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Acta Cryst. (2010). E66, m1410    [ doi:10.1107/S1600536810040353 ]

4-(Dimethylamino)pyridinium trans-diaquabis[oxalato(2-)-[kappa]2O1,O2]chromate(III)

J. Nenwa, M. M. Belombe, J. Ngoune and B. P. T. Fokwa

Abstract top

In the title salt, (C7H11N2)[Cr(C2O4)2(H2O)2], the asymmetric unit contains one half-cation and one half-anion. The Cr atom, the C and N atoms involved in C- N(exocyclic) bonding and the N and H atoms of N-H groups lie on twofold rotation axis. The CrIII atom of the complex anion is six-coordinated in a distorted (4 + 2) octahedral geometry with four equatorial O atoms of two nearly coplanar oxalate and two quasi-axial aqua O atoms. In the crystal, the protonated N atoms of the pyridine rings are hydrogen bonded to the carbonyl O atoms of the anions, forming chains along [010]. These chains are connected by lateral O-H...O hydrogen bonds, stabilizing the structure.

Comment top

The coordination chemistry of oxalate (C2O42-) continues receiving considerable attention, 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]. Recently, we published the structure of an organic-inorganic hybrid salt involving the quinolinium cation, [C9H8N]+and complex anion, [Cr(H2O)2(C2O4)2]- (Bélombé et al., 2009). We report here the crystal structure of a homologous salt, with 4-Dimethylaminopyridinium as the organic cation. The Fig. 1 shows the 4-dimethylaminopyridinium cation, [C7H11N2]+, and the complex anion, [Cr(H2O)2(C2O4)2]-.The asymmetric unit is formed by one-half cation and one-half anion. The geometrical parameters of the [C7H11N2]+ cation are in agreement with those found in salts with the same cationic entity (Ghouili et al., 2010). The CrIII ion of the complex anion adopts a distorted (4 + 2) octahedral coordination involving four equatorial O atoms (O2, O2i, O3, O3i) of two nearly coplanar oxalate and two quasi axial O atoms (O1, O1i) of water ligands (Fig. 1). The equatorial Cr–O distances are 1.9706 (13) Å (Cr–O(2), Cr–O(2i)) and 1.9468 (13) Å (Cr–O(3), Cr–O(3i)) respectively, and are significantly shorter than the axial Cr–O distance of 2.0055 (14)Å (Cr–O(1), Cr–O(1i)). The bond distances in the complex anion are comparable with those reported for the quinolinium compound (Bélombé et al., 2009).In the crystal structure, intermolecular N–H···O(carbonyl) hydrogen bonds connect the ionic entities, generating layers parallel to [010]. These layers are further connected by lateral O–H···O hydrogen bonds,stabilizing the structure (Table 1, Fig. 2)

Related literature top

For general background to the coordination chemistry of oxalate, see: Martin et al. (2007). For related structures, see: Bélombé et al. (2009); Ghouili et al. (2010).

Experimental top

A mixture of 4-dimethylaminopyridine (1 mmol, 122.2 mg) and oxalic acid (2.2 mmol, 277.2 mg) was dissolved in 30 ml of water. The filtered solution was stirred at 328 K and an aqueous solution (20 ml) of CrCl3.6H2O (1 mmol, 266.5 mg) was added in successive small portions and stirred for 2 h continuously. The final red-violet solution obtained was left at room temperature and brown plate-like 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 0.96 and 0.86 Å respectively, and constrained to ride on their parent atoms, with Uiso(H) = 1.5Ueq(C) and 1.2Ueq(N). The water H atoms were first located in a difference Fourier map and refined with distance restraints of d(O–H1) = 0.81 (1) with all Uiso(H) refined freely.

