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Journal logoCRYSTALLOGRAPHIC
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ISSN: 2056-9890
Volume 71| Part 4| April 2015| Pages 374-376

Crystal structure of the co-crystal fac-tri­aqua­tris­(thio­cyanato-κN)iron(III)–2,3-di­methyl­pyrazine (1/3)

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aDepartment of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska st. 64, Kyiv 01601, Ukraine, bKherson National Technical University, Beryslavske st. 24, Kherson 73008, Ukraine, and cInstitute of Inorganic Chemistry, Georg-August-University Göttingen, Tammannstrasse 4, Göttingen D-37077, Germany
*Correspondence e-mail: lesya.kucheriv@gmail.com

Edited by D.-J. Xu, Zhejiang University (Yuquan Campus), China (Received 3 March 2015; accepted 9 March 2015; online 18 March 2015)

In the crystal of the title compound, [Fe(NCS)3(H2O)3]·3C6H8N2, the FeIII cation is located on a threefold rotation axis and is coordinated by three N atoms of the thiocyanate anions and three water mol­ecules in a fac arrangement, forming a slightly distorted N3O3 octa­hedron. Stabilization within the crystal structure is provided by O—H⋯N hydrogen bonds; the H atoms from coordinating water mol­ecules act as donors to the N atoms of guest 2,3-di­methyl­pyrazine mol­ecules, leading to a three-dimensional supra­molecular framework.

1. Chemical context

In the large family of coordination compounds, materials showing a tunable character of their physical properties (e.g., electrical, magnetic, optical etc) are of special inter­est. Attempts to design compounds with such tunability have revealed the possibility to target the property of inter­est through the rational choice of ligands in transition metal complexes. For instance, variation of the aromatic N-donor ligand can lead to possible spin-state modulation of transition metals. In certain cases, these complexes can even possess spin crossover behaviour (transition between low and high spin states of a metal). The phenomenon of spin transition, which is one of the most known examples of mol­ecular bis­tability, can be provoked by some external stimuli (temperature, pressure, light, magnetic field, absorption of some compounds) and is followed by a change of the optical, magnetic and electric properties (Gütlich & Goodwin, 2004[Gütlich, P. & Goodwin, H. (2004). Spin Crossover in Transition Metal Compounds I, pp. 1-47. Berlin, Heidelberg: Springer-Verlag.]).

[Scheme 1]

One of the simplest bridging N-donor ligands in the design of coordination polymers is pyrazine. This ligand is known for the formation of not only low-dimensional chains and sheets but also of some more complicated architectures, such as [Ag(pz)](CB11H12) [CB11H12 is the monocarba-closo-dodeca­borate(−) anion], which exhibits a three-dimensional structure made up of checkerboard sheets of silver cations and anions connected by pillars of bridging pyrazine ligands (Cunha-Silva et al., 2006[Cunha-Silva, L., Ahmad, R. & Hardie, M. J. (2006). Aust. J. Chem. 59, 40-48.]). In addition, pyrazine is able to construct Hofmann clathrates – spin crossover compounds with general formula [FeIIMII (pz)(CN)4] where M = Ni, Pd or Pt (Niel et al., 2001[Niel, V., Martinez-Agudo, J. M., Muñoz, M. C., Gaspar, A. B. & Real, J. A. (2001). Inorg. Chem. 40, 3838-3839.]). A combination of pyrazine ligands with thiocyanates instead of tetracyanidometalates leads to the two-dimensional coordin­ation polymer [Fe(pz)2(NCS)2] with an anti­ferromagnetic exchange between the metal cations (Real et al., 1991[Real, J. A., De Munno, G., Munoz, M. C. & Julve, M. (1991). Inorg. Chem. 30, 2701-2704.]). In this context, we attempted to synthesize an FeII thio­cyanate complex with 2,3-di­methyl­pyrazine; however, the exposure of the starting material [Fe(OTs)2]·6H2O (OTs = p-toluene­sulfonate) to the oxygen in the air led to the oxidation of FeII and to the formation of the title compound.

