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In poly[di-μ-chlorido-μ-(4,4′-bipyridazine)-κ
2N1:
N1′-cadmium(II)], [CdCl
2(C
8H
6N
4)]
n, (I), and its isomorphous bromide analogue, [CdBr
2(C
8H
6N
4)]
n, (II), the halide atom lies on a mirror plane and the Cd
II ion resides at the intersection of two perpendicular mirror planes with
m2
m site symmetry. The pyridazine rings of the ligand lie in a mirror plane and are related to each other by a second mirror plane perpendicular to the first. The compounds adopt the characteristic structure of the [
MIIX2(bipy)] type (bipy is bipyridine) based on crosslinking of [Cd(μ-
X)
2]
n chains [Cd—Cl = 2.5955 (9) and 2.6688 (9) Å; Cd—Br = 2.7089 (4) and 2.8041 (3) Å] by bitopic rod-like organic ligands [Cd—N = 2.368 (3)–2.380 (3) Å]. This feature is discussed in terms of supramolecular stabilization, implying that the periodicity of the inorganic chain [Cd
Cd = 3.7802 (4) Å in (I) and 3.9432 (3) Å in (II)] is favourable for extensive parallel π–π stacking of monodentate pyridazine rings, with centroid–centroid distances of 3.7751 (4) Å in (I) and 3.9359 (4) Å in (II). This is not the case for the longer iodide bridges, which cannot stabilize such a pattern. In poly[tetra-μ-iodido-μ
4-(4,4′-bipyridazine)-κ
4N1:
N2:
N1′:
N2′-dicadmium(II)], [Cd
2I
4(C
8H
6N
4)]
n, (III), the ligands are situated across a centre of inversion; they are tetradentate [Cd—N = 2.488 (2) and 2.516 (2) Å] and link successive [Cd(μ-I)
2]
n chains [Cd—I = 2.8816 (3)–3.0069 (4) Å] into corrugated layers.
Supporting information
CCDC references: 914633; 914634; 914635
4,4'-Bipyridazine was prepared by cycloaddition of 1,2,4,5-tetrazine and
cis,trans-1,4-bis(dimethylamino)butadiene (Domasevitch,
Gural'skiy et al., 2007). The complexes were prepared under
similar
conditions reacting the components as follows. Solutions of CdCl2 (18.3 mg,
0.1 mmol) in water (2 ml) and 4,4'-bipyridazine (15.8 mg, 0.1 mmol) in water
(2 ml) were combined. The mixture was filtered and then allowed to evaporate
slowly for a period of 7–10 d, providing colourless prisms of (I) in a yield
of 29 mg (85%). The crystals were collected by filtration, washed with ethanol
and ether and dried in air. Starting with CdBr2.4H2O (34.4 mg, 0.1 mmol)
and 4,4'-bipyridazine (15.8 mg, 0.1 mmol), complex (II) was obtained as
colourless prisms in 70% yield. Similarly, reaction of CdI2 (73.2 mg, 0.2 mmol) and 4,4'-bipyridazine (15.8 mg, 0.1 mmol) led to large orange prisms of
(III) in 65% yield. In every case, variations in the metal-to-ligand ratios
did not affect the composition of the reaction product. For (I), elemental
analysis calculated: C 28.14, H 1.77, N 16.41%; found: C 28.33, H 1.62, N
16.20%. For (II), elemental analysis calculated: C 22.32, H 1.41, N 13.02%;
found: C 22.18, H 1.47, N 12.97%. For (III), elemental analysis calculated: C
10.79, H 0.68, N 6.29%; found: C 10.60, H 3/4, N 6.11%.
All H atoms were located from difference maps and then refined as riding, with
the angles constrained, C—H distances constrained to 0.94 Å, and with
Uiso(H) = 1.2Ueq(C).
For all compounds, data collection: IPDS Software (Stoe & Cie, 2000); cell refinement: IPDS Software (Stoe & Cie, 2000); data reduction: IPDS Software (Stoe & Cie, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999).
(I) Poly[di-µ-chlorido-µ-(4,4'-bipyridazine)-
κ2N1:
N1'-
cadmium(II)]
top
Crystal data top
[CdCl2(C8H6N4)] | Dx = 2.197 Mg m−3 |
Mr = 341.47 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Cmcm | Cell parameters from 3205 reflections |
a = 11.7374 (10) Å | θ = 2.5–28.1° |
b = 11.6511 (10) Å | µ = 2.60 mm−1 |
c = 7.5484 (8) Å | T = 223 K |
V = 1032.27 (17) Å3 | Prism, colorless |
Z = 4 | 0.19 × 0.15 × 0.14 mm |
F(000) = 656 | |
Data collection top
Stoe imaging-plate diffraction system diffractometer | 706 independent reflections |
