2-Amino­pyridinium trans-diaqua­bis­(oxalato-κ2O,O)chromate(III)

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

doi:10.1107/S1600536812040950

metal-organic compounds

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ISSN: 2056-9890

Volume 68| Part 11| November 2012| Pages m1325-m1326

doi:10.1107/S1600536812040950

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2-Aminopyridinium trans-diaquabis(oxalato-κ²O,O)chromate(III)

Justin Nenwa,^a ^* Gouet Bebga,^b Signé Martin,^a Michel M. Bélombé,^a Mohammed Mbarki ^c and Boniface P. T. Fokwa ^c

^aDepartment of Inorganic Chemistry, University of Yaounde I, POB 812 Yaounde, Cameroon, ^bHigher Teacher Training College, POB 47, University of Yaounde 1, Cameroon, and ^cInstitut für Anorganische Chemie, RWTH Aachen, D-52056 Aachen, Germany
^*Correspondence e-mail: jnenwa@yahoo.fr

(Received 14 September 2012; accepted 28 September 2012; online 6 October 2012)

In the title hybrid salt, (C₅H₇N₂)[Cr(H₂O)₂(C₂O₄)₂], the Cr^III 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).

Related literature

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

Crystal data

(C₅H₇N₂)[Cr(H₂O)₂(C₂O₄)₂]
M_r = 359.20
Monoclinic, I a
a = 6.8627 (14) Å
b = 19.434 (4) Å
c = 9.854 (2) Å
β = 99.90 (3)°
V = 1294.7 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.94 mm⁻¹
T = 100 K
0.23 × 0.15 × 0.10 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2004 ) T_min = 0.811, T_max = 0.912
9645 measured reflections
3716 independent reflections
3391 reflections with I > 2σ(I)
R_int = 0.035

Refinement

R[F² > 2σ(F²)] = 0.039
wR(F²) = 0.088
S = 1.04
3716 reflections
241 parameters
21 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.52 e Å⁻³
Δρ_min = −0.30 e Å⁻³
Absolute structure: Flack (1983 ), 1793 Friedel pairs
Flack parameter: 0.25 (2)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
OW1—HW1A⋯O23ⁱ	0.82 (2)	1.86 (2)	2.660 (4)	166 (3)
OW1—HW1B⋯O11ⁱⁱ	0.80 (2)	1.92 (2)	2.663 (3)	156 (4)
OW2—HW2A⋯O24ⁱⁱⁱ	0.85 (2)	1.78 (2)	2.621 (4)	172 (4)
OW2—HW2B⋯O12^iv	0.80 (2)	1.95 (2)	2.687 (3)	153 (4)
N1—H1A⋯O12^v	0.88	2.33	3.183 (5)	164
N1—H1B⋯O23	0.88	2.38	3.251 (4)	171
N2—H2⋯O13^v	0.88	2.02	2.865 (3)	159
Symmetry codes: (i) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (ii) $[x-{\script{1\over 2}}, -y+1, z]$ ; (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iv) $[x+{\script{1\over 2}}, -y+1, z]$ ; (v) $[x+{\script{1\over 2}}, y-{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

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: DIAMOND (Brandenburg, 2010 ); software used to prepare material for publication: WinGX Farrugia (1999 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536812040950/lh5534sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812040950/lh5534Isup2.hkl

checkCIF report

Comment top

The coordination chemistry of oxalates (C₂O₄^2-) 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 Cr^III 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.

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

	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.
	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
M_r = 359.20	D_x = 1.843 Mg m⁻³
Monoclinic, Ia	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: I -2ya	Cell parameters from 3716 reflections
a = 6.8627 (14) Å	θ = 2.4–30.7°
b = 19.434 (4) Å	µ = 0.94 mm⁻¹
c = 9.854 (2) Å	T = 100 K
β = 99.90 (3)°	Prism, blue
V = 1294.7 (5) Å³	0.23 × 0.15 × 0.10 mm
Z = 4

Data collection top

Bruker SMART APEX CCD diffractometer	3716 independent reflections
Radiation source: fine-focus sealed tube	3391 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.035
ϕ and ω scans	θ_max = 30.7°, θ_min = 2.4°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −9→9
T_min = 0.811, T_max = 0.912	k = −27→26
9645 measured reflections	l = −13→13

