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The title compound, (C10H10N2)[Cu(C2O4)2] or (4,4′-H2bpy)[Cu(ox)2] (bpy is 4,4′-bipyridine and ox is oxalate), is an ion-pair complex comprising a protonated 4,4′-bipyridinium dication and a square-planar dioxalatocopper(II) dianion. In the centrosymmetric dianion, the CuII centre is coordinated by four O atoms from the two dicrete oxalate ligands [Cu—O = 1.9245 (19) and 1.9252 (17) Å], while the planar dications are also centrosymmetric. Inter-species N—H...O hydrogen bonds link the cations and anions into one-dimensional chains and, together with weak intra-ion C—H...O inter­actions, give a two-dimensional sheet structure.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536809039117/zs2010sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536809039117/zs2010Isup2.hkl
Contains datablock I

CCDC reference: 754050

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.004 Å
  • R factor = 0.027
  • wR factor = 0.073
  • Data-to-parameter ratio = 10.2

checkCIF/PLATON results

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Alert level C PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor .... 2.50 PLAT042_ALERT_1_C Calc. and Reported MoietyFormula Strings Differ ?
Alert level G PLAT154_ALERT_1_G The su's on the Cell Angles are Equal (x 10000) 3000 Deg. PLAT180_ALERT_4_G Check Cell Rounding: # of Values Ending with 0 = 3 PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature 293 K PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature 293 K
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 2 ALERT level C = Check and explain 4 ALERT level G = General alerts; check 4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 1 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check

Comment top

Currently, in situ chemical reactions are of considerable interest, providing a powerful route for the preparation of novel crystals with unexpected structures, e.g. Ren et al. (2007) has reported the hydrothermal synthesis of a new coordination polymer [Cu(ox)(4,4'-bpy)]n (bpy = 4,4'-bipyridine; ox = oxalate2-) resulting from the decomposition of furan-2-carboxylic acid to give the ox2- ligand in the reaction of this acid with Cu(NO3)2.3H2O and 4,4'-bpy. In the work reported here, a novel ion-pair complex, (4,4'-H2bpy)[Cu(ox)2] (I) was obtained by using sodium 2-hydroxyphosphonocarboxylate as the ox2- source and CuCl2 . 2H2O as the copper source. Copper(II) is a relatively strong oxidant with the ability to oxidise the sodium 2-hydroxyphosphonocarboxylic giving ox2- which is generated in situ, resulting in formation of the title compound, the structure of which is reported here.

The structure of the (I) shows an ion-pair complex comprising a protonated 4,4'-bipyridine dication, (4,4'-H2bpy)2+ (Bukowska-Strzyzewska et al., 1979; Crawford et al., 2004; Dou et al., 2007; Madhu et al., 2004; Näther et al., 2001; Tosik et al., 1990; Willett et al., 2006), and a [Cu(C2O4)2]2- anion (Fig. 1). The discrete bis-(oxalato)copper(II) dianions have square planar CuO4 stereochemistry, comprising four O donor atoms from two oxalate ligands [Cu–O, 1.9245 (19), 1.9252 (17) Å] and lie across inversion centres in the unit cell. In the axial sites, the Cu–Ooxalate contacts are 2.920 (2) Å. With the 4,4'-bipyridine dications, the pyridine rings are coplanar and also have crystallographic inversion symmetry. Interamolecular N—H···O hydrogen bonds (Table 1) link the cations and anions into one-dimensional chains and together with weak intramolecular C–H···O interactions give two-dimensional sheet structures which layer down the a direction in the unit cell (Fig. 2).

Related literature top

For related background, see: Ren et al. (2007). For related structures, see, for example: Bukowska-Strzyzewska et al. (1979); Crawford et al. (2004); Diallo et al. (2008); Dou et al. (2007); Madhu & Das (2004); Näther et al. (2001); Tosik et al. (1990); Willett et al. (2006).

