4,4′-Bipyridinium bis­(oxalato-κ² O ¹,O ²)cuprate(II): an ion-pair complex

Abstract

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 Cu^II 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.

Related literature

For related background, see: Ren et al. (2007 ▶). For related structures, see, for example: Bukowska-Strzyzewska & Tosik (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

Crystal data

• (C₁₀H₁₀N₂)[Cu(C₂O₄)₂]

• M _r = 397.79

• Triclinic,

• a = 3.6900 (7) Å

• b = 9.950 (2) Å

• c = 10.230 (2) Å

• α = 113.77 (3)°

• β = 98.43 (3)°

• γ = 97.89 (3)°

• V = 331.93 (15) ų

• Z = 1

• Mo Kα radiation

• μ = 1.70 mm⁻¹

• T = 293 K

• 0.41 × 0.27 × 0.22 mm

Data collection

• Bruker APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.527, T _max = 0.705

• 1761 measured reflections

• 1168 independent reflections

• 1126 reflections with I > 2σ(I)

• R _int = 0.013

Refinement

• R[F ² > 2σ(F ²)] = 0.027

• wR(F ²) = 0.073

• S = 1.09

• 1168 reflections

• 115 parameters

• H-atom parameters constrained

• Δρ_max = 0.30 e Å⁻³

• Δρ_min = −0.29 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT-Plus (Bruker, 2005 ▶); data reduction: SAINT-Plus; 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.

Supplementary Material

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
N1—H1A⋯O4i	0.86	2.02	2.755 (3)	143
N1—H1A⋯O1i	0.86	2.21	2.880 (3)	135
C1—H1⋯O4ii	0.93	2.49	3.381 (3)	160
C2—H2⋯O3ii	0.93	2.57	3.195 (3)	125
C4—H4⋯O2	0.93	2.42	3.272 (3)	153
C5—H5⋯O1	0.93	2.46	3.215 (3)	138

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

Comment

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 = oxalate^2-) resulting from the decomposition of furan-2-carboxylic acid to give the ox^2- 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 ox^2- 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 ox^2- 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–O_oxalate 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).

Experimental

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

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 U_iso(H) = 1.2U_eq (C, N).

Figures

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.

Fig. 2.

The two-dimensional hydrogen-bonded sheet structure of (I) showing intra- and intermolecular hydrogen bonds as dashed lines.

Crystal data

(C10H10N2)[Cu(C2O4)2]	Z = 1
Mr = 397.79	F(000) = 201
Triclinic, P1	Dx = 1.990 Mg m−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 3.6900 (7) Å	Cell parameters from 1168 reflections
b = 9.950 (2) Å	θ = 2.2–25.1°
c = 10.230 (2) Å	µ = 1.70 mm−1
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

Bruker APEXII CCD area-detector diffractometer	1168 independent reflections
Radiation source: fine-focus sealed tube	1126 reflections with I > 2σ(I)
graphite	Rint = 0.013
φ and ω scans	θmax = 25.1°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −4→4
Tmin = 0.527, Tmax = 0.705	k = −9→11
1761 measured reflections	l = −11→12

