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lr2097 scheme

Acta Cryst. (2013). E69, m116    [ doi:10.1107/S1600536813001414 ]

trans-Dibromidobis(3-methylpyridine-[kappa]N)copper(II)

F. F. Awwadi

Abstract top

The asymmetric unit of the title compound, [CuBr2(C6H7N)2], contains one half-molecule, the whole molecule being generated by inversion through a center located at the CuII atom. The geometry around the CuII atom is square planar. Semicoordinate Cu...Br bonds [3.269 (1) Å] and nonclassical C-H...Br hydrogen bonds connect the molecules, forming chains running parallel to the a axis. These chains are further linked via additional C-H...Br hydrogen bonds into a three-dimensional network.

Comment top

The molecular units (Fig. 1) of the title compound are linked via Cu···Br semi-coordinate bonds to form a chain structure that runs parallel to the a-axis (Fig. 2). These chains are reinforced by C6—H6···Br1 and C2—H2···Br1 hydrogen bonding interactions. The data summarizing these interactions are shown in Table 1. These chains are interlinked using non-classical C5—H5···Br1 hydrogen bonding interactions to form the final three dimensional structure (Fig. 3).

Cu(4MP)2Cl2, (Marsh et al., 1981), where 4MP is 4-methylpyridine, forms an extended chain structure based on the Cu···Cl semi coordinate bond, similar to the title compound. In contrast, Cu(2MP)2X2, 2MP = 2-methylpyridine and X = Cl or Br, form a dimer structure based on the Cu···X semi coordinate bond (Singh et al., 1972 and Marsh et al., 1982).

The title compound was prepared to investigate chloro-methyl and bromo-methyl exchange rules in the crystal structures of Cu(3YP)2Br2 complexes, where 3YP = 3-substituted pyridine and Y = Cl, Br and methyl (Awwadi et al., 2006 and Awwadi et al., 2011). These three compounds are isostructural in the solid state, hence, the halo-methyl exchange rule is not violated. Desiraju showed that the chloro-methyl exchange rule is obeyed if the final structure is stabilized by dispersive forces (Desiraju & Sarma, 1986). This indicates that the Cu···Br semi-coordinate bonds play the crucial role in determining the final structure of these compounds. The volume of the methyl group is ca 24 Å3 which is in between the volume of chlorine (ca 19 Å3) and bromine (ca 27 Å3). In contrast, if directional forces are involved, the chloro-methyl exchange rule is violated.

Related literature top

The title compound was prepared to investigate chloro-methyl and bromo-methyl exchange rules in the crystal structures of [Cu(3YP)2Br2] complexes (where 3YP = 3-substituted pyridine and Y = Cl, Br and methyl), see: Awwadi et al. (2006, 2011). Desiraju showed that the chloro-methyl exchange rule is obeyed if the final structure is stabilized by dispersive forces, see: Desiraju & Sarma (1986). For related structures, see: Marsh et al. (1981, 1982); Singh et al. (1972).

Experimental top

2 mmol of 3-methylpyridine were dissolved in 20 mL of acetonitrile. One mmol of CuBr2 was dissolved in 20 mL of acetonitrile. The two solutions were mixed. The resulting solution was gently heated with stirring for 15 minutes. The solution was filtered and left to slowly evaporate at the room temperature. Green crystals with a needle habit were formed. One of these crystals was used for single-crystal X-ray data collection.

