Poly[tris­[μ₂-2-(pyrazol-1-yl)pyrazine]hexa-μ_1,3-thio­cyanato-tricadmium(II)]

The asymmetric unit of the title crystal structure, [Cd₃(NCS)₆(C₇H₆N₄)₂]_n, contains two independent Cd^II ions, one of which is located on a crystallographic inversion center. Each independent Cd^II ion is in a slightly distorted octa­hedral coordination environment, but the disortion from ideally octa­hedral is greater in the environment of the Cd^II ion on a general position. Both thio­cyanate ligands act as bridges connecting independent Cd^II ions, and the 2-(pyrazol-1-yl)pyrazine ligands chelate one Cd^II ion in a bidentate mode while the remaining N atom of the pyrazine ring coordinates to a symmetry-related Cd^II ion, forming a two-dimensional structure parallel to (211).

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.022
• wR factor = 0.056
• Data-to-parameter ratio = 14.3

checkCIF/PLATON results

No syntax errors found



Alert level C
            Value of measurement temperature given =   298.000
            Value of melting point given =     0.000
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.98
PLAT230_ALERT_2_C Hirshfeld Test Diff for    S1     --  C9      ..       5.74 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    S2     --  C8      ..       5.68 su
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         S1
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C9
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        200 Deg.

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

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

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S1. Comment

For a considerable time, interest has focused on polymeric coordination compounds because such new coordination polymers may afford new materials with useful properties, such as catalytic activity, micro-porosity, electrical conductivity, non-linear optical activity and magnetic coupling behavior. The thiocyanide anion is a very common bridging ligand and many muti-nuclear complexes containing this ligand have been reported. Some of these complexes exhibit interesting magnetic coupling properties (Shi, Sun, Liu et al., 2006; Shi, Sun, Zhang et al., 2006)). The 2-(pyrazole-1-yl)-pyrazine molecule can act as a bridge ligand due to its structural character and up till now no crystal structures of complexes with this ligand have been reported. Under the motivation of preparing new coordination polymers containing mixed bridging ligands, we have synthesized the title coordination polymer and herein we report its crystal structure (I).

Fig. 1 shows the coordination around each independent Cd^II ion. Atom Cd1 is located on a crystallographic inversion center. In the crystal structure thiocyanade anions act as bridging ligands and connect symmetry related Cd^II ions [with Cd···Cd = 5.8122 (6)Å for Cd1···Cd2 and 5.7411 (7) Å for Cd2···Cd2ⁱⁱ; symmetry code: (ii) -x+1, -y+1, -z+1] forming an eight-membered ring which acts as a repeat unit of the structure in one-dimension [Fig. 2]. The 2-(pyrazole-1-yl)-pyrazine ligand functions as a tridentate bridging ligand and coordinates to symmetry related Cd^II ions [with a Cd···Cd separation of 7.6144 (7)Å] connecting the structure further into two-dimensions. Figure 2 also shows that in the two-dimensional structure there are two different types of rings formed by the 2-(pyrazole-1-yl)-pyrazine bridging ligand. An 18-membered ring consists of four Cd^II ions, two thiocyanato ligands and two 2-(pyrazole-1-yl)-pyrazine bridging ligands while a 26-membered ring consists of two 2-(pyrazole-1-yl)-pyrazine bridging ligands, four thiocyanade ligands and six Cd^II ions. The 18-membered rings and the 26-membered rings are arranged alternately in the two-dimensional structure.

Related literature

For background information, see: Shi, Sun, Liu et al. (2006); Shi, Sun, Zhang et al. (2006).

S2. Experimental

7 ml 3-(pyrazole-2-yloxy)-pyridine (0.0365 g, 0.250 mmol) methanol solution, 7 ml C d(ClO₄)₂6H₂O (0.1048 g, 0.250 mmol) H₂O solution and 4 ml NaSCN (0.0405 g, 0.500 mmol) H₂O solution were mixed together and stirred for a few minutes. Colorless single crystals were obtained after allowing the filtrate to stand at room temperature for four months.