2. Structural commentary

In the crystal structure of the title compound, the FeIII cation is located on a threefold rotation axis and is in an octa­hedral coordination environment formed by three N atoms of the thio­cyanate anions and three O atoms of water mol­ecules arranged in a fac configuration (Fig. 1[link]). The distance between the FeIII ion and the N atoms [2.025 (4) Å] is longer than that between the FeIII ion and the O atoms [2.034 (3) Å] and therefore the FeN3O3 octa­hedron is slightly distorted. These structural features are typical for related compounds (Shylin et al., 2013[Shylin, S. I., Gural'skiy, I. A., Haukka, M. & Golenya, I. A. (2013). Acta Cryst. E69, m280.], 2015[Shylin, S. I., Gural'skiy, I. A., Bykov, D., Demeshko, S., Dechert, S., Meyer, F., Hauka, M. & Fritsky, I. O. (2015). Polyhedron, 87, 147-155.]). The thio­cyanate ligands are bound through nitro­gen atoms and are quasi-linear [N1—C1—S1 = 179.5 (4)°], while the Fe–NCS linkages are bent [C1—N1—Fe1 = 157.0 (4)°]. Previously reported complexes with an N-bound NCS group possess similar structural features (Petrusenko et al., 1997[Petrusenko, S. R., Kokozay, V. N. & Fritsky, I. O. (1997). Polyhedron, 16, 267-274.]).

[Figure 1]
Figure 1
The mol­ecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. [Symmetry codes: (i) −y + 1, x − y + 1, z; (ii) −x + y, −x + 1, z.]

3. Supra­molecular features

In the title compound, the crystal packing is stabilized by O—H⋯N hydrogen bonds (Table 1[link]): the H atoms from coordin­ating water mol­ecules act as donors to the N atoms of guest 2,3-di­methyl­pyrazine mol­ecules. The compound contains three guest mol­ecules of pyrazine per FeIII cation. In the crystal lattice, each mol­ecule of the complex is attached to six mol­ecules of pyrazine, while each pyrazine is connected with two water mol­ecules of the host complexes, leading to the formation of a three-dimensional network (Fig. 2[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1A⋯N2 0.80 (3) 1.95 (3) 2.745 (4) 172 (8)
[Figure 2]
Figure 2
Crystal structure of the title compound, showing hydrogen bonds as dashed lines. H atoms not involved in hydrogen bonding have been omitted for clarity. Colour key: bronze Fe, yellow S, blue N, grey C and red O.

4. Synthesis and crystallization

Crystals of the title compound were obtained by the slow-diffusion method between three layers, the first layer being a solution of [Fe(OTs)2]·6H2O (0.096 g, 0.2 mmol) and NH4SCN (0.046 g, 0.6 mmol) in water (10 ml), the second being a water/methanol mixture (1/1, 10 ml) and the third a solution of 2,3-di­methyl­pyrazine (0.065 g, 0.6 mmol) in methanol (3 ml). After two weeks, red plates grew in the second layer; they were collected, washed with water and dried in air, yield 0.028 g (23%).

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All hydrogen atoms connected to C and O atoms were placed in their expected calculated positions and refined as riding with C—H = 0.98 (CH3), 0.95 (Carom), O—H = 0.80 (3) Å, and with Uiso(H) = 1.2Uiso(C) with the exception of methyl hydrogen atoms, which were refined with Uiso(H) = 1.5Ueq(C).

Table 2
Experimental details

Crystal data
Chemical formula [Fe(NCS)3(H2O)3]·3C6H8N2
Mr 608.57
Crystal system, space group Trigonal, R3c
Temperature (K) 133
a, c (Å) 16.9383 (12), 17.6259 (13)
V3) 4379.5 (7)
Z 6
Radiation type Mo Kα
μ (mm−1) 0.77
Crystal size (mm) 0.16 × 0.12 × 0.1
 
Data collection
Diffractometer Stoe IPDS II
Absorption correction Numerical (X-RED; Stoe & Cie, 2002[Stoe & Cie (2002). X-RED and X-AREA. Stoe & Cie, Darmstadt, Germany.])
Tmin, Tmax 0.908, 0.939
No. of measured, independent and observed [I > 2σ(I)] reflections 5784, 1903, 1716
Rint 0.058
(sin θ/λ)max−1) 0.633
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.038, 0.070, 1.07
No. of reflections 1903
No. of parameters 120
No. of restraints 3
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.27, −0.28
Absolute structure Flack x determined using 685 quotients [(I+)−(I)]/[(I+)+(I)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])
Absolute structure parameter −0.03 (3)
Computer programs: X-AREA and X-RED (Stoe & Cie, 2002[Stoe & Cie (2002). X-RED and X-AREA. Stoe & Cie, Darmstadt, Germany.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Computing details top

