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Acta Crystallogr Sect E Struct Rep Online. 2008 May 1; 64(Pt 5): m736–m737.
Published online 2008 April 30. doi:  10.1107/S1600536808010994
PMCID: PMC2961302

μ-Pyrazine-bis­[tetra­aqua­cadmium(II)] μ-pyrazine-bis­[tetra­acetato­cadmium(II)]


In the title dinuclear ionic complex, [Cd2(C4H4N2)(H2O)8][Cd2(CH3CO2)8(C4H4N2)], the cation and anion are disordered equally over a site with symmetry mmm. The CdII ions and the N atoms of the bridging pyrazine ligand lie on the inter­section of two crystallographic mirror planes. The C atoms of the bridging pyrazine ligand lie on one of these mirror planes, and the acetate groups and water mol­ecules lie across the inter­secting mirror planes. Each CdII atom in the cation is five-coordinated by four O atoms from four water mol­ecules and one N atom from the bridging pyrazine ligand, whereas each CdII in the anion is nine-coordinated by four pairs of O atoms from the bidentate acetate ligands and one N atom from the bridging pyrazine ligand. In the crystal structure, each anion is surrounded by eight nearest-neighbour cations and vice versa. The crystal structure is stabilized by ionic inter­actions as well as by C—H(...)O inter­actions.

Related literature

For bond-length data, see: Allen et al. (1987 [triangle]). For CdII coord­ination chemistry, applications and related structures, see: Filipović et al. (2008 [triangle]); Inoue et al. (2000 [triangle]); Pons et al. (2007 [triangle]); Xia et al. (2004 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-64-0m736-scheme1.jpg


Crystal data

  • [Cd2(C4H4N2)(H2O)8][Cd2(C2H3O2)8(C4H4N2)]
  • M r = 1226.26
  • Tetragonal, An external file that holds a picture, illustration, etc.
Object name is e-64-0m736-efi13.jpg
  • a = 16.7103 (4) Å
  • c = 7.3533 (2) Å
  • V = 2053.29 (9) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 2.13 mm−1
  • T = 100.0 (1) K
  • 0.58 × 0.08 × 0.05 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2005 [triangle]) T min = 0.371, T max = 0.895
  • 12617 measured reflections
  • 1246 independent reflections
  • 1145 reflections with I > 2σ(I)
  • R int = 0.037


  • R[F 2 > 2σ(F 2)] = 0.016
  • wR(F 2) = 0.034
  • S = 1.06
  • 1246 reflections
  • 73 parameters
  • 2 restraints
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.59 e Å−3
  • Δρmin = −0.44 e Å−3

Data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005 [triangle]); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808010994/ci2576sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808010994/ci2576Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report


The authors thank the Malaysian Government and Universiti Sains Malaysia for the Scientific Advancement Grant Allocation (SAGA) grant No. 304/PFIZIK/653003/A118. SC thanks Prince of Songkla University for generous support.

supplementary crystallographic information


The investigations of coordination compounds between cadmium(II) and O and N donors atoms have attracted much attention due to their potential application in a number of areas (Inoue et al., 2000; Pons et al., 2007; Xia et al., 2004), including cytotoxic activities (Filipović et al., 2008). We report herein, the synthesis and crystal structure of the title compound which exhibits a mixed coordination for CdII atom i.e nine- and five-coordination mode for CdII, which is a rare case.

In the title compound, both [Cd2(H2O)8(C4H4N2)]4+ cations and [Cd2(CH3CO2)8(C4H4N2)]4- anions lie on the site symmetry mmm. The CdII and the N atoms of the bridging pyrazine ligand lie on the intersection of two crystallographic mirror planes, one perpenidicular to the c axis (z = 0) and the other parallel to the c axis and passing through the mid points of the a and b axis. The C atoms of the bridging pyrazine ligand lie on the z = 0 mirror plane, and the acetate groups and water molecules lie across the intersecting mirror planes. There are two molecules of the title complex in the unit cell.

