Reactions of a stable silylene with halocarbons

Article abstract of DOI:10.1039/b507462b

An unusual product formation is observed for the insertion reaction of the thermally stable silylene Si[(NCH₂Bu^t)₂C ₆H₄-1,2] [abbrev. as Si(NN)] into the carbon-halogen bond of alkyl or aryl halides R

Full text of DOI:10.1039/b507462b

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F U L L P A P E R
Reactions of a stable silylene with halocarbons
Mahmood Delawar, Barbara Gehrhus* and Peter B. Hitchcock
Department of Chemistry, School of Life Sciences, University of Sussex, Brighton,
UK BN1 9QJ. E-mail: b.gehrhus@sussex.ac.uk
Received 26th May 2005, Accepted 5th July 2005
First published as an Advance Article on the web 19th July 2005
An unusual product formation is observed for the insertion reaction of the thermally stable silylene
Si[(NCH2But)2C6H4-1,2] [abbrev. as Si(NN)] into the carbon–halogen bond of alkyl or aryl halides RHal (Hal = Cl,
Br). In general, depending on the halogen, the reaction either results in a disilane of type (NN)Si(Hal)-(R)Si(NN) for
Hal = Cl or a mixture of disilane and the monosilane (NN)Si(R)(Hal) for Hal = Br. The results are put into context
to previously suggested mechanisms. The disilane (NN)Si(Hal)-(R)Si(NN) (Hal = Cl or Br) is thermally labile and
mild thermolysis yields the corresponding monosilane (NN)Si(R)(Hal) and silylene 1. Additionally, strong evidence
is presented for a radical pathway for the reaction of 1 and RHal.
Introduction
Silylenes show a variety of reactions which can be categorised
generally into insertions and additions; additionally, silylenes
can act as ligands in transition metal complexes.1–4 Stable
silylenes were shown to extend the scope of insertion reactions
of transient silylenes, including insertions into M–N (M =
Li, Na, K),5,6 Li–C,7 Li–Si,5 B–C,8 M(II)–N (M = Si, Ge,
Sn, Pb),9–11 Sn(II)–C,12 Sn(II)–Cl,13 O–H14,15 and Si–Cl bonds.16
The silylene Si[(NCH2But)2C6H4-1,2] 1 [abbrev. Si(NN)] also
inserted into the M–Cl bond of [MCl2(PPh3)2], concomitant with
PPh3 ligand replacement, leading to [M{Si(NN)}2{Si(NN)Cl}2]
(M = Pd, Pt).17
Insertion of a stable bis(amino)silylene into the C–Hal bond
of a halocarbon was first reported by us in 1996 in the context of
the reaction of 1 with MeI.14 Later this was extended to reactions
with CH2Cl2, CH2Br2 and CHCl3 (Scheme 1); preliminary results
were included in our review article in 2001,3 [the product of the
reaction of 1 with CHCl3 was erroneously identified therein as
CHCl{Si(NN)Cl}2].
Scheme 2
Scheme 1
Scheme 3
Reactions of the bis(amino)silylene Si[N(But)CHCHNBut]
[abbrev. as Si(NꢀNꢀ)] with halocarbons were reported by West,
et al., Scheme 2.15,18 The unusual formation of the disilanes
Cl(NꢀNꢀ)Si-Si(NꢀNꢀ)CR3 led us to reinvestigate the reactions of 1
with CH2Cl2, CH2Br2 and CHCl3 and we found (vide infra) that
similar disilanes are indeed formed. These products, however,
are thermally labile and subject to rearrangement.
Somewhat different is the reaction behaviour of the marginally
stable bis(alkyl)silylene Si[C(SiMe3)2CH2CH2C(SiMe3)2] [ab-
brev. as Si(RK)2], particularly in its reactions with CHCl3, CCl4,
CH2Cl2 or (chloromethyl)cyclopropane (Scheme 3), as reported
by Kira et al.19
the synthesis of alkylhalosilanes by direct reaction of silicon and
a haloalkane.19
In this paper we report full details of the results of Scheme 1
and extend the topic of further reactions of 1 with related
halocarbons.
Results and discussion
The reaction of 1 with PrCl, CH2Cl2, Me2CCl2 or CHCl3
proceeded under mild conditions and exclusively yielded a
product of the formal double insertion of 1 into the C–Cl bond,
irrespective of the relative molar ratio of the reactants. The
resulting compounds 2a, 3a, 4a, and 5, respectively, in Scheme 4,
were not thermally stable. Compound 2a was converted upon
The ready insertion of a stable silylene into a carbon–
halogen bond of an organic halide presents an alternative to
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3
2 9 4 5
©

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Scheme 4
heating and silylene extrusion into the monosilyl derivative 2b.
A similar reaction occurred when compound 3a was heated,
however, with a different outcome. The corresponding monosilyl
(NN)Si(Cl)(CH2Cl) was not observed, but was most likely
subjected to further reaction with the extruded silylene 1,
which inserted into the C–Cl bond of the (NN)Si(Cl)(CH2Cl)
intermediate to furnish the C2-symmetric isomer 3b. Likewise,
compound 5 was thermally labile; but heating 5 led to a complex
mixture of insertion products.
Thermolysis of compound 4a did not proceed via silylene
extrusion, but instead, via an intramolecular rearrangement, the
isomer 4b was obtained. Prolonged heating at 140 ◦C for 10 days
led to the complete conversion to the C2-symmetric isomer 4c.
The structures of compounds 2a, 3a and 4b were also con-
firmed by X-ray structural analysis, Fig. 1, 2, and 3, respectively.
Crystal refinement data are given in Table 1. Note that the
structure of 3a has disorder of the Cl and CH2Cl groups.
Fig. 2 Molecular structure of compound 3a. Selected bond lengths
◦
˚
(A) and angles ( ): Si(1)–N(1) 1.720(5), Si(1)–N(2) 1.727(5), Si(1)–Si(2)
2.362(2), Si(2)–N(3) 1.727(4), Si(2)–N(4) 1.728(5); N(1)–Si(1)–N(2)
93.9(2), N(3)–Si(2)–N(4) 94.3(2).
Fig. 1 Molecular◦structure of compound 2a. Selected bond lengths
˚
(A) and angles ( ): Si(1)–N(2) 1.7408(15), Si(1)–N(1) 1.7484(16),
Si(1)–Si(2) 2.3652(7), Si(2)–N(4) 1.7252(16), Si(2)–N(3) 1.7256(15),
Si(2)–Cl 2.0866(7); N(2)–Si(1)–N(1) 93.82(7), N(3)–Si(2)–N(4) 93.98(7).
Fig. 3 Molecular structure of compound 4b. Selected bond lengths
Slow addition of 1 to an excess of ButCl gave as the major
component the disilane 6a and the monosilane 6b as the minor
(A) and angles (◦): Si(1)–N(1) 1.7133(18), Si(1)–C(33) 1.889(2),
˚
Si(1)–Cl(1) 2.0737(8), Si(1)–Si(2) 2.3481(8), Si(2)–N(3) 1.7139(19),
Si(2)–N(4) 1.7225(18), Si(2)–Cl(2) 2.0896(8); N(1)–Si(1)–C(33)
105.32(9), N(1)–Si(1)–Si(2) 116.57(7), N(3)–Si(2)–N(4) 94.39.
