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The title compound, [Cu2(C2H3O2)4(C6H4N2)2], has the familiar lantern-type structure that is characteristic of dimetal tetra­carboxyl­ates of copper and several other transition elements. The molecule lies about an inversion centre and the Cu atom is present in a distorted square-pyramidal coordination environment, consisting of four O atoms in equatorial positions and the pyridyl-N atoms of the two 4-cyano­pyridine ligands in axial positions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101009052/vj1144sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101009052/vj1144Isup2.hkl
Contains datablock I

CCDC reference: 173343

Comment top

We have been investigating the coordination behaviour of 4-cyanopyridine (4-CNpy) in the hope of being able to prepare coordination polymers containing metal ions bridged by this unsymmetrical and potentially bidentate ligand, having two possible coordination sites at the pyridyl and nitrile N atoms. Polymeric species containing 4-CNpy as a bridging ligand are known (Carlucci et al., 1994). In the absence of or at low concentrations of the acetate ion, the complex [CuCl2(4-CNpy)2] (Zhang et al., 1997), which has a polymeric step-ladder chain structure (Barman et al., 2000) in the solid state, is obtained in high yield. Using a reaction mixture of CuCl2·2H2O, 4-CNpy and NaCH3COO·3H2O in a 1:2:4 molar ratio in methanol, we have been able to isolate dark green crystals of the title compound, Cu2(µ-O2CCH3)4(4-CNpy)2, (I) in good yield. This compound has been previously prepared by other routes and its magnetic and spectroscopic properties have been reported in the literature (Dubicki & Martin, 1966; Muto et al., 1984). It has been suggested by Uekusa et al. (1992) that there is a relationship between the coordination geometry of copper and the exchange coupling constant in dimeric structures of the copper(II) acetate hydrate type. \sch

The molecular structure of (I) (Fig. 1) shows it to be structurally similar to copper(II) acetate hydrate. Both Cu atoms are present in general positions and are related by a crystallographic centre of symmetry at the mid-point of the Cu···Cu axis. The Cu—O bond lengths are close to 1.97 Å but the Cu—N distance is longer, at 2.188 (2) Å. The Cu···Cu distance of 2.600 (1) Å in (I) is shorter than the corresponding distances in Cu2(µ-O2CCH3)4(H2O)2 [2.614 Å (Brown & Chidambaram, 1973) and 2.616 Å (de Meester et al., 1973)], as well as in the two forms of Cu2(µ-O2CCH3)4(py)2 [2.645 Å (Hanic et al., 1964) and 2.630 Å (Barclay & Kannard, 1961)], but no bond is present between the Cu atoms. However, the Cu—O distances are comparable to those in the above compounds. The long Cu—L (axial ligands) distances are characteristic of Cu2(CH3CO2)4L2 type structures (Catterick & Thornton, 1977).

The distorted nature of the CuO4N square pyramid can be understood from the O—Cu—O and O—Cu—N angles. While the former are found to be in the range 88.46 (10)–169.00 (7)°, the latter are in the range 93.03 (8)–98.21 (8)°. The Cu atom is 0.1523 (7) Å away from the mean plane formed by the four equatorial O atoms. On the other hand, the coordinated N atom also lies in the same direction, at a distance of 2.336 (3) Å from the plane. However, our data prove beyond doubt that the copper coordination geometry is by no means trigonal bipyramidal. Furthermore, an examination of the packing diagram shows that there are no significant intermolecular interactions involving discrete molecules of (I). The present crystal-structure analysis of this known compound thus corroborates the validity of the chemical theory of Uekusa et al. (1992), in the sense that its previously reported antiferromagnetic (superexchange) coupling constant of 345 cm-1 (Muto et al., 1984) is consistent with the observed structure which, we believe, is reported for the first time in the present paper. Our work also indicates that 4-CNpy is only a reluctant ligand with regard to coordination in a bidentate mode.

Experimental top

A mixture of cupric chloride dihydrate (1 mmol), 4-cyanopyridine (2 mmol) and sodium acetate trihydrate (4 mmol) was mechanically stirred in methanol (20 ml) for 2 h. The small amount of light-blue precipitate was filtered off and the filtrate was kept at ca 278 K for 2 d. Large green crystals formed and these were filtered and washed with cold methanol (yield 68%). All crystals were clearly those of (I). A suitable single-crystal was mounted on a glass fibre for the X-ray diffraction experiment.

Refinement top

All H atoms were found in difference Fourier maps and were refined with isotropic atomic displacement parameters.

