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The cation of the title compound, C12H15N2O+·CF3SO3, exists as an E-configured hydroxy­imino derivative conjugated with a nearly planar iminium system. The twist angle between the phenyl ring and the oxime group is 72.2 (2)°. An O—H...O hydrogen bond links the oxime group of the cation to the anion.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100020448/bm1441sup1.cif
Contains datablocks global, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100020448/bm1441IIsup2.hkl
Contains datablock II

CCDC reference: 169933

Comment top

1-Heterosubstituted 2-nitroethylene derivatives undergo polyprotonations in trifluoromethanesulfonic acid that lead to loss of water and formation of hydroxynitrilium ions, or O-protonated nitrile oxides, which are fairly electrophilic (Coustard, 1995, 1996, 1999). In this medium, 1-methyl-2-nitromethylenepyrrolidine, (I), also undergoes this transformation, leading to the corresponding hydroxynitrilium ion (scheme), which reacts with benzene to afford a stable dication observable either by 1H or 13C NMR spectroscopy. Quenching with water affords the title compound, (II), which is stable in acidic or neutral aqueous solution. In basic solution, deprotonation of the OH oxime group leads to formation of a conjugated nitroso derivative which dimerizes readily to give a mixture of isomers. In compound (II), the presence of a trifluoromethanesulfonate anion, phenyl ring and oxime (or hydroxyimino) group was expected from 1H and 13NMR data (Coustard, 1999). However, the configuration of the oxime is important from a mechanistic point of view and needed to be confirmed. The unusual behavior of this salt also prompted us to undertake the present X-ray crystallographic analysis. \sch

Most of the cation is nearly planar (Fig. 1), but the aromatic ring lies out of the plane, with a C12—C7—C6—N6 torsion angle of 72.2 (2)°. The maximum deviation of the atoms defining the least-squares mean plane through O6, N6, C6, C5, N1 and C13 is observed for C6 and N6, with respective values of -0.116 Å and 0.098 Å. The atoms of the five-membered ring C5/N1/C2/C3/C4 are also approximately coplanar, with maximum deviations from the least-squares mean plane of -0.114 Å for C4 and 0.135 Å for C3.

The O6—N6—C6—C7 torsion angle of -5.0 (2)° indicates a E-configured oxime group; the adjacent C6—C5 bond adopts an s-trans conformation [N1—C5—C6—N6 - 170.2 (3)°]. Such an oxime configuration has also been reported for products resulting from hydroxynitrilium ion trapping (Cousson & Coustard, 1998, 1999).

Conjugation of the N6—C6—C5—N1 double-bond system allows delocalization of the positive charge and accounts for the lengthening of both the C6—C5 single bond [1.469 (2) Å, compared with the expected value for a single bond in a dienic conjugated system of 1.455 (11) Å; Allen et al., 1987] and the C6—N6 double bond [1.290 (2) Å, compared with the expected value in an unconjugated oxime of 1.280 (13) Å; Allen et al., 1987].

The relatively short distance of 2.651 (2) Å between atom O1 of the trifluoromethanesulfonate anion and the oxime oxygen O6 implies a hydrogen bond involving H6 [H6···O1 1.69 and O6···O1 2.651 (2) Å, and O6—H6···O1 177°].

The O3i···N2 and O3i···C5 distances [symmetry code: (i) 1 - x, 1/2 + y, 1/2 - z] of 2.855 (2) and 2.873 (2) Å, respectively, are shorter than expected, the sum of the relevant van der Waals sums (Bondi, 1964) being 3.07 and 3.22 Å. A search of the Cambridge Structural Database (Allen & Kennard, 1993; October 2000 Version) for the fragment F3C—SO3···NC indicates that about half the 25 or so occurrences have generally similar distances to those above. In the present case, the short distances may result from the formation of some kind of π-adduct between the π-electrons of the CN double bond and the O3 atom of the trifluoromethanesulfonate anion. In agreement with this hypothesis is the fact that the O3i atom is almost equidistant from N2 and C5, and the dihedral angle between the N2/O3i/C5 and N1/C2/C3/C4/C5 planes is 97.54°, indicating that they are almost perpendicular.

