4,4′-Bipyridyl­ium di-μ-chloro­tetra­chloro­dicuprate(II): a redetermination

The structure of the title compound, (C₁₀H₁₀N₂)[Cu₂Cl₆], previously determined by Bukowska-Strzyzewska & Tosik [Pol. J. Chem. (1979), 53, 2423–2428], has been reinvestigated. Our structure determination is of a significantly higher precision and, in contrast to the previous investigation, H atoms could be clearly found. Thus, it can be shown that the chains of alternating bipyridyl­ium cations and Cu₂Cl₆²⁻ anions are stabilized by bifurcated hydrogen bonds. The cation and anion both lie on inversion centres.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.028
• wR factor = 0.068
• Data-to-parameter ratio = 24.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

---

S1. Comment

The structure determination of the title compound, (I), was undertaken within a project on the preparation and structural investigation of new coordination polymers based on copper(I) halides and aromatic bases. Our results are of a significantly higher precision than the previously determined structure (Bukowska-Strzyzewska & Tosik, 1979) and we have been able to locate all H atoms.

The title compound crystallizes in parallel sheets which are composed of rows of alternating bipyridyl cations and Cu₂Cl₆^2- anions. These rows run approximately along the [145] vector and are stabilized by bifurcated N—H···Cl hydrogen bonds (Fig. 1). The cation and anion are located on crystallographic centres of inversion and, as a consequence of that, the pyridyl rings are coplanar. Bond lengths and angles are in the usual ranges compared with structures retrieved from the Cambridge Structural Database (Version 5.20 of October 2000; Allen & Kennard, 1993). The bonds between the terminal Cl atoms and the Cu atoms are significantly shorter than the bridging Cu—Cl bonds.

S2. Experimental

The title compound was prepared by the reaction of Cu₂I₂–4,4'-bipyridine [freshly prepared by the reaction of 4,4'-bipyridine and copper(I) iodide] with an excess of diluted hydrochloric acid. After one day standing at room temperature, light orange needles had formed in 60% yield. The homogeneity was checked by X-ray powder diffraction.

S3. Refinement

All H atoms were located by difference Fourier synthesis and refined with fixed individual displacement parameters [U(H) = 1.2U_eq(C) or U(H) = 1.2U_eq(N)] using a riding model with aromatic C—H = 0.93 Å or N—H = 0.86 Å.

Computing details

Data collection: DIF4 (Stoe & Cie, 1992); cell refinement: DIF4; data reduction: REDU4 (Stoe & Cie, 1992); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Siemens, 1991); software used to prepare material for publication: CIFTAB in SHELXL97.

Figures

Fig. 1. A perspective view of the title compound with the atom-numbering scheme. Atoms labelled A are centrosymmetrically related to the others. Displacement ellipsoids are at the 50% probability level.

(I)

Crystal data

(C10H10N2)[Cu2Cl6]	Z = 1
Mr = 497.98	F(000) = 244
Triclinic, P1	Dx = 2.190 Mg m^−3
a = 3.9158 (8) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.021 (2) Å	Cell parameters from 70 reflections
c = 10.698 (2) Å	θ = 11–19°
α = 113.92 (3)°	µ = 3.86 mm^−1
β = 95.16 (3)°	T = 293 K
γ = 96.06 (3)°	Needle, light orange
V = 377.51 (13) Å^3	0.15 × 0.07 × 0.07 mm

Data collection

Phillips PW-1100 four-circle diffractometer	1716 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.018
Graphite monochromator	θmax = 30.0°, θmin = 3.7°
ω/θ scans	h = 0→5
Absorption correction: numerical X-SHAPE (Stoe & Cie, 1998)	k = −14→14
Tmin = 0.549, Tmax = 0.599	l = −14→14
2500 measured reflections	4 standard reflections every 120 min
2205 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.028	H-atom parameters constrained
wR(F^2) = 0.068	w = 1/[σ^2(Fo^2) + (0.023P)^2 + 0.415P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max = 0.001
2205 reflections	Δρmax = 0.53 e Å^−3
92 parameters	Δρmin = −0.46 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0084 (12)

