catena-Poly[[[4-bromo-2-(2-pyridyl­methyl­imino­meth­yl)­phenol­ato]­zinc(II)]-μ-chloro]

The title complex, [Zn(C₁₃H₁₀BrN₂O)Cl]_n, is a chloride-bridged polynuclear zinc(II) compound. Each Zn^II ion is five-coordinated in a square-pyramidal configuration, with one O and two N atoms of one Schiff base and one bridging Cl atom defining the basal plane, and another bridging Cl atom occupying the apical position. The novelty of the compound lies in the bridging by chlorine of two square-pyramidal Zn atoms, so that the bridging atom is apical for one Zn ion and basal for the other. This structural arrangement has not been observed before. The linked moieties form polymeric zigzag chains running along the a axis.

S1. Comment

Metal-organic complexes containing bridging ligands are of current interest because of their interesting molecular topologies and crystal packing motifs as well as the fact that they may be designed with specific functionalities (Supriya et al., 2005; Batten & Robson, 1998; Colacio et al., 2005; Abourahma et al., 2002; Konar et al., 2002). In general, chloride anions only bridge two metals or reside at the terminal positions (Gladkikh et al., 1997; Ülkü et al., 2000; Tatar et al., 2002). A similar pattern can be observed in the bromo-coordinated complexes (Hong et al., 2005). Dance (1985) has reported an interesting zinc(II) complex, in which the chloride anion is located on a twofold axis and coordinated to four Zn atoms. There are a few other complexes with similar chain or bridged Zn^II structures (Niu et al., 1999; Schneider et al., 1999; Bottomley et al., 1989; Martin et al., 1998). There are also some complexes with N,O-coordinating ligands to Zn and `capping' by a bridged ZnCl₄ group (Müller & Vahrenkamp, 1999; Tesmer et al., 1997; Follner, 1972). However, a major obstacle to a more comprehensive study of such chloride-coordinated complexes is the lack of rational synthetic procedures, since with the present state of knowledge it is hardly possible to determine which coordination mode will be adopted by the chloride anion.

Our work is aimed at obtaining multidimensional polymetallic complexes. We have designed and synthesized a rigid tridentate ligand, 4-bromo-2-(2-pyridylmethyliminomethyl)phenol (BPMM). The reason we did not use a flexible ligand is that the rigid BPMM ligand should adopt an almost fixed coordination mode through the three donor atoms (You et al., 2004; You & Zhu, 2004). The second ligand, viz. chloride, would then probably act as a bridging group. Zinc(II) is a good candidate for square pyramidal coordination geometry (Erxleben, 2001). We report here a novel chloride-bridged polynuclear zinc(II) complex, (I), formed from the reaction of the BPMM ligand with zinc(II) chloride.

Complex (I) (Fig. 1 and Table 1) contains Zn(BPMM) units connected to each other by a single bridging chloride anion. Each Zn^II ion is five-coordinated in a square pyramidal configuration, with one O and two N atoms of one Schiff base and one terminal Cl atom defining the basal plane, and a symmetry-related Cl atom occupying the apical position, that is, atom Cl1 acts as a basal donor of the Zn1 moiety, while for the Zn1ⁱ moiety, it acts as the apical donor atom [symmetry code: (i) x + 1/2, y, −z + 1/2]. Thus the Zn1—Cl1ⁱ bond is longer by 0.548 (3) Å than the Zn1—Cl1 bond (Table 1). The basal least-square planes of the two adjacent Zn^II centres are nearly parallel, with a dihedral angle of 4.6 (4)°. The deviation of atom Zn1 from the best fit square plane towards Cl1ⁱ is 0.138 (4) Å. Each zinc(II) moiety of the complex is nearly coplanar, with a mean deviation from the Br1/C1–C6/C7/N1/C8/C9–C13/N2/O1 plane of 0.091 (1) Å. This planar configuration can decrease the steric repulsion of the two near planar zinc(II) moieties, and also promote a square pyramidal geometry for the Zn^II atom rather than trigonal-bipyramid geometry.

The C7═N1 bond length conforms to the value for a double bond, while the C8—N1 bond length conforms to the value for a single bond (You, 2005a,b). As expected, the bond involving the pyridine atom N2 is longer than that involving the imine atom N1 (Mondal et al., 2001).

