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The title compound, (C5H6Br2N3)2[CuBr4], contains isolated substituted pyridinium cations and [CuBr4]2- anions. The di­amino­di­bromo­pyridinium ions are planar, while the CuII ions have a distorted compressed tetrahedral coordination with C2 symmetry. The two independent trans-Br-Cu-Br angles are 128.9 (1) and 136.0 (1)°, with Cu-Br distances of 2.3939 (15) and 2.3790 (16) Å.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100012105/qa0382sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100012105/qa0382Isup2.hkl
Contains datablock I

CCDC reference: 152653

Comment top

The catalytic halogenation of activated pyridine rings by copper(II) halides is a common phenomenon. The bromination step presubably involves reduction of CuII to CuI, with the subsequent re-oxidation to CuII by atmospheric oxygen. In our attempts to prepare various substituted pyridinium salts of copper(II) halides, we have frequently isolated the corresponding halogenated salts (Willett & West, 1987; Willett, 1988, 2000; Place & Willett, 1987; Willett & Halvorson, 1988). With 2,6-diaminopyridine, we have previously reported the formation and isolation of the corresponding 3,5-dichloro derivative (Willett & West, 1987) as the [CuCl4]2− salt. However, the compound crystallizes in a different space group.

In the title compound, (I), the cation is nearly planar. However, the Br5 atom lies 0.116 Å out of the plane of the pyridine ring. This is probably due to steric repulsion with the adjacent NH2 group. The [CuBr4]2− anion has a slightly compressed tetrahedral geometry with a substantial (but not unusual) distortion from idealized D2 d symmetry (Place & Willett, 1988).

Experimental top

2,6-Diaminopyridine (0.01 mol, 1.09 g) and CuBr2 (0.005 mol, 1.12 g) were dissolved in dilute HBr (100 ml, ca 0.1M) and the resultant solution was slowly evaporated at ca 323 K. The compound was obtained as small nearly opaque purple crystals after two days.

Refinement top

H atoms were found on difference Fourier syntheses and positional parameters and isotropic displacement parameters refined. The X—H distances were restrained to a distance of 0.96 (5) Å. The largest residual electron-density peaks all lie within 1.06 Å of Br atoms.