Refinement top

The structure was solved by direct methods and refined by least squares method on F2 using the SHELXTL program package. The structure was solved in the space group P2(1)/c (# 14) by analysis of systematic absences. All atoms were refined anisotropically. Hydrogen atoms were placed at the calculated positions using a riding model with C(aromatic)—H = 0.95 Å and Uiso(H) = 1.2Ueq(C), and with C(aliphatic)—H = 0.98 Å and Uiso(H) = 1.5Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); 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 top
[Figure 1] Fig. 1. The molecular unit of the title compound. Symmetry transformations used to generate equivalent atoms are -x + 1, -y, -z + 2. Thermal ellipsoids are shown at 50% probability.
[Figure 2] Fig. 2. Chain structure of the title compound.
[Figure 3] Fig. 3. The packing diagram of the title compound viewed down the a-axis.
trans-Dibromidobis(3-methylpyridine-κN)copper(II) top
Crystal data top
[CuBr2(C6H7N)2]F(000) = 398
Mr = 409.61Dx = 2.020 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 2369 reflections
a = 4.0171 (8) Åθ = 2.2–29.8°
b = 14.105 (3) ŵ = 7.53 mm1
c = 11.899 (2) ÅT = 85 K
β = 92.54 (3)°Needle, green
V = 673.5 (2) Å30.24 × 0.03 × 0.03 mm
Z = 2
Data collection top
Bruker/Siemens SMART APEX
diffractometer
1536 independent reflections
Radiation source: normal-focus sealed tube1283 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.044
Detector resolution: 8.3 pixels mm-1θmax = 27.5°, θmin = 2.9°
ω scansh = 54
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
k = 1618
Tmin = 0.265, Tmax = 0.806l = 1415
5995 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.032Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.075H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0388P)2]
where P = (Fo2 + 2Fc2)/3
1536 reflections(Δ/σ)max < 0.001
80 parametersΔρmax = 0.97 e Å3
0 restraintsΔρmin = 0.47 e Å3
Crystal data top
[CuBr2(C6H7N)2]V = 673.5 (2) Å3
Mr = 409.61Z = 2
Monoclinic, P21/cMo Kα radiation
a = 4.0171 (8) ŵ = 7.53 mm1
b = 14.105 (3) ÅT = 85 K
c = 11.899 (2) Å0.24 × 0.03 × 0.03 mm
β = 92.54 (3)°
Data collection top
Bruker/Siemens SMART APEX
diffractometer
1536 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
1283 reflections with I > 2σ(I)
Tmin = 0.265, Tmax = 0.806Rint = 0.044
5995 measured reflectionsθmax = 27.5°
Refinement top
R[F2 > 2σ(F2)] = 0.032H-atom parameters constrained
wR(F2) = 0.075Δρmax = 0.97 e Å3
S = 1.01Δρmin = 0.47 e Å3
1536 reflectionsAbsolute structure: ?
80 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
Br10.12621 (8)0.03733 (3)0.83940 (3)0.01337 (12)
Cu10.50000.00001.00000.01824 (18)
N10.5100 (7)0.1368 (2)1.0454 (2)0.0154 (7)
C20.6317 (9)0.2051 (3)0.9789 (3)0.0158 (8)
H20.71160.18690.90810.019*
C30.6464 (9)0.2998 (3)1.0082 (3)0.0153 (8)
C40.5247 (9)0.3257 (3)1.1112 (3)0.0165 (8)
H40.53170.38991.13500.020*