In the structure, the cation contains two CdII ions, eight water molecules and one bridging pyrazine ligand whereas the anion contains two CdII ions, eight acetate and one bridging pyrazine ligands. Each of the CdII in the cation is five-coordinated with four O atoms from four water molecules and one N atom from a bridging pyrazine ligand, whereas each CdII in the anion is nine-coordinated with four pairs of chelate O atoms from the bidentate acetate ligands and one N atom from the bridging pyrazine ligand. The Cd—O(acetate) bond distances are 2.3458 (14) and 2.5200 (14) Å, and the Cd—O(water) and Cd—N distances are 2.2783 (15) Å and 2.3470 (15) Å, respectively. The O(water)—Cd—O(water) bond angles lie in the range 64.15 (8)°-174.10 (7)°, whereas, the O(acetate)—Cd—O(acetate) bond angles are in the range 53.57 (7)°-158.87 (6)°. The N—Cd—O(water) angle is 92.95 (3)° and N—Cd—O(acetate) angles are 132.77 (3)° and 79.43 (3)°, respectively. The geometric parameters are comparable to those reported for other Cd—O and Cd—N donor complexes (Inoue et al., 2000; Pons et al., 2007; Xia et al., 2004).

In the crystal packing (Fig. 2 and Fig.3), each anion is surrounded by eight nearest neighbour cations and vice-versa. The crystal structure is stablized by ionic interactions as well as by weak C—H···O interactions (Table 1).


The title compound was synthesized by mixing Cd(CH3COO)2 and pyrazine with a 2:1 molar ratio in a hot methanol-water (2:1 v/v) solution and stirred for 10 min at room temperature. The solution was then left at ambient temperature to allow the solvent to slowly evaporate. Colourless crystals of the title compound suitable for X-ray structure determination were obtained after a few weeks.


Water H atoms were located in a difference map and refined isotropically, with a O—H distance restraint of 0.800 (1) Å. C-bound H atoms were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.96 Å. The Uiso value of H1A was constrained to 1.2Ueq(C1) and for other H atoms the Uiso values were refined. A rotating group model was used for the methyl group.


Fig. 1.
The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering. The cations and anions occupy the same site with equal occupancy. Symmetry codes for the Cd1A ion: (A) -x, 1 - y, -z. Symmetry codes ...
Fig. 2.
The crystal packing of the title compound, viewed along the c axis, showing a layer of the cations and anions.
Fig. 3.
The crystal packing of the title compound, viewed along the a axis, showing the same layer of cations and anions in Fig. 2.

Crystal data

[Cd2(C4H4N2)(H2O)8][Cd2(C2H3O2)8(C4H4N2)]Dx = 1.983 Mg m3
Mr = 1226.26Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4/mcmCell parameters from 1246 reflections
Hall symbol: -I 4 2cθ = 1.7–35.0°
a = 16.7103 (4) ŵ = 2.13 mm1
c = 7.3533 (2) ÅT = 100 K
V = 2053.29 (9) Å3Needle, colourless
Z = 20.58 × 0.08 × 0.05 mm
F(000) = 1208

Data collection

Bruker SMART APEXII CCD area-detector diffractometer1246 independent reflections
Radiation source: fine-focus sealed tube1145 reflections with I > 2σ(I)
graphiteRint = 0.037
Detector resolution: 8.33 pixels mm-1θmax = 35.0°, θmin = 1.7°
ω scansh = −26→26
Absorption correction: multi-scan (SADABS; Bruker, 2005)k = −26→26
Tmin = 0.371, Tmax = 0.895l = −11→11
12617 measured reflections


Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.016Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.034H atoms treated by a mixture of independent and constrained refinement
S = 1.06w = 1/[σ2(Fo2) + (0.0089P)2 + 1.5621P] where P = (Fo2 + 2Fc2)/3
1246 reflections(Δ/σ)max = 0.002
73 parametersΔρmax = 0.59 e Å3
2 restraintsΔρmin = −0.44 e Å3

