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The crystal and molecular structure of 4-di­methyl­amino­pyridinium bromide, C7H11N2+.Br-, (I), is built up by hydrogen-bonded dimers of crystallographic 222 symmetry and four short C-H...halogen contacts. It is remarkable that (I) and 4-di­methyl­amino­pyridinium chloride are not isostructural.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199016133/qb0146sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270199016133/qb0146Isup2.hkl
Contains datablock I

CCDC reference: 140861

Comment top

It is a long tradition in our group to investigate the formation of Lewis-acid-base complexes of the silicon halides (Adley et al., 1972; Campbell-Ferguson & Ebsworth, 1966; Fleischer et al., 1996; Klebe et al., 1985; Spangenberg, 1999).

In the course of our research work several reactions of different silanes with tertiary organic nitrogen bases were performed. The afforded reaction products are very susceptible to moisture and, as a result of that, it sometimes happens that only crystals of the hydrolysed compounds are obtained (Hensen et al., 1998; Bolte & Kettner, 1998).

The molecule of (I) with C2v symmetry has crystallographic C2 symmetry. The atoms Br1, H1, N1, C4 and N4 are located on a twofold rotation axis. The NH group forms a bifurcated hydrogen bond to two symmetry equivalent Br ions (H1···Br1 2.80 Å, N1—H1···Br1 132.7°) resulting in a dimer of crystallographic 222 symmetry. Furthermore, the crystal packing is stabilized by short Br···H contacts: H2···Br1 2.90 Å, C2—H2···Br1 124.7°, and H3···Br1i 2.99 Å, C3—H3···Br1i 134.2° [symmetry code: (i) 3/2 − x,1/2 − y,-z]. \scheme

(I) crystallizes in planes parallel to (100). However, the molecules in a plane are not exactly coplanar, but twisted by 4.88 (3)° relative to each other.

The molecular geometry of the title compound is as expected. Bond lengths and angles adopt the usual values.

It is remarkable that the exchange of Br and Cl in 4-dimethylaminopyridinium complexes leads to different crystal structures: (I) and 4-dimethylaminopyridinium chloride (Bryant & King, 1992) are not isostructural. This lack of isostructurality has already been observed for other small pyridinium complexes (Faber et al., 1999)

As previously published structures of 4-dimethylaminopyridinium suggest (Biradha et al., 1995; Chao et al., 1977), 4-dimethylaminopyridinium changes its packing arrangement rather easily as other small molecules are incorporated into the crystal.

Experimental top

The title compound was obtained accidentally as part of solubility studies on silicon complexes resulting from the reaction of SiBr2Cl2 with 4-dimethylaminopyridine (DMAP). In chloroforme, DMAP reacts with SiBr2Cl2 to yield a white powder that is readily dissolved in methyl or ethyl alcohol. In hot propanol or hot butanol the substance dissolves equally well and yields needles of the title compound upon cooling.

Refinement top

The data were collected at room temperature, because we observed that the crystals underwent an irreversible phase transition upon cooling. The data collection nominally covered a sphere of reciprocal space, by a combination of seven sets of exposures; each set had a different ϕ angle for the crystal and each exposure covered 0.3° in ω. The crystal-to-detector distance was 4.0 cm. Crystal decay was monitored by repeating the initial frames at the end of data collection and analyzing the duplicate reflections.

All H atoms were located by difference Fourier synthesis and refined with fixed individual displacement parameters [U(H) = 1.5 Ueq(Cmethyl), U(H) = 1.2 Ueq(C) or U(H) = 1.2 Ueq(N)] using a riding model with CH(methyl) = 0.96, C—H(aromatic) = 0.93, or N—H = 0.86 Å, respectively.

The methyl groups attached to the aromatic ring were allowed to rotate about their local threefold axis.

Computing details top

Data collection: SMART (Siemens, 1995); cell refinement: SMART (Siemens, 1995); data reduction: SAINT (Siemens, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

