Synthesis and characterisation of two new binaphthyl trisilanes

Article abstract of DOI:10.1016/j.jorganchem.2008.09.054

The synthesis and characterisation of two binaphthyl trisilanes is described. Reaction between 2,2′-dilithio-1,1′-binaphthyl and 1,3-dichlorohexamethyltrisilane gave 3,3,4,4,5,5-hexamethyl-4,5-dihydro-3H-3,4,5-trisilacyclohepta[2,1-a;4,3-a′]binaphthalene

Full text of DOI:10.1016/j.jorganchem.2008.09.054

Journal of Organometallic Chemistry 694 (2009) 137–141
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Journal of Organometallic Chemistry
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Note
Synthesis and characterisation of two new binaphthyl trisilanes
Alexander G. Russell a, Tatyana Guveli a, Benson M. Kariuki b, John S. Snaith a,
*
a School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
b School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
a r t i c l e i n f o
a b s t r a c t
The synthesis and characterisation of two binaphthyl trisilanes is described. Reaction between 2,20-dilith-
io-1,10-binaphthyl and 1,3-dichlorohexamethyltrisilane gave 3,3,4,4,5,5-hexamethyl-4,5-dihydro-3H-
3,4,5-trisilacyclohepta[2,1-a;4,3-a0]binaphthalene (3). Compound 3 was characterised by 1H, 13C and
29Si NMR spectroscopy and a crystal structure analysis. Reaction between 2,20-dilithio-1,10-binaphthyl
and 1,3-bis(trifluoromethanesulfonyloxy)-1,1,2,3,3-pentamethyltrisilane, generated in situ by treatment
of 1,3-diphenyl-1,1,2,3,3-pentamethyltrisilane with trifluormethanesulfonic acid, gave 3,3,4,5,5-penta-
methyl-4,5-dihydro-3H-3,4,5-trisilacyclohepta[2,1-a;4,3-a0]binaphthalene (7). Analysis by 1H, 13C and
29Si NMR spectroscopy revealed that 7 had a very similar structure to 3.
Article history:
Received 19 August 2008
Received in revised form 19 September
2008
Accepted 29 September 2008
Available online 4 October 2008
Keywords:
Silanes
Trisilanes
Binaphthyl
Structure
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
achieving very high levels of enantiomeric excess, in asymmetric
transformations. A small number of chiral silanes are known, in
Chiral silanes are of considerable interest as asymmetric reduc-
ing agents, and a number of approaches to these systems have
been described [1]. The use of silanes as alternatives to tributyltin
hydride in radical chemistry is also growing in popularity, driven
by their lower toxicity, ease of separation from products and often
greater selectivity [2]. Particularly of note are tris(trimethyl-
silyl)silane 1 and related trisilanes such as 2, developed by Chatgil-
ialoglu and coworkers [3,4].
which a single silicon is connected to the binaphthyl framework
through carbon [1a,9], nitrogen [10] or oxygen [1a] substituents
in the 2 and 20 positions, although the presence of only one silicon
atom in these molecules precludes their use in radical chemistry.
The corresponding systems with silicon in the 2 and 20 positions
are virtually unknown [11], with the few examples published sim-
ilarly incapable of functioning as radical reducing agents.
Herein, we report the first synthesis and structural characterisa-
tion of a chiral trisilane based upon the 1,10-binaphthyl framework.
SiMe3
Me
Me3Si Si SiMe3
Me3Si Si SiMe3
2. Results and discussion
H
1
H
2
Since the Si–H bond is relatively reactive and prone to oxida-
tion, we chose to carry out initial studies on a model system 3 that
did not contain this functionality. Our retrosynthetic strategy is
outlined in Scheme 1, in which the key step is the reaction between
2,20-dilithio-1,10-binaphthyl and dichlorotrisilane 4, itself prepared
from 1,3-diphenylhexamethyltrisilane 5 using known chemistry.
