Poly[dibromidobis[μ-1-(pyridin-4-ylmeth­yl)-1H-1,2,4-triazole-κ²N:N′]cadmium]

The title coordination polymer, [CdBr₂(C₈H₈N₄)₂]_n, arose from a layer-separated diffusion synthesis at room temperature. The title compound is isotypic with the I and Cl analogues. The Cd atom, located on an inversion center, is coordinated by two bromide ions and four N atoms (two from triazole rings and two from pyridyl rings) in a distorted trans-CdBr₂N₄ octa­hedral arrangement. The bridging 1-(4-pyridyl­meth­yl)-1H-1,2,4-triazole ligands are twisted [dihedral angle between the triazole and pyridine rings = 72.56 (13)°], affording a two-dimensional 4⁴ sheet structure in the crystal.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.024
• wR factor = 0.069
• Data-to-parameter ratio = 18.3

checkCIF/PLATON results

No syntax errors found



Alert level C
SHFSU01_ALERT_2_C  The absolute value of parameter shift to su ratio > 0.05
            Absolute value of the parameter shift to su ratio given   0.083
            Additional refinement cycles may be required.
PLAT080_ALERT_2_C Maximum Shift/Error ............................       0.08
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Cd1    --  Br1     ..       6.73 su
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          3
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         25
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....         11
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600          2

Alert level G
PLAT063_ALERT_4_G Crystal Size Likely too Large for Beam Size ....       0.65 mm
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        293 K
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Cd1     .......       2.01

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   7 ALERT level C = Check and explain
   4 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

Recently, our group has focused on the design and synthesis of some flexible unsymmetric ligands (Liu et al., 2005; Huang et al., 2006), one of which being the heterocyclic ligand pyta, N-(4-pyridylmethyl)-1,2,4-triazole. In order to explore the architectural styles and other features of this kind of ligands, we selected cadmium dibromide as a representative subject for stereoregular coordination. Among our attempts, a new polymer [CdBr₂(pyta)₂]_n was obtained as crystals suitable for single-crystal X-ray analysis.

The crystal structure of the title compound is isomorphous to other complexes we have reported with I or Cl in place of Br (Wang et al., 2008, 2010) or with Cu(II) and Cl (Li et al., 2009). The crystallographic analysis reveals that the title compound crystallizes in the monoclinic space group P2₁/c. The asymmetric unit contains one cadmium atom, one bromide donor and one pyta bridging molecule, as shown in Fig. 1. The Cd(II) ion is placed on an inversion center, with an octahedral [CdBr₂N₄] environment, where the axial positions are occupied by two bromide ions and the equatorial positions occupied by two trans triazole N atoms and two trans pyridyl N atoms, each of which respectively belonging to four symmetry-related pyta ligands (Fig. 1). The bond angles about the Cd octahedron range from 85.88 (8) to 94.12 (8)° and deviate slightly from those of a perfect octahedron. Due to the existence of the —CH₂— spacer between the triazole and the pyridyl ring, sufficient flexibility makes possible for pyta to be twisted in order to meet the requirement of coordination geometry of the metal center. The dihedral angle between the triazole and pyridyl rings in the ligand is 72.56 (13)°.

As conveniently shown in Fig. 2, the title compound forms an infinite two-dimensional rhombohedral sheet containing 36-membered sandglass rings. The sp³ hybridization of C3 forces the pyta ligand to be non-linear, generating the nonlinear grid sides and thereby the sandglass grids. Every complementary four [Cd₄(pyta)₄] grids are connected together by sharing the cadmium apices to give the 4⁴ two-dimensional structure with a side length of 11.01 Å, and a diagonal measurement of about 14.31 × 16.73 Ų.

Related literature

For structures of Cd(II) polymers with related ligands, see: Liu et al. (2005); Huang et al. (2006). For the structures of isotypic analogues with I and Cl, see: Wang et al. (2008, 2010). For the structure of the isotypic complex with Cu(II) and Cl, see: Li et al. (2009).

S2. Experimental

A solution of pyta (0.021 g, 0.10 mmol) in MeOH (5 ml) was carefully layered on a solution of CdBr₂ (0.027 g, 0.10 mmol) in H₂O (5 ml). Diffusion between the two phases over a period of two weeks produced colorless block crystals.

S3. Refinement

All H atoms were placed in calculated positions and refined using a riding model with C—H bond lengths fixed to 0.93 (aromatic) or 0.97 Å (methylene), and isotropic displacement parameters calculated as 1.2 times the equivalent displacement parameter of the carrier C atom.