In conclusion, compound (II) may be considered as resulting from O-protonation of the nitroso group of α-(N-methyl-1-azacyclopent-1-en-2-yl)-α-nitrosotoluene by trifluoromethanesulfonic acid. The oxime group thus formed is E-configured, in agreement with an electrophilic aromatic substitution mechanism involving the C N of the transient hydroxynitrilium ion (Hegarty et al., 1980; Nguyen et al., 1991).

Experimental top

The title compound was prepared as described by Coustard (1999).

Refinement top

H atoms on C were placed geometrically and the H atom on O was located in a difference Fourier synthesis. C—H distances were fixed at 1.00 Å and the O—H distance was fixed at 0.96 Å. A common Uiso parameter for all H atoms converged at 0.046 (2) Å2. Query - not methyl H.

Structure description top

1-Heterosubstituted 2-nitroethylene derivatives undergo polyprotonations in trifluoromethanesulfonic acid that lead to loss of water and formation of hydroxynitrilium ions, or O-protonated nitrile oxides, which are fairly electrophilic (Coustard, 1995, 1996, 1999). In this medium, 1-methyl-2-nitromethylenepyrrolidine, (I), also undergoes this transformation, leading to the corresponding hydroxynitrilium ion (scheme), which reacts with benzene to afford a stable dication observable either by 1H or 13C NMR spectroscopy. Quenching with water affords the title compound, (II), which is stable in acidic or neutral aqueous solution. In basic solution, deprotonation of the OH oxime group leads to formation of a conjugated nitroso derivative which dimerizes readily to give a mixture of isomers. In compound (II), the presence of a trifluoromethanesulfonate anion, phenyl ring and oxime (or hydroxyimino) group was expected from 1H and 13NMR data (Coustard, 1999). However, the configuration of the oxime is important from a mechanistic point of view and needed to be confirmed. The unusual behavior of this salt also prompted us to undertake the present X-ray crystallographic analysis. \sch

Most of the cation is nearly planar (Fig. 1), but the aromatic ring lies out of the plane, with a C12—C7—C6—N6 torsion angle of 72.2 (2)°. The maximum deviation of the atoms defining the least-squares mean plane through O6, N6, C6, C5, N1 and C13 is observed for C6 and N6, with respective values of -0.116 Å and 0.098 Å. The atoms of the five-membered ring C5/N1/C2/C3/C4 are also approximately coplanar, with maximum deviations from the least-squares mean plane of -0.114 Å for C4 and 0.135 Å for C3.

The O6—N6—C6—C7 torsion angle of -5.0 (2)° indicates a E-configured oxime group; the adjacent C6—C5 bond adopts an s-trans conformation [N1—C5—C6—N6 - 170.2 (3)°]. Such an oxime configuration has also been reported for products resulting from hydroxynitrilium ion trapping (Cousson & Coustard, 1998, 1999).

Conjugation of the N6—C6—C5—N1 double-bond system allows delocalization of the positive charge and accounts for the lengthening of both the C6—C5 single bond [1.469 (2) Å, compared with the expected value for a single bond in a dienic conjugated system of 1.455 (11) Å; Allen et al., 1987] and the C6—N6 double bond [1.290 (2) Å, compared with the expected value in an unconjugated oxime of 1.280 (13) Å; Allen et al., 1987].

The relatively short distance of 2.651 (2) Å between atom O1 of the trifluoromethanesulfonate anion and the oxime oxygen O6 implies a hydrogen bond involving H6 [H6···O1 1.69 and O6···O1 2.651 (2) Å, and O6—H6···O1 177°].