1,3-Diphenylhexamethyltrisilane 5 was synthesised from chlo-
rodimethylphenylsilane: reaction with lithium metal gave dim-
ethylphenylsilyllithium which was then added slowly to
dichlorodimethylsilane at 0 °C, Scheme 2 [12]. After vacuum distil-
lation, 5 was isolated as a colourless oil containing a small amount
of (PhMe2Si)2 as a contaminant. A second distillation gave pure 5 in
67% yield. In our hands, the published procedure using HCl gas and
AlCl3 for cleavage of the silicon-phenyl bonds gave very low yields
of the desired compound, which was inseparable from many other
products confirmed by GC–MS to be formed by over chlorination
For a silane to be an efficient hydrogen atom donor, the silicon bear-
ing the hydrogen must be attached to two or three other silicon
atoms. Whilst there have been reports of chiral stannanes [5] and
germanes [6] as potential asymmetric radical reducing agents, chi-
ral versions of 1 and 2 are unknown in the literature.
A potential solution is to incorporate the silane within a 1,10-
binaphthyl framework. 2,20-Disubstituted-1,10-binaphthyls are axi-
ally-chiral, and are viewed as privileged ligand scaffolds in asym-
metric synthesis. When the substituents at the 2 and 20 positions
are oxygen, e.g. BINOL [7], or phosphorus, e.g. BINAP [8], the result-
ing binaphthyls have found wide application, and are capable of
* Corresponding author. Tel./fax: +44 121 4144363.
E-mail address: j.s.snaith@bham.ac.uk (J.S. Snaith).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.09.054

138
A.G. Russell et al. / Journal of Organometallic Chemistry 694 (2009) 137–141
Si
Li
Li
Si
Si
+
Si
Si
Cl
Si
Cl
Si
Si
Si
Ph Ph
5
4
3
Scheme 1. Retrosynthetic analysis of 3.
ο
Li, THF, 0 C
Cl2SiMe2, THF, 0 οC
AcCl, AlCl3
hexane, RT
Cl
Li
Si
Si
Si
Ph
Si
Ph
Si
Cl
Si
Cl
Si
Si
Ph Ph
5, 67%
4, 47%
Scheme 2. Preparation of dichlorosilane 4.
[12]. The transformation could be much more reliably accom-
plished using acetyl chloride/AlCl3 [13]; after vacuum distillation,
4 was isolated as a colourless oil in 47% yield.
Our second target was 7, in which the central silicon atom bears a
hydrogen substituent. Synthesis of this required trisilane 8, which
was prepared by reaction of PhMe2SiLi, prepared as described pre-
viously, with Cl2MeSiH, affording the product in 64% yield after vac-
uum distillation, Scheme 4.
Lithiation of 2,20-dibromo-1,10-binaphthyl 6 in THF at ꢀ78 °C
and addition of 1,3-dichlorohexamethyltrisilane 4 at the same
temperature, before allowing the mixture to warm to room tem-
perature, gave trisilane 3 in 41% yield as a white solid after column
chromatography, Scheme 3.
The trisilane 8 was accompanied by other unidentified silicon
species which were difficult to separate by column chromatogra-
phy. The yield and purity of 8 was, therefore maximised by follow-
ing the course of the reaction by analytical HPLC and stopping it
before the side-products had formed to a significant extent.
Having obtained a clean sample of 8, the phenyl groups had to
be replaced by leaving groups to generate a species which could be
coupled to dilithiobinaphthyl. We expected that the previously
employed method using AlCl3 and acetyl chloride to generate silyl
chlorides would be problematic since Si–H bonds are known to be
cleaved in the presence of AlCl3/HCl [15]. However, there is litera-
ture precedent for the replacement of phenyl groups by triflate
groups, in the presence of Si–H bonds, using triflic acid [16], and
so bis-triflate 9 became our target. Silyl triflates are more prone
to hydrolysis than silyl chlorides, so rather than attempting to iso-
late and purify bis-triflate 9, we decided to form this reactive spe-
cies in situ and use it immediately (see Scheme 5).