Experimental top

Sodium 2-hydroxyphosphonocarboxylate (1 mmol) was dissolved in 10 ml of 50% ethanol-water after which 1 mmol of copper(II) chloride dihydrate and 1 mmol of 4,4'-bipyridine were added in sequence. After stirring for 10 min, the resulting mixture was transferred into a Teflon-lined stainless steel vessel (15 ml) which was sealed and heated at 110 °C for four days, then allowed to cool to room temperature. The blue-green single crystal blocks of the title compound (I), together with yellow-red prismatic crystals of a second unidentified component were obtained. The yield of (I) was ca. 25% (based on copper). IR (cm-1, KBr): 3439, 3110, 3060, 2921, 1665, 1581, 1487, 1409, 1273, 1205 1106, 1000, 892, 827, 798.

Refinement top

All H atoms were geometrically placed and refined using a riding model approximation, with C—H = 0.93 Å or N—H = 0.86 Å and Uiso(H) = 1.2Ueq (C, N).

Structure description top

Currently, in situ chemical reactions are of considerable interest, providing a powerful route for the preparation of novel crystals with unexpected structures, e.g. Ren et al. (2007) has reported the hydrothermal synthesis of a new coordination polymer [Cu(ox)(4,4'-bpy)]n (bpy = 4,4'-bipyridine; ox = oxalate2-) resulting from the decomposition of furan-2-carboxylic acid to give the ox2- ligand in the reaction of this acid with Cu(NO3)2.3H2O and 4,4'-bpy. In the work reported here, a novel ion-pair complex, (4,4'-H2bpy)[Cu(ox)2] (I) was obtained by using sodium 2-hydroxyphosphonocarboxylate as the ox2- source and CuCl2 . 2H2O as the copper source. Copper(II) is a relatively strong oxidant with the ability to oxidise the sodium 2-hydroxyphosphonocarboxylic giving ox2- which is generated in situ, resulting in formation of the title compound, the structure of which is reported here.

The structure of the (I) shows an ion-pair complex comprising a protonated 4,4'-bipyridine dication, (4,4'-H2bpy)2+ (Bukowska-Strzyzewska et al., 1979; Crawford et al., 2004; Dou et al., 2007; Madhu et al., 2004; Näther et al., 2001; Tosik et al., 1990; Willett et al., 2006), and a [Cu(C2O4)2]2- anion (Fig. 1). The discrete bis-(oxalato)copper(II) dianions have square planar CuO4 stereochemistry, comprising four O donor atoms from two oxalate ligands [Cu–O, 1.9245 (19), 1.9252 (17) Å] and lie across inversion centres in the unit cell. In the axial sites, the Cu–Ooxalate contacts are 2.920 (2) Å. With the 4,4'-bipyridine dications, the pyridine rings are coplanar and also have crystallographic inversion symmetry. Interamolecular N—H···O hydrogen bonds (Table 1) link the cations and anions into one-dimensional chains and together with weak intramolecular C–H···O interactions give two-dimensional sheet structures which layer down the a direction in the unit cell (Fig. 2).