1
product (ca. 20% as judged by the H NMR spectrum of the
reaction mixture). In an NMR experiment, the reaction of 1 with
ButCl in a ratio 2.4 : 1 was shown to proceed slowly. However,
the reaction was fast when an excess of ButCl was used. The
disilane 6a is thermally labile and was readily converted into 6b
and 1 (Scheme 5).
The reaction with PhCl needed more vigorous conditions;
conversion into the mono-insertion product 7 was achieved at
140 ◦C. However, even after 1 month, the reaction had not gone
to completeness.
2 9 4 6
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3

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Table 1 Crystal and refinement data for 2a, 3a, 4b and 11d
2a
3a
4b
11d
Empirical formula
M
C35H59ClN4Si2
627.49
C33H54Cl2N4Si2
633.88
C35H58Cl2N4Si2
661.93
C65H106Br2N8Si4. 1.5(C6H6)
1388.92
Crystal system
Monoclinic
C2/c (No. 15)
37.6052(5)
10.2296(1)
19.9346(2)
90
105.446(1)
90
7391.59(14)
8
Triclinic
Triclinic
Triclinic
¯
¯
¯
Space group
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
˚
a/A
10.2646(5)
18.5123(10)
10.6180(5)
99.309(3)
70.322(3)
82.774(3)
1839.2(2)
2
9.5407(3)
11.9325(4)
17.3185(5)
90.626(2)
98.687(2)
104.831(1)
1881.53(10)
2
14.8293(3)
15.1696(3
19.1719(3)
87.796(1)
67.561(1)
76.029(1)
3861.41(12)
2
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
d
calc/mg m−3
1.13
0.20
1.15
0.27
1.17
0.27
1.20
1.16
l(Mo-Ka)/mm−1
Reflections collected
38024
9307
27787
52154
Independent reflections
Reflections with I > 2r(I)
data/parameters
Final R indices [I > 2r(I)] R1, wR2
R indices (all data) R1, wR2
6480 [R(int) = 0.042]
4765 [R(int) = 0.041]
7412 [R(int) = 0.055]
13561 [R(int) = 0.048]
5583
4133
5578
10267
6480/379
0.041, 0.096
0.051, 0.101
4765/379
0.084, 0.195
0.096, 0.201
7412/388
0.047, 0.106
0.071, 0.118
13561/793
0.044, 0.091
0.068, 0.101
The reaction of 1 with PhBr afforded as major product 9a,
which was converted into 9b when heated. In an NMR-scale
reaction, however, when a solution of 1 in C6D6 was treated with
an excess of PhBr the ratio of 9a : 9b was 1 : 1.7.
To illustrate the dependence of the ratio of the mono- versus
disilane product on the experimental conditions, the reaction of
1 with cyclopropyl bromide was examined more closely. Thus,
addition of 1 to C3H5Br led to the formation of compound
10b, whilst slow addition of C3H5Br to 1 afforded compound
10a in addition to a small amount of 10b. Compound 10a was
thermally labile and was converted into 10b via silylene extrusion
(Scheme 7). In a separate reaction 10b was treated with 1 in
C6D6 in a sealed NMR tube but no reaction was observed after
several days.
The reaction of 1 with CH2Br2 was somewhat more com-
plicated (Scheme 8). Adding 1 to an excess of CH2Br2 gave
exclusively the mono product 11a, which upon further treatment
with 1 yielded the trinuclear compound 11b as the major and 11c
as the minor component. Thermolysis of 11b afforded 11c via
silylene extrusion. On the other hand, when CH2Br2 was slowly
added to 1 the tetranuclear compound 11d was isolated as the
major component, which upon thermolysis yielded 11c and two
equivalents of 1.
Scheme 5
The reactions with bromocarbons differed, in that, in most
cases, both the mono- and disilane were obtained, depending
on the substrate and/or the reaction conditions. In an NMR
experiment it was shown that when 1 was treated with an excess
of ButBr, compounds 8a and 8b were formed in a ratio 1 : 3
(Scheme 6).
Scheme 6
Scheme 7
Scheme 8
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3
2 9 4 7

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The structure of compound 11d was also confirmed by X-ray
structural analysis, Fig. 4.
propylmethylsilanes 14a and 14c, but also substantial amounts
(almost 50% of the total) of the isomers 14b and 14d, originating
from a radical pathway. Thermolysis of the reaction mixture led
to the conversion of 14c and 14d into 14a and 14b, respectively.
Several pathways describing the halophilic reaction of the
stable silylene Si[N(But)CHCHNBut] [abbrev. as Si(NꢀNꢀ)] have
been reported recently. Initially, West et al. proposed the forma-
tion of a weak acid–base adduct, which might accept additional
coordination by another silylene, followed by a 1,3-shift [(1) in
Scheme 12].18 On the other hand, Su postulated, on the basis of
DFT calculations, that a donor–acceptor intermediate is formed
initially, in which the lone pairs of a chlorine atom donate
electrons into the empty p-orbital of the silylene. This leads
to the formation of a halosilane. An additional silylene then
undergoes insertion into the Si–Hal bond to give the disilane
[(2) in Scheme 12].20,21
Further investigations, however, revealed that a mechanism
•
involving radicals is more likely.4 Thus, the presence of CCl3
radicals was found by matrix isolation studies of the reaction
of Si(NꢀNꢀ) with CCl4, and in the reaction of Si(NꢀNꢀ) with
CHCl3 small amounts of HCl2CCCl2H (ca. 1.5%) were detected
by 1H and 13C NMR. Additional support for a radical pathway
[(3) in Scheme 12] was recently provided by McKee, et al.22 on
the basis of theoretical calculations (DFT) for the reaction of
[N(H)CHCHNH]Si and MeX (X = Cl, Br, I). Thus, it was found
that the free energy of activation for the radical mechanism is
16–23 kcal mol−1 lower than for a concerted oxidative addition.
The calculations also predicted a mixture of monosilane and
disilane product on the basis that the free energies of the
transition states for the propagation step (3c) and (3d) are
very similar. It was concluded that the ratio of mono- and
disilane arise from the competition between steps (3c) and (3d)
(Scheme 12).
Fig.
4
Molecular structure of compound 11d. Selected bond
lengths (A) and angles (◦): Br(1)–Si(4) 2.2769(8), Br(2)–Si(1)
2.2574(8), Si(1)–N(1) 1.729(2), Si(1)–N(2) 1.730(2), Si(1)–Si(2)
2.4036(10), Si(2)–N(4) 1.738(2), Si(2)–N(3) 1.743(2), Si(2)–C(33)
1.884(3), Si(3)–N(6) 1.733(2), Si(3)–N(5) 1.742(2), Si(3)–C(33) 1.871(3),
Si(3)–Si(4) 2.3962(10), Si(4)–N(8) 1.723(2), Si(4)–N(7) 1.724(2);
N(1)–Si(1)–N(2) 92.78(11), N(3)–Si(2)–N(4) 93.12(11), N(5)–Si(3)–N(6)
93.17(10), N(7)–Si(4)–N(8) 93.39(11).
˚
The reaction of 1 with Me2CBr2 gave the 1 : 1 adduct 12a,
which with further 1 furnished the C2-symmetric compound
12b (Scheme 9).
