Download citation
Download citation
link to html
The title compound, meso-1,2-bis­(methyl­diazenyl)-1,2-di­phenyl­ethane, C16H18N4, is arranged in a disordered manner around an inversion point. The N-N atom distances in the azo group of 1.192 (8) and 1.195 (8) Å, and the C-C atom distances in the ethyl­ene moiety at 1.512 (8) and 1.503 (8) Å in the two models [refined to 51.7 (6) and 48.3 (6)% occupancies] were not significantly different.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101015918/da1209sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101015918/da1209Isup2.hkl
Contains datablock I

CCDC reference: 179273

Comment top

The syntheses of vicinal bis(azo)alkanes can be achieved through the oxidation of hydrazones by various reagents (Winter & Wiecko, 1969; Balachandran et al., 1968; Bhatnagar & George, 1967). Depending upon the substituents on the azo groups, the compound can decompose by breaking the C—N bonds and eliminating nitrogen and alkyl radicals to form an alkene (Engel et al., 1991). If the terminal R group is aryl, the central C—C bond is broken to form two α-hydrazonyl radicals (Wieko, 1970; Engel et al., 1993).

So far, there are only six structural reports on vicinal bis(azo) compounds (Allen et al., 1983). Our interest in these compounds stems from the possibility of low-temperature production of methyl radicals through simultaneous or near-simultaneous loss of nitrogen. Here, we report the crystal structure of a vicinal bis(azo)alkane, namely meso-1,2-bis(methylazo)-1,2-diphenylethane, (I).

There is disorder in the arrangement of the entire molecule. As a result, the N—N distances [1.192 (8) and 1.195 (8) Å] are slightly shorter than expected (ca 1.22 Å) compared to other methylazo compounds (van Remoortere & Boer, 1971; Ferguson et al., 1991). The two central C—C bond distances are comparable, but shorter [1.512 (8) and 1.503 (8) Å versus 1.532–1.555 Å] than two known bis(azo)alkanes (Kavounis & Rentzeperis, 1983, 1984). The C—N distances involving the central ethylene bridge [1.487 (8) and 1.477 (8) Å] are also not significantly different and are comparable to those in the above bis(azo)alkanes (1.465–1.520 Å; Kavounis & Rentzeperis, 1983, 1984). The methylazo C—N bond distances [1.494 (6) and 1.489 (6) Å] are also comparable to previous crystal structures (van Remoortere & Boer, 1971; Ferguson et al., 1991).

Related literature top

For related literature, see: Allen et al. (1983); Balachandran et al. (1968); Bayse et al. (2001); Bhatnagar & George (1967); Engel et al. (1991, 1993); Ferguson et al. (1991); Kavounis & Rentzeperis (1983, 1984); Remoortere & Boer (1971); Winter & Wiecko (1969).

Experimental top

The title compound was synthesized by the oxidation of benzaldehyde methylhydrazone with MnO2 as detailed in a separate publication (Bayse et al., 2001). The product was obtained as crystals from the reaction mixture. Suitable crystals for X-ray diffraction were obtained by recrystallization from chloroform.

Refinement top

In the original structure solution, the disorder in the positions of the C atoms in the ethylene moiety was apparent. This model was refined with first isotropic and then anisotropic displacement parameters to convergence. The positions and isotropic displacement parameters of the H atoms were constrained and set to 1.5 times (1.2 for aryl H atoms) the isotropic equivalent of the attached atoms. At this stage, due to some unusual bond distances and angles, a new model was constructed which required restraints (24 in total, C—C = 1.39 Å) to prevent correlation from hindering the refinement. This resulted in different orientations in the phenyl rings, for the N atoms of the azo groups and for the C atoms of the ethylene moiety. Only the C atom in the methyl group was unique, but this was refined with two sets of H atoms to better fit the two independent models.