S3. Refinement

All H atoms were placed in calculated positions and refined as riding with (C—H = 0.93 Å) and U_iso = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. Coordination around the two independent Cd^II ions in (I) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level [symmetry codes: (i) x-1, y+1, z (ii) -x+1, -y+1, -z+1 (iii) -x+1, -y, -z (iv) x+1, y-1, z (v) -x, -y+1, -z].
	Fig. 2. Part of the two-dimensional sheet structure of (I).

Poly[tris[µ₂-2-(pyrazol-1-yl)pyrazine]hexa-µ_1,3-thiocyanato- tricadmium(II)]

Crystal data

[Cd3(NCS)6(C7H6N4)2]	Z = 1
Mr = 978.00	F(000) = 470
Triclinic, P1	Dx = 2.111 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.0309 (9) Å	Cell parameters from 3404 reflections
b = 8.6178 (12) Å	θ = 2.6–28.2°
c = 13.7373 (18) Å	µ = 2.50 mm^−1
α = 87.889 (2)°	T = 298 K
β = 85.173 (2)°	Bar, colorless
γ = 68.060 (2)°	0.38 × 0.16 × 0.10 mm
V = 769.32 (18) Å^3

Data collection

Bruker SMART APEX CCD diffractometer	2805 independent reflections
Radiation source: fine-focus sealed tube	2625 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.013
ϕ and ω scans	θmax = 25.5°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −4→8
Tmin = 0.450, Tmax = 0.788	k = −10→10
4043 measured reflections	l = −15→16