(I) top
Crystal data top
C7H11N2+·BrF(000) = 1632
Mr = 203.09Dx = 1.536 Mg m3
Orthorhombic, FdddMo Kα radiation, λ = 0.71073 Å
Hall symbol: -F 2uv 2vwCell parameters from 502 reflections
a = 6.9804 (8) Åθ = 1–20°
b = 19.256 (2) ŵ = 4.61 mm1
c = 26.131 (3) ÅT = 293 K
V = 3512.4 (7) Å3Plate, colourless
Z = 160.30 × 0.20 × 0.10 mm
Data collection top
Siemens CCD three-circle
diffractometer
782 independent reflections
Radiation source: fine-focus sealed tube506 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.081
ω scansθmax = 25.0°, θmin = 3.1°
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
h = 88
Tmin = 0.338, Tmax = 0.656k = 2222
16371 measured reflectionsl = 3030
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)] = 0.036Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.100H atoms treated by a mixture of independent and constrained refinement
S = 1.02 w = 1/[σ2(Fo2) + (0.0552P)2 + 4.7275P]
where P = (Fo2 + 2Fc2)/3
782 reflections(Δ/σ)max < 0.001
49 parametersΔρmax = 0.24 e Å3
0 restraintsΔρmin = 0.25 e Å3
Crystal data top
C7H11N2+·BrV = 3512.4 (7) Å3
Mr = 203.09Z = 16
Orthorhombic, FdddMo Kα radiation
a = 6.9804 (8) ŵ = 4.61 mm1
b = 19.256 (2) ÅT = 293 K
c = 26.131 (3) Å0.30 × 0.20 × 0.10 mm
Data collection top
Siemens CCD three-circle
diffractometer
782 independent reflections
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
506 reflections with I > 2σ(I)
Tmin = 0.338, Tmax = 0.656Rint = 0.081
16371 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0360 restraints
wR(F2) = 0.100H atoms treated by a mixture of independent and constrained refinement
S = 1.02Δρmax = 0.24 e Å3
782 reflectionsΔρmin = 0.25 e Å3
49 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
Br10.62500.12500.04610 (2)0.0789 (3)
N10.62500.2684 (3)0.12500.0857 (18)
H10.62500.22380.12500.103*
C20.6323 (7)0.3009 (3)0.0821 (2)0.0774 (13)
H20.63790.27550.05190.093*
C30.6320 (6)0.3706 (3)0.07967 (19)0.0723 (12)
H30.63640.39270.04800.087*
C40.62500.4105 (3)0.12500.0573 (13)
N40.62500.4797 (3)0.12500.105 (2)
C410.6313 (11)0.5190 (4)0.0780 (5)0.163 (3)
H41A0.66110.48860.05000.244*
H41B0.72790.55430.08050.244*
H41C0.50890.54040.07210.244*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.1215 (6)0.0590 (4)0.0563 (4)0.0044 (4)0.0000.000
N10.059 (3)0.051 (3)0.147 (6)0.0000.020 (6)0.000
C20.055 (3)0.078 (3)0.099 (3)0.003 (3)0.000 (3)0.030 (3)
C30.050 (2)0.097 (3)0.070 (3)0.011 (4)0.008 (2)0.015 (2)
C40.034 (2)0.044 (3)0.095 (4)0.0000.003 (3)0.000
N40.063 (3)0.051 (3)0.201 (8)0.0000.026 (6)0.000
C410.109 (5)0.089 (4)0.291 (10)0.004 (4)0.002 (7)0.103 (6)
Geometric parameters (Å, º) top
N1—C21.284 (6)C4—N41.332 (7)
N1—C2i1.285 (6)C4—C3i1.413 (6)
C2—C31.344 (7)N4—C41i1.444 (9)
C3—C41.412 (6)N4—C411.444 (9)
C2—N1—C2i121.7 (6)C3—C4—C3i114.1 (5)
N1—C2—C3121.9 (5)C4—N4—C41i121.6 (5)
C2—C3—C4120.2 (5)C4—N4—C41121.6 (5)
N4—C4—C3122.9 (3)C41i—N4—C41116.7 (9)
N4—C4—C3i122.9 (3)
C2i—N1—C2—C30.2 (3)C3—C4—N4—C41i179.7 (4)
N1—C2—C3—C40.5 (7)C3i—C4—N4—C41i0.3 (4)
C2—C3—C4—N4179.8 (3)C3—C4—N4—C410.3 (4)
C2—C3—C4—C3i0.2 (3)C3i—C4—N4—C41179.7 (4)
Symmetry code: (i) x+5/4, y, z+1/4.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···Br10.862.803.446 (4)133
N1—H1···Br1i0.862.803.446 (4)133
C2—H2···Br10.932.903.516 (5)125
C3—H3···Br1ii0.932.993.699 (5)134
Symmetry codes: (i) x+5/4, y, z+1/4; (ii) x+3/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC7H11N2+·Br
Mr203.09
Crystal system, space groupOrthorhombic, Fddd
Temperature (K)293
a, b, c (Å)6.9804 (8), 19.256 (2), 26.131 (3)
V3)3512.4 (7)
Z16
Radiation typeMo Kα
µ (mm1)4.61
Crystal size (mm)0.30 × 0.20 × 0.10
Data collection
DiffractometerSiemens CCD three-circle
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.338, 0.656
No. of measured, independent and
observed [I > 2σ(I)] reflections
16371, 782, 506
Rint0.081
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.036, 0.100, 1.02
No. of reflections782
No. of parameters49
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.24, 0.25

Computer programs: SMART (Siemens, 1995), SAINT (Siemens, 1995), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···Br10.862.803.446 (4)132.7
N1—H1···Br1i0.862.803.446 (4)132.7
C2—H2···Br10.932.903.516 (5)124.7
C3—H3···Br1ii0.932.993.699 (5)134.2
Symmetry codes: (i) x+5/4, y, z+1/4; (ii) x+3/2, y+1/2, z.
 

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