catena-Poly[[(2,2′-bi­pyridine-κ²N,N′)lead(II)]-di-μ-bromido]

The polymeric title compound, [PbBr₂(C₁₀H₈N₂)]_n, consists of ¹_∞[PbBr_4/2] chains running parallel to [001]. Each Pb^II atom is additionally chelated by a 2,2′-bi­pyridine ligand, completing a distorted octa­hedral Br₄N₂ coordination set. In the crystal, weak C—H⋯Br hydrogen bonds and π–π stacking inter­actions link the [PbBr₂(C₁₀H₈N₂)]_n chains into a three-dimensional supra­molecular structure.

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Chemical scheme

Structure description

In the context of studies of metal complexes derived from halogen benzoic acids X-C₆H₄COOH, where X is F, Cl, Br or I, and ancilliary chelating ligands (Zhang et al., 2004; Zhang, 2005, 2006), we originally intended to synthesize a lead(II) complex derived from 6-bromo-2-pyridine­carb­oxy­lic acid and 2,2′-bi­pyridine (bpy). However, we accidentally obtained instead an 1:1 adduct of PbBr₂ with bpy, [PbBr₂(C₁₀H₈N₂)]_n (Fig. 1), that supposedly formed due to decomposition of the acid under the applied solvothermal conditions.

Figure 1 A view of the chain of bromide-bridged Pb^II ions in the title compound extending parallel to [001]. Displacement ellipsoids are drawn at the 40% probability level [symmetry code (i) 1 − x, y,  − z].

Both the Pb^II atom and the chelating pby mol­ecule lie on a twofold rotation axis. In the crystal, Pb1^II atoms are bridged by two pairs of Br1 ligands into ¹_∞[PbBr_4/2] chains (Br—Pb—Br and Pb—Br—Pb angles are 89.87 (6) and 90.13 (6)°, respectively) with a Pb⋯Pb distance in the chain of 4.3434 (9) Å (Fig. 1). The closest plane-to-plane distance between two bpy ligands of 3.376 (2) Å indicates the existence of π–π inter­actions, which results in the formation of a layered arrangement of the [PbBr₂(C₁₀H₈N₂)]_n chains parallel to (100). The layers are associated through weak C—H⋯Br hydrogen bonds (Table 1, Fig. 2) into an overall three-dimensional supra­molecular set-up.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯Br1^i	0.93	2.98	3.906 (9)	174
Symmetry code: (i) .

Figure 2 A packing diagram of the title compound viewed along [001]. Dashed lines indicate C—H⋯Br hydrogen bonds.

The chain structure of the title compound resembles that of related cadmium compounds with composition [CdX₂(phen)] (phen = 1,10-phenanthroline), X = Cl, Chen et al., 2003; X = Br, (Zhang, 2007) or [CdCl₂(2,2-bpy)] (Zhou et al., 2003).

Synthesis and crystallization

Freshly prepared Pb(CH₃COO)₂·3H₂O (0.1890 g 0.50 mmol), 2,2′-bi­pyridine (bpy) (0.0399 g 0.25 mmol), 6-bromo-2-pyridine­carb­oxy­lic acid (0.0504 g 0.25 mmol), and 15 ml CH₃OH/H₂O (1:2,v/v) were mixed and stirred for ca 2.0 h. Subsequently, the resulting suspension was heated in a 23 ml Teflon-lined stainless steel autoclave at 433 K for 7 days. After the autoclave was cooled to room temperature, yellow crystals with a cuboid form were obtained.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	[PbBr2(C10H8N2)]
Mr	523.19
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	293
a, b, c (Å)	16.249 (3), 9.878 (2), 8.2425 (16)
β (°)	104.79 (3)
V (Å^3)	1279.2 (4)
Z	4
Radiation type	Mo Kα
μ (mm^−1)	19.41
Crystal size (mm)	0.24 × 0.23 × 0.21
Data collection
Diffractometer	Rigaku R-AXIS RAPID
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995)
Tmin, Tmax	0.013, 0.017
No. of measured, independent and observed [I > 2σ(I)] reflections	4632, 1053, 871
Rint	0.123
(sin θ/λ)max (Å^−1)	0.583
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.043, 0.124, 1.21
No. of reflections	1053
No. of parameters	58
No. of restraints	21
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å^−3)	1.64, −1.97
Computer programs: RAPID-AUTO (Rigaku, 1998), CrystalStructure (Rigaku/MSC, 2002), SHELXS97 and SHELXTL (Sheldrick, 2008) and SHELXL97 (Sheldrick, 2008).

