The title compound, (C
12H
11N
3)
2[Cd
2Cl
8], consists of two discrete 2-(3-pyridinio)benzimidazolium cations and one [Cd
2Cl
8]
4− anion. The dimeric [Cd
2Cl
8]
4− anion lies about an inversion centre and consists of two distorted [CdCl
5] trigonal bipyramids which share a common edge. The two Cd atoms are each coordinated by two μ-Cl atoms and three terminal Cl atoms, with a Cd
Cd separation of 3.9853 (6) Å. The packing displays two-dimensional hydrogen-bonded sheets, which are further linked by C—H
Cl contacts and π–π stacking interactions to yield a three-dimensional network.
Supporting information
CCDC reference: 269021
2-(3-Pyridyl)benzimidazole was synthesized according to the literature method of Alcalde et al. (1992). An aqueous solution (20 ml) of 2-(3-pyridyl)benzimidazole (1.6 mmol), CdCl2 (1.2 mmol) and HCl (0.2 ml) was continuously stirred for about 30 min, and the solution was then allowed to stand at room temperature for several days, to give colourless crystals of (I) (yield 81%). Analysis calculated for C24H22Cd2N6Cl8: C 31.92, H 2.46, N 9.31%; found: C 32.12, H 2.71, N 9.37%. IR (KBr, ν, cm−1): 3468 (s), 1625 (s), 1526 (s), 1378 (s), 1261 (m), 1114 (m), 876 (s), 811 (s), 765 (m), 666 (m), 527 (m), 488 (m).
All H atoms were visible in difference maps and were treated as riding atoms, with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C).
Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1994); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) in WinGX (version 1.70.01; Farrugia, 1999); molecular graphics: SHELXL97 and PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.
Bis[2-(3-pyridinio)benzimidazolium] di-µ-chloro-bis[trichlorocadmium(II)]
top
Crystal data top
(C12N3H11)2[Cd2Cl8] | F(000) = 880 |
Mr = 902.88 | Dx = 2.029 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 3960 reflections |
a = 7.5295 (5) Å | θ = 3.1–25.0° |
b = 15.8570 (13) Å | µ = 2.19 mm−1 |
c = 12.3755 (9) Å | T = 293 K |
β = 90.457 (6)° | Prism, colourless |
V = 1477.53 (19) Å3 | 0.20 × 0.15 × 0.06 mm |
Z = 2 | |
Data collection top
Siemens SMART CCD area-detector diffractometer | 2593 independent reflections |
Radiation source: fine-focus sealed tube | 2209 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.058 |
ω scans | θmax = 25.0°, θmin = 3.1° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→8 |
Tmin = 0.643, Tmax = 0.880 | k = −15→18 |
9164 measured reflections | l = −14→14 |
Refinement top
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)] = 0.031 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.091 | H-atom parameters constrained |
