catena-Poly[[bis­(2-chloro­pyrazine-κN ⁴)cadmium]-di-μ-thio­cyanato-κ² N:S;κ² S:N]

Abstract

Reaction of cadmium thio­cyanate with 2-chloro­pyrazine leads to the polymeric title compound, [Cd(NCS)₂(C₄H₃ClN₂)₂]_n. The Cd^II cation, which is located on a center of inversion, is coordinated by two N-bonded and two S-bonded thio­cyanate anions and by two N-bonded 2-chloro­pyrazine ligands within a slightly distorted octa­hedron. The Cd^II cations are linked into chains along the a axis by bridging thio­cyanate anions.

Related literature  

For the background to this work and the synthesis of bridging thio­cyanato coordination polymers, see: Wöhlert et al. (2012 ▶, 2013 ▶).

Experimental  

Crystal data  

• [Cd(NCS)₂(C₄H₃ClN₂)₂]

• M _r = 457.63

• Triclinic,

• a = 5.7151 (6) Å

• b = 6.7625 (8) Å

• c = 11.2915 (13) Å

• α = 76.895 (9)°

• β = 82.639 (9)°

• γ = 73.068 (8)°

• V = 405.70 (8) ų

• Z = 1

• Mo Kα radiation

• μ = 1.93 mm⁻¹

• T = 293 K

• 0.17 × 0.15 × 0.10 mm

Data collection  

• Stoe IPDS-2 diffractometer

• Absorption correction: numerical (X-SHAPE and X-RED32; Stoe & Cie, 2008 ▶) T _min = 0.551, T _max = 0.719

• 5777 measured reflections

• 1592 independent reflections

• 1492 reflections with I > 2σ(I)

• R _int = 0.068

Refinement  

• R[F ² > 2σ(F ²)] = 0.029

• wR(F ²) = 0.072

• S = 1.02

• 1592 reflections

• 97 parameters

• H-atom parameters constrained

• Δρ_max = 0.56 e Å⁻³

• Δρ_min = −0.49 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2008 ▶); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP in SHELXTL (Sheldrick, 2008 ▶) and DIAMOND (Brandenburg, 2011 ▶); software used to prepare material for publication: XCIF in SHELXTL and publCIF (Westrip, 2010 ▶).

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Cd1—N1	2.287 (3)
Cd1—N12	2.417 (2)
Cd1—S1i	2.7071 (9)

Symmetry code: (i) .

supplementary crystallographic information

Comment

Recently we have reported on the synthesis and characterization of cadmium(II) thiocyanato coordination polymers with different neutral N-donor co-ligands. For [Cd(NCS)₂(4-ethylpyridine)₂]_n a one-dimensional structure was observed, in which the metal cations are octahedrally coordinated by two N and two S atoms of the thiocyanato anions and two N atoms of the co-ligands all of them in an all-trans coordination (Wöhlert et al., 2013). In contrast, for [Cd(NCS)₂(pyridine)₂]_n, three different modifications were obtained in which the anionic ligands are all-trans, all-cis or cis-cis-trans coordinated (Wöhlert et al., 2012). To investigate the influence of the neutral co-ligand in more detail, 2-chloropyrazine was selected, which can act as a bidentate as well as a monodentate ligand. Therefore, cadmium(II) thiocyanate was reacted with 2-chloropyrazine in water which results in the formation of single crystals suitable for structure determination.

The crystal structure of [Cd(NCS)₂(2-chloropyrazine)₂]_n consists of cadmium(II) cations that are located on centers of inversion as well as of thiocyanato anions and 2-chloropyrazine ligand in general position. Each cadmium(II) cation is coordinated by two N-bonded and two S-bonded thiocyanato anions as well as two 2-chloropyrazine ligands within a slightly distorted octahedral geometry (Fig. 1). The CdN₄S₂ distances ranges from 2.287 (3) Å to 2.7071 (9) Å with angles arround the cadmium(II) cation between 87.75 (8) ° to 92.25 (8) ° and of 180 ° (Tab. 1). In the crystal structure the cadmium(II) cations are connected through µ-1,3 bridging thiocyanato anions into one-dimensional polymeric chains, in which all thiocyanato anions and the 2-chloropyrazine ligand are trans-coordinated (Fig. 2). The intrachain cadmium-cadmium separation amounts to 5.7151 (6) Å, whereas the shortest interchain Cd—Cd distance is 11.2915 (13) Å. This structural motiv is frequently found in cadmium thiocyanato coordination compounds and might represent the most stable coordination. However, in this context it is noted that for [Cd(NCS)₂(pyridine)₂]_n, the form with a cis-cis-trans coordination represents the thermodynamic stable form at room-temperature and this might be an exception (Wöhlert et al., 2012).

