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

Kucheriv, O.I.; Shylin, S.I.; Ilina, T.A.; Dechert, S.; Gural'skiy, I.A.

doi:10.1107/S2056989015004831

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ISSN: 2056-9890

Volume 71| Part 4| April 2015| Pages 374-376

doi:10.1107/S2056989015004831

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

Olesia I. Kucheriv,^a ^* Sergii I. Shylin,^a Tetiana A. Ilina,^b Sebastian Dechert ^c and Il'ya A. Gural'skiy ^a

^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 Fe^III 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.

Keywords: crystal structure; Fe^III complex; isothiocyanate ligand; pyrazine; co-crystal; hydrogen bonding.

CCDC reference: 1053032

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 ).

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 ). In addition, pyrazine is able to construct Hofmann clathrates – spin crossover compounds with general formula [Fe^IIM^II (pz)(CN)₄]_∞ where M = Ni, Pd or Pt (Niel et al., 2001 ). 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 ). In this context, we attempted to synthesize an Fe^II 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 Fe^II and to the formation of the title compound.

2. Structural commentary

In the crystal structure of the title compound, the Fe^III 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). The distance between the Fe^III ion and the N atoms [2.025 (4) Å] is longer than that between the Fe^III 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 , 2015 ). 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 ).

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): 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 Fe^III 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).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1A⋯N2	0.80 (3)	1.95 (3)	2.745 (4)	172 (8)

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. 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 (C_arom), O—H = 0.80 (3) Å, and with U_iso(H) = 1.2U_iso(C) with the exception of methyl hydrogen atoms, which were refined with U_iso(H) = 1.5U_eq(C).

Table 2
Experimental details

Crystal data
Chemical formula	[Fe(NCS)₃(H₂O)₃]·3C₆H₈N₂
M_r	608.57
Crystal system, space group	Trigonal, R3c
Temperature (K)	133
a, c (Å)	16.9383 (12), 17.6259 (13)
V (Å³)	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 )
T_min, T_max	0.908, 0.939
No. of measured, independent and observed [I > 2σ(I)] reflections	5784, 1903, 1716
R_int	0.058
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	0.27, −0.28
Absolute structure	Flack x determined using 685 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	−0.03 (3)
Computer programs: X-AREA and X-RED (Stoe & Cie, 2002), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), OLEX2 (Dolomanov et al., 2009 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1053032

Crystal structure: contains datablocks global, I. DOI: 10.1107/S2056989015004831/xu5840sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S2056989015004831/xu5840Isup2.hkl

checkCIF report

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]·3C₆H₈N₂	F(000) = 1902
M_r = 608.57	D_x = 1.384 Mg m⁻³
Trigonal, R3c	Mo Kα radiation, λ = 0.71073 Å
a = 16.9383 (12) Å	µ = 0.77 mm⁻¹
c = 17.6259 (13) Å	T = 133 K
V = 4379.5 (7) Å³	Block, red
Z = 6	0.16 × 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 offset	R_int = 0.058
Absorption correction: numerical (X-RED; Stoe & Cie, 2002)	θ_max = 26.8°, θ_min = 2.4°
T_min = 0.908, T_max = 0.939	h = −18→21
5784 measured reflections	k = −21→15
1903 independent reflections	l = −18→22

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.070	w = 1/[σ²(F_o²) + (0.0297P)²] where P = (F_o² + 2F_c²)/3
S = 1.07	(Δ/σ)_max < 0.001
1903 reflections	Δρ_max = 0.27 e Å⁻³
120 parameters	Δρ_min = −0.28 e Å⁻³
3 restraints	Absolute structure: Flack x determined using 685 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute 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

	x	y	z	U_iso*/U_eq
Fe1	0.3333	0.6667	0.99891 (7)	0.0201 (2)
S1	0.29300 (8)	0.86373 (8)	1.16318 (7)	0.0300 (3)
N1	0.2860 (3)	0.7347 (3)	1.0611 (2)	0.0297 (9)
O1	0.2256 (2)	0.62277 (19)	0.92686 (19)	0.0221 (6)
C1	0.2893 (3)	0.7891 (3)	1.1041 (3)	0.0238 (9)
N2	0.0562 (2)	0.5854 (2)	0.9750 (2)	0.0250 (8)
N3	−0.1220 (2)	0.5016 (2)	1.0276 (2)	0.0254 (8)
C2	0.0336 (3)	0.5471 (3)	1.0439 (3)	0.0299 (10)
H2	0.0796	0.5481	1.0753	0.036*
C3	−0.0543 (3)	0.5064 (3)	1.0704 (3)	0.0288 (10)
H3	−0.0674	0.4812	1.1201	0.035*
C4	−0.1008 (3)	0.5385 (3)	0.9586 (2)	0.0235 (9)
C5	−0.0099 (3)	0.5815 (3)	0.9318 (3)	0.0229 (9)
C6	−0.1766 (3)	0.5322 (3)	0.9107 (3)	0.0322 (10)
H6A	−0.2345	0.4977	0.9379	0.048*
H6B	−0.1795	0.5010	0.8630	0.048*
H6C	−0.1655	0.5936	0.8996	0.048*
C7	0.0144 (3)	0.6246 (3)	0.8553 (3)	0.0304 (10)
H7A	0.0795	0.6484	0.8459	0.046*
H7B	0.0012	0.6747	0.8531	0.046*
H7C	−0.0214	0.5791	0.8166	0.046*
H1A	0.179 (3)	0.617 (5)	0.943 (4)	0.080*
H1B	0.206 (5)	0.572 (3)	0.912 (4)	0.080*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Fe1	0.0197 (3)	0.0197 (3)	0.0209 (5)	0.00986 (13)	0.000	0.000
S1	0.0320 (6)	0.0293 (5)	0.0316 (6)	0.0175 (5)	0.0009 (5)	−0.0061 (5)
N1	0.030 (2)	0.031 (2)	0.029 (2)	0.0157 (18)	0.0031 (17)	−0.0024 (18)
O1	0.0180 (14)	0.0201 (14)	0.0283 (17)	0.0096 (13)	−0.0011 (13)	−0.0021 (13)
C1	0.022 (2)	0.030 (2)	0.022 (2)	0.0141 (18)	0.0019 (17)	0.0053 (18)
N2	0.0234 (18)	0.0234 (17)	0.028 (2)	0.0119 (15)	−0.0004 (16)	−0.0026 (15)
N3	0.0236 (17)	0.0233 (17)	0.029 (2)	0.0113 (15)	0.0027 (15)	0.0001 (15)
C2	0.027 (2)	0.037 (2)	0.030 (3)	0.019 (2)	−0.0040 (19)	−0.001 (2)
C3	0.032 (2)	0.029 (2)	0.028 (3)	0.018 (2)	0.0022 (19)	0.0030 (19)
C4	0.021 (2)	0.023 (2)	0.027 (2)	0.0113 (16)	0.0008 (18)	−0.0022 (18)
C5	0.023 (2)	0.0203 (19)	0.027 (2)	0.0121 (17)	0.0023 (17)	−0.0028 (17)
C6	0.027 (2)	0.036 (3)	0.035 (3)	0.017 (2)	−0.002 (2)	−0.002 (2)
C7	0.026 (2)	0.037 (2)	0.028 (3)	0.016 (2)	0.0020 (19)	0.0020 (19)