Structural data

S1. Comment

In the context of studies of metal complexes derived from halogen benzoic acids X-C₆H₄COOH, where X is F, Cl, Br or I, and ancilliary chelating ligands (Zhang et al., 2004; Zhang, 2005, 2006), we originally intended to synthesize a lead(II) complex derived from 6-bromo-2-pyridinecarboxylic acid and 2,2'-bipyridine (bpy). However, we accidentally obtained instead an 1:1 adduct of PbBr₂ with bpy, [PbBr₂(C₁₀H₈N₂)]_n, that supposedly formed due to decomposition of the acid under the applied solvothermal conditions. Both the Pb^II atom and the chelating pby molecule lie on a twofold rotation axis. In the crystal, Pb1^II atoms are bridged by two pairs of Br1 ligands into ¹_∞[PbBr_4/2] chains (Br—Pb—Br and Pb—Br—Pb angles are 89.87 (6) and 90.13 (6)°, respectively) with a Pb···Pb distance in the chain of 4.3434 (9) Å (Fig. 1). In the crystal, the closest plane-to-plane distance between two bpy ligands of 3.376 (2) Å indicates the existence of π—π interactions, which results in the formation of a layered arrangement of the [PbBr₂(C₁₀H₈N₂)]_n chains parallel to (100). The layers are associated through weak C—H···Br hydrogen bonds (Table 1, Fig. 2) into an overall three-dimensional supramolecular set-up.

The chain structure of the title compound resembles that of related cadmium compounds with composition [CdX₂(phen)] (phen = 1,10-phenantroline), X = Cl, Chen et al., 2003; X = Br, (Zhang, 2007) or [CdCl₂(2,2-bpy)] (Zhou et al., 2003).

S2. Experimental

Freshly prepared Pb(CH₃COO)₂·3H₂O (0.1890 g 0.50 mmol), 2,2'-bipyridine (bpy) (0.0399 g 0.25 mmol), 6-bromo-2-pyridinecarboxylic acid (0.0504 g 0.25 mmol), and 15 ml CH₃OH/H₂O (1:2,v/v) were mixed and stirred for ca 2.0 h. Subsequently, the resulting suspension was heated in a 23 ml Teflon-lined stainless steel autoclave at 433 K for 7 days. After the autoclave was cooled to room temperature, yellow crystals with a cuboid form were obtained.

S3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Computing details

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. A view of the chain of bromide-bridged Pb^II ions in the title compound extending parallel to [001]. Displacement ellipsoids are drawn at the 40% probability level [symmetry code (i) 1 - x, y, 1/2 - z].
	Fig. 2. A packing diagram of the title compound viewed down [001]. Dashed lines indicate C—H···Br hydrogen bonds.

catena-Poly[[(2,2'-bipyridine-κ²N,N')lead(II)]-di-µ-bromido]

Crystal data

[PbBr2(C10H8N2)]	F(000) = 936
Mr = 523.19	Dx = 2.717 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 4297 reflections
a = 16.249 (3) Å	θ = 3.3–24.5°
b = 9.878 (2) Å	µ = 19.41 mm^−1
c = 8.2425 (16) Å	T = 293 K
β = 104.79 (3)°	Cuboid, yellow
V = 1279.2 (4) Å^3	0.24 × 0.23 × 0.21 mm
Z = 4

Data collection

Rigaku R-AXIS RAPID diffractometer	1053 independent reflections
Radiation source: fine-focus sealed tube	871 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.123
ω scans	θmax = 24.5°, θmin = 3.3°
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	h = −18→18
Tmin = 0.013, Tmax = 0.017	k = −11→11
4632 measured reflections	l = −9→8