The O3i···N2 and O3i···C5 distances [symmetry code: (i) 1 - x, 1/2 + y, 1/2 - z] of 2.855 (2) and 2.873 (2) Å, respectively, are shorter than expected, the sum of the relevant van der Waals sums (Bondi, 1964) being 3.07 and 3.22 Å. A search of the Cambridge Structural Database (Allen & Kennard, 1993; October 2000 Version) for the fragment F3C—SO3···NC indicates that about half the 25 or so occurrences have generally similar distances to those above. In the present case, the short distances may result from the formation of some kind of π-adduct between the π-electrons of the CN double bond and the O3 atom of the trifluoromethanesulfonate anion. In agreement with this hypothesis is the fact that the O3i atom is almost equidistant from N2 and C5, and the dihedral angle between the N2/O3i/C5 and N1/C2/C3/C4/C5 planes is 97.54°, indicating that they are almost perpendicular.

In conclusion, compound (II) may be considered as resulting from O-protonation of the nitroso group of α-(N-methyl-1-azacyclopent-1-en-2-yl)-α-nitrosotoluene by trifluoromethanesulfonic acid. The oxime group thus formed is E-configured, in agreement with an electrophilic aromatic substitution mechanism involving the C N of the transient hydroxynitrilium ion (Hegarty et al., 1980; Nguyen et al., 1991).

Computing details top

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998); cell refinement: DENZO; data reduction: DENZO; program(s) used to solve structure: SHELXS86 (Sheldrick, 1986); program(s) used to refine structure: CRYSTALS (Watkin, Prout, Carruthers & Betteridge, 1996); molecular graphics: CAMERON (Watkin, Prout & Pearce, 1996); software used to prepare material for publication: CRYSTALS.

