Cadmium(II) chloride, bromide and iodide complexes with 4,4′-bipyrid­azine: when are diazine and halide bridges (in)compatible?

In poly[di-μ-chlorido-μ-(4,4′-bipyridazine)-κ²N¹:N^1′-cad­mium(II)], [CdCl₂(C₈H₆N₄)]_n, (I), and its isomorphous bromide analogue, [CdBr₂(C₈H₆N₄)]_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 m2m 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 [M^IIX₂(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-μ₄-(4,4′-bipyridazine)-κ⁴N¹:N²:N^1′:N^2′-di­cadmium(II)], [Cd₂I₄(C₈H₆N₄)]_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.

S1. Comment

The role of pyridazine as a powerful bidentate bridging ligand towards Cu^I and Ag^I ions may be rationalized in terms of strong back-bonding (Munakata et al., 1999). In the case of Zn^II and Cd^II ions, the lack of such stabilization mitigates against double coordination of this electron-deficient and low-basic (pK_a = 2.24 for pyridazine versus pK_a = 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 Cd^II 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 Cd^II 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 Cu^I and Ag^I (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,N^1'-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 [M^IIX₂(bipy)] (M^II = 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 Cd^II 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···N2^vi: C1···N2^vi = 3.529 (6) and 3.687 (4) Å for (I) and (II), respectively, and C1—H1···N2^vi = 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 Cd^II 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···I1^iv = 3.748 (3) Å and C4—H4···I1^iv = 135°; symmetry code: (iv) x, -y + 1/2, z - 1/2] and the second between successive coordination layers [C1···I2^v = 3.792 (3) Å and C1—H1···I1^v = 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 [M^IIX₂(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 [M^IIX₂(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 Cd^II 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 [M^IIX₂(bpdz)] system and its wider structural potential in view of supramolecular isomerism.

Related literature

For related literature, see: Allen (2002); Ciurtin et al. (2003); Desiraju & Steiner (1999); Domasevitch, Gural'skiy, Solntsev, Rusanov, Krautscheid, Howard & Chernega (2007); Domasevitch, Solntsev, Gural'skiy, Krautscheid, Rusanov, Chernega & Howard (2007); Englert (2010); Hu et al. (2003); Munakata et al. (1999); Pazderski et al. (2004); Wang et al. (2009).

S2. Experimental

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%.

S3. Refinement

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 U_iso(H) = 1.2U_eq(C).

Computing details

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).

Figures

	Fig. 1. The structure of (I), showing the atom-labelling scheme [which is identical for the isomorphous bromido complex (II), with Br1 atom instead of Cl1]. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. [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.]
	Fig. 2. Crosslinking of the [Cd(µ-Cl)2]n chains by bitopic rod-like bpdz bridges with generation of coordination layers. [Symmetry code: (i) -x + 1, y, -z + 1/2.]
	Fig. 3. A projection of the structure of (I) on the ab plane, showing the packing mode for the successive coordination layers with a set of weak C—H···N and C—H···Cl hydrogen bonds. The inorganic [Cd(µ-Cl)2]n chains are orthogonal to the plane of the figure. [Symmetry codes: (i) -x + 1, y, -z + 1/2; (iii) -x + 1, -y + 1, z + 1/2; (vi) -x + 3/2, y + 1/2, -z + 1/2; (vii) -x + 3/2, -y + 1/2, z + 1/2.]
	Fig. 4. The structure of (III), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Note the combination of the pyridazine and double iodide bridges between the Cd^II ions. [Symmetry codes: (i) x, -y + 1/2, z - 1/2; (ii) x, -y + 1/2, z + 1/2; (iii) -x + 1, -y, -z + 1.]
	Fig. 5. A projection of the structure of (III) on the bc plane, showing the accommodation of the tetradentate organic ligands at the [Cd(µ-I)2]n chains with generation of a corrugated layer. H atoms have been omitted for clarity and N atoms are shaded grey. [Symmetry codes: (i) x, -y + 1/2, z - 1/2; (ii) x, -y + 1/2, z + 1/2.]
	Fig. 6. The packing of the coordination layers in (III) (projection on the ab plane). H atoms have been omitted for clarity and dotted lines indicate weak C—H···I hydrogen bonds which are observed within the coordination strand [Cd(µ-I)2(µ-bpdz)]n, as well as between the layers. [Symmetry codes: (iv) x, -y + 1/2, z - 1/2; (v) x + 1, y, z + 1.]