S = 1.16 | w = 1/[σ2(Fo2) + (0.0262P)2 + 2.7025P] where P = (Fo2 + 2Fc2)/3 |
2593 reflections | (Δ/σ)max = 0.001 |
181 parameters | Δρmax = 0.74 e Å−3 |
0 restraints | Δρmin = −0.58 e Å−3 |
Crystal data top
(C12N3H11)2[Cd2Cl8] | V = 1477.53 (19) Å3 |
Mr = 902.88 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.5295 (5) Å | µ = 2.19 mm−1 |
b = 15.8570 (13) Å | T = 293 K |
c = 12.3755 (9) Å | 0.20 × 0.15 × 0.06 mm |
β = 90.457 (6)° | |
Data collection top
Siemens SMART CCD area-detector diffractometer | 2593 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2209 reflections with I > 2σ(I) |
Tmin = 0.643, Tmax = 0.880 | Rint = 0.058 |
9164 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.031 | 0 restraints |
wR(F2) = 0.091 | H-atom parameters constrained |
S = 1.16 | Δρmax = 0.74 e Å−3 |
2593 reflections | Δρmin = −0.58 e Å−3 |
181 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 | x | y | z | Uiso*/Ueq | |
Cd1 | 0.57513 (5) | 0.50178 (2) | 0.34599 (3) | 0.01288 (13) | |
Cl1 | 0.72097 (15) | 0.47411 (8) | 0.52910 (9) | 0.0147 (3) | |
Cl2 | 0.88392 (17) | 0.45816 (8) | 0.25981 (10) | 0.0196 (3) | |
Cl3 | 0.40480 (16) | 0.39105 (8) | 0.25211 (9) | 0.0174 (3) | |
Cl4 | 0.58697 (16) | 0.65098 (8) | 0.30089 (10) | 0.0188 (3) | |
N1 | 0.8397 (5) | 0.2605 (3) | 0.2625 (3) | 0.0125 (9) | |
H1 | 0.8324 | 0.3137 | 0.2498 | 0.015* | |
N3 | 0.9056 (5) | 0.1280 (3) | 0.2445 (3) | 0.0136 (9) | |
H3 | 0.9485 | 0.0821 | 0.2185 | 0.016* | |
N11 | 1.1689 (5) | 0.1751 (3) | −0.0532 (3) | 0.0150 (9) | |
H11 | 1.2004 | 0.1339 | −0.0939 | 0.018* | |
C2 | 0.9237 (6) | 0.2039 (3) | 0.2001 (4) | 0.0118 (10) | |
C4 | 0.8076 (6) | 0.1337 (3) | 0.3386 (4) | 0.0129 (10) | |
C5 | 0.7542 (7) | 0.0733 (3) | 0.4122 (4) | 0.0183 (11) | |
H5 | 0.7813 | 0.0165 | 0.4033 | 0.022* | |
C6 | 0.6581 (7) | 0.1022 (3) | 0.4997 (4) | 0.0186 (11) | |
H6 | 0.6182 | 0.0636 | 0.5508 | 0.022* | |
C7 | 0.6192 (6) | 0.1885 (3) | 0.5134 (4) | 0.0161 (11) | |
H7 | 0.5570 | 0.2056 | 0.5742 | 0.019* | |
C8 | 0.6709 (6) | 0.2484 (3) | 0.4391 (4) | 0.0147 (11) | |
H8 | 0.6433 | 0.3051 | 0.4475 | 0.018* | |
C9 | 0.7667 (6) | 0.2192 (3) | 0.3506 (4) | 0.0126 (10) | |
C12 | 1.0755 (6) | 0.1582 (3) | 0.0352 (4) | 0.0147 (11) | |
H12 | 1.0461 | 0.1028 | 0.0519 | 0.018* | |
C13 | 1.0224 (6) | 0.2232 (3) | 0.1020 (4) | 0.0120 (10) | |
C14 | 1.0692 (6) | 0.3056 (3) | 0.0743 (4) | 0.0148 (11) | |
H14 | 1.0355 | 0.3505 | 0.1179 | 0.018* | |
C15 | 1.1656 (6) | 0.3200 (3) | −0.0181 (4) | 0.0180 (11) | |
H15 | 1.1966 | 0.3747 | −0.0374 | 0.022* | |