Computing details top

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: local software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII in WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing 50% probability displacement ellipsoids and the atom-numbering scheme. H atoms are drawn as small spheres of arbitrary radii.
tetrakis(µ-acetato-O,O')bis(4-cyanopyridine-N)dicopper(II) top
Crystal data top
[Cu2(C2H3O2)4(C6H4N2)2]Z = 1
Mr = 571.48F(000) = 290
Triclinic, P1Dx = 1.628 Mg m3
a = 7.734 (5) ÅMo Kα radiation, λ = 0.71070 Å
b = 8.432 (3) ÅCell parameters from 25 reflections
c = 9.782 (4) Åθ = 8.2–14.3°
α = 95.88 (4)°µ = 1.88 mm1
β = 112.78 (4)°T = 293 K
γ = 92.09 (4)°Irregular prism, dark green
V = 583.0 (5) Å30.34 × 0.28 × 0.16 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
1845 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.030
Graphite monochromatorθmax = 25.0°, θmin = 2.3°
ω/2θ scansh = 09
Absorption correction: ψ-scan
(North et al., 1968)
k = 1010
Tmin = 0.700, Tmax = 0.741l = 1110
2222 measured reflections3 standard reflections every 200 reflections
2055 independent reflections intensity decay: none
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)] = 0.026Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.072All H-atom parameters refined
S = 1.11 w = 1/[σ2(Fo2) + (0.0364P)2 + 0.2826P]
where P = (Fo2 + 2Fc2)/3
2055 reflections(Δ/σ)max = 0.006
194 parametersΔρmax = 0.25 e Å3
0 restraintsΔρmin = 0.30 e Å3
Crystal data top
[Cu2(C2H3O2)4(C6H4N2)2]γ = 92.09 (4)°
Mr = 571.48V = 583.0 (5) Å3
Triclinic, P1Z = 1
a = 7.734 (5) ÅMo Kα radiation
b = 8.432 (3) ŵ = 1.88 mm1
c = 9.782 (4) ÅT = 293 K
α = 95.88 (4)°0.34 × 0.28 × 0.16 mm
β = 112.78 (4)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
1845 reflections with I > 2σ(I)
Absorption correction: ψ-scan
(North et al., 1968)
Rint = 0.030
Tmin = 0.700, Tmax = 0.7413 standard reflections every 200 reflections
2222 measured reflections intensity decay: none
2055 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0260 restraints
wR(F2) = 0.072All H-atom parameters refined
S = 1.11Δρmax = 0.25 e Å3
2055 reflectionsΔρmin = 0.30 e Å3
194 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
Cu10.04167 (4)0.04818 (3)0.39355 (3)0.03404 (12)
O10.2130 (3)0.0410 (2)0.2567 (2)0.0481 (4)
O20.1342 (3)0.1639 (2)0.3737 (2)0.0468 (4)
O30.2830 (3)0.1200 (3)0.5594 (2)0.0539 (5)
O40.0692 (3)0.2421 (2)0.4405 (2)0.0514 (5)
N10.1225 (3)0.1547 (2)0.2300 (2)0.0372 (4)
N20.2778 (4)0.4892 (3)0.1493 (3)0.0639 (7)
C10.3227 (3)0.1026 (3)0.6931 (3)0.0410 (6)
C20.1325 (3)0.2639 (3)0.4596 (3)0.0395 (5)
C30.5180 (5)0.1614 (6)0.8023 (5)0.0643 (9)
C40.2085 (6)0.4214 (4)0.4401 (5)0.0582 (8)
C50.2985 (4)0.2101 (3)0.2596 (3)0.0456 (6)
C60.3475 (4)0.2931 (4)0.1642 (3)0.0495 (7)
C70.2072 (4)0.3212 (3)0.0318 (3)0.0396 (5)
C80.0247 (4)0.2634 (4)0.0013 (3)0.0518 (7)
C90.0101 (4)0.1824 (4)0.1021 (3)0.0512 (7)
C100.2479 (4)0.4132 (3)0.0706 (3)0.0475 (6)
H10.390 (4)0.179 (3)0.344 (3)0.050 (8)*
H20.074 (5)0.280 (4)0.089 (4)0.065 (10)*
H30.475 (5)0.317 (4)0.188 (4)0.076 (11)*
H40.126 (5)0.154 (5)0.083 (4)0.086 (13)*
H50.115 (6)0.490 (5)0.376 (5)0.102 (15)*
H60.548 (7)0.128 (6)0.877 (6)0.107 (19)*
H70.605 (6)0.140 (5)0.767 (5)0.093 (14)*
H80.277 (7)0.418 (5)0.393 (5)0.108 (17)*
H90.269 (6)0.458 (5)0.520 (5)0.093 (15)*
H100.535 (7)0.272 (7)0.842 (6)0.129 (18)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.03628 (18)0.03843 (18)0.03220 (17)0.00445 (11)0.01884 (13)0.00647 (11)
O10.0404 (10)0.0617 (12)0.0397 (9)0.0062 (8)0.0139 (8)0.0065 (8)
