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Oxidation of tetrahydrodispirobenzimidazole by
m-chloroperbenzoic acid did not produce dispiro-2
H-benzimidazole, which is the product obtained by oxidation with MnO
2. Instead, a mixture of two compounds was identified, namely dispiro[2
H-benzimidazole-2,1′-cyclohexane-4′,2′′-[2
H]benzimidazole] 1-oxide, C
18H
16N
4O, (III), and dispiro[2
H-benzimidazole-2,1′-cyclohexane-4′,2′′-[2
H]benzimidazole] 1,1′′-dioxide, C
18H
16N
4O
2, (IV). In (III), the molecules are disordered about a twofold rotation axis and have 2/
m site symmetry. In (IV), the crystals are triclinic and the molecules occupy crystallographic inversion centers. Although the two compounds are very similar and are arranged in layers, they adopt completely different packing modes within the layers,
viz. herring-bone in (III) and parallel molecules in (IV). The molecules within the layers are held together by C—H
O and C—H
N hydrogen bonds.
Supporting information
CCDC references: 183032; 183033
Compound (I) was synthesized according to the procedure of Herbert et al.
(1988) (see Scheme 1). Monooxyl (III) and dioxyl (IV) were prepared by
oxidation of (I) (0.29 g, 1 mmol) by dropwise addition over 20 min of an ether
solution of m-chloroperbenzoic acid (MPCA; 0.95 g, 5.5 mmol) at 273 K.
Overnight stirring produced a yellow solution which was washed with 5%
Na2CO3, dried (K2CO3) and evaporated. After chromatography of the
resulting solid over silica gel with CHCl3, two substances were isolated,
monooxyl (III) [90 mg, 30%; MS (M++1): 305] and dioxyl (IV) [118 mg,
37%; MS: (M++1) 321].
The positions of all H atoms were located in a difference Fourier map and they
were refined as riding on their attached atoms (C—H = 0.95 and 0.99 Å).
Data collection: COLLECT (Nonius, 1998) for (III); Philips PW1100/20 Software (Philips, 1973) for (IV). Cell refinement: DENZO-SMN (Otwinowski & Minor, 1997) for (III); Philips PW1100/20 Software for (IV). Data reduction: DENZO-SMN for (III); Philips PW1100/20 Software for (IV). Program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a) for (III); SHELXS97 (Sheldrick, 1997) for (IV). Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b) for (III); SHELXL97 (Sheldrick, 1997) for (IV). Molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) for (III); ORTEP-3 (Farrugia, 1997) for (IV).
(III) Dispiro[2
H-benzimidazole-2,1'-cyclohexane-4',2''-
[2H]benzimidazole],1,-oxide
top
Crystal data top
C18H16N4O | Dx = 1.395 Mg m−3 |
Mr = 304.35 | Mo Kα radiation, λ = 0.71069 Å |
