Reactivity of a silylsilylene bearing a functionalized diaminochlorosilyl substituent

Article abstract of DOI:10.1002/chem.201002611

The reactivity of the silylsilylene [{PhC(NtBu)₂}SiSi(Cl){(NtBu) ₂C(H)Ph}] (2) towards diphenylacetylene, azobenzene, 2,6-diisopropylphenyl azide, sulfur, and selenium is described. The reaction of 2 with one equivalent of azobenzene in toluene afforded compound 3, which is the first example of a 1,2-diaza-3,4-disilacyclobutane containing a pentacoordinate silicon center. The formation of 3 can be explained by a [1+2] cycloaddition of the divalent Si center in 2 with PhN=NPh to form a diazasilacyclopropane intermediate, which then undergoes a 1,2-chlorine shift to release the ring strain to form 3. Similarly, the reaction of 2 with one equivalent of diphenylacetylene in toluene afforded the 1,2-disilacyclobutene 4, which contains a pentacoordinate silicon center. The reaction of 2 with 1.6equivalents of 2,6-diisopropylphenylazide in toluene afforded the silaimine [LSi(=NAr)N(Ar)L′] (5, L=PhC(NtBu)₂, L′=Si(Cl){(NtBu) ₂C(H)Ph}, Ar=2,6-iPr₂C₆H₃). The formation of 5 can be explained by an oxidative addition of the divalent Si center in 2 with ArN₃ to afford a silaimine intermediate, which then reacts with another molecule of ArN₃ to give compound 5. The reaction of 2 with elemental sulfur in toluene afforded the chlorosilanethione [LSi(S)Cl] (6) and dithiodisiletane [{Ph(H)C(NtBu)₂}Si(μ-S)] ₂ (7). Treatment of 2 with elemental selenium in THF afforded the di(silaneselone) [LSi(Se)Si(Se)L] (8). Evidently, the divalent Si center in 2 undergoes oxidative addition with chalcogens to afford a silylsilanechalcogenone intermediate, which then displaces ":Si{(NtBu)₂C(H)Ph}" and "ClSi{(NtBu)₂C(H)Ph}" to form 6 and 8, respectively. Moreover, compound 8 was synthesized by the reaction of [{PhC(NtBu) ₂}Si:]₂ (10) with elemental selenium in THF. The results show that the reactions of 2 are initiated by oxidative addition of the divalent silicon center, and then the intermediate formed undergoes a rearrangement involving the diaminochlorosilyl substituent to form compounds 3-8. These products have been characterized by NMR spectroscopy and X-ray crystallography. Stable silylenes: The reactivity of the silylsilylene 1 towards diphenylacetylene, azobenzene, 2,6-diisopropylphenyl azide, sulfur, and selenium is reported. The results show that the reactions of 1 are initiated by oxidative addition of the divalent silicon center, and then the intermediate formed undergoes a rearrangement that involves the diaminochlorosilyl substituent (see scheme). The diaminochlorosilyl substituent in 1 can undergo a 1,2-chlorine shift, and it also serves as a leaving group in the reactions. Copyright