C16 | 1.2156 (6) | 0.2531 (3) | −0.0815 (4) | 0.0164 (11) | |
H16 | 1.2816 | 0.2622 | −0.1436 | 0.020* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.0152 (2) | 0.0106 (2) | 0.0129 (2) | −0.00084 (14) | 0.00075 (14) | 0.00002 (14) |
Cl1 | 0.0142 (6) | 0.0161 (6) | 0.0139 (6) | 0.0011 (5) | 0.0005 (5) | 0.0015 (5) |
Cl2 | 0.0198 (6) | 0.0124 (6) | 0.0268 (7) | −0.0032 (5) | 0.0086 (5) | −0.0058 (5) |
Cl3 | 0.0219 (7) | 0.0162 (6) | 0.0140 (6) | −0.0055 (5) | 0.0032 (5) | −0.0029 (5) |
Cl4 | 0.0197 (7) | 0.0133 (6) | 0.0232 (7) | −0.0019 (5) | −0.0022 (5) | 0.0060 (5) |
N1 | 0.015 (2) | 0.008 (2) | 0.015 (2) | 0.0016 (17) | 0.0016 (17) | 0.0000 (17) |
N3 | 0.016 (2) | 0.010 (2) | 0.014 (2) | 0.0034 (17) | 0.0008 (17) | −0.0032 (17) |
N11 | 0.013 (2) | 0.018 (2) | 0.014 (2) | 0.0036 (18) | 0.0003 (17) | −0.0035 (18) |
C2 | 0.012 (2) | 0.014 (3) | 0.009 (2) | −0.001 (2) | −0.0017 (19) | −0.004 (2) |
C4 | 0.011 (2) | 0.014 (3) | 0.013 (2) | −0.001 (2) | −0.0017 (19) | −0.004 (2) |
C5 | 0.024 (3) | 0.012 (3) | 0.019 (3) | 0.002 (2) | −0.003 (2) | 0.000 (2) |
C6 | 0.021 (3) | 0.021 (3) | 0.014 (2) | −0.004 (2) | 0.000 (2) | 0.003 (2) |
C7 | 0.013 (3) | 0.023 (3) | 0.012 (2) | 0.000 (2) | 0.004 (2) | −0.004 (2) |
C8 | 0.015 (3) | 0.014 (3) | 0.015 (3) | 0.003 (2) | −0.002 (2) | −0.005 (2) |
C9 | 0.013 (3) | 0.013 (3) | 0.011 (2) | −0.001 (2) | −0.0028 (19) | −0.001 (2) |
C12 | 0.012 (3) | 0.014 (3) | 0.019 (3) | −0.002 (2) | −0.001 (2) | 0.000 (2) |
C13 | 0.009 (2) | 0.015 (3) | 0.012 (2) | 0.000 (2) | −0.0040 (19) | 0.002 (2) |
C14 | 0.013 (2) | 0.015 (3) | 0.016 (3) | 0.000 (2) | −0.003 (2) | −0.003 (2) |
C15 | 0.015 (3) | 0.016 (3) | 0.022 (3) | −0.005 (2) | −0.002 (2) | 0.005 (2) |
C16 | 0.015 (3) | 0.021 (3) | 0.013 (3) | −0.002 (2) | 0.000 (2) | 0.002 (2) |
Geometric parameters (Å, º) top
Cd1—Cl4 | 2.4325 (13) | C4—C9 | 1.398 (7) |
Cd1—Cl3 | 2.4605 (12) | C5—C6 | 1.386 (7) |
Cd1—Cl1 | 2.5483 (12) | C5—H5 | 0.93 |
Cd1—Cl2 | 2.6573 (13) | C6—C7 | 1.411 (7) |
Cd1—Cl1i | 2.7498 (12) | C6—H6 | 0.93 |
Cl1—Cd1i | 2.7498 (12) | C7—C8 | 1.380 (7) |
N1—C2 | 1.345 (6) | C7—H7 | 0.93 |
N1—C9 | 1.389 (6) | C8—C9 | 1.395 (7) |
N1—H1 | 0.8598 | C8—H8 | 0.93 |
N3—C2 | 1.330 (6) | C12—C13 | 1.382 (7) |
N3—C4 | 1.386 (6) | C12—H12 | 0.93 |
N3—H3 | 0.8598 | C13—C14 | 1.397 (7) |
N11—C12 | 1.332 (6) | C14—C15 | 1.378 (7) |
N11—C16 | 1.333 (7) | C14—H14 | 0.93 |
N11—H11 | 0.8595 | C15—C16 | 1.374 (7) |
C2—C13 | 1.461 (6) | C15—H15 | 0.93 |
C4—C5 | 1.385 (7) | C16—H16 | 0.93 |
| | | |
Cl4—Cd1—Cl3 | 127.27 (4) | C6—C5—H5 | 121.9 |
Cl4—Cd1—Cl1 | 110.80 (4) | C5—C6—C7 | 121.6 (5) |