For the reaction of the bis(alkyl)silylene Si(RK)2 with RCl
(R = ClCH2 or C3H5CH2) (Scheme 3) Kira, et al.19 suggested
the initial formation of a 1 : 1 adduct [(RK)2Si · · · ClR]. A small
amount of observed (RK)2SiCl2 points to a second pathway
involving radicals;24 this is only of secondary importance in the
reaction withCH2Cl2 andC3H5CH2Cl, butplays a dominantrole
in the reaction with CHCl3 or CCl4, where the major product
was the dichlorosilane (RK)2SiCl2.19
The results presented here show convincing evidence for a
radical pathway. Thus, the reaction of 1 with (bromomethyl)-
cyclopropane (Scheme 11) gave a product distribution of
cyclopropylmethyl : 1-butenyl-substituted silanes in a ratio of
55 : 45. For the reaction of 1 with (chloromethyl)cyclopropane
we found, however, only ca. 1% of the 1-butenyl-substituted
silane (Scheme 10).
There is some discussion in the literature about the
mechanism of the reaction of stable silylenes with halocarbons
involving either
a weak acid–base or donor–acceptor
complex,18,19–21 or a radical pathway (vide infra).4,19,22 We there-
fore investigated the reaction of 1 with (chloromethyl)- and
(bromomethyl)cyclopropane. The cyclopropylmethyl radical is
known to convert rapidly and irreversibly into the more stable
1-butenyl isomer (eqn. (1)).23 The distribution of the reaction
products should therefore provide evidence of the involvement
of radicals.
(1)
Thus, an NMR-scale reaction of a solution of 1 in C6D6 with
(chloromethyl)cyclopropane gave (Scheme 10) 13a and only
traces (< 1%) of the radical product 13b. Treatment of 1 with
(bromomethyl)cyclopropane, in an NMR-scale reaction, on the
other hand, afforded (Scheme 11) not only the expected cyclo-
Evidence for a radical mechanism has also been provided for
the reaction of Sn[N(SiMe3)2]2 or Sn[CH(SiMe3)2]2 with an alkyl
or aryl bromide.25,26
Scheme 9
Scheme 10
Scheme 11
2 9 4 8
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3

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Scheme 12
The theoretical calculations for the radical pathway pre-
dict the formation of both, the mono- and disilane [(3c/d)
in Scheme 12]. For the reaction of 1, as well as for
[N(But)CHCHNBut]Si, with an alkyl chloride RCl, however,
the disilane was the exclusive product, regardless of the stoi-
chiometric ratio of the reactants. The monosilane is only formed
when the alkyl group in RCl is bulky. Thus, reaction of 1 with
ButCl gave (Scheme 5) both the 2 : 1-product 6a (major) and
the 1 : 1-product 6b (minor) [cf., with the more steric hindered
Si(NꢀNꢀ),27 only the mono-product was observed (Scheme 2)].18
With bromocarbon reactants, both the mono- and disilane were
obtained. The reactions were directed to favour the mono-
insertion product by adding the silylene 1 slowly to an excess
of bromocarbon, an effect not observed for chlorocarbons. The
proposed radical mechanism22 does not sufficiently account for
the exclusive formation of a disilane from the bis(amino)silylene
and an unhindered alkyl chloride, which leaves open the possible
involvement of other pathways.
We did not find experimental evidence for the second step of
the postulated mechanism by Su as a pathway to the disilane
formation [(2) in Scheme 12]. The monosilane 10b was treated
with 1 at ambient temperature in C6D6 in a sealed NMR tube
over several days and no reaction was observed. Additionally,
monosilanes are formed from the corresponding disilanes by
thermolysis as was shown for 2a, 3a, 6a, 8a, 9a, 10a, 14c or 14d.
Most of these thermolysis were examined in a sealed NMR tube;
no further reaction was observed once 1 and the monosilane
were formed (Scheme 13).
The thermal decomposition of compounds 2a, 6a, 8a, 9a, 10a,
14c and 14d proceeded under relatively mild conditions (100 ◦C)
compared to the thermolysis (at 200 ◦C) of 1,1,2,2-tetramethyl-
1,2-dimethoxydisilane, or the generation of a silylene used as
a so◦urce for preparative purposes in flow pyrolysis at ca. 400–
500 C.30 Such an extrusion of a silylene, as noted for compounds
2a, 6a, 8a, 9a, 10a, 14c and 14d, might provide a convenient
general method to other stable bis(amino)substituted silylenes.
For compounds 3a, 11b and 11d, the result of thermolysis was
not the formation of the corresponding monosilane 3c or 11a.
We propose that elimination of the silylene 1 is rapidly followed
by its insertion into the remaining C–Hal bond of 3c or 11a,
respectively, as illustrated for 3a → 3b in Scheme 14.
The pathway leading to compound 4b and 4c (Scheme 4)
is believed to proceed by a different route (Scheme 15). Upon
thermolysis 4a rearranged to the isolated and crystallographi-
cally characterised (Fig. 3) 4b. Tertiary alkyl halides are highly
polar. The lone pair at a nitrogen atom of 4a can stabilise
an intermediate incipient carbocation which in turn facilitates
migration of the chlorine atom from C → Si yielding 4b. Only
upon prolonged heating of 4b was 4c obtained. A possible
extrusion of (NN)SiCl2 via a-elimination and formation of 4d
was not observed.
Conclusions
The thermally stable silylene 1 [abbrev. as Si(NN)] inserts readily
into the carbon–halogen bond of organic substrates. In general,
depending on the halogen, the reaction yields either exclusively
a disilane of type (NN)Si(Hal)–(R)Si(NN) for Hal = Cl, or a
mixture of such a disilane and the monosilane (NN)Si(R)(Hal)
for Hal = Br. The product distribution for Hal = Br is dependent
on the relative ratio of 1 and RBr. An excess of RBr favours
the formation of (NN)Si(R)Br whereas an excess of 1 favours
the disilane. The mono-insertion product for Hal = Cl is only
formed if the substrate is sterically demanding, e.g., ButCl.
The disilane (NN)Si(Hal)–(R)Si(NN) (Hal = Cl or Br) is not
thermally stable and mild thermolysis yields the corresponding
monosilane (NN)Si(R)(Hal) and the silylene 1. The extrusion of
1 is proposed to proceed by a 1,2-migratory shift of the halogen
from one silicon to the neighbouring silicon atom. This could
The pathway of the thermal decomposition of compounds 2a,
3a, 6a, 8a, 9a, 10a, 11b, 11d, 14c and 14d most likely proceeds
by 1,2-halogen migration (a-elimination). Such a mechanism
was first postulated by Atwell and Weyenberg for the generation
of transient silylenes from appropriate disilanes (Scheme 14).
Thus for example, thermolysis of 1,1,2,2-tetramethyl-1,2-
dimethoxydisilane led to the 1,2-migration of a methoxy group
involving an intermediate such as I (Scheme 13).28,29
Scheme 13
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3
2 9 4 9

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Scheme 14
1
(NCH2), 110.32, 118.48, 140.8 and 142.73 (phenyl). 29Si{ H}
NMR: d −7.9 and 1.36. EI MS: m/z 626 ([M]+, 22%).