Orthorhombic, Cmca | Cell parameters from 902 reflections |
a = 6.774 (2) Å | θ = 0.9–27.5° |
b = 15.875 (3) Å | µ = 0.09 mm−1 |
c = 13.477 (3) Å | T = 150 K |
V = 1449.3 (6) Å3 | Prism, orange–red |
Z = 4 | 0.50 × 0.35 × 0.30 mm |
F(000) = 640 | |
Data collection top
Nonius KappaCCD diffractometer | 658 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.054 |
Graphite monochromator | θmax = 27.5°, θmin = 2.6° |
ϕ and ω scans | h = 0→8 |
3482 measured reflections | k = −20→20 |
902 independent reflections | l = −16→17 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.043 | H-atom parameters constrained |
wR(F2) = 0.119 | w = 1/[σ2(Fo2) + (0.0602P)2 + 0.5909P] where P = (Fo2 + 2Fc2)/3 |
S = 1.02 | (Δ/σ)max < 0.001 |
902 reflections | Δρmax = 0.22 e Å−3 |
77 parameters | Δρmin = −0.17 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.038 (5) |
Crystal data top
C18H16N4O | V = 1449.3 (6) Å3 |
Mr = 304.35 | Z = 4 |
Orthorhombic, Cmca | Mo Kα radiation |
a = 6.774 (2) Å | µ = 0.09 mm−1 |
b = 15.875 (3) Å | T = 150 K |
c = 13.477 (3) Å | 0.50 × 0.35 × 0.30 mm |
Data collection top
Nonius KappaCCD diffractometer | 658 reflections with I > 2σ(I) |
3482 measured reflections | Rint = 0.054 |
902 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.119 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.22 e Å−3 |
902 reflections | Δρmin = −0.17 e Å−3 |
77 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 | x | y | z | Uiso*/Ueq | Occ. (<1) |
O1 | 0.0000 | 0.02025 (17) | 0.2498 (2) | 0.0400 (7) | 0.50 |
N1 | 0.0000 | 0.07428 (11) | 0.19275 (12) | 0.0355 (5) | |
N2 | 0.0000 | 0.14359 (11) | 0.03727 (12) | 0.0352 (5) | |
C1 | 0.0000 | 0.15606 (13) | 0.20659 (14) | 0.0326 (5) | |
C2 | 0.0000 | 0.20307 (13) | 0.29706 (14) | 0.0340 (5) | |
C3 | 0.0000 | 0.28779 (14) | 0.28967 (15) | 0.0372 (5) | |
C4 | 0.0000 | 0.33013 (14) | 0.19452 (16) | 0.0393 (6) | |
C5 | 0.0000 | 0.28830 (14) | 0.10753 (16) | 0.0398 (6) | |
C6 | 0.0000 | 0.19724 (12) | 0.11008 (14) | 0.0320 (5) | |
C7 | 0.0000 | 0.06067 (12) | 0.08329 (15) | 0.0343 (5) | |
C8 | 0.1861 (2) | 0.01152 (10) | 0.05516 (10) | 0.0371 (4) | |
H2 | 0.0000 | 0.1758 | 0.3598 | 0.045 (7)* | |
H3 | 0.0000 | 0.3206 | 0.3486 | 0.046 (7)* | |
H4 | 0.0000 | 0.3900 | 0.1934 | 0.052 (7)* | |
H5 | 0.0000 | 0.3178 | 0.0462 | 0.046 (7)* | |
H81 | 0.3041 | 0.0460 | 0.0703 | 0.046 (4)* | |
H82 | 0.1935 | −0.0406 | 0.0954 | 0.043 (4)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0594 (19) | 0.0318 (15) | 0.0290 (14) | 0.000 | 0.000 | 0.0079 (14) |
