supplementary materials


Acta Cryst. (2007). E63, m1701    [ doi:10.1107/S1600536807023070 ]

Dimethylpyrazinium tetrabromidoferrate(II): Br...aryl...Br and Br...Br intermolecular interactions

R. Al-Far and B. F. Ali

Abstract top

In the title compound, (C6H10N2)[FeBr4], the asymmetric unit contains one half-cation and one half-anion, where the Fe atom has a distorted tetrahedral environment. The Fe atom and two Br atoms lie on a mirror plane; the cation is centrosymmetric. In the crystal structure, the cations and anions are packed into alternate stacking with no significant intermolecular Br...Br and/or aryl...aryl interactions within each stack. The anion...anion stacks interact via Br...Br interactions [Br...Br = 3.8773 (15) Å] to form one-dimensional arrays. The Br...aryl interactions are arranged in a ...Br...aryl...Br...aryl... infinite motif [Br...centroid distance of 3.928 (1) Å]. All of them link the anions and cations into two-dimensional layers.

Comment top

The research in the field of inorganic-organic hybrids is of great interest due to their magnetic, electronic and optoelectric properties (Cui et al., 2000; Lacroix et al., 1994; Chakravarthy & Guloy, 1997). The packing interactions that govern the crystal organization is expected to affect the packing and then the specific properties of such solids. For example, pyrazine (pyz) and similar ligands have been used through their two nitrogen atoms as neutral linkers to generate and stabilize many open 1-, 2- and 3-D coordination polymers and forming supramolecular coordination assemblies (Hao & Liu, 2007; Huang & Wang, 2007). We herein report the crystal structure of the title complex, (I), wherein, the protonated dimethylpyrazinium ligand [pyzH2]2+ is not involved in coordination, but in extensive infinite aryl···Br···aryl···Br intermolecular interactions, affording a 2-D network structure by the aid of Br···Br interactions.

The asymmetric unit of the title compound, (I), contains one half [pyzH2]2+ cation and [FeBr3]1- unit of the anion, where the Fe atom has a distorted tetrahedral environment (Fig. 1, Table 1). The Fe—Br bonds and Br—Fe—Br angles are in the range of 2.3182 (17)–2.3348 (11) Å [mean value is 2.3305 (14) Å] and 108.72 (4)–110.63 (7) °, respectively, in which they are in accordance with the corresponding values (Benito-Garagorri et al., 2006; Kruszynski & Wyrzykowski, 2006). The bond lengths and angles in the brominated cation are also in accordance with the corresponding ones (Hao & Liu, 2007; Churakov et al., 2006; Yang et al., 2004).

The molecules of discrete anions, packed into stacks, are separated by stacks of cations. The anion stacks along the c axis are parallel to the cation stacks with Fe···Fe distance of 6.8583 (14) Å, with no significant interactions between anions and cations within a stack. Inter anion-stacks are linked only through one Br···Br interaction parallel to b axis [Br3···Br3A = 3.8773 (15) Å (symmetry code A: 2 - x, 1 - y, 1 - z)]. The anions and cations are not involved in any of Br···H interactions, but only through Br···aryl interactions, that are represented in the ···Br···aryl···Br···aryl··· infinite motif (Al-Far & Ali, 2007), in which the bromide ions of the anion lie between the two cationic species with centroid···Br···centroid (symmetry code: 2 - x, 1/2 + y, 1 - z) repeat distance of 3.928 (1) Å. Beside these interactions along with inter anion-stacks, the Br···Br interactions also link the anions and cations together into 2-D layers approximately normal to the a axis (Fig 2).

Related literature top

For general background, see: Cui et al. (2000); Lacroix et al. (1994); Chakravarthy & Guloy (1997); Huang & Wang (2007); Al-Far & Ali (2007). For related literature, see: Garagorri-Benito et al. (2006); Kruszynski & Wyrzykowski (2006); Hao & Liu (2007); Churakov et al. (2006); Yang et al. (2004).

Experimental top

For the preparation of (I), FeCl2 (127 mg, 1 mmol) dissolved in absolute ethanol (10 ml) and liquid Br2 (20%, 1 ml), was added dropwise to a stirred hot ethanolic solution of dimethylpyrazine (77%, 1 ml) dissolved in ethanol (10 ml) and HBr (60%, 2 ml). After heating for 3 h, the mixture was filtered off and allowed to stand undisturbed at room temperature. The salt crystallized out over 3 d as black blocks. Crystals were filtered off, washed with ethanol then diethylether, and dried under vacuum (yield; 300 mg, 61.8%).

Refinement top

H atoms were positioned geometrically, with N—H = 0.86 Å (for NH) and C—H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, and constrained to ride on their parent atoms, with Uiso(H) = xUeq(C,N), where x = 1.5 for methyl H, and x = 1.2 for all other H atoms.