[1,2-C6H4(NCH2But)2]Si(Cl)(Pr) (2b). A sample of com-
pound 2a was heated in C6D6 in a sealed NMR tube at 100 ◦C
for 16 h. NMR spectroscopic analysis showed the presence of
compounds 2b and 1 in a 1 : 1 ratio. 1H NMR (500 MHz) for 2b:
d 0.83 (t, 3 H, CH3), 0.94 (s, 18 H, But), 1.24 (m, 2 H, CH2), 1.43
(m, 2 H, CH2), 3.06, 3.09, 3.23 and 3.26 (AB-type, 4 H, NCH2),
1
6.79 and 6.88 (m, 4 H, phenyl). 13C{ H} NMR for 2b: d 16.93
(CH2), 17.51 (CH3), 20.63 (CH2), 28.78 (CMe3), 33.75 (CMe3),
1
55.69 (CH2), 110.27, 118.66 and 140.69 (phenyl). 29Si{ H} NMR
for 2b: d 0.47.
[1,2-C6H4 (NCH2But )2 ]Si(Cl)-(ClCH2 )Si[(NCH2But )2C6H4 -
1,2] (3a). CH2Cl2 (2.2 cm3, 34.3 mmol) was added to a solution
of 1 (0.94 g, 3.43 mmol) in hexane (30 cm3) at −78 ◦C. The
mixture was warmed to ambient temperature and was stirred
for 16 h. The solvent was removed in vacuo and the remaining
residue was extracted into pentane and the extract filtered.
Cooling the filtrate at −25 ◦C afforded 3a as a white solid
(0.79 g, 73%) (Found: C, 62.6; H, 8.54; N, 8.76. C33H54Cl2N4Si2
Scheme 15
have applications for the synthesis of other bis(amino)silylenes,
a topic currently under investigation in our laboratory.
Finally, experimental evidence is presented for a radical
pathway for the reaction of 1 with an alkyl halide.
◦
Experimental
requires C, 62.5; H, 8.59; N, 8.84%), mp 142–143 C. Crystals
suitable for X-ray crystallographic analysis were obtained from
a concentrated solution in pentane at ambient temperature. 1H
NMR: d 0.87 and 0.91 (2 s, 36 H, But), 2.76, 2.83, 3.09 and 3.14
(AB-type, 4 H, CH2), 2.97, 3.02, 3.08 and 3.13 (AB-type, 4 H,
CH2), 3.17 (s, 2 H, CH2Cl) and 6.72–6.83 (m, 8 H, phenyl).
General procedure
All operations and manipulations were carried out under
purified argon, by conventional Schlenk techniques. Solvents
were dried and degassed before use. Microanalyses were carried
out at the University of North London. The NMR spectra
were recorded (at 298 K in C6D6, or otherwise as stated) using
Bruker instruments: Bruker DPX 300 [1H (300.13 MHz), 13C
(75.42 MHz)] and AMX 500 [29Si (99.36 MHz)], and referenced
internally to residual solvent resonances, or externally for 29Si
and referenced to SiMe4 (data in d). Electron impact mass
spectra were taken from solid samples using a Kratos MS 80
RF instrument. Melting points were taken in sealed capillaries
and are uncorrected.
1
13C{ H} NMR: d 28.6 and 29.4 (CMe3), 30.9 (CH2), 33.7
(CMe3), 55.9 and 56.8 (NCH2), 110.4, 110.5, 118.6, 118.7, 140.5
1
and 141.9 (phenyl). 29Si{ H} NMR: d −6.7 and −8.2. EI MS:
m/z 632 ([M]+, 57%).
[{1,2-C6H4(NCH2But)2}Si(Cl)]2CH2 (3b). A solution of 3a
(0.7 g, 1.17 mmol) in benzene (30 cm3) was heated for 2 d
at 100 ◦C. The solvent was removed and the residue was
◦
distilled at 180–200 C (5 × 10−2 Torr) to afford compound
3b as a colourless, viscous oil (0.46 g, 66%) (Found: C, 62.4;
H, 8.67; N, 8.79. C33H54Cl2N4Si2 requires C, 62.5; H, 8.59; N,
8.84%). Alternatively, CH2Cl2 (20 cm3) was added to 1 (1.07 g,
3.91 mmol) and the mixture stirred at ambient temperature for
16 h. The solvent was removed and the residue was distilled to
afford 3b as a pale yellow oil (0.93 g, 75%). 1H NMR: d 0.90 (s,
36 H, But), 1.69 (s, 2 H, CH2), 2.90, 2.95, 3.09 and 3.17 (AB-
type, 8 H, NCH2), 6.7–6.74 and 6.79–6.85 (m, 8 H, phenyl).
[1,2-C6H4 (NCH2But )2]Si(Cl)–(Pr)Si[(NCH2But)2C6H4 -1,2]
(2a). CH3CH2CH2Cl (1.6 cm3, 18.2 mmol) was added to a
solution of 1 (0.5 g, 1.82 mmol) in hexane (20 cm3) at ambient
temperature. The mixture was stirred for 16 h; a white precipitate
formed. The suspension was filtered yielding compound 2a
as a white solid (0.52 g, 92%) (Found: C, 66.9; H, 9.30; N,
8.91. C35H59ClN4Si2 requires C, 67.0; H, 9.48; N, 8.93%),
mp 180–181 ◦C. Crystals suitable for X-ray crystallographic
analysis were obtained from a concentrated solution in hexane
at ambient temperature. 1H NMR (500 MHz): d 0.89 and 0.98
(2 s, 36 H, But), 0.95 (t, 3 H, CH3), 1.33 (m, 2 H, CH2), 1.71 (m,
2 H, CH2), 2.87, 2.9, 3.16 and 3.19 (AB-type, 4 H, NCH2), 3.07,
3.1, 3.11 and 3.13 (AB-type, 4 H, NCH2) and 6.73–6.84 (m, 8
1
13C{ H} NMR: d 13.08 (CH2), 29.14 (CMe3), 33.66 (CMe3),
1
55.53 (NCH2), 110.38, 118.74 and 140.39 (phenyl). 29Si{ H}
NMR: d −5.64. EI MS: m/z 632 ([M]+, 83%).
[1,2-C6H4(NCH2But)2]Si(Cl)–(Me2CCl)Si[(NCH2But)2C6H4-
1,2] (4a). (CH3)2CCl2 (0.47 cm3, 4.48 mmol) was added to
a solution of 1 (1.23 g, 4.48 mmol) in hexane (30 cm3) at
−20 ◦C. The mixture was warmed to ambient temperature and
1
H, phenyl). 13C{ H} NMR: d 16.01 (CH2), 17.84 (CH3), 24.64
(CH2), 28.67 and 29.47 (CMe3), 33.73 (CMe3), 56.3 and 57.45
2 9 5 0
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3

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stirred for 16 h. The solvent was removed in vacuo and the
remaining solid was extracted into hexane and the extract was
filtered. The filtrate was concentrated and compound 4a (0.94 g,
64%) was obtained as a white solid after several days at room
temperature. (Found: C, 63.7; H, 9.03; N, 8.33. C35H58Cl2N4Si2
requires C, 63.5; H, 8.83; N, 8.46%), mp 135–136 ◦C. In an
NMR experiment, a solution of 1 in C6D6 was treated with an
−25 ◦C to afford compound 6a as a white solid (0.31 g, 60.3%)
(Found: C, 67.5; H, 9.62; N, 8.67. C36H61N4Si2Cl requires C,
67.4; H, 9.58; N, 8.73%), mp 143–145 ◦C. 1H NMR: d 0.87 and
1.01 (2 s, 36 H, But), 1.32 (s, 9 H, But), 2.76, 2.81, 3.05 and 3.10
(AB-type, 4 H, CH2), 3.17, 3.22, 3.25 and 3.3 (AB-type, 4 H,
1
CH2) and 6.69–6.83 (m, 8 H, phenyl). 13C{ H} NMR: d 27.2
(CMe3), 29.6 and 29.72 (CMe3), 33.73 and 33.44 (CMe3), 54.18
1
excess of (CH3)2CCl2. Compound 4a was the sole product. H
and 56.47 (CH2), 109.92, 110.95, 117.58, 118.06, 140.26 and
NMR: d 0.87 and 1.01 (2 s, 36 H, But), 1.78 (s, 6 H, CH3), 2.96,
142.2 (phenyl). 29Si{ H} NMR: d −3.3 and 1.4. EI MS: m/z
1
3.01, 3.08 and 3.13 (AB-type, 4 H, CH2), 3.25, 3.3, 3.32 and 3.37
641 ([M]+, 18%).
