catena-Poly[[bis­[μ-2,4-dichloro-6-(2-pyridyl­methyl­imino­meth­yl)phenolato]dicadmium(II)]-di-μ-thiocyanato]

The title complex, [Cd₂(C₁₃H₉Cl₂N₂O)₂(NCS)₂]_n, is a novel thio­cyanate-bridged polynuclear cadmium(II) compound. The Cd^II atom is six-coordinated in a distorted octa­hedral configuration, with one O and two N atoms of one Schiff base mol­ecule and one terminal S atom of a bridging thio­cyanate ligand defining the equatorial plane, and one terminal N atom of another bridging thio­cyanate ligand and one O atom of another Schiff base mol­ecule occupying axial positions. Adjacent inversion-related [2,4-dichloro-6-(2-pyridylmethyl­imino­meth­yl)phenolato]cadmium(II) moieties utilize bridging phenolate and thio­cyanate groups to form polymeric chains running along the b 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 (You, 2005b; Adams, Clunas, Fenton, Gregson et al., 2002 or Adams, Clunas, Fenton & Spey, 2002?; Tiron et al., 2003). The Cd^II coordination polymers feature interesting supramolecular structures, such as one-dimensional helical ribbons or molecular zippers, two-dimensional molecular square or triangular grids, and interpenetrating/non-interpenetrating three-dimensional networks (Dai et al., 2002; Chen et al., 2003; Luo et al., 2003); most of these compounds possess photoluminescent properties (Xiong et al., 2000; Wang et al., 2003). Owing to the versatile coordination modes of the ambidentate thiocyanate ligand, this pseudohalide ligand has become one of the most extensively studied building blocks in multidimensional complexes (Sailaja et al., 2003; Dey et al., 2004). Thiocyanate complexes of various dimensionalities have been obtained (Zurowska et al., 2002; Zhang et al., 2003).

Our work is aimed at obtaining multidimensional polymetallic complexes. On the basis of the above considerations, we designed and synthesized a tridentate ligand containing a phenolate O atom, 2,4-dichloro-6-(2-pyridylmethyliminomethyl)phenol (DPMP), with the potential to coordinate through three donor atoms (You & Zhu, 2005b Should this be b?). Thiocyanate ions readily bridge different metal ions through the terminal donor atoms, forming polynuclear complexes (Kuang et al., 2001). The novel polynuclear structure (I), formed by the reaction of the DPMP ligand, ammonium thiocyanate and cadmium(II) acetate, is reported here.

Complex (I) is a phenolate- and thiocyanate-bridged polynuclear cadmium(II) compound (Fig. 1). In the structure, the smallest repeat unit contains two Cd(DPMP) moieties and two bridging thiocyanate anions related by crystallographic centres of symmetry. Each Cd^II atom is six-coordinate in a distorted octahedral configuration, with one O and two N atoms from one Schiff base ligand and one terminal S atom of a bridging thiocyanate ligand defining the equatorial plane. A terminal N atom of another bridging thiocyanate ligand and one O atom of another Schiff base ligand occupy the axial positions. The angles subtended at the Cd^II atom confirm the distorted octahedral coordination (Table 1). It is interesting that the tridentate Schiff base also acts as a bridging ligand, through the phenolate O atom. This behavior has been observed in the dinuclear nickel(II) compound, (µ₂-acetato-O,O'){µ₂-2-N-ethyl-[2-(dimethylamino) ethylaminomethyl)]-6-(2-pyridylmethyliminomethyl)-4-methylphenolato}(µ₂-isothiocyanato)isothiocyanatomethanoldinickel (BADHEU; Adams, Clunas, Fenton, Gregson et al., 2002 or Adams, Clunas, Fenton & Spey, 2002?). In complexes containing phenolate O atoms that are not acting as the bridging group, the Schiff base ligands are nearly coplanar (You, 2005a,b,c). However, the Schiff base ligand is severely distorted in (I), with a dihedral angle between the pyridine and phenol rings of 43.5 (2)°, promoted by the coordination of the bridging phenolate O atom to another metal ion. The same pattern can be observed in a similar phenolate O-bridged structure, bis{[µ₂-N-(phenyl-2-thiolato)salicylaldiminato-O,O,S,N](1,10-phenanthroline-N,N')cadmium(II)} (WIGRUZ; Labisbal et al., 1994). The thiocyanate anion here acts as a bridging ligand by coordinating to symmetry-related cadmium(II) ions via the terminal N and S atoms.

