Di-μ-chloro-bis­[(2,2-bipyridine)chloro­copper(II)]

The title compound, [Cu₂Cl₄(C₁₀H₈N₂)₂], represents the first example of a simple dimeric coordination complex of Cu^II and 2,2′-bipyridine (bpy). The metal is in a five-coordinate distorted square-pyramidal environment, bonded to a 2,2′- bipyridine mol­ecule, two bridging chlorides and one terminal chloride. There is a centre of symmetry at the mid-point of the Cu...Cu vector.

Key indicators

• Single-crystal X-ray study
• T = 120 K
• Mean [sigma](C-C) = 0.015 Å
• R factor = 0.063
• wR factor = 0.180
• Data-to-parameter ratio = 12.5

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT027_ALERT_3_A _diffrn_reflns_theta_full (too) Low ............      24.68 Deg.

Author Response: The measured crystal was small and therefore diffracted rather weakly. This reduced the upper diffraction limit. \Q range for unit cell determination was 1.00-25.03 \%. For the data collection the final range was 2.5-24.68 deg. The data collection was repeated by using larger crystal, which met the criteria of \Q=25\% (upper \Q limit was 26.50 \%). However, larger crystals were twinned. With the best twinned crystal use of twin model (twin law -1.000 0.000 0.000 0.197 0.982 -0.035 -0.098 -0.991 -0.982, BASF=0.45), led to the same solution than the weak unique data but with poorer R-values and poorer esd's for bond lengths and angles. Therefore, the unique data set was chosen as the final data set.

Alert level C
RINTA01_ALERT_3_C  The value of Rint is greater than 0.10
            Rint given   0.103
THETM01_ALERT_3_C  The value of sine(theta_max)/wavelength is less than 0.590
            Calculated sin(theta_max)/wavelength =    0.5875
PLAT020_ALERT_3_C The value of Rint is greater than 0.10 .........       0.10
PLAT023_ALERT_3_C Resolution (too) Low [sin(th)/Lambda < 0.6].....      24.68 Deg.
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       2.00 Ratio
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT341_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...         15

   1 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   9 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   6 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

Copper compounds display a variety of coordination geometries and coordination numbers that vary from three to six. Jahn–Teller distortion leads to the absence of regular octahedral structures in Cu^II chemistry. Complexes of the general formula Cu(NN)X₂ (X = CI and Br, and NN = a dinitrogen chelate) are known to have different geometries with the coordination number of the copper atom varying from four to six. Particular attention has been devoted to polymeric Cu^II complexes with chlorides and substituted bipyridines as ligands (Garland et al., 1988; Hernandez-Molina et al., 1999; Wang et al., 2004).

The title compound, (I), represents the first example of a binuclear complex of Cu^II chloride and 2,2'-bipyridine and is the most distorted when compared with the other two dimeric complexes containing copper and (a substituted) bipyridine (Gonzalez et al., 1993; Tynan et al., 2005), since the distance of the bridging chloride to a vicinal Cu atom is 2.909?(3) Å. The Cu^II atom is five-coordinate and the geometry about the Cu atom is square pyramidal. The coordination sphere is occupied by two N atoms provided by the chelate 2,2'-bipyridine, as well as two asymmetrically bridging and one terminal chlorides.

Interaction of Cu1—Cl1ⁱⁱ, in order to form a chain structure, is very weak since the distance is 3.130 (3) Å (Wang et al., 2004) [symmetry code: (ii) 1 − x, −y, 1 − z]. Although there are no stacking interactions in the crystal, the structure is stabilized by a series of intra- and inter-chain C—H···Cl contacts (Table 2 and Fig. 2). The H1—Cl2 and H10—Cl1 interactions constitute the intrachain contacts, and the H4—Cl2ⁱⁱⁱ and H7—Cl1ⁱⁱⁱ interactions are very weak inter-chain contacts [symmetry code: (iii) x, 1 + y, z].

S2. Experimental

Compound (I) was produced unexpectedly. A solution of of 2,2'-bipyridine (15.6 mg, 0.1 mmol) in methanol (1 ml) was added to an aqueous solution (9 ml) of CuCl₂ (13.3 mg, 0.1 mmol) containing an equivalent amount of trans-aconitic acid (11.6 mg, 0.066 mmol). A clear green solution was obtained. Green needles of (I) precipitated after slow evaporation of the solution (yield 10 mg, 35%).

S3. Refinement

The H atoms were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.95 Å and U_iso(H) = 1.2U_eq(parent atom).

