2-Amino­pyridinium trans-diaqua­bis­(oxalato-κ2 O,O)chromate(III)

Justin Nenwa; Gouet Bebga; Signé Martin; Michel M Bélombé; Mohammed Mbarki; Boniface P T Fokwa

doi:10.1107/S1600536812040950

. 2012 Oct 6;68(Pt 11):m1325–m1326. doi: 10.1107/S1600536812040950

2-Aminopyridinium trans-diaquabis(oxalato-κ² O,O)chromate(III)

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

PMCID: PMC3515093 PMID: 23284320

Abstract

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,
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[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 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)

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 ▶).

Supplementary Material

Click here for additional data file.^{(19.3KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812040950/lh5534sup1.cif

e-68-m1325-sup1.cif^{(19.3KB, cif)}

Click here for additional data file.^{(178.5KB, hkl)}

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

e-68-m1325-Isup2.hkl^{(178.5KB, hkl)}

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

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

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

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.

supplementary crystallographic information

Comment

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.

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.