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA (Stoe & Cie, 2002); data reduction: X-RED (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

fac-Triaquatris(thiocyanato-κN)iron(III)–2,3-dimethylpyrazine (1/3) top
Crystal data top
[Fe(NCS)3(H2O)3]·3C6H8N2F(000) = 1902
Mr = 608.57Dx = 1.384 Mg m3
Trigonal, R3cMo Kα radiation, λ = 0.71073 Å
a = 16.9383 (12) ŵ = 0.77 mm1
c = 17.6259 (13) ÅT = 133 K
V = 4379.5 (7) Å3Block, red
Z = 60.16 × 0.12 × 0.1 mm
Data collection top
Stoe IPDS II
diffractometer
1716 reflections with I > 2σ(I)
φ scans and ω scans with κ offsetRint = 0.058
Absorption correction: numerical
(X-RED; Stoe & Cie, 2002)
θmax = 26.8°, θmin = 2.4°
Tmin = 0.908, Tmax = 0.939h = 1821
5784 measured reflectionsk = 2115
1903 independent reflectionsl = 1822
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.038H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.070 w = 1/[σ2(Fo2) + (0.0297P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max < 0.001
1903 reflectionsΔρmax = 0.27 e Å3
120 parametersΔρmin = 0.28 e Å3
3 restraintsAbsolute structure: Flack x determined using 685 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.03 (3)
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Fe10.33330.66670.99891 (7)0.0201 (2)
S10.29300 (8)0.86373 (8)1.16318 (7)0.0300 (3)
N10.2860 (3)0.7347 (3)1.0611 (2)0.0297 (9)
O10.2256 (2)0.62277 (19)0.92686 (19)0.0221 (6)
C10.2893 (3)0.7891 (3)1.1041 (3)0.0238 (9)
N20.0562 (2)0.5854 (2)0.9750 (2)0.0250 (8)
N30.1220 (2)0.5016 (2)1.0276 (2)0.0254 (8)
C20.0336 (3)0.5471 (3)1.0439 (3)0.0299 (10)
H20.07960.54811.07530.036*
C30.0543 (3)0.5064 (3)1.0704 (3)0.0288 (10)
H30.06740.48121.12010.035*
C40.1008 (3)0.5385 (3)0.9586 (2)0.0235 (9)
C50.0099 (3)0.5815 (3)0.9318 (3)0.0229 (9)
C60.1766 (3)0.5322 (3)0.9107 (3)0.0322 (10)
H6A0.23450.49770.93790.048*
H6B0.17950.50100.86300.048*
H6C0.16550.59360.89960.048*
C70.0144 (3)0.6246 (3)0.8553 (3)0.0304 (10)
H7A0.07950.64840.84590.046*
H7B0.00120.67470.85310.046*
H7C0.02140.57910.81660.046*
H1A0.179 (3)0.617 (5)0.943 (4)0.080*
H1B0.206 (5)0.572 (3)0.912 (4)0.080*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Fe10.0197 (3)0.0197 (3)0.0209 (5)0.00986 (13)0.0000.000
S10.0320 (6)0.0293 (5)0.0316 (6)0.0175 (5)0.0009 (5)0.0061 (5)
N10.030 (2)0.031 (2)0.029 (2)0.0157 (18)0.0031 (17)0.0024 (18)
O10.0180 (14)0.0201 (14)0.0283 (17)0.0096 (13)0.0011 (13)0.0021 (13)
