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Acta Cryst. (2012). E68, m1434    [ doi:10.1107/S1600536812044303 ]

Pyridinium cis-diaquabis(oxalato-[kappa]2O,O')chromate(III)

J. Nenwa, O. Befolo, B. Gouet, M. Mbarki and B. P. T. Fokwa

Abstract top

The title compound, (C5H6N)[Cr(C2O4)2(H2O)2], contains one protonated pyridine molecule and one [Cr(C2O4)2(H2O)2]- complex anion in the asymmetric unit. The CrIII in the complex anion is coordinated in a distorted octahedral environment by two O atoms from two cis water molecules and four O atoms from two chelating oxalate dianions. The crystal packing is stabilized by intermolecular N-H...O(oxalate) and O-H...O(oxalate) hydrogen bonds and by [pi]-[pi] stacking interactions (centroid-centroid distance = 3.602 Å) between pyridine rings, thereby building up a three-dimensional network.

Comment top

Recently, we have reported the structure of a few organic-inorganic hybrid salts involving various aromatic iminium cations and the complex anion, [Cr(C2O4)2(H2O)2]- in trans-geometry (Bélombé et al., 2009; Nenwa et al., 2010, 2012). In the present investigation, we wish to report the structure of a homologous salt, containing the complex anion adopting the cis-geometry and protonated pyridinium as a counter cation. This cis-anion which is somewhat less common has been observed in a similar organic-inorganic hybrid salt, with 2-amino-5-chloropyridinium as the organic cation (Chérif, Abdelhak et al., 2012).

The asymmetric unit of the title compound, (C5H6N)[Cr(C2O4)2(H2O)2] which crstallizes in space group P21/c, is shown in Fig. 1. The CrIII site in the complex anion has a distorted octahedral coordination environment build up by two O atoms (OW1, OW2) from two cis water molecules and four O atoms (O11, O12, O21, O22) from two chelating oxalate dianions. The main geometric parameters of the (C5H6N)+ cation are in agreement with those found in salts with similar cationic entities (Bélombé et al., 2009; Nenwa et al., 2010; Nenwa et al., 2012; Chérif et al., 2011; Chérif, Abdelhak et al., 2012; Chérif, Zid et al., 2012). The bond distances in the complex anion (Table 1) are comparable with those reported in the 2-amino-5-chloropyridinium compound (Chérif, Abdelhak et al., 2012). The crystal packing is stabilized by intermolecular N—H···O (oxalate) and O—H···O (oxalate) hydrogen bonds and by ππ stacking interactions [centroid-centroid distance = 3.602 Å] between pyridine rings, thereby building up a three-dimensional network (Table 2, Fig. 2).

Related literature top

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

Experimental top

Pyridine (1 mmol, 79.1 mg) and oxalic acid (2 mmol, 260 mg) were added in successive small portions in an aqueous solution (50 ml) of CrCl3.6H2O (1 mmol, 266.5 mg). The mixture was stirred for 4 h continuously. The final blue-violet solution obtained was left at room temperature and violet 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 refined.

Computing details top

Data collection: SMART (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 at the 50% probability level.
[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. ππ stacking between the protonated pyridine rings is also observed.
Pyridinium cis-diaquabis(oxalato-κ2O,O')chromate(III) top
Crystal data top
(C5H6N)[Cr(C2O4)2(H2O)2]F(000) = 700
Mr = 344.18Dx = 1.842 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P_2ybcCell parameters from 3703 reflections
a = 7.479 (2) Åθ = 1.7–30.9°
b = 24.700 (8) ŵ = 0.98 mm1
c = 7.056 (2) ÅT = 100 K
β = 107.744 (6)°Needle, violet
V = 1241.4 (6) Å30.15 × 0.04 × 0.04 mm
Z = 4
Data collection top
Bruker SMART APEX CCD
diffractometer
3703 independent reflections
Radiation source: fine-focus sealed tube2580 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.106
φ and ω scansθmax = 30.9°, θmin = 1.7°
Absorption correction: multi-scan
(SADABS; Bruker, 2004)
h = 1010
Tmin = 0.862, Tmax = 0.961k = 3433
18649 measured reflectionsl = 910
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.061Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.160H atoms treated by a mixture of independent and constrained refinement
S = 1.13 w = 1/[σ2(Fo2) + (0.0636P)2]
where P = (Fo2 + 2Fc2)/3
3703 reflections(Δ/σ)max = 0.001
206 parametersΔρmax = 0.59 e Å3
5 restraintsΔρmin = 0.69 e Å3
Crystal data top
(C5H6N)[Cr(C2O4)2(H2O)2]V = 1241.4 (6) Å3
Mr = 344.18Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.479 (2) ŵ = 0.98 mm1
b = 24.700 (8) ÅT = 100 K
c = 7.056 (2) Å0.15 × 0.04 × 0.04 mm
β = 107.744 (6)°
Data collection top
Bruker SMART APEX CCD
diffractometer
3703 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2004)
2580 reflections with I > 2σ(I)
Tmin = 0.862, Tmax = 0.961Rint = 0.106
18649 measured reflectionsθmax = 30.9°
Refinement top
R[F2 > 2σ(F2)] = 0.061H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.160Δρmax = 0.59 e Å3
S = 1.13Δρmin = 0.69 e Å3
3703 reflectionsAbsolute structure: ?
206 parametersFlack parameter: ?
5 restraintsRogers parameter: ?
Special details top