Figures top
[Figure 1] Fig. 1. The molecular view of (II) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii.
(E)-5-[Hydroxyimino(phenyl)methyl]-1-methyl-3,4-dihydro-2H-pyrrolium trifluoromethanesulfonate top
Crystal data top
C12H15N2O+·CF3SO3Dx = 1.511 Mg m3
Mr = 352.33Melting point = 386.5–389 K
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 11.7643 (5) ÅCell parameters from 11326 reflections
b = 8.2154 (4) Åθ = 1–28°
c = 16.5207 (6) ŵ = 0.26 mm1
β = 104.10 (2)°T = 120 K
V = 1548.6 Å3Plate, colourless
Z = 40.25 × 0.20 × 0.10 mm
F(000) = 728.77
Data collection top
Nonius KappaCCD area-detector
diffractometer
Rint = 0.036
Graphite monochromatorθmax = 28°, θmin = 1°
φ rotation scans with 2° stepsh = 1515
11326 measured reflectionsk = 910
3595 independent reflectionsl = 2119
2749 reflections with I > 3σ(I)
Refinement top
Refinement on FPrimary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044H-atom parameters constrained
wR(F2) = 0.054 Chebychev polynomial with 3 parameters, 0.683, 0.650 and 0.343 (Carruthers & Watkin, 1979)
S = 1.03(Δ/σ)max = 0.001
2749 reflectionsΔρmax = 0.67 e Å3
209 parametersΔρmin = 0.49 e Å3
Crystal data top
C12H15N2O+·CF3SO3V = 1548.6 Å3
Mr = 352.33Z = 4
Monoclinic, P21/cMo Kα radiation
a = 11.7643 (5) ŵ = 0.26 mm1
b = 8.2154 (4) ÅT = 120 K
c = 16.5207 (6) Å0.25 × 0.20 × 0.10 mm
β = 104.10 (2)°
Data collection top
Nonius KappaCCD area-detector
diffractometer
2749 reflections with I > 3σ(I)
11326 measured reflectionsRint = 0.036
3595 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.044209 parameters
wR(F2) = 0.054H-atom parameters constrained
S = 1.03Δρmax = 0.67 e Å3
2749 reflectionsΔρmin = 0.49 e Å3
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
S10.23655 (4)0.77001 (6)0.07596 (3)0.0293
O10.30177 (11)0.92007 (15)0.07503 (8)0.0288
O20.15339 (18)0.7745 (3)0.12625 (12)0.0590
O30.30712 (14)0.62638 (18)0.08194 (11)0.0458
O60.52897 (11)0.89981 (18)0.14656 (8)0.0325
N10.68740 (13)0.77957 (18)0.42736 (9)0.0234
N60.52186 (13)0.88205 (19)0.22798 (9)0.0265
C20.64478 (17)0.7695 (2)0.50482 (11)0.0292
C30.51219 (17)0.7596 (2)0.47273 (11)0.0306
C40.48847 (16)0.8280 (2)0.38356 (11)0.0287
C50.60483 (15)0.8092 (2)0.3618 (1)0.0235
C60.61798 (15)0.8287 (2)0.2761 (1)0.0236
C70.72305 (14)0.7776 (2)0.2472 (1)0.0237
C80.74806 (15)0.6124 (2)0.24575 (11)0.0271
C90.84465 (17)0.5598 (3)0.21780 (12)0.0324
C100.91529 (16)0.6732 (3)0.19139 (12)0.0359
C110.89034 (17)0.8379 (3)0.19271 (12)0.0355
C120.79380 (16)0.8913 (2)0.22050 (12)0.0317
C130.81448 (15)0.7725 (2)0.43582 (11)0.0281
C140.14536 (18)0.7633 (3)0.03011 (14)0.0382
F10.07281 (12)0.88976 (18)0.0453 (1)0.0582
F20.21115 (14)0.7675 (2)0.08562 (9)0.0593
F30.08090 (12)0.62762 (17)0.0437 (1)0.0540
H60.44720.91000.11960.0530 (19)*
H210.66790.86910.54000.0476 (19)*
H220.67600.67080.53780.0476 (19)*
H310.47190.82760.50780.0476 (19)*
H320.48430.64480.47210.0476 (19)*
H410.46450.94530.38180.0476 (19)*
H420.42570.76420.34430.0476 (19)*
H810.69660.53240.26510.0476 (19)*
H910.86290.44100.21660.0476 (19)*
H1010.98450.63570.17100.0476 (19)*
H1110.94280.91970.17480.0476 (19)*
H1210.77481.00980.22060.0476 (19)*
H1310.83780.85460.40170.0527 (19)*
H1320.84560.80170.49210.0527 (19)*