C10.022 (2)0.030 (2)0.022 (2)0.0141 (18)0.0019 (17)0.0053 (18)
N20.0234 (18)0.0234 (17)0.028 (2)0.0119 (15)0.0004 (16)0.0026 (15)
N30.0236 (17)0.0233 (17)0.029 (2)0.0113 (15)0.0027 (15)0.0001 (15)
C20.027 (2)0.037 (2)0.030 (3)0.019 (2)0.0040 (19)0.001 (2)
C30.032 (2)0.029 (2)0.028 (3)0.018 (2)0.0022 (19)0.0030 (19)
C40.021 (2)0.023 (2)0.027 (2)0.0113 (16)0.0008 (18)0.0022 (18)
C50.023 (2)0.0203 (19)0.027 (2)0.0121 (17)0.0023 (17)0.0028 (17)
C60.027 (2)0.036 (3)0.035 (3)0.017 (2)0.002 (2)0.002 (2)
C70.026 (2)0.037 (2)0.028 (3)0.016 (2)0.0020 (19)0.0020 (19)
Geometric parameters (Å, º) top
Fe1—N12.025 (4)N3—C41.333 (6)
Fe1—N1i2.025 (4)C2—H20.9500
Fe1—N1ii2.025 (4)C2—C31.372 (6)
Fe1—O12.034 (3)C3—H30.9500
Fe1—O1i2.034 (3)C4—C51.415 (6)
Fe1—O1ii2.034 (3)C4—C61.495 (6)
S1—C11.615 (5)C5—C71.491 (6)
N1—C11.172 (6)C6—H6A0.9800
O1—H1A0.80 (3)C6—H6B0.9800
O1—H1B0.80 (3)C6—H6C0.9800
N2—C21.339 (6)C7—H7A0.9800
N2—C51.329 (5)C7—H7B0.9800
N3—C31.340 (6)C7—H7C0.9800
N1—Fe1—N1i93.42 (17)N2—C2—C3121.9 (4)
N1—Fe1—N1ii93.42 (17)C3—C2—H2119.0
N1i—Fe1—N1ii93.42 (16)N3—C3—C2121.2 (5)
N1—Fe1—O1ii90.67 (14)N3—C3—H3119.4
N1ii—Fe1—O1ii90.47 (14)C2—C3—H3119.4
N1ii—Fe1—O1i90.67 (14)N3—C4—C5120.9 (4)
N1i—Fe1—O1ii174.17 (17)N3—C4—C6117.6 (4)
N1—Fe1—O190.47 (14)C5—C4—C6121.5 (4)
N1i—Fe1—O1i90.47 (14)N2—C5—C4120.5 (4)
N1ii—Fe1—O1174.17 (17)N2—C5—C7118.3 (4)
N1i—Fe1—O190.67 (14)C4—C5—C7121.2 (4)
N1—Fe1—O1i174.17 (17)C4—C6—H6A109.5
O1—Fe1—O1ii85.15 (14)C4—C6—H6B109.5
O1ii—Fe1—O1i85.15 (14)C4—C6—H6C109.5
O1—Fe1—O1i85.15 (14)H6A—C6—H6B109.5
C1—N1—Fe1157.0 (4)H6A—C6—H6C109.5
Fe1—O1—H1A118 (6)H6B—C6—H6C109.5
Fe1—O1—H1B115 (6)C5—C7—H7A109.5
H1A—O1—H1B98 (7)C5—C7—H7B109.5
N1—C1—S1179.5 (4)C5—C7—H7C109.5
C5—N2—C2117.7 (4)H7A—C7—H7B109.5
C4—N3—C3117.7 (4)H7A—C7—H7C109.5
N2—C2—H2119.0H7B—C7—H7C109.5
N2—C2—C3—N31.5 (7)C3—N3—C4—C6179.4 (4)
N3—C4—C5—N20.4 (6)C4—N3—C3—C20.7 (7)
N3—C4—C5—C7178.7 (4)C5—N2—C2—C31.2 (6)
C2—N2—C5—C40.3 (6)C6—C4—C5—N2179.2 (4)
C2—N2—C5—C7179.5 (4)C6—C4—C5—C71.7 (6)
C3—N3—C4—C50.2 (6)
Symmetry codes: (i) y+1, xy+1, z; (ii) x+y, x+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1A···N20.80 (3)1.95 (3)2.745 (4)172 (8)
 

Acknowledgements

SIS and IAG acknowledge DAAD fellowships and the hosting of Professor F. Meyer's group.

References

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ISSN: 2056-9890
Volume 71| Part 4| April 2015| Pages 374-376
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