(I) Poly[di-µ-chlorido-µ-(4,4'-bipyridazine)-κ²N¹:N^1'- cadmium(II)]

Crystal data

[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) Å^3	Prism, colorless
Z = 4	0.19 × 0.15 × 0.14 mm
F(000) = 656

Data collection

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

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)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.073	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0524P)^2] where P = (Fo^2 + 2Fc^2)/3
706 reflections	(Δ/σ)max < 0.001
47 parameters	Δρmax = 1.22 e Å^−3
0 restraints	Δρmin = −0.68 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
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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

Cd1—N1^i	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—Cl1^ii	2.5955 (9)	C2—C3	1.372 (5)
Cd1—Cl1^iii	2.6688 (9)	C2—H2	0.9400
Cd1—Cl1^iv	2.6688 (9)	C3—C4	1.395 (5)
N1—C1	1.328 (5)	C3—C3^v	1.491 (7)
N1—N2	1.337 (4)	C4—H4	0.9400
N1^i—Cd1—N1	174.99 (12)	C1—N1—N2	119.6 (4)
N1^i—Cd1—Cl1	91.66 (4)	C1—N1—Cd1	121.7 (2)
N1—Cd1—Cl1	91.66 (4)	N2—N1—Cd1	118.8 (2)
N1^i—Cd1—Cl1^ii	91.66 (4)	C4—N2—N1	119.1 (3)
N1—Cd1—Cl1^ii	91.66 (4)	N1—C1—C2	123.1 (4)
N1—Cd1—Cl1^iii	88.18 (4)	N1—C1—H1	118.4
Cl1—Cd1—Cl1^ii	96.72 (4)	C2—C1—H1	118.4
N1^i—Cd1—Cl1^iii	88.18 (5)	C3—C2—C1	118.2 (4)
Cl1—Cd1—Cl1^iii	175.07 (3)	C3—C2—H2	120.9
Cl1^ii—Cd1—Cl1^iii	88.22 (3)	C1—C2—H2	120.9
N1^i—Cd1—Cl1^iv	88.18 (4)	C2—C3—C4	116.1 (3)
N1—Cd1—Cl1^iv	88.18 (4)	C2—C3—C3^v	122.1 (2)
Cl1—Cd1—Cl1^iv	88.22 (3)	C4—C3—C3^v	121.7 (2)
Cl1^ii—Cd1—Cl1^iv	175.07 (3)	N2—C4—C3	123.9 (4)
Cl1^iii—Cd1—Cl1^iv	86.85 (4)	N2—C4—H4	118.1
Cd1—Cl1—Cd1^iv	91.78 (3)	C3—C4—H4	118.1
N1^i—Cd1—Cl1—Cd1^iv	88.13 (5)	Cl1^iv—Cd1—N1—N2	−136.549 (19)
N1—Cd1—Cl1—Cd1^iv	−88.13 (5)	C1—N1—N2—C4	0.0
Cl1^ii—Cd1—Cl1—Cd1^iv	180.0	Cd1—N1—N2—C4	180.0
Cl1^iv—Cd1—Cl1—Cd1^iv	0.0	N2—N1—C1—C2	0.0
Cl1—Cd1—N1—C1	131.62 (2)	Cd1—N1—C1—C2	180.0
Cl1^ii—Cd1—N1—C1	−131.62 (2)	N1—C1—C2—C3	0.0
Cl1^iii—Cd1—N1—C1	−43.451 (19)	C1—C2—C3—C4	0.0
Cl1^iv—Cd1—N1—C1	43.451 (19)	C1—C2—C3—C3^v	180.0
Cl1—Cd1—N1—N2	−48.38 (2)	N1—N2—C4—C3	0.0
Cl1^ii—Cd1—N1—N2	48.38 (2)	C2—C3—C4—N2	0.0
Cl1^iii—Cd1—N1—N2	136.549 (19)	C3^v—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:N^1'- cadmium(II)]