Full text of DOI:10.1002/chem.201002611

DOI: 10.1002/chem.201002611
Reactivity of a Silylsilylene Bearing a Functionalized Diaminochlorosilyl
Substituent
Shu-Hua Zhang, Hui-Xian Yeong, and Cheuk-Wai So*[a]
Dedicated to Professor Kevin W.-P. Leung
Abstract: The reactivity of the silylsily-
lene [{PhC(NtBu)2}SiSi(Cl)-
{(NtBu)2C(H)Ph}] (2) towards diphen-
The reaction of 2 with 1.6 equivalents
of 2,6-diisopropylphenylazide in tolu-
THF afforded the di(silaneselone)
[LSi(Se)Si(Se)L] (8). Evidently, the di-
valent Si center in 2 undergoes oxida-
tive addition with chalcogens to afford
a silylsilanechalcogenone intermediate,
G
E
ene afforded the silaimine [LSi
N(Ar)L’] (5, L=PhC(NtBu)2, L’=
Si(Cl){(NtBu)2C(H)Ph}, Ar=2,6-
ACHTUNGTRNE(NUNG =NAr)-
ylacetylene, azobenzene, 2,6-diisopro-
pylphenyl azide, sulfur, and selenium is
described. The reaction of 2 with one
equivalent of azobenzene in toluene af-
forded compound 3, which is the first
example of a 1,2-diaza-3,4-disilacyclo-
butane containing a pentacoordinate
silicon center. The formation of 3 can
be explained by a [1+2] cycloaddition
of the divalent Si center in 2 with
PhN=NPh to form a diazasilacyclopro-
pane intermediate, which then under-
goes a 1,2-chlorine shift to release the
ring strain to form 3. Similarly, the re-
action of 2 with one equivalent of di-
phenylacetylene in toluene afforded
the 1,2-disilacyclobutene 4, which con-
tains a pentacoordinate silicon center.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
iPr2C6H3). The formation of 5 can be
explained by an oxidative addition of
the divalent Si center in 2 with ArN3 to
afford a silaimine intermediate, which
then reacts with another molecule of
ArN3 to give compound 5. The reaction
of 2 with elemental sulfur in toluene
which
then
displaces
and “ClSi-
“DSi{(NtBu)2C(H)Ph}”
G
AHCTUNGERTG{NNUN (NtBu)2C(H)Ph}” to form 6 and 8, re-
spectively. Moreover, compound 8 was
synthesized by the reaction of [{PhC-
AHCTUNTGERG(NNUN NtBu)2}SiD]2 (10) with elemental seleni-
um in THF. The results show that the
reactions of 2 are initiated by oxidative
addition of the divalent silicon center,
and then the intermediate formed un-
dergoes a rearrangement involving the
diaminochlorosilyl substituent to form
compounds 3–8. These products have
been characterized by NMR spectros-
copy and X-ray crystallography.
afforded
[LSi(S)Cl] (6) and dithiodisiletane
[{Ph(H)C(NtBu)2}Si(m-S)]2 (7). Treat-
ment of 2 with elemental selenium in
the
chlorosilanethione
A
ACHTUNGTRENNUNG
Keywords: carbene homologues
·
chalcogens · N ligands · silicon ·
silylenes
Introduction
The chemistry of stable silylenes has attracted much atten-
tion in the past two decades and has been the focus of sever-
al reviews.[1] In 1994, West et al. reported the first example
of a stable N-heterocyclic silylene, A,[2] which contains a di-
coordinate SiII atom. Compound A is stable at room temper-
ature under anaerobic conditions because it benefits from
electronic stabilization by the amino substituents and steric
protection by the bulky substituents. After the isolation of
compound A, silylenes B–D were also synthesized and
structurally characterized.[3] Their reactions with a range of
organic, inorganic, and organometallic substrates were ex-
tensively investigated, which revealed that they usually un-
dergo insertion/oxidative addition to form silanes.[4] They
[a] S.-H. Zhang, H.-X. Yeong, Prof. Dr. C.-W. So
Division of Chemistry and Biological Chemistry
Nanyang Technological University
21 Nanyang Link, 637371 (Singapore)
Fax : (+65)6791-1961
E-mail: CWSo@ntu.edu.sg
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Chem. Eur. J. 2011, 17, 3490 – 3499