Experimental

CdSO₄x8/3H₂O, Ba(NCS)₂x3H₂O and 2-chloropyrazine were obtained from Alfa Aesar. All chemicals were used without further purification. Cd(NCS)₂ was prepared by the reaction of equimolar amounts of CdSO₄x8/3H₂O with Ba(NCS)₂x3H₂O in water. The resulting precipitate of BaSO₄ were filtered off and the filtrate were concentrated to complete dryness resulting in white residues of Cd(NCS)₂. The purity was checked by XRPD and CHNS analysis. 0.1 mmol (22.0 mg) Cd(NCS)₂ and 0.4 mmol (32.0 µL) 2-chloropyrazine were reacted in 1 ml water. Colorless single crystals of the title compound were obtained after three days.

Refinement

All H atoms were located in difference map but were positioned with idealized geometry and were refined isotropic with U_iso(H) = 1.2 U_eq(C) using a riding model with C—H = 0.93 Å.

Figures

Fig. 1.

: Crystal structure of the title compound with labeling and displacement ellipsoids drawn at the 50% probability level. Symmetry code: i = -x + 1, -y + 1, -z; ii = x - 1, y, z; iii = -x + 2, -y + 1, -z.

Fig. 2.

: Crystal structure of the title compound with view along the b-axis (orange = cadmium, blue = nitrogen, yellow = sulfur, green = chloro, grey = carbon, white = hydrogen).

Crystal data

[Cd(NCS)2(C4H3ClN2)2]	Z = 1
Mr = 457.63	F(000) = 222
Triclinic, P1	Dx = 1.873 Mg m−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.7151 (6) Å	Cell parameters from 5777 reflections
b = 6.7625 (8) Å	θ = 1.9–26.0°
c = 11.2915 (13) Å	µ = 1.93 mm−1
α = 76.895 (9)°	T = 293 K
β = 82.639 (9)°	Block, colourless
γ = 73.068 (8)°	0.17 × 0.15 × 0.10 mm
V = 405.70 (8) Å3

Data collection

Stoe IPDS-2 diffractometer	1592 independent reflections
Radiation source: fine-focus sealed tube	1492 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.068
ω scan	θmax = 26.0°, θmin = 1.9°
Absorption correction: numerical (X-SHAPE and X-RED32; Stoe & Cie, 2008)	h = −7→7
Tmin = 0.551, Tmax = 0.719	k = −8→8
5777 measured reflections	l = −13→13

