Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101015918/da1209sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101015918/da1209Isup2.hkl |
CCDC reference: 179273
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.
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.
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).
Fig. 1. ORTEP-3 (Farrugia, 1997) views of (a) molecule A and (b) molecule B of (I) (50% probability displacement ellipsoids). |
C16H18N4 | F(000) = 256 |
Mr = 266.35 | Dx = 1.172 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71069 Å |
a = 5.525 (2) Å | Cell parameters from 25 reflections |
b = 17.444 (3) Å | θ = 10–15° |
c = 8.194 (2) Å | µ = 0.07 mm−1 |
β = 107.10 (2)° | T = 293 K |
V = 754.8 (4) Å3 | Prism, white |
Z = 2 | 0.40 × 0.20 × 0.10 mm |
Enraf-Nonius Turbo-CAD4 diffractometer | Rint = 0.016 |
non–profiled ω/2θ scans | θmax = 25.0°, θmin = 2.3° |
Absorption correction: ψ scan (North et al., 1968) | h = 0→6 |
Tmin = 0.970, Tmax = 0.992 | k = 0→20 |
1465 measured reflections | l = −9→9 |
1324 independent reflections | 3 standard reflections every 166 min |
687 reflections with I > 2σ(I) | intensity decay: 1% |
Refinement on F2 | 24 restraints |
Least-squares matrix: full | H-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 = 1.01 | Δρmax = 0.18 e Å−3 |
1324 reflections | Δρmin = −0.13 e Å−3 |
107 parameters |
C16H18N4 | V = 754.8 (4) Å3 |
Mr = 266.35 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 5.525 (2) Å | µ = 0.07 mm−1 |
b = 17.444 (3) Å | T = 293 K |
c = 8.194 (2) Å | 0.40 × 0.20 × 0.10 mm |
β = 107.10 (2)° |
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 = 0.992 | 3 standard reflections every 166 min |
1465 measured reflections | intensity decay: 1% |
1324 independent reflections |
R[F2 > 2σ(F2)] = 0.056 | 24 restraints |
wR(F2) = 0.170 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.18 e Å−3 |
1324 reflections | Δρmin = −0.13 e Å−3 |
107 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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
N1A | 0.7237 (17) | 0.0451 (13) | 0.3475 (13) | 0.072 (2) | 0.517 (6) |
N2A | 0.6975 (10) | 0.0722 (3) | 0.2098 (6) | 0.079 (2) | 0.517 (6) |
C1A | 1.030 (3) | 0.1049 (8) | 0.5936 (18) | 0.0546 (18) | 0.517 (6) |
C2A | 1.217 (3) | 0.1600 (8) | 0.6111 (16) | 0.0590 (17) | 0.517 (6) |
H2A | 1.3274 | 0.1573 | 0.5444 | 0.071* | 0.517 (6) |
C3A | 1.240 (3) | 0.2193 (7) | 0.7281 (14) | 0.058 (2) | 0.517 (6) |
H3A | 1.3659 | 0.2562 | 0.7398 | 0.069* | 0.517 (6) |
C4A | 1.076 (3) | 0.2233 (8) | 0.8277 (17) | 0.060 (2) | 0.517 (6) |
H4A | 1.0915 | 0.263 | 0.906 | 0.073* | 0.517 (6) |
