Chapyshev et al.
JOCArticle
argon (DS = -0.0938 cm-1, ES = -0.0040 cm-1) and 2MT-
HF glass (DS=-0.0934 cm-1, ES=-0.0015 cm-1). In ar-
gon matrices the powder X-band EPR spectra show three
strong Z-transitions in the 40-300 mT region and six
couples of well-resolved X- and Y-transitions, whereas in
2MTHF glasses six unresolved X,Y-transitions in the 150-
700 mT region are observed. The fine-structure parameters
measured in argon matrices fit well the geometry parameters
and spin densities at the nitrene units predicted by DFT
calculations for the septet trinitrene 6. The very small para-
meter ES found for 6 in 2MTHF glass indicates significant
changes in the spin densities at its nitrene units. Presumably,
this is caused by specific interactions of these units with
surrounding 2MTHF molecules. Compared to the very
strong interactions of singlet nitrenes with THF resulting
in the formation of ylides,18 the paramagnetic nitrene units of
6 interact only weakly with the 2MTHF molecules, resulting
in some redistribution of spin density without formation of
new chemical bonds. The analysis of the magnetic parameters
of septet trinitrene 6 shows that the energy of dipole-
dipole interactions between three nitrene units attached to
the 1,3,5-benzenetriyl core is about 0.009 cm-1 or 10% of the
DS value.
Experimental Section
Synthesis. 2,4,6-Triaminotoluene trihydrochloride was syn-
thesized by the reduction of 2,4,6-trinitrotoluene according to
the literature procedure.28
FIGURE 5. Contour plots of the functional R for EPR spectra
recorded in solid argon (A, red: Rmin = 0.67 mT, R1 = 0.75 mT,
R2 = 0.9 mT, R3 = 1.6 mT, R4 = 2 mT, R5 = 2.2 mT) and in
2MTHF glass (B, blue: Rmin = 1.28mT, R1 = 1.35mT, R2 = 1.5 mT,
R3 = 1.7 mT, R4 = 2 mT, R5 = 2.6 mT).
2,4,6-Triazidotoluene (1). 2,4,6-Triaminotoluene trihydro-
chloride (2.77 g, 10 mmol) was dissolved in 150 mL of 20%
HCl and cooled to 0 °C. Sodium nitrite (3.1 g, 35 mmol),
dissolved in 20 mL of H2O, was added within 15 min, while
the temperature of the solution was kept below 5 °C. Foaming
was controlled by the addition of a few drops of diethyl ether.
After 20 min of stirring at 0 °C, a solution of 2.93 g (35 mmol)
of sodium azide was added slowly and the solution was
stirred subsequently for an additional 30 min. After warming
to room temperature, it was poured onto 250 g of ice and
extracted twice with 200 mL of diethyl ether. The organic
phase was extracted twice with 200 mL of a diluted NaHCO3
solution and the procedure was repeated with saturated NaH-
CO3 solution. The organic phase was dried over Na2SO4 and
the solvent was removed in vacuum. The solid residue was
recrystallized from a hexane-benzene mixture to yield 900 mg
(4.2 mmol, 42%) of 2,4,6-triazidotoluene as a bright yellow
solid. Mp 103-104 °C dec; 1H NMR (200 MHz, CDCl3) δ 1.93
(c, 3H), 6.48 (c, 2H); 13C NMR (CDCl3) δ 10.0 (CH3), 103.8 (C-
3,5), 117.2 (C-1), 138.4 (C-4), 140.3 (C-2,6); IR (microcrystalline
film) ν/cm-1 (%) 2961 (15), 2924 (13), 2854 (8), 2108 (100), 1580
(25), 1571 (42), 1560 (37), 1490 (30), 1419 (30), 1339 (15), 1266
(88), 1102 (38), 1019 (40), 961 (25), 815 (55), 702 (25), 590 (13),
532 (33); UV-vis (MeOH) λmax, nm (log ε) 318 (3.24), 308
(3.32), 245 (4.30), 212 (3.87); MS (m/z, %) 215 (13), 187 (10), 104
(8), 77 (15), 66 (73), 63 (22), 52 (100), 51 (33), 39 (68). Anal. Calcd
for C7H5N9 (215.17): C 39.07, H 2.34, N 58.59. Found: C 39.32,
H 2.44, N 58.24.
The fine-structure parameters of trinitrene 6 provide im-
portant information regarding dipole-dipole interactions
between the three nitrene units attached to the 1,3,5-benze-
netriyl core. The energy of these interactions Eij can be
estimated from eq 7:
Eij ¼ DSðexperimentÞ þ ðDtþλ=3Þ=10
ð7Þ
For triplet nitrenes 2 and 3 DT is 1.02 cm-1, and the spin
densities at the nitrene units are F ≈ 1.56. In septet trinitrene
6 the nitrene units in positions 2 and 6 show F ≈ 1.57, which
corresponds to Dt = 1.02 ꢁ (1.57/1.56) cm-1 = 1.0265 cm-1
.
With λ = 0.0127 and Dt = 1.0265 cm-1 we obtain for 6 from
eq 7 Eij = 0.009 cm-1, which is about 10% of its DS value.
Previous studies have shown that Eij of septet trinitrene 7
reaches about 18% of its DS value.6 This shows that the
dipole-dipole interactions between the nitrene units at the
1,3,5-benzenetriyl core are weaker than those at the 2,4,6-
triazinetriyl core. This is explained by a more efficient
delocalization of the py unpaired electrons from the nitrene
units in the benzene ring. On the other hand, due to this
delocalization septet trinitrenobenzenes are rather stable in
2MTHF glasses and available for spectroscopic studies.
EPR Measurements and Analysis. X-band EPR spectra were
recorded with a Bruker-Elexsys E500 EPR spectrometer with an
ER077R magnet (75 mm gap between pole faces), an ER047
XG-T microwave bridge, and an ER4102ST resonator with a
TE102 cavity. The experimental technique for matrix isolation
used in this study was similar to that described earlier.7
Conclusions
Septet 2,4,6-trinitrenotoluene 6 is the major paramagnetic
product with a septet spin state formed during the photolysis
of 2,4,6-triazidotoluene 1 in cryogenic matrices. This trini-
trene displays remarkably different EPR spectra in solid
(28) Shevelev, S. A.; Shakhnes, A. K.; Ugrak, B. I.; Vorob’ev, S. S. Synth.
Commun. 2001, 31, 2557–2561.
J. Org. Chem. Vol. 74, No. 19, 2009 7243