O20.0575 (12)0.0453 (10)0.0504 (10)0.0080 (8)0.0332 (9)0.0121 (8)
O30.0411 (10)0.0741 (14)0.0446 (11)0.0170 (9)0.0173 (8)0.0048 (9)
O40.0754 (14)0.0408 (10)0.0546 (11)0.0074 (9)0.0417 (11)0.0130 (8)
N10.0405 (11)0.0408 (11)0.0361 (10)0.0032 (9)0.0216 (9)0.0058 (8)
N20.0612 (16)0.0777 (18)0.0647 (16)0.0025 (13)0.0325 (14)0.0322 (14)
C10.0314 (13)0.0443 (14)0.0447 (14)0.0019 (10)0.0144 (11)0.0018 (11)
C20.0365 (13)0.0385 (13)0.0430 (13)0.0016 (10)0.0159 (11)0.0033 (10)
C30.0339 (16)0.089 (3)0.058 (2)0.0072 (16)0.0104 (15)0.0094 (19)
C40.065 (2)0.0464 (17)0.069 (2)0.0105 (15)0.0325 (19)0.0076 (16)
C50.0391 (14)0.0605 (17)0.0409 (14)0.0023 (12)0.0182 (12)0.0157 (12)
C60.0379 (15)0.0658 (18)0.0503 (15)0.0077 (13)0.0224 (12)0.0155 (13)
C70.0479 (15)0.0402 (13)0.0404 (13)0.0007 (11)0.0277 (11)0.0075 (10)
C80.0424 (15)0.073 (2)0.0400 (14)0.0068 (13)0.0148 (12)0.0191 (13)
C90.0368 (15)0.072 (2)0.0455 (15)0.0112 (13)0.0161 (12)0.0184 (13)
C100.0459 (15)0.0569 (16)0.0470 (15)0.0016 (12)0.0250 (12)0.0137 (13)
Geometric parameters (Å, º) top
Cu1—O31.963 (2)C2—C41.496 (4)
Cu1—O41.968 (2)C3—H60.76 (5)
Cu1—O21.969 (2)C3—H70.88 (4)
Cu1—O11.970 (2)C3—H100.96 (6)
Cu1—N12.188 (2)C4—H50.89 (5)
Cu1—Cu1i2.6000 (11)C4—H80.83 (5)
O1—C1i1.255 (3)C4—H90.84 (4)
O2—C21.253 (3)C5—C61.376 (4)
O3—C11.248 (3)C5—H10.92 (3)
O4—C2i1.252 (3)C6—C71.380 (4)
N1—C91.325 (4)C6—H30.93 (4)
N1—C51.332 (3)C7—C81.378 (4)
N2—C101.133 (3)C7—C101.446 (3)
C1—O1i1.255 (3)C8—C91.378 (4)
C1—C31.502 (4)C8—H20.93 (3)
C2—O4i1.252 (3)C9—H40.86 (4)
O3—Cu1—O490.76 (10)C1—C3—H6115 (4)
O3—Cu1—O289.35 (10)C1—C3—H7113 (3)
O4—Cu1—O2168.73 (7)H6—C3—H7106 (4)
O3—Cu1—O1169.00 (7)C1—C3—H10115 (3)
O4—Cu1—O188.46 (10)H6—C3—H1097 (4)
O2—Cu1—O189.28 (10)H7—C3—H10109 (4)
O3—Cu1—N193.27 (9)C2—C4—H5109 (3)
O4—Cu1—N193.03 (8)C2—C4—H8112 (3)
O2—Cu1—N198.21 (8)H5—C4—H8100 (4)
O1—Cu1—N197.72 (9)C2—C4—H9115 (3)
O3—Cu1—Cu1i82.60 (7)H5—C4—H9113 (4)
O4—Cu1—Cu1i82.26 (6)H8—C4—H9108 (4)
O2—Cu1—Cu1i86.58 (6)N1—C5—C6123.2 (3)
O1—Cu1—Cu1i86.43 (7)N1—C5—H1115.9 (19)
N1—Cu1—Cu1i173.67 (6)C6—C5—H1120.5 (19)
C1i—O1—Cu1120.25 (17)C5—C6—C7118.3 (2)
C2—O2—Cu1120.67 (17)C5—C6—H3118 (2)
C1—O3—Cu1125.24 (17)C7—C6—H3123 (2)
C2i—O4—Cu1125.84 (17)C8—C7—C6119.2 (2)
C9—N1—C5117.5 (2)C8—C7—C10119.6 (2)
C9—N1—Cu1119.33 (17)C6—C7—C10121.1 (2)
C5—N1—Cu1122.71 (17)C7—C8—C9118.0 (3)
O3—C1—O1i125.4 (2)C7—C8—H2122 (2)
O3—C1—C3116.9 (3)C9—C8—H2120 (2)
O1i—C1—C3117.7 (3)N1—C9—C8123.7 (3)
O4i—C2—O2124.6 (2)N1—C9—H4119 (3)
O4i—C2—C4117.6 (3)C8—C9—H4117 (3)
O2—C2—C4117.8 (3)N2—C10—C7177.9 (3)
O3—Cu1—O1—C1i5.8 (5)O1—Cu1—N1—C919.2 (2)
O4—Cu1—O1—C1i80.3 (2)Cu1i—Cu1—N1—C9111.5 (5)
O2—Cu1—O1—C1i88.7 (2)O3—Cu1—N1—C511.6 (2)
N1—Cu1—O1—C1i173.1 (2)O4—Cu1—N1—C5102.6 (2)
Cu1i—Cu1—O1—C1i2.1 (2)O2—Cu1—N1—C578.2 (2)
O3—Cu1—O2—C280.2 (2)O1—Cu1—N1—C5168.6 (2)
O4—Cu1—O2—C210.4 (5)Cu1i—Cu1—N1—C560.7 (6)
O1—Cu1—O2—C288.9 (2)Cu1—O3—C1—O1i2.3 (4)
N1—Cu1—O2—C2173.43 (19)Cu1—O3—C1—C3178.0 (2)
Cu1i—Cu1—O2—C22.41 (19)Cu1—O2—C2—O4i2.2 (4)
O4—Cu1—O3—C182.5 (2)Cu1—O2—C2—C4178.8 (2)
O2—Cu1—O3—C186.2 (2)C9—N1—C5—C60.2 (4)
O1—Cu1—O3—C13.3 (6)Cu1—N1—C5—C6172.5 (2)
N1—Cu1—O3—C1175.6 (2)N1—C5—C6—C70.4 (5)
Cu1i—Cu1—O3—C10.4 (2)C5—C6—C7—C81.1 (4)
O3—Cu1—O4—C2i81.0 (2)C5—C6—C7—C10177.5 (3)
O2—Cu1—O4—C2i9.5 (6)C6—C7—C8—C91.5 (4)
O1—Cu1—O4—C2i88.0 (2)C10—C7—C8—C9177.1 (3)
N1—Cu1—O4—C2i174.4 (2)C5—N1—C9—C80.6 (5)
Cu1i—Cu1—O4—C2i1.4 (2)Cu1—N1—C9—C8173.3 (3)
O3—Cu1—N1—C9160.6 (2)C7—C8—C9—N11.3 (5)
O4—Cu1—N1—C969.7 (2)C8—C7—C10—N278 (9)
O2—Cu1—N1—C9109.6 (2)C6—C7—C10—N2101 (9)
Symmetry code: (i) x, y, z+1.