The bond lengths subtended at atom Cd1 are comparable to those observed in other Schiff base–cadmium(II) complexes (You & Zhu, 2005a) and WIGRUZ, but much longer, as expected for the greater atomic radii, in than the corresponding Ni^II structure BADHEU [e.g. Ni1—O1 = 2.001 (2) Å]. The bridging thiocyaanate group is nearly linear and shows bent coordination modes with the metal atoms, as observed in BADHEU. The N1—Cd1—N2 bond angle of the Cd1/N1/C8/C9/N2 chelate ring is much smaller than 90°, as expected for a five-membered chelate ring; this ring approximates to an envelope conformation with atom N1 as the flap (Spek, 2003). Atom O1 lies out of the C1–C6 phenyl ring, by 0.112 (2) Å, towards the Cd1ⁱ direction [symmetry code: (i) 1 − x, 1 − y, 1 − z], as might be expected from its bridging coordination to the Cd1ⁱ ion. The same pattern is observed in WIGRUZ, where atom O1 deviates from the phenyl ring by 0.015 (2) Å.

In the crystal structure, the bis(DPMP) dicadmium(II) moieties are linked by the bridging thiocyanate ligands into polymeric chains with backbones of the type [–Cd-(N—C—S)₂—Cd—O₂]_n, running along the b axis (Fig. 2). There are weak but significant interactions, such as C8—H8B···N3 and C10—H10···π bonding to the C1–C6 ring, which complement the main binding of the polymeric chain.

S2. Experimental

3,5-Dichlorosalicylaldehyde (0.1 mmol, 19.1 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 clear yellow solution. To the solution was added an aqueous solution (2 ml) of NH₄NCS (0.1 mmol, 7.6 mg) and an MeOH solution (3 ml) of Cd(CH₃COO)₂·4H₂O (0.1 mmol, 30.3 mg), with stirring. The mixture was stirred for another 10 min at room temperature. After the filtrate had been keept in air for 13 d, colourless block-shaped crystals were formed at the bottom of the vessel.

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 suffixes A and B are related by the symmetry operations (1 − x, −y, 1 − z) and (1 − x, 1 − y, 1 − z).
	Fig. 2. The crystal packing of (I), viewed along the a axis.

Poly[bis[µ-2,4-dichloro-6-(2-pyridylmethyliminomethyl)phenolato]-di-µ- thiocyanato-dicadmium(II)]

Crystal data

[Cd2(C13H9Cl2N2O)2(NCS)2]	F(000) = 880
Mr = 450.60	Dx = 1.855 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5699 reflections
a = 13.131 (1) Å	θ = 2.5–27.5°
b = 7.829 (1) Å	µ = 1.82 mm^−1
c = 16.911 (2) Å	T = 298 K
β = 111.903 (1)°	Block, colourless
V = 1613.0 (3) Å^3	0.20 × 0.20 × 0.12 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	3640 independent reflections
Radiation source: fine-focus sealed tube	3085 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ω scan	θmax = 27.5°, θmin = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −17→17
Tmin = 0.713, Tmax = 0.812	k = −10→9
13342 measured reflections	l = −21→21