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)] = 0.022	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.056	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0271P)^2 + 0.3586P] where P = (Fo^2 + 2Fc^2)/3
2805 reflections	(Δ/σ)max = 0.001
196 parameters	Δρmax = 0.61 e Å^−3
0 restraints	Δρmin = −0.51 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
C1	0.0009 (4)	0.7101 (4)	0.49099 (19)	0.0358 (6)
H1	0.0564	0.6478	0.5456	0.043*
C2	−0.1423 (5)	0.8730 (4)	0.4948 (2)	0.0402 (7)
H2	−0.1990	0.9378	0.5502	0.048*
C3	−0.1821 (5)	0.9178 (4)	0.4006 (2)	0.0383 (7)
H3	−0.2725	1.0200	0.3788	0.046*
C4	−0.0578 (4)	0.7640 (3)	0.24350 (18)	0.0260 (5)
C5	0.1109 (5)	0.6225 (4)	0.1068 (2)	0.0381 (7)
H5	0.2239	0.5397	0.0758	0.046*
C6	−0.0462 (5)	0.7197 (4)	0.0532 (2)	0.0388 (7)
H6	−0.0368	0.7019	−0.0137	0.047*
C7	0.5004 (4)	0.6931 (3)	0.4694 (2)	0.0312 (6)
C8	0.2476 (4)	0.1598 (3)	0.21816 (19)	0.0309 (6)
C9	0.6045 (4)	0.3004 (4)	0.1046 (2)	0.0369 (7)
C13	−0.2187 (4)	0.8625 (3)	0.18960 (19)	0.0311 (6)
H13	−0.3319	0.9454	0.2206	0.037*
Cd1	0.5000	0.0000	0.0000	0.02922 (9)
Cd2	0.35673 (3)	0.47371 (2)	0.314014 (13)	0.02935 (8)
N1	0.5156 (4)	0.6693 (3)	0.55123 (18)	0.0419 (6)
N2	0.5526 (4)	0.2304 (3)	0.04926 (19)	0.0445 (6)
N3	0.2614 (4)	0.2620 (3)	0.26533 (18)	0.0438 (6)
N4	0.1055 (3)	0.6441 (3)	0.20341 (16)	0.0298 (5)
N5	0.0489 (3)	0.6539 (3)	0.40006 (16)	0.0311 (5)
N6	−0.0646 (3)	0.7848 (3)	0.34443 (15)	0.0292 (5)
N7	−0.2124 (3)	0.8392 (3)	0.09389 (16)	0.0325 (5)
S1	0.67535 (14)	0.40534 (14)	0.18169 (7)	0.0617 (3)
S2	0.22912 (12)	0.01127 (9)	0.15191 (5)	0.03591 (17)
S3	0.47355 (13)	0.73397 (10)	0.35252 (5)	0.04143 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0406 (16)	0.0454 (16)	0.0255 (14)	−0.0200 (14)	−0.0055 (12)	0.0002 (12)
C2	0.0428 (17)	0.0477 (17)	0.0322 (15)	−0.0193 (14)	0.0024 (13)	−0.0120 (13)
C3	0.0397 (16)	0.0325 (15)	0.0388 (16)	−0.0084 (13)	−0.0025 (13)	−0.0082 (12)
C4	0.0233 (13)	0.0304 (13)	0.0244 (13)	−0.0100 (11)	−0.0017 (10)	0.0002 (10)
C5	0.0332 (15)	0.0398 (16)	0.0282 (14)	0.0017 (13)	−0.0024 (12)	−0.0046 (12)
C6	0.0380 (16)	0.0445 (16)	0.0243 (14)	−0.0040 (13)	−0.0039 (12)	−0.0001 (12)
C7	0.0316 (14)	0.0281 (13)	0.0344 (16)	−0.0105 (11)	−0.0082 (12)	−0.0009 (11)
C8	0.0312 (15)	0.0360 (15)	0.0247 (13)	−0.0121 (12)	−0.0023 (11)	0.0042 (12)
C9	0.0312 (15)	0.0371 (15)	0.0368 (16)	−0.0075 (13)	0.0061 (12)	−0.0059 (13)
C13	0.0250 (13)	0.0337 (14)	0.0285 (14)	−0.0036 (11)	−0.0035 (11)	0.0007 (11)
Cd1	0.02909 (16)	0.03095 (15)	0.02367 (15)	−0.00539 (12)	−0.00732 (11)	−0.00178 (11)
Cd2	0.02855 (12)	0.03169 (12)	0.02402 (12)	−0.00559 (9)	−0.00708 (8)	−0.00237 (8)
N1	0.0545 (16)	0.0386 (14)	0.0348 (14)	−0.0171 (12)	−0.0183 (12)	0.0057 (11)
N2	0.0539 (17)	0.0435 (15)	0.0377 (14)	−0.0203 (13)	0.0023 (12)	−0.0115 (12)
N3	0.0551 (17)	0.0472 (15)	0.0326 (13)	−0.0228 (13)	−0.0010 (12)	−0.0081 (12)
N4	0.0251 (11)	0.0327 (12)	0.0280 (12)	−0.0062 (10)	−0.0057 (9)	0.0008 (9)
N5	0.0288 (12)	0.0353 (12)	0.0266 (11)	−0.0088 (10)	−0.0045 (9)	0.0028 (9)
N6	0.0260 (11)	0.0327 (12)	0.0263 (11)	−0.0072 (9)	−0.0057 (9)	−0.0008 (9)
N7	0.0271 (12)	0.0367 (12)	0.0283 (12)	−0.0053 (10)	−0.0056 (10)	0.0032 (10)
S1	0.0419 (5)	0.0957 (7)	0.0566 (5)	−0.0359 (5)	0.0139 (4)	−0.0407 (5)
S2	0.0423 (4)	0.0402 (4)	0.0301 (4)	−0.0209 (3)	−0.0007 (3)	−0.0051 (3)
S3	0.0571 (5)	0.0523 (5)	0.0274 (4)	−0.0342 (4)	−0.0067 (3)	0.0023 (3)

Geometric parameters (Å, º)

