Crystal structure of high-spin tetra­aqua­bis­(2-chloro­pyrazine-κN ⁴)iron(II) bis­(4-methyl­benzene­sulfonate)

Between the tosyl­ate anions and the octa­hedral complex cations consisting of Fe^II, four aqua and two N-bound 2-chloro­pyrazine ligands, weak O—H⋯O as well as π–π inter­actions play important roles in the mol­ecular self-assembly, resulting in the formation of a three-dimensional structure.

Abstract

The title salt, [Fe^II(C₄H₃ClN₂)₂(H₂O)₄](C₇H₇O₃S)₂, contains a complex cation with point group symmetry 2/m. The high-spin Fe^II cation is hexa­coordinated by four symmetry-related water and two N-bound 2-chloro­pyrazine mol­ecules in a trans arrangement, forming a distorted FeN₂O₄ octa­hedron. The three-dimensional supra­molecular structure is supported by inter­molecular O—H⋯O hydrogen bonds between the complex cations and tosyl­ate anions, and additional π–π inter­actions between benzene and pyrazine rings. The methyl H atoms of the tosyl­ate anion are equally disordered over two positions.

Chemical context  

Transition metal complexes containing pyrazine or substituted pyrazines as ligands are of current inter­est due to their supra­molecular arrangements and the probability of being spin-crossover compounds. Spin crossover, sometimes referred to as a spin transition or a spin equilibrium behaviour, is a phenomenon that occurs in some metal complexes wherein the spin state of a compound changes via influence of external stimuli such as temperature, pressure, light irradiation, magnetic field or guest effects (Gütlich & Goodwin, 2004 ▸). As a result of the appearance of such features as thermochromic effects, magnetic susceptibility changes, changes of cell volume, etc. that accompany the mol­ecular switching between high-spin and low-spin states, they can be applied in the development of micro-thermometers and photonic devices (Gural’skiy et al., 2012 ▸).

Aromatic ligands bearing two or more N atoms are known for their ability to form different coordination polymers and mol­ecular complexes. Thus, a number of mononuclear high-spin Fe^II complexes with substituted pyrazines have been reported recently (Shylin et al., 2015 ▸). These heterocyclic ligands are also known for their ability to create three-dimensional metal-organic framework structures, so called analogues of Hofmann clathrates with general formula {Fe(L)_x[M_y(CN)_z]}_∞ where M = Ni, Pd, Pt, etc. Series of thio­cyanato coordination polymers [M(NCS)₂ L ₂]_∞ (with M = Mn, Fe, Co, Ni, and L = pyrazine) in which the small-sized thiocyanate anions are terminally N-bound and therefore not involved in any magnetic exchange interactions are also known (Wriedt & Näther, 2011 ▸). Although 2-chloro­pyrazine could possess a N,N′-manner of coordination, it is frequently found to act as a monodentate ligand due to the bulky chlorine atom being in direct proximity to one of the nitro­gen atoms (Wöhlert & Näther, 2013 ▸).

In this paper, we report on the crystal structure of [Fe^II(C₄H₃ClN₂)₂(H₂O)₄](C₇H₇O₃S)₂ containing a cationic iron(II) complex with 2-chloro­pyrazine and aqua ligands, and tosyl­ate as an anion.

Structural commentary  

The structure of the title compound consists of a complex cation [Fe(2-chloro­pyrazine)₂(H₂O)₄]²⁺ and two tosyl­ate anions. The Fe^II atom, located on a special position with site symmetry 2/m, is sixfold coordinated by two N atoms of two symmetry-related 2-chloro­pyrazine ligands occupying the axial positions and four O atoms of four H₂O mol­ecules forming the equatorial plane (Fig. 1 ▸). The distances between Fe^II and the O atoms [2.1004 (14) Å] of the H₂O mol­ecules are significantly shorter than those between Fe^II and N [2.200 (2) Å] atoms of the two 2-chloro­pyrazine ligands, hence the resulting FeO₄N₂ octa­hedron is distorted. The metal-to-ligand distances clearly signalize the high-spin nature of the complex described in here (Shylin et al., 2015 ▸). Similar structural features have been reported for other related compounds (Shylin et al., 2013 ▸). The angles between the coordinating O atoms [O1ⁱ—Fe1—O1ⁱⁱⁱ = 90.83 (11)°; for symmetry codes see caption to Fig. 1 ▸], and coordinating N and O atoms [O1ⁱⁱ—Fe1—N1 = 90.68 (5)°] indicate only a small angular distortion.