N1 | 0.0363 (10) | 0.0402 (10) | 0.0301 (9) | 0.000 | 0.000 | −0.0075 (8) |
N2 | 0.0376 (10) | 0.0384 (10) | 0.0296 (9) | 0.000 | 0.000 | −0.0055 (7) |
C1 | 0.0282 (10) | 0.0408 (11) | 0.0288 (10) | 0.000 | 0.000 | −0.0062 (8) |
C2 | 0.0328 (11) | 0.0414 (12) | 0.0279 (10) | 0.000 | 0.000 | −0.0069 (9) |
C3 | 0.0356 (12) | 0.0436 (12) | 0.0325 (11) | 0.000 | 0.000 | −0.0116 (9) |
C4 | 0.0384 (12) | 0.0362 (12) | 0.0432 (12) | 0.000 | 0.000 | −0.0056 (9) |
C5 | 0.0451 (13) | 0.0387 (12) | 0.0356 (11) | 0.000 | 0.000 | 0.0017 (9) |
C6 | 0.0325 (11) | 0.0351 (11) | 0.0284 (10) | 0.000 | 0.000 | −0.0046 (8) |
C7 | 0.0353 (11) | 0.0343 (11) | 0.0334 (11) | 0.000 | 0.000 | −0.0104 (8) |
C8 | 0.0318 (8) | 0.0404 (9) | 0.0392 (9) | 0.0005 (6) | −0.0021 (6) | −0.0123 (6) |
Geometric parameters (Å, º) top
O1—N1 | 1.152 (3) | C3—H3 | 0.9500 |
N1—C1 | 1.312 (3) | C4—C5 | 1.348 (3) |
N1—C7 | 1.491 (3) | C4—H4 | 0.9500 |
N2—C6 | 1.299 (2) | C5—C6 | 1.446 (3) |
N2—C7 | 1.455 (3) | C5—H5 | 0.9500 |
C1—C2 | 1.430 (3) | C7—C8i | 1.5303 (18) |
C1—C6 | 1.456 (3) | C7—C8 | 1.5303 (18) |
C2—C3 | 1.349 (3) | C8—C8ii | 1.531 (3) |
C2—H2 | 0.9500 | C8—H81 | 0.9900 |
C3—C4 | 1.448 (3) | C8—H82 | 0.9900 |
| | | |
O1—N1—C1 | 130.0 (2) | C4—C5—H5 | 120.9 |
O1—N1—C7 | 123.5 (2) | C6—C5—H5 | 120.9 |
C1—N1—C7 | 106.51 (16) | N2—C6—C5 | 129.59 (19) |
C6—N2—C7 | 105.73 (16) | N2—C6—C1 | 112.36 (18) |
N1—C1—C2 | 129.65 (19) | C5—C6—C1 | 118.05 (17) |
N1—C1—C6 | 108.51 (16) | N2—C7—N1 | 106.89 (15) |
C2—C1—C6 | 121.84 (19) | N2—C7—C8i | 110.83 (12) |
C3—C2—C1 | 117.24 (19) | N1—C7—C8i | 108.60 (11) |
C3—C2—H2 | 121.4 | N2—C7—C8 | 110.83 (12) |
C1—C2—H2 | 121.4 | N1—C7—C8 | 108.60 (11) |
C2—C3—C4 | 121.90 (19) | C8i—C7—C8 | 110.94 (16) |
C2—C3—H3 | 119.1 | C8ii—C8—C7 | 111.24 (12) |
C4—C3—H3 | 119.1 | C8ii—C8—H81 | 109.4 |
C5—C4—C3 | 122.8 (2) | C7—C8—H81 | 109.4 |
C5—C4—H4 | 118.6 | C8ii—C8—H82 | 109.4 |
C3—C4—H4 | 118.6 | C7—C8—H82 | 109.4 |
C4—C5—C6 | 118.2 (2) | H81—C8—H82 | 108.0 |
| | | |
O1—N1—C1—C2 | 0.0 | N1—C1—C6—C5 | 180.0 |
C7—N1—C1—C2 | 180.0 | C2—C1—C6—C5 | 0.0 |
O1—N1—C1—C6 | 180.0 | C6—N2—C7—N1 | 0.0 |
C7—N1—C1—C6 | 0.0 | C6—N2—C7—C8i | 118.18 (12) |
N1—C1—C2—C3 | 180.0 | C6—N2—C7—C8 | −118.18 (12) |
C6—C1—C2—C3 | 0.0 | O1—N1—C7—N2 | 180.0 |
C1—C2—C3—C4 | 0.0 | C1—N1—C7—N2 | 0.0 |
C2—C3—C4—C5 | 0.0 | O1—N1—C7—C8i | 60.37 (11) |
C3—C4—C5—C6 | 0.0 | C1—N1—C7—C8i | −119.63 (11) |
C7—N2—C6—C5 | 180.0 | O1—N1—C7—C8 | −60.37 (11) |
C7—N2—C6—C1 | 0.0 | C1—N1—C7—C8 | 119.63 (11) |