Cl3—Cd1—Cl1 | 121.09 (4) | C5—C6—H6 | 119.2 |
Cl4—Cd1—Cl2 | 97.31 (4) | C7—C6—H6 | 119.2 |
Cl3—Cd1—Cl2 | 94.54 (4) | C8—C7—C6 | 121.9 (4) |
Cl1—Cd1—Cl2 | 86.55 (4) | C8—C7—H7 | 119.1 |
Cl4—Cd1—Cl1i | 91.44 (4) | C6—C7—H7 | 119.1 |
Cl3—Cd1—Cl1i | 86.72 (4) | C7—C8—C9 | 116.5 (5) |
Cl1—Cd1—Cl1i | 82.51 (4) | C7—C8—H8 | 121.8 |
Cl2—Cd1—Cl1i | 167.89 (4) | C9—C8—H8 | 121.8 |
Cd1—Cl1—Cd1i | 97.49 (4) | N1—C9—C8 | 132.1 (5) |
C2—N1—C9 | 109.1 (4) | N1—C9—C4 | 106.5 (4) |
C2—N1—H1 | 125.4 | C8—C9—C4 | 121.4 (5) |
C9—N1—H1 | 125.5 | N11—C12—C13 | 119.9 (5) |
C2—N3—C4 | 110.1 (4) | N11—C12—H12 | 120.0 |
C2—N3—H3 | 124.9 | C13—C12—H12 | 120.0 |
C4—N3—H3 | 125.0 | C12—C13—C14 | 118.3 (4) |
C12—N11—C16 | 122.9 (4) | C12—C13—C2 | 119.5 (5) |
C12—N11—H11 | 118.6 | C14—C13—C2 | 122.1 (4) |
C16—N11—H11 | 118.5 | C15—C14—C13 | 119.7 (5) |
N3—C2—N1 | 108.5 (4) | C15—C14—H14 | 120.2 |
N3—C2—C13 | 125.9 (4) | C13—C14—H14 | 120.2 |
N1—C2—C13 | 125.6 (5) | C16—C15—C14 | 119.6 (5) |
C5—C4—N3 | 131.8 (5) | C16—C15—H15 | 120.2 |
C5—C4—C9 | 122.4 (4) | C14—C15—H15 | 120.2 |
N3—C4—C9 | 105.8 (4) | N11—C16—C15 | 119.5 (4) |
C4—C5—C6 | 116.2 (5) | N11—C16—H16 | 120.2 |
C4—C5—H5 | 121.9 | C15—C16—H16 | 120.2 |
| | | |
Cl4—Cd1—Cl1—Cd1i | 88.69 (5) | C7—C8—C9—C4 | 0.0 (7) |
Cl3—Cd1—Cl1—Cd1i | −81.56 (5) | C5—C4—C9—N1 | −179.6 (4) |
Cl2—Cd1—Cl1—Cd1i | −174.79 (4) | N3—C4—C9—N1 | 0.8 (5) |
Cl1i—Cd1—Cl1—Cd1i | 0.0 | C5—C4—C9—C8 | 0.9 (7) |
C4—N3—C2—N1 | 0.0 (5) | N3—C4—C9—C8 | −178.7 (4) |
C4—N3—C2—C13 | 178.3 (4) | C16—N11—C12—C13 | 0.2 (7) |
C9—N1—C2—N3 | 0.6 (5) | N11—C12—C13—C14 | 0.0 (7) |
C9—N1—C2—C13 | −177.7 (4) | N11—C12—C13—C2 | −178.6 (4) |
C2—N3—C4—C5 | 180.0 (5) | N3—C2—C13—C12 | 13.4 (7) |
C2—N3—C4—C9 | −0.5 (5) | N1—C2—C13—C12 | −168.5 (5) |
N3—C4—C5—C6 | 179.0 (5) | N3—C2—C13—C14 | −165.1 (5) |
C9—C4—C5—C6 | −0.5 (7) | N1—C2—C13—C14 | 13.0 (7) |
C4—C5—C6—C7 | −0.8 (7) | C12—C13—C14—C15 | 0.2 (7) |
C5—C6—C7—C8 | 1.6 (8) | C2—C13—C14—C15 | 178.7 (4) |
C6—C7—C8—C9 | −1.2 (7) | C13—C14—C15—C16 | −0.4 (7) |
C2—N1—C9—C8 | 178.6 (5) | C12—N11—C16—C15 | −0.5 (7) |
C2—N1—C9—C4 | −0.9 (5) | C14—C15—C16—N11 | 0.6 (7) |
C7—C8—C9—N1 | −179.4 (5) | | |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Cl2 | 0.86 | 2.33 | 3.152 (4) | 161 |
N3—H3···Cl2ii | 0.86 | 2.35 | 3.126 (4) | 150 |
N11—H11···Cl1ii | 0.86 | 2.72 | 3.306 (4) | 127 |
N11—H11···Cl3iii | 0.86 | 2.49 | 3.182 (4) | 138 |
C12—H12···Cl1iv | 0.93 | 2.75 | 3.396 (5) | 128 |
C14—H14···Cl2 | 0.93 | 2.71 | 3.623 (5) | 168 |
C16—H16···Cl4v | 0.93 | 2.59 | 3.458 (5) | 156 |