As the lithiation of 6 was carried out in THF, we first attempted
the conversion of 8 into triflate 9 in this solvent. However, the reac-
tion failed and starting material was quantitatively recovered.
Monitoring the formation of the silyl triflate by 1H NMR in deuter-
ated toluene indicated that conversion to the highly moisture sen-
sitive triflate was very clean and complete within 10 min in this
solvent at 0 °C, and so in subsequent experiments 9, was generated
as a solution in toluene and added to a solution of 2,20-dilithio-1,10-
binaphthyl in THF. The reaction was maintained at ꢀ50 °C over-
night to afford, after chromatography, trisilane 7 as a colourless
oil in 30% yield. Attempts to optimise the yield by variation of
the reaction temperature, ratio of reactants and the inclusion of
TMEDA were unsuccessful (see Scheme 6).
Comprehensive NMR experiments were carried out to confirm
the identity and structure of 3. 1H NMR showed three methyl envi-
ronments (at ꢀ0.94, +0.06 and +0.43 ppm) corresponding to two
equivalent methyl groups on the central silicon atom and the two
distinct methyl environments on each of the flanking silicon atoms.
The 29Si NMR displayed two signals (at ꢀ20.15 and ꢀ40.64 ppm) for
the central silicon atom and the two identical flanking silicon atoms.
The non-coplanar nature of the two naphthyl rings means that
whilst one methyl group lies in the plane of the naphthyl unit to
which it is closest, the other methyl group lies out of plane, and
face-on to the other naphthyl ring system. The face-on methyl group
is shielded by the ring current of the aromatic ring, so resonance is
observed at low chemical shift. On the other hand, the edge-on
methyl groups are deshielded by the aromatic ring, leading to reso-
nance at higher chemical shift. The face-on/edge-on arrangement of
methyl groups was confirmed by nOe experiments. Excitation at the
frequency of the peak at +0.43 ppm showed a nOe through to the
proton in position 3 (systematic numbering; C6 and C16 crystallo-
graphic numbering) of the naphthyl ring, confirming the edge-on
arrangement of this methyl group. Excitation at the frequency corre-
spondingto theꢀ0.94 ppmsignalshowedasmallnOetoall aromatic
protons, so confirming the face-on nature of this methyl group.
Single crystals of 3 were obtained by slow evaporation of diethyl
ether and X-ray crystallography provided a crystal structure in
agreement with that suggested by the NMR experiments (see Fig. 1).
H
Crystals of 7 could not be obtained, but 1H, 13C and 29Si NMR
spectra confirmed that the structure was similar to 3. Like 3, 7
exhibited the same face-on and edge-on arrangement of the
methyl groups on the flanking silicon atoms, but since the central
silicon atom was now asymmetrically substituted, these methyl
groups were diastereotopic, resulting in all five methyl groups
being magnetically different and five separate signals being ob-
served. The two face-on methyl groups, shielded by the naphtha-
lene ring current, were observed close together at low chemical
shift (at ꢀ0.74 and ꢀ0.65 ppm), whereas the two edge-on methyl
groups, deshielded by the naphthalene ring, were observed close
together at higher chemical shift (at 0.41 and 0.53 ppm); the
methyl group on the central silicon (at 0.11 ppm) was split into a
doublet as a result of coupling to the Si–H. In the same way, the
Si
Si
Si
7
ο
Si
i. t-BuLi, -78 C, THF
Br
Br
Si
ο
Si
ii. 4, THF, -78 C to RT
6
3, 41%
Scheme 3. Synthesis of binaphthyl trisilane 3.