Computing details

Data collection: CrystalClear (Rigaku/MSC, 2004); cell refinement: CrystalClear (Rigaku/MSC, 2004); data reduction: CrystalClear (Rigaku/MSC, 2004); 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: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A view of the structure of the title compound, showing 30% probability displacement ellipsoids. H atoms have been omitted for clarity. Symmetry codes: (A) -x, -y + 1, -z; (B) -x + 1, y + 1/2, -z + 1/2; (C) x - 1, -y + 3/2, z - 1/2.
	Fig. 2. The two-dimensional structure of the title compound, constructed of rhombus-shaped grids.

Poly[dibromidobis[µ-1-(pyridin-4-ylmethyl)-1H-1,2,4-triazole- κ²N:N']cadmium]

Crystal data

[CdBr2(C8H8N4)2]	F(000) = 572
Mr = 592.59	Dx = 1.961 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2944 reflections
a = 7.7802 (9) Å	θ = 2.6–27.5°
b = 16.7299 (16) Å	µ = 5.09 mm^−1
c = 8.4684 (10) Å	T = 293 K
β = 114.409 (5)°	Block, yellow
V = 1003.74 (19) Å^3	0.65 × 0.60 × 0.55 mm
Z = 2

Data collection

Rigaku Mercury70 CCD diffractometer	2270 independent reflections
Radiation source: fine-focus sealed tube	2098 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
Detector resolution: 14.6306 pixels mm^-1	θmax = 27.5°, θmin = 3.1°
ω scans	h = −10→10
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −21→19
Tmin = 0.498, Tmax = 1.000	l = −10→10
7206 measured reflections

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) = 0.069	H-atom parameters constrained
S = 0.91	w = 1/[σ^2(Fo^2) + (0.048P)^2 + 0.7729P] where P = (Fo^2 + 2Fc^2)/3
2270 reflections	(Δ/σ)max = 0.083
124 parameters	Δρmax = 0.74 e Å^−3
0 restraints	Δρmin = −0.51 e Å^−3
0 constraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cd1	0.0000	0.5000	0.5000	0.02280 (9)
Br1	0.19066 (4)	0.538566 (18)	0.30452 (4)	0.03501 (10)
C1	0.2617 (4)	0.57653 (19)	0.8969 (4)	0.0371 (6)
H1A	0.1582	0.5731	0.9248	0.044*
C2	0.4305 (4)	0.56459 (17)	0.7599 (4)	0.0303 (5)
H2A	0.4757	0.5526	0.6768	0.036*
C3	0.7295 (4)	0.61998 (17)	0.9870 (4)	0.0380 (7)
H3A	0.7919	0.5889	0.9293	0.046*
H3B	0.7836	0.6045	1.1082	0.046*
C4	0.7711 (4)	0.70758 (15)	0.9750 (4)	0.0297 (6)
C5	0.6428 (4)	0.76858 (18)	0.9397 (5)	0.0404 (7)
H5A	0.5176	0.7576	0.9173	0.048*
C6	0.7013 (4)	0.84676 (17)	0.9379 (4)	0.0388 (7)
H6A	0.6129	0.8875	0.9146	0.047*
C7	1.0005 (4)	0.8062 (2)	1.0007 (5)	0.0458 (8)
H7A	1.1243	0.8186	1.0204	0.055*
C8	0.9543 (5)	0.72732 (18)	1.0071 (5)	0.0439 (8)
H8A	1.0458	0.6877	1.0329	0.053*
N1	0.5308 (3)	0.59953 (13)	0.9121 (3)	0.0299 (5)
N2	0.4232 (4)	0.60782 (17)	1.0010 (3)	0.0421 (6)
N3	0.2588 (3)	0.54957 (14)	0.7446 (3)	0.0293 (5)
N4	0.8769 (3)	0.86608 (13)	0.9675 (3)	0.0327 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.02036 (14)	0.01935 (14)	0.02797 (15)	0.00065 (9)	0.00926 (11)	−0.00225 (9)
Br1	0.03130 (17)	0.04281 (18)	0.03652 (17)	0.00314 (12)	0.01962 (13)	0.00383 (11)
C1	0.0407 (16)	0.0381 (15)	0.0380 (15)	−0.0095 (13)	0.0219 (13)	−0.0070 (12)
C2	0.0263 (13)	0.0304 (13)	0.0339 (14)	−0.0032 (11)	0.0120 (11)	−0.0059 (11)
C3	0.0299 (14)	0.0247 (13)	0.0469 (17)	−0.0070 (11)	0.0033 (13)	−0.0006 (12)
C4	0.0316 (14)	0.0218 (12)	0.0318 (13)	−0.0059 (10)	0.0092 (11)	−0.0013 (10)
C5	0.0278 (14)	0.0297 (14)	0.0595 (19)	−0.0051 (11)	0.0138 (14)	0.0007 (13)
C6	0.0298 (14)	0.0243 (13)	0.0595 (19)	0.0013 (11)	0.0157 (14)	0.0046 (12)
C7	0.0329 (16)	0.0255 (15)	0.083 (3)	−0.0035 (12)	0.0282 (17)	−0.0032 (14)
C8	0.0340 (15)	0.0234 (14)	0.075 (2)	−0.0006 (12)	0.0227 (16)	−0.0022 (13)
N1	0.0309 (12)	0.0221 (10)	0.0320 (11)	−0.0059 (9)	0.0083 (10)	−0.0018 (8)
N2	0.0496 (16)	0.0464 (15)	0.0362 (13)	−0.0175 (13)	0.0235 (12)	−0.0127 (11)
N3	0.0257 (11)	0.0310 (12)	0.0297 (11)	−0.0026 (9)	0.0100 (9)	−0.0046 (9)
N4	0.0328 (12)	0.0221 (11)	0.0449 (14)	−0.0022 (9)	0.0177 (11)	0.0007 (9)