Figure 1.

The structure of the cationic and anionic components in the title salt. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are indicated by dashed lines. [Symmetry codes: (i) 1 − x, −y, 1 − z; (ii) 1 − x, y, 1 − z; (iii) x, −y, z; (iv) x, 1 − y, z; (v) 1 − x, −1 + y, 1 − z.]

Supra­molecular features  

In the title compound, the crystal packing is stabilized by O1—H1A⋯O2 and O1—H1B⋯O3ⁱ hydrogen bonds (Table 1 ▸) between the complex cations and the counter-anions (Figs. 1 ▸ and 2 ▸). Only two O atoms of the tosyl­ate anion are involved in hydrogen bonding. Additional π –π stacking inter­actions (for numerical details, see: Table 2 ▸) between the pyrazine and benzene rings of the tosyl­ate anion contribute to the stabilization (Fritsky et al., 2004 ▸) of the three-dimensional network (Fig. 2 ▸).

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
O1H1AO2	0.82(2)	1.91(2)	2.7238(19)	171(4)
O1H1BO3i	0.81(2)	1.95(2)	2.7624(19)	177(3)

Symmetry code: (i) .

Figure 2.

The crystal structure of the title compound, showing hydrogen bonds as dashed cyan lines and π–π contacts as green lines. Colour key: orange Fe, yellow S, blue N, grey C, green Cl, red O and white H.

Table 2. Geometric parameters of stacking (, ).

centroid (2-chloropyrazine)centroid (tosylate anion)	3.7098(1)
centroid (2-chloropyrazine)centroid (tosylate anion)centroid (2-chloropyrazine)	130.283(1)

Synthesis and crystallization  

Crystals of the title compound were obtained by adding 2-chloro­pyrazine (0.046 g, 0.4 mmol) to Fe(OTs)₂·6H₂O (0.096 g, 0.2 mmol) (OTs = p-toluene­sulfonate) and ascorbic acid (0.001 g) in water (5 ml). After seven days this yielded colourless blocks of the title compound that were collected, washed with water and dried in air. Yield 0.090 g (64%).

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. All non-water H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C—H) = 0.95 Å for aromatic and 0.98 Å for CH₃ hydrogen atoms. Because of the symmetry of the complete complex cation, methyl H atoms were modelled as equally disordered over two sets of sites. The H atoms of the water mol­ecule were located from a difference Fourier map and were modelled with a common isotropic displacement parameter fixed at 0.08 Ų. The O—H bonds lengths were constrained to 0.82 Å. The U _iso values were constrained to be 1.5U _eq of the carrier atom for methyl H atoms and 1.2U _eq for the remaining H atoms.

Table 3. Experimental details.

Crystal data
Chemical formula	[Fe(C4H3ClN2)2(H2O)4](C7H7O3S)2
M r	699.35
Crystal system, space group	Monoclinic, C2/m
Temperature (K)	133
a, b, c ()	30.691(3), 6.7321(3), 6.9435(6)
()	99.811(7)
V (3)	1413.63(19)
Z	2
Radiation type	Mo K
(mm1)	0.93
Crystal size (mm)	0.26 0.14 0.06
Data collection
Diffractometer	Stoe IPDS II
Absorption correction	Numerical (X-RED; Stoe Cie, 2002 ▸)
T min, T max	0.697, 0.925
No. of measured, independent and observed [I > 2(I)] reflections	9102, 1630, 1380
R int	0.066
(sin /)max (1)	0.633
Refinement
R[F 2 > 2(F 2)], wR(F 2), S	0.028, 0.067, 1.00
No. of reflections	1630
No. of parameters	126
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
max, min (e 3)	0.38, 0.36

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 ▸).