Radiation source: fine-focus sealed tube | 625 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.038 |
ϕ oscillation scans | θmax = 28.1°, θmin = 2.5° |
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | h = −15→15 |
Tmin = 0.638, Tmax = 0.712 | k = −10→15 |
3205 measured reflections | l = −8→9 |
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)] = 0.029 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.073 | H-atom parameters constrained |
S = 1.01 | w = 1/[σ2(Fo2) + (0.0524P)2] where P = (Fo2 + 2Fc2)/3 |
706 reflections | (Δ/σ)max < 0.001 |
47 parameters | Δρmax = 1.22 e Å−3 |
0 restraints | Δρmin = −0.68 e Å−3 |
Crystal data top
[CdCl2(C8H6N4)] | V = 1032.27 (17) Å3 |
Mr = 341.47 | Z = 4 |
Orthorhombic, Cmcm | Mo Kα radiation |
a = 11.7374 (10) Å | µ = 2.60 mm−1 |
b = 11.6511 (10) Å | T = 223 K |
c = 7.5484 (8) Å | 0.19 × 0.15 × 0.14 mm |
Data collection top
Stoe imaging-plate diffraction system diffractometer | 706 independent reflections |
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | 625 reflections with I > 2σ(I) |
Tmin = 0.638, Tmax = 0.712 | Rint = 0.038 |
3205 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.073 | H-atom parameters constrained |
S = 1.01 | Δρmax = 1.22 e Å−3 |
706 reflections | Δρmin = −0.68 e Å−3 |
47 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 | 0.5000 | 0.49083 (3) | 0.2500 | 0.01733 (16) | |
Cl1 | 0.5000 | 0.34280 (7) | −0.00696 (11) | 0.0195 (2) | |
N1 | 0.7016 (3) | 0.4997 (2) | 0.2500 | 0.0206 (7) | |
N2 | 0.7607 (3) | 0.4016 (3) | 0.2500 | 0.0263 (7) | |
C1 | 0.7567 (3) | 0.5992 (3) | 0.2500 | 0.0226 (8) | |
H1 | 0.7138 | 0.6674 | 0.2500 | 0.027* | |
C2 | 0.8743 (3) | 0.6075 (3) | 0.2500 | 0.0254 (8) | |
H2 | 0.9106 | 0.6794 | 0.2500 | 0.031* | |
C3 | 0.9365 (3) | 0.5078 (3) | 0.2500 | 0.0169 (7) | |
C4 | 0.8740 (3) | 0.4059 (3) | 0.2500 | 0.0265 (9) | |
H4 | 0.9143 | 0.3362 | 0.2500 | 0.032* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.0122 (2) | 0.0209 (2) | 0.0188 (2) | 0.000 | 0.000 | 0.000 |
Cl1 | 0.0261 (5) | 0.0129 (5) | 0.0194 (5) | 0.000 | 0.000 | −0.0001 (3) |
N1 | 0.0136 (13) | 0.0161 (16) | 0.032 (2) | −0.0008 (9) | 0.000 | 0.000 |
N2 | 0.0216 (15) | 0.0195 (16) | 0.038 (2) | 0.0002 (12) | 0.000 | 0.000 |
C1 | 0.0200 (16) | 0.0198 (17) | 0.028 (2) | 0.0032 (13) | 0.000 | 0.000 |
C2 | 0.0216 (18) | 0.0230 (18) | 0.032 (2) | −0.0037 (14) | 0.000 | 0.000 |
C3 | 0.0132 (17) | 0.0222 (18) | 0.0152 (18) | 0.0002 (11) | 0.000 | 0.000 |
C4 | 0.0204 (17) | 0.0194 (17) | 0.040 (3) | 0.0011 (14) | 0.000 | 0.000 |
Geometric parameters (Å, º) top
Cd1—N1i | 2.368 (3) | N2—C4 | 1.330 (5) |
Cd1—N1 | 2.368 (3) | C1—C2 | 1.383 (5) |
Cd1—Cl1 | 2.5955 (9) | C1—H1 | 0.9400 |
Cd1—Cl1ii | 2.5955 (9) | C2—C3 | 1.372 (5) |
Cd1—Cl1iii | 2.6688 (9) | C2—H2 | 0.9400 |
Cd1—Cl1iv | 2.6688 (9) | C3—C4 | 1.395 (5) |
N1—C1 | 1.328 (5) | C3—C3v | 1.491 (7) |
N1—N2 | 1.337 (4) | C4—H4 | 0.9400 |
| | | |
N1i—Cd1—N1 | 174.99 (12) | C1—N1—N2 | 119.6 (4) |
N1i—Cd1—Cl1 | 91.66 (4) | C1—N1—Cd1 | 121.7 (2) |
N1—Cd1—Cl1 | 91.66 (4) | N2—N1—Cd1 | 118.8 (2) |
N1i—Cd1—Cl1ii | 91.66 (4) | C4—N2—N1 | 119.1 (3) |
N1—Cd1—Cl1ii | 91.66 (4) | N1—C1—C2 | 123.1 (4) |
N1—Cd1—Cl1iii | 88.18 (4) | N1—C1—H1 | 118.4 |
Cl1—Cd1—Cl1ii | 96.72 (4) | C2—C1—H1 | 118.4 |
N1i—Cd1—Cl1iii | 88.18 (5) | C3—C2—C1 | 118.2 (4) |
Cl1—Cd1—Cl1iii | 175.07 (3) | C3—C2—H2 | 120.9 |
Cl1ii—Cd1—Cl1iii | 88.22 (3) | C1—C2—H2 | 120.9 |
N1i—Cd1—Cl1iv | 88.18 (4) | C2—C3—C4 | 116.1 (3) |
N1—Cd1—Cl1iv | 88.18 (4) | C2—C3—C3v | 122.1 (2) |
Cl1—Cd1—Cl1iv | 88.22 (3) | C4—C3—C3v | 121.7 (2) |
Cl1ii—Cd1—Cl1iv | 175.07 (3) | N2—C4—C3 | 123.9 (4) |
Cl1iii—Cd1—Cl1iv | 86.85 (4) | N2—C4—H4 | 118.1 |
Cd1—Cl1—Cd1iv | 91.78 (3) | C3—C4—H4 | 118.1 |
| | | |
N1i—Cd1—Cl1—Cd1iv | 88.13 (5) | Cl1iv—Cd1—N1—N2 | −136.549 (19) |
N1—Cd1—Cl1—Cd1iv | −88.13 (5) | C1—N1—N2—C4 | 0.0 |
Cl1ii—Cd1—Cl1—Cd1iv | 180.0 | Cd1—N1—N2—C4 | 180.0 |