For related background, see: Ren et al. (2007). For related structures, see, for example: Bukowska-Strzyzewska et al. (1979); Crawford et al. (2004); Diallo et al. (2008); Dou et al. (2007); Madhu & Das (2004); Näther et al. (2001); Tosik et al. (1990); Willett et al. (2006).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Molecular configuration and atom numbering scheme for the discrete dication and dianion species in (I). Displacement ellipsoids are drawn at the 50% probability level. Both cation and anion have crystallographic inversion symmetry. Symmetry codes: (A) -x + 1, -y, -z; (B) -x, -y, -z + 1.
[Figure 2] Fig. 2. The two-dimensional hydrogen-bonded sheet structure of (I) showing intra- and intermolecular hydrogen bonds as dashed lines.
4,4'-Bipyridinium bis(oxalato-κ2O1,O2)cuprate(II) top
Crystal data top
(C10H10N2)[Cu(C2O4)2]Z = 1
Mr = 397.79F(000) = 201
Triclinic, P1Dx = 1.990 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 3.6900 (7) ÅCell parameters from 1168 reflections
b = 9.950 (2) Åθ = 2.2–25.1°
c = 10.230 (2) ŵ = 1.70 mm1
α = 113.77 (3)°T = 293 K
β = 98.43 (3)°Block, green-blue
γ = 97.89 (3)°0.41 × 0.27 × 0.22 mm
V = 331.93 (15) Å3
Data collection top
Bruker APEXII CCD area-detector
diffractometer
1168 independent reflections
Radiation source: fine-focus sealed tube1126 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.013
φ and ω scansθmax = 25.1°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
h = 44
Tmin = 0.527, Tmax = 0.705k = 911
1761 measured reflectionsl = 1112
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)] = 0.027Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.073H-atom parameters constrained
S = 1.09 w = 1/[σ2(Fo2) + (0.0434P)2 + 0.1814P]
where P = (Fo2 + 2Fc2)/3
1168 reflections(Δ/σ)max < 0.001
115 parametersΔρmax = 0.30 e Å3
0 restraintsΔρmin = 0.29 e Å3
Crystal data top
(C10H10N2)[Cu(C2O4)2]γ = 97.89 (3)°
Mr = 397.79V = 331.93 (15) Å3
Triclinic, P1Z = 1
a = 3.6900 (7) ÅMo Kα radiation
b = 9.950 (2) ŵ = 1.70 mm1
c = 10.230 (2) ÅT = 293 K
α = 113.77 (3)°0.41 × 0.27 × 0.22 mm
β = 98.43 (3)°
Data collection top
Bruker APEXII CCD area-detector
diffractometer
1168 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
1126 reflections with I > 2σ(I)
Tmin = 0.527, Tmax = 0.705Rint = 0.013
1761 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0270 restraints
wR(F2) = 0.073H-atom parameters constrained
S = 1.09Δρmax = 0.30 e Å3
1168 reflectionsΔρmin = 0.29 e Å3
115 parameters
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
Cu10.00000.00000.50000.02273 (16)
C10.9693 (6)0.2924 (3)0.0264 (3)0.0263 (5)
H11.06580.33920.02730.032*
C20.7599 (6)0.1481 (3)0.0443 (3)0.0228 (5)
H20.71400.09710.14590.027*
C30.6154 (6)0.0779 (2)0.0367 (2)0.0182 (4)
C40.6955 (7)0.1599 (3)0.1887 (3)0.0265 (5)
H40.60540.11650.24610.032*
C50.9057 (7)0.3037 (3)0.2534 (3)0.0312 (6)
H50.95800.35820.35470.037*
C60.4733 (6)0.2586 (3)0.5616 (3)0.0232 (5)
C70.3414 (6)0.2770 (3)0.7045 (2)0.0224 (5)
N11.0353 (5)0.3657 (2)0.1713 (2)0.0273 (4)
H1A1.16640.45640.21350.033*
O10.6801 (5)0.3636 (2)0.5609 (2)0.0342 (4)
O20.3514 (5)0.12699 (19)0.45407 (17)0.0286 (4)
O30.1187 (5)0.16185 (19)0.69418 (18)0.0265 (4)
O40.4569 (5)0.39568 (19)0.81441 (18)0.0313 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0285 (2)0.0171 (2)0.0166 (2)0.00496 (16)0.00626 (16)0.00411 (17)
C10.0250 (12)0.0251 (12)0.0318 (13)0.0015 (10)0.0060 (10)0.0167 (11)
C20.0249 (11)0.0219 (12)0.0211 (11)0.0009 (9)0.0046 (9)0.0102 (10)
C30.0155 (10)0.0184 (11)0.0216 (11)0.0041 (9)0.0043 (8)0.0095 (9)
C40.0319 (13)0.0245 (12)0.0218 (12)0.0003 (10)0.0082 (10)0.0101 (10)
C50.0360 (14)0.0262 (13)0.0237 (13)0.0002 (11)0.0047 (10)0.0059 (11)
C60.0244 (11)0.0224 (12)0.0214 (12)0.0018 (9)0.0051 (9)0.0092 (10)
C70.0235 (11)0.0221 (12)0.0208 (12)0.0022 (9)0.0046 (9)0.0096 (10)
N10.0242 (10)0.0160 (10)0.0371 (12)0.0022 (8)0.0040 (9)0.0099 (9)
O10.0425 (10)0.0237 (9)0.0309 (10)0.0083 (8)0.0111 (8)0.0101 (8)
O20.0381 (9)0.0205 (8)0.0196 (8)0.0057 (7)0.0102 (7)0.0037 (7)
O30.0332 (9)0.0208 (8)0.0198 (8)0.0059 (7)0.0079 (7)0.0062 (7)
O40.0389 (10)0.0203 (9)0.0227 (9)0.0070 (7)0.0063 (7)0.0018 (7)
Geometric parameters (Å, º) top
Cu1—O31.9245 (19)C4—C51.367 (4)
Cu1—O3i1.9245 (19)C4—H40.9300
Cu1—O2i1.9252 (17)C5—N11.331 (3)
Cu1—O21.9252 (17)C5—H50.9300
C1—N11.327 (3)C6—O11.210 (3)
C1—C21.369 (3)C6—O21.288 (3)
C1—H10.9300C6—C71.557 (3)
C2—C31.397 (3)C7—O41.221 (3)
C2—H20.9300C7—O31.272 (3)
C3—C41.395 (3)N1—H1A0.8600
C3—C3ii1.485 (4)
O3—Cu1—O3i180.0C5—C4—H4119.9
O3—Cu1—O2i93.91 (7)C3—C4—H4119.9
O3i—Cu1—O2i86.09 (7)N1—C5—C4119.9 (2)
O3—Cu1—O286.09 (7)N1—C5—H5120.1
O3i—Cu1—O293.91 (7)C4—C5—H5120.1
O2i—Cu1—O2180.00 (8)O1—C6—O2126.2 (2)
N1—C1—C2120.4 (2)O1—C6—C7119.2 (2)
N1—C1—H1119.8O2—C6—C7114.60 (19)
C2—C1—H1119.8O4—C7—O3125.9 (2)
C1—C2—C3119.7 (2)O4—C7—C6119.3 (2)
C1—C2—H2120.1O3—C7—C6114.8 (2)
C3—C2—H2120.1C1—N1—C5122.3 (2)
C4—C3—C2117.5 (2)C1—N1—H1A118.9
C4—C3—C3ii121.4 (2)C5—N1—H1A118.9
C2—C3—C3ii121.1 (3)C6—O2—Cu1111.74 (14)
C5—C4—C3120.3 (2)C7—O3—Cu1112.38 (14)
Symmetry codes: (i) x, y, z+1; (ii) x+1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O4iii0.862.022.755 (3)143
N1—H1A···O1iii0.862.212.880 (3)135
C1—H1···O4iv0.932.493.381 (3)160
C2—H2···O3iv0.932.573.195 (3)125
C4—H4···O20.932.423.272 (3)153
C5—H5···O10.932.463.215 (3)138
Symmetry codes: (iii) x+2, y+1, z+1; (iv) x+1, y, z1.