1
(AB-type, 4 H, CH2) and 6.73–6.81 (m, 8 H, phenyl). 13C{ H}
[1,2-C6H4(NCH2But)2]Si(Cl)(But) (6b). A solution of 6a in
C6D6 was heated in a sealed NMR tube for 16 h at 100 ◦C;
complete conversion into compounds 6b and 1 occurred. Data
for 6b: 1H NMR: d 1.02 (s, 18 H, But), 0.97 (s, 9 H, But), 3.10,
3.15, 3.30 and 3.35 (AB-type, 4 H, CH2), and 6.76–6.87 (m, 4 H,
NMR: d 29.8 (Me), 30.0 (CMe3), 33.6 and 33.9 (CMe3), 54.7
and 56.5 (CH2), 59.6 (Me2C), 110.3, 111.4, 118.0, 118.6, 140.5
1
and 141.8 (phenyl). 29Si{ H} NMR: d −6.3 and −11.0. EI MS:
m/z 661 ([M]+, 24%).
[1,2-C6H4N(CH2But)C(Me)2Si(Cl)N(CH2But)]–(Cl)Si[(NCH2-
But)2C6H4-1,2] (4b). A solution of 4a (0.8 g, 1.21 mmol) in
benzene (30 cm3) was heated at 100 ◦C for 16 h. The solvent was
removed and the residue was extracted into hexane and filtered.
1
phenyl). 13C{ H} NMR: d 25.72 (CMe3), 27.06 (CMe3), 29.64
(CMe3), 34.19 (CMe3), 54.97 (CH2), 109.73, 118.14 and 140.33
1
(phenyl). 29Si{ H} NMR: d 1.6.
[1,2-C6H4(NCH2But)2]Si(Cl)(Ph) (7). A solution of 1 and an
excess of PhCl in C7D8 was heated in a sealed NMR tube for
1 month at 140 ◦C to afford compound 7; ca. 6% of 1 was still
unconsumed. Data for 7: 1H NMR: d 0.73 (s, 18 H, But), 2.95,
3.00, 3.19 and 3.24 (AB-type, 4 H, CH2), 6.75–7.05 (m, phenyl;
together with unreacted 1 and C6H5Cl) and 7.59–7.62 (m, 2 H,
◦
The filtrate was cooled at −25 C to afford 4b (0.6 g, 75%) as
white solid (Found: C, 63.7; H, 8.79; N, 8.37. C35H58Cl2N4Si2
◦
requires C, 63.5; H, 8.83; N, 8.46%), mp 184–186 C. Crystals
suitable for X-ray crystallographic analysis were obtained from
a concentrated solution in hexane at ambient temperature. A
solution of compound 4a in C7D8 was heated in a NMR tube for
2 h, which revealed that complete and exclusive rearrangement
1
phenyl). 13C{ H} NMR: d 28.61 (CMe3), 33.50 (CMe3), 55.77
1
(CH2), 110.11, 118.69, 126.30, 128.46, 130.69, 131.85 and 140.66
to 4b had taken place. H NMR (318 K, C7D8): d 0.54 and
1
(phenyl). 29Si{ H} NMR: d −10.7.
1.39 (2 s, 6 H, Me), 0.88, 0.93, 1.02 and 1.04 (4 s, 36 H, But),
2.73, 2.76, 3.16 and 3.19 (AB-type, 2 H, NCH2), 3.31 (s, 2 H,
NCH2), 2.85, 2.88, 2.96 and 2.99 (AB-type, 2 H, NCH2), 3.37,
3.40, 3.66 and 3.69 (AB-type, 2 H, NCH2), and 6.64–7.03 (m,
[1,2-C6H4(NCH2But)2]Si(Br)–(But)Si[(NCH2But)2C6H4-1,2]/
[1,2-C6H4(NCH2But)2]Si(Br)(But) (8a/b). In an NMR experi-
ment a solution of 1 in C6D6 was treated with an excess of ButBr.
The reaction proceeded rapidly; in the 1H NMR spectrum,
signals for both the di-(8a) and mono-(8b) insertion product
were found in a ratio of 1 : 3. NMR spectroscopic data for
compound 8b were obtained by heating the above sample in a
1
8 H, phenyl). 13C{ H} NMR (318 K, C7D8): d 22.37 and 26.26
(CMe2), 28.93, 29.55, 29.66 and 29.72 (CMe3), 33.66, 33.93,
33.98 and 34.49 (CMe3), 53.57 (CMe2), 51.47, 55.12, 55.62 and
55.83 (NCH2), 110.05, 110.34, 118.58, 119.27, 120.75, 122.29,
1
123.41, 139.39, 140.49, 140.68 and 141.79 (phenyl). 29Si{ H}
◦
sealed NMR tube at 100 C for 16 h. 8b was the sole product
NMR (318 K, C7D8): d −1 and −8. EI MS: m/z 660 ([M]+,
1
apart from unconsumed ButBr. H NMR for 8a: d 0.89 and
1.04 (2 s, 36 H, But), 1.34 (s, 9 H, But), 2.79, 2.84, 2.98 and
3.03 (AB-type, broad, 4 H, CH2), 3.13, 3.18, 3.24 and 3.29
(AB-type, broad, 4 H, CH2), and 6.68–6.84 (m, 12 H, phenyl
44%).
[{1,2-C6H4(NCH2But)2}Si(Cl)]2CMe2 (4c). A solution of 4b
in C7D8 was heated at 140 ◦C in an NMR tube for 10 days,
resulting in the complete rearrangement of 4b into 4c. 1H NMR
(C7D8): d 0.91 (s, 36 H, But), 1.36 (s, 6 H, Me), 2.93, 2.98, 3.17 and
3.22 (AB-type, 8 H, NCH2), 6.56–6.60 and 6.65–6.70 (m, 8 H,
1
of 8a and 8b). 13C{ H} NMR for 8a: d 27.59 (CMe3), 30.1 and
30.22 (CMe3), 33.74 and 33.93 (CMe3), 54.34 and 56.86 (CH2),
110.49, 111.25, 117.93, 118.39, 140.46 and 142.43 (phenyl).