A.G. Russell et al. / Journal of Organometallic Chemistry 694 (2009) 137–141
139
Fig. 1. (a) ORTEP [14] representation of 3, ellipsoids at 30%. Selected geometry: C(1)–Si(1) = 1.893(2) Å, C(11)–Si(2) = 1.902(2) Å, Si(1)–Si(3) = 2.3365(9) Å, Si(2)–
Si(3) = 2.3474(8) Å, C(1)–Si(1)–Si(3) = 103.71(6) °, C(11)–Si(2)–Si(3) = 104.52(6) °, Si(1)–Si(3)–Si(2) = 103.13(3) °, C(11)–Si(2)–Si(3)–Si(1) = 33.48(7) °, C(1)–Si(1)–Si(3)–
Si(2) = 38.03(7) °. (b) The nOes observed between the edge-on methyl groups and the naphthyl ring.
single enantiomers of 7 and related silanes, and their evaluation as
asymmetric reducing agents in radical chemistry.
H
ο
Cl2SiHMe, THF
Li, THF, 0 C
Cl
Li
Si
Si
Ph
Si
Ph
Si
Si
ο
-30 C to RT
Ph Ph
3. Experimental
8, 64%
3.1. General
Scheme 4. Preparation of trisilane 8.
3.1.1. Chemicals and reagents
H
H
All chemicals and reagents were obtained from commercial
sources and were used as supplied, except for THF and toluene
which were distilled from sodium-benzophenone ketyl and acetyl
chloride which was distilled under argon from PCl5. Solutions of n-
BuLi and t-BuLi were titrated against N-pivaloyl-o-toluidine prior
to use according to a method developed by Suffert [18]. The term
‘‘petrol” refers to the 40–60 °C boiling fraction of petroleum ether.
Thin layer chromatography was carried out on precoated, glass-
backed, silica gel plates (silica gel 60, F254, thickness 0.25 mm, sup-
plied by MerckÒ) and visualisation was achieved using UV light
(254/365 nm) or basic KMnO4 solution. Column chromatography
was performed using laboratory grade solvents on silica gel 60A
TfOH
toluene, 0 οC
Si
Si
Si
Si
Si
Si
OTf OTf
Ph Ph
8
9
Scheme 5.
i. n-BuLi, -78 to -60 οC, THF
H
Si
Br
Br
Si
ii. 9 (in toluene), THF, -60 to -50 οC
Si
(43–63 l
m mesh, supplied by FluorochemÒ) under pressure ap-
6
7, 30%
plied using hand bellows. Unless noted, all Rf were measured using
the column solvent.
Scheme 6. Synthesis of binaphthyl trisilane 7.
All reactions were carried out using oven-dried (150 °C) or
flame-dried glassware and were performed under a positive pres-
sure of argon.
diastereotopicity of the two flanking silicon atoms resulted in three
signals in the 1H-decoupled 29Si spectrum.
In conclusion, we have achieved the synthesis of the first axially-
chiral trisilane, based upon the 1,10-binaphthyl framework. The
methyl groups on the flanking silicon atoms adopt edge-on and
face-on orientations with respect to the naphthalene rings, reinforc-
ing the chiral environment around the Si–H bond. The synthesis
should be amenable to the production of single enantiomers. Mur-
doch and co-workers have shown that 2,20-dilithio-1,10-binaphthyl,
prepared from a single enantiomer of 2,20-dibromo-1,10-binaphthyl,
is configurationally stable at temperatures below ꢀ44 °C [17]. As 7
was prepared at ꢀ50 °C, access to single enantiomers should be pos-
sible starting from enantiomerically pure 2,20-dibromo-1,10-binaph-
thyl. Future work in our laboratory will focus on the synthesis of
3.1.2. Instrumentation
1H- and 13C NMR spectra were recorded on a Bruker AC300 (at
300.13 MHz and 75.47 MHz, respectively), a Bruker AV300 (at
300.13 MHz and 75.48 MHz, respectively), a Bruker AV400 (at
400.08 MHz and 100.60 MHz) or a Bruker DRX500 (at 500.13 MHz
and 125.77 MHz). All 75 MHz 13C spectra were recorded using the
PENDANT pulse sequence. Where necessary, COSY90, HMBC, HSQC
and nOe experiments were carried out to allow unequivocal assign-
ment of signals. 29Si NMR spectra were recorded on a Bruker
DRX500 at 99.35 MHz or a Bruker AV400 at 79.48 MHz.