Special details

Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.
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)

xyzUiso*/UeqOcc. (<1)
Cd10.158218 (5)0.341782 (5)0.00000.01214 (4)
O10.16811 (7)0.21686 (8)0.1438 (2)0.0156 (2)0.50
O20.04830 (8)0.27097 (9)0.1708 (2)0.0183 (3)0.50
C20.09773 (11)0.21621 (11)0.2069 (3)0.0144 (3)0.50
C30.07138 (12)0.14714 (12)0.3238 (3)0.0212 (4)0.50
H3A0.03440.16590.41420.036 (9)*0.50
H3B0.11720.12400.38250.038 (8)*0.50
H3C0.04580.10750.24930.031 (8)*0.50
O1W0.11198 (8)0.28563 (8)0.2621 (2)0.0170 (3)0.50
H1W10.0654 (4)0.2746 (17)0.262 (4)0.020 (7)*0.50
H2W10.1447 (16)0.2523 (16)0.287 (5)0.055 (11)*0.50
N10.05890 (6)0.44110 (6)0.00000.0131 (3)
C1−0.01905 (7)0.42237 (7)0.00000.0144 (2)

Atomic displacement parameters (Å2)

Cd10.00955 (4)0.00955 (4)0.01731 (7)0.00080 (4)0.0000.000
O10.0119 (5)0.0133 (5)0.0216 (7)0.0003 (4)0.0008 (5)0.0015 (5)
O20.0137 (6)0.0151 (6)0.0260 (8)0.0028 (5)0.0007 (6)0.0037 (5)
C20.0131 (7)0.0118 (7)0.0181 (8)−0.0016 (5)−0.0025 (6)0.0004 (6)
C30.0189 (9)0.0195 (9)0.0251 (10)−0.0014 (7)0.0006 (7)0.0074 (8)
O1W0.0121 (5)0.0156 (6)0.0233 (7)0.0022 (5)0.0023 (5)0.0030 (5)
N10.0119 (4)0.0119 (4)0.0155 (7)0.0010 (5)0.0000.000
C10.0122 (5)0.0113 (5)0.0196 (6)0.0004 (4)0.0000.000

Geometric parameters (Å, °)