1
29Si{ H} NMR for 8a: d −6.5 and 0.9. 1H NMR for 8b: d
1
phenyl). 13C{ H} NMR (C7D8): d 22.78 (CMe2), 25.62 (CMe2),
0.99 (s, 9 H, But), 1.05 (s, 18 H, But), 3.15, 3.20, 3.28 and 3.33
29.65 (CMe3), 34.07 (CMe3), 54.61 (NCH2), 110.09, 118.21 and
1
(AB-type, 4 H, CH2) and 6.76–6.85 (m, 4 H, phenyl). 13C{ H}
1
139.5 (phenyl). 29Si{ H} NMR (C7D8): d −4.2.
NMR for 8b: d 27.02 (CMe3), 30.02 (CMe3), 34.15 (CMe3),
[1,2-C6H4(NCH2But )2 ]Si(Cl)–(Cl2CH)Si[(NCH2But )2C6H4 -
1,2] (5). CHCl3 (1 cm3) was added to a solution of 1 (1.19 g,
4.34 mmol) in hexane (30 cm3) at −50 ◦C. The mixture was
warmed to ambient temperature and stirred for 16 h. The
solvent was removed in vacuo and the remaining solid was
extracted into hexane and the extract was filtered. Cooling the
filtrate to −25 ◦C afforded compound 5 as a white solid (1.02 g,
70%) (Found: C, 59.4; H, 7.89; N, 8.22. C33H53Cl3N4Si2 requires
C, 59.3; H, 7.99; N, 8.38%), mp 151–152 ◦C. 1H NMR: d 0.9 and
0.95 (2 s, 36 H, But), 2.83, 2.88, 3.07 and 3.12 (AB-type, 4 H,
CH2), 2.98, 3.03, 3.18 and 3.22 (AB-type, 4 H, CH2), 5.45 (s, 1
1
55.19 (CH2), 110.11, 118.29 and 140.45. 29Si{ H} NMR for
8b: d 2.1.
[1,2-C6H42(NCH2But)2]Si(Br)–(Ph)Si[(NCH2But)2C6H4 -1,2]
(9a). PhBr (0.55 cm3, 5.18 mmol) was added via syringe to a
solution of 1 (0.71 g, 2.59 mmol) in hexane (30 cm3) and the
mixture was stirred for 16 h, during which time a precipitate
had formed. The mixture was filtered; the residual solid was
dried to afford compound 9a as a pale yellow solid (0.84 g, 92%)
which was analytically pure by NMR (Found: C, 64.5; H, 8.00;
N, 7.88. C38H57BrN4Si2 requires C, 64.6; H, 8.14; N, 7.94%), mp
182–184 ◦C. 1H NMR (C4D8O): d 0.62 and 1.02 (2 s, 36 H, But),
2.83, 2.88, 3.06 and 3.11 (AB-type, 4 H, NCH2), 2.96, 2.97, 3.01
and 3.02 (AB-type, 4 H, NCH2), 6.6–6.74 (m, 4 H, phenyl),
7.49–7.56 (m, 3 H, phenyl) and 8.10–8.13 (d, 2 H, phenyl).
1
H, CHCl2), 6.7–6.8 (m, 8 H, phenyl). 13C{ H} NMR: d 29.16
and 29.51 (CMe3), 33.63 and 33.86 (CMe3), 55.28 and 57.19
(CH2), 60.59 (CHCl2), 110.52, 110.98, 118.66, 119.0, 140.38
1
and 141.76 (phenyl). 29Si{ H} NMR: d −8.7 and −14.3. EI MS:
1
13C{ H} NMR (C4D8O): d 28.96 and 30.02 (CMe3), 34.08 and
m/z 668 ([M]+, 84%).
34.21 (CMe3), 56.40 and 57.66 (NCH2), 110.54, 110.88, 118.60,
[1,2-C6H4(NCH2But )2 ]Si(Cl)–(But )Si[(NCH2But )2C6H4 -1,2]
(6a). A solution of 1 (0.44 g, 1.61 mmol) in hexane (30 cm3)
was added to a solution of ButCl (3.5 cm3, 32 mmol) in hexane
(10 cm3). The mixture was stirred for 16 h. The solvent was
removed in vacuo and the remaining solid was extracted into
pentane; the extract was filtered and the filtrate cooled at
118.68, 141.26 and 142.77 (phenyl), 129.02, 132.84 and 137.12
1
(phenyl). 29Si{ H} NMR (C4D8O): d −10.9 and −12.4. EI MS:
m/z 706 ([M]+, 25%).
[1,2-C6H4(NCH2But)2]Si(Br)(Ph) (9b). A solution of 9a in
C6D6 was heated at 100 ◦C for 16 h in a sealed NMR tube,
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3
2 9 5 1

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1
resulting in the complete conversion to compound 9b and an
(decomp) (unsatisfactory microanalysis obtained). H NMR:
equivalent of 1. Data for 9b: H NMR: d 0.79 (s, 18 H, But),
d 0.79, 1.01 and 1.06 (3 s, 54 H, But), 2.01 (s, 2 H, CH2), 3.05,
3.08, 3.11, 3.13, 3.14, 3.23, 3.26, 3.48, 3.50 (broad, overlapping
AB-type, 12 H, NCH2) [at 348 K all 12 expected signals for
NCH2, 3.06, 3.07, 3.09. 3.092, 3.10, 3.11, 3.12, 3.15, 3.23, 3.26,
1
3.08, 3.13, 3.29 and 3.34 (AB-type, 4 H, NCH2), 6.73–7.26 (m,
1
7 H, phenyl) and 7.72–7.76 (m, 2 H, phenyl). 13C{ H} NMR: d
28.84 (CMe3), 33.57 (CMe3), 56.12 (NCH2), 110.54, 118.98 and
140.76 (phenyl), 128.53, 132.10 and 136.48 (phenyl). 29Si{ H}
3.40, 3.43] and 6.71–6.84 (m, 12 H, phenyl). 13C{ H} NMR: d
1
1
NMR: d −9.7.
19.53 (CH2), 28.77, 29.88 and 29.96 (CMe3), 33.69, 33.87 and
33.89 (CMe3), 55.16, 56.32 and 57.66 (NCH2), 110.65, 110.87,
110.95, 118.49, 118.73, 118.77, 140.41, 140.54 and 142.13
Compound 9a/9b. In an NMR experiment, a solution of 1 in
C6D6 was treated with an excess of PhBr at ambient temperature.
A mixture of 9a and 9b in relative ratio 1 : 1.7 had formed after
several minutes.
(phenyl). 29Si{ H} NMR: d −8.46, −10.89 and −17.9. EI MS:
1
m/z 966 ([M]+, 1.5%).
[{1,2-C6H4(NCH2But)2}Si(Br)]2CH2 (11c). A solution of
11b or 11d in C6D6 was heated at 100 ◦C for 16 h or 48 h
in a sealed NMR tube, facilitating the formation of 11c and
[1,2-C6H4(NCH2But)2]Si(Br)–(C3H5)Si[(NCH2But)2C6H4-1,2]
(10a). Bromocyclopropane (0.46 cm3, 5.8 mmol) was slowly
added to a solution of 1 (0.8 g, 2.92 mmol) in hexane (40 cm3).