Symmetry codes: (ii) −x+2, y−1/2, −z+1/2; (iii) x+1, −y+1/2, z−1/2; (iv) x, −y+1/2, z−1/2; (v) −x+2, −y+1, −z. |
Experimental details
Crystal data |
Chemical formula | (C12N3H11)2[Cd2Cl8] |
Mr | 902.88 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 7.5295 (5), 15.8570 (13), 12.3755 (9) |
β (°) | 90.457 (6) |
V (Å3) | 1477.53 (19) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 2.19 |
Crystal size (mm) | 0.20 × 0.15 × 0.06 |
|
Data collection |
Diffractometer | Siemens SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.643, 0.880 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9164, 2593, 2209 |
Rint | 0.058 |
(sin θ/λ)max (Å−1) | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.091, 1.16 |
No. of reflections | 2593 |
No. of parameters | 181 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.74, −0.58 |
Selected geometric parameters (Å, º) topCd1—Cl4 | 2.4325 (13) | Cd1—Cl2 | 2.6573 (13) |
Cd1—Cl3 | 2.4605 (12) | Cd1—Cl1i | 2.7498 (12) |
Cd1—Cl1 | 2.5483 (12) | | |
| | | |
Cl4—Cd1—Cl3 | 127.27 (4) | Cl3—Cd1—Cl1 | 121.09 (4) |
Cl4—Cd1—Cl1 | 110.80 (4) | Cl2—Cd1—Cl1i | 167.89 (4) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Cl2 | 0.86 | 2.33 | 3.152 (4) | 161 |
N3—H3···Cl2ii | 0.86 | 2.35 | 3.126 (4) | 150 |
N11—H11···Cl1ii | 0.86 | 2.72 | 3.306 (4) | 127 |
N11—H11···Cl3iii | 0.86 | 2.49 | 3.182 (4) | 138 |
C12—H12···Cl1iv | 0.93 | 2.75 | 3.396 (5) | 128 |
C14—H14···Cl2 | 0.93 | 2.71 | 3.623 (5) | 168 |
C16—H16···Cl4v | 0.93 | 2.59 | 3.458 (5) | 156 |
Symmetry codes: (ii) −x+2, y−1/2, −z+1/2; (iii) x+1, −y+1/2, z−1/2; (iv) x, −y+1/2, z−1/2; (v) −x+2, −y+1, −z. |
Crystal engineering of inorganic–organic hybrid materials is based on a modular approach, where discrete building blocks are constructed into extended networks. In the search for reliable strategies for crystal synthesis by design, a key goal is the identification and exploitation of robust synthons to control the relative orientation of the molecular component of the solid. Among the usual interactions found to assemble the molecular crystal, hydrogen-bonding interactions have attracted the most attention. In the case of transition metal chloride complexes, the M—Cl moieties (M is a transition metal) can act as good hydrogen-bond acceptors (Gillon et al., 2000; Lewis & Orpen, 1998; Luque et al., 2002). We report here the title complex salt, (I), composed of a novel [Cd2Cl8]4− anion and two protonated 2-(3-pyridyl)benzimidazole cations, in which the N—H···Cl hydrogen bonds and π–π stacking interactions aggregate the anions and cations into a three-dimensional network.