Supplementary Material

CCDC reference: 1404715

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

[Fe(C4H3ClN2)2(H2O)4](C7H7O3S)2	F(000) = 720
Mr = 699.35	Dx = 1.643 Mg m−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
a = 30.691 (3) Å	Cell parameters from 9102 reflections
b = 6.7321 (3) Å	θ = 1.4–26.7°
c = 6.9435 (6) Å	µ = 0.93 mm−1
β = 99.811 (7)°	T = 133 K
V = 1413.63 (19) Å3	Block, colourless
Z = 2	0.26 × 0.14 × 0.06 mm

Data collection

Stoe IPDS II diffractometer	1380 reflections with I > 2σ(I)
φ scans and ω scans with κ offset	Rint = 0.066
Absorption correction: numerical (X-RED; Stoe & Cie, 2002)	θmax = 26.7°, θmin = 1.4°
Tmin = 0.697, Tmax = 0.925	h = −38→38
9102 measured reflections	k = −8→6
1630 independent reflections	l = −8→8

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.028	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.067	w = 1/[σ2(Fo2) + (0.0395P)2] where P = (Fo2 + 2Fc2)/3
S = 1.00	(Δ/σ)max = 0.001
1630 reflections	Δρmax = 0.38 e Å−3
126 parameters	Δρmin = −0.35 e Å−3
2 restraints

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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Fe1	0.5000	0.0000	0.5000	0.01386 (13)
Cl1	0.68495 (2)	0.0000	0.84806 (9)	0.02791 (16)
O1	0.51119 (5)	0.2190 (3)	0.7183 (2)	0.0399 (4)
N1	0.57111 (7)	0.0000	0.4870 (3)	0.0161 (4)
N2	0.66150 (7)	0.0000	0.4683 (3)	0.0206 (4)
C1	0.60191 (8)	0.0000	0.6491 (3)	0.0171 (5)
H1	0.5932	0.0000	0.7741	0.021*
C2	0.64619 (8)	0.0000	0.6350 (3)	0.0184 (5)
C3	0.58590 (8)	0.0000	0.3161 (3)	0.0192 (5)
H3	0.5652	0.0000	0.1977	0.023*
C4	0.63061 (8)	0.0000	0.3081 (3)	0.0211 (5)
H4	0.6396	0.0000	0.1839	0.025*
S1	0.41620 (2)	0.5000	0.91435 (8)	0.01630 (14)
O2	0.45581 (6)	0.5000	0.8231 (2)	0.0206 (4)
O3	0.41275 (4)	0.32011 (19)	1.02718 (16)	0.0237 (3)
C5	0.37118 (8)	0.5000	0.7189 (3)	0.0165 (5)