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.073	H-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 parameters	Δρmax = 0.30 e Å−3
0 restraints	Δρmin = −0.29 e Å−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.0000	0.0000	0.5000	0.02273 (16)
C1	0.9693 (6)	0.2924 (3)	0.0264 (3)	0.0263 (5)
H1	1.0658	0.3392	−0.0273	0.032*
C2	0.7599 (6)	0.1481 (3)	−0.0443 (3)	0.0228 (5)
H2	0.7140	0.0971	−0.1459	0.027*
C3	0.6154 (6)	0.0779 (2)	0.0367 (2)	0.0182 (4)
C4	0.6955 (7)	0.1599 (3)	0.1887 (3)	0.0265 (5)
H4	0.6054	0.1165	0.2461	0.032*
C5	0.9057 (7)	0.3037 (3)	0.2534 (3)	0.0312 (6)
H5	0.9580	0.3582	0.3547	0.037*
C6	0.4733 (6)	0.2586 (3)	0.5616 (3)	0.0232 (5)
C7	0.3414 (6)	0.2770 (3)	0.7045 (2)	0.0224 (5)
N1	1.0353 (5)	0.3657 (2)	0.1713 (2)	0.0273 (4)
H1A	1.1664	0.4564	0.2135	0.033*
O1	0.6801 (5)	0.3636 (2)	0.5609 (2)	0.0342 (4)
O2	0.3514 (5)	0.12699 (19)	0.45407 (17)	0.0286 (4)
O3	0.1187 (5)	0.16185 (19)	0.69418 (18)	0.0265 (4)
O4	0.4569 (5)	0.39568 (19)	0.81441 (18)	0.0313 (4)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cu1	0.0285 (2)	0.0171 (2)	0.0166 (2)	−0.00496 (16)	0.00626 (16)	0.00411 (17)
C1	0.0250 (12)	0.0251 (12)	0.0318 (13)	0.0015 (10)	0.0060 (10)	0.0167 (11)
C2	0.0249 (11)	0.0219 (12)	0.0211 (11)	0.0009 (9)	0.0046 (9)	0.0102 (10)
C3	0.0155 (10)	0.0184 (11)	0.0216 (11)	0.0041 (9)	0.0043 (8)	0.0095 (9)
C4	0.0319 (13)	0.0245 (12)	0.0218 (12)	−0.0003 (10)	0.0082 (10)	0.0101 (10)
C5	0.0360 (14)	0.0262 (13)	0.0237 (13)	−0.0002 (11)	0.0047 (10)	0.0059 (11)
C6	0.0244 (11)	0.0224 (12)	0.0214 (12)	0.0018 (9)	0.0051 (9)	0.0092 (10)
C7	0.0235 (11)	0.0221 (12)	0.0208 (12)	0.0022 (9)	0.0046 (9)	0.0096 (10)
N1	0.0242 (10)	0.0160 (10)	0.0371 (12)	−0.0022 (8)	0.0040 (9)	0.0099 (9)
O1	0.0425 (10)	0.0237 (9)	0.0309 (10)	−0.0083 (8)	0.0111 (8)	0.0101 (8)
O2	0.0381 (9)	0.0205 (8)	0.0196 (8)	−0.0057 (7)	0.0102 (7)	0.0037 (7)
O3	0.0332 (9)	0.0208 (8)	0.0198 (8)	−0.0059 (7)	0.0079 (7)	0.0062 (7)
O4	0.0389 (10)	0.0203 (9)	0.0227 (9)	−0.0070 (7)	0.0063 (7)	0.0018 (7)

Geometric parameters (Å, °)

Cu1—O3	1.9245 (19)	C4—C5	1.367 (4)
Cu1—O3i	1.9245 (19)	C4—H4	0.9300
Cu1—O2i	1.9252 (17)	C5—N1	1.331 (3)
Cu1—O2	1.9252 (17)	C5—H5	0.9300
C1—N1	1.327 (3)	C6—O1	1.210 (3)
C1—C2	1.369 (3)	C6—O2	1.288 (3)
C1—H1	0.9300	C6—C7	1.557 (3)
C2—C3	1.397 (3)	C7—O4	1.221 (3)
C2—H2	0.9300	C7—O3	1.272 (3)
C3—C4	1.395 (3)	N1—H1A	0.8600
C3—C3ii	1.485 (4)
O3—Cu1—O3i	180.0	C5—C4—H4	119.9
O3—Cu1—O2i	93.91 (7)	C3—C4—H4	119.9
O3i—Cu1—O2i	86.09 (7)	N1—C5—C4	119.9 (2)
O3—Cu1—O2	86.09 (7)	N1—C5—H5	120.1
O3i—Cu1—O2	93.91 (7)	C4—C5—H5	120.1
O2i—Cu1—O2	180.00 (8)	O1—C6—O2	126.2 (2)
N1—C1—C2	120.4 (2)	O1—C6—C7	119.2 (2)
N1—C1—H1	119.8	O2—C6—C7	114.60 (19)
C2—C1—H1	119.8	O4—C7—O3	125.9 (2)
C1—C2—C3	119.7 (2)	O4—C7—C6	119.3 (2)
C1—C2—H2	120.1	O3—C7—C6	114.8 (2)
C3—C2—H2	120.1	C1—N1—C5	122.3 (2)
C4—C3—C2	117.5 (2)	C1—N1—H1A	118.9
C4—C3—C3ii	121.4 (2)	C5—N1—H1A	118.9
C2—C3—C3ii	121.1 (3)	C6—O2—Cu1	111.74 (14)
C5—C4—C3	120.3 (2)	C7—O3—Cu1	112.38 (14)

Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1, −y, −z.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O4iii	0.86	2.02	2.755 (3)	143
N1—H1A···O1iii	0.86	2.21	2.880 (3)	135
C1—H1···O4iv	0.93	2.49	3.381 (3)	160
C2—H2···O3iv	0.93	2.57	3.195 (3)	125
C4—H4···O2	0.93	2.42	3.272 (3)	153
C5—H5···O1	0.93	2.46	3.215 (3)	138

Symmetry codes: (iii) −x+2, −y+1, −z+1; (iv) x+1, y, z−1.