Computing details top

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. ORTEP-3 (Farrugia, 1997) views of (a) molecule A and (b) molecule B of (I) (50% probability displacement ellipsoids).
(I) top
Crystal data top
C16H18N4F(000) = 256
Mr = 266.35Dx = 1.172 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71069 Å
a = 5.525 (2) ÅCell parameters from 25 reflections
b = 17.444 (3) Åθ = 10–15°
c = 8.194 (2) ŵ = 0.07 mm1
β = 107.10 (2)°T = 293 K
V = 754.8 (4) Å3Prism, white
Z = 20.40 × 0.20 × 0.10 mm
Data collection top
Enraf-Nonius Turbo-CAD4
diffractometer
Rint = 0.016
non–profiled ω/2θ scansθmax = 25.0°, θmin = 2.3°
Absorption correction: ψ scan
(North et al., 1968)
h = 06
Tmin = 0.970, Tmax = 0.992k = 020
1465 measured reflectionsl = 99
1324 independent reflections3 standard reflections every 166 min
687 reflections with I > 2σ(I) intensity decay: 1%
Refinement top
Refinement on F224 restraints
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.056 w = 1/[σ2(Fo2) + (0.0763P)2 + 0.1301P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.170(Δ/σ)max = 0.012
S = 1.01Δρmax = 0.18 e Å3
1324 reflectionsΔρmin = 0.13 e Å3
107 parameters
Crystal data top
C16H18N4V = 754.8 (4) Å3
Mr = 266.35Z = 2
Monoclinic, P21/nMo Kα radiation
a = 5.525 (2) ŵ = 0.07 mm1
b = 17.444 (3) ÅT = 293 K
c = 8.194 (2) Å0.40 × 0.20 × 0.10 mm
β = 107.10 (2)°
Data collection top
Enraf-Nonius Turbo-CAD4
diffractometer
687 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.016
Tmin = 0.970, Tmax = 0.9923 standard reflections every 166 min
1465 measured reflections intensity decay: 1%
1324 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.05624 restraints
wR(F2) = 0.170H-atom parameters constrained
S = 1.01Δρmax = 0.18 e Å3
1324 reflectionsΔρmin = 0.13 e Å3
107 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
N1A0.7237 (17)0.0451 (13)0.3475 (13)0.072 (2)0.517 (6)
N2A0.6975 (10)0.0722 (3)0.2098 (6)0.079 (2)0.517 (6)
C1A1.030 (3)0.1049 (8)0.5936 (18)0.0546 (18)0.517 (6)
C2A1.217 (3)0.1600 (8)0.6111 (16)0.0590 (17)0.517 (6)
H2A1.32740.15730.54440.071*0.517 (6)
C3A1.240 (3)0.2193 (7)0.7281 (14)0.058 (2)0.517 (6)
H3A1.36590.25620.73980.069*0.517 (6)
C4A1.076 (3)0.2233 (8)0.8277 (17)0.060 (2)0.517 (6)
H4A1.09150.2630.9060.073*0.517 (6)
C5A0.889 (3)0.1682 (9)0.8102 (18)0.064 (2)0.517 (6)
H5A0.77860.17090.87690.076*0.517 (6)
C6A0.866 (3)0.1089 (9)0.6932 (17)0.0603 (18)0.517 (6)
H6A0.74010.0720.68150.072*0.517 (6)
C7A0.9889 (13)0.0394 (3)0.4601 (9)0.058 (2)0.517 (6)
H7A1.10790.04460.39260.069*0.517 (6)
C8A0.4260 (6)0.08370 (19)0.1109 (4)0.1016 (12)0.517 (6)
H8A10.41580.10450.00060.152*0.517 (6)
H8A20.34870.11860.17120.152*0.517 (6)
H8A30.3390.03540.09720.152*0.517 (6)
N1B0.7669 (16)0.0530 (14)0.3206 (14)0.072 (2)0.483 (6)
N2B0.5411 (10)0.0517 (3)0.2850 (6)0.0692 (19)0.483 (6)
C1B0.984 (3)0.0975 (9)0.612 (2)0.0546 (18)0.483 (6)
C2B1.165 (3)0.1460 (9)0.5813 (17)0.0590 (17)0.483 (6)
H2B1.23960.1340.49630.071*0.483 (6)
C3B1.236 (3)0.2123 (8)0.6774 (16)0.058 (2)0.483 (6)
H3B1.3570.24480.65680.069*0.483 (6)
C4B1.124 (3)0.2303 (8)0.8043 (19)0.060 (2)0.483 (6)
H4B1.17150.27470.86860.073*0.483 (6)
C5B0.943 (3)0.1818 (9)0.8351 (18)0.064 (2)0.483 (6)
H5B0.86860.19380.920.076*0.483 (6)