C4—C5—C6—N2 | 180.0 | N2—C7—C8—C8ii | −67.98 (18) |
C4—C5—C6—C1 | 0.0 | N1—C7—C8—C8ii | 174.88 (14) |
N1—C1—C6—N2 | 0.0 | C8i—C7—C8—C8ii | 55.6 (2) |
C2—C1—C6—N2 | 180.0 | | |
Symmetry codes: (i) −x, y, z; (ii) x, −y, −z. |
(IV) dispiro [2
H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole],
1,1''-dioxide
top
Crystal data top
C18H16N4O2 | Z = 1 |
Mr = 320.34 | F(000) = 168 |
Triclinic, P1 | Dx = 1.411 Mg m−3 |
a = 5.416 (2) Å | Mo Kα radiation, λ = 0.71069 Å |
b = 7.290 (2) Å | Cell parameters from 25 reflections |
c = 10.426 (3) Å | θ = 3.1–12.2° |
α = 104.39 (3)° | µ = 0.10 mm−1 |
β = 104.15 (3)° | T = 293 K |
γ = 98.41 (3)° | Plate, yellow |
V = 377.1 (2) Å3 | 0.4 × 0.3 × 0.25 mm |
Data collection top
Philips PW1100 diffractometer | Rint = 0.036 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.1° |
Graphite monochromator | h = −6→6 |
ω/2θ scans | k = −8→8 |
1422 measured reflections | l = 0→12 |
1339 independent reflections | 3 standard reflections every 120 min |
885 reflections with I > 2σ(I) | intensity decay: 7.3% |
Refinement top
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)] = 0.053 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.139 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0567P)2 + 0.0683P] where P = (Fo2 + 2Fc2)/3 |
1339 reflections | (Δ/σ)max < 0.001 |
117 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
Crystal data top
C18H16N4O2 | γ = 98.41 (3)° |
Mr = 320.34 | V = 377.1 (2) Å3 |
Triclinic, P1 | Z = 1 |
a = 5.416 (2) Å | Mo Kα radiation |
b = 7.290 (2) Å | µ = 0.10 mm−1 |
c = 10.426 (3) Å | T = 293 K |
α = 104.39 (3)° | 0.4 × 0.3 × 0.25 mm |
β = 104.15 (3)° | |
Data collection top
Philips PW1100 diffractometer | Rint = 0.036 |
1422 measured reflections | 3 standard reflections every 120 min |
1339 independent reflections | intensity decay: 7.3% |
885 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.053 | 0 restraints |
wR(F2) = 0.139 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.20 e Å−3 |
1339 reflections | Δρmin = −0.18 e Å−3 |
117 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 | x | y | z | Uiso*/Ueq | |
O1 | −0.0836 (4) | 0.7268 (3) | 0.3112 (2) | 0.0567 (6) | |
N1 | 0.0766 (4) | 0.7937 (3) | 0.2539 (2) | 0.0381 (6) | |
N2 | 0.2981 (4) | 0.8060 (3) | 0.0879 (2) | 0.0372 (6) | |
C1 | 0.2504 (5) | 0.9603 (4) | 0.2994 (3) | 0.0362 (6) | |
C2 | 0.3161 (6) | 1.1149 (4) | 0.4242 (3) | 0.0449 (7) | |
C3 | 0.5157 (6) | 1.2607 (4) | 0.4436 (3) | 0.0517 (8) | |
C4 | 0.6519 (6) | 1.2672 (4) | 0.3419 (3) | 0.0521 (8) | |