C6	0.32788 (8)	0.5000	0.7567 (3)	0.0223 (5)
H6	0.3226	0.5000	0.8876	0.027*
C7	0.29303 (8)	0.5000	0.6040 (4)	0.0239 (5)
H7	0.2637	0.5000	0.6308	0.029*
C8	0.29970 (8)	0.5000	0.4102 (3)	0.0205 (5)
C9	0.34283 (8)	0.5000	0.3749 (3)	0.0211 (5)
H9	0.3480	0.5000	0.2438	0.025*
C10	0.37849 (8)	0.5000	0.5263 (3)	0.0188 (5)
H10	0.4078	0.5000	0.4993	0.023*
C11	0.26090 (9)	0.5000	0.2452 (4)	0.0283 (6)
H11A	0.2351	0.4424	0.2904	0.042*	0.5
H11B	0.2681	0.4209	0.1364	0.042*	0.5
H11C	0.2542	0.6367	0.2013	0.042*	0.5
H1A	0.4925 (10)	0.299 (5)	0.740 (5)	0.080*
H1B	0.5338 (8)	0.251 (5)	0.791 (4)	0.080*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Fe1	0.0130 (2)	0.0152 (2)	0.0129 (2)	0.000	0.00075 (16)	0.000
Cl1	0.0162 (3)	0.0456 (4)	0.0203 (3)	0.000	−0.0017 (2)	0.000
O1	0.0192 (7)	0.0481 (10)	0.0481 (9)	0.0068 (7)	−0.0063 (6)	−0.0343 (7)
N1	0.0165 (10)	0.0157 (10)	0.0159 (9)	0.000	0.0021 (7)	0.000
N2	0.0182 (10)	0.0241 (11)	0.0202 (9)	0.000	0.0051 (8)	0.000
C1	0.0183 (12)	0.0194 (12)	0.0139 (10)	0.000	0.0033 (9)	0.000
C2	0.0178 (12)	0.0194 (12)	0.0168 (10)	0.000	−0.0002 (9)	0.000
C3	0.0212 (13)	0.0210 (12)	0.0155 (10)	0.000	0.0032 (9)	0.000
C4	0.0216 (13)	0.0255 (13)	0.0170 (11)	0.000	0.0054 (9)	0.000
S1	0.0149 (3)	0.0189 (3)	0.0142 (3)	0.000	−0.0001 (2)	0.000
O2	0.0143 (8)	0.0235 (9)	0.0240 (8)	0.000	0.0030 (7)	0.000
O3	0.0224 (7)	0.0263 (7)	0.0203 (6)	−0.0031 (5)	−0.0025 (5)	0.0066 (5)
C5	0.0163 (12)	0.0173 (11)	0.0155 (10)	0.000	0.0014 (9)	0.000
C6	0.0190 (13)	0.0338 (15)	0.0139 (10)	0.000	0.0025 (9)	0.000
C7	0.0138 (12)	0.0354 (15)	0.0229 (12)	0.000	0.0040 (9)	0.000
C8	0.0183 (12)	0.0234 (13)	0.0181 (11)	0.000	−0.0018 (9)	0.000
C9	0.0211 (13)	0.0268 (13)	0.0153 (11)	0.000	0.0028 (9)	0.000
C10	0.0176 (12)	0.0223 (12)	0.0171 (10)	0.000	0.0046 (9)	0.000
C11	0.0217 (13)	0.0391 (16)	0.0216 (12)	0.000	−0.0030 (10)	0.000