Crystal data

[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) Å^3	Prism, colorless
Z = 4	0.19 × 0.15 × 0.15 mm
F(000) = 800

Data collection

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

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)] = 0.024	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.062	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0474P)^2] where P = (Fo^2 + 2Fc^2)/3
776 reflections	(Δ/σ)max = 0.001
47 parameters	Δρmax = 0.76 e Å^−3
0 restraints	Δρmin = −0.93 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
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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

Cd1—N1	2.380 (3)	N2—C4	1.316 (4)
Cd1—N1^i	2.380 (3)	C1—C2	1.379 (4)
Cd1—Br1	2.7089 (4)	C1—H1	0.9400
Cd1—Br1^ii	2.7089 (4)	C2—C3	1.386 (4)
Cd1—Br1^iii	2.8041 (3)	C2—H2	0.9400
Cd1—Br1^iv	2.8041 (3)	C3—C4	1.413 (4)
N1—C1	1.326 (4)	C3—C3^v	1.465 (6)
N1—N2	1.335 (3)	C4—H4	0.9400
N1—Cd1—N1^i	173.64 (10)	C1—N1—N2	119.6 (3)
N1—Cd1—Br1	92.11 (3)	C1—N1—Cd1	122.3 (2)
N1—Cd1—Br1^ii	92.11 (3)	N2—N1—Cd1	118.11 (18)
N1—Cd1—Br1^iii	87.67 (4)	C4—N2—N1	118.8 (3)
Br1—Cd1—Br1^ii	96.987 (17)	N1—C1—C2	123.8 (3)
Br1—Cd1—Br1^iv	88.689 (10)	N1—C1—H1	118.1
Br1^iii—Cd1—Br1^iv	85.635 (15)	C2—C1—H1	118.1
Br1—Cd1—Br1^iii	174.324 (13)	C1—C2—C3	118.0 (3)
Cd1—Br1—Cd1^iv	91.311 (10)	C1—C2—H2	121.0
N1^i—Cd1—Br1	92.11 (3)	C3—C2—H2	121.0
N1^i—Cd1—Br1^ii	92.11 (3)	C2—C3—C4	114.7 (3)
N1^i—Cd1—Br1^iii	87.67 (4)	C2—C3—C3^v	122.77 (17)
Br1^ii—Cd1—Br1^iii	88.689 (10)	C4—C3—C3^v	122.53 (17)
N1—Cd1—Br1^iv	87.67 (4)	N2—C4—C3	125.0 (3)
N1^i—Cd1—Br1^iv	87.67 (4)	N2—C4—H4	117.5
Br1^ii—Cd1—Br1^iv	174.324 (13)	C3—C4—H4	117.5
N1—Cd1—Br1—Cd1^iv	−87.62 (4)	Br1^iv—Cd1—N1—N2	−137.139 (8)
N1^i—Cd1—Br1—Cd1^iv	87.62 (4)	C1—N1—N2—C4	0.0
Br1^ii—Cd1—Br1—Cd1^iv	180.0	Cd1—N1—N2—C4	180.0
Br1^iv—Cd1—Br1—Cd1^iv	0.0	N2—N1—C1—C2	0.0
Br1—Cd1—N1—C1	131.463 (9)	Cd1—N1—C1—C2	180.0
Br1^ii—Cd1—N1—C1	−131.463 (9)	N1—C1—C2—C3	0.0
Br1^iii—Cd1—N1—C1	−42.861 (8)	C1—C2—C3—C4	0.0
Br1^iv—Cd1—N1—C1	42.861 (8)	C1—C2—C3—C3^v	180.0
Br1—Cd1—N1—N2	−48.537 (9)	N1—N2—C4—C3	0.0
Br1^ii—Cd1—N1—N2	48.537 (9)	C2—C3—C4—N2	0.0
Br1^iii—Cd1—N1—N2	137.139 (8)	C3^v—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-µ₄-(4,4'-bipyridazine)- κ⁴N¹:N²:N^1':N^2'-dicadmium(II)]

Crystal data

[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) Å^3	Prism, yellow
Z = 2	0.19 × 0.17 × 0.14 mm

