Haaf et al.
1531
(
72%) of product 6 was collected (49°C, 0.1 torr (1 torr =
33.322 Pa)) The product was stored over NaOH to keep it
dried and charged with argon. Freshly cut potassium (1.0 g,
25.5 mmol) and sodium (0.33 g, 14.3 mmol) were added to
the three-necked flask under a heavy flow of argon. The ap-
paratus was then evacuated, and the flask heated with a heat
gun to melt the potassium and sodium chunks to generate
1
1
13
dry. H NMR δ: 1.014 (s,18H), 2.541 (s, 4H). C NMR δ:
9.5, 43.6, 49.8.
2
NaK . The apparatus was again charged with argon, and
Synthesis of N,N′-di-tert-butyl-1,3-diaza-2,2-dichloro-2-
silacyclopentane (7)
Into a three-necked 2 L flask equipped with a condenser,
gas inlet, stopper, stir bar, and septum was added N,N ′-di-
tert-butylethylenediamine 6 (20.0 g, 116 mmol) and hexane
2
cooled to room temperature at which point 30 mL freshly
distilled THF was added to the flask. The apparatus was
then cooled in a dry ice – acetone bath. The solution of 7 in
THF was added to the flask via cannula, and the apparatus
was warmed to room temperature. Upon warming the solu-
(
(
250 mL). The solution was stirred at 0°C while SiCl4
20.0 g, 118 mmol) was added via syringe. The solution was
1
tion turned black. Regular monitoring by H NMR indicated
a gradual formation and then disappearance of silylene over
a 3 h period. Eventually no silylene peaks were observed in
the NMR. At this point the solution was filtered. The filtrate
was cooled in a dry ice – acetone bath and reacted with 1
equiv of a proton source (water, EtOH, phenol) to produce
the dihydride in 95% yield (by NMR). Crystals suitable for
X-ray analysis were grown from THF. HRMS : m/z 398
+
[
M ]. Exact mass calcd. for C H N Si m/z: 398.3261;
20 46
4
2
1
found: 398.3210. H NMR δ: 1.293 (s, 36H), 2.965 (s, 8H),
.739 (s, 2H). C NMR δ: 29.71, 44.78, 50.73. Si NMR δ:
1
3
29
5
–23.9.
Synthesis of tetramer (10)
Disilene 10 was produced by recrystallization of 1 from
THF or diethyl ether. Alternatively, crystals of 1 will slowly
convert in the solid state to disilene 10. H NMR δ: 1.368
Synthesis of N,N ′-di-tert-butyl-1,3-diaza-2-sila-2-ylidene
1)
A solution of N,N ′-di-tert-butyl-1,3-diaza-2,2-dichloro-2-
silacyclopentane, 7, (10 g, 37.1 mmol) in THF (100 mL)
was made up in a flame-dried, degassed Schlenk flask. A
three-necked, 250 mL flask was equipped with a stir bar,
frit, septum, and stopper. On the other end of the frit was
placed a 250 mL Schlenk flask equipped with a stir bar and
attached to the Schlenk line. The apparatus was rigorously
flame-dried and charged with argon. Freshly cut potassium
(
1
(
2
4
s, 18H), 1.416 (s, 18H), 1.429 (s, 18H), 1.575 (s, 18H),
1
3
.9–3.1 (m, 16H). C NMR δ: 30.16, 30.22, 31.0, 31.20,
2
9
2.50, 42.56, 45.41, 51.36, 51.55, 51.67, 55.59, 55.67. Si
NMR δ: 119.0, –25.0.
Reaction of 1 with ethanol
A dried, degassed Schlenk flask was charged with
–
3
(
2.0 g) and sodium (0.6 g) were added to the three-necked
0.222 mL of ethanol (3.8 × 10 mol) and 10 mL THF, then
flask under a heavy flow of argon. The apparatus was then
evacuated, and the flask heated with a heat gun to melt the
placed in a dry ice – acetone bath. A solution of 1 (0.075 g
–
3
(3.8 × 10 mol)/50 mL THF) was added and the flask was
allowed to warm to room temperature. The ethanol insertion
product 11 is a liquid, which can be isolated by fractional
potassium and sodium chunks to generate NaK . The appa-
2
ratus was again charged with argon, and cooled to room
temperature at which point 50 mL freshly distilled THF and
1
distillation (38°C, 0.1 torr (1 torr = 133.322 Pa)) (60%). H
2
0 mL freshly distilled TEA were added to the flask. The
NMR δ: 1.207 (s, 18H), 1.207 (t, 3H, J = 6.9 Hz), 2.88–2.94
1
3
apparatus was then cooled in a dry ice – acetone bath. The
solution of 7 in THF was added to the flask, and the appara-
tus was warmed to room temperature. The reaction was
(m, 4H), 3.736(q, 2H, J = 6.9 Hz), 5.090 (s, 1H). C NMR
2
9
δ: 18.41, 29.58, 43.05, 50.50, 56.92. Si NMR δ: –44.5.
1
monitored by H NMR and filtered when complete (approxi-
Reaction of 1 with phenol
mately 2–3 h). It is important to filter immediately upon
completion for maximal yield. The filtrate was concentrated
to give 6 g (80%) of crude product and recrystallized from
A dried, degassed Schlenk flask was charged with 0.475 g
–
3
of phenol (5.0 × 10 mol) and 30 mL THF, then placed in a
–
3
dry ice – acetone bath. A solution of 1 (1.0 g (5.05 × 10
1
THF to give crystals of disilene 10 (5.0 g, 68%). H NMR
mol)/50 mL THF) was added and the flask was allowed to
warm to room temperature. The insertion product 12 was
formed in 80% yield by NMR. Recrystallization from THF
1
3
(
4
for 1) δ: 1.269 (s, 18H), 3.140 (s, 4H). C NMR δ: 31.68,
6.46, 52.46. Si NMR δ: 118.9.
2
9
1
provided crystals of 12 suitable for X-ray analysis. H NMR
δ: 1.130 (s, 18H), 2.9–3.0 (m, 4H), 5.354 (s, 1H), 6.7–7.2
Synthesis of dihydride (9)
1
3
(
1
m, 5H). C NMR δ: 29.38, 42.81, 50.69, 116.5,121.6,
23.3, 129.9. Si NMR δ: –46.6.
A solution of N,N′-di-tert-butyl-1,3-diaza-2,2-dichloro-2-
silacyclopentane, 7, (1.0 g, 3.7 mmol) in THF (20 mL) was
made up in a flame-dried, degassed Schlenk flask. A three-
necked, 250 mL flask was equipped with a stir bar, frit, sep-
tum, and stopper. On the other end of the frit was placed a
2
9
Reaction of 1 with water
A dried, degassed Schlenk flask was charged with
–
3
2
50 mL Schlenk flask equipped with a stir bar and attached
0.034 mL of water (1.9 × 10 mol) and 10 mL THF, then
to the Schlenk line. The apparatus was rigorously flame-
placed in a dry ice – acetone bath. A solution of 1 (0.075 g
©
2000 NRC Canada