Geometric parameters (Å, º)

Fe1—O1i	2.1004 (14)	S1—O2	1.4632 (17)
Fe1—O1ii	2.1004 (14)	S1—O3iv	1.4560 (12)
Fe1—O1iii	2.1004 (14)	S1—O3	1.4560 (12)
Fe1—O1	2.1004 (14)	S1—C5	1.764 (2)
Fe1—N1i	2.200 (2)	C5—C6	1.398 (3)
Fe1—N1	2.200 (2)	C5—C10	1.393 (3)
Cl1—C2	1.733 (2)	C6—H6	0.9500
O1—H1A	0.820 (18)	C6—C7	1.372 (3)
O1—H1B	0.814 (18)	C7—H7	0.9500
N1—C1	1.341 (3)	C7—C8	1.395 (3)
N1—C3	1.341 (3)	C8—C9	1.387 (3)
N2—C2	1.321 (3)	C8—C11	1.506 (3)
N2—C4	1.333 (3)	C9—H9	0.9500
C1—H1	0.9500	C9—C10	1.383 (3)
C1—C2	1.379 (3)	C10—H10	0.9500
C3—H3	0.9500	C11—H11A	0.9800
C3—C4	1.383 (4)	C11—H11B	0.9800
C4—H4	0.9500	C11—H11C	0.9800
O1i—Fe1—O1iii	90.83 (11)	N2—C4—H4	118.8
O1i—Fe1—O1	180.0	C3—C4—H4	118.8
O1iii—Fe1—O1	89.17 (11)	O2—S1—C5	105.44 (10)
O1iii—Fe1—O1ii	180.0	O3iv—S1—O2	112.02 (6)
O1i—Fe1—O1ii	89.17 (11)	O3—S1—O2	112.02 (6)
O1ii—Fe1—O1	90.83 (11)	O3—S1—O3iv	112.56 (10)
O1iii—Fe1—N1	89.32 (5)	O3—S1—C5	107.14 (7)
O1ii—Fe1—N1i	89.32 (5)	O3iv—S1—C5	107.14 (7)
O1i—Fe1—N1i	89.32 (5)	C6—C5—S1	120.03 (17)
O1ii—Fe1—N1	90.68 (5)	C10—C5—S1	120.37 (18)
O1—Fe1—N1	89.32 (5)	C10—C5—C6	119.6 (2)
O1i—Fe1—N1	90.68 (5)	C5—C6—H6	120.1
O1iii—Fe1—N1i	90.68 (5)	C7—C6—C5	119.7 (2)
O1—Fe1—N1i	90.68 (5)	C7—C6—H6	120.1
N1i—Fe1—N1	180.0	C6—C7—H7	119.3
Fe1—O1—H1A	124 (3)	C6—C7—C8	121.5 (2)
Fe1—O1—H1B	131 (2)	C8—C7—H7	119.3
H1A—O1—H1B	105 (3)	C7—C8—C11	120.5 (2)
C1—N1—Fe1	121.88 (15)	C9—C8—C7	118.2 (2)
C1—N1—C3	116.5 (2)	C9—C8—C11	121.4 (2)
C3—N1—Fe1	121.60 (16)	C8—C9—H9	119.3
C2—N2—C4	115.0 (2)	C10—C9—C8	121.4 (2)
N1—C1—H1	119.9	C10—C9—H9	119.3
N1—C1—C2	120.2 (2)	C5—C10—H10	120.2
C2—C1—H1	119.9	C9—C10—C5	119.6 (2)
N2—C2—Cl1	116.93 (19)	C9—C10—H10	120.2
N2—C2—C1	124.4 (2)	C8—C11—H11A	109.5
C1—C2—Cl1	118.71 (18)	C8—C11—H11B	109.5
N1—C3—H3	119.2	C8—C11—H11C	109.5
N1—C3—C4	121.6 (2)	H11A—C11—H11B	109.5
C4—C3—H3	119.2	H11A—C11—H11C	109.5
N2—C4—C3	122.4 (2)	H11B—C11—H11C	109.5
Fe1—N1—C1—C2	180.000 (1)	O2—S1—C5—C10	0.000 (1)
Fe1—N1—C3—C4	180.000 (1)	O3iv—S1—C5—C6	−60.51 (6)
N1—C1—C2—Cl1	180.000 (1)	O3—S1—C5—C6	60.51 (6)
N1—C1—C2—N2	0.000 (1)	O3iv—S1—C5—C10	119.49 (6)
N1—C3—C4—N2	0.000 (1)	O3—S1—C5—C10	−119.49 (6)
C1—N1—C3—C4	0.000 (1)	C5—C6—C7—C8	0.000 (1)
C2—N2—C4—C3	0.000 (1)	C6—C5—C10—C9	0.000 (1)
C3—N1—C1—C2	0.000 (1)	C6—C7—C8—C9	0.000 (1)
C4—N2—C2—Cl1	180.000 (1)	C6—C7—C8—C11	180.000 (1)
C4—N2—C2—C1	0.000 (1)	C7—C8—C9—C10	0.000 (1)
S1—C5—C6—C7	180.000 (1)	C8—C9—C10—C5	0.000 (1)
S1—C5—C10—C9	180.000 (1)	C10—C5—C6—C7	0.000 (1)
O2—S1—C5—C6	180.000 (1)	C11—C8—C9—C10	180.000 (1)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···O2	0.82 (2)	1.91 (2)	2.7238 (19)	171 (4)
O1—H1B···O3v	0.81 (2)	1.95 (2)	2.7624 (19)	177 (3)

Symmetry code: (v) −x+1, y, −z+2.