The distance between atom H8A and the planar ring Zn1/O1/C2/C1/C7/N1 is 2.616 (2) Å, with a C8–H8A—centre of ring angle of 112.5 (4)°, indicating that there may be a somewhat fortuitous weak hydrogen intramolecular interaction of the C8–H8A···π type. There is also another intramolecular interaction C13–H13···Cl1 (Table 2). In the crystal structure, the [4-bromo-2-(2-pyridylmethylaminomethylphenolato)zinc(II) moieties are linked by the bridging chloride anions, forming polymeric zigzag chains running along the a axis (Fig. 2).

S2. Experimental

5-Bromosalicylaldehyde (0.1 mmol, 20.1 mg) and 2-aminomethylpyridine (0.1 mmol, 10.8 mg) were dissolved in MeOH (10 ml). The mixture was stirred at room temperature for 10 min to give a yellow solution. To the solution was added an MeOH solution (5 ml) of ZnCl₂·6H₂O (0.1 mmol, 24.4 mg), with stirring. The mixture was stirred for another 10 min at room temperature. After keeping the filtrate in air for 13 d, colourless block-shaped crystals were formed.

S3. Refinement

All H atoms were placed in geometrically idealized positions and allowed to ride on their parent atoms with C—H distances of 0.93–0.97 Å and with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Atoms labelled with the suffix i or unlabelled are at the symmetry position (1/2 + x, y, 1/2 − z).
	Fig. 2. The crystal packing of (I), viewed down the b axis. H atoms have been omitted.

catena-Poly[[[4-bromo-2-(2-pyridylmethyliminomethyl)phenolato]zinc(II)]- µ-chloro]

Crystal data

[Zn(C13H10BrN2O)Cl]	Dx = 1.931 Mg m^−3
Mr = 390.96	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 2244 reflections
a = 7.924 (1) Å	θ = 2.3–22.2°
b = 13.578 (2) Å	µ = 4.99 mm^−1
c = 25.003 (3) Å	T = 298 K
V = 2689.9 (6) Å^3	Block, colourless
Z = 8	0.31 × 0.13 × 0.12 mm
F(000) = 1536

Data collection

Bruker SMART CCD area-detector diffractometer	3091 independent reflections
Radiation source: fine-focus sealed tube	1792 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.113
ω scans	θmax = 27.5°, θmin = 1.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −10→10
Tmin = 0.288, Tmax = 0.550	k = −17→17
28481 measured reflections	l = −32→32