C5 | 0.5908 (6) | 1.1253 (4) | 0.2206 (3) | 0.0470 (8) | |
C6 | 0.3842 (5) | 0.9614 (4) | 0.1951 (3) | 0.0360 (6) | |
C7 | 0.0962 (5) | 0.6816 (4) | 0.1158 (3) | 0.0338 (6) | |
C8 | −0.1671 (5) | 0.6423 (4) | 0.0080 (3) | 0.0399 (7) | |
C9 | 0.1757 (5) | 0.4932 (4) | 0.1304 (3) | 0.0389 (7) | |
H2 | 0.2249 | 1.1148 | 0.4890 | 0.066 (10)* | |
H3 | 0.5684 | 1.3616 | 0.5259 | 0.046 (8)* | |
H4 | 0.7873 | 1.3734 | 0.3603 | 0.045 (8)* | |
H5 | 0.6800 | 1.1335 | 0.1557 | 0.058 (9)* | |
H81 | −0.3026 | 0.5852 | 0.0414 | 0.054 (8)* | |
H82 | −0.2026 | 0.7643 | −0.0047 | 0.051 (8)* | |
H91 | 0.3512 | 0.5239 | 0.1929 | 0.033 (6)* | |
H92 | 0.0592 | 0.4280 | 0.1705 | 0.044 (8)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0637 (14) | 0.0596 (13) | 0.0520 (13) | 0.0013 (10) | 0.0365 (11) | 0.0136 (10) |
N1 | 0.0409 (13) | 0.0416 (13) | 0.0351 (12) | 0.0062 (10) | 0.0198 (11) | 0.0104 (10) |
N2 | 0.0371 (12) | 0.0403 (13) | 0.0360 (12) | 0.0063 (10) | 0.0140 (10) | 0.0124 (10) |
C1 | 0.0406 (15) | 0.0363 (15) | 0.0325 (14) | 0.0104 (12) | 0.0103 (12) | 0.0112 (11) |
C2 | 0.0604 (19) | 0.0427 (17) | 0.0342 (16) | 0.0166 (15) | 0.0159 (14) | 0.0107 (13) |
C3 | 0.074 (2) | 0.0330 (16) | 0.0382 (17) | 0.0129 (15) | 0.0049 (15) | 0.0045 (13) |
C4 | 0.0565 (19) | 0.0384 (17) | 0.0560 (19) | 0.0009 (14) | 0.0084 (16) | 0.0177 (15) |
C5 | 0.0501 (18) | 0.0441 (17) | 0.0474 (18) | 0.0015 (14) | 0.0173 (15) | 0.0170 (14) |
C6 | 0.0412 (15) | 0.0391 (15) | 0.0313 (14) | 0.0119 (12) | 0.0110 (12) | 0.0147 (12) |
C7 | 0.0345 (14) | 0.0338 (14) | 0.0310 (14) | 0.0054 (11) | 0.0123 (11) | 0.0048 (11) |
C8 | 0.0355 (15) | 0.0388 (16) | 0.0441 (16) | 0.0106 (12) | 0.0114 (13) | 0.0088 (12) |
C9 | 0.0358 (15) | 0.0433 (16) | 0.0343 (15) | 0.0069 (12) | 0.0060 (12) | 0.0111 (12) |
Geometric parameters (Å, º) top
O1—N1 | 1.273 (3) | C4—H4 | 0.9300 |
N1—C1 | 1.322 (3) | C5—C6 | 1.434 (4) |
N1—C7 | 1.505 (3) | C5—H5 | 0.9300 |
N2—C6 | 1.308 (3) | C7—C8 | 1.522 (4) |
N2—C7 | 1.449 (3) | C7—C9 | 1.530 (4) |
C1—C2 | 1.420 (4) | C8—C9i | 1.518 (3) |
C1—C6 | 1.447 (4) | C8—H81 | 0.9700 |
C2—C3 | 1.337 (4) | C8—H82 | 0.9700 |
C2—H2 | 0.9300 | C9—C8i | 1.518 (3) |
C3—C4 | 1.438 (4) | C9—H91 | 0.9700 |
C3—H3 | 0.9300 | C9—H92 | 0.9700 |
C4—C5 | 1.351 (4) | | |
| | | |
O1—N1—C1 | 129.2 (2) | N2—C6—C1 | 113.6 (2) |
O1—N1—C7 | 122.3 (2) | C5—C6—C1 | 118.1 (2) |
C1—N1—C7 | 108.5 (2) | N2—C7—N1 | 105.13 (19) |
C6—N2—C7 | 106.3 (2) | N2—C7—C8 | 112.0 (2) |
N1—C1—C2 | 131.2 (3) | N1—C7—C8 | 108.63 (19) |
N1—C1—C6 | 106.4 (2) | N2—C7—C9 | 111.1 (2) |