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.071	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0365P)^2 + 0.562P] where P = (Fo^2 + 2Fc^2)/3
3640 reflections	(Δ/σ)max < 0.001
199 parameters	Δρmax = 0.64 e Å^−3
0 restraints	Δρmin = −0.46 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	0.437323 (15)	0.32768 (2)	0.530283 (11)	0.04098 (8)
Cl1	0.79076 (8)	0.22352 (14)	0.51392 (7)	0.0793 (3)
Cl2	1.00524 (9)	0.33837 (18)	0.84719 (10)	0.1275 (6)
S1	0.67522 (7)	−0.16587 (10)	0.60862 (5)	0.0571 (2)
O1	0.60797 (14)	0.4021 (2)	0.53853 (11)	0.0451 (4)
N1	0.50280 (18)	0.4953 (3)	0.65275 (14)	0.0480 (5)
N2	0.29683 (19)	0.3596 (3)	0.58221 (15)	0.0505 (6)
N3	0.5155 (2)	0.0749 (3)	0.60160 (15)	0.0610 (7)
C1	0.6962 (2)	0.4373 (4)	0.69002 (18)	0.0527 (7)
C2	0.6934 (2)	0.3816 (4)	0.61007 (18)	0.0470 (6)
C3	0.7899 (2)	0.3039 (4)	0.6090 (2)	0.0567 (8)
C4	0.8835 (3)	0.2873 (5)	0.6813 (3)	0.0728 (11)
H4	0.9451	0.2323	0.6788	0.087*
C5	0.8848 (3)	0.3530 (5)	0.7569 (3)	0.0740 (11)
C6	0.7945 (3)	0.4255 (4)	0.7620 (2)	0.0665 (9)
H6	0.7971	0.4686	0.8140	0.080*
C7	0.6021 (2)	0.5087 (4)	0.70363 (17)	0.0551 (7)
H7	0.6156	0.5693	0.7538	0.066*
C8	0.4176 (2)	0.5765 (4)	0.67372 (19)	0.0562 (7)
H8A	0.4029	0.6887	0.6475	0.067*
H8B	0.4430	0.5917	0.7350	0.067*
C9	0.3130 (2)	0.4742 (4)	0.64407 (18)	0.0500 (7)
C10	0.2346 (3)	0.5049 (5)	0.6785 (2)	0.0676 (9)
H10	0.2485	0.5817	0.7232	0.081*
C11	0.1369 (3)	0.4218 (5)	0.6463 (3)	0.0840 (12)
H11	0.0828	0.4430	0.6683	0.101*
C12	0.1184 (3)	0.3063 (6)	0.5813 (3)	0.0844 (12)
H12	0.0515	0.2499	0.5576	0.101*
C13	0.2015 (3)	0.2764 (5)	0.5520 (2)	0.0654 (8)
H13	0.1907	0.1952	0.5095	0.079*
C14	0.5796 (2)	−0.0246 (3)	0.60243 (15)	0.0473 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.03790 (12)	0.04601 (13)	0.03689 (12)	0.00242 (8)	0.01146 (8)	−0.00375 (8)
Cl1	0.0645 (5)	0.0926 (6)	0.0925 (7)	0.0280 (5)	0.0430 (5)	0.0215 (5)
Cl2	0.0578 (6)	0.1436 (12)	0.1200 (10)	−0.0130 (6)	−0.0372 (6)	0.0329 (8)
S1	0.0512 (4)	0.0554 (4)	0.0502 (4)	0.0036 (3)	0.0022 (3)	−0.0099 (3)
O1	0.0354 (9)	0.0505 (10)	0.0445 (10)	0.0054 (8)	0.0094 (8)	0.0030 (8)
N1	0.0508 (13)	0.0499 (13)	0.0402 (12)	0.0024 (11)	0.0135 (10)	−0.0049 (10)
N2	0.0476 (13)	0.0582 (15)	0.0477 (13)	0.0019 (11)	0.0198 (11)	−0.0014 (11)
N3	0.0769 (18)	0.0533 (15)	0.0448 (14)	0.0156 (14)	0.0135 (12)	−0.0030 (11)
C1	0.0454 (15)	0.0467 (15)	0.0511 (16)	−0.0042 (12)	0.0008 (12)	0.0056 (12)
C2	0.0364 (14)	0.0431 (14)	0.0544 (17)	−0.0008 (11)	0.0088 (12)	0.0105 (12)
C3	0.0377 (15)	0.0537 (17)	0.075 (2)	0.0015 (12)	0.0164 (14)	0.0200 (14)
C4	0.0355 (16)	0.071 (2)	0.099 (3)	0.0011 (15)	0.0102 (17)	0.035 (2)
C5	0.0379 (17)	0.070 (2)	0.084 (3)	−0.0102 (15)	−0.0119 (16)	0.0245 (19)
C6	0.058 (2)	0.0608 (19)	0.0565 (19)	−0.0135 (16)	−0.0067 (15)	0.0072 (15)
C7	0.0647 (19)	0.0538 (17)	0.0370 (14)	−0.0027 (14)	0.0076 (13)	−0.0033 (12)
C8	0.0633 (19)	0.0579 (18)	0.0477 (16)	0.0045 (14)	0.0212 (14)	−0.0106 (13)
C9	0.0589 (17)	0.0483 (16)	0.0487 (15)	0.0121 (13)	0.0267 (13)	0.0083 (12)
C10	0.079 (2)	0.067 (2)	0.074 (2)	0.0120 (18)	0.0490 (19)	0.0021 (17)
C11	0.082 (3)	0.089 (3)	0.110 (3)	0.006 (2)	0.069 (2)	0.001 (2)
C12	0.061 (2)	0.105 (3)	0.100 (3)	−0.010 (2)	0.044 (2)	0.003 (2)
C13	0.0551 (19)	0.074 (2)	0.071 (2)	−0.0057 (16)	0.0273 (17)	−0.0024 (17)
C14	0.0617 (17)	0.0416 (14)	0.0310 (12)	−0.0027 (13)	0.0085 (12)	0.0015 (10)

Geometric parameters (Å, º)