Cl1iv—Cd1—Cl1—Cd1iv | 0.0 | N2—N1—C1—C2 | 0.0 |
Cl1—Cd1—N1—C1 | 131.62 (2) | Cd1—N1—C1—C2 | 180.0 |
Cl1ii—Cd1—N1—C1 | −131.62 (2) | N1—C1—C2—C3 | 0.0 |
Cl1iii—Cd1—N1—C1 | −43.451 (19) | C1—C2—C3—C4 | 0.0 |
Cl1iv—Cd1—N1—C1 | 43.451 (19) | C1—C2—C3—C3v | 180.0 |
Cl1—Cd1—N1—N2 | −48.38 (2) | N1—N2—C4—C3 | 0.0 |
Cl1ii—Cd1—N1—N2 | 48.38 (2) | C2—C3—C4—N2 | 0.0 |
Cl1iii—Cd1—N1—N2 | 136.549 (19) | C3v—C3—C4—N2 | 180.0 |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) x, y, −z+1/2; (iii) −x+1, −y+1, z+1/2; (iv) −x+1, −y+1, −z; (v) −x+2, y, −z+1/2. |
(II) Poly[di-µ-bromido-µ-(4,4'-bipyridazine)-
κ2N1:
N1'-
cadmium(II)]
top
Crystal data top
[CdBr2(C8H6N4)] | Dx = 2.584 Mg m−3 |
Mr = 430.39 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Cmcm | Cell parameters from 5866 reflections |
a = 11.7549 (8) Å | θ = 2.4–28.5° |
b = 11.9619 (8) Å | µ = 9.17 mm−1 |
c = 7.8690 (6) Å | T = 223 K |
V = 1106.47 (14) Å3 | Prism, colorless |
Z = 4 | 0.19 × 0.15 × 0.15 mm |
F(000) = 800 | |
Data collection top
Stoe imaging-plate diffraction system diffractometer | 776 independent reflections |
Radiation source: fine-focus sealed tube | 722 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.044 |
ϕ oscillation scans | θmax = 28.5°, θmin = 2.4° |
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | h = −15→15 |
Tmin = 0.275, Tmax = 0.340 | k = −15→15 |
5866 measured reflections | l = −9→9 |
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)] = 0.024 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.062 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0474P)2] where P = (Fo2 + 2Fc2)/3 |
776 reflections | (Δ/σ)max = 0.001 |
47 parameters | Δρmax = 0.76 e Å−3 |
0 restraints | Δρmin = −0.93 e Å−3 |
Crystal data top
[CdBr2(C8H6N4)] | V = 1106.47 (14) Å3 |
Mr = 430.39 | Z = 4 |
Orthorhombic, Cmcm | Mo Kα radiation |
a = 11.7549 (8) Å | µ = 9.17 mm−1 |
b = 11.9619 (8) Å | T = 223 K |
c = 7.8690 (6) Å | 0.19 × 0.15 × 0.15 mm |
Data collection top
Stoe imaging-plate diffraction system diffractometer | 776 independent reflections |
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | 722 reflections with I > 2σ(I) |
Tmin = 0.275, Tmax = 0.340 | Rint = 0.044 |
5866 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.024 | 0 restraints |
wR(F2) = 0.062 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.76 e Å−3 |
776 reflections | Δρmin = −0.93 e Å−3 |
47 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 | 0.5000 | 0.48906 (2) | 0.2500 | 0.01521 (13) | |
Br1 | 0.5000 | 0.33898 (2) | −0.00780 (4) | 0.02267 (14) | |
N1 | 0.7021 (2) | 0.50009 (17) | 0.2500 | 0.0218 (6) | |
N2 | 0.7611 (2) | 0.4047 (2) | 0.2500 | 0.0312 (7) | |
C1 | 0.7570 (3) | 0.5969 (2) | 0.2500 | 0.0292 (8) | |
H1 | 0.7136 | 0.6630 | 0.2500 | 0.035* | |
C2 | 0.8738 (3) | 0.6065 (2) | 0.2500 | 0.0275 (7) | |
H2 | 0.9092 | 0.6769 | 0.2500 | 0.033* | |
C3 | 0.9377 (2) | 0.5090 (2) | 0.2500 | 0.0159 (6) | |
C4 | 0.8730 (3) | 0.4094 (2) | 0.2500 | 0.0309 (8) | |
H4 | 0.9129 | 0.3413 | 0.2500 | 0.037* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.00816 (18) | 0.01652 (17) | 0.0210 (2) | 0.000 | 0.000 | 0.000 |
Br1 | 0.0307 (3) | 0.01492 (18) | 0.0224 (2) | 0.000 | 0.000 | −0.00020 (9) |
N1 | 0.0086 (11) | 0.0187 (12) | 0.038 (2) | −0.0001 (7) | 0.000 | 0.000 |
N2 | 0.0150 (13) | 0.0192 (12) | 0.059 (2) | −0.0009 (9) | 0.000 | 0.000 |
C1 | 0.0157 (15) | 0.0197 (13) | 0.052 (2) | 0.0027 (11) | 0.000 | 0.000 |
C2 | 0.0132 (15) | 0.0179 (12) | 0.051 (2) | −0.0007 (10) | 0.000 | 0.000 |
C3 | 0.0097 (14) | 0.0176 (12) | 0.0205 (18) | 0.0000 (8) | 0.000 | 0.000 |
C4 | 0.0134 (15) | 0.0192 (13) | 0.060 (3) | −0.0002 (10) | 0.000 | 0.000 |
Geometric parameters (Å, º) top
Cd1—N1 | 2.380 (3) | N2—C4 | 1.316 (4) |
Cd1—N1i | 2.380 (3) | C1—C2 | 1.379 (4) |
Cd1—Br1 | 2.7089 (4) | C1—H1 | 0.9400 |
Cd1—Br1ii | 2.7089 (4) | C2—C3 | 1.386 (4) |
