Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803007773/bt6266sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536803007773/bt6266Isup2.hkl |
CCDC reference: 214607
Key indicators
- Single-crystal X-ray study
- T = 133 K
- Mean (C-C) = 0.004 Å
- R factor = 0.020
- wR factor = 0.052
- Data-to-parameter ratio = 22.6
checkCIF results
No syntax errors found ADDSYM reports no extra symmetry
Alert Level C:
ABSTM_02 Alert C The ratio of expected to reported Tmax/Tmin(RR) is > 1.10 Tmin and Tmax reported: 0.253 0.462 Tmin and Tmax expected: 0.117 0.312 RR = 1.461 Please check that your absorption correction is appropriate. General Notes
ABSTM_02 When printed, the submitted absorption T values will be replaced by the scaled T values. Since the ratio of scaled T's is identical to the ratio of reported T values, the scaling does not imply a change to the absorption corrections used in the study. Ratio of Tmax expected/reported 0.676 Tmax scaled 0.312 Tmin scaled 0.171
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check
During a study of tribromoacetates, small crystals of the title compound were obtained on attempting to crystallize 3,5-dibromopyridinium tribromoacetate from dichloromethane/diethyl ether. Presumably these arose from small quantities of bromine or bromide as a decomposition product.
The acidic H atom was refined freely but with an N—H bond length restraint (DFIX). Other H atoms were included using a riding model with fixed C—H bond lengths of 0.95 Å. Uiso(H) values were fixed at 1.2 times the Ueq of the parent atom.
Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97.
C5H4Br2N+·Br− | F(000) = 584 |
Mr = 317.82 | Dx = 2.553 Mg m−3 |
Monoclinic, C2/m | Mo Kα radiation, λ = 0.71073 Å |
a = 11.6270 (8) Å | Cell parameters from 4877 reflections |
b = 6.8372 (4) Å | θ = 3.5–30.5° |
c = 10.4344 (6) Å | µ = 14.55 mm−1 |
β = 94.574 (4)° | T = 133 K |
V = 826.85 (9) Å3 | Prism, colourless |
Z = 4 | 0.25 × 0.13 × 0.08 mm |
Bruker SMART 1000 CCD diffractometer | 1308 independent reflections |
Radiation source: fine-focus sealed tube | 1138 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.030 |
Detector resolution: 8.192 pixels mm-1 | θmax = 30.0°, θmin = 2.0° |
ω and ϕ scans | h = −16→16 |
Absorption correction: multi-scan (SADABS; Bruker, 1998) | k = −9→9 |
Tmin = 0.253, Tmax = 0.462 | l = −14→14 |
7962 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.020 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.052 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0338P)2] where P = (Fo2 + 2Fc2)/3 |
1308 reflections | (Δ/σ)max = 0.001 |
58 parameters | Δρmax = 0.55 e Å−3 |
1 restraint | Δρmin = −0.78 e Å−3 |
C5H4Br2N+·Br− | V = 826.85 (9) Å3 |
Mr = 317.82 | Z = 4 |
Monoclinic, C2/m | Mo Kα radiation |
a = 11.6270 (8) Å | µ = 14.55 mm−1 |
b = 6.8372 (4) Å | T = 133 K |
c = 10.4344 (6) Å | 0.25 × 0.13 × 0.08 mm |
β = 94.574 (4)° |
Bruker SMART 1000 CCD diffractometer | 1308 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 1998) | 1138 reflections with I > 2σ(I) |
Tmin = 0.253, Tmax = 0.462 | Rint = 0.030 |
7962 measured reflections |
R[F2 > 2σ(F2)] = 0.020 | 1 restraint |
wR(F2) = 0.052 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.06 | Δρmax = 0.55 e Å−3 |
1308 reflections | Δρmin = −0.78 e Å−3 |
58 parameters |
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. Non-bonded Distances 3.9011 (0.0005) Br1 - Br2_$1 3.5117 (0.0005) Br2 - Br3_$2 3.4752 (0.0005) Br1 - Br3_$4 3.8311 (0.0007) Br1 - Br1_$5 3.9545 (0.0004) Br1 - Br1_$6 3.9545 (0.0004) Br1 - Br1_$7 101.84 (0.09) C3 - Br1 - Br2_$1 136.03 (0.09) Br1 - Br2_$1 - C5_$1 168.36 (0.09) C5 - Br2 - Br3_$2 158.35 (0.09) C3 - Br1 - Br3_$4 119.39 (0.09) C3 - Br1 - Br1_$5 73.42 (0.04) C3 - Br1 - Br1_$6 73.42 (0.04) C3 - Br1 - Br1_$7 Operators for generating equivalent atoms: $1 − x, −y, −z $2 − x, −y, −z + 1 $3 − x + 1, −y, −z + 1 $4 x, y, z − 1 $5 − x + 1, −y, −z $6 − x + 1/2, y − 1/2, −z $7 − x + 1/2, y + 1/2, −z |