C1—N5	1.327 (3)	C9—N2	1.148 (4)
C1—C2	1.388 (4)	C9—S1	1.639 (3)
C1—H1	0.9300	C13—N7	1.332 (3)
C2—C3	1.359 (4)	C13—H13	0.9300
C2—H2	0.9300	Cd1—N2	2.286 (3)
C3—N6	1.357 (3)	Cd1—N2^i	2.286 (3)
C3—H3	0.9300	Cd1—N7^ii	2.426 (2)
C4—N4	1.319 (3)	Cd1—N7^iii	2.426 (2)
C4—C13	1.388 (4)	Cd1—S2^i	2.6832 (8)
C4—N6	1.399 (3)	Cd1—S2	2.6832 (8)
C5—N4	1.342 (3)	Cd2—N1^iv	2.244 (2)
C5—C6	1.365 (4)	Cd2—N3	2.303 (3)
C5—H5	0.9300	Cd2—N5	2.385 (2)
C6—N7	1.331 (4)	Cd2—N4	2.436 (2)
C6—H6	0.9300	Cd2—S1	2.6603 (9)
C7—N1	1.142 (3)	Cd2—S3	2.7427 (8)
C7—S3	1.643 (3)	N1—Cd2^iv	2.244 (2)
C8—N3	1.150 (4)	N5—N6	1.364 (3)
C8—S2	1.647 (3)	N7—Cd1^v	2.426 (2)
N5—C1—C2	111.8 (3)	N7^ii—Cd1—S2	91.66 (6)
N5—C1—H1	124.1	N7^iii—Cd1—S2	88.34 (6)
C2—C1—H1	124.1	S2^i—Cd1—S2	180
C3—C2—C1	105.6 (3)	N1^iv—Cd2—N3	91.59 (9)
C3—C2—H2	127.2	N1^iv—Cd2—N5	93.71 (9)
C1—C2—H2	127.2	N3—Cd2—N5	102.07 (9)
N6—C3—C2	106.9 (3)	N1^iv—Cd2—N4	159.57 (9)
N6—C3—H3	126.6	N3—Cd2—N4	83.77 (9)
C2—C3—H3	126.6	N5—Cd2—N4	68.04 (7)
N4—C4—C13	122.2 (2)	N1^iv—Cd2—S1	105.57 (8)
N4—C4—N6	116.7 (2)	N3—Cd2—S1	94.46 (7)
C13—C4—N6	121.1 (2)	N5—Cd2—S1	154.21 (6)
N4—C5—C6	121.4 (3)	N4—Cd2—S1	94.63 (6)
N4—C5—H5	119.3	N1^iv—Cd2—S3	93.51 (7)
C6—C5—H5	119.3	N3—Cd2—S3	174.25 (7)
N7—C6—C5	121.9 (3)	N5—Cd2—S3	80.27 (6)
N7—C6—H6	119.0	N4—Cd2—S3	92.33 (6)
C5—C6—H6	119.0	S1—Cd2—S3	81.60 (3)
N1—C7—S3	178.1 (3)	C7—N1—Cd2^iv	156.4 (2)
N3—C8—S2	179.1 (3)	C9—N2—Cd1	151.9 (3)
N2—C9—S1	178.3 (3)	C8—N3—Cd2	160.7 (2)
N7—C13—C4	120.5 (2)	C4—N4—C5	116.7 (2)
N7—C13—H13	119.7	C4—N4—Cd2	116.51 (17)
C4—C13—H13	119.7	C5—N4—Cd2	126.65 (18)
N2—Cd1—N2^i	180	C1—N5—N6	104.4 (2)
N2—Cd1—N7^ii	85.94 (9)	C1—N5—Cd2	134.13 (19)
N2^i—Cd1—N7^ii	94.06 (9)	N6—N5—Cd2	112.89 (15)
N2—Cd1—N7^iii	94.06 (9)	C3—N6—N5	111.4 (2)
N2^i—Cd1—N7^iii	85.94 (9)	C3—N6—C4	129.3 (2)
N7^ii—Cd1—N7^iii	180	N5—N6—C4	119.2 (2)
N2—Cd1—S2^i	86.38 (7)	C6—N7—C13	117.2 (2)
N2^i—Cd1—S2^i	93.62 (7)	C6—N7—Cd1^v	121.71 (18)