Cd1—Br1iii | 2.8041 (3) | C2—H2 | 0.9400 |
Cd1—Br1iv | 2.8041 (3) | C3—C4 | 1.413 (4) |
N1—C1 | 1.326 (4) | C3—C3v | 1.465 (6) |
N1—N2 | 1.335 (3) | C4—H4 | 0.9400 |
| | | |
N1—Cd1—N1i | 173.64 (10) | C1—N1—N2 | 119.6 (3) |
N1—Cd1—Br1 | 92.11 (3) | C1—N1—Cd1 | 122.3 (2) |
N1—Cd1—Br1ii | 92.11 (3) | N2—N1—Cd1 | 118.11 (18) |
N1—Cd1—Br1iii | 87.67 (4) | C4—N2—N1 | 118.8 (3) |
Br1—Cd1—Br1ii | 96.987 (17) | N1—C1—C2 | 123.8 (3) |
Br1—Cd1—Br1iv | 88.689 (10) | N1—C1—H1 | 118.1 |
Br1iii—Cd1—Br1iv | 85.635 (15) | C2—C1—H1 | 118.1 |
Br1—Cd1—Br1iii | 174.324 (13) | C1—C2—C3 | 118.0 (3) |
Cd1—Br1—Cd1iv | 91.311 (10) | C1—C2—H2 | 121.0 |
N1i—Cd1—Br1 | 92.11 (3) | C3—C2—H2 | 121.0 |
N1i—Cd1—Br1ii | 92.11 (3) | C2—C3—C4 | 114.7 (3) |
N1i—Cd1—Br1iii | 87.67 (4) | C2—C3—C3v | 122.77 (17) |
Br1ii—Cd1—Br1iii | 88.689 (10) | C4—C3—C3v | 122.53 (17) |
N1—Cd1—Br1iv | 87.67 (4) | N2—C4—C3 | 125.0 (3) |
N1i—Cd1—Br1iv | 87.67 (4) | N2—C4—H4 | 117.5 |
Br1ii—Cd1—Br1iv | 174.324 (13) | C3—C4—H4 | 117.5 |
| | | |
N1—Cd1—Br1—Cd1iv | −87.62 (4) | Br1iv—Cd1—N1—N2 | −137.139 (8) |
N1i—Cd1—Br1—Cd1iv | 87.62 (4) | C1—N1—N2—C4 | 0.0 |
Br1ii—Cd1—Br1—Cd1iv | 180.0 | Cd1—N1—N2—C4 | 180.0 |
Br1iv—Cd1—Br1—Cd1iv | 0.0 | N2—N1—C1—C2 | 0.0 |
Br1—Cd1—N1—C1 | 131.463 (9) | Cd1—N1—C1—C2 | 180.0 |
Br1ii—Cd1—N1—C1 | −131.463 (9) | N1—C1—C2—C3 | 0.0 |
Br1iii—Cd1—N1—C1 | −42.861 (8) | C1—C2—C3—C4 | 0.0 |
Br1iv—Cd1—N1—C1 | 42.861 (8) | C1—C2—C3—C3v | 180.0 |
Br1—Cd1—N1—N2 | −48.537 (9) | N1—N2—C4—C3 | 0.0 |
Br1ii—Cd1—N1—N2 | 48.537 (9) | C2—C3—C4—N2 | 0.0 |
Br1iii—Cd1—N1—N2 | 137.139 (8) | C3v—C3—C4—N2 | 180.0 |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) x, y, −z+1/2; (iii) −x+1, −y+1, z+1/2; (iv) −x+1, −y+1, −z; (v) −x+2, y, −z+1/2. |
(III) Poly[[tetra-µ-iodido-µ
4-(4,4'-bipyridazine)-
κ4N1:
N2:
N1':
N2'-dicadmium(II)]
top
Crystal data top
[Cd2I4(C8H6N4)] | F(000) = 780 |
Mr = 890.57 | Dx = 3.717 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 8.0106 (6) Å | Cell parameters from 7188 reflections |
b = 14.3621 (13) Å | θ = 2.8–28.1° |
c = 7.6850 (6) Å | µ = 10.42 mm−1 |
β = 115.855 (8)° | T = 223 K |
V = 795.65 (11) Å3 | Prism, yellow |
Z = 2 | 0.19 × 0.17 × 0.14 mm |
Data collection top
Stoe imaging-plate diffraction system diffractometer | 1913 independent reflections |
Radiation source: fine-focus sealed tube | 1768 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.037 |
ϕ oscillation scans | θmax = 28.1°, θmin = 2.8° |
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | h = −10→9 |
Tmin = 0.242, Tmax = 0.323 | k = −19→19 |
7188 measured reflections | l = −10→10 |
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)] = 0.017 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.040 | H-atom parameters constrained |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0207P)2 + 0.2521P] where P = (Fo2 + 2Fc2)/3 |
1913 reflections | (Δ/σ)max < 0.001 |
82 parameters | Δρmax = 0.64 e Å−3 |
0 restraints | Δρmin = −0.76 e Å−3 |
Crystal data top
[Cd2I4(C8H6N4)] | V = 795.65 (11) Å3 |
Mr = 890.57 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 8.0106 (6) Å | µ = 10.42 mm−1 |
b = 14.3621 (13) Å | T = 223 K |
c = 7.6850 (6) Å | 0.19 × 0.17 × 0.14 mm |
β = 115.855 (8)° | |
Data collection top
Stoe imaging-plate diffraction system diffractometer | 1913 independent reflections |
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | 1768 reflections with I > 2σ(I) |
Tmin = 0.242, Tmax = 0.323 | Rint = 0.037 |
7188 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.017 | 0 restraints |
wR(F2) = 0.040 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.64 e Å−3 |
1913 reflections | Δρmin = −0.76 e Å−3 |
82 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 | −0.02645 (3) | 0.237346 (13) | 0.08695 (3) | 0.01730 (6) | |
I1 | −0.00055 (3) | 0.400707 (11) | 0.32771 (3) | 0.01966 (6) | |