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.039	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.088	w = 1/[σ²(F_o²) + (0.0372P)² + 2.2822P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max < 0.001
3716 reflections	Δρ_max = 0.52 e Å⁻³
241 parameters	Δρ_min = −0.30 e Å⁻³
21 restraints	Absolute structure: Flack (1983), 1793 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.25 (2)

Crystal data top

(C₅H₇N₂)[Cr(H₂O)₂(C₂O₄)₂]	V = 1294.7 (5) Å³
M_r = 359.20	Z = 4
Monoclinic, Ia	Mo Kα radiation
a = 6.8627 (14) Å	µ = 0.94 mm⁻¹
b = 19.434 (4) Å	T = 100 K
c = 9.854 (2) Å	0.23 × 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)
T_min = 0.811, T_max = 0.912	R_int = 0.035
9645 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.088	Δρ_max = 0.52 e Å⁻³
S = 1.04	Δρ_min = −0.30 e Å⁻³
3716 reflections	Absolute structure: Flack (1983), 1793 Friedel pairs
241 parameters	Absolute structure 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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Cr1	0.19814 (16)	0.342519 (16)	0.68436 (13)	0.01109 (9)
C11	0.2455 (5)	0.48129 (16)	0.7396 (4)	0.0177 (7)
C12	0.1032 (5)	0.47555 (17)	0.6004 (3)	0.0195 (7)
O11	0.2936 (4)	0.53790 (12)	0.7885 (3)	0.0321 (6)
O12	0.0359 (4)	0.52679 (12)	0.5348 (3)	0.0282 (6)
O14	0.3031 (4)	0.42294 (13)	0.7934 (3)	0.0183 (5)
O13	0.0649 (4)	0.41336 (12)	0.5602 (3)	0.0180 (5)
C21	0.2715 (5)	0.20807 (17)	0.7621 (3)	0.0135 (6)
C22	0.1519 (5)	0.20649 (17)	0.6142 (4)	0.0145 (6)
O22	0.0979 (3)	0.26575 (12)	0.5654 (2)	0.0155 (5)
O21	0.3152 (3)	0.26885 (12)	0.8085 (2)	0.0134 (5)
O24	0.3136 (5)	0.15470 (11)	0.8242 (3)	0.0221 (7)
O23	0.1161 (5)	0.15033 (11)	0.5525 (3)	0.0201 (6)
OW1	−0.0319 (4)	0.33987 (10)	0.7854 (3)	0.0145 (5)
OW2	0.4360 (4)	0.34394 (10)	0.5912 (3)	0.0180 (5)
N1	0.2574 (5)	0.01644 (13)	0.7419 (4)	0.0213 (9)	0.800 (7)
H1A	0.3224	0.0271	0.8241	0.026*	0.800 (7)
H1B	0.2100	0.0492	0.6839	0.026*	0.800 (7)
N2	0.3078 (5)	−0.09776 (18)	0.7994 (3)	0.0141 (8)	0.800 (7)
H2	0.3733	−0.0840	0.8794	0.017*	0.800 (7)
C1	0.2309 (6)	−0.04927 (14)	0.7051 (4)	0.0134 (8)	0.800 (7)
C6	0.1323 (6)	−0.0728 (2)	0.5772 (4)	0.0150 (8)	0.800 (7)
H6	0.0779	−0.0409	0.5080	0.018*	0.800 (7)
C5	0.1146 (6)	−0.1417 (2)	0.5524 (4)	0.0180 (9)	0.800 (7)
H5	0.0494	−0.1574	0.4650	0.022*	0.800 (7)
C4	0.1916 (6)	−0.19022 (15)	0.6546 (4)	0.0161 (9)	0.800 (7)
H4	0.1756	−0.2382	0.6383	0.019*	0.800 (7)
C3	0.2877 (6)	−0.1664 (2)	0.7750 (4)	0.0152 (9)	0.800 (7)
H3	0.3429	−0.1980	0.8447	0.018*	0.800 (7)
N1A	0.161 (2)	0.0179 (4)	0.6157 (15)	0.031 (4)*	0.200 (7)