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.043	H-atom parameters constrained
wR(F^2) = 0.124	w = 1/[σ^2(Fo^2) + (0.P)^2 + 35.8179P] where P = (Fo^2 + 2Fc^2)/3
S = 1.21	(Δ/σ)max < 0.001
1053 reflections	Δρmax = 1.64 e Å^−3
58 parameters	Δρmin = −1.97 e Å^−3
21 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0010 (2)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
Pb1	0.5000	0.43060 (8)	0.2500	0.0502 (5)
Br1	0.62002 (14)	0.3951 (2)	0.0295 (3)	0.0700 (6)
C1	0.3595 (8)	0.2242 (10)	−0.0180 (13)	0.073 (6)
H1	0.3389	0.3078	−0.0624	0.087*
C2	0.3177 (7)	0.1061 (13)	−0.0845 (14)	0.086 (5)
H2	0.2692	0.1106	−0.1733	0.103*
C3	0.3485 (8)	−0.0188 (10)	−0.0181 (17)	0.086 (5)
H3	0.3206	−0.0979	−0.0626	0.103*
C4	0.4210 (8)	−0.0256 (7)	0.1147 (16)	0.061 (4)
H4	0.4416	−0.1092	0.1590	0.073*
C5	0.4628 (6)	0.0925 (9)	0.1811 (12)	0.059 (4)
N1	0.4320 (7)	0.2174 (8)	0.1147 (12)	0.055 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.0539 (7)	0.0463 (6)	0.0447 (6)	0.000	0.0023 (4)	0.000
Br1	0.0603 (14)	0.0770 (12)	0.0718 (12)	0.0152 (10)	0.0151 (9)	0.0157 (9)
C1	0.074 (15)	0.092 (13)	0.043 (9)	0.022 (11)	−0.002 (10)	−0.022 (9)
C2	0.060 (11)	0.098 (10)	0.101 (12)	−0.010 (9)	0.022 (10)	−0.046 (10)
C3	0.060 (11)	0.098 (10)	0.101 (12)	−0.010 (9)	0.023 (10)	−0.046 (10)
C4	0.063 (9)	0.050 (6)	0.083 (9)	−0.009 (6)	0.041 (8)	−0.010 (6)
C5	0.060 (9)	0.049 (6)	0.081 (9)	−0.008 (6)	0.042 (8)	−0.010 (6)
N1	0.045 (9)	0.062 (8)	0.059 (8)	−0.003 (7)	0.011 (7)	−0.016 (7)

Geometric parameters (Å, º)

Pb1—N1	2.504 (7)	C1—H1	0.9300
Pb1—N1^i	2.504 (15)	C2—C3	1.3900
Pb1—Br1	3.006 (2)	C2—H2	0.9300
Pb1—Br1^i	3.006 (2)	C3—C4	1.3900
Pb1—Br1^ii	3.128 (2)	C3—H3	0.9300
Pb1—Br1^iii	3.128 (2)	C4—C5	1.3900
Br1—Pb1^iii	3.128 (2)	C4—H4	0.9300
C1—C2	1.3900	C5—N1	1.3900
C1—N1	1.3900	C5—C5^i	1.433 (17)
N1—Pb1—N1^i	65.5 (6)	C2—C1—H1	120.0
N1—Pb1—Br1	85.0 (3)	N1—C1—H1	120.0
N1^i—Pb1—Br1	83.7 (6)	C1—C2—C3	120.0
N1—Pb1—Br1^i	83.7 (3)	C1—C2—H2	120.0
N1^i—Pb1—Br1^i	85.0 (6)	C3—C2—H2	120.0
Br1—Pb1—Br1^i	166.60 (8)	C2—C3—C4	120.0
N1—Pb1—Br1^ii	155.8 (2)	C2—C3—H3	120.0
N1^i—Pb1—Br1^ii	90.8 (4)	C4—C3—H3	120.0
Br1—Pb1—Br1^ii	97.52 (7)	C5—C4—C3	120.0
Br1^i—Pb1—Br1^ii	89.87 (6)	C5—C4—H4	120.0
N1—Pb1—Br1^iii	90.8 (2)	C3—C4—H4	120.0
N1^i—Pb1—Br1^iii	155.8 (4)	C4—C5—N1	120.0
Br1—Pb1—Br1^iii	89.87 (6)	C4—C5—C5^i	122.73 (11)
Br1^i—Pb1—Br1^iii	97.52 (7)	N1—C5—C5^i	117.27 (9)
Br1^ii—Pb1—Br1^iii	113.19 (9)	C5—N1—C1	120.0
Pb1—Br1—Pb1^iii	90.13 (6)	C5—N1—Pb1	119.9 (5)
C2—C1—N1	120.0	C1—N1—Pb1	120.0 (5)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···Br1^iv	0.93	2.98	3.906 (9)	174

Symmetry code: (iv) x−1/2, −y+1/2, z−1/2.