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Nitro­gen-centered urazole radicals exist in equilibrium with tetra­zane dimers in solution. The equilibrium established typically favors the free-radical form. However, 1-aryl­urazole radicals bearing substituents at the ortho position favor the dimeric form. We were able to determine the structure of one of the dimers (substituted at both ortho positions with methyl groups), namely 1,2-(2,4-di­methyl­phen­yl)-2-[2-(2,4-di­methyl­phen­yl)-4-methyl-3,5-dioxo-1,2,4-triazoli­din-1-yl]-4-methyl-1,2,4-triazolidine-3,5-dione, C24H28N6O4, via X-ray crystallography. The experimentally determined structure agreed well with the computationally obtained geometry at the B3LYP/6-311G(d,p) level of theory. The preferred syn conformation of these 1-aryl­urazole dimers results in the two aromatic rings being proximate and nearly parallel, which leads to some inter­esting shielding effects of certain signals in the 1H NMR spectrum. Armed with this information, we were able to decipher the more complicated 1H NMR spectrum obtained from a dimer that was monosubstituted at the ortho position with a methyl group.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2053229617010786/fn3238sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S2053229617010786/fn3238Isup2.hkl
Contains datablock I

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S2053229617010786/fn3238sup3.pdf
Computing details, NMR spectra of relevant structures, and computational details

cml

Chemical Markup Language (CML) file https://doi.org/10.1107/S2053229617010786/fn3238Isup4.cml
Supplementary material

CCDC reference: 1563844

Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2017 (Sheldrick, 2015); molecular graphics: ShelXle (Hübschle et al., 2011); software used to prepare material for publication: ShelXle (Hübschle et al., 2011).