The mixture was stirred for 16 h. The solvent was removed in
vacuo; the residue was extracted into pentane and the extract
was filtered. Cooling the filtrate at −25 ◦C afforded compound
10a as a white solid (0.54 g, 55.7%) (Found: C, 61.2; H, 8.55; N,
8.41. C35H57BrN4Si2 requires C, 62.7; H, 8.58; N, 8.36%), mp
1
1 or 2 equivalents of 1, respectively. Data for 11c: H NMR:
d 0.92 (s, 36 H, But), 2.10 (br. s, 2 H, CH2), 3.02, 3.05, 3.16
and 3.19 (AB-type, br., 8 H, NCH2), 6.74–6.75 and 6.81–6.83
1
(m, 8 H, phenyl). 13C{ H} NMR (348 K): d 20.68 (CH2), 29.5
(CMe3), 33.64 (CMe3), 56.06 (NCH2), 110.85, 118.96 and 141.67
1
(phenyl). 29Si{ H}NMR: d −9.64.
◦
1
125–126 C. H NMR: d 0.06 (ttt, 1 H, CH, J 9.59, 6.90 Hz),
0.90 (m, 2 H, CH2, partially hidden by But), 0.65 (m, 2 H, CH2),
0.92 and 1.0 (2 s, 36 H, But), 2.82, 2.85, 3.0 and 3.03 (AB-type,
4 H, NCH2), 3.01, 3.04, 3.08 and 3.11 (AB-type, 4 H, NCH2),
[{1,2-C6H4(NCH2But )2Si(Br)}-{Si(NCH2But )2C6H4-1,2}]2 -
CH2 (11d). CH2Br2 (1 cm3, 15 mmol) in hexane (50 cm3) was
added slowly to a solution of 1 (0.82 g, 2.99 mmol) in hexane
(20 cm3) at ambient temperature. The mixture was stirred for
16 h. The solvent was removed in vacuo; the remaining solid
was extracted into pentane and the extract filtered. Cooling
the filtrate at −25 ◦C afforded compound 11d as a white
1
6.7–6.74 and 6.77–7.16 (m, 8 H, phenyl). 13C{ H} NMR: d
−0.42 (CH), 4.1 (CH2), 29.13 and 29.92 (CMe3), 33.87 and
34.22 (CMe3), 54.69 and 55.85 (NCH2), 110.07, 110.49, 118.06,
1
118.22, 140.26 and 141.78 (phenyl). 29Si{ H} NMR: d −8.6 and
2.1. EI MS: m/z 670 ([M]+, 4%), 396 ([M − 1]+, 25%).
◦
crystalline solid (0.61 g, 64%), mp 177–179 C (unsatisfactory
[1,2-C6H4(NCH2But)2]Si(Br)(C3H5) (10b). The silylene 1
(0.54 g, 1.97 mmol) in hexane (30 cm3) was added slowly to a
solution of bromocyclopropane (0.79 cm3, 9.85 mmol) in hexane
(30 cm3) at ambient temperature. The mixture was stirred for
16 h. The solvent was removed in vacuo; the residue was extracted
into pentane and the extract was filtered. Cooling the filtrate at
−25 ◦C afforded compound 10b as a white solid (0.44 g, 56.4%)
(Found: C, 57.8; H, 8.01; N, 6.96. C19H31BrN2Si requires C, 57.7;
microanalysis obtained). Crystals suitable for X-ray analysis
were obtained from a saturated benzene solution at ambient
1
temperature. H NMR (338 K): d 0.80 (br. s, 36 H, But), 1.11
(br. s, 36 H, But), 1.44 (s, 2 H, CH2), 2.89 and 2.93 (AB-type,
v. br. with shoulder, 8 H, NCH2), 3.05, 3.07, 3.20 and 3.22
(AB-type, v. br., 8 H, NCH2) and 6.56–6.71 (m, 16 H, phenyl).
1
29Si{ H} NMR: d −8.7 and −15.6. EI MS: m/z 997 ([M − 1]+,
10%), 723 ([M − 21]+, 100%).
◦
1
H, 7.90; N, 7.08%), mp 124–125 C. H NMR: d −0.36 (ttt, 1
H, CH, J 9.07, 6.50 Hz), 0.44 (m, 2 H, CH2), 0.77 (m, 2 H,
CH2), 0.95 (s, 18 H, But), 3.06, 3.11, 3.29 and 3.26 (AB-type, 4
[1,2-C6H4(NCH2But)2]Si(Br)(CMe2Br) (12a). A solution of
1 (1 g, 3.65 mmol) in hexane (30 cm3) was slowly added to a
solution of Me2CBr2 (2.06 cm3, 18.25 mmol) in hexane (20 cm3)
at −50 ◦C. The mixture was warmed to ambient temperature and
stirred for 16 h. The solvent was removed; the remaining residue
was extracted into pentane and the extract filtered. Cooling the
filtrate at −25 ◦C afforded compound 12a as colourless crystals
(1.13 g, 65%) (Found: C, 48.1; H, 6.72; N, 5.79. C19H32Br2N2Si
1
H, NCH2), 6.82–6.92 (m, 4 H, phenyl). 13C{ H} NMR: d −2.37
(CH), 4.35 (CH2), 29.0 (CMe3), 33.9 (CMe3), 55.08 (NCH2),
1
110.34, 118.69 and 139.87 (phenyl). 29Si{ H} NMR: d 3.5. EI
MS: m/z 396 ([M]+, 31%).
Thermal decomposition of compound 10a. A solution of 10a
◦
was heated in C6D6 in a sealed NMR tube at 100 C for 16 h.
◦
1
requires C, 47.9; H, 6.77; N, 5.88%), mp 89–91 C. H NMR:
1
1H and 29Si{ H} NMR analysis showed signals corresponding
d 1.03 (s, 18 H, But), 1.57 (s, 6 H, CH3), 3.25, 3.30, 3.38 and
to compound 10b and the silylene 1.
1
3.43 (AB-type, 4H, CH2), 6.76–6.83 (m, 4 H, phenyl). 13C{ H}
[1,2-C6H4(NCH2But)2]Si(Br)(CH2Br) (11a). A solution of
CH2Br2 (2 cm3, 28.4 mmol) in hexane (20 cm3) was added
to a solution of 1 (0.78 g, 2.85 mmol) in hexane (30 cm3)
at −78 ◦C. The mixture was warmed to ambient temperature
and stirred for 16 h. The solvent was removed ◦in vacuo and
the remaining residue was distilled at 140–150 C (5 × 10−2
Torr) to afford compound 11a as a colourless very viscous oil
NMR: d 29.95 (CMe3), 30.56 (CH3), 34.32 (CMe3), 54.60 (CH2),
110.39, 118.59 and 139.89 (phenyl), signal for CMe2 is probably
very broad and lies under signal for CH2, but was detected at
1
low temperature in C7D8. 13C{ H} NMR (228 K, C7D8): d 29.51
(CMe3), 29.83 (CH3), 34.39 (CMe3), 53.87 (CH2), 54.71 (CMe2),
1
109.88, 118.21 and 139.47 (phenyl). 29Si{ H} NMR: d −10.38.
EI MS: m/z 476 ([M]+, 47%).
1
(0.43 g, 34%), which was shown to be 95% pure by NMR. H
[{1,2-C6H4(NCH2But)2}Si(Br)]2CMe2 (12b). A solution of
12a in C6D6 was treated with 1 in an NMR tube. The sole
products were 12 and unreacted 1. Data for 12b: 1H NMR: d 1.00
(s, 18 H, But), 1.41 (s, 3 H, CH3), 3.04, 3.09, 3.19 and 3.24 (AB-
NMR: d 0.93 (s, 18 H, But), 2.75 (s, 2 H, CH2), 3.08, 3.13, 3.22
and 3.27 (AB-type, 4 H, NCH2), 6.77–6.87 (m, 4 H, phenyl).
1
13C{ H} NMR: d 14.89 (CH2), 28.69 (CMe3), 33.61 (CMe3),
1
56.17 (NCH2), 110.81, 119.21 and 140.4 (phenyl). 29Si{ H}
1
type, 4 H, CH2) and 6.62–6.76 (m, 4 H, phenyl). 13C{ H} NMR:
NMR: d −12.2. EI MS: m/z 448 ([M]+, 21%).
d 23.62 (CH3), 29.27 (CMe2), 30.15 (CMe3), 34.01 (CMe3),
[{1,2-C6H4 (NCH2But )2 }Si(Br)]-CH2 -[Si{(NCH2But )2C6H4 -
1
54.97 (CH2), 110.46, 118.4 and 139.70 (phenyl). 29Si{ H} NMR:
1,2}]-[(Br)Si{(NCH2But)2C6H4-1,2}] (11b).
A solution of
d − 4.6.
11a (0.54 g, 1.2 mmol) in hexane (30 cm3) was slowly added
to a solution of 1 (0.66 g, 2.4 mmol) in hexane (20 cm3).
The mixture was stirred for 16 h, and concentrated in vacuo.
Cooling the concentrate at −25 ◦C afforded compound 11b
as yellow–orange crystals (0.73 g, 61.3%), mp 104–106 ◦C
Reaction of 1 with C3H5CH2Cl. In an NMR experiment,
a solution of 1 in C6D6 was treated with a few drops of
C3H5CH2Cl. The mixture was shown to consist of 13a and only
traces (< 1%) of 13b, with unreacted C3H5CH2Cl.
2 9 5 2
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3

View Article Online
[1,2-C6H4(NCH2But)2]Si(Cl)–(C3H5CH2)Si[(NCH2But)2C6H4-
1,2] (13a). C3H5CH2Cl (0.24 cm3, 2.59 mmol) was added
to a solution of 1 (0.71 g, 2.59 mmol) in hexane (20 cm3).
The mixture was stirred for 16 h at ambient temperature. The
solvent was removed in vacuo; the remaining solid was extracted
into warm hexane and the extract was filtered. The filtrate was
structures were refined on all F2 using SHELXL-97.31 For 3a the
diffraction was limited and weak and the Cl and CH2Cl groups
are disordered equally between the two sites in the molecule with
C/Cl disorder unresolved. Crystal data and refinement details
are presented in Table 1.
CCDC reference numbers 273147–273150.
See http://dx.doi.org/10.1039/b507462b for crystallographic
data in CIF or other electronic format.
◦
cooled to −25 C to afford 13a as a white solid (0.5 g, 60.5%)
(Found: C, 67.7; H, 9.21; N, 8.74. C36H59ClN4Si requires C,
67.6; H, 9.30; N, 8.76%), mp 158–160 ◦C. 1H NMR: d 0.10 (m,
2 H, CH2), 0.43 (m, 2 H, CH2), 0.87 (m, 1 H, CH), 0.92 and
0.97 (2 s, 36 H, But), 1.44 (d, 2 H, CH2), 2.89, 2.92, 3.15, 3.16,
3.17, 3.18, 3.19, 3.22 (AB-type, 8 H, NCH2), and 6.76–6.85 (m,
Acknowledgements
We thank the EPSRC for an Advanced Fellowship for B. G. and
the University of Payam-Noor, Iran for a visiting grant for M. D.
1
8 H, phenyl). 13C{ H} NMR: d 4.10 (CH), 9.40 (CH2), 26.93
(CH2), 28.80 and 29.48 (CMe3), 33.79 (CMe3), 56.23 and 57.35
(NCH2), 110.31, 110.38, 118.43, 118.46, 140.80 and 142.72
References
1
(phenyl). 29Si{ H} NMR: d −8.4 and 0.4. EI MS: m/z 638
([M]+, 31%).
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C3H5CH2Br. The mixture was shown to consist of 14a, 14b,
14c, and 14d in a ratio of 1 : 2.87 : 8.96 : 5.34, and unreacted
C3H5CH2Br. Heating the sealed NMR sample at 100 ◦C for 16 h
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1
6.77–6.87 (m, 8 H, phenyl of 14a and 14b). 13C{ H} NMR of 14a:
d 5.59 (CH), 26.43 (CH2), 29.06 (CMe3), 33.80 (CMe3), 55.81
1
(NCH2), 110.56, 118.77 and 140.51 (phenyl). 29Si{ H} NMR of
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4 H, NCH2), 4.9 (ddt, 1 H, CH, J 10.15, 1.55 Hz), 4.96 (ddt, 1
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1
6.17 Hz) and 6.77–6.87 (m, 8 H, phenyl of 14a and 14b). 13C{ H}
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=
=
(CMe3), 55.72 (NCH2), 114.31 ( CH2), 138.99 ( CH), 110.57,
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1
118.84 and 140.35 (phenyl). 29Si{ H} NMR of 14b: d − 0.5.
[1,2-C6H4(NCH2But)2]Si(Br)–(C3H5CH2)Si[(NCH2But)2C6H4-
1,2]/[1,2-C6H4(NCH2But)2]Si(Br)–(CH2CHCH2CH2)Si[(NCH2-
But)2C6H4-1,2] (14c/14d).
A
solution of C3H5CH2Br
16 S. Ishida, T. Iwamoto, C. Kabuto and M. Kira, Nature, 2003, 421,
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to a solution of 1 (0.95 g, 3.47 mmol) in hexane (20 cm3).
The mixture was stirred for 16 h at ambient temperature. The
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1
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1
13C{ H} NMR of 14c: d 4.14 (CH), 9.44 (CH2), 26.68 (CH2),
28.89 and 29.71 (CMe3), 33.76 and 33.90 (CMe3), 56.30 and
57.21 (NCH2), 110.41, 110.76, 118.44, 118.63, 140.66 and 142.6
1
(phenyl). 29Si{ H} NMR of 14c: d −1.2 and −13.9. 1H NMR of
14d: d 0.89 and 0.98 (2 s, 36 H, But), 2.46 (m, 2 H, CH2), 3.08,
3.11, 3.23, 3.267, 3.27 and 3.30 (AB-type, 8 H, NCH2, partly
overlapped with signals of 14c), 4.96 (br. d, 2 H, CH2), 5.08 (br.
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1
of 14c and 14d). 29Si{ H} NMR of 14d: d −0.4 and −14.6.
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Crystal data and refinement details for (2a), (3a), (4b) and (11d).
Data were collected using monochromated Mo-Ka radiation,
˚
k = 0.71073 A at 173(2) K, with the crystal under a stream of
cold nitrogen gas, on a Nonius KappaCCD diffractometer. The
D a l t o n T r a n s . , 2 0 0 5 , 2 9 4 5 – 2 9 5 3
2 9 5 3