Experimental details

Crystal data
Chemical formula(C10H10N2)[Cu(C2O4)2]
Mr397.79
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)3.6900 (7), 9.950 (2), 10.230 (2)
α, β, γ (°)113.77 (3), 98.43 (3), 97.89 (3)
V3)331.93 (15)
Z1
Radiation typeMo Kα
µ (mm1)1.70
Crystal size (mm)0.41 × 0.27 × 0.22
Data collection
DiffractometerBruker APEXII CCD area-detector
Absorption correctionMulti-scan
(SADABS; Bruker, 2005)
Tmin, Tmax0.527, 0.705
No. of measured, independent and
observed [I > 2σ(I)] reflections
1761, 1168, 1126
Rint0.013
(sin θ/λ)max1)0.597
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.027, 0.073, 1.09
No. of reflections1168
No. of parameters115
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.30, 0.29

Computer programs: APEX2 (Bruker, 2005), SAINT-Plus (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O4i0.862.022.755 (3)143.1
N1—H1A···O1i0.862.212.880 (3)135.3
C1—H1···O4ii0.932.493.381 (3)159.8
C2—H2···O3ii0.932.573.195 (3)124.6
C4—H4···O20.932.423.272 (3)152.6
C5—H5···O10.932.463.215 (3)138.1
Symmetry codes: (i) x+2, y+1, z+1; (ii) x+1, y, z1.
 

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