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)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.128	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0498P)^2 + 1.3612P] where P = (Fo^2 + 2Fc^2)/3
3091 reflections	(Δ/σ)max < 0.001
172 parameters	Δρmax = 0.64 e Å^−3
0 restraints	Δρmin = −0.64 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
Zn1	0.60168 (8)	0.46439 (5)	0.25357 (3)	0.0452 (2)
Br1	0.96450 (10)	0.13674 (5)	0.04699 (3)	0.0739 (3)
Cl1	0.39733 (17)	0.57988 (10)	0.24143 (6)	0.0476 (4)
O1	0.6148 (5)	0.4460 (3)	0.17850 (15)	0.0508 (10)
N1	0.7257 (6)	0.3425 (3)	0.26823 (17)	0.0362 (11)
N2	0.5993 (6)	0.4755 (3)	0.33357 (19)	0.0437 (11)
C1	0.7756 (6)	0.2948 (4)	0.1770 (2)	0.0376 (13)
C2	0.6916 (7)	0.3762 (4)	0.1526 (2)	0.0432 (14)
C3	0.6902 (8)	0.3789 (5)	0.0965 (3)	0.0584 (17)
H3	0.6353	0.4306	0.0794	0.070*
C4	0.7667 (8)	0.3085 (5)	0.0664 (3)	0.0583 (17)
H4	0.7641	0.3130	0.0293	0.070*
C5	0.8486 (7)	0.2298 (4)	0.0907 (2)	0.0458 (14)
C6	0.8523 (7)	0.2222 (4)	0.1443 (2)	0.0447 (14)
H6	0.9059	0.1687	0.1601	0.054*
C7	0.7897 (6)	0.2847 (4)	0.2335 (2)	0.0392 (13)
H7	0.8511	0.2312	0.2462	0.047*
C8	0.7512 (7)	0.3211 (4)	0.3247 (2)	0.0430 (14)
H8A	0.8706	0.3118	0.3316	0.052*
H8B	0.6934	0.2604	0.3338	0.052*
C9	0.6859 (7)	0.4028 (4)	0.3589 (2)	0.0439 (14)
C10	0.7116 (8)	0.4059 (5)	0.4140 (2)	0.0567 (17)
H10	0.7718	0.3562	0.4310	0.068*
C11	0.6475 (9)	0.4829 (6)	0.4429 (3)	0.069 (2)
H11	0.6636	0.4857	0.4797	0.083*
C12	0.5594 (9)	0.5558 (5)	0.4172 (3)	0.0661 (19)
H12	0.5149	0.6087	0.4362	0.079*
C13	0.5384 (8)	0.5491 (4)	0.3632 (3)	0.0557 (17)
H13	0.4782	0.5987	0.3461	0.067*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0451 (4)	0.0371 (4)	0.0533 (4)	0.0026 (3)	−0.0033 (3)	−0.0001 (3)
Br1	0.0909 (6)	0.0653 (5)	0.0656 (5)	0.0112 (4)	0.0239 (4)	−0.0050 (4)
Cl1	0.0353 (7)	0.0371 (7)	0.0704 (11)	0.0024 (6)	0.0004 (7)	0.0026 (7)
O1	0.059 (3)	0.045 (2)	0.049 (2)	0.014 (2)	−0.011 (2)	0.0013 (19)
N1	0.040 (3)	0.025 (2)	0.043 (3)	−0.0010 (19)	−0.006 (2)	0.0057 (19)
N2	0.043 (3)	0.037 (3)	0.051 (3)	−0.009 (2)	0.001 (2)	0.002 (2)
C1	0.031 (3)	0.035 (3)	0.047 (3)	−0.004 (2)	0.000 (2)	0.003 (3)
C2	0.037 (3)	0.041 (3)	0.051 (4)	−0.003 (3)	−0.004 (3)	0.001 (3)
C3	0.068 (4)	0.052 (4)	0.055 (4)	0.011 (3)	−0.011 (3)	0.004 (3)
C4	0.062 (4)	0.069 (5)	0.045 (4)	−0.006 (4)	−0.009 (3)	0.004 (3)
C5	0.048 (4)	0.042 (3)	0.048 (4)	−0.003 (3)	0.000 (3)	−0.005 (3)
C6	0.041 (3)	0.037 (3)	0.056 (4)	−0.003 (3)	0.004 (3)	0.008 (3)
C7	0.027 (3)	0.029 (3)	0.061 (4)	−0.003 (2)	−0.003 (2)	0.006 (3)
C8	0.041 (3)	0.042 (3)	0.046 (4)	0.001 (3)	−0.001 (3)	0.006 (3)
C9	0.033 (3)	0.048 (4)	0.051 (4)	−0.013 (3)	0.002 (3)	0.003 (3)
C10	0.059 (4)	0.061 (4)	0.050 (4)	−0.005 (3)	0.004 (3)	0.000 (3)
C11	0.074 (5)	0.083 (5)	0.049 (4)	−0.009 (4)	0.006 (4)	−0.007 (4)
C12	0.070 (5)	0.069 (5)	0.059 (5)	−0.001 (4)	0.012 (4)	−0.015 (4)
C13	0.060 (4)	0.047 (4)	0.060 (4)	0.004 (3)	0.010 (3)	−0.002 (3)

Geometric parameters (Å, º)