4-Methyl-1-[4-methyl-3,5-dioxo-2-(2,4,6-trimethylphenyl)-1,2,4-triazolidin-1-yl]-2-(2,4,6-trimethylphenyl)-1,2,4-triazolidine-3,5-dione top
Crystal data top
C24H28N6O4Dx = 1.280 Mg m3
Mr = 464.52Melting point: 433 K
Orthorhombic, PccnMo Kα radiation, λ = 0.71073 Å
a = 9.1077 (7) ÅCell parameters from 9977 reflections
b = 13.5893 (11) Åθ = 2.6–30.7°
c = 19.4760 (16) ŵ = 0.09 mm1
V = 2410.5 (3) Å3T = 100 K
Z = 4Block, colourless
F(000) = 9840.84 × 0.50 × 0.34 mm
Data collection top
Bruker APEXII CCD
diffractometer
3721 independent reflections
Radiation source: fine-focus sealed tube3323 reflections with I > 2σ(I)
Detector resolution: 8.3333 pixels mm-1Rint = 0.025
φ and ω scansθmax = 30.7°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Bruker, 2016)
h = 1013
Tmin = 0.661, Tmax = 0.746k = 1919
20363 measured reflectionsl = 2527
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045Hydrogen site location: difference Fourier map
wR(F2) = 0.126All H-atom parameters refined
S = 1.04 w = 1/[σ2(Fo2) + (0.0749P)2 + 0.8555P]
where P = (Fo2 + 2Fc2)/3
3721 reflections(Δ/σ)max = 0.015
223 parametersΔρmax = 0.47 e Å3
72 restraintsΔρmin = 0.22 e Å3
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
xyzUiso*/UeqOcc. (<1)
O10.14248 (8)0.15831 (5)0.25907 (4)0.01958 (16)
O20.56911 (8)0.04859 (5)0.35811 (4)0.02095 (16)
N10.26561 (8)0.20011 (5)0.35988 (4)0.01305 (16)
N20.35286 (8)0.07732 (5)0.29746 (4)0.01640 (16)
N30.41174 (8)0.17803 (5)0.38272 (4)0.01289 (15)
C10.24245 (10)0.14570 (6)0.29872 (4)0.01453 (17)
C20.36322 (13)0.00245 (8)0.24773 (6)0.0268 (2)
H2A0.2665 (17)0.0188 (14)0.2306 (11)0.018 (7)*0.59 (4)
H2B0.421 (3)0.0219 (16)0.2080 (9)0.052 (11)*0.59 (4)
H2C0.412 (3)0.0587 (12)0.2677 (10)0.027 (8)*0.59 (4)
H2F0.321 (4)0.0626 (13)0.2681 (12)0.037 (12)*0.41 (4)
H2D0.308 (3)0.0144 (18)0.2066 (10)0.021 (10)*0.41 (4)
H2E0.4647 (18)0.0156 (19)0.2365 (13)0.017 (10)*0.41 (4)
C30.45849 (10)0.09596 (6)0.34806 (5)0.01476 (17)
C40.45249 (9)0.20492 (6)0.45127 (4)0.01326 (16)
C50.54272 (11)0.28700 (7)0.45977 (5)0.01975 (19)
C60.59948 (14)0.34619 (9)0.40023 (6)0.0310 (3)
H6A0.5857 (19)0.3145 (12)0.3563 (7)0.052 (6)*
H6B0.7012 (14)0.3635 (11)0.4040 (8)0.040 (4)*
H6C0.546 (2)0.4099 (12)0.3951 (10)0.086 (8)*
C70.57694 (15)0.31505 (8)0.52693 (6)0.0300 (3)
H70.6382 (19)0.3702 (13)0.5328 (9)0.039 (4)*
C80.52312 (15)0.26429 (8)0.58352 (5)0.0284 (2)
C90.5563 (3)0.29835 (13)0.65532 (7)0.0595 (6)
H9A0.592 (2)0.2490 (16)0.6836 (9)0.089 (8)*
H9B0.618 (2)0.3521 (13)0.6560 (9)0.059 (6)*
H9C0.468 (2)0.3191 (18)0.6777 (11)0.132 (13)*
C100.43458 (12)0.18197 (7)0.57286 (5)0.0213 (2)
H100.3980 (18)0.1460 (12)0.6115 (8)0.032 (4)*
C110.39823 (10)0.15077 (6)0.50710 (5)0.01638 (18)
C120.30343 (13)0.06119 (8)0.49601 (6)0.0260 (2)
H12A0.2787 (17)0.0309 (11)0.5393 (7)0.045 (5)*
H12B0.3582 (18)0.0119 (11)0.4697 (8)0.056 (6)*
H12C0.2162 (16)0.0770 (12)0.4718 (8)0.052 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0168 (3)0.0192 (3)0.0228 (3)0.0009 (2)0.0055 (2)0.0024 (2)
O20.0162 (3)0.0188 (3)0.0279 (4)0.0057 (2)0.0029 (3)0.0039 (3)
N10.0119 (3)0.0094 (3)0.0178 (3)0.0016 (2)0.0024 (2)0.0012 (2)
N20.0143 (4)0.0139 (3)0.0210 (4)0.0019 (2)0.0021 (3)0.0053 (3)
N30.0113 (3)0.0124 (3)0.0150 (3)0.0021 (2)0.0019 (2)0.0013 (2)
C10.0140 (4)0.0116 (3)0.0180 (4)0.0008 (3)0.0000 (3)0.0014 (3)
C20.0242 (5)0.0231 (4)0.0330 (5)0.0041 (4)0.0034 (4)0.0161 (4)
C30.0135 (4)0.0123 (3)0.0185 (4)0.0002 (3)0.0001 (3)0.0010 (3)
C40.0135 (4)0.0122 (3)0.0141 (4)0.0008 (3)0.0002 (3)0.0001 (3)
C50.0254 (5)0.0179 (4)0.0159 (4)0.0095 (3)0.0001 (3)0.0012 (3)
