)2.687 (3)153 (4)
N1—H1A···O12v0.882.333.183 (5)164.4
N1—H1B···O230.882.383.251 (4)170.5
N2—H2···O13v0.882.022.865 (3)159.3
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) x−1/2, −y+1, z; (iii) x, −y+1/2, z−1/2; (iv) x+1/2, −y+1, z; (v) x+1/2, y−1/2, z+1/2.
Acknowledgements top

The authors thank Professor Barthelemy Nyasse (Organic Chemistry Department, University of Yaounde I) for the donation of 2-aminopyridin and Tobias Storp (RWTH Aachen) for his technical support during the X-ray experiments.

references
References top

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