Computing details

Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Crystal Impact, 2005); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I), showing 40% probability displacement ellipsoids.
	Fig. 2. A representation of intra- and inter-chain C—H···Cl contacts (dashed lines), resulting in the formation of a one-dimensional chain.

Di-µ-chloro-bis[(2,2-bipyridine)chlorocopper(II)]

Crystal data

[Cu2Cl4(C10H8Cl2N2)2]	Z = 1
Mr = 581.24	F(000) = 290
Triclinic, P1	Dx = 1.897 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.1923 (7) Å	Cell parameters from 6682 reflections
b = 8.9872 (8) Å	θ = 2.6–24.7°
c = 9.4241 (9) Å	µ = 2.63 mm^−1
α = 115.136 (6)°	T = 120 K
β = 107.201 (5)°	Needle, green
γ = 95.617 (4)°	0.22 × 0.06 × 0.02 mm
V = 508.91 (8) Å^3

Data collection

Nonius KappaCCD diffractometer	1701 independent reflections
Radiation source: fine-focus sealed tube	1142 reflections with I > 2σ(I)
Horizontally mounted graphite crystal monochromator	Rint = 0.103
Detector resolution: 9 pixels mm^-1	θmax = 24.7°, θmin = 2.6°
ϕ scans and ω scans with κ offsets	h = −8→8
Absorption correction: multi-scan (XPREP in SHELXTL; Sheldrick, 2005)	k = −10→10
Tmin = 0.600, Tmax = 0.944	l = −10→11
6682 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.063	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.180	H-atom parameters constrained
S = 1.17	w = 1/[σ^2(Fo^2) + (0.066P)^2 + 2.6959P] where P = (Fo^2 + 2Fc^2)/3
1701 reflections	(Δ/σ)max < 0.001
136 parameters	Δρmax = 1.09 e Å^−3
0 restraints	Δρmin = −0.84 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	0.76745 (18)	0.07115 (14)	0.50096 (14)	0.0254 (4)
Cl1	0.5435 (4)	−0.1882 (3)	0.3299 (3)	0.0289 (6)
Cl2	0.9535 (4)	−0.0203 (3)	0.6743 (3)	0.0285 (6)
N1	0.9259 (11)	0.3189 (9)	0.6568 (9)	0.0206 (18)
N2	0.6256 (11)	0.1749 (9)	0.3606 (9)	0.0191 (17)
C1	1.0731 (14)	0.3821 (13)	0.8066 (12)	0.029 (2)
H1	1.1265	0.3056	0.8420	0.035*
C2	1.1529 (15)	0.5565 (12)	0.9147 (12)	0.031 (3)
H2	1.2581	0.5984	1.0218	0.037*
C3	1.0750 (15)	0.6662 (12)	0.8617 (12)	0.030 (2)
H3	1.1240	0.7857	0.9334	0.036*
C4	0.9258 (14)	0.6019 (12)	0.7044 (12)	0.026 (2)
H4	0.8741	0.6761	0.6646	0.031*
C5	0.8532 (14)	0.4290 (11)	0.6061 (11)	0.021 (2)
C6	0.6930 (14)	0.3470 (12)	0.4354 (12)	0.023 (2)
C7	0.6122 (15)	0.4373 (13)	0.3544 (12)	0.027 (2)
H7	0.6584	0.5578	0.4084	0.033*
C8	0.4652 (15)	0.3501 (13)	0.1956 (13)	0.029 (2)
H8	0.4112	0.4101	0.1378	0.035*
C9	0.3944 (16)	0.1735 (14)	0.1184 (13)	0.034 (3)
H9	0.2904	0.1115	0.0094	0.041*
C10	0.4813 (14)	0.0922 (12)	0.2067 (11)	0.025 (2)
H10	0.4360	−0.0281	0.1552	0.030*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0292 (8)	0.0161 (7)	0.0182 (7)	−0.0002 (5)	−0.0038 (5)	0.0069 (5)
Cl1	0.0297 (15)	0.0199 (13)	0.0253 (14)	−0.0003 (11)	0.0004 (11)	0.0086 (11)
Cl2	0.0314 (15)	0.0216 (13)	0.0248 (14)	0.0022 (11)	0.0005 (11)	0.0118 (11)
N1	0.025 (5)	0.015 (4)	0.014 (4)	0.001 (3)	0.003 (4)	0.003 (3)
N2	0.022 (4)	0.016 (4)	0.018 (4)	0.006 (3)	0.006 (4)	0.009 (3)
C1	0.025 (6)	0.035 (6)	0.023 (6)	0.002 (5)	0.004 (5)	0.014 (5)
C2	0.030 (6)	0.023 (5)	0.016 (5)	−0.007 (5)	−0.006 (5)	0.000 (4)
C3	0.033 (6)	0.018 (5)	0.028 (6)	−0.005 (5)	0.006 (5)	0.007 (5)
C4	0.027 (6)	0.016 (5)	0.028 (6)	0.005 (4)	0.003 (5)	0.011 (4)
C5	0.024 (5)	0.020 (5)	0.022 (5)	0.007 (4)	0.012 (4)	0.010 (4)
C6	0.020 (5)	0.018 (5)	0.030 (6)	0.002 (4)	0.012 (5)	0.011 (4)
C7	0.033 (6)	0.029 (6)	0.029 (6)	0.014 (5)	0.009 (5)	0.021 (5)
C8	0.031 (6)	0.038 (6)	0.035 (6)	0.018 (5)	0.011 (5)	0.030 (5)
C9	0.042 (7)	0.041 (7)	0.024 (6)	0.017 (5)	0.008 (5)	0.021 (5)
C10	0.032 (6)	0.019 (5)	0.014 (5)	0.003 (4)	−0.001 (4)	0.005 (4)