H1330.83470.66330.42170.0527 (19)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0316 (2)0.0255 (2)0.0333 (2)0.00125 (17)0.01289 (17)0.00211 (17)
O10.0290 (6)0.0213 (6)0.0353 (6)0.0004 (5)0.0065 (5)0.0013 (5)
O20.0624 (11)0.0712 (12)0.0574 (11)0.0149 (9)0.0417 (9)0.0076 (9)
O30.0441 (8)0.0224 (7)0.0671 (11)0.0039 (6)0.0059 (7)0.0073 (7)
O60.0313 (7)0.0468 (8)0.0202 (6)0.0044 (6)0.0080 (5)0.0040 (5)
N10.0266 (7)0.0211 (6)0.0233 (6)0.0005 (5)0.0072 (5)0.0006 (5)
N60.0305 (7)0.0298 (7)0.0209 (6)0.0020 (6)0.0096 (5)0.0015 (5)
C20.0337 (9)0.0339 (9)0.0216 (7)0.0026 (7)0.0098 (6)0.0012 (7)
C30.0330 (9)0.036 (1)0.0260 (8)0.0011 (7)0.0131 (7)0.0019 (7)
C40.0282 (8)0.0348 (9)0.0247 (8)0.0016 (7)0.0094 (6)0.0007 (7)
C50.0266 (8)0.0215 (8)0.0234 (8)0.0010 (6)0.0080 (6)0.0006 (6)
C60.0267 (8)0.0222 (8)0.0231 (8)0.0019 (6)0.0086 (6)0.0003 (6)
C70.0231 (7)0.0289 (8)0.0195 (7)0.0018 (6)0.0061 (6)0.0009 (6)
C80.0277 (8)0.0280 (9)0.0269 (8)0.0017 (7)0.0093 (6)0.0002 (7)
C90.0301 (9)0.036 (1)0.0329 (9)0.0048 (8)0.0109 (7)0.0026 (7)
C100.0251 (8)0.0541 (12)0.0305 (9)0.0023 (8)0.0103 (7)0.0016 (8)
C110.0271 (9)0.0485 (12)0.0327 (9)0.0081 (8)0.0103 (7)0.0064 (8)
C120.0305 (9)0.033 (1)0.0313 (9)0.0047 (7)0.0081 (7)0.0057 (7)
C130.0247 (8)0.0300 (9)0.0285 (8)0.0015 (7)0.0043 (6)0.0009 (7)
C140.0314 (9)0.0365 (11)0.0456 (11)0.0041 (8)0.0070 (8)0.0023 (8)
F10.0392 (7)0.0469 (8)0.077 (1)0.0051 (6)0.0072 (7)0.0094 (7)
F20.0608 (9)0.0840 (12)0.0356 (7)0.0165 (8)0.0164 (6)0.0107 (7)
F30.0407 (7)0.0431 (8)0.072 (1)0.0138 (6)0.0023 (6)0.0118 (7)
Geometric parameters (Å, º) top
S1—O11.4541 (13)C5—C61.469 (2)
S1—O21.4300 (16)C6—C71.490 (2)
S1—O31.4323 (15)C7—C81.390 (3)
S1—C141.819 (2)C7—C121.392 (2)
O6—N61.3757 (18)C8—C91.396 (3)
O6—H60.96C8—H811.00
N1—C21.486 (2)C9—C101.388 (3)
N1—C51.290 (2)C9—H911.00
N1—C131.468 (2)C10—C111.386 (3)
N6—C61.290 (2)C10—H1011.00
C2—C31.522 (3)C11—C121.395 (3)
C2—H211.00C11—H1111.00
C2—H221.00C12—H1211.00
C3—C41.537 (2)C13—H1310.96
C3—H311.00C13—H1320.94
C3—H321.00C13—H1330.97
C4—C51.506 (2)C14—F11.329 (3)
C4—H411.00C14—F21.337 (3)
C4—H421.00C14—F31.336 (2)
O1—S1—O2114.9 (1)N6—C6—C7124.66 (15)
O1—S1—O3113.62 (9)C5—C6—C7124.65 (15)
O2—S1—O3116.65 (12)C6—C7—C8118.43 (15)
O1—S1—C14101.80 (9)C6—C7—C12121.29 (16)
O2—S1—C14103.54 (12)C8—C7—C12120.26 (16)
O3—S1—C14103.7 (1)C7—C8—C9120.08 (17)
N6—O6—H6100C7—C8—H81119
C2—N1—C5113.00 (14)C9—C8—H81121
C2—N1—C13117.72 (14)C8—C9—C10119.59 (18)
C5—N1—C13128.93 (15)C8—C9—H91120
O6—N6—C6112.70 (14)C10—C9—H91120
N1—C2—C3103.60 (14)C9—C10—C11120.36 (17)
N1—C2—H21111C9—C10—H101120
C3—C2—H21111C11—C10—H101120
N1—C2—H22111C10—C11—C12120.29 (18)
C3—C2—H22111C10—C11—H111120
H21—C2—H22110C12—C11—H111120
C2—C3—C4104.22 (14)C7—C12—C11119.41 (18)
C2—C3—H31111C7—C12—H121120
C4—C3—H31110C11—C12—H121120
C2—C3—H32111N1—C13—H131110
C4—C3—H32111N1—C13—H132103
H31—C3—H32109H131—C13—H132108
C3—C4—C5103.19 (14)N1—C13—H133109
C3—C4—H41111H131—C13—H133113
C5—C4—H41111H132—C13—H133114
C3—C4—H42111S1—C14—F1111.06 (15)
C5—C4—H42111S1—C14—F2110.85 (14)
H41—C4—H42109F1—C14—F2107.60 (19)
N1—C5—C4111.17 (15)S1—C14—F3111.39 (15)
N1—C5—C6126.52 (16)F1—C14—F3107.96 (16)
C4—C5—C6122.29 (15)F2—C14—F3107.83 (18)
N6—C6—C5110.41 (15)
C12—C7—C6—N672.0 (2)N1—C5—C6—N6170.0 (2)
O6—N6—C6—C74.9 (2)