C5A | 0.889 (3) | 0.1682 (9) | 0.8102 (18) | 0.064 (2) | 0.517 (6) |
H5A | 0.7786 | 0.1709 | 0.8769 | 0.076* | 0.517 (6) |
C6A | 0.866 (3) | 0.1089 (9) | 0.6932 (17) | 0.0603 (18) | 0.517 (6) |
H6A | 0.7401 | 0.072 | 0.6815 | 0.072* | 0.517 (6) |
C7A | 0.9889 (13) | 0.0394 (3) | 0.4601 (9) | 0.058 (2) | 0.517 (6) |
H7A | 1.1079 | 0.0446 | 0.3926 | 0.069* | 0.517 (6) |
C8A | 0.4260 (6) | 0.08370 (19) | 0.1109 (4) | 0.1016 (12) | 0.517 (6) |
H8A1 | 0.4158 | 0.1045 | 0.0006 | 0.152* | 0.517 (6) |
H8A2 | 0.3487 | 0.1186 | 0.1712 | 0.152* | 0.517 (6) |
H8A3 | 0.339 | 0.0354 | 0.0972 | 0.152* | 0.517 (6) |
N1B | 0.7669 (16) | 0.0530 (14) | 0.3206 (14) | 0.072 (2) | 0.483 (6) |
N2B | 0.5411 (10) | 0.0517 (3) | 0.2850 (6) | 0.0692 (19) | 0.483 (6) |
C1B | 0.984 (3) | 0.0975 (9) | 0.612 (2) | 0.0546 (18) | 0.483 (6) |
C2B | 1.165 (3) | 0.1460 (9) | 0.5813 (17) | 0.0590 (17) | 0.483 (6) |
H2B | 1.2396 | 0.134 | 0.4963 | 0.071* | 0.483 (6) |
C3B | 1.236 (3) | 0.2123 (8) | 0.6774 (16) | 0.058 (2) | 0.483 (6) |
H3B | 1.357 | 0.2448 | 0.6568 | 0.069* | 0.483 (6) |
C4B | 1.124 (3) | 0.2303 (8) | 0.8043 (19) | 0.060 (2) | 0.483 (6) |
H4B | 1.1715 | 0.2747 | 0.8686 | 0.073* | 0.483 (6) |
C5B | 0.943 (3) | 0.1818 (9) | 0.8351 (18) | 0.064 (2) | 0.483 (6) |
H5B | 0.8686 | 0.1938 | 0.92 | 0.076* | 0.483 (6) |
C6B | 0.873 (3) | 0.1154 (9) | 0.7390 (19) | 0.0603 (18) | 0.483 (6) |
H6B | 0.7512 | 0.083 | 0.7596 | 0.072* | 0.483 (6) |
C7B | 0.8922 (13) | 0.0268 (5) | 0.4967 (9) | 0.063 (2) | 0.483 (6) |
H7B | 0.7673 | −0.0006 | 0.5383 | 0.076* | 0.483 (6) |
C8B | 0.4260 (6) | 0.08370 (19) | 0.1109 (4) | 0.1016 (12) | 0.483 (6) |
H8B1 | 0.2448 | 0.0812 | 0.0829 | 0.152* | 0.483 (6) |
H8B2 | 0.4813 | 0.0544 | 0.0293 | 0.152* | 0.483 (6) |
H8B3 | 0.4776 | 0.1361 | 0.1081 | 0.152* | 0.483 (6) |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1A | 0.082 (3) | 0.062 (4) | 0.057 (3) | 0.009 (3) | −0.003 (3) | 0.010 (3) |
N2A | 0.094 (4) | 0.071 (3) | 0.060 (4) | 0.014 (3) | 0.006 (3) | 0.009 (3) |
C1A | 0.060 (5) | 0.043 (3) | 0.056 (3) | −0.001 (2) | 0.010 (2) | 0.004 (3) |
C2A | 0.052 (6) | 0.062 (5) | 0.055 (4) | −0.011 (3) | 0.002 (4) | −0.015 (3) |
C3A | 0.071 (2) | 0.062 (3) | 0.035 (7) | −0.009 (2) | 0.008 (4) | −0.009 (3) |
C4A | 0.066 (6) | 0.051 (3) | 0.061 (4) | −0.002 (2) | 0.014 (3) | −0.002 (3) |
C5A | 0.055 (6) | 0.066 (5) | 0.064 (4) | −0.009 (3) | 0.009 (5) | −0.018 (3) |
C6A | 0.0676 (19) | 0.067 (3) | 0.043 (7) | −0.0130 (19) | 0.012 (4) | −0.008 (3) |
C7A | 0.055 (4) | 0.053 (4) | 0.066 (4) | 0.003 (3) | 0.022 (3) | −0.002 (3) |
C8A | 0.107 (3) | 0.082 (2) | 0.079 (2) | 0.0164 (19) | −0.0293 (19) | 0.0047 (18) |
N1B | 0.082 (3) | 0.062 (4) | 0.057 (3) | 0.009 (3) | −0.003 (3) | 0.010 (3) |