C2—C1—C6 | 122.4 (3) | N1—C7—C9 | 107.9 (2) |
C3—C2—C1 | 116.6 (3) | C8—C7—C9 | 111.7 (2) |
C3—C2—H2 | 121.7 | C9i—C8—C7 | 112.1 (2) |
C1—C2—H2 | 121.7 | C9i—C8—H81 | 109.2 |
C2—C3—C4 | 122.5 (3) | C7—C8—H81 | 109.2 |
C2—C3—H3 | 118.8 | C9i—C8—H82 | 109.2 |
C4—C3—H3 | 118.8 | C7—C8—H82 | 109.2 |
C5—C4—C3 | 122.6 (3) | H81—C8—H82 | 107.9 |
C5—C4—H4 | 118.7 | C8i—C9—C7 | 112.0 (2) |
C3—C4—H4 | 118.7 | C8i—C9—H91 | 109.2 |
C4—C5—C6 | 117.8 (3) | C7—C9—H91 | 109.2 |
C4—C5—H5 | 121.1 | C8i—C9—H92 | 109.2 |
C6—C5—H5 | 121.1 | C7—C9—H92 | 109.2 |
N2—C6—C5 | 128.3 (2) | H91—C9—H92 | 107.9 |
| | | |
O1—N1—C1—C2 | 0.6 (5) | C2—C1—C6—C5 | 0.3 (4) |
C7—N1—C1—C2 | −178.3 (3) | C6—N2—C7—N1 | 1.5 (3) |
O1—N1—C1—C6 | 178.9 (3) | C6—N2—C7—C8 | 119.3 (2) |
C7—N1—C1—C6 | 0.1 (3) | C6—N2—C7—C9 | −115.0 (2) |
N1—C1—C2—C3 | 175.8 (3) | O1—N1—C7—N2 | −179.9 (2) |
C6—C1—C2—C3 | −2.3 (4) | C1—N1—C7—N2 | −1.0 (3) |
C1—C2—C3—C4 | 2.7 (4) | O1—N1—C7—C8 | 60.1 (3) |
C2—C3—C4—C5 | −1.1 (5) | C1—N1—C7—C8 | −121.0 (2) |
C3—C4—C5—C6 | −1.0 (4) | O1—N1—C7—C9 | −61.2 (3) |
C7—N2—C6—C5 | 177.5 (3) | C1—N1—C7—C9 | 117.7 (2) |
C7—N2—C6—C1 | −1.6 (3) | N2—C7—C8—C9i | 72.0 (3) |
C4—C5—C6—N2 | −177.8 (3) | N1—C7—C8—C9i | −172.3 (2) |
C4—C5—C6—C1 | 1.3 (4) | C9—C7—C8—C9i | −53.4 (3) |
N1—C1—C6—N2 | 1.0 (3) | N2—C7—C9—C8i | −72.6 (3) |
C2—C1—C6—N2 | 179.5 (2) | N1—C7—C9—C8i | 172.7 (2) |
N1—C1—C6—C5 | −178.2 (2) | C8—C7—C9—C8i | 53.3 (3) |
Symmetry code: (i) −x, −y+1, −z. |
Experimental details
| (III) | (IV) |
Crystal data |
Chemical formula | C18H16N4O | C18H16N4O2 |
Mr | 304.35 | 320.34 |
Crystal system, space group | Orthorhombic, Cmca | Triclinic, P1 |
Temperature (K) | 150 | 293 |
a, b, c (Å) | 6.774 (2), 15.875 (3), 13.477 (3) | 5.416 (2), 7.290 (2), 10.426 (3) |
α, β, γ (°) | 90, 90.00 (3), 90 | 104.39 (3), 104.15 (3), 98.41 (3) |
V (Å3) | 1449.3 (6) | 377.1 (2) |
Z | 4 | 1 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.09 | 0.10 |
Crystal size (mm) | 0.50 × 0.35 × 0.30 | 0.4 × 0.3 × 0.25 |
|
Data collection |
Diffractometer | Nonius KappaCCD diffractometer | Philips PW1100 diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3482, 902, 658 | 1422, 1339, 885 |
Rint | 0.054 | 0.036 |
(sin θ/λ)max (Å−1) | 0.649 | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.119, 1.02 | 0.053, 0.139, 1.06 |
No. of reflections | 902 | 1339 |
No. of parameters | 77 | 117 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.22, −0.17 | 0.20, −0.18 |
Comparison of bond lengths (Å) for (III), (IV), (VI), (VII), (VIII).
