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[1]. In comparison to the solid state structure of 1 [6]
the Si–Si bond lengths are only slightly elongated
(average: 238.4 vs. 236.1 pm). The lengths of the six
dative B···N vary between 161.9 and 163.9 pm. This
is above the value of 158.7 pm which was reported
as average B···N bond lengths in acyclic amine–
borane complexes [16], but is still smaller than the
dative bond length of 166.1 pm in the BH3 · urotropine
complex [17].
Ongoing experiments are addressing the question
whether complexation of the nucleophilic dimethy-
lamino groups in 1, as realized in cyclotrisilane 15,
surpresses the silylene activity, which is typical for
cyclotrisilanes 1–3.
3.3. Bis[2-(dimethylaminomethyl)phenyl](dimethylalu-
minum)methylsilane · AlMe3 (10)
A 2 M solution of AlMe3 in toluene (1.69 ml, 3.39
mmol) was added to a solution of 1 (503 mg, 0.57
mmol) in toluene (7 ml) and stirred for 15 h at r.t. The
solvent was removed in vacuo and pentane (7 ml) was
added. The resulting suspension was stirred for further
15 h and filtered. The remaining solid was washed with
pentane to yield 10 as white solid (470 mg, 63%).
Crystals suitable for X-ray diffraction analysis were
obtained by crystallization from toluene/pentane.—
Dec.: 87°C.—1H-NMR (C6D6): l= −0.63 (s; 3H,
AlMe), −0.56 (s; 3H, AlMe), −0.36 (s; 9H, AlMe3),
0.79 (s; 3H, SiMe), 1.55 (s; 3H, NMe), 1.71 (s; 3H,
NMe), 2.02 (s; 3H, NMe), 2.23 (s; 3H, NMe), 2.67, 3.66
2
(AB system, J=13 Hz; 2H, CH2N), 4.20, 4.33 (AB
3. Experimental
2
3
system, J=13 Hz; 2H, CH2N), 6.68 (d, J=7 Hz; 2H,
3
ar H), 6.9–7.2 (m; 6H, ar H), 7.54 (d, J=7 Hz; 2H, ar
3.1. General
H).—13C-NMR (C6D6): l= −9.9 (AlMe), −9.1
(AlMe), −8.75 (AlMe3), 0.8 (SiMe), 42.2 (NMe2), 43.4
(NMe2), 45.0 (NMe2), 47.9 (NMe2), 60.6 (CH2N), 66.2
(CH2N), 127.1 (ar C), 127.6 (ar C), 128.4 (ar C), 129.1
(ar C), 131.5 (ar C), 132.6 (ar C), 136.6 (ar C), 136.7 (ar
Cq), 137.3 (ar C), 139.6 (ar Cq), 145.4 (ar Cq), 146.6 (ar
Cq).—29Si-NMR (C6D6): l= −31.4.
1H- and 13C-NMR spectra were recorded on a
Bruker AM 250 (1H-NMR: 250 MHz; 13C-NMR: 62.9
MHz) or a Bruker AMX 300 (1H-NMR: 300 MHz;
13C-NMR: 75.5 MHz) spectrometer. Cq, CH, CH2 and
CH3 were determined using the DEPT or APT pulse
sequence. 29Si-NMR spectra were recorded on a
Bruker AMX 300 (59.6 MHz) using a refocused INEPT
pulse sequence or direct acquisition. Chemical shifts
refer to lTMS=0.0. All manipulations were carried out
under inert argon atmosphere using carefully dried
glassware. Halogen-free solvents used were dried by
refluxing over sodium/benzophenone ketyl and distilled
immediately before use. CDCl3 was distilled from
CaH2.
3.4. Hydrolysis of 10
To a solution of 10 in C6D6 in an NMR tube was
added a drop of water. After ceasing of the gas evolu-
tion the 1H-NMR spectrum of the slurry showed
mainly the signals of bis[2-(dimethylaminomethyl)-
phenyl]methylsilane (11) [10].
3.5. Bis[2-(dimethylaminomethyl)phenyl](dimethylalu-
minum)methylsilane (12)
3.2. Bis[2-(dimethylaminomethyl)phenyl]siliconium
bromide (8a)
(a) A crystal of quinuclidine was added to a solution
of 10 (20 mg, 45 mmol) in C6D6 (0.4 ml) in an NMR
tube. After dissolution of the amine the signals of 12
were observed besides that of left over quinuclidine and
the quinuclidine AlMe3 · complex. (b) To a solution of
10 (120 mg, 0.27 mmol) in C6D6 (0.6 ml) in an NMR
tube was added 1 (80 mg, 0.09 mmol). A 1H-NMR
spectrum taken after 15 h at r.t. showed exclusively the
signals of 12. (c) A 2 M solution of AlMe3 in toluene
(84 ml, 0.17 mmol) was added to a solution of 1 (50 mg,
0.06 mmol) in toluene (0.5 ml) and stirred for 3 h at r.t.
The solvent was removed in vacuo and the remaining
A solution of 1 (202 mg, 0.23 mmol) and pyridinium
bromide (109 mg, 0.68 mmol) in THF (50 ml) was
stirred for 4 days at r.t. The solvent was removed in
vacuo and the residue was washed with hexane (2×10
ml) leaving behind 8a (132 mg, 51%) as a white solid.
The solvent was removed from the hexane phase in
vacuo and the remaining oil was distilled at 160°C/10–3
Torr to yield 9 (95 mg, 47%). 8a: m.p.: 212°C.—1H-
NMR (CDCl3): l=2.72 (s; 6H, NMe), 2.93 (s; 6H,
NMe), 4.41, 4.42 (AB-system, 2JHH=15 Hz; 4H,
1
CH2N), 4.66 (s (d, JSiH=273 Hz); 1H, SiH), 7.3–7.5
3
1
(m; 6H, ar H), 7.79 (d, JHH=7 Hz; 2H, ar H).—13C-
yellow oil was dissolved in 0.4 ml C6D6. The H-NMR
NMR (CDCl3): l=45.3 (NMe), 47.5 (NMe), 64.7
(CH2N), 127.2 (ar CH), 128.0 (ar Cq), 128.3 (ar CH),
132.0 (ar CH), 135.4 (ar CH), 144.4 (ar Cq).—29Si-
NMR (CDCl3): l= −51.5 (1JSiH=269 Hz).—IR (nu-
spectrum showed, besides traces of 1, only signals of
12.—1H-NMR (C6D6): l= −0.58 (s; 3H, AlMe),
−0.52 (s; 3H, AlMe), 0.73 (s; 3H, SiMe), 1.97 (s; 12H,
NMe2), 3.33, 3.81 (AB system, J=13 Hz; 4H, CH2N),
7.01–7.15 (m; 6H, ar H), 7.49–7.51 (m; 2H, ar H).
2
jol): w=2164 cm−1
.