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M. Ri6ie`re-Baudet et al. / Journal of Organometallic Chemistry 595 (2000) 153–157
3.5. Photochemical stability of 1
3.1. Preparation of 1
A similar sample of 1 dissolved in 0.3 ml of THF
and 0.3 ml of toluene was placed in a quartz tube at
−60°C in the ESR cavity. The sample was irradiated
and warmed progressively. The expected septet was
not observed, indicating that 1 is stable under these
conditions.
To H2NCN (0.07 g, 1.72 mmol) in 4 ml of THF at
−70°C was added dropwise with stirring a solution of
t-BuLi in pentane (3.44 mmol, 2.02 ml, 1.7 M). After
30 min at r.t. the mixture was cooled again to −60°C
and Mes3GeCl (0.80 g, 1.72 mmol) in 6 ml of THF
was added dropwise with stirring. After 1 h at
−60°C, GeCl2.dioxane (0.19 g, 0.86 mmol) in 2 ml of
THF was added dropwise with stirring. The mixture
was kept at −30°C for 16 h. THF was then replaced
by benzene and lithium chloride centrifuged. Evapora-
tion of the solvents under vacuum afforded 0.33 g of a
white powder of 1 (yield 72%) which was unstable in
air.
3.6. Hydrolysis of 1 to yield 3
At r.t. 0.3 g of 1 in 4 ml of benzene left in an open
flask afforded colorless crystals, which slowly de-
posited on the vessel walls near the liquid surface. 0.21
g of these crystals were obtained and identified as 3b
(yield 75%) by X-ray analysis. M.p.: 127–129°C. IR
1
M.p.: 108°C with decomposition. H-NMR (CDCl3):
(KBr): (was NCN): 2122 cm−1
. Anal. Calc. for
lppm, 2.20 (s, 54H, CH3); 6.72 (s, 12H, C6H2). 13C-
NMR (CDCl3): lppm, 21.04 (p-CH3); 23.97 (o-CH3);
143.64 (C2); 128.92 (C3); 138.60 (C4); 136.00; 135.68
(C1; NCN); (C6D6) lppm, 21.02 (p-CH3); 24.21 (o-
CH3); 143.84 (C2); 130.17(C3); 139.50(C4). IR (CDCl3):
(was NCN): 2088 cm−1. MS (DCI–CH4), m/z, %):
1013, 2% [M+1].
C28H34GeN2, C, 71.37; H, 7.27; N, 5.95. Found: C,
71.45; H, 6.99; N, 5.54%.
3.7. Tautomeric equilibrium 3a/3b as followed by IR
and 13C-NMR studies
A reference solution of 3 was prepared by dissolving
3 (0.02 g, 0.04 mmol) in 1.5 ml of chloroform. To 0.5
ml of this solution was added 0.1 ml of nitromethane.
The reference solution and the solution with ni-
tromethane were analyzed by IR spectroscopy. The
presence of nitromethane increased the intensity of the
wCꢁN absorption. IR (CDCl3): (was CN): 2198 cm−1; (w
3.2. Reaction of 3,5-di-t-butylcatechol with 1, followed
by reaction with 3,5-di-t-butylorthoquinone
To 1 (0.34 g, 0.34 mmol) in 3 ml of THF was added
dropwise with stirring at r.t. a solution of 3,5-di-t-
butylcatechol (0.08 g, 0.34 mmol) in 2 ml of THF.
After 4 h at r.t., THF was evaporated under vacuum
yielding a white sticky residue consisting of 3 (69%)
1
N–H): 3388 cm−1; (was NCN): 2149 cm−1. H-NMR
(CDCl3, 80 MHz): lppm, 2.21 (s, 18H, o-CH3); 2.25 (s,
9H, p-CH3); 6.82 (s, 6H, C6H2).
and
2-germylene(6,8-di-t-butyl)-4,5-benzo-1,3-dioxo-
For 13C-NMR analysis, the reference solution was
prepared in 1.5 ml of CDCl3. To 1.5 ml of this solu-
tion was added 0.05 ml of CH3NO2. In the 13C-NMR
spectrum, there were two sets of carbon signals, one of
which was enhanced by the presence of CH3NO2 and
attributed to the cyanamide form 3a: lppm, 21.09
(p-CH3); 23.87 (o-CH3); 134.29 (C1); 143.18 (C2);
129.96(C3); 139.88 (C4); 122.55 (CꢁN). The other car-
lane 2 (31%) characterized by comparison with an
authentic sample [7]. Addition of an equivalent of
3,5-di-t-butylorthoquinone gave the expected spiroger-
1
mane [7] identified by H-NMR.
3.3. Attempts at addition reactions to 1
To 1 (0.33 g, 0.32 mmol) in 3 ml of THF was added
with stirring at r.t. dimethylbutadiene (0.03 g, 0.32
mmol). After 5 h of reaction at r.t. only thermal
decomposition products of 1 were recovered. The same
result was observed with methyl iodide.
bons signals were attributed to carbodiimide 3b: lppm
,
21.09 (p-CH3); 24.08 (o-CH3); 134.29 (C1); 143.29 (C2);
129.67 (C3); 139.35 (C4); 135.21 (NꢀCꢀN). MS (EI,
+
m/z, %): 472, 5% [M+ ]; 457, 6% [M –NH]; 431,
100% [M+–NH–CN]; 352, 45% [M+–MesH].
3.4. Thermal decomposition of 1
3.8. X-ray analysis of 3b
A solution of 1 (0.05 g, 0.05 mmol) in 0.5 ml of
Crystal data for 3b: C31H36GeN2, M=509.21, tri-
CDCl3 was heated to 50°C for 1 h. The decomposition
(
,
,
clinic, P1, a=8.957(1) A, b=16.303(2) A, c=
1
was followed by H-NMR, showing the formation of
,
18.505(2) A, h=80.07(1)°, i=83.89(1)°, k=89.39(1)°,
V=2646.5(5) A , Z=4, zc 1.278 Mg m−3, F(000)=
3
4. A white precipitate not soluble in usual organic
solvents was identified (by its infrared spectrum:
wNꢀCꢀN: 2105 cm−1) as (GeNCN)n 5 [9], but it was too
sensitive to hydrolysis for microanalysis.
,
,
1072, u=0.71073 A, T=173(2) K, v(Mo–Ka)=1.179
mm−1, crystal size 0.6×0.5×0.1 mm, 2.29°B[B
22.72°, 18 536 reflections (6758 independent, Rint
=