C60.0377 (6)0.0347 (6)0.0207 (5)0.0232 (5)0.0017 (4)0.0076 (4)
C70.0483 (7)0.0235 (5)0.0181 (4)0.0183 (5)0.0036 (4)0.0012 (4)
C80.0450 (7)0.0245 (5)0.0158 (4)0.0085 (4)0.0000 (4)0.0021 (3)
C90.1150 (17)0.0468 (8)0.0168 (5)0.0332 (10)0.0024 (7)0.0059 (5)
C100.0254 (5)0.0222 (4)0.0163 (4)0.0016 (3)0.0023 (3)0.0043 (3)
C110.0153 (4)0.0153 (4)0.0185 (4)0.0014 (3)0.0002 (3)0.0045 (3)
C120.0252 (5)0.0237 (4)0.0292 (5)0.0120 (4)0.0081 (4)0.0124 (4)
Geometric parameters (Å, º) top
O1—C11.2062 (11)C4—C51.3953 (12)
O2—C31.2115 (11)C4—C111.4030 (12)
N1—N1i1.3854 (13)C5—C71.3975 (14)
N1—C11.4178 (11)C5—C61.5030 (14)
N1—N31.4349 (10)C7—C81.3896 (15)
N2—C11.3694 (11)C8—C101.3945 (14)
N2—C31.4003 (11)C8—C91.5035 (17)
N2—C21.4567 (12)C10—C111.3891 (13)
N3—C31.3714 (11)C11—C121.5080 (13)
N3—C41.4331 (11)
N1i—N1—C1118.68 (5)C5—C4—C11122.33 (8)
N1i—N1—N3113.27 (8)C5—C4—N3117.84 (8)
C1—N1—N3106.82 (6)C11—C4—N3119.81 (8)
C1—N2—C3111.66 (7)C4—C5—C7117.42 (9)
C1—N2—C2124.36 (8)C4—C5—C6122.60 (9)
C3—N2—C2123.92 (8)C7—C5—C6119.96 (9)
C3—N3—C4125.83 (7)C8—C7—C5121.89 (9)
C3—N3—N1107.79 (7)C7—C8—C10118.95 (9)
C4—N3—N1118.40 (7)C7—C8—C9120.93 (11)
O1—C1—N2129.74 (8)C10—C8—C9120.10 (10)
O1—C1—N1125.18 (8)C11—C10—C8121.33 (9)
N2—C1—N1105.05 (7)C10—C11—C4118.07 (8)
O2—C3—N3127.65 (8)C10—C11—C12121.00 (8)
O2—C3—N2126.08 (8)C4—C11—C12120.93 (8)
N3—C3—N2106.27 (7)
N1i—N1—N3—C3147.65 (6)C3—N3—C4—C5110.61 (10)
C1—N1—N3—C315.15 (9)N1—N3—C4—C5104.43 (10)
N1i—N1—N3—C461.61 (8)C3—N3—C4—C1171.19 (12)
C1—N1—N3—C4165.89 (7)N1—N3—C4—C1173.77 (10)
C3—N2—C1—O1171.90 (9)C11—C4—C5—C70.72 (15)
C2—N2—C1—O15.46 (16)N3—C4—C5—C7177.43 (9)
C3—N2—C1—N110.06 (10)C11—C4—C5—C6179.11 (10)
C2—N2—C1—N1172.58 (9)N3—C4—C5—C60.96 (15)
N1i—N1—C1—O137.29 (14)C4—C5—C7—C80.46 (18)
N3—N1—C1—O1166.76 (8)C6—C5—C7—C8177.98 (13)
N1i—N1—C1—N2144.56 (9)C5—C7—C8—C101.2 (2)
N3—N1—C1—N215.09 (9)C5—C7—C8—C9177.41 (15)
C4—N3—C3—O223.65 (15)C7—C8—C10—C110.72 (18)
N1—N3—C3—O2171.62 (9)C9—C8—C10—C11177.87 (14)
C4—N3—C3—N2156.86 (8)C8—C10—C11—C40.40 (15)
N1—N3—C3—N28.89 (9)C8—C10—C11—C12179.50 (10)
C1—N2—C3—O2178.74 (9)C5—C4—C11—C101.14 (14)
C2—N2—C3—O21.37 (15)N3—C4—C11—C10176.98 (8)
C1—N2—C3—N30.76 (10)C5—C4—C11—C12178.75 (9)
C2—N2—C3—N3178.13 (9)N3—C4—C11—C123.13 (13)
Symmetry code: (i) x+1/2, y+1/2, z.
Selected crystallographic and computational structural data for dimer 2a-2a top
ExperimentalComputational
Bond distances (Å)
C4—N31.433 (1)1.432
N1—N31.435 (1)1.435
N1—N1i1.385 (1)1.396
N3—C31.371 (1)1.379
C3—O21.211 (1)1.207
N1—C11.418 (1)1.432
C1—O11.206 (1)1.206
Bond angles (°)
C4—N3—N1118.40 (7)121.6
C3—N3—N1107.79 (7)109.0
N3—N1—N1i113.27 (8)114.2
Torsion angles (°)
C11—C4—N3—N173.8 (1)65.0
N1—N3—C3—N28.89 (9)5.7
N3—N1—N1i—N3i140.6143.6
Note: (a) atoms N1A and N3A are the C2-symmetry-related atoms on the remaining half of the dimer.
Comparison of theoretical and experimental 1H NMR chemical shifts for dimers 2a-2a and 2b-2b top
DimerSignal assignmentComputed chemical shift (ppm)Experimental chemical shift (ppm)bDifference (ppm)
2a-2aN—CH33.053.24–0.19
aryl H7.016.830.18
aryl H (shielded)6.626.380.24
aryl CH32.382.250.13
aryl CH32.432.260.17
aryl CH3 (shielded)1.371.49-0.12
2b-2bN-CH33.083.10-0.02
aryl H5.926.07–0.15
aryl H (shielded)5.695.94-0.25
aryl OCH33.733.79-0.06
aryl OCH33.713.77-0.06
aryl OCH3 (shielded)3.363.63-0.27
Note: (a) computed at the mPW1PW91/6-311+G(2d,p)//B3LYP/6-311G(d,p) level of theory using implicit solvent model (smd) in chloroform and scaled according to Tantillo (Lodewyk et al., 2012); (b) in CDCl3. Symmetry code: (i) -x+1/2, -y+1/2, z.
 

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