Geometric parameters (Å, º) top

Fe1—N1	2.025 (4)	N3—C4	1.333 (6)
Fe1—N1ⁱ	2.025 (4)	C2—H2	0.9500
Fe1—N1ⁱⁱ	2.025 (4)	C2—C3	1.372 (6)
Fe1—O1	2.034 (3)	C3—H3	0.9500
Fe1—O1ⁱ	2.034 (3)	C4—C5	1.415 (6)
Fe1—O1ⁱⁱ	2.034 (3)	C4—C6	1.495 (6)
S1—C1	1.615 (5)	C5—C7	1.491 (6)
N1—C1	1.172 (6)	C6—H6A	0.9800
O1—H1A	0.80 (3)	C6—H6B	0.9800
O1—H1B	0.80 (3)	C6—H6C	0.9800
N2—C2	1.339 (6)	C7—H7A	0.9800
N2—C5	1.329 (5)	C7—H7B	0.9800
N3—C3	1.340 (6)	C7—H7C	0.9800

N1—Fe1—N1ⁱ	93.42 (17)	N2—C2—C3	121.9 (4)
N1—Fe1—N1ⁱⁱ	93.42 (17)	C3—C2—H2	119.0
N1ⁱ—Fe1—N1ⁱⁱ	93.42 (16)	N3—C3—C2	121.2 (5)
N1—Fe1—O1ⁱⁱ	90.67 (14)	N3—C3—H3	119.4
N1ⁱⁱ—Fe1—O1ⁱⁱ	90.47 (14)	C2—C3—H3	119.4
N1ⁱⁱ—Fe1—O1ⁱ	90.67 (14)	N3—C4—C5	120.9 (4)
N1ⁱ—Fe1—O1ⁱⁱ	174.17 (17)	N3—C4—C6	117.6 (4)
N1—Fe1—O1	90.47 (14)	C5—C4—C6	121.5 (4)
N1ⁱ—Fe1—O1ⁱ	90.47 (14)	N2—C5—C4	120.5 (4)
N1ⁱⁱ—Fe1—O1	174.17 (17)	N2—C5—C7	118.3 (4)
N1ⁱ—Fe1—O1	90.67 (14)	C4—C5—C7	121.2 (4)
N1—Fe1—O1ⁱ	174.17 (17)	C4—C6—H6A	109.5
O1—Fe1—O1ⁱⁱ	85.15 (14)	C4—C6—H6B	109.5
O1ⁱⁱ—Fe1—O1ⁱ	85.15 (14)	C4—C6—H6C	109.5
O1—Fe1—O1ⁱ	85.15 (14)	H6A—C6—H6B	109.5
C1—N1—Fe1	157.0 (4)	H6A—C6—H6C	109.5
Fe1—O1—H1A	118 (6)	H6B—C6—H6C	109.5
Fe1—O1—H1B	115 (6)	C5—C7—H7A	109.5
H1A—O1—H1B	98 (7)	C5—C7—H7B	109.5
N1—C1—S1	179.5 (4)	C5—C7—H7C	109.5
C5—N2—C2	117.7 (4)	H7A—C7—H7B	109.5
C4—N3—C3	117.7 (4)	H7A—C7—H7C	109.5
N2—C2—H2	119.0	H7B—C7—H7C	109.5

N2—C2—C3—N3	1.5 (7)	C3—N3—C4—C6	179.4 (4)
N3—C4—C5—N2	0.4 (6)	C4—N3—C3—C2	−0.7 (7)
N3—C4—C5—C7	−178.7 (4)	C5—N2—C2—C3	−1.2 (6)
C2—N2—C5—C4	0.3 (6)	C6—C4—C5—N2	−179.2 (4)
C2—N2—C5—C7	179.5 (4)	C6—C4—C5—C7	1.7 (6)
C3—N3—C4—C5	−0.2 (6)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···N2	0.80 (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.

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