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

(I) top
Crystal data top
(C5H6N3Br2)2[CuBr4]F(000) = 1692
Mr = 919.08Dx = 2.741 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
a = 20.612 (10) ÅCell parameters from 5523 reflections
b = 10.053 (5) Åθ = 2.4–24.7°
c = 13.507 (7) ŵ = 15.34 mm1
β = 127.264 (7)°T = 293 K
V = 2227.3 (19) Å3Plates, purple
Z = 40.38 × 0.18 × 0.03 mm
Data collection top
Bruker CCD area-detector
diffractometer
1849 independent reflections
Radiation source: normal-focus sealed tube1274 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.056
ϕ and ω scansθmax = 24.7°, θmin = 2.4°
Absorption correction: empirical (using intensity measurements)
(SADABS; Bruker, 1998)
h = 1624
Tmin = 0.045, Tmax = 0.681k = 1111
5523 measured reflectionsl = 1514
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)] = 0.050Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.129All H-atom parameters refined
S = 1.02 w = 1/[σ2(Fo2) + (0.0744P)2]
where P = (Fo2 + 2Fc2)/3
1849 reflections(Δ/σ)max < 0.001
138 parametersΔρmax = 1.31 e Å3
6 restraintsΔρmin = 0.96 e Å3
Crystal data top
(C5H6N3Br2)2[CuBr4]V = 2227.3 (19) Å3
Mr = 919.08Z = 4
Monoclinic, C2/cMo Kα radiation
a = 20.612 (10) ŵ = 15.34 mm1
b = 10.053 (5) ÅT = 293 K
c = 13.507 (7) Å0.38 × 0.18 × 0.03 mm
β = 127.264 (7)°
Data collection top
Bruker CCD area-detector
diffractometer
1849 independent reflections
Absorption correction: empirical (using intensity measurements)
(SADABS; Bruker, 1998)
1274 reflections with I > 2σ(I)
Tmin = 0.045, Tmax = 0.681Rint = 0.056
5523 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0506 restraints
wR(F2) = 0.129All H-atom parameters refined
S = 1.02Δρmax = 1.31 e Å3
1849 reflectionsΔρmin = 0.96 e Å3
138 parameters
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
Cu0.50000.32918 (15)0.25000.0435 (4)
Br10.39440 (7)0.43115 (10)0.24630 (10)0.0546 (3)
Br20.57585 (7)0.23991 (9)0.45615 (9)0.0523 (3)
N10.1810 (5)0.0220 (8)0.0548 (7)0.0433 (19)
H10.141 (4)0.038 (7)0.021 (8)0.04 (3)*
C20.2598 (6)0.0111 (9)0.1253 (8)0.040 (2)
N20.2777 (6)0.1393 (8)0.1300 (9)0.054 (2)
H2A0.329 (3)0.161 (8)0.165 (7)0.02 (2)*
H2B0.232 (6)0.191 (13)0.101 (13)0.13 (6)*
C30.3147 (6)0.0932 (9)0.1849 (8)0.041 (2)
Br30.42727 (7)0.05131 (11)0.28619 (10)0.0610 (4)
C40.2868 (7)0.2212 (9)0.1690 (10)0.047 (3)
H40.318 (6)0.299 (8)0.209 (9)0.09 (4)*
C50.2059 (7)0.2499 (8)0.0931 (8)0.040 (2)
Br50.16690 (8)0.42578 (9)0.06204 (10)0.0579 (4)
C60.1478 (7)0.1468 (9)0.0331 (9)0.044 (2)
N60.0681 (6)0.1620 (9)0.0454 (9)0.061 (3)
H6A0.044 (7)0.234 (8)0.031 (11)0.08 (4)*
H6B0.031 (7)0.089 (9)0.079 (11)0.10 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu0.0432 (11)0.0436 (9)0.0421 (9)0.0000.0250 (9)0.000
Br10.0594 (8)0.0534 (6)0.0599 (7)0.0096 (5)0.0407 (6)0.0035 (5)
Br20.0581 (7)0.0395 (5)0.0477 (6)0.0029 (5)0.0259 (6)0.0071 (4)
N10.045 (6)0.036 (4)0.043 (5)0.000 (4)0.024 (5)0.003 (4)
C20.052 (7)0.036 (5)0.033 (5)0.004 (5)0.028 (5)0.001 (4)
N20.047 (7)0.045 (5)0.068 (6)0.005 (5)0.034 (6)0.005 (4)
C30.035 (6)0.053 (6)0.033 (5)0.004 (4)0.019 (5)0.001 (4)
Br30.0457 (7)0.0738 (8)0.0606 (7)0.0017 (5)0.0307 (6)0.0097 (5)
C40.070 (8)0.036 (5)0.048 (6)0.006 (5)0.043 (6)0.007 (4)
C50.062 (7)0.029 (5)0.038 (5)0.006 (4)0.034 (5)0.002 (4)
Br50.0830 (9)0.0376 (5)0.0605 (7)0.0093 (5)0.0473 (7)0.0014 (4)
C60.055 (7)0.043 (5)0.035 (5)0.008 (5)0.027 (5)0.007 (4)
N60.064 (8)0.045 (5)0.061 (6)0.011 (5)0.031 (6)0.001 (4)
Geometric parameters (Å, º) top
Cu—Br12.3790 (16)N2—H2B0.93 (5)
Cu—Br1i2.3790 (16)C3—C41.373 (13)
Cu—Br22.3939 (15)C3—Br31.894 (9)
Cu—Br2i2.3939 (15)C4—C51.358 (15)
N1—C21.335 (12)C4—H40.95 (5)
N1—C61.374 (12)C5—C61.410 (14)
N1—H10.90 (5)C5—Br51.881 (9)
C2—N21.331 (12)C6—N61.317 (13)
C2—C31.388 (13)N6—H6A0.96 (5)
N2—H2A0.88 (4)N6—H6B0.95 (5)
Br1—Cu—Br1i128.95 (9)C4—C3—C2120.0 (9)
Br1—Cu—Br297.52 (5)C4—C3—Br3122.4 (8)
Br1i—Cu—Br2101.08 (5)C2—C3—Br3117.6 (7)
Br1—Cu—Br2i101.08 (4)C5—C4—C3121.6 (9)
Br1i—Cu—Br2i97.52 (4)C5—C4—H4111 (7)
Br2—Cu—Br2i135.97 (9)C3—C4—H4128 (7)
C2—N1—C6127.9 (9)C4—C5—C6120.3 (8)
C2—N1—H1123 (6)C4—C5—Br5122.1 (7)
C6—N1—H1108 (6)C6—C5—Br5117.6 (8)
N2—C2—N1117.2 (9)N6—C6—N1119.7 (9)
N2—C2—C3126.7 (10)N6—C6—C5126.0 (9)
N1—C2—C3116.0 (8)N1—C6—C5114.1 (9)
C2—N2—H2A118 (5)C6—N6—H6A118 (7)
C2—N2—H2B110 (10)C6—N6—H6B123 (8)
H2A—N2—H2B131 (10)H6A—N6—H6B108 (10)
C6—N1—C2—N2178.4 (9)C3—C4—C5—C63.3 (14)
C6—N1—C2—C30.7 (14)C3—C4—C5—Br5175.8 (7)
N2—C2—C3—C4178.7 (9)C2—N1—C6—N6176.1 (10)
N1—C2—C3—C40.3 (13)C2—N1—C6—C50.8 (13)
N2—C2—C3—Br31.1 (13)C4—C5—C6—N6177.6 (10)
N1—C2—C3—Br3180.0 (6)Br5—C5—C6—N61.5 (13)
C2—C3—C4—C51.7 (14)C4—C5—C6—N12.7 (12)
Br3—C3—C4—C5178.1 (7)Br5—C5—C6—N1176.4 (6)
Symmetry code: (i) x+1, y, z+1/2.

Experimental details

Crystal data
Chemical formula(C5H6N3Br2)2[CuBr4]
Mr919.08
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)20.612 (10), 10.053 (5), 13.507 (7)
β (°) 127.264 (7)
V3)2227.3 (19)
Z4
Radiation typeMo Kα
µ (mm1)15.34
Crystal size (mm)0.38 × 0.18 × 0.03
Data collection
DiffractometerBruker CCD area-detector
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(SADABS; Bruker, 1998)
Tmin, Tmax0.045, 0.681
No. of measured, independent and
observed [I > 2σ(I)] reflections
5523, 1849, 1274
Rint0.056
(sin θ/λ)max1)0.588
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.129, 1.02
No. of reflections1849
No. of parameters138
No. of restraints6
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)1.31, 0.96

Computer programs: SMART (Bruker, 1997), SMART, SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXL97.

 

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