C50.3921 (9)0.2560 (3)1.1791 (3)0.0163 (8)
H50.30240.27251.24900.020*
C60.3925 (8)0.1636 (3)1.1440 (3)0.0160 (8)
H60.30570.11651.19160.019*
C70.7889 (9)0.3717 (3)0.9301 (3)0.0211 (9)
H7A0.89710.33890.86900.032*
H7B0.95310.41100.97190.032*
H7C0.60940.41200.89860.032*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0162 (2)0.0089 (2)0.01488 (19)0.00020 (14)0.00062 (13)0.00010 (13)
Cu10.0286 (4)0.0059 (3)0.0194 (3)0.0034 (3)0.0089 (3)0.0029 (2)
N10.0213 (16)0.0084 (17)0.0160 (15)0.0025 (12)0.0051 (12)0.0015 (11)
C20.0178 (19)0.015 (2)0.0144 (17)0.0028 (15)0.0028 (14)0.0033 (14)
C30.0138 (19)0.012 (2)0.0199 (19)0.0013 (14)0.0027 (14)0.0015 (14)
C40.019 (2)0.0076 (19)0.0221 (19)0.0002 (15)0.0038 (15)0.0030 (14)
C50.0191 (18)0.017 (2)0.0132 (18)0.0000 (15)0.0024 (14)0.0019 (14)
C60.0156 (19)0.013 (2)0.0193 (19)0.0044 (14)0.0007 (15)0.0010 (14)
C70.024 (2)0.016 (2)0.023 (2)0.0033 (16)0.0020 (16)0.0028 (15)
Geometric parameters (Å, º) top
Br1—Cu12.4351 (8)C3—C71.506 (5)
Cu1—N1i2.004 (3)C4—C51.393 (5)
Cu1—N12.004 (3)C4—H40.9500
Cu1—Br1i2.4351 (8)C5—C61.369 (5)
N1—C61.338 (4)C5—H50.9500
N1—C21.351 (5)C6—H60.9500
C2—C31.382 (5)C7—H7A0.9800
C2—H20.9500C7—H7B0.9800
C3—C41.388 (5)C7—H7C0.9800
N1i—Cu1—N1180.000 (1)C3—C4—C5119.0 (4)
N1i—Cu1—Br189.57 (8)C3—C4—H4120.5
N1—Cu1—Br190.43 (8)C5—C4—H4120.5
N1i—Cu1—Br1i90.43 (8)C6—C5—C4119.3 (3)
N1—Cu1—Br1i89.57 (8)C6—C5—H5120.4
Br1—Cu1—Br1i180.0C4—C5—H5120.4
C6—N1—C2117.6 (3)N1—C6—C5122.8 (3)
C6—N1—Cu1120.3 (3)N1—C6—H6118.6
C2—N1—Cu1122.1 (2)C5—C6—H6118.6
N1—C2—C3123.6 (3)C3—C7—H7A109.5
N1—C2—H2118.2C3—C7—H7B109.5
C3—C2—H2118.2H7A—C7—H7B109.5
C2—C3—C4117.7 (3)C3—C7—H7C109.5
C2—C3—C7120.6 (3)H7A—C7—H7C109.5
C4—C3—C7121.8 (3)H7B—C7—H7C109.5
Br1—Cu1—N1—C6117.1 (2)N1—C2—C3—C7179.4 (3)
Br1i—Cu1—N1—C662.9 (2)C2—C3—C4—C50.6 (5)
Br1—Cu1—N1—C262.5 (3)C7—C3—C4—C5179.2 (3)
Br1i—Cu1—N1—C2117.5 (3)C3—C4—C5—C61.6 (5)
C6—N1—C2—C31.2 (5)C2—N1—C6—C50.1 (5)
Cu1—N1—C2—C3179.1 (3)Cu1—N1—C6—C5179.8 (3)
N1—C2—C3—C40.9 (5)C4—C5—C6—N11.3 (5)
Symmetry code: (i) x+1, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···Br1ii0.952.833.549 (4)133
C6—H6···Br1iii0.952.793.529 (4)135
C5—H5···Br1iv0.952.993.668 (4)130
Symmetry codes: (ii) x+1, y, z; (iii) x, y, z+2; (iv) x, y+1/2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···Br1i0.952.8313.549 (4)133.10
C6—H6···Br1ii0.952.7923.529 (4)135.02
C5—H5···Br1iii0.952.9873.668 (4)129.76
Symmetry codes: (i) x+1, y, z; (ii) x, y, z+2; (iii) x, y+1/2, z+1/2.
Acknowledgements top

The author thanks Brendan Twamley for collecting the X-ray diffraction data set.

references
References top

Awwadi, F. F., Willett, R. D., Haddad, S. F. & Twamley, B. (2006). Cryst. Growth Des. 6, 1833–1838.

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Marsh, W. E., Hatfield, W. E. & Hodgson, D. J. (1982). Inorg. Chem. 21, 2679–2684.

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