Experimental details

Crystal data
Chemical formulaC12H15N2O+·CF3SO3
Mr352.33
Crystal system, space groupMonoclinic, P21/c
Temperature (K)120
a, b, c (Å)11.7643 (5), 8.2154 (4), 16.5207 (6)
β (°) 104.10 (2)
V3)1548.6
Z4
Radiation typeMo Kα
µ (mm1)0.26
Crystal size (mm)0.25 × 0.20 × 0.10
Data collection
DiffractometerNonius KappaCCD area-detector
Absorption correction
No. of measured, independent and
observed [I > 3σ(I)] reflections
11326, 3595, 2749
Rint0.036
(sin θ/λ)max1)0.661
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.054, 1.03
No. of reflections2749
No. of parameters209
No. of restraints?
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.67, 0.49

Computer programs: DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998), DENZO, SHELXS86 (Sheldrick, 1986), CRYSTALS (Watkin, Prout, Carruthers & Betteridge, 1996), CAMERON (Watkin, Prout & Pearce, 1996), CRYSTALS.

Selected geometric parameters (Å, º) top
S1—O11.4541 (13)C5—C61.469 (2)
S1—O21.4300 (16)C6—C71.490 (2)
S1—O31.4323 (15)C7—C81.390 (3)
S1—C141.819 (2)C7—C121.392 (2)
O6—N61.3757 (18)C8—C91.396 (3)
N1—C21.486 (2)C9—C101.388 (3)
N1—C51.290 (2)C10—C111.386 (3)
N1—C131.468 (2)C11—C121.395 (3)
N6—C61.290 (2)C14—F11.329 (3)
C2—C31.522 (3)C14—F21.337 (3)
C3—C41.537 (2)C14—F31.336 (2)
C4—C51.506 (2)
O1—S1—O2114.9 (1)N6—C6—C7124.66 (15)
O1—S1—O3113.62 (9)C5—C6—C7124.65 (15)
O2—S1—O3116.65 (12)C6—C7—C8118.43 (15)
O1—S1—C14101.80 (9)C6—C7—C12121.29 (16)
O2—S1—C14103.54 (12)C8—C7—C12120.26 (16)
O3—S1—C14103.7 (1)C7—C8—C9120.08 (17)
C2—N1—C5113.00 (14)C8—C9—C10119.59 (18)
C2—N1—C13117.72 (14)C9—C10—C11120.36 (17)
C5—N1—C13128.93 (15)C10—C11—C12120.29 (18)
O6—N6—C6112.70 (14)C7—C12—C11119.41 (18)
N1—C2—C3103.60 (14)S1—C14—F1111.06 (15)
C2—C3—C4104.22 (14)S1—C14—F2110.85 (14)
C3—C4—C5103.19 (14)F1—C14—F2107.60 (19)
N1—C5—C4111.17 (15)S1—C14—F3111.39 (15)
N1—C5—C6126.52 (16)F1—C14—F3107.96 (16)
C4—C5—C6122.29 (15)F2—C14—F3107.83 (18)
N6—C6—C5110.41 (15)
C12—C7—C6—N672.0 (2)N1—C5—C6—N6170.0 (2)
O6—N6—C6—C74.9 (2)
 

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