Chemical shifts (d) are expressed in parts per million (ppm)
downfield from tetramethylsilane. Individual spectra were refer-

140
A.G. Russell et al. / Journal of Organometallic Chemistry 694 (2009) 137–141
enced relative to residual solvent. The multiplicity of signals in 1H
NMR is expressed as follows: s = singlet, d = doublet, q = quartet,
m = multiplet. Coupling constants J are reported in Hz. The term
‘‘multiplet” or ‘‘m” has been used to describe a signal arising from
a single nucleus (or more than one magnetically equivalent nuclei)
where coupling constants cannot be assigned. The term ‘‘envelope”
describes a region of the spectrum when signals from non-equiva-
lent nuclei overlap in such a way that coupling constants cannot be
assigned. In 1H NMR assignments, the signals are described in the
following manner: Chemical shift (relative integration, multiplic-
ity, coupling constant [if applicable], assignment).
Melting points were determined in open glass capillaries using
a Stuart Scientific SMP1 apparatus and are uncorrected.
Infra-red spectra were recorded neat or as a film on NaCl using a
Perkin–Elmer Paragon 1600 FTIR spectrometer, or as solids on a
Shimadzu 8300 FTIR spectrometer.
The reaction mixture was allowed to warm to room temperature
and was stirred overnight. The reaction was monitored by GC to
ensure complete consumption of starting silane. Once reaction
was complete, the pale yellow hexane layer was removed by syr-
inge from the orange lower layer, which was further extracted with
hexane (2 ꢁ 5 mL). The combined hexane layers were concentrated
in vacuo to give a pale brown oil. Two vacuum distillations yielded
4 as a colourless oil (0.61 g, 47%).
B.p. 42–43 °C/0.5 mmHg (lit.7 b.p. 108 °C/30 mmHg); dH
(300 MHz, CDCl3) 0.28 (6H, s, SiSi(CH3)2Si), 0.55 (12H, s,
2 ꢁ Si(CH3)2Cl); dC (75 MHz, CDCl3) ꢀ7.7 (SiSi(CH3)2Si), 3.0
(Si(CH3)2Cl); m/z (EI+) 246 (10% [M]+), 244 (12%), 231 (11%), 229
(51%), 211 (6%), 209 (51%), 186 (3%), 165 (12%), 153 (75%), 151
(83%), 131 (61%), 116 (82%), 101 (32%), 93 (84%), 85 (20%), 73 (100%).
3.4. 3,3,4,4,5,5-Hexamethyl-4,5-dihydro-3H-3,4,5-
trisilacyclohepta[2,1-a;4,3-a0]binaphthalene, 3
Elemental analyses were performed on a Carlo Erba EA1110
simultaneous CHNS analyser.
EI mass spectra were recorded on either a VG ProSpec or VG
Zabspec instrument at 70 eV. High resolution EI spectra were mea-
sured using perfluorokerosene (PFK) as an internal calibrant.
Single crystal diffraction data were recorded at 296(2) K on a Rig-
aku R-axis II diffractometer equipped with a molybdenum rotating
anode source (k = 0.71069 Å) and an image plate detector system.
Structure solution was by direct methods (Molecular Structure Cor-
poration, TEXSAN, Single Crystal Structure Analysis Software, Ver-
sion 1.6. MSC, 3200 Research Forest Drive, The Woodlands, TX
77381, USA, 1993) and refinement by SHELXL92 (G.M .Sheldrick, SHEL-
XL92, Program for the Refinement of Crystal Structures, University
of Gottingen, Germany, 1993). A riding model was used for the
hydrogens with atomic displacement parameters 1.2 times (1.5
times for methyl groups) those of the carbon atoms they are bonded
to.