Experimental details

Crystal data
Chemical formula[Cu2(C2H3O2)4(C6H4N2)2]
Mr571.48
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)7.734 (5), 8.432 (3), 9.782 (4)
α, β, γ (°)95.88 (4), 112.78 (4), 92.09 (4)
V3)583.0 (5)
Z1
Radiation typeMo Kα
µ (mm1)1.88
Crystal size (mm)0.34 × 0.28 × 0.16
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ-scan
(North et al., 1968)
Tmin, Tmax0.700, 0.741
No. of measured, independent and
observed [I > 2σ(I)] reflections
2222, 2055, 1845
Rint0.030
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.026, 0.072, 1.11
No. of reflections2055
No. of parameters194
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.25, 0.30

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, local software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPIII in WinGX (Farrugia, 1999).

Selected geometric parameters (Å, º) top
Cu1—O31.963 (2)Cu1—N12.188 (2)
Cu1—O41.968 (2)O2—C21.253 (3)
Cu1—O21.969 (2)O3—C11.248 (3)
Cu1—O11.970 (2)N2—C101.133 (3)
O3—Cu1—O490.76 (10)O3—Cu1—N193.27 (9)
O3—Cu1—O289.35 (10)O4—Cu1—N193.03 (8)
O4—Cu1—O2168.73 (7)O2—Cu1—N198.21 (8)
O3—Cu1—O1169.00 (7)O1—Cu1—N197.72 (9)
O4—Cu1—O188.46 (10)N2—C10—C7177.9 (3)
O2—Cu1—O189.28 (10)
 

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