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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.2711 (2) | 0.0000 | 0.3728 (2) | 0.0210 (5) | |
H01 | 0.318 (3) | 0.0000 | 0.447 (3) | 0.041 (11)* | |
C2 | 0.3274 (2) | 0.0000 | 0.2649 (3) | 0.0213 (6) | |
H2 | 0.4093 | 0.0000 | 0.2687 | 0.026* | |
C3 | 0.2623 (3) | 0.0000 | 0.1490 (3) | 0.0195 (5) | |
C4 | 0.1426 (2) | 0.0000 | 0.1439 (3) | 0.0209 (6) | |
H4 | 0.0978 | 0.0000 | 0.0637 | 0.025* | |
C5 | 0.0901 (2) | 0.0000 | 0.2585 (3) | 0.0196 (5) | |
C6 | 0.1582 (3) | 0.0000 | 0.3746 (3) | 0.0206 (5) | |
H6 | 0.1235 | 0.0000 | 0.4540 | 0.025* | |
Br1 | 0.33492 (3) | 0.0000 | −0.00570 (3) | 0.02854 (9) | |
Br2 | −0.07127 (2) | 0.0000 | 0.26154 (3) | 0.02426 (9) | |
Br3 | 0.36075 (2) | 0.0000 | 0.66478 (3) | 0.02041 (8) |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0210 (12) | 0.0214 (12) | 0.0196 (12) | 0.000 | −0.0055 (10) | 0.000 |
C2 | 0.0163 (13) | 0.0203 (14) | 0.0270 (15) | 0.000 | 0.0001 (11) | 0.000 |
C3 | 0.0168 (12) | 0.0225 (14) | 0.0196 (13) | 0.000 | 0.0041 (10) | 0.000 |
C4 | 0.0179 (13) | 0.0256 (15) | 0.0188 (13) | 0.000 | −0.0005 (10) | 0.000 |
C5 | 0.0165 (12) | 0.0203 (14) | 0.0216 (14) | 0.000 | 0.0001 (10) | 0.000 |
C6 | 0.0194 (13) | 0.0212 (14) | 0.0213 (13) | 0.000 | 0.0018 (10) | 0.000 |
Br1 | 0.02211 (15) | 0.03806 (19) | 0.02650 (17) | 0.000 | 0.00851 (12) | 0.000 |
Br2 | 0.01390 (14) | 0.02879 (17) | 0.03013 (17) | 0.000 | 0.00204 (11) | 0.000 |
Br3 | 0.01699 (14) | 0.02412 (16) | 0.01952 (14) | 0.000 | −0.00222 (10) | 0.000 |
N1—C6 | 1.314 (4) | C3—Br1 | 1.881 (3) |
N1—C2 | 1.347 (4) | C4—C5 | 1.386 (4) |
N1—H01 | 0.912 (19) | C4—H4 | 0.9500 |
C2—C3 | 1.375 (4) | C5—C6 | 1.394 (4) |
C2—H2 | 0.9500 | C5—Br2 | 1.879 (3) |
C3—C4 | 1.388 (4) | C6—H6 | 0.9500 |
C6—N1—C2 | 124.4 (3) | C5—C4—C3 | 118.4 (3) |
C6—N1—H01 | 121 (3) | C5—C4—H4 | 120.8 |
C2—N1—H01 | 114 (3) | C3—C4—H4 | 120.8 |
N1—C2—C3 | 117.7 (3) | C4—C5—C6 | 119.4 (3) |
N1—C2—H2 | 121.2 | C4—C5—Br2 | 121.6 (2) |
C3—C2—H2 | 121.2 | C6—C5—Br2 | 119.0 (2) |
C2—C3—C4 | 121.0 (3) | N1—C6—C5 | 119.1 (3) |
C2—C3—Br1 | 120.1 (2) | N1—C6—H6 | 120.4 |
C4—C3—Br1 | 119.0 (2) | C5—C6—H6 | 120.4 |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H01···Br3 | 0.91 (2) | 2.29 (2) | 3.140 (2) | 156 (4) |
C6—H6···Br2i | 0.95 | 3.08 | 4.006 (3) | 166 |
C2—H2···Br3ii | 0.95 | 2.71 | 3.641 (3) | 168 |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C5H4Br2N+·Br− |
Mr | 317.82 |
Crystal system, space group | Monoclinic, C2/m |
Temperature (K) | 133 |
a, b, c (Å) | 11.6270 (8), 6.8372 (4), 10.4344 (6) |
β (°) | 94.574 (4) |
V (Å3) | 826.85 (9) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 14.55 |
Crystal size (mm) | 0.25 × 0.13 × 0.08 |
Data collection | |
Diffractometer | Bruker SMART 1000 CCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 1998) |
Tmin, Tmax | 0.253, 0.462 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7962, 1308, 1138 |
Rint | 0.030 |
(sin θ/λ)max (Å−1) | 0.704 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.020, 0.052, 1.06 |
No. of reflections | 1308 |
No. of parameters | 58 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.55, −0.78 |
Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1998), SAINT, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1994), SHELXL97.