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*/Ueq
Cr10.00150 (8)0.67285 (2)0.06297 (8)0.00840 (15)
C110.3839 (5)0.67581 (15)0.0409 (5)0.0119 (7)
C120.3217 (5)0.73552 (14)0.0479 (5)0.0099 (7)
C210.0773 (5)0.61425 (14)0.2335 (5)0.0110 (7)
C220.1456 (5)0.57906 (15)0.0428 (5)0.0120 (7)
O110.2502 (3)0.64143 (10)0.0020 (4)0.0113 (5)
O120.1425 (3)0.74032 (10)0.0051 (4)0.0105 (5)
O130.4367 (4)0.77229 (11)0.0905 (4)0.0177 (6)
O140.5518 (4)0.66425 (11)0.0766 (4)0.0170 (6)
O210.0065 (3)0.65975 (10)0.2098 (4)0.0113 (5)
O220.1238 (4)0.60185 (10)0.1125 (4)0.0118 (5)
O230.0948 (4)0.59673 (10)0.3912 (4)0.0137 (5)
O240.2113 (4)0.53428 (11)0.0504 (4)0.0186 (6)
OW10.0262 (4)0.67909 (11)0.3493 (4)0.0139 (5)
OW20.2371 (4)0.71532 (11)0.1053 (4)0.0139 (5)
N10.2547 (4)0.48994 (13)0.3963 (5)0.0148 (6)
H10.20810.51520.34190.018*
C20.3312 (6)0.44697 (16)0.2871 (6)0.0177 (8)
H20.33200.44460.15530.021*
C30.2476 (5)0.49522 (15)0.5870 (6)0.0147 (7)
H30.19270.52560.65900.018*
C40.3220 (6)0.45543 (16)0.6751 (6)0.0172 (8)
H40.31640.45830.80820.021*
C50.4083 (5)0.40652 (15)0.3686 (6)0.0180 (8)
H50.46180.37650.29300.022*
C60.4059 (5)0.41073 (16)0.5641 (6)0.0161 (8)
H60.45990.38390.62120.019*
H1B0.019 (6)0.6988 (17)0.415 (6)0.032 (15)*
H2A0.310 (5)0.721 (2)0.214 (4)0.033 (15)*
H1A0.051 (8)0.6501 (17)0.419 (9)0.06 (2)*
H2B0.296 (6)0.700 (2)0.040 (6)0.06 (2)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cr10.0108 (3)0.0067 (3)0.0083 (3)0.0012 (2)0.0037 (2)0.0006 (2)
C110.0116 (16)0.0135 (17)0.0112 (17)0.0003 (13)0.0043 (13)0.0004 (14)
C120.0122 (16)0.0114 (16)0.0052 (16)0.0005 (13)0.0015 (13)0.0007 (12)
C210.0141 (17)0.0108 (17)0.0102 (17)0.0011 (13)0.0065 (14)0.0005 (13)
C220.0157 (17)0.0120 (17)0.0095 (17)0.0011 (13)0.0056 (14)0.0046 (14)
O110.0123 (12)0.0093 (12)0.0129 (13)0.0006 (9)0.0048 (10)0.0011 (9)
O120.0116 (12)0.0086 (12)0.0110 (13)0.0004 (9)0.0031 (10)0.0003 (9)
O130.0148 (13)0.0116 (13)0.0250 (16)0.0046 (10)0.0035 (11)0.0026 (11)
O140.0128 (12)0.0175 (14)0.0222 (15)0.0043 (10)0.0073 (11)0.0070 (11)
O210.0132 (12)0.0094 (12)0.0123 (13)0.0012 (9)0.0053 (10)0.0014 (9)
O220.0187 (13)0.0109 (13)0.0074 (12)0.0035 (10)0.0061 (10)0.0021 (10)
O230.0205 (13)0.0112 (13)0.0109 (13)0.0017 (10)0.0069 (10)0.0004 (10)
O240.0351 (16)0.0092 (13)0.0144 (14)0.0103 (11)0.0119 (12)0.0024 (10)
OW10.0217 (14)0.0106 (13)0.0106 (13)0.0050 (11)0.0069 (11)0.0003 (10)
OW20.0108 (12)0.0163 (14)0.0150 (14)0.0020 (10)0.0044 (11)0.0048 (11)
N10.0198 (16)0.0104 (15)0.0167 (16)0.0004 (12)0.0090 (13)0.0021 (12)
C20.028 (2)0.0151 (19)0.0117 (18)0.0035 (16)0.0091 (16)0.0003 (14)
C30.0166 (18)0.0114 (17)0.0139 (18)0.0028 (13)0.0013 (14)0.0026 (14)