As shown in Fig. 1, compound (I) is composed of two 2-(3-pyridinio)benzimidazolium cations and a novel [Cd2Cl8]4− anion which lies about an inversion centre, chosen for convenience to be (1/2, 1/2, 1/2). In the unique cation, the pyridyl ring is rotated out of the benzimidazyl ring plane with a dihedral angle of 12.9 (2)°. The dimeric [Cd2Cl8]4− anion can best be described as consisting of two distorted trigonal bipyramids, [CdCl5], which share a common edge. The bridging Cl1 atom is axial to one Cd atom and equatorial to the other. The Cd1—Cl1—Cd1i—Cl1i ring (see Table 1 for symmetry code) is strictly planar because of the inversion centre. In the [CdCl5] moiety, atoms Cl1, Cl3 and Cl4 are equatorial, while Cl2 and Cl1i are axial. Atom Cd1 and these three equatorial atoms are almost coplanar, with atom Cd1 being 0.1305 (8) Å from the Cl1/Cl3/Cl4 plane and displaced toward the axial atom Cl2. According to the different classes of Cd—Cl bond lengths, a logical sequence is apparent: Cd—Cl(axial,bridging) 2.7498 (12) Å > Cd—Cl(axial,terminal) 2.6573 (13) Å > Cd—Cl(equatorial,bridging) 2.5483 (12) Å > Cd—Cl(equatorial,terminal) 2.4605 (11) and 2.4325 (13) Å (Table 1). There is clearly no Cd—Cd bond in the dimer, the Cd···Cd distance of 3.9853 (6) Å being longer than the value of 3.53 Å found for the Cd···Cd distance in the dimeric [Cd2Cl6]2− anion (Bart et al., 1980).
The dimeric [Cd2Cl8]4− anion of (I) exhibits a new coordination geometry, although it has been studied as part of a larger Cd–Ni compound (Chesnut et al., 1999) which had terminal Cl atoms bonded to Ni atoms. Other dimeric Cd anions, such as [Cd2Cl6]2− (Bart et al., 1980), have been described, but the Cd atoms have distorted tetrahedral geometry. In some polymeric structures (Charles et al., 1984; Puget et al., 1991; Doudin & Chapuis, 1992), the Cd centre generally displays octahedral coordination.
In the crystal lattice of (I), there are hydrogen-bonding and π–π stacking interactions. There are both N—H···Cl and C—H···Cl interactions between the 2-(3-pyridinio)benzimidazolium cations and the dimeric [Cd2Cl8]4− anions (Table 2). The N—H···Cl interactions generate a sheet structure, as shown in Fig. 2. In addition, there are π–π stacking interactions between adjacent aromatic and pyridine rings, as shown in Fig. 3. The centroid···centroid separation of rings N11/C12–C16(x, y, z) and C4–C9(x, 1/2 − y, z − 1/2) is 3.592 (6) Å, and the shortest atom···atom separation is 3.345 (7) Å between atoms C14(x, y, z) and C8(x, 1/2 − y, z − 1/2). These interactions, and the C—H···Cl interactions involving atoms C12 and C16 (Table 2), serve to generate a three-dimensional network.