Computing details top

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1999); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level (symmetry code A: x, 3/2 - y, z).
[Figure 2] Fig. 2. A packing diagram for (I). The Br···Br and Br···aryl interactions are shown as dashed lines.
Dimethylpyrazinium tetrabromidoferrate(II) top
Crystal data top
(C6H10N2)[FeBr4]F(000) = 452
Mr = 485.61Dx = 2.461 Mg m3
Monoclinic, P21/mMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybCell parameters from 1974 reflections
a = 6.6591 (13) Åθ = 3.0–27.9°
b = 14.352 (3) ŵ = 13.31 mm1
c = 6.8583 (14) ÅT = 294 K
β = 90.92 (3)°Block, black
V = 655.4 (2) Å30.20 × 0.15 × 0.10 mm
Z = 2
Data collection top
Rigaku Mercury CCD
diffractometer
1213 independent reflections
Radiation source: fine-focus sealed tube856 reflections with I > 2σ(I)
graphiteRint = 0.084
Detector resolution: 14.6306 pixels mm-1θmax = 25.2°, θmin = 3.0°
dtintegrate.ref scansh = 67
Absorption correction: numerical
(Shape Tracing Software; REFERENCE?)
k = 1517
Tmin = 0.103, Tmax = 0.262l = 88
5269 measured reflections
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)] = 0.044H-atom parameters constrained
wR(F2) = 0.113 w = 1/[σ2(Fo2) + (0.0601P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.97(Δ/σ)max = 0.043
1213 reflectionsΔρmax = 0.66 e Å3
66 parametersΔρmin = 0.91 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.032 (3)
Crystal data top
(C6H10N2)[FeBr4]V = 655.4 (2) Å3
Mr = 485.61Z = 2
Monoclinic, P21/mMo Kα radiation
a = 6.6591 (13) ŵ = 13.31 mm1
b = 14.352 (3) ÅT = 294 K
c = 6.8583 (14) Å0.20 × 0.15 × 0.10 mm
β = 90.92 (3)°
Data collection top
Rigaku Mercury CCD
diffractometer
1213 independent reflections
Absorption correction: numerical
(Shape Tracing Software; REFERENCE?)
856 reflections with I > 2σ(I)
Tmin = 0.103, Tmax = 0.262Rint = 0.084
5269 measured reflectionsθmax = 25.2°
Refinement top
R[F2 > 2σ(F2)] = 0.044H-atom parameters constrained
wR(F2) = 0.113Δρmax = 0.66 e Å3
S = 0.97Δρmin = 0.91 e Å3
1213 reflectionsAbsolute structure: ?
66 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
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.

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 (Å2) top
xyzUiso*/Ueq
Fe10.81018 (19)0.75000.77976 (18)0.0431 (4)
Br20.92375 (18)0.75001.10355 (15)0.0725 (4)
Br10.46205 (15)0.75000.76938 (16)0.0627 (4)
Br30.92512 (11)0.61623 (5)0.62320 (11)0.0649 (4)
C30.3172 (15)0.5452 (7)1.0157 (16)0.084 (3)
H3A0.19370.57521.02250.100*
N40.3605 (14)0.4879 (7)0.8654 (18)0.123 (4)
H4A0.26980.47900.77660.148*
C20.4576 (15)0.5570 (7)1.1530 (15)0.085 (3)
C10.4033 (16)0.6165 (7)1.3151 (13)0.095 (3)
H1A0.29120.58981.38140.143*
H1B0.36730.67721.26690.143*
H1C0.51540.62191.40420.143*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Fe10.0450 (8)0.0465 (8)0.0377 (7)0.0000.0013 (6)0.000
Br20.0831 (9)0.0942 (10)0.0398 (6)0.0000.0103 (6)0.000
Br10.0458 (6)0.0744 (8)0.0681 (8)0.0000.0037 (5)0.000
Br30.0702 (6)0.0626 (6)0.0617 (6)0.0158 (4)0.0042 (4)0.0125 (4)
C30.077 (7)0.080 (6)0.092 (7)0.006 (5)0.027 (6)0.015 (6)
N40.082 (6)0.125 (8)0.160 (10)0.036 (6)0.062 (6)0.057 (7)
C20.083 (7)0.081 (7)0.090 (7)0.028 (5)0.026 (6)0.037 (5)
C10.110 (8)0.096 (8)0.080 (7)0.024 (6)0.010 (6)0.011 (6)
Geometric parameters (Å, °) top
Fe1—Br12.3182 (17)N4—C2ii1.380 (13)
Fe1—Br22.3343 (17)N4—H4A0.8600
Fe1—Br3i2.3348 (11)C2—N4ii1.380 (13)
Fe1—Br32.3348 (11)C2—C11.452 (13)
C3—C21.328 (12)C1—H1A0.9600
C3—N41.353 (13)C1—H1B0.9600
C3—H3A0.9300C1—H1C0.9600
Br1—Fe1—Br2109.74 (7)C2ii—N4—H4A118.3
Br1—Fe1—Br3i108.72 (4)C3—C2—N4ii119.0 (10)
Br2—Fe1—Br3i109.51 (4)C3—C2—C1115.9 (11)
Br1—Fe1—Br3108.72 (4)N4ii—C2—C1125.1 (10)
Br2—Fe1—Br3109.51 (4)C2—C1—H1A109.5
Br3i—Fe1—Br3110.63 (7)C2—C1—H1B109.5
C2—C3—N4117.5 (10)H1A—C1—H1B109.5
C2—C3—H3A121.2C2—C1—H1C109.5
N4—C3—H3A121.2H1A—C1—H1C109.5
C3—N4—C2ii123.5 (9)H1B—C1—H1C109.5
C3—N4—H4A118.3
C2—C3—N4—C2ii1.0 (16)N4—C3—C2—C1178.0 (9)
N4—C3—C2—N4ii1.0 (16)
Symmetry codes: (i) x, −y+3/2, z; (ii) −x+1, −y+1, −z+2.
Table 1
Selected geometric parameters (Å, °)
top
Fe1—Br12.3182 (17)Fe1—Br3i2.3348 (11)
Fe1—Br22.3343 (17)Fe1—Br32.3348 (11)
Br1—Fe1—Br2109.74 (7)Br1—Fe1—Br3108.72 (4)
Br1—Fe1—Br3i108.72 (4)Br2—Fe1—Br3109.51 (4)
Br2—Fe1—Br3i109.51 (4)Br3i—Fe1—Br3110.63 (7)
Symmetry codes: (i) x, −y+3/2, z.
Acknowledgements top

This research was supported by Al al-Bayt University and Al-Balqa'a Applied University.

references
References top

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