Geometric parameters (Å, º)

Cd1—N3	2.363 (2)	C3—H3A	0.9700
Cd1—N3^i	2.363 (2)	C3—H3B	0.9700
Cd1—N4^ii	2.407 (2)	C4—C5	1.372 (4)
Cd1—N4^iii	2.407 (2)	C4—C8	1.376 (4)
Cd1—Br1	2.7178 (4)	C5—C6	1.387 (4)
Cd1—Br1^i	2.7178 (3)	C5—H5A	0.9300
C1—N2	1.310 (4)	C6—N4	1.323 (4)
C1—N3	1.358 (4)	C6—H6A	0.9300
C1—H1A	0.9300	C7—N4	1.335 (4)
C2—N3	1.312 (4)	C7—C8	1.375 (4)
C2—N1	1.334 (4)	C7—H7A	0.9300
C2—H2A	0.9300	C8—H8A	0.9300
C3—N1	1.449 (4)	N1—N2	1.345 (4)
C3—C4	1.513 (4)	N4—Cd1^iv	2.407 (2)
N3—Cd1—N3^i	180.0	H3A—C3—H3B	107.6
N3—Cd1—N4^ii	85.88 (8)	C5—C4—C8	117.8 (3)
N3^i—Cd1—N4^ii	94.12 (8)	C5—C4—C3	125.3 (3)
N3—Cd1—N4^iii	94.12 (8)	C8—C4—C3	116.9 (3)
N3^i—Cd1—N4^iii	85.88 (8)	C4—C5—C6	119.4 (3)
N4^ii—Cd1—N4^iii	180.0	C4—C5—H5A	120.3
N3—Cd1—Br1	88.21 (6)	C6—C5—H5A	120.3
N3^i—Cd1—Br1	91.79 (6)	N4—C6—C5	123.1 (3)
N4^ii—Cd1—Br1	90.06 (6)	N4—C6—H6A	118.4
N4^iii—Cd1—Br1	89.94 (6)	C5—C6—H6A	118.4
N3—Cd1—Br1^i	91.79 (6)	N4—C7—C8	123.4 (3)
N3^i—Cd1—Br1^i	88.21 (6)	N4—C7—H7A	118.3
N4^ii—Cd1—Br1^i	89.94 (6)	C8—C7—H7A	118.3
N4^iii—Cd1—Br1^i	90.06 (6)	C7—C8—C4	119.3 (3)
Br1—Cd1—Br1^i	180.0	C7—C8—H8A	120.4
N2—C1—N3	114.0 (3)	C4—C8—H8A	120.4
N2—C1—H1A	123.0	C2—N1—N2	109.6 (2)
N3—C1—H1A	123.0	C2—N1—C3	128.3 (3)
N3—C2—N1	110.2 (3)	N2—N1—C3	121.9 (2)
N3—C2—H2A	124.9	C1—N2—N1	103.2 (2)
N1—C2—H2A	124.9	C2—N3—C1	103.0 (2)
N1—C3—C4	114.7 (2)	C2—N3—Cd1	128.17 (19)
N1—C3—H3A	108.6	C1—N3—Cd1	128.52 (19)
C4—C3—H3A	108.6	C6—N4—C7	117.0 (2)
N1—C3—H3B	108.6	C6—N4—Cd1^iv	125.46 (19)
C4—C3—H3B	108.6	C7—N4—Cd1^iv	117.12 (19)

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