and bond angles (°) for (III) and (IV). top | (III) | (IV) | (VI) | (VII) | (VIII) |
O1—N1 | 1.152 (3) | 1.273 (3) | 1.28 (2)/1.34 (3) | | |
N1—C1 | 1.312 (3) | 1.322 (3) | 1.34 (3) | 1.30 (1) | 1.399 (7) |
N1—C7 | 1.491 (3) | 1.505 (3) | 1.54 (3) | 1.506 (8) | 1.491 (7) |
N2—C6 | 1.299 (2) | 1.308 (3) | 1.33 (3) | 1.30 (1) | 1.403 (7) |
N2—C7 | 1.455 (3) | 1.449 (3) | 1.52 (3) | 1.48 (1) | 1.480 (8) |
C1—C2 | 1.430 (3) | 1.420 (4) | 1.42 (3) | 1.463 (9) | 1.383 (7) |
C1—C6 | 1.456 (3) | 1.447 (4) | 1.41 (3) | 1.48 (1) | 1.375 (7) |
C2—C3 | 1.349 (3) | 1.337 (4) | 1.41 (4) | 1.36 (1) | 1.402 (7) |
C3—C4 | 1.448 (3) | 1.438 (4) | 1.41 (4) | 1.51 (2) | 1.389 (9) |
C4—C5 | 1.348 (3) | 1.351 (4) | 1.40 (4) | 1.36 (1) | 1.402 (9) |
C5—C6 | 1.446 (3) | 1.434 (4) | 1.45 (4) | 1.43 (2) | 1.363 (8) |
C7—C8 | 1.530 (2) | 1.522 (4) | | | |
C7—C8* | 1.530 (2) | 1.530 (4) | | | |
C8—C8* | 1.531 (3) | 1.518 (3) | | | |
| | | | | |
O1—N1—C1 | 130.0 (2) | 129.2 (2) | | | |
O1—N1—C7 | 123.5 (2) | 122.3 (2) | | | |
C1—N1—C7 | 106.5 (2) | 108.5 (2) | | | |
C6—N2—C7 | 105.7 (2) | 106.3 (2) | | | |
N1—C1—C2 | 129.6 (2) | 131.2 (3) | | | |
N1—C1—C6 | 108.5 (2) | 106.4 (2) | | | |
C2—C1—C6 | 121.8 (2) | 122.4 (3) | | | |
C3—C2—C1 | 117.2 (2) | 116.6 (3) | | | |
C2—C3—C4 | 121.9 (2) | 122.5 (3) | | | |
C5—C4—C3 | 122.8 (2) | 122.6 (3) | | | |
C4—C5—C6 | 118.2 (2) | 117.8 (3) | | | |
N2—C6—C5 | 129.6 (2) | 128.3 (2) | | | |
N2—C6—C1 | 112.4 (2) | 113.6 (2) | | | |
C5—C6—C1 | 118.0 (2) | 118.1 (2) | | | |
N2—C7—N1 | 106.9 (2) | 105.1 (2) | | | |
N2—C7—C8 | 110.8 (1) | 112.0 (2) | | | |
N1—C7—C8 | 109.0 (1) | 108.6 (2) | | | |
N2—C7—C8* | 110.8 (1) | 111.1 (2) | | | |
N1—C7—C8* | 108.6 (1) | 107.9 (2) | | | |
C8—C7—C8* | 110.9 (2) | 111.7 (2) | | | |
C8*—C8—C7 | 111.2 (1) | 112.1 (2) | | | |
C8—C8*—C7 | 111.2 (1) | 112.0 (2) | | | |
Notes: atoms marked with an asterisk are related by either twofold symmetry
[in (III)] or by an inversion center [in (IV)]. |
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We have attempted to prepare tetranitroxide (V) (see Scheme 1) by a procedure similar to that described by Keana et al. (1967, 1978). Following the guidelines of Davies et al. (1984) and Herbert et al. (1988), dispiro(2H-benzimidazole-2,1'-cyclohexane-4,2''-[2H]benzimidazole), (I), was prepared. Oxidation of (I) by MnO2 led to the dispiro-2H-benzimidazole (II) (Herbert et al., 1988) (see Scheme 2). Further oxidation by m-chloroperbenzoic acid (von Glahn et al., 1999) produced (E)- and (Z)-dispiro[2H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole] 1,1''-dioxide, i.e. (IV) and (IV'), respectively (see Scheme 2). We carried out the oxidation of (I) by m-chloroperbenzoic acid, skipping the oxidation step with MnO2. Two major products were identified, namely dispiro[2H-benzimidazole-2,1'-cyclohexane-4', 2''-[2H]benzimidazole] 1-oxide, (III), and dispiro[2H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole] 1,1''-dioxide, (IV). Although the chemical difference between the two compounds is small, the crystal structures are completely different. Monoxide (III) crystallizes in the orthorhombic space group Cmca, occupying the 2/m crystallographic site symmetry. This means that the O atom is equally disordered between two sites related by a twofold symmetry axis. The crystals of dioxide (IV) are triclinic and the molecule occupies