N7^ii—Cd1—S2^i	88.34 (6)	C13—N7—Cd1^v	120.98 (18)
N7^iii—Cd1—S2^i	91.66 (6)	C9—S1—Cd2	98.65 (11)
N2—Cd1—S2	93.62 (7)	C8—S2—Cd1	101.07 (10)
N2^i—Cd1—S2	86.38 (7)	C7—S3—Cd2	96.52 (10)
N5—C1—C2—C3	−0.3 (4)	S1—Cd2—N5—C1	−110.8 (3)
C1—C2—C3—N6	−0.3 (3)	S3—Cd2—N5—C1	−64.9 (3)
N4—C5—C6—N7	−0.5 (5)	N1^iv—Cd2—N5—N6	169.76 (17)
N4—C4—C13—N7	−0.5 (4)	N3—Cd2—N5—N6	−97.82 (18)
N6—C4—C13—N7	−178.6 (2)	N4—Cd2—N5—N6	−19.70 (16)
N7^ii—Cd1—N2—C9	−30.1 (5)	S1—Cd2—N5—N6	30.9 (3)
N7^iii—Cd1—N2—C9	149.9 (5)	S3—Cd2—N5—N6	76.83 (17)
S2^i—Cd1—N2—C9	−118.7 (5)	C2—C3—N6—N5	0.7 (3)
S2—Cd1—N2—C9	61.3 (5)	C2—C3—N6—C4	176.0 (3)
N1^iv—Cd2—N3—C8	−124.3 (8)	C1—N5—N6—C3	−0.9 (3)
N5—Cd2—N3—C8	141.6 (8)	Cd2—N5—N6—C3	−153.58 (19)
N4—Cd2—N3—C8	75.7 (8)	C1—N5—N6—C4	−176.7 (2)
S1—Cd2—N3—C8	−18.5 (8)	Cd2—N5—N6—C4	30.6 (3)
C13—C4—N4—C5	0.9 (4)	N4—C4—N6—C3	162.2 (3)
N6—C4—N4—C5	179.1 (3)	C13—C4—N6—C3	−19.5 (4)
C13—C4—N4—Cd2	−175.6 (2)	N4—C4—N6—N5	−22.8 (3)
N6—C4—N4—Cd2	2.7 (3)	C13—C4—N6—N5	155.5 (2)
C6—C5—N4—C4	−0.4 (4)	C5—C6—N7—C13	1.0 (5)
C6—C5—N4—Cd2	175.7 (2)	C5—C6—N7—Cd1^v	−176.2 (2)
N1^iv—Cd2—N4—C4	37.2 (3)	C4—C13—N7—C6	−0.5 (4)
N3—Cd2—N4—C4	114.9 (2)	C4—C13—N7—Cd1^v	176.70 (19)
N5—Cd2—N4—C4	9.15 (18)	N1^iv—Cd2—S1—C9	113.39 (13)
S1—Cd2—N4—C4	−151.14 (18)	N3—Cd2—S1—C9	20.49 (14)
S3—Cd2—N4—C4	−69.38 (19)	N5—Cd2—S1—C9	−109.59 (17)
N1^iv—Cd2—N4—C5	−138.9 (3)	N4—Cd2—S1—C9	−63.61 (13)
N3—Cd2—N4—C5	−61.2 (3)	S3—Cd2—S1—C9	−155.29 (12)
N5—Cd2—N4—C5	−166.9 (3)	N2—Cd1—S2—C8	−7.34 (12)
S1—Cd2—N4—C5	32.8 (2)	N2^i—Cd1—S2—C8	172.66 (12)
S3—Cd2—N4—C5	114.6 (2)	N7^ii—Cd1—S2—C8	78.70 (11)
C2—C1—N5—N6	0.7 (3)	N7^iii—Cd1—S2—C8	−101.30 (11)
C2—C1—N5—Cd2	144.6 (2)	N1^iv—Cd2—S3—C7	−19.29 (12)
N1^iv—Cd2—N5—C1	28.0 (3)	N5—Cd2—S3—C7	73.89 (11)
N3—Cd2—N5—C1	120.4 (3)	N4—Cd2—S3—C7	141.13 (11)
N4—Cd2—N5—C1	−161.5 (3)	S1—Cd2—S3—C7	−124.53 (11)

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