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	0.33110 (8)	0.90348 (3)	0.08873 (3)	0.02544 (10)
Cl1	0.25990 (16)	0.89121 (6)	−0.13317 (6)	0.02760 (14)
Cl2	−0.10035 (18)	0.71109 (7)	0.02790 (6)	0.03439 (16)
Cl3	0.40337 (16)	0.94513 (7)	0.31191 (6)	0.02755 (13)
N1	0.8566 (6)	0.6889 (2)	0.3197 (2)	0.0296 (5)
H1N	0.9459	0.7353	0.2752	0.036*
C1	0.5769 (6)	0.5406 (2)	0.4613 (2)	0.0210 (4)
C2	0.7537 (7)	0.6839 (3)	0.5304 (3)	0.0307 (5)
H2	0.7767	0.7311	0.6263	0.037*
C3	0.8957 (7)	0.7566 (3)	0.4573 (3)	0.0317 (6)
H3	1.0176	0.8521	0.5037	0.038*
C4	0.6850 (8)	0.5523 (3)	0.2483 (3)	0.0352 (6)
H4	0.6619	0.5090	0.1523	0.042*
C5	0.5414 (8)	0.4751 (3)	0.3175 (3)	0.0313 (6)
H5	0.4213	0.3797	0.2682	0.038*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.02994 (17)	0.02633 (16)	0.01819 (15)	−0.00603 (11)	0.00114 (11)	0.01042 (12)
Cl1	0.0324 (3)	0.0278 (3)	0.0196 (3)	−0.0069 (2)	−0.0009 (2)	0.0107 (2)
Cl2	0.0403 (4)	0.0325 (3)	0.0249 (3)	−0.0130 (3)	0.0015 (2)	0.0117 (2)
Cl3	0.0310 (3)	0.0318 (3)	0.0196 (3)	−0.0013 (2)	0.0025 (2)	0.0123 (2)
N1	0.0340 (12)	0.0306 (11)	0.0311 (11)	0.0032 (9)	0.0093 (9)	0.0193 (9)
C1	0.0215 (11)	0.0215 (10)	0.0206 (10)	0.0024 (8)	0.0026 (8)	0.0097 (9)
C2	0.0408 (15)	0.0237 (11)	0.0216 (11)	−0.0059 (10)	0.0010 (10)	0.0068 (9)
C3	0.0359 (14)	0.0249 (11)	0.0316 (13)	−0.0036 (10)	0.0040 (11)	0.0114 (10)
C4	0.0478 (17)	0.0338 (13)	0.0219 (12)	−0.0008 (12)	0.0080 (11)	0.0107 (10)
C5	0.0429 (15)	0.0250 (11)	0.0227 (12)	−0.0026 (11)	0.0065 (11)	0.0080 (10)

Geometric parameters (Å, º)

Cu1—Cl3	2.2361 (8)	C1—C5	1.393 (3)
Cu1—Cl2	2.2566 (11)	C1—C1^ii	1.498 (4)
Cu1—Cl1	2.3163 (8)	C2—C3	1.381 (3)
Cu1—Cl1^i	2.3234 (11)	C2—H2	0.930
Cl1—Cu1^i	2.3234 (11)	C3—H3	0.930
N1—C4	1.332 (3)	C4—C5	1.381 (4)
N1—C3	1.334 (3)	C4—H4	0.930
N1—H1N	0.860	C5—H5	0.930
C1—C2	1.388 (3)
Cl3—Cu1—Cl2	93.96 (4)	C3—C2—C1	120.2 (2)
Cl3—Cu1—Cl1	173.01 (3)	C3—C2—H2	119.9
Cl2—Cu1—Cl1	91.00 (4)	C1—C2—H2	119.9
Cl3—Cu1—Cl1^i	91.25 (4)	N1—C3—C2	119.5 (2)
Cl2—Cu1—Cl1^i	173.43 (3)	N1—C3—H3	120.3
Cl1—Cu1—Cl1^i	83.48 (4)	C2—C3—H3	120.3
Cu1—Cl1—Cu1^i	96.52 (4)	N1—C4—C5	119.7 (2)
C4—N1—C3	122.6 (2)	N1—C4—H4	120.1
C4—N1—H1N	118.7	C5—C4—H4	120.1
C3—N1—H1N	118.7	C4—C5—C1	119.8 (2)
C2—C1—C5	118.1 (2)	C4—C5—H5	120.1
C2—C1—C1^ii	121.0 (3)	C1—C5—H5	120.1
C5—C1—C1^ii	120.9 (3)
Cl2—Cu1—Cl1—Cu1^i	176.44 (3)	C3—N1—C4—C5	−0.4 (4)
C5—C1—C2—C3	−1.5 (4)	N1—C4—C5—C1	0.0 (4)
C1^ii—C1—C2—C3	179.6 (3)	C2—C1—C5—C4	0.9 (4)
C4—N1—C3—C2	−0.1 (4)	C1^ii—C1—C5—C4	179.9 (3)
C1—C2—C3—N1	1.1 (4)

Symmetry codes: (i) −x+1, −y+2, −z; (ii) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···Cl2^iii	0.86	2.54	3.236 (2)	138
N1—H1N···Cl3^iii	0.86	2.49	3.198 (2)	140

Symmetry code: (iii) x+1, y, z.