Cd1—O1W2.2782 (15)O1—C21.264 (2)
Cd1—O1Wi2.2783 (15)O2—C21.261 (2)
Cd1—O1Wii2.2783 (15)C2—C31.505 (3)
Cd1—O1Wiii2.2783 (15)C3—H3A0.96
Cd1—O12.3458 (14)C3—H3B0.96
Cd1—O1i2.3458 (14)C3—H3C0.96
Cd1—O1ii2.3458 (14)O1W—H1W10.800 (1)
Cd1—O1iii2.3458 (14)O1W—H2W10.800 (1)
Cd1—N12.3470 (15)N1—C1i1.3396 (15)
Cd1—O2i2.5200 (14)N1—C11.3397 (15)
Cd1—O2ii2.5200 (14)C1—C1iv1.384 (2)
Cd1—O22.5200 (14)C1—H1A0.96
O1W—Cd1—O1Wi64.15 (8)O1i—Cd1—O2ii81.84 (5)
O1W—Cd1—O1Wii174.10 (7)O1ii—Cd1—O2ii53.77 (4)
O1Wi—Cd1—O1Wii115.52 (8)O1iii—Cd1—O2ii113.02 (5)
O1W—Cd1—O1Wiii115.51 (8)N1—Cd1—O2ii79.43 (3)
O1Wi—Cd1—O1Wiii174.10 (7)O2i—Cd1—O2ii59.77 (8)
O1Wii—Cd1—O1Wiii64.15 (8)O1—Cd1—O253.77 (4)
O1—Cd1—O1i70.82 (6)O1i—Cd1—O2113.02 (5)
O1—Cd1—O1ii94.46 (6)O1ii—Cd1—O2147.15 (4)
O1i—Cd1—O1ii53.57 (7)O1iii—Cd1—O281.84 (5)
O1—Cd1—O1iii53.57 (7)N1—Cd1—O279.43 (3)
O1i—Cd1—O1iii94.46 (6)O2i—Cd1—O2115.86 (8)
O1ii—Cd1—O1iii70.82 (6)O2ii—Cd1—O2158.87 (6)
O1W—Cd1—N192.95 (3)C2—O1—Cd196.17 (11)
O1Wi—Cd1—N192.95 (3)C2—O2—Cd188.18 (11)
O1Wii—Cd1—N192.95 (3)O2—C2—O1121.73 (17)
O1Wiii—Cd1—N192.95 (3)O2—C2—C3119.02 (16)
O1—Cd1—N1132.77 (3)O1—C2—C3119.23 (16)
O1i—Cd1—N1132.77 (3)Cd1—O1W—H1W1115 (2)
O1ii—Cd1—N1132.77 (3)Cd1—O1W—H2W1104 (3)
O1iii—Cd1—N1132.77 (3)H1W1—O1W—H2W1120 (3)
O1—Cd1—O2i113.02 (5)C1i—N1—C1117.01 (15)
O1i—Cd1—O2i53.77 (4)C1i—N1—Cd1121.49 (8)
O1ii—Cd1—O2i81.84 (5)C1—N1—Cd1121.49 (8)
O1iii—Cd1—O2i147.15 (4)N1—C1—C1iv121.50 (8)
N1—Cd1—O2i79.43 (3)N1—C1—H1A120.0
O1—Cd1—O2ii147.15 (4)C1iv—C1—H1A118.5
O1i—Cd1—O1—C2137.93 (10)O1Wiii—Cd1—N1—C1i−122.12 (4)
O1ii—Cd1—O1—C2−173.19 (14)O1—Cd1—N1—C1i142.13 (5)
O1iii—Cd1—O1—C2−111.03 (11)O1i—Cd1—N1—C1i37.87 (5)
N1—Cd1—O1—C26.81 (14)O1ii—Cd1—N1—C1i−37.87 (5)
O2i—Cd1—O1—C2103.79 (12)O1iii—Cd1—N1—C1i−142.13 (5)
O2ii—Cd1—O1—C2173.28 (11)O2i—Cd1—N1—C1i30.46 (4)
O2—Cd1—O1—C2−2.25 (11)O2ii—Cd1—N1—C1i−30.46 (4)
O1—Cd1—O2—C22.24 (11)O2—Cd1—N1—C1i149.54 (4)
O1i—Cd1—O2—C2−38.85 (13)O1W—Cd1—N1—C1−57.88 (4)
O1ii—Cd1—O2—C219.05 (17)O1Wi—Cd1—N1—C1−122.12 (4)
O1iii—Cd1—O2—C252.55 (12)O1Wii—Cd1—N1—C1122.12 (4)
N1—Cd1—O2—C2−171.01 (12)O1Wiii—Cd1—N1—C157.88 (4)
O2i—Cd1—O2—C2−98.33 (12)O1—Cd1—N1—C1−37.87 (5)
O2ii—Cd1—O2—C2−171.01 (12)O1i—Cd1—N1—C1−142.13 (5)
Cd1—O2—C2—O1−3.94 (19)O1ii—Cd1—N1—C1142.13 (5)
Cd1—O2—C2—C3177.83 (17)O1iii—Cd1—N1—C137.87 (5)
Cd1—O1—C2—O24.3 (2)O2i—Cd1—N1—C1−149.54 (4)
Cd1—O1—C2—C3−177.52 (16)O2ii—Cd1—N1—C1149.54 (4)
O1W—Cd1—N1—C1i122.12 (4)O2—Cd1—N1—C1−30.46 (4)
O1Wi—Cd1—N1—C1i57.88 (4)C1i—N1—C1—C1iv0.0
O1Wii—Cd1—N1—C1i−57.88 (4)Cd1—N1—C1—C1iv180.0

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

Hydrogen-bond geometry (Å, °)

C1—H1A···O20.962.473.0405 (18)118
C1—H1A···O1Wv0.962.563.2700 (17)131
C1—H1A···O2vi0.962.473.0405 (18)118
C1—H1A···O1Wvii0.962.563.2700 (17)131

Symmetry codes: (v) −x, y, −z+1/2; (vi) x, y, −z; (vii) −x, y, z−1/2.


Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: CI2576).


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