I2 | −0.27868 (3) | 0.157754 (13) | 0.23005 (3) | 0.02287 (6) | |
N1 | 0.2386 (3) | 0.18598 (15) | 0.5499 (3) | 0.0176 (5) | |
N2 | 0.2208 (3) | 0.16096 (14) | 0.3743 (4) | 0.0166 (4) | |
C1 | 0.3685 (4) | 0.14507 (18) | 0.7044 (4) | 0.0193 (5) | |
H1 | 0.3874 | 0.1668 | 0.8270 | 0.023* | |
C2 | 0.4787 (4) | 0.07162 (19) | 0.6957 (4) | 0.0193 (5) | |
H2 | 0.5686 | 0.0442 | 0.8088 | 0.023* | |
C3 | 0.4510 (3) | 0.04078 (16) | 0.5152 (4) | 0.0145 (5) | |
C4 | 0.3221 (4) | 0.09249 (17) | 0.3565 (4) | 0.0163 (5) | |
H4 | 0.3080 | 0.0772 | 0.2319 | 0.020* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cd1 | 0.01750 (10) | 0.01931 (10) | 0.01509 (11) | 0.00017 (7) | 0.00713 (9) | 0.00004 (7) |
I1 | 0.02479 (10) | 0.01583 (9) | 0.01814 (10) | 0.00161 (6) | 0.00917 (8) | −0.00002 (6) |
I2 | 0.02011 (10) | 0.02977 (10) | 0.01844 (10) | −0.00869 (7) | 0.00815 (8) | −0.00332 (6) |
N1 | 0.0157 (10) | 0.0168 (10) | 0.0175 (11) | 0.0029 (8) | 0.0046 (9) | 0.0003 (8) |
N2 | 0.0153 (11) | 0.0169 (9) | 0.0173 (11) | 0.0015 (8) | 0.0069 (9) | 0.0015 (8) |
C1 | 0.0168 (13) | 0.0224 (12) | 0.0146 (13) | 0.0031 (10) | 0.0032 (11) | −0.0030 (10) |
C2 | 0.0142 (12) | 0.0218 (12) | 0.0175 (13) | 0.0036 (10) | 0.0030 (11) | 0.0016 (10) |
C3 | 0.0125 (11) | 0.0134 (10) | 0.0166 (12) | 0.0007 (9) | 0.0055 (10) | 0.0021 (9) |
C4 | 0.0140 (12) | 0.0202 (12) | 0.0137 (12) | 0.0024 (9) | 0.0052 (11) | 0.0010 (9) |
Geometric parameters (Å, º) top
Cd1—N1i | 2.516 (2) | N2—C4 | 1.319 (3) |
Cd1—N2 | 2.488 (2) | C1—C2 | 1.396 (4) |
Cd1—I1i | 2.8816 (3) | C1—H1 | 0.9400 |
Cd1—I1 | 2.9388 (3) | C2—C3 | 1.378 (4) |
Cd1—I2 | 2.9217 (3) | C2—H2 | 0.9400 |
Cd1—I2i | 3.0069 (4) | C3—C4 | 1.417 (3) |
N1—C1 | 1.327 (4) | C3—C3ii | 1.484 (5) |
N1—N2 | 1.343 (4) | C4—H4 | 0.9400 |
| | | |
N2—Cd1—N1i | 84.78 (8) | C1—N1—Cd1iii | 117.61 (19) |
N1i—Cd1—I1 | 83.71 (5) | N2—N1—Cd1iii | 120.42 (16) |
N1i—Cd1—I1i | 84.50 (5) | C4—N2—N1 | 120.2 (2) |
N1i—Cd1—I2 | 165.97 (6) | C4—N2—Cd1 | 121.62 (19) |
N1i—Cd1—I2i | 86.67 (5) | N1—N2—Cd1 | 117.93 (16) |
N2—Cd1—I1 | 89.02 (5) | N1—C1—C2 | 123.8 (3) |
N2—Cd1—I1i | 92.34 (5) | N1—C1—H1 | 118.1 |
N2—Cd1—I2 | 84.66 (6) | C2—C1—H1 | 118.1 |
N2—Cd1—I2i | 171.43 (6) | C3—C2—C1 | 117.6 (2) |
I1i—Cd1—I1 | 167.960 (10) | C3—C2—H2 | 121.2 |
I1i—Cd1—I2 | 105.137 (10) | C1—C2—H2 | 121.2 |
I1—Cd1—I2 | 86.900 (9) | C2—C3—C4 | 115.8 (2) |
I1i—Cd1—I2i | 86.356 (10) | C2—C3—C3ii | 123.2 (3) |
I1—Cd1—I2i | 90.524 (10) | C4—C3—C3ii | 121.0 (3) |
I2—Cd1—I2i | 103.856 (11) | N2—C4—C3 | 123.5 (3) |
Cd1iii—I1—Cd1 | 83.071 (8) | N2—C4—H4 | 118.3 |
Cd1—I2—Cd1iii | 81.223 (8) | C3—C4—H4 | 118.3 |
C1—N1—N2 | 118.6 (2) | | |
| | | |
N2—Cd1—I1—Cd1iii | −49.12 (6) | I2—Cd1—N2—C4 | 114.6 (2) |
N1i—Cd1—I1—Cd1iii | −133.97 (5) | I1—Cd1—N2—C4 | −158.4 (2) |
I1i—Cd1—I1—Cd1iii | −145.74 (4) | N1i—Cd1—N2—N1 | 110.95 (16) |
I2—Cd1—I1—Cd1iii | 35.593 (9) | I1i—Cd1—N2—N1 | −164.80 (17) |
I2i—Cd1—I1—Cd1iii | 139.441 (6) | I2—Cd1—N2—N1 | −59.81 (17) |
N2—Cd1—I2—Cd1iii | 55.23 (5) | I1—Cd1—N2—N1 | 27.17 (17) |
N1i—Cd1—I2—Cd1iii | 13.9 (2) | N2—N1—C1—C2 | −5.6 (4) |
I1i—Cd1—I2—Cd1iii | 146.214 (7) | Cd1iii—N1—C1—C2 | 153.9 (2) |
I1—Cd1—I2—Cd1iii | −34.074 (7) | N1—C1—C2—C3 | 0.5 (4) |
I2i—Cd1—I2—Cd1iii | −123.849 (12) | C1—C2—C3—C4 | 4.8 (4) |
C1—N1—N2—C4 | 4.7 (4) | C1—C2—C3—C3ii | −175.6 (3) |
Cd1iii—N1—N2—C4 | −154.15 (19) | N1—N2—C4—C3 | 1.0 (4) |
C1—N1—N2—Cd1 | 179.24 (19) | Cd1—N2—C4—C3 | −173.35 (19) |
Cd1iii—N1—N2—Cd1 | 20.4 (2) | C2—C3—C4—N2 | −5.8 (4) |
N1i—Cd1—N2—C4 | −74.6 (2) | C3ii—C3—C4—N2 | 174.6 (3) |
I1i—Cd1—N2—C4 | 9.7 (2) | | |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, −y, −z+1; (iii) x, −y+1/2, z+1/2. |
Experimental details
| (I) | (II) | (III) |
Crystal data |
Chemical formula | [CdCl2(C8H6N4)] | [CdBr2(C8H6N4)] | [Cd2I4(C8H6N4)] |
Mr | 341.47 | 430.39 | 890.57 |
Crystal system, space group | Orthorhombic, Cmcm | Orthorhombic, Cmcm | Monoclinic, P21/c |