H1A1	0.2089	0.0479	0.6796	0.037*	0.200 (7)
H1A2	0.0995	0.0323	0.5348	0.037*	0.200 (7)
N2A	0.275 (2)	−0.0690 (6)	0.7682 (10)	0.021 (3)*	0.200 (7)
H2A1	0.3211	−0.0370	0.8285	0.025*	0.200 (7)
C1A	0.180 (2)	−0.0492 (4)	0.6414 (12)	0.011 (3)*	0.200 (7)
C6A	0.101 (2)	−0.1015 (6)	0.5499 (9)	0.007 (3)*	0.200 (7)
H6A	0.0292	−0.0900	0.4617	0.009*	0.200 (7)
C5A	0.129 (3)	−0.1687 (5)	0.5876 (14)	0.024 (5)*	0.200 (7)
H5A	0.0816	−0.2039	0.5234	0.028*	0.200 (7)
C4A	0.227 (2)	−0.1868 (5)	0.7210 (16)	0.020 (4)*	0.200 (7)
H4A	0.2377	−0.2335	0.7498	0.024*	0.200 (7)
C3A	0.303 (2)	−0.1361 (7)	0.8054 (11)	0.018 (4)*	0.200 (7)
H3A	0.3775	−0.1471	0.8930	0.022*	0.200 (7)
HW1A	0.016 (6)	0.3359 (17)	0.867 (2)	0.028*
HW1B	−0.099 (5)	0.3728 (13)	0.764 (4)	0.028*
HW2A	0.406 (6)	0.3418 (16)	0.5044 (19)	0.028*
HW2B	0.485 (5)	0.3815 (12)	0.600 (4)	0.028*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cr1	0.01435 (16)	0.00763 (14)	0.01064 (15)	0.0002 (2)	0.00028 (11)	0.0000 (2)
C11	0.0265 (17)	0.0098 (12)	0.0212 (14)	−0.0049 (11)	0.0168 (13)	−0.0041 (10)
C12	0.0276 (17)	0.0154 (15)	0.0190 (15)	0.0026 (12)	0.0138 (13)	0.0021 (12)
O11	0.0492 (16)	0.0181 (11)	0.0355 (14)	−0.0159 (10)	0.0257 (12)	−0.0135 (10)
O12	0.0499 (15)	0.0123 (10)	0.0273 (12)	0.0118 (10)	0.0205 (11)	0.0068 (9)
O14	0.0220 (11)	0.0174 (12)	0.0157 (10)	−0.0056 (9)	0.0036 (9)	−0.0046 (9)
O13	0.0271 (13)	0.0100 (11)	0.0181 (11)	0.0048 (8)	0.0071 (10)	0.0029 (8)
C21	0.0142 (13)	0.0143 (15)	0.0134 (13)	0.0026 (11)	0.0067 (10)	0.0014 (11)
C22	0.0155 (14)	0.0128 (14)	0.0167 (14)	−0.0029 (11)	0.0068 (11)	−0.0014 (11)
O22	0.0213 (12)	0.0118 (12)	0.0133 (10)	−0.0012 (8)	0.0029 (9)	−0.0013 (8)
O21	0.0150 (10)	0.0115 (11)	0.0126 (10)	0.0021 (8)	−0.0008 (8)	0.0015 (8)
O24	0.0332 (15)	0.0117 (12)	0.0247 (14)	0.0056 (9)	0.0147 (11)	0.0070 (8)
O23	0.0277 (13)	0.0115 (11)	0.0239 (13)	−0.0059 (9)	0.0121 (10)	−0.0076 (8)
OW1	0.0145 (12)	0.0110 (11)	0.0185 (12)	0.0034 (7)	0.0047 (10)	0.0008 (7)
OW2	0.0208 (14)	0.0133 (12)	0.0198 (12)	−0.0025 (7)	0.0031 (10)	−0.0011 (7)
N1	0.0254 (17)	0.0137 (14)	0.0246 (16)	−0.0009 (11)	0.0033 (13)	−0.0023 (11)
N2	0.0150 (15)	0.0179 (19)	0.0084 (13)	0.0007 (12)	−0.0013 (11)	0.0031 (12)
C1	0.016 (2)	0.0140 (14)	0.011 (2)	0.0005 (12)	0.0032 (15)	0.0028 (12)
C6	0.0124 (17)	0.020 (2)	0.0107 (16)	0.0040 (14)	−0.0026 (13)	−0.0003 (15)
C5	0.0127 (17)	0.024 (2)	0.0158 (18)	0.0029 (16)	−0.0016 (13)	−0.0073 (16)
C4	0.0159 (18)	0.0116 (14)	0.020 (2)	−0.0013 (14)	0.0019 (19)	−0.0036 (12)
C3	0.0151 (18)	0.0116 (17)	0.0193 (19)	−0.0014 (14)	0.0039 (14)	−0.0011 (14)