C6B0.873 (3)0.1154 (9)0.7390 (19)0.0603 (18)0.483 (6)
H6B0.75120.0830.75960.072*0.483 (6)
C7B0.8922 (13)0.0268 (5)0.4967 (9)0.063 (2)0.483 (6)
H7B0.76730.00060.53830.076*0.483 (6)
C8B0.4260 (6)0.08370 (19)0.1109 (4)0.1016 (12)0.483 (6)
H8B10.24480.08120.08290.152*0.483 (6)
H8B20.48130.05440.02930.152*0.483 (6)
H8B30.47760.13610.10810.152*0.483 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N1A0.082 (3)0.062 (4)0.057 (3)0.009 (3)0.003 (3)0.010 (3)
N2A0.094 (4)0.071 (3)0.060 (4)0.014 (3)0.006 (3)0.009 (3)
C1A0.060 (5)0.043 (3)0.056 (3)0.001 (2)0.010 (2)0.004 (3)
C2A0.052 (6)0.062 (5)0.055 (4)0.011 (3)0.002 (4)0.015 (3)
C3A0.071 (2)0.062 (3)0.035 (7)0.009 (2)0.008 (4)0.009 (3)
C4A0.066 (6)0.051 (3)0.061 (4)0.002 (2)0.014 (3)0.002 (3)
C5A0.055 (6)0.066 (5)0.064 (4)0.009 (3)0.009 (5)0.018 (3)
C6A0.0676 (19)0.067 (3)0.043 (7)0.0130 (19)0.012 (4)0.008 (3)
C7A0.055 (4)0.053 (4)0.066 (4)0.003 (3)0.022 (3)0.002 (3)
C8A0.107 (3)0.082 (2)0.079 (2)0.0164 (19)0.0293 (19)0.0047 (18)
N1B0.082 (3)0.062 (4)0.057 (3)0.009 (3)0.003 (3)0.010 (3)
N2B0.060 (4)0.070 (3)0.068 (4)0.004 (3)0.004 (3)0.005 (3)
C1B0.060 (5)0.043 (3)0.056 (3)0.001 (2)0.010 (2)0.004 (3)
C2B0.052 (6)0.062 (5)0.055 (4)0.011 (3)0.002 (4)0.015 (3)
C3B0.071 (2)0.062 (3)0.035 (7)0.009 (2)0.008 (4)0.009 (3)
C4B0.066 (6)0.051 (3)0.061 (4)0.002 (2)0.014 (3)0.002 (3)
C5B0.055 (6)0.066 (5)0.064 (4)0.009 (3)0.009 (5)0.018 (3)
C6B0.0676 (19)0.067 (3)0.043 (7)0.0130 (19)0.012 (4)0.008 (3)
C7B0.049 (4)0.076 (5)0.061 (5)0.016 (4)0.010 (4)0.006 (3)
C8B0.107 (3)0.082 (2)0.079 (2)0.0164 (19)0.0293 (19)0.0047 (18)
Geometric parameters (Å, º) top
N1A—N2A1.192 (8)N1B—N2B1.195 (8)
N1A—C7A1.487 (8)N1B—C7B1.477 (8)
N2A—C8A1.494 (6)N2B—C8B1.489 (6)
C1A—C2A1.39C1B—C2B1.39
C1A—C6A1.39C1B—C6B1.39
C1A—C7A1.551 (5)C1B—C7B1.545 (6)
C2A—C3A1.39C2B—C3B1.39
C3A—C4A1.39C3B—C4B1.39
C4A—C5A1.39C4B—C5B1.39
C5A—C6A1.39C5B—C6B1.39
C7A—C7Ai1.512 (8)C7B—C7Bi1.503 (8)
N2A—N1A—C7A115.9 (9)N2B—N1B—C7B112.9 (9)
N1A—N2A—C8A113.0 (7)N1B—N2B—C8B110.4 (7)
C2A—C1A—C6A120C2B—C1B—C6B120
C2A—C1A—C7A122.2 (5)C2B—C1B—C7B119.9 (6)
C6A—C1A—C7A117.8 (5)C6B—C1B—C7B120.0 (6)
C1A—C2A—C3A120C1B—C2B—C3B120
C2A—C3A—C4A120C2B—C3B—C4B120
C5A—C4A—C3A120C5B—C4B—C3B120
C4A—C5A—C6A120C6B—C5B—C4B120
C5A—C6A—C1A120C5B—C6B—C1B120
N1A—C7A—C7Ai105.6 (9)N1B—C7B—C7Bi111.5 (10)
N1A—C7A—C1A107.5 (7)N1B—C7B—C1B109.0 (8)
C7Ai—C7A—C1A112.8 (11)C7Bi—C7B—C1B111.2 (12)
Symmetry code: (i) x+2, y, z+1.

Experimental details

Crystal data
Chemical formulaC16H18N4
Mr266.35
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)5.525 (2), 17.444 (3), 8.194 (2)
β (°) 107.10 (2)
V3)754.8 (4)
Z2
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.40 × 0.20 × 0.10
Data collection
DiffractometerEnraf-Nonius Turbo-CAD4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.970, 0.992
No. of measured, independent and
observed [I > 2σ(I)] reflections
1465, 1324, 687
Rint0.016
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.170, 1.01
No. of reflections1324
No. of parameters107
No. of restraints24
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.18, 0.13

Computer programs: CAD-4 EXPRESS (Enraf-Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

 

Follow Acta Cryst. C
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds