Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199016133/qb0146sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270199016133/qb0146Isup2.hkl |
CCDC reference: 140861
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.
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 C—H(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.
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).
C7H11N2+·Br− | F(000) = 1632 |
Mr = 203.09 | Dx = 1.536 Mg m−3 |
Orthorhombic, Fddd | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -F 2uv 2vw | Cell parameters from 502 reflections |
a = 6.9804 (8) Å | θ = 1–20° |
b = 19.256 (2) Å | µ = 4.61 mm−1 |
c = 26.131 (3) Å | T = 293 K |
V = 3512.4 (7) Å3 | Plate, colourless |
Z = 16 | 0.30 × 0.20 × 0.10 mm |
Siemens CCD three-circle diffractometer | 782 independent reflections |
Radiation source: fine-focus sealed tube | 506 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.081 |
ω scans | θmax = 25.0°, θmin = 3.1° |
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996) | h = −8→8 |
Tmin = 0.338, Tmax = 0.656 | k = −22→22 |
16371 measured reflections | l = −30→30 |
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)] = 0.036 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.100 | H 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 parameters | Δρmax = 0.24 e Å−3 |
0 restraints | Δρmin = −0.25 e Å−3 |
C7H11N2+·Br− | V = 3512.4 (7) Å3 |
Mr = 203.09 | Z = 16 |
Orthorhombic, Fddd | Mo Kα radiation |
a = 6.9804 (8) Å | µ = 4.61 mm−1 |
b = 19.256 (2) Å | T = 293 K |
c = 26.131 (3) Å | 0.30 × 0.20 × 0.10 mm |
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 = 0.656 | Rint = 0.081 |
16371 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 0 restraints |
wR(F2) = 0.100 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.02 | Δρmax = 0.24 e Å−3 |
782 reflections | Δρmin = −0.25 e Å−3 |
49 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. |
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 | ||
Br1 | 0.6250 | 0.1250 | 0.04610 (2) | 0.0789 (3) | |
N1 | 0.6250 | 0.2684 (3) | 0.1250 | 0.0857 (18) | |
H1 | 0.6250 | 0.2238 | 0.1250 | 0.103* | |
C2 | 0.6323 (7) | 0.3009 (3) | 0.0821 (2) | 0.0774 (13) | |
H2 | 0.6379 | 0.2755 | 0.0519 | 0.093* | |
C3 | 0.6320 (6) | 0.3706 (3) | 0.07967 (19) | 0.0723 (12) | |
H3 | 0.6364 | 0.3927 | 0.0480 | 0.087* | |
C4 | 0.6250 | 0.4105 (3) | 0.1250 | 0.0573 (13) | |
N4 | 0.6250 | 0.4797 (3) | 0.1250 | 0.105 (2) | |
C41 | 0.6313 (11) | 0.5190 (4) | 0.0780 (5) | 0.163 (3) | |
H41A | 0.6611 | 0.4886 | 0.0500 | 0.244* | |
H41B | 0.7279 | 0.5543 | 0.0805 | 0.244* | |
H41C | 0.5089 | 0.5404 | 0.0721 | 0.244* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.1215 (6) | 0.0590 (4) | 0.0563 (4) | −0.0044 (4) | 0.000 | 0.000 |
N1 | 0.059 (3) | 0.051 (3) | 0.147 (6) | 0.000 | −0.020 (6) | 0.000 |
C2 | 0.055 (3) | 0.078 (3) | 0.099 (3) | 0.003 (3) | 0.000 (3) | −0.030 (3) |
C3 | 0.050 (2) | 0.097 (3) | 0.070 (3) | 0.011 (4) | 0.008 (2) | 0.015 (2) |
C4 | 0.034 (2) | 0.044 (3) | 0.095 (4) | 0.000 | 0.003 (3) | 0.000 |
N4 | 0.063 (3) | 0.051 (3) | 0.201 (8) | 0.000 | 0.026 (6) | 0.000 |
C41 | 0.109 (5) | 0.089 (4) | 0.291 (10) | 0.004 (4) | −0.002 (7) | 0.103 (6) |
N1—C2 | 1.284 (6) | C4—N4 | 1.332 (7) |
N1—C2i | 1.285 (6) | C4—C3i | 1.413 (6) |
C2—C3 | 1.344 (7) | N4—C41i | 1.444 (9) |
C3—C4 | 1.412 (6) | N4—C41 | 1.444 (9) |
C2—N1—C2i | 121.7 (6) | C3—C4—C3i | 114.1 (5) |
N1—C2—C3 | 121.9 (5) | C4—N4—C41i | 121.6 (5) |
C2—C3—C4 | 120.2 (5) | C4—N4—C41 | 121.6 (5) |
N4—C4—C3 | 122.9 (3) | C41i—N4—C41 | 116.7 (9) |
N4—C4—C3i | 122.9 (3) | ||
C2i—N1—C2—C3 | −0.2 (3) | C3—C4—N4—C41i | −179.7 (4) |
N1—C2—C3—C4 | 0.5 (7) | C3i—C4—N4—C41i | 0.3 (4) |
C2—C3—C4—N4 | 179.8 (3) | C3—C4—N4—C41 | 0.3 (4) |
C2—C3—C4—C3i | −0.2 (3) | C3i—C4—N4—C41 | −179.7 (4) |
Symmetry code: (i) −x+5/4, y, −z+1/4. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Br1 | 0.86 | 2.80 | 3.446 (4) | 133 |
N1—H1···Br1i | 0.86 | 2.80 | 3.446 (4) | 133 |
C2—H2···Br1 | 0.93 | 2.90 | 3.516 (5) | 125 |
C3—H3···Br1ii | 0.93 | 2.99 | 3.699 (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 formula | C7H11N2+·Br− |
Mr | 203.09 |
Crystal system, space group | Orthorhombic, Fddd |
Temperature (K) | 293 |
a, b, c (Å) | 6.9804 (8), 19.256 (2), 26.131 (3) |
V (Å3) | 3512.4 (7) |
Z | 16 |
Radiation type | Mo Kα |
µ (mm−1) | 4.61 |
Crystal size (mm) | 0.30 × 0.20 × 0.10 |
Data collection | |
Diffractometer | Siemens CCD three-circle diffractometer |
Absorption correction | Empirical (using intensity measurements) (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.338, 0.656 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 16371, 782, 506 |
Rint | 0.081 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.100, 1.02 |
No. of reflections | 782 |
No. of parameters | 49 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.24, −0.25 |
Computer programs: SMART (Siemens, 1995), SAINT (Siemens, 1995), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Br1 | 0.86 | 2.80 | 3.446 (4) | 132.7 |
N1—H1···Br1i | 0.86 | 2.80 | 3.446 (4) | 132.7 |
C2—H2···Br1 | 0.93 | 2.90 | 3.516 (5) | 124.7 |
C3—H3···Br1ii | 0.93 | 2.99 | 3.699 (5) | 134.2 |
Symmetry codes: (i) −x+5/4, y, −z+1/4; (ii) −x+3/2, −y+1/2, −z. |
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.