Geometric parameters (Å, º)

Cu1—N2	2.024 (7)	C3—C4	1.376 (13)
Cu1—N1	2.037 (7)	C3—H3	0.9500
Cu1—Cl1	2.272 (3)	C4—C5	1.370 (12)
Cu1—Cl2	2.280 (3)	C4—H4	0.9500
Cu1—Cl2^i	2.909 (3)	C5—C6	1.479 (13)
Cl1—Cu1^ii	3.130 (3)	C6—C7	1.392 (13)
N1—C1	1.324 (12)	C7—C8	1.370 (14)
N1—C5	1.355 (11)	C7—H7	0.9500
N2—C10	1.333 (11)	C8—C9	1.397 (14)
N2—C6	1.359 (11)	C8—H8	0.9500
C1—C2	1.394 (13)	C9—C10	1.383 (13)
C1—H1	0.9500	C9—H9	0.9500
C2—C3	1.377 (14)	C10—H10	0.9500
C2—H2	0.9500
N2—Cu1—N1	81.0 (3)	C4—C3—H3	120.2
N2—Cu1—Cl1	93.4 (2)	C2—C3—H3	120.2
N1—Cu1—Cl1	170.2 (2)	C5—C4—C3	118.9 (9)
N2—Cu1—Cl2	174.0 (2)	C5—C4—H4	120.6
N1—Cu1—Cl2	93.3 (2)	C3—C4—H4	120.6
Cl1—Cu1—Cl2	92.52 (9)	N1—C5—C4	122.3 (9)
N2—Cu1—Cl2^i	88.4 (2)	N1—C5—C6	114.5 (8)
N1—Cu1—Cl2^i	90.1 (2)	C4—C5—C6	123.2 (8)
Cl1—Cu1—Cl2^i	97.79 (9)	N2—C6—C7	121.0 (9)
Cl2—Cu1—Cl2^i	89.91 (8)	N2—C6—C5	115.8 (8)
C1—N1—C5	118.2 (8)	C7—C6—C5	123.2 (8)
C1—N1—Cu1	127.1 (7)	C8—C7—C6	119.1 (9)
C5—N1—Cu1	114.2 (6)	C8—C7—H7	120.5
C10—N2—C6	119.2 (8)	C6—C7—H7	120.5
C10—N2—Cu1	126.9 (6)	C7—C8—C9	120.2 (9)
C6—N2—Cu1	114.0 (6)	C7—C8—H8	119.9
N1—C1—C2	122.7 (9)	C9—C8—H8	119.9
N1—C1—H1	118.6	C10—C9—C8	117.5 (9)
C2—C1—H1	118.6	C10—C9—H9	121.3
C3—C2—C1	118.1 (9)	C8—C9—H9	121.3
C3—C2—H2	120.9	N2—C10—C9	123.0 (9)
C1—C2—H2	120.9	N2—C10—H10	118.5
C4—C3—C2	119.6 (9)	C9—C10—H10	118.5

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···Cl2	0.95	2.61	3.209 (11)	121
C10—H10···Cl1	0.95	2.62	3.209 (9)	121
C7—H7···Cl1^iii	0.95	2.81	3.542 (10)	135
C4—H4···Cl2^iii	0.95	2.69	3.517 (10)	146

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