Geometric parameters (Å, º) top

Cr1—O22	1.949 (2)	N2—C1	1.364 (4)
Cr1—O13	1.960 (2)	N2—H2	0.8800
Cr1—O14	1.962 (2)	C1—C6	1.402 (5)
Cr1—O21	1.963 (2)	C6—C5	1.363 (5)
Cr1—OW2	2.006 (3)	C6—H6	0.9500
Cr1—OW1	2.007 (3)	C5—C4	1.414 (5)
C11—O11	1.223 (4)	C5—H5	0.9500
C11—O14	1.285 (4)	C4—C3	1.337 (5)
C11—C12	1.545 (4)	C4—H4	0.9500
C12—O12	1.233 (4)	C3—H3	0.9500
C12—O13	1.285 (4)	N1A—C1A	1.331 (4)
C21—O24	1.214 (4)	N1A—H1A1	0.8800
C21—O21	1.283 (4)	N1A—H1A2	0.8800
C21—C22	1.545 (3)	N2A—C3A	1.359 (5)
C22—O23	1.253 (4)	N2A—C1A	1.363 (5)
C22—O22	1.278 (4)	N2A—H2A1	0.8800
OW1—HW1A	0.816 (18)	C1A—C6A	1.402 (5)
OW1—HW1B	0.796 (18)	C6A—C5A	1.363 (5)
OW2—HW2A	0.846 (18)	C6A—H6A	0.9500
OW2—HW2B	0.803 (18)	C5A—C4A	1.414 (6)
N1—C1	1.331 (3)	C5A—H5A	0.9500
N1—H1A	0.8800	C4A—C3A	1.337 (6)
N1—H1B	0.8800	C4A—H4A	0.9500
N2—C3	1.358 (4)	C3A—H3A	0.9500