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. A view of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Unlabelled atoms are related two labeled atoms by the symmetry code for cation and anion are: 1-x,y,1/2-z; -x,y,1/2-z
[Figure 2] Fig. 2. Packing diagram of the title compound. Dotted lines show hydrogen bonding.
4-(Dimethylamino)pyridinium trans-diaquabis[oxalato(2-)-κ2O1,O2]chromate(III) top
Crystal data top
(C7H11N2)[Cr(C2O4)2(H2O)2]F(000) = 796
Mr = 387.25Dx = 1.731 Mg m−3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 1857 reflections
a = 11.524 (4) Åθ = 2.0–28.3°
b = 20.372 (8) ŵ = 0.83 mm−1
c = 7.355 (2) ÅT = 293 K
β = 120.626 (6)°Prism, dark-violet
V = 1485.9 (9) Å30.20 × 0.20 × 0.10 mm
Z = 4
Data collection top
Bruker APEX CCD area-detector
diffractometer		1857 independent reflections
Radiation source: fine-focus sealed tube1739 reflections with I > 2σ(I)
graphiteRint = 0.046
integration method scansθmax = 28.3°, θmin = 2.0°
Absorption correction: multi-scan
(SADABS; Bruker, 2004)		h = −15→15
Tmin = 0.895, Tmax = 0.910k = −27→27
10203 measured reflectionsl = −9→9
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)] = 0.033H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.089 w = 1/[σ2(Fo2) + (0.0395P)2 + 1.1284P]
where P = (Fo2 + 2Fc2)/3
S = 1.16(Δ/σ)max < 0.001
1857 reflectionsΔρmax = 0.37 e Å−3
127 parametersΔρmin = −0.38 e Å−3
2 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0065 (6)
Crystal data top
(C7H11N2)[Cr(C2O4)2(H2O)2]V = 1485.9 (9) Å3
Mr = 387.25Z = 4
Monoclinic, C2/cMo Kα radiation
a = 11.524 (4) ŵ = 0.83 mm−1
b = 20.372 (8) ÅT = 293 K
c = 7.355 (2) Å0.20 × 0.20 × 0.10 mm
β = 120.626 (6)°
Data collection top
Bruker APEX CCD area-detector
diffractometer		1857 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2004)		1739 reflections with I > 2σ(I)
Tmin = 0.895, Tmax = 0.910Rint = 0.046
10203 measured reflectionsθmax = 28.3°
Refinement top
R[F2 > 2σ(F2)] = 0.033H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.089Δρmax = 0.37 e Å−3
S = 1.16Δρmin = −0.38 e Å−3
1857 reflectionsAbsolute structure: ?
127 parametersFlack parameter: ?
2 restraintsRogers parameter: ?
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cr10.00000.148676 (17)0.25000.02141 (14)
O10.10432 (13)0.15066 (6)0.5670 (2)0.0278 (3)
H1A0.1841 (11)0.1603 (11)0.618 (4)0.038 (6)*
H1B0.097 (2)0.1194 (8)0.626 (3)0.039 (6)*
O20.11598 (12)0.22143 (6)0.2606 (2)0.0273 (3)
O30.10971 (12)0.07688 (6)0.2448 (2)0.0275 (3)
O40.12757 (13)0.33040 (6)0.2756 (2)0.0324 (3)
O50.11585 (14)−0.03196 (7)0.2324 (2)0.0394 (4)
C10.06468 (17)0.01913 (8)0.2430 (3)0.0259 (4)
C20.07080 (16)0.27821 (8)0.2608 (3)0.0236 (3)
N110.50000.15711 (11)0.25000.0374 (5)
N120.5000−0.04417 (12)0.25000.0393 (6)
H120.5000−0.08640.25000.096 (17)*
C110.3808 (3)0.19340 (12)0.2074 (5)0.0594 (7)
H11C0.39980.23960.21910.121 (15)*
H11D0.35480.18110.30770.088 (11)*
H11E0.30870.18360.06710.077 (10)*
C120.50000.09124 (12)0.25000.0263 (5)
C130.38704 (18)0.05453 (10)0.2186 (3)0.0341 (4)
H130.30970.07600.19670.049 (7)*
C140.3915 (2)−0.01145 (10)0.2204 (3)0.0394 (5)
H140.3167−0.03490.20050.070 (9)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cr10.0191 (2)0.0153 (2)0.0318 (2)0.0000.01434 (16)0.000
O10.0272 (7)0.0222 (6)0.0332 (7)−0.0025 (5)0.0147 (6)0.0010 (5)
O20.0237 (6)0.0200 (6)0.0417 (7)−0.0003 (4)0.0192 (6)0.0007 (5)
O30.0236 (6)0.0222 (6)0.0400 (7)0.0021 (5)0.0186 (5)−0.0004 (5)
O40.0275 (6)0.0205 (6)0.0477 (8)−0.0031 (5)0.0180 (6)0.0019 (5)
O50.0379 (8)0.0254 (7)0.0459 (8)0.0093 (5)0.0148 (6)−0.0056 (6)