Data collection

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

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)] = 0.017	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.040	H-atom parameters constrained
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0207P)^2 + 0.2521P] where P = (Fo^2 + 2Fc^2)/3
1913 reflections	(Δ/σ)max < 0.001
82 parameters	Δρmax = 0.64 e Å^−3
0 restraints	Δρmin = −0.76 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
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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

Cd1—N1^i	2.516 (2)	N2—C4	1.319 (3)
Cd1—N2	2.488 (2)	C1—C2	1.396 (4)
Cd1—I1^i	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—I2^i	3.0069 (4)	C3—C4	1.417 (3)
N1—C1	1.327 (4)	C3—C3^ii	1.484 (5)
N1—N2	1.343 (4)	C4—H4	0.9400
N2—Cd1—N1^i	84.78 (8)	C1—N1—Cd1^iii	117.61 (19)
N1^i—Cd1—I1	83.71 (5)	N2—N1—Cd1^iii	120.42 (16)
N1^i—Cd1—I1^i	84.50 (5)	C4—N2—N1	120.2 (2)
N1^i—Cd1—I2	165.97 (6)	C4—N2—Cd1	121.62 (19)
N1^i—Cd1—I2^i	86.67 (5)	N1—N2—Cd1	117.93 (16)
N2—Cd1—I1	89.02 (5)	N1—C1—C2	123.8 (3)
N2—Cd1—I1^i	92.34 (5)	N1—C1—H1	118.1
N2—Cd1—I2	84.66 (6)	C2—C1—H1	118.1
N2—Cd1—I2^i	171.43 (6)	C3—C2—C1	117.6 (2)
I1^i—Cd1—I1	167.960 (10)	C3—C2—H2	121.2
I1^i—Cd1—I2	105.137 (10)	C1—C2—H2	121.2
I1—Cd1—I2	86.900 (9)	C2—C3—C4	115.8 (2)
I1^i—Cd1—I2^i	86.356 (10)	C2—C3—C3^ii	123.2 (3)
I1—Cd1—I2^i	90.524 (10)	C4—C3—C3^ii	121.0 (3)
I2—Cd1—I2^i	103.856 (11)	N2—C4—C3	123.5 (3)
Cd1^iii—I1—Cd1	83.071 (8)	N2—C4—H4	118.3
Cd1—I2—Cd1^iii	81.223 (8)	C3—C4—H4	118.3
C1—N1—N2	118.6 (2)
N2—Cd1—I1—Cd1^iii	−49.12 (6)	I2—Cd1—N2—C4	114.6 (2)
N1^i—Cd1—I1—Cd1^iii	−133.97 (5)	I1—Cd1—N2—C4	−158.4 (2)
I1^i—Cd1—I1—Cd1^iii	−145.74 (4)	N1^i—Cd1—N2—N1	110.95 (16)
I2—Cd1—I1—Cd1^iii	35.593 (9)	I1^i—Cd1—N2—N1	−164.80 (17)
I2^i—Cd1—I1—Cd1^iii	139.441 (6)	I2—Cd1—N2—N1	−59.81 (17)
N2—Cd1—I2—Cd1^iii	55.23 (5)	I1—Cd1—N2—N1	27.17 (17)
N1^i—Cd1—I2—Cd1^iii	13.9 (2)	N2—N1—C1—C2	−5.6 (4)
I1^i—Cd1—I2—Cd1^iii	146.214 (7)	Cd1^iii—N1—C1—C2	153.9 (2)
I1—Cd1—I2—Cd1^iii	−34.074 (7)	N1—C1—C2—C3	0.5 (4)
I2^i—Cd1—I2—Cd1^iii	−123.849 (12)	C1—C2—C3—C4	4.8 (4)
C1—N1—N2—C4	4.7 (4)	C1—C2—C3—C3^ii	−175.6 (3)
Cd1^iii—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)
Cd1^iii—N1—N2—Cd1	20.4 (2)	C2—C3—C4—N2	−5.8 (4)
N1^i—Cd1—N2—C4	−74.6 (2)	C3^ii—C3—C4—N2	174.6 (3)
I1^i—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.