Cd1—O1	2.269 (2)	C1—C7	1.451 (4)
Cd1—N1	2.328 (2)	C2—C3	1.411 (4)
Cd1—N2	2.334 (2)	C3—C4	1.379 (4)
Cd1—N3	2.345 (3)	C4—C5	1.373 (6)
Cd1—O1^i	2.381 (2)	C4—H4	0.9300
Cd1—S1^ii	2.5916 (9)	C5—C6	1.346 (5)
Cl1—C3	1.731 (4)	C6—H6	0.9300
Cl2—C5	1.745 (3)	C7—H7	0.9300
S1—C14	1.647 (3)	C8—C9	1.506 (4)
S1—Cd1^ii	2.5918 (8)	C8—H8A	0.9700
O1—C2	1.317 (3)	C8—H8B	0.9700
O1—Cd1^i	2.3805 (19)	C9—C10	1.379 (4)
N1—C7	1.271 (4)	C10—C11	1.358 (5)
N1—C8	1.441 (4)	C10—H10	0.9300
N2—C13	1.332 (4)	C11—C12	1.374 (6)
N2—C9	1.334 (4)	C11—H11	0.9300
N3—C14	1.143 (4)	C12—C13	1.377 (5)
C1—C2	1.408 (4)	C12—H12	0.9300
C1—C6	1.409 (4)	C13—H13	0.9300
O1—Cd1—N1	76.82 (7)	C5—C4—C3	119.1 (4)
O1—Cd1—N2	148.29 (8)	C5—C4—H4	120.4
N1—Cd1—N2	71.72 (8)	C3—C4—H4	120.4
O1—Cd1—N3	87.28 (9)	C6—C5—C4	120.9 (3)
N1—Cd1—N3	94.16 (8)	C6—C5—Cl2	120.3 (4)
N2—Cd1—N3	98.77 (9)	C4—C5—Cl2	118.8 (3)
O1—Cd1—O1^i	82.11 (6)	C5—C6—C1	121.1 (4)
N1—Cd1—O1^i	82.88 (7)	C5—C6—H6	119.4
N2—Cd1—O1^i	90.02 (7)	C1—C6—H6	119.4
N3—Cd1—O1^i	169.37 (8)	N1—C7—C1	125.5 (3)
O1—Cd1—S1^ii	113.42 (5)	N1—C7—H7	117.3
N1—Cd1—S1^ii	168.00 (6)	C1—C7—H7	117.3
N2—Cd1—S1^ii	97.47 (6)	N1—C8—C9	112.3 (2)
N3—Cd1—S1^ii	92.62 (6)	N1—C8—H8A	109.1
O1^i—Cd1—S1^ii	92.14 (5)	C9—C8—H8A	109.1
C14—S1—Cd1^ii	96.15 (9)	N1—C8—H8B	109.1
C2—O1—Cd1	120.55 (17)	C9—C8—H8B	109.1
C2—O1—Cd1^i	121.95 (17)	H8A—C8—H8B	107.9
Cd1—O1—Cd1^i	97.89 (6)	N2—C9—C10	121.5 (3)
C7—N1—C8	119.4 (2)	N2—C9—C8	118.5 (2)
C7—N1—Cd1	126.4 (2)	C10—C9—C8	119.9 (3)
C8—N1—Cd1	113.87 (17)	C11—C10—C9	119.4 (3)
C13—N2—C9	118.8 (3)	C11—C10—H10	120.3
C13—N2—Cd1	124.4 (2)	C9—C10—H10	120.3
C9—N2—Cd1	116.77 (19)	C10—C11—C12	119.6 (3)
C14—N3—Cd1	139.5 (2)	C10—C11—H11	120.2
C2—C1—C6	119.8 (3)	C12—C11—H11	120.2
C2—C1—C7	123.5 (2)	C11—C12—C13	118.2 (4)
C6—C1—C7	116.6 (3)	C11—C12—H12	120.9
O1—C2—C1	123.6 (3)	C13—C12—H12	120.9
O1—C2—C3	120.1 (3)	N2—C13—C12	122.4 (4)
C1—C2—C3	116.3 (3)	N2—C13—H13	118.8
C4—C3—C2	122.5 (3)	C12—C13—H13	118.8
C4—C3—Cl1	118.4 (3)	N3—C14—S1	177.2 (2)
C2—C3—Cl1	119.0 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8B···N3^iii	0.97	2.61	3.566 (2)	168
C10—H10···Cg5^i	0.93	2.86	3.736 (2)	157

Symmetry codes: (i) −x+1, −y+1, −z+1; (iii) −x+1, y+1/2, −z+3/2.