C40.024 (2)0.0173 (19)0.0100 (18)0.0015 (15)0.0040 (15)0.0013 (14)
C50.024 (2)0.0083 (17)0.019 (2)0.0024 (14)0.0037 (16)0.0042 (14)
C60.0199 (19)0.0129 (18)0.017 (2)0.0007 (14)0.0068 (15)0.0062 (14)
Geometric parameters (Å, º) top
Cr1—O111.959 (3)OW1—H1B0.814 (19)
Cr1—O221.960 (3)OW1—H1A0.86 (5)
Cr1—O121.963 (3)OW2—H2A0.806 (19)
Cr1—O211.963 (3)OW2—H2B0.818 (19)
Cr1—OW11.978 (3)N1—C21.334 (5)
Cr1—OW21.993 (3)N1—C31.337 (5)
C11—O141.237 (4)N1—H10.8600
C11—O111.276 (4)C2—C51.365 (5)
C11—C121.552 (5)C2—H20.9300
C12—O131.224 (4)C3—C41.369 (5)
C12—O121.286 (4)C3—H30.9300
C21—O231.238 (4)C4—C61.388 (5)
C21—O211.275 (4)C4—H40.9300
C21—C221.552 (5)C5—C61.378 (6)
C22—O241.218 (4)C5—H50.9300
C22—O221.285 (4)C6—H60.9300
O11—Cr1—O2292.85 (11)C12—O12—Cr1115.7 (2)
O11—Cr1—O1282.18 (10)C21—O21—Cr1114.0 (2)
O22—Cr1—O12174.30 (11)C22—O22—Cr1114.4 (2)
O11—Cr1—O2191.36 (11)Cr1—OW1—H1B135 (3)
O22—Cr1—O2183.09 (11)Cr1—OW1—H1A117 (4)
O12—Cr1—O2194.19 (11)H1B—OW1—H1A103 (4)
O11—Cr1—OW192.26 (11)Cr1—OW2—H2A123 (4)
O22—Cr1—OW189.69 (11)Cr1—OW2—H2B106 (4)
O12—Cr1—OW193.28 (11)H2A—OW2—H2B107 (3)
O21—Cr1—OW1172.08 (11)C2—N1—C3122.5 (3)
O11—Cr1—OW2171.04 (11)C2—N1—H1118.8
O22—Cr1—OW295.79 (11)C3—N1—H1118.8
O12—Cr1—OW289.07 (11)N1—C2—C5120.1 (4)
O21—Cr1—OW287.33 (11)N1—C2—H2120.0
OW1—Cr1—OW290.17 (12)C5—C2—H2120.0
O14—C11—O11124.7 (3)N1—C3—C4119.4 (3)
O14—C11—C12120.6 (3)N1—C3—H3120.3
O11—C11—C12114.8 (3)C4—C3—H3120.3
O13—C12—O12126.4 (3)C3—C4—C6119.4 (4)
O13—C12—C11121.2 (3)C3—C4—H4120.3
O12—C12—C11112.4 (3)C6—C4—H4120.3
O23—C21—O21126.0 (3)C2—C5—C6119.2 (4)
O23—C21—C22119.1 (3)C2—C5—H5120.4
O21—C21—C22114.9 (3)C6—C5—H5120.4
O24—C22—O22126.3 (3)C5—C6—C4119.4 (4)
O24—C22—C21120.1 (3)C5—C6—H6120.3
O22—C22—C21113.6 (3)C4—C6—H6120.3
C11—O11—Cr1114.8 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O240.862.102.783 (4)136
N1—H1···O230.862.172.901 (4)143
OW1—H1B···O12i0.81 (2)1.94 (2)2.720 (4)162 (5)
OW1—H1A···O23ii0.86 (5)1.84 (5)2.680 (4)168 (5)
OW2—H2A···O13iii0.81 (2)1.98 (3)2.732 (4)154 (4)
OW2—H2B···O14iv0.82 (2)1.83 (2)2.639 (4)173 (5)
Symmetry codes: (i) x, y+3/2, z+1/2; (ii) x, y, z+1; (iii) x+1, y+3/2, z+1/2; (iv) x+1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O240.862.102.783 (4)135.5
N1—H1···O230.862.172.901 (4)142.5
OW1—H1B···O12i0.814 (19)1.94 (2)2.720 (4)162 (5)
OW1—H1A···O23ii0.86 (5)1.84 (5)2.680 (4)168 (5)
OW2—H2A···O13iii0.806 (19)1.98 (3)2.732 (4)154 (4)
OW2—H2B···O14iv0.818 (19)1.83 (2)2.639 (4)173 (5)
Symmetry codes: (i) x, y+3/2, z+1/2; (ii) x, y, z+1; (iii) x+1, y+3/2, z+1/2; (iv) x+1, y, z.
Acknowledgements top

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

references
References top

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