Temperature (K) | 223 | 223 | 223 |
a, b, c (Å) | 11.7374 (10), 11.6511 (10), 7.5484 (8) | 11.7549 (8), 11.9619 (8), 7.8690 (6) | 8.0106 (6), 14.3621 (13), 7.6850 (6) |
α, β, γ (°) | 90, 90, 90 | 90, 90, 90 | 90, 115.855 (8), 90 |
V (Å3) | 1032.27 (17) | 1106.47 (14) | 795.65 (11) |
Z | 4 | 4 | 2 |
Radiation type | Mo Kα | Mo Kα | Mo Kα |
µ (mm−1) | 2.60 | 9.17 | 10.42 |
Crystal size (mm) | 0.19 × 0.15 × 0.14 | 0.19 × 0.15 × 0.15 | 0.19 × 0.17 × 0.14 |
|
Data collection |
Diffractometer | Stoe imaging-plate diffraction system diffractometer | Stoe imaging-plate diffraction system diffractometer | Stoe imaging-plate diffraction system diffractometer |
Absorption correction | Numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | Numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] | Numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)] |
Tmin, Tmax | 0.638, 0.712 | 0.275, 0.340 | 0.242, 0.323 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3205, 706, 625 | 5866, 776, 722 | 7188, 1913, 1768 |
Rint | 0.038 | 0.044 | 0.037 |
(sin θ/λ)max (Å−1) | 0.663 | 0.671 | 0.662 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.073, 1.01 | 0.024, 0.062, 1.02 | 0.017, 0.040, 1.10 |
No. of reflections | 706 | 776 | 1913 |
No. of parameters | 47 | 47 | 82 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 1.22, −0.68 | 0.76, −0.93 | 0.64, −0.76 |
Selected geometric parameters (Å, º) for (I) topCd1—N1 | 2.368 (3) | Cd1—Cl1i | 2.6688 (9) |
Cd1—Cl1 | 2.5955 (9) | | |
| | | |
N1ii—Cd1—N1 | 174.99 (12) | Cl1—Cd1—Cl1i | 175.07 (3) |
N1—Cd1—Cl1 | 91.66 (4) | Cl1—Cd1—Cl1iv | 88.22 (3) |
N1—Cd1—Cl1i | 88.18 (4) | Cl1i—Cd1—Cl1iv | 86.85 (4) |
Cl1—Cd1—Cl1iii | 96.72 (4) | Cd1—Cl1—Cd1iv | 91.78 (3) |
Symmetry codes: (i) −x+1, −y+1, z+1/2; (ii) −x+1, y, −z+1/2; (iii) x, y, −z+1/2; (iv) −x+1, −y+1, −z. |
Selected geometric parameters (Å, º) for (II) topCd1—N1 | 2.380 (3) | Cd1—Br1i | 2.8041 (3) |
Cd1—Br1 | 2.7089 (4) | | |
| | | |
N1—Cd1—N1ii | 173.64 (10) | Br1—Cd1—Br1iv | 88.689 (10) |
N1—Cd1—Br1 | 92.11 (3) | Br1i—Cd1—Br1iv | 85.635 (15) |
N1—Cd1—Br1i | 87.67 (4) | Br1—Cd1—Br1i | 174.324 (13) |
Br1—Cd1—Br1iii | 96.987 (17) | Cd1—Br1—Cd1iv | 91.311 (10) |
Symmetry codes: (i) −x+1, −y+1, z+1/2; (ii) −x+1, y, −z+1/2; (iii) x, y, −z+1/2; (iv) −x+1, −y+1, −z. |
Summary of the ligand–[Cd(µ-X)2]n strand interactions for
isomorphous complexes (I) and (II) and isotypic bipyridine compounds
(Å, °). topCompound | C···X (Å) | H···X (Å) | C–H···X (°) | N···X (Å) | C—N—Cd—X (Å) |
[CdCl2(bpdz)]a | 3.592 (3) | 3.11 | 114 | 3.687 (3) | 43.45 (2) |
[CdBr2(bpdz)]a | 3.653 (3) | 3.15 | 115 | 3.762 (2) | 42.86 (2) |
| | | | | |
[CdCl2(bipy)]b | 3.492 (2) | 2.84 | 124 | | 28.36 (2) |
[CdBr2(bipy)]b | 3.591 (3) | 2.91 | 124 | | 30.81 (3) |
[CdI2(bipy)]b | 3.829 (2) | 3.30 | 115 | | 44.25 (3) |
Notes: (a) this work; (b) Hu et al. (2003). |
Selected geometric parameters (Å, º) for (III) topCd1—N1i | 2.516 (2) | Cd1—I1 | 2.9388 (3) |
Cd1—N2 | 2.488 (2) | Cd1—I2 | 2.9217 (3) |
Cd1—I1i | 2.8816 (3) | Cd1—I2i | 3.0069 (4) |
| | | |
N2—Cd1—N1i | 84.78 (8) | I1i—Cd1—I2 | 105.137 (10) |
N1i—Cd1—I2 | 165.97 (6) | I1—Cd1—I2 | 86.900 (9) |
N2—Cd1—I1 | 89.02 (5) | I1—Cd1—I2i | 90.524 (10) |
N2—Cd1—I1i | 92.34 (5) | I2—Cd1—I2i | 103.856 (11) |
N2—Cd1—I2 | 84.66 (6) | Cd1ii—I1—Cd1 | 83.071 (8) |
N2—Cd1—I2i | 171.43 (6) | Cd1—I2—Cd1ii | 81.223 (8) |
I1i—Cd1—I1 | 167.960 (10) | | |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) x, −y+1/2, z+1/2. |