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.072	H-atom parameters constrained
S = 1.02	w = 1/[σ2(Fo2) + (0.0411P)2] where P = (Fo2 + 2Fc2)/3
1592 reflections	(Δ/σ)max < 0.001
97 parameters	Δρmax = 0.56 e Å−3
0 restraints	Δρmin = −0.49 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	0.5000	0.0000	0.04055 (12)
N1	0.7466 (5)	0.7003 (4)	0.0217 (3)	0.0512 (6)
N12	0.6360 (5)	0.2497 (4)	0.1840 (2)	0.0457 (6)
C12	0.5473 (6)	0.0818 (5)	0.2234 (3)	0.0485 (7)
H12	0.4340	0.0591	0.1794	0.058*
C11	0.6252 (7)	−0.0574 (5)	0.3298 (3)	0.0502 (8)
C14	0.8718 (8)	0.1294 (6)	0.3560 (3)	0.0623 (9)
H14	0.9856	0.1502	0.4005	0.075*
C13	0.8027 (7)	0.2699 (6)	0.2508 (3)	0.0545 (8)
H13	0.8726	0.3819	0.2247	0.065*
N11	0.7817 (7)	−0.0377 (5)	0.3977 (3)	0.0590 (7)
Cl11	0.5080 (2)	−0.27337 (15)	0.37726 (10)	0.0755 (3)
S1	1.14072 (16)	0.73906 (13)	0.12925 (8)	0.0535 (2)
C1	0.9108 (6)	0.7182 (4)	0.0647 (3)	0.0404 (6)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cd1	0.03692 (19)	0.04198 (17)	0.04287 (19)	−0.01361 (12)	−0.01125 (13)	−0.00014 (12)
N1	0.0460 (16)	0.0474 (13)	0.0632 (17)	−0.0154 (12)	−0.0118 (13)	−0.0089 (12)
N12	0.0451 (15)	0.0484 (13)	0.0416 (14)	−0.0117 (11)	−0.0087 (11)	−0.0031 (11)
C12	0.0487 (18)	0.0482 (15)	0.0459 (16)	−0.0095 (13)	−0.0086 (14)	−0.0057 (13)
C11	0.060 (2)	0.0455 (15)	0.0418 (16)	−0.0124 (14)	−0.0037 (15)	−0.0052 (12)
C14	0.071 (3)	0.071 (2)	0.0480 (18)	−0.0249 (19)	−0.0237 (18)	−0.0015 (16)
C13	0.059 (2)	0.0546 (17)	0.0511 (19)	−0.0204 (15)	−0.0145 (16)	−0.0011 (14)
N11	0.072 (2)	0.0601 (16)	0.0431 (14)	−0.0183 (15)	−0.0143 (14)	0.0004 (12)
Cl11	0.1033 (9)	0.0591 (5)	0.0665 (6)	−0.0365 (5)	−0.0086 (6)	0.0031 (4)
S1	0.0426 (5)	0.0638 (5)	0.0620 (5)	−0.0142 (4)	−0.0100 (4)	−0.0250 (4)
C1	0.0381 (16)	0.0394 (13)	0.0452 (16)	−0.0123 (11)	−0.0033 (13)	−0.0088 (12)

Geometric parameters (Å, º)

Cd1—N1	2.287 (3)	C12—H12	0.9300
Cd1—N1i	2.287 (3)	C11—N11	1.303 (5)
Cd1—N12i	2.417 (2)	C11—Cl11	1.730 (3)
Cd1—N12	2.417 (2)	C14—N11	1.341 (5)
Cd1—S1ii	2.7071 (9)	C14—C13	1.364 (5)
Cd1—S1iii	2.7071 (9)	C14—H14	0.9300
N1—C1	1.158 (4)	C13—H13	0.9300
N12—C12	1.338 (4)	S1—C1	1.636 (3)
N12—C13	1.342 (4)	S1—Cd1iv	2.7071 (9)
C12—C11	1.381 (4)
N1—Cd1—N1i	180.0	C12—N12—Cd1	120.7 (2)
N1—Cd1—N12i	88.62 (10)	C13—N12—Cd1	122.4 (2)
N1i—Cd1—N12i	91.38 (10)	N12—C12—C11	119.6 (3)
N1—Cd1—N12	91.38 (10)	N12—C12—H12	120.2
N1i—Cd1—N12	88.62 (10)	C11—C12—H12	120.2
N12i—Cd1—N12	180.00 (15)	N11—C11—C12	124.5 (3)
N1—Cd1—S1ii	92.25 (8)	N11—C11—Cl11	117.2 (2)
N1i—Cd1—S1ii	87.75 (8)	C12—C11—Cl11	118.2 (3)
N12i—Cd1—S1ii	91.06 (7)	N11—C14—C13	122.5 (4)
N12—Cd1—S1ii	88.94 (7)	N11—C14—H14	118.7
N1—Cd1—S1iii	87.75 (8)	C13—C14—H14	118.7
N1i—Cd1—S1iii	92.25 (8)	N12—C13—C14	121.3 (3)
N12i—Cd1—S1iii	88.94 (7)	N12—C13—H13	119.4
N12—Cd1—S1iii	91.06 (7)	C14—C13—H13	119.4
S1ii—Cd1—S1iii	180.00 (4)	C11—N11—C14	115.1 (3)
C1—N1—Cd1	150.2 (2)	C1—S1—Cd1iv	96.53 (11)
C12—N12—C13	116.9 (3)	N1—C1—S1	178.3 (3)

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