N2B | 0.060 (4) | 0.070 (3) | 0.068 (4) | 0.004 (3) | 0.004 (3) | 0.005 (3) |
C1B | 0.060 (5) | 0.043 (3) | 0.056 (3) | −0.001 (2) | 0.010 (2) | 0.004 (3) |
C2B | 0.052 (6) | 0.062 (5) | 0.055 (4) | −0.011 (3) | 0.002 (4) | −0.015 (3) |
C3B | 0.071 (2) | 0.062 (3) | 0.035 (7) | −0.009 (2) | 0.008 (4) | −0.009 (3) |
C4B | 0.066 (6) | 0.051 (3) | 0.061 (4) | −0.002 (2) | 0.014 (3) | −0.002 (3) |
C5B | 0.055 (6) | 0.066 (5) | 0.064 (4) | −0.009 (3) | 0.009 (5) | −0.018 (3) |
C6B | 0.0676 (19) | 0.067 (3) | 0.043 (7) | −0.0130 (19) | 0.012 (4) | −0.008 (3) |
C7B | 0.049 (4) | 0.076 (5) | 0.061 (5) | 0.016 (4) | 0.010 (4) | 0.006 (3) |
C8B | 0.107 (3) | 0.082 (2) | 0.079 (2) | 0.0164 (19) | −0.0293 (19) | 0.0047 (18) |
N1A—N2A | 1.192 (8) | N1B—N2B | 1.195 (8) |
N1A—C7A | 1.487 (8) | N1B—C7B | 1.477 (8) |
N2A—C8A | 1.494 (6) | N2B—C8B | 1.489 (6) |
C1A—C2A | 1.39 | C1B—C2B | 1.39 |
C1A—C6A | 1.39 | C1B—C6B | 1.39 |
C1A—C7A | 1.551 (5) | C1B—C7B | 1.545 (6) |
C2A—C3A | 1.39 | C2B—C3B | 1.39 |
C3A—C4A | 1.39 | C3B—C4B | 1.39 |
C4A—C5A | 1.39 | C4B—C5B | 1.39 |
C5A—C6A | 1.39 | C5B—C6B | 1.39 |
C7A—C7Ai | 1.512 (8) | C7B—C7Bi | 1.503 (8) |
N2A—N1A—C7A | 115.9 (9) | N2B—N1B—C7B | 112.9 (9) |
N1A—N2A—C8A | 113.0 (7) | N1B—N2B—C8B | 110.4 (7) |
C2A—C1A—C6A | 120 | C2B—C1B—C6B | 120 |
C2A—C1A—C7A | 122.2 (5) | C2B—C1B—C7B | 119.9 (6) |
C6A—C1A—C7A | 117.8 (5) | C6B—C1B—C7B | 120.0 (6) |
C1A—C2A—C3A | 120 | C1B—C2B—C3B | 120 |
C2A—C3A—C4A | 120 | C2B—C3B—C4B | 120 |
C5A—C4A—C3A | 120 | C5B—C4B—C3B | 120 |
C4A—C5A—C6A | 120 | C6B—C5B—C4B | 120 |
C5A—C6A—C1A | 120 | C5B—C6B—C1B | 120 |
N1A—C7A—C7Ai | 105.6 (9) | N1B—C7B—C7Bi | 111.5 (10) |
N1A—C7A—C1A | 107.5 (7) | N1B—C7B—C1B | 109.0 (8) |
C7Ai—C7A—C1A | 112.8 (11) | C7Bi—C7B—C1B | 111.2 (12) |
Symmetry code: (i) −x+2, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H18N4 |
Mr | 266.35 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 293 |
a, b, c (Å) | 5.525 (2), 17.444 (3), 8.194 (2) |
β (°) | 107.10 (2) |
V (Å3) | 754.8 (4) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.07 |
Crystal size (mm) | 0.40 × 0.20 × 0.10 |
Data collection | |
Diffractometer | Enraf-Nonius Turbo-CAD4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.970, 0.992 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1465, 1324, 687 |
Rint | 0.016 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.056, 0.170, 1.01 |
No. of reflections | 1324 |
No. of parameters | 107 |
No. of restraints | 24 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 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).
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).