To a solution of 2,20-dibromobinaphthyl (470 mg, 1.14 mmol) in
THFat ꢀ78 °Cwasaddedviasyringea1.7 Msolutionof t-BuLiinpen-
tane (1.40 mL, 2.38 mmol). The resulting bright yellow solution was
stirred at ꢀ78 °C for 90 min after which a solution of 1,3-dichloro-
hexamethyltrisilane 4 (278 mg, 1.13 mmol) in THF (10 mL) was
added. The reaction was maintained at ꢀ78 °C for a further 60 min
before being allowed to warm to room temperature and stirring
overnight. The reaction mixture was poured into NH4Cl solution
(50 mL), extracted with diethyl ether (4 ꢁ 50 mL) and the combined
diethyl ether layers were dried over MgSO4 and concentrated in va-
cuo. Purification by column chromatography yielded 3 (petrol,
Rf = 0.55) as colourless, crystalline plates (202 mg, 41%).
M.p. 186–190 °C; dH (500 MHz, CDCl3) ꢀ0.94 (6H, s, Si(CH3)CH3-
Si(CH3)2Si(CH3)CH3), 0.06 (6H, s, SiSi(CH3)2Si), 0.43 (6H, s,
Si(CH3)CH3Si(CH3)2Si(CH3)CH3), 7.03 (2H, d, J 8.6, 2 ꢁ H9), 7.13–
7.17 (2H, m, 2 ꢁ H8), 7.38–7.42 (2H, m, 2 ꢁ H7), 7.72 (2H, d, J
8.3, 2 ꢁ H3), 7.87 (2H, d, J 8.3, 2 ꢁ H6), 7.92 (2H, d, J 8.3, 2 ꢁ H4);
dC (75 MHz, CDCl3) ꢀ7.3 (SiSi(CH3)2Si), ꢀ4.7 (Si(CH3)CH3Si(CH3)2-
Si(CH3)CH3), ꢀ4.0 (Si(CH3)CH3Si(CH3)2Si(CH3)CH3), 125.8 (C7),
125.9 (C6), 126.7 (C8), 126.9 (C4), 127.7 (C5), 130.1 (C3), 133.4
(C4a), 134.3 (C8a), 136.9 (C2), 145.5 (C1); dSi (100 MHz, CDCl3)
ꢀ40.8, ꢀ20.4; mmax (solid, cmꢀ1) 3047 (C–H aromatic), 2947 (C–
H), 2893 (C–H), 1913 (aromatic overtone), 1551 (C@C aromatic),
1497 (C@C aromatic), 1450, 1404, 1304, 1242, 1142, 1111, 1026,
949, 802, 756, 671, 594, 548; m/z (EI+) 426 (50%, [M]+), 411 (5%),
367 (6%), 353 (15%), 337 (6%), 310 (27%), 295 (57%), 278 (21%),
252 (81%), 226 (8%), 200 (3%), 146 (6%), 116 (100%), 101 (23%);
HRMS (EI+). Found: 426.1659. Calc. for C26H30Si3: 426.1655; found:
C 73.4, H 7.1, required for C26H30Si3: C 73.2, H 7.1.