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The role of pyridazine as a powerful bidentate bridging ligand towards CuI and AgI ions may be rationalized in terms of strong back-bonding (Munakata et al., 1999). In the case of ZnII and CdII ions, the lack of such stabilization mitigates against double coordination of this electron-deficient and low-basic (pKa = 2.24 for pyridazine versus pKa = 5.25 for pyridine) heterocycle, making the metal–pyridazine (pdz) system very flexible and sensitive to a range of additional factors such as the interplay with a suitable bridging co-ligand, weak C—H···X hydrogen bonding and π–π stacking. This implies a versatile structural role for pyridazine, either as a 1,2-diazine bridge or as a singly coordinated pyridine-like donor, and allows the evaluation of subtle supramolecular forces stabilizing one coordination pattern over the other. In this context, we examined the structurally simple and illustrative tecton 4,4'-bipyridazine (bpdz) as a potentially tetradentate ligand towards CdII chloride, bromide and iodide. The compatibility of pyridazine and halogenide bridges is a particular issue for cadmium coordination polymers [CdX2(pdz)] (X = Cl, Br), which comprise octahedral CdII ions, and organic and double halogenide links (Pazderski et al., 2004). However, the effects of supramolecular stabilization could be prevalent for large polyaromatic molecules. Therefore, beyond the very characteristic series of bidentate pyridazines which bridge CuI and AgI (Domasevitch, Solntsev et al., 2007), the coordination behaviour of the unsubstituted pyridazine itself may be less applicable to polytopic ligands combining multiple pyridazine functions. In this way, 4,4'-bipyridazine revealed a dual role as a tetradentate bis-pyridazine ligand in combination with additional short-distance bridges (halogenide and hydroxide) and as a simple N1,N1'-bitopic rod-like connector similar to 4,4'-bipyridine (Domasevitch, Gural'skiy et al., 2007). Herein, we report the structures of [CdCl2(bpdz)]n, (I), [CdBr2(bpdz)]n, (II), and [Cd2I4(bpdz)]n, (III), which display a clear structural response upon changes in the chemical composition of the halide bridges.
Compounds (I) and (II) are isomorphous and belong to the stucture type [MIIX2(bipy)] (MII = Zn, Cd, Hg, Pb, Ni, Mn, Fe; Englert, 2010). The Cl1 atom [Br1 in (II)] lies on a mirror plane (site symmetry m) and the Cd1 atom resides on an intersection of two perpendicular mirror planes (site symmetry m2m). The site symmetry of the organic ligand is also m2m, with the atoms of the pyridazine ring lying in a mirror plane and the two pyridazine halves of the molecule related by a mirror plane perpendicular to the first plane (Fig. 1). The crystal symmetry (Cmcm) is close to that for the [CdI2(bipy)] structure (Cmmm), which represents the aristotype of the above family commonly crystallizing in Pban (Hu et al., 2003).
The inorganic subconnectivity exists in the form of linear ribbons [CdX2]n along the c axis, formed by coplanar Cd2X2 squares sharing the Cd vertices (Tables 1 and 2). The organic ligands are coordinated in axial positions of the CdII ions and connect successive inorganic ribbons as simple linear rod-like bridges (Fig. 2), similar to the prototypical 4,4'-bipyridine ligand (Fig. 2). This leads to the extension of the array in a second dimension along the a axis, giving rise to two-dimensional coordination layers parallel to the ac plane. The Cd—N bond lengths are slightly longer then those observed for [CdX2(bipy)] [2.368 (3) and 2.344 (4) Å for X = Cl; 2.380 (3) and 2.363 (7) Å for X = Br; Hu et al., 2003]. This may be indicative of the lower donor ability of pyridazine. The entire structure is generated with extensive weak hydrogen bonding between successive layers, which includes bonds to noncoordinated N atoms [C1—H1···N2vi: C1···N2vi = 3.529 (6) and 3.687 (4) Å for (I) and (II), respectively, and C1—H1···N2vi = 141° for both structures; symmetry code: (vi) -x + 3/2, y + 1/2, -z + 1/2] and a set of C—H···Cl(Br) hydrogen bonds with corresponding C···X separations of 3.668 (3) and 3.735 (4) Å for X = Cl, and 3.749 (3) and 3.833 (3) Å for X = Br, with angles at the H atoms of 137–141° (Fig. 3).