FULL PAPER
also serve as two-electron donors to transition metals and
lanthanides.[5] Recently, Roesky et al. reported the synthesis
and reactivity of stable amidinate-stabilized chlorosilylene F
and N-heterocyclic carbene-stabilized dichlorosilylene G,
both of which contain a three-coordinate SiII center.[6]
Driess and co-workers reported the synthesis of the stable
N-heterocyclic zwitterionic silylene H, which has an electro-
philic SiII center and a nucleophilic exocyclic methylene
group.[7] Because of the ylide-like character of H, its reactiv-
ity is remarkable and noticeably different from that of A–
D.[8] For example, it undergoes
remarkable roles of the bulky diaminochlorosilyl substituent
in these reactions are also described.
Results and Discussion
Reaction of 2 towards azobenzene and diphenylacetylene:
The reaction of [{PhCACHTNUTRGENN(UG NtBu)2}SiSi(Cl)CAHTUGNTRNEN{UGN (NtBu)2C(H)Ph}] (2)
with one equivalent of azobenzene in toluene afforded com-
pound 3 (Scheme 1), which is the first example of a 1,2-
1,4-addition with [HCAHTUNGRTEN(NNUG OEt2)2]-
[B(C6F5)4] and H2O·B(C6F5)3 to
A
ACHTUNGTRENNUNG
form a silyliumylidene and a
silaformamide–borane complex,
respectively.[8a,b] It inserts into a
[8l]
À
À
N H bond of ammonia, a P
P bond of white phosphorus,[8c]
[8j]
À
À
a S H bond of H2S, a Si Cl
Scheme 1. Synthesis of 3.
bond of halosilanes,[8h] and a C
À
H bond of acetylene.[8f] It has
also been used as a synthon for the preparation of a N-het-
erocyclic carbene-supported silanone[8e] and a Ni0–silylene
complex.[8d]
diaza-3,4-disilacyclobutane containing a pentacoordinate sil-
icon center. 1,2-Diaza-3,4-disilacyclobutanes are rare, with
compound
I derived from the [2+2] cycloaddition of
Silylsilylene is scarcely found and usually exists only as a
reactive intermediate. For example, Tokitoh et al. showed
Mes2Si=SiMes2 (Mes=C6H2-2,4,6-Me3) with azobenzene ap-
parently being the only reported example.[13] The formation
of 3 can be rationalized in terms of a [1+2] cycloaddition of
the divalent Si center in 2 with PhN=NPh to form a diazasi-
lacyclopropane intermediate, which then undergoes a 1,2-
chlorine shift to release the ring strain to form 3. There is
precedence for such [1+2] cycloaddition of stable silylenes
to unsaturated organic molecules. Thus, [1+2] cycloaddition
of compound H to diphenylacetylene affords a silacyclo-
prop-3-ene derivative.[8f] Compound F reacts with diphenyl-
acetylene to form a silacycloprop-3-ene intermediate, which
then inserts into another molecule of F to form the disilacy-
clobutene K, which contains two pentacoordinate silicon
centers.[6b]
that [(Bbt)BrSi=SiBr
4-{C(SiMe3)3}) underwent a 1,2-migration of a bromine
atom upon heating at 1008C in [D6]benzene for 10 h to form
the silylsilylene intermediate [{(Bbt)(Br)2Si}(Bbt)SiD]. The
ACHTUTNGERNNUG(Bbt)] (Bbt=C6H2-2,6-{CHACHTUGNTREN(NUGN SiMe3)2}2-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
À
low-valent silicon center then inserted into the C H bond of
the Bbt ligand to form a cyclized compound.[9] Sekiguchi
et al. demonstrated that the disilylsilylene [DSi
(SiMetBu2)2}2] was unstable and underwent a 1,2-silyl migra-
tion to form the disilene [{(tBu2MeSi)2MeSi}
(SiA)Si=Si(Me)-
(SiA)] (SiA =SitBuMe2).[10] West et al. showed that the stable
ACHTUNGTRNE{NUNG SiMe-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
diaminosilylene [DSi{N
(tBu)CH2CH2N
E
À
the Si N bond of another diaminosilylene molecule to form
an intermediate aminosilylsilylene, which further dimerized
to form a diaminodisilyldisilene.[11] Recently, we successfully
synthesized and characterized amidinate-stabilized silylsily-
Compound 3 was isolated as a highly air- and moisture-
sensitive colorless crystalline solid in 19% yield. It is soluble
lenes [{PhCACHTUNGTRENNUNG(NtBu)2}SiSiRCAHTUNGTNER{NUGN (NtBu)2C(H)Ph}] (R=H (1), Cl
(2)).[12] To the best of our knowledge, little is known regard-
ing the reactivity of stable silylsilylenes. Hence, in this
paper, we report the reactivity of [{PhC
{(NtBu)2C(H)Ph}] (2) towards diphenylacetylene, azoben-
zene, 2,6-diisopropylphenyl azide, sulfur, and selenium. The
ACHTUNGTERN(NUNG NtBu)2}SiSiCl-
ACHTUNGTRENNUNG
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3491

C.-W. So et al.
in toluene and hexane. It is stable in solution or the solid
state at room temperature in an inert atmosphere. It has
been characterized by elemental analysis and spectroscopic
try about the Si1 atom is distorted tetrahedral. As a result,
À
the Si2 N5 bond (1.880(5) ꢁ) is significantly longer than
À
the Si1 N6 bond (1.754(5) ꢁ) due to the differences in ge-
1
methods. The H and 13C NMR spectra of 3 display resonan-
ometry and coordination number between the Si1 and Si2
À
ces due to the amidinate, amido, and phenyl substituents on
the SiNNSi four-membered ring. The H NMR spectrum of
atoms. The Si1 N6 bond length (1.754(5) ꢁ) is comparable
1
to those in
I
(1.792(5), 1.797(6) ꢁ).[13] The Si1 Si2
À
À
3
shows
a
singlet at d=5.57 ppm attributable to the
(2.340(2) ꢁ) and N5 N6 (1.446(6) ꢁ) bond lengths are com-
parable with those of typical Si Si (2.34 ꢁ) and N N
(1.45 ꢁ) single bonds, respectively. The Si2 N1 bond
(1.968(5) ꢁ) is significantly longer than the Si2 N2 bond
(1.818(5) ꢁ). It is suggested that the axial N1 atom forms a
dative bond to the Si2 atom, whereas the