O22—Cr1—O13	94.80 (11)	C3—N2—C1	122.9 (3)
O22—Cr1—O14	176.23 (12)	C3—N2—H2	118.6
O13—Cr1—O14	82.55 (9)	C1—N2—H2	118.6
O22—Cr1—O21	83.15 (7)	N1—C1—N2	117.3 (4)
O13—Cr1—O21	176.38 (11)	N1—C1—C6	125.5 (4)
O14—Cr1—O21	99.63 (11)	N2—C1—C6	117.2 (3)
O22—Cr1—OW2	88.05 (9)	C5—C6—C1	119.8 (3)
O13—Cr1—OW2	91.94 (10)	C5—C6—H6	120.1
O14—Cr1—OW2	89.36 (10)	C1—C6—H6	120.1
O21—Cr1—OW2	90.98 (10)	C6—C5—C4	121.1 (3)
O22—Cr1—OW1	93.02 (9)	C6—C5—H5	119.5
O13—Cr1—OW1	90.31 (10)	C4—C5—H5	119.5
O14—Cr1—OW1	89.68 (10)	C3—C4—C5	117.9 (3)
O21—Cr1—OW1	86.82 (9)	C3—C4—H4	121.0
OW2—Cr1—OW1	177.42 (14)	C5—C4—H4	121.0
O11—C11—O14	126.0 (4)	C4—C3—N2	121.1 (3)
O11—C11—C12	120.1 (3)	C4—C3—H3	119.4
O14—C11—C12	113.9 (3)	N2—C3—H3	119.4
O12—C12—O13	124.1 (3)	C1A—N1A—H1A1	120.0
O12—C12—C11	122.0 (3)	C1A—N1A—H1A2	120.0
O13—C12—C11	114.0 (3)	H1A1—N1A—H1A2	120.0
C11—O14—Cr1	114.8 (2)	C3A—N2A—C1A	122.7 (4)
C12—O13—Cr1	114.8 (2)	C3A—N2A—H2A1	118.6
O24—C21—O21	125.9 (3)	C1A—N2A—H2A1	118.6
O24—C21—C22	120.0 (4)	N1A—C1A—N2A	117.8 (5)
O21—C21—C22	114.1 (3)	N1A—C1A—C6A	125.0 (5)
O23—C22—O22	125.6 (4)	N2A—C1A—C6A	117.1 (3)
O23—C22—C21	120.2 (4)	C5A—C6A—C1A	120.0 (4)
O22—C22—C21	114.2 (3)	C5A—C6A—H6A	120.0
C22—O22—Cr1	114.4 (2)	C1A—C6A—H6A	120.0
C21—O21—Cr1	113.8 (2)	C6A—C5A—C4A	120.9 (4)
Cr1—OW1—HW1A	106 (3)	C6A—C5A—H5A	119.6
Cr1—OW1—HW1B	108 (3)	C4A—C5A—H5A	119.6
HW1A—OW1—HW1B	117 (3)	C3A—C4A—C5A	117.8 (4)
Cr1—OW2—HW2A	113 (3)	C3A—C4A—H4A	121.1
Cr1—OW2—HW2B	109 (3)	C5A—C4A—H4A	121.1
HW2A—OW2—HW2B	100 (3)	C4A—C3A—N2A	121.3 (4)
C1—N1—H1A	120.0	C4A—C3A—H3A	119.4
C1—N1—H1B	120.0	N2A—C3A—H3A	119.4
H1A—N1—H1B	120.0

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
OW1—HW1A···O23ⁱ	0.82 (2)	1.86 (2)	2.660 (4)	166 (3)
OW1—HW1B···O11ⁱⁱ	0.80 (2)	1.92 (2)	2.663 (3)	156 (4)
OW2—HW2A···O24ⁱⁱⁱ	0.85 (2)	1.78 (2)	2.621 (4)	172 (4)
OW2—HW2B···O12^iv	0.80 (2)	1.95 (2)	2.687 (3)	153 (4)
N1—H1A···O12^v	0.88	2.33	3.183 (5)	164
N1—H1B···O23	0.88	2.38	3.251 (4)	171
N2—H2···O13^v	0.88	2.02	2.865 (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.

Experimental details

Crystal data
Chemical formula	(C₅H₇N₂)[Cr(H₂O)₂(C₂O₄)₂]
M_r	359.20
Crystal system, space group	Monoclinic, Ia
Temperature (K)	100
a, b, c (Å)	6.8627 (14), 19.434 (4), 9.854 (2)
β (°)	99.90 (3)
V (Å³)	1294.7 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.94
Crystal size (mm)	0.23 × 0.15 × 0.10

Data collection
Diffractometer	Bruker SMART APEX CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2004)
T_min, T_max	0.811, 0.912
No. of measured, independent and observed [I > 2σ(I)] reflections	9645, 3716, 3391
R_int	0.035
(sin θ/λ)_max (Å⁻¹)	0.717

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.088, 1.04
No. of reflections	3716
No. of parameters	241
No. of restraints	21
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.52, −0.30
Absolute structure	Flack (1983), 1793 Friedel pairs
Absolute structure parameter	0.25 (2)

Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2010), WinGX Farrugia (1999).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
OW1—HW1A···O23ⁱ	0.816 (18)	1.86 (2)	2.660 (4)	166 (3)
OW1—HW1B···O11ⁱⁱ	0.796 (18)	1.92 (2)	2.663 (3)	156 (4)
OW2—HW2A···O24ⁱⁱⁱ	0.846 (18)	1.782 (19)	2.621 (4)	172 (4)
OW2—HW2B···O12^iv	0.803 (18)	1.95 (2)	2.687 (3)	153 (4)
N1—H1A···O12^v	0.88	2.33	3.183 (5)	164.4
N1—H1B···O23	0.88	2.38	3.251 (4)	170.5
N2—H2···O13^v	0.88	2.02	2.865 (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

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

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