Zn1—O1	1.896 (4)	C4—C5	1.390 (8)
Zn1—N1	1.959 (4)	C4—H4	0.9300
Zn1—N2	2.006 (5)	C5—C6	1.343 (7)
Zn1—Cl1	2.274 (3)	C6—H6	0.9300
Zn1—Cl1^i	2.822 (2)	C7—H7	0.9300
Br1—C5	1.908 (6)	C8—C9	1.493 (8)
O1—C2	1.299 (6)	C8—H8A	0.9700
N1—C7	1.276 (6)	C8—H8B	0.9700
N1—C8	1.456 (6)	C9—C10	1.394 (8)
N2—C13	1.335 (7)	C10—C11	1.367 (8)
N2—C9	1.359 (7)	C10—H10	0.9300
C1—C6	1.416 (7)	C11—C12	1.372 (9)
C1—C7	1.424 (7)	C11—H11	0.9300
C1—C2	1.427 (7)	C12—C13	1.363 (9)
C2—C3	1.402 (8)	C12—H12	0.9300
C3—C4	1.360 (8)	C13—H13	0.9300
C3—H3	0.9300
O1—Zn1—N1	92.67 (17)	C5—C6—C1	120.8 (5)
O1—Zn1—N2	175.83 (18)	C5—C6—H6	119.6
N1—Zn1—N2	83.21 (19)	C1—C6—H6	119.6
O1—Zn1—Cl1	89.86 (12)	N1—C7—C1	125.8 (5)
N1—Zn1—Cl1	164.67 (13)	N1—C7—H7	117.1
N2—Zn1—Cl1	94.28 (14)	C1—C7—H7	117.1
C2—O1—Zn1	128.0 (4)	N1—C8—C9	111.0 (4)
C7—N1—C8	118.8 (4)	N1—C8—H8A	109.4
C7—N1—Zn1	126.3 (4)	C9—C8—H8A	109.4
C8—N1—Zn1	114.8 (3)	N1—C8—H8B	109.4
C13—N2—C9	117.9 (5)	C9—C8—H8B	109.4
C13—N2—Zn1	127.9 (4)	H8A—C8—H8B	108.0
C9—N2—Zn1	113.9 (4)	N2—C9—C10	120.8 (6)
C6—C1—C7	118.1 (5)	N2—C9—C8	116.6 (5)
C6—C1—C2	119.6 (5)	C10—C9—C8	122.6 (6)
C7—C1—C2	122.3 (5)	C11—C10—C9	119.4 (6)
O1—C2—C3	118.4 (5)	C11—C10—H10	120.3
O1—C2—C1	124.8 (5)	C9—C10—H10	120.3
C3—C2—C1	116.8 (5)	C10—C11—C12	119.6 (7)
C4—C3—C2	122.2 (6)	C10—C11—H11	120.2
C4—C3—H3	118.9	C12—C11—H11	120.2
C2—C3—H3	118.9	C13—C12—C11	118.5 (6)
C3—C4—C5	120.3 (6)	C13—C12—H12	120.8
C3—C4—H4	119.8	C11—C12—H12	120.8
C5—C4—H4	119.8	N2—C13—C12	123.8 (6)
C6—C5—C4	120.4 (6)	N2—C13—H13	118.1
C6—C5—Br1	120.7 (4)	C12—C13—H13	118.1
C4—C5—Br1	118.8 (5)
N1—Zn1—O1—C2	−3.1 (5)	C4—C5—C6—C1	−1.1 (8)
Cl1—Zn1—O1—C2	−168.0 (4)	Br1—C5—C6—C1	175.9 (4)
O1—Zn1—N1—C7	3.1 (4)	C7—C1—C6—C5	−177.5 (5)
N2—Zn1—N1—C7	−176.3 (5)	C2—C1—C6—C5	0.8 (8)
Cl1—Zn1—N1—C7	102.4 (6)	C8—N1—C7—C1	179.5 (5)
O1—Zn1—N1—C8	−179.9 (4)	Zn1—N1—C7—C1	−3.6 (8)
N2—Zn1—N1—C8	0.7 (4)	C6—C1—C7—N1	−178.7 (5)
Cl1—Zn1—N1—C8	−80.7 (6)	C2—C1—C7—N1	3.0 (8)
N1—Zn1—N2—C13	176.4 (5)	C7—N1—C8—C9	173.0 (5)
Cl1—Zn1—N2—C13	−18.8 (5)	Zn1—N1—C8—C9	−4.2 (5)
N1—Zn1—N2—C9	3.4 (4)	C13—N2—C9—C10	−0.7 (8)
Cl1—Zn1—N2—C9	168.2 (3)	Zn1—N2—C9—C10	173.0 (4)
Zn1—O1—C2—C3	−177.7 (4)	C13—N2—C9—C8	179.5 (5)
Zn1—O1—C2—C1	3.6 (8)	Zn1—N2—C9—C8	−6.8 (6)
C6—C1—C2—O1	178.9 (5)	N1—C8—C9—N2	7.2 (7)
C7—C1—C2—O1	−2.9 (8)	N1—C8—C9—C10	−172.6 (5)
C6—C1—C2—C3	0.1 (7)	N2—C9—C10—C11	0.5 (9)
C7—C1—C2—C3	178.3 (5)	C8—C9—C10—C11	−179.7 (6)
O1—C2—C3—C4	−179.6 (6)	C9—C10—C11—C12	−0.2 (10)
C1—C2—C3—C4	−0.8 (9)	C10—C11—C12—C13	0.0 (10)
C2—C3—C4—C5	0.6 (10)	C9—N2—C13—C12	0.6 (9)
C3—C4—C5—C6	0.4 (9)	Zn1—N2—C13—C12	−172.2 (5)
C3—C4—C5—Br1	−176.6 (5)	C11—C12—C13—N2	−0.2 (11)

Symmetry code: (i) x+1/2, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C13—H13···Cl1	0.93	2.71	3.270 (8)	120