The structure of the corresponding iodide, viz. [Cd2I4(bpdz)], (III), is completely different. The ligand resides on a centre of inversion and is coordinated in a tetradentate fashion (Fig. 4). The Cd1 ions adopt a distorted cis-octahedral geometry (CdN2I4), with rather long Cd—N bond lengths (Table 3), unprecedented for complexes with nonchelating ligands. The Cd—I distances agree with the parameters for a comparable cis-octahedral cadmium iodide complex with pyrazine-2-carboxylic acid, also incorporating [Cd(µ-I)2]n chains [Cd—I = 2.827 (3)–3.012 (2) Å; Ciurtin et al., 2003]. The combination of pyridazine and double iodide bridges provides connection of CdII ions into one-dimensional chains along the c axis (Fig. 5), while the organic ligands link these chains into puckered layers parallel to the bc plane (Fig. 6). The supramolecular interactions in (III) include very weak C—H···I hydrogen bonds, one of which is found within the [Cd(µ-I)2(µ-pyridazine)]n strand [C4···I1iv = 3.748 (3) Å and C4—H4···I1iv = 135°; symmetry code: (iv) x, -y + 1/2, z - 1/2] and the second between successive coordination layers [C1···I2v = 3.792 (3) Å and C1—H1···I1v = 133°; symmetry code: (v) x + 1, y, z + 1] (Fig. 6).
Thus, in (III), the ligand acts as a tetradentate double pyridazine donor, whereas for (I) and (II) its functionality is lower and parallels the behaviour of the rod-like 4,4'-bipyridine connector. In this sense, both the chloride and bromide but not the iodide structures correspond to the [MIIX2(bipy)] archetype raising interest towards discussion of weaker supramolecular interactions, such as π–π heteroaryl ring stacking and C—H···X hydrogen bonding.
The significance of the π–π stacking as a stabilizing factor for [CdX2(bipy)] decreases from chloride to iodide, providing a progressive increase of the Cd···Cd distances along the inorganic [CdX2]n chain (Hu et al., 2003). In (I), the relatively short chloride bridges facilitate parallel disposition of the coordinated pyridazines, with a centroid–centroid distance of 3.775 (3) Å. This parameter itself is most favourable for parallel π–π stacking of pyridazine rings in crystal structures, which occurs within the range of centroid–centroid distances of ca 3.50–3.95 Å (distribution median = 3.78 Å; Allen, 2002). For the bromide analogue (II), this separation is longer [3.936 (3) Å], but an even less favourable geometry could be anticipated in the case of iodide (III); a translation period of more than 4.1 Å is too long to maintain efficient stacking of pyridazine rings. Although [CdI2(bipy)] [Cd···Cd = 4.142(s.u.?) Å] has a similar structure to the chloride and bromide analogues, the lack of π–π stacking stabilization is responsible for disintegration of the related polymeric [CdX2(L)2]n array (X = Cl, Br, I; L = pyridine) in the case of iodide and unsubstituted pyridine, 3-methylpyridine or 3,5-dimethylpyridine (Hu et al., 2003).
For [CdX2(bipy)] (X = Cl, Br), the relative orientation of the heterocyclic ring towards the cadmium–halide [CdX2]n scaffold is indicative for double intrastrand interactions C—H···X (with two ortho-CH groups of the pyridine ring), which are attractive and stabilizing (Wang et al., 2009). This is not the case for the series [CdX2(bpdz)] (X = Cl, Br) because an analogous orientation of the pyridazine ring could generate an unfavourable N2···X contact instead. For (I) and (II), a certain repulsive character for the ligand/scaffold interaction is indicated by the torsion angles C1—N1—Cd1—X1 (Table 4), corresponding to a most distal disposition of the ortho-CH/N and pairs of cis-halogenide atoms. A similar configuration in [CdI2(bipy)] (Hu et al., 2003) agrees with the weakness of potential C—H···I interactions (Desiraju & Steiner, 1999). The N1—Cd—N1i bond angles [symmetry code: (i) -x + 1, y, -z + 1/2] also suggest an N2···X repulsion, which is somewhat more appreciable for (II) [174.99 (12)° for (I) and 173.64 (10)° for (II)], but may became even stronger for the corresponding iodide derivative.
When compared with the 4,4'-bipyridine complexes (Englert, 2010), the range of existence for [MIIX2(bipy)]-like structures with the 4,4'-bipyridazine ligand is possibly narrower due to the lack of specific stabilizing supramolecular interactions. Being still reliable for complexes (I) and (II), these interactions are unable to maintain a similar packing pattern in the case of iodide (III) which adopts its own structure featuring a combination of organic and double inorganic bridges.
In brief, the structures of iodide (III) and the related chloride and bromide complexes of the parent pyridazine [CdX2(pdz)] (Pazderski et al., 2004) suggest the compatibility of 1,2-diazine and all kinds of halide bridges (Cl to I) between the CdII ions. However, this is not the only relevant factor for the present system, which is also influenced by supramolecular forces coming from complementary hydrogen bonding and π–π stacking interactions. In the case of the chloride- and bromide-bridged motifs in structures (I) and (II), the latter interactions are important and prevent co-bridging of the pyridazine groups. The ease of structural reorganization when combining terminal or bridging halide and pyridazine donors suggests chemical flexibility of the [MIIX2(bpdz)] system and its wider structural potential in view of supramolecular isomerism.