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H01···Br3 | 0.912 (19) | 2.29 (2) | 3.140 (2) | 156 (4) |
C6—H6···Br2i | 0.95 | 3.08 | 4.006 (3) | 166 |
C2—H2···Br3ii | 0.95 | 2.71 | 3.641 (3) | 168 |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1, −y, −z+1. |
We are interested in secondary bonding contacts (classical and `weak' hydrogen bonds, halogen-halogen contacts) in structures of halopyridinium halides (see Freytag & Jones, 2001, and references therein). In that publication we had already reported the synthesis and structure of the compound 3,5-dibromopyridinium bromide, (I), which crystallized from acetonitrile/methanol/diethyl ether in space group P42/mnm. We have now by chance determined the structure of a second form of the same compound, crystallized from dichloromethane/diethyl ether.
The asymmetric unit, which lies completely in the crystallographic mirror plane y = 0, is presented in Fig. 1. Bond lengths and angles may be regarded as normal, in particular the widened bond angle at the protonated N atom.
The packing within one layer is presented in Fig. 2. A classical N+—H···Br− hydrogen bond is observed, as are two `weak' hydrogen bonds of the form C—H···Br− (Table 2). Only the shorter of these latter two interactions is shown explicitly in Fig. 2; it has a normalized H···Br distance of only 2.58 Å.
There are also several bromine-bromine contacts. The shortest of these, Br1···Br3(x, y, z − 1) = 3.4752 (5) and Br2···Br3(-x, −y, 1 − z) = 3.5117 Å, involve the anion Br3 and are approximately linear at the central bromine [C—Br···Br = 158.35 (9) and 168.36 (9)°]. Such contacts are thought to be associated with a positive region of charge in the extension of the C—Br vector beyond Br. Two further Br···Br contacts are longer than the double van der Waals radius of 3.7 Å (Bondi, 1964), but may nevertheless be regarded as structurally significant; Br1···Br2(-x, −y, −z) = 3.9011 (5) Å and Br1···Br1(1 − x, −y, −z) = 3.8311 (7) Å. The latter, with C—Br···Br angles equal by symmetry at 119.39 (9)°, is a typical `type I' interaction as classified by Pedireddi et al. (1994); in contrast to type II interactions (one 90° and one 180° angle), these are not thought to represent significant electrostatic interactions, but nevertheless are observed so frequently that some stabilizing effect might be presumed. The former has angles of 101.84 (9) and 136.03 (9)° and lies between types I and II.
The packing of the previous modification differed from the pattern described here in one important respect; the higher symmetry of the layers (4/mmm), in which the N—H bonds of neighbouring rings are exactly antiparallel and `share' two bromides via three-centre hydrogen bonds, thus forming units N+—H(···Br-···)2H—N+. In Fig. 2, the formal conversion of the lower to the higher symmetry form can be seen in terms of the R24(10) ring centred at x = 1/2, z = 1; the pyridine rings to the upper right and lower left of the cell edge should both be rotated anticlockwise.
The distance between the layers is b/2 = 3.419 Å, cf. 3.442 Å in the previous modification; however, the latter has a significantly higher density, 2.631 versus 2.553 Mg m−3, suggesting more efficient packing in its layers. One surmises that the energy balance between the two forms would be very delicate.