a crystallographic inversion center. The packing of the molecules of (III) and (IV) in the unit cells are shown in Figs. 1 and 2, respectively. In both, the molecules form layers but the arrangement of molecules within the layer is different. While the molecules in (III) adopt a herring=bone packing motif, the molecules are parallel in (IV). The molecules within a layer are held together by short intermolecular O···H—C and N···H—C contacts. Only two such contacts that were observed in the crystal structure of (III) could be considered hydrogen bonds: O1···H4 2.205 (3) Å, O1···C4 3.110 (3) Å and O1···H4—C4 158.7 (2)°; N2···H3 2.605 (3) Å, N2···C3 3.510 Å and N2···H3—C3 159.3 (2)°. In (IV), there is only one hydrogen bond [O1···H2 2.470 (4) Å, O1···C2 3.327 (4) Å and O1···H2—C2 153.4 (3)°]. The packing of the layers is also very different. While the molecules between successive layers in (IV) are related by translation, those in (III) are related by a twofold rotation axis perpendicular to the benzimidazole portions of the molecules (see Figs. 3 and 4). A comparison of bond lengths and angles is given in Table 1. Also compared in Table 1 are the bond lengths of the relevant moiety in benzimidazole dioxide (VI) (Keller et al., 1977), benzimidazole (VII), and dihydrobenzimidazole (VIII) (Hazelton et al., 1995) (see Scheme 3). The localization of double bonds in the benzene ring is clearly observed in (III), (IV) and (VII), where the C2—C3 and C4—C5 bonds are significantly shorter than C1—C2, C3—C4, C5—C6 and C1—C6 (see notation in Fig. 1), while in (VI) and (VIII) these bonds are normal for aromatic compounds. Some bond lengths should be noted; the N1—O1 bond length is significantly shorter in monooxyl (III) [1.152 (3) Å] than in dioxyl (IV) [1.274 (3) Å], and (VI) [1.28 (2) and 1.34 (3) Å]. The experimental geometry at the nitroxide group in (III) is strongly affected by the disorder. The disordered moiety is an average between benzimidazole [such as (VI)] and benzimidazoleoxide [such as (VII)]. The position of atom N1 is an average between two sites. The distance between the theoretical positions of the two sites is only 0.12 Å and all attempts to refine these positions separately or by fixing them failed to provide more reliable geometry. The N1═C1 and N2═C6 bond lengths are chemically equivalent within each of the compounds (VI), (VII) and (VIII), and therefore the bond lengths are equal within each molecule either as localized double bonds in (VII) [1.30 (1) and 1.30 (1) Å], localized Nsp3—Csp2 single bonds in (VIII) [1.399 (7) and 1.403 (7) Å] or delocalized double bonds in (VII) [1.34 (3) and 1.33 (3) Å]. These bonds in (IV) are significantly different [N1═C1 1.320 (3) Å and N2═C6 1.307 (3) Å] because only one of the two N atoms is connected to the electronegative atom O1; therefore the later is compared to the equivalent bond in (VI), and the former should be compared with that in (VII). The N2═ C6 bond in (IV) is not affected by the disorder and therefore the bond length of 1.303 (3) Å is similar to that found in (VII). The N1═C1 bond length in (III) is somewhat longer [1.312 (3) Å] as a result of the disorder. The presence of (III) in the reaction bath might suggest that the oxidation takes place in two steps. In the first step, the monooxyl is formed and in the second step, the second N atom is oxidized.