C10.0242 (8)0.0219 (8)0.0252 (8)0.0029 (6)0.0080 (7)−0.0011 (6)
C20.0216 (8)0.0216 (8)0.0258 (8)0.0007 (6)0.0110 (6)0.0014 (6)
N110.0452 (14)0.0244 (11)0.0443 (14)0.0000.0240 (12)0.000
N120.0497 (15)0.0244 (12)0.0397 (13)0.0000.0198 (11)0.000
C110.0716 (18)0.0393 (13)0.0646 (16)0.0220 (12)0.0327 (15)−0.0016 (11)
C120.0265 (12)0.0271 (12)0.0259 (11)0.0000.0138 (10)0.000
C130.0248 (9)0.0395 (10)0.0398 (10)−0.0006 (7)0.0178 (8)−0.0021 (8)
C140.0376 (11)0.0398 (11)0.0399 (11)−0.0139 (8)0.0190 (9)−0.0035 (8)
Geometric parameters (Å, °) top
Cr1—O3i1.9466 (13)N11—C121.342 (3)
Cr1—O31.9466 (13)N11—C11ii1.447 (3)
Cr1—O21.9706 (13)N11—C111.447 (3)
Cr1—O2i1.9706 (13)N12—C14ii1.333 (3)
Cr1—O1i2.0067 (14)N12—C141.333 (3)
Cr1—O12.0067 (14)N12—H120.8600
O1—H1A0.821 (10)C11—H11C0.9600
O1—H1B0.802 (10)C11—H11D0.9600
O2—C21.269 (2)C11—H11E0.9600
O3—C11.283 (2)C12—C131.414 (2)
O4—C21.224 (2)C12—C13ii1.414 (2)
O5—C11.218 (2)C13—C141.345 (3)
C1—C1i1.546 (4)C13—H130.9300
C2—C2i1.557 (3)C14—H140.9300
O3i—Cr1—O382.57 (8)O4—C2—C2i119.61 (10)
O3i—Cr1—O2177.08 (5)O2—C2—C2i114.16 (9)
O3—Cr1—O297.57 (6)C12—N11—C11ii120.73 (15)
O3i—Cr1—O2i97.57 (6)C12—N11—C11120.73 (15)
O3—Cr1—O2i177.08 (5)C11ii—N11—C11118.5 (3)
O2—Cr1—O2i82.45 (7)C14ii—N12—C14120.0 (3)
O3i—Cr1—O1i91.57 (5)C14ii—N12—H12120.0
O3—Cr1—O1i90.16 (5)C14—N12—H12120.0
O2—Cr1—O1i91.35 (5)N11—C11—H11C109.5
O2i—Cr1—O1i86.91 (5)N11—C11—H11D109.5
O3i—Cr1—O190.16 (5)H11C—C11—H11D109.5
O3—Cr1—O191.57 (5)N11—C11—H11E109.5
O2—Cr1—O186.91 (5)H11C—C11—H11E109.5
O2i—Cr1—O191.35 (5)H11D—C11—H11E109.5
O1i—Cr1—O1177.70 (7)N11—C12—C13121.92 (12)
Cr1—O1—H1A114.1 (17)N11—C12—C13ii121.92 (12)
Cr1—O1—H1B116.7 (17)C13—C12—C13ii116.2 (2)
H1A—O1—H1B110 (2)C14—C13—C12119.97 (19)
C2—O2—Cr1114.53 (11)C14—C13—H13120.0
C1—O3—Cr1115.20 (11)C12—C13—H13120.0
O5—C1—O3125.28 (17)N12—C14—C13121.95 (19)
O5—C1—C1i121.26 (11)N12—C14—H14119.0
O3—C1—C1i113.46 (9)C13—C14—H14119.0
O4—C2—O2126.23 (15)
O3i—Cr1—O2—C2−89.0 (10)Cr1—O3—C1—C1i−3.0 (2)
O3—Cr1—O2—C2178.46 (12)Cr1—O2—C2—O4176.72 (14)
O2i—Cr1—O2—C21.40 (9)Cr1—O2—C2—C2i−3.4 (2)
O1i—Cr1—O2—C288.11 (12)C11ii—N11—C12—C13177.00 (16)
O1—Cr1—O2—C2−90.37 (12)C11—N11—C12—C13−3.00 (16)
O3i—Cr1—O3—C11.22 (9)C11ii—N11—C12—C13ii−3.00 (16)
O2—Cr1—O3—C1178.27 (12)C11—N11—C12—C13ii177.00 (16)
O2i—Cr1—O3—C1−91.7 (10)N11—C12—C13—C14−179.79 (14)
O1i—Cr1—O3—C1−90.34 (12)C13ii—C12—C13—C140.21 (14)
O1—Cr1—O3—C191.18 (12)C14ii—N12—C14—C130.22 (15)
Cr1—O3—C1—O5177.34 (15)C12—C13—C14—N12−0.4 (3)
Symmetry codes: (i) −x, y, −z+1/2; (ii) −x+1, y, −z+1/2.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···O4iii0.82 (1)1.91 (1)2.719 (2)171 (2)
O1—H1B···O5iv0.80 (1)1.91 (1)2.680 (2)160 (2)
N12—H12···O4v0.862.192.906 (3)141
N12—H12···O4vi0.862.192.906 (3)141
Symmetry codes: (iii) −x+1/2, −y+1/2, −z+1; (iv) x, −y, z+1/2; (v) −x+1/2, y−1/2, −z+1/2; (vi) x+1/2, y−1/2, z.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···O4i0.82 (1)1.91 (1)2.719 (2)171 (2)
O1—H1B···O5ii0.80 (1)1.91 (1)2.680 (2)160 (2)
N12—H12···O4iii0.862.192.906 (3)141
N12—H12···O4iv0.862.192.906 (3)141
Symmetry codes: (i) −x+1/2, −y+1/2, −z+1; (ii) x, −y, z+1/2; (iii) −x+1/2, y−1/2, −z+1/2; (iv) x+1/2, y−1/2, z.
Acknowledgements top

The authors thank Pr. Barthelemy Nyasse (Organic Chemistry Department, University of Yaounde I) for the donation of 4-dimethylaminopyridine and Klaus Kruse (RWTH Aachen) for his technical support during the X-ray experiments.

references
References top

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