3.2. 1,3-Diphenylhexamethyltrisilane, 5
To
a suspension of hexane-washed lithium shot (5.0 g,
714 mmol) in THF (100 mL) at 0 °C was added chlorodimethylphe-
nylsilane (15 mL, 89 mmol) over 5 min and the mixture was stirred
overnight at 0 °C. Dichlorodimethylsilane (5.4 mL, 44.5 mmol) was
dissolved in THF (150 mL) in a flask fitted with a dropping funnel
and cooled to 0 °C. The deep red phenyldimethylsilyllithium solu-
tion was syringed off from the excess lithium and transferred to
the dropping funnel. The silyllithium solution was added dropwise
to the dichlorodimethylsilane solution over 4 h at 0 °C. The reaction
mixturewas allowed to warm toroomtemperatureand stirred over-
night. THF was removed in vacuo and diethyl ether (100 mL) was
added. The precipitated lithium chloride was filtered off and the
diethyl ether solution concentrated in vacuo to give a pale brown
oil. Distillation under vacuum yielded 5 as a colourless oil (9.80 g,
67%).
Crystal data: C26H30Si3, F = 426.77, T = 296(2) K, k = 0.71069 Å,
Orthorhombic, Pbca, a = 17.5436(11) Å, b = 12.8098(8) Å, c =
22.0697(15) Å, volume = 4959.7(6) Å3, Z = 8,
l
collected = 27049, independent reflections = 4480, Rint = 0.089,
r
calc = 1.143 Mg/m3,
= 0.201 mmꢀ1, crystal size = 0.50 ꢁ 0.40 ꢁ 0.30 mm3, reflections
B.p.
145–150 °C/0.05 mmHg)
(lit.7
b.p.
117–120 °C/
0.05 mmHg); dH (300 MHz, CDCl3) 0.20 (6H, s, SiSi(CH3)2Si), 0.40
(12H, s, 2 ꢁ Si(CH3)2Ph), 7.38–7.44 (6H, envelope, 6 ꢁ HAr), 7.46–
7.51 (4H, envelope, 4 ꢁ HAr); dC (75 MHz, CDCl3) ꢀ6.2 (SiSi(CH3)2-
Si), ꢀ3.0 (Si(CH3)2Ph), 128.0 (C3), 128.7 (C4), 134.0 (C2), 139.9
(C1); dSi (100 MHz, CDCl3) ꢀ47.7, ꢀ18.1; mmax (film, cmꢀ1) 3047
(C–H aromatic), 2955 (C–H), 1427, 1242, 1103, 826, 779, 725,
694, 640; m/z (EI+) 328 (13%, [M]+), 193 (51%), 178 (18%), 163
(11%), 135 (100%), 116 (46%), 105 (7%).
parameters = 269, R1 = 0.0519, wR2 = 0.1295 for I > 2
0.0545, wR2 = 0.1307 for all data.
r(I), R1 =
3.5. 1,3-Diphenyl-1,1,2,3,3-pentamethyltrisilane, 8
To a solution of dichloromethylsilane (2.70 mL, 26.0 mmol) in
THF at ꢀ78 °C was added via syringe a 1.1 M solution of PhMe2SiLi
(48 mL, 52.8 mmol). The mixture was slowly allowed to warm to
room temperature and stirred overnight. THF was removed in vacuo
and diethyl ether (100 mL) and water (100 mL) were added. The or-
ganic phase was further washed with water (2 ꢁ 100 mL) and brine
(100 mL) before being dried over MgSO4 and concentrated in vacuo
to yield a pale yellow oil. Kugelrohr distillation (oven temperature
180 °C/1 mmHg) yielded 8 as a colourless oil (5.20 g, 64%).
3.3. 1,3-Dichlorohexamethyltrisilane, 4
To a solution of 1,3-diphenylhexamethyltrisilane, 5 (1.75 g,
5.3 mmol) in hexane (40 mL) at ꢀ10 °C was added acetyl chloride
(0.95 mL, 13.3 mmol) and anhydrous AlCl3 (1.78 g, 13.3 mmol).

A.G. Russell et al. / Journal of Organometallic Chemistry 694 (2009) 137–141
141
dH (300 MHz, C6D6) 0.09 (3H, d, J 5.1, Si(H)CH3), 0.30 (12H, s,
Appendix A. Supplementary material
2 ꢁ Si(CH3)2), 3.30 (1H, q, J 5.1, Si–H), 7.28–7.31 (6H, envelope,
6 ꢁ HAr), 7.38–7.42 (4H, envelope, 4 ꢁ HAr); dC (75 MHz, C6D6)
ꢀ12.1 (Si(H)CH3), ꢀ2.1 (Si(CH3)CH3), ꢀ2.0 (Si(CH3)CH3), 127.9
CCDC 698595 contains the supplementary crystallographic data
for 3. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif. Supplementary material associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem.2008.09.054.
(CHAr), 128.7 (CHAr), 133.9 (CHAr), 135.6 (CAr); mmax (neat, cmꢀ1
)
3063 (C–H aromatic), 2955 (C–H), 2068 (Si–H), 1427, 1250, 1103,
1057, 872, 833, 772, 733, 694, 633; m/z (EI+) 313 (5%, [MꢀH]+),
298 (4%), 255 (11%), 197 (6%), 178 (81%), 163 (38%), 135 (100%),
121 (9%), 105 (15%); HRMS (EI+). Found: 314.1329, required for
C17H26Si3: 314.1342.
References
3.6. 3,3,4,5,5-Pentamethyl-4,5-dihydro-3H-3,4,5-
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To a solution of trisilane 8 (202 mg, 0.62 mmol) in toluene
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dH (400 MHz, C6D6) ꢀ0.74 (3H, s, SiCH3), ꢀ0.65 (3H, s, SiCH3),
0.11 (3H, d, J 5.0, Si(H)CH3), 0.41 (3H, s, SiCH3), 0.53 (3H, s, SiCH3),
3.66 (1H, q, J 5.0, Si–H), 6.87–6.94 (2H, m, 2 ꢁ HAr), 7.14–7.20 (2H,
m, 2 ꢁ HAr), 7.24 (2H, d, J 8.6, 2 ꢁ HAr), 7.69 (2H, d, J 8.1, 2 ꢁ HAr),
7.70–7.82 (4H, envelope, 4 ꢁ HAr); dC (75 MHz, C6D6) ꢀ12.5
(Si(H)CH3), ꢀ4.2 (SiCH3), ꢀ3.2 (SiCH3), ꢀ2.8 (SiCH3), ꢀ1.5 (SiCH3),
126.4 (CHAr), 126.5 (CHAr), 126.5 (CHAr), 127.1 (CHAr), 127.2 (CHAr),
127.5 (CHAr), 127.6 (CHAr), 128.2 (CHAr), 128.3 (CHAr), 130.4 (CHAr),
130.6 (CHAr), 134.2 (CAr), 134.2 (CAr), 135.0 (CAr), 135.0 (CAr), 136.7
(CAr), 136.8 (CAr), 146.1 (CAr), 146.1 (CAr) (Note: One CHAr is ob-
scured by benzene solvent); dSi (80 MHz, C6D6) ꢀ65.9, ꢀ19.6,
ꢀ19.5; mmax (film, cmꢀ1) 3049 (C–H aromatic), 3009 (C–H aro-
matic), 2951 (C–H), 2893 (C–H), 2076 (Si–H), 1924 (aromatic over-
tone), 1584, 1548 (C@C aromatic), 1499 (C@C aromatic), 1454,
1405, 1331, 1306, 1246, 1216, 1150, 1115, 1109, 1024, 948, 871,
835, 809, 792, 760, 684, 668, 636, 626, 608; m/z (EI+) 412 (92%,
[M]+), 397 (12%), 353 (43%), 338 (46%), 309 (13%), 295 (100%),
279 (25%), 265 (15%), 252 (14%), 116 (42%), 102 (47%); HRMS
(EI+). Found: 412.1487. Calc. for C25H28Si3: 412.1499.
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We thank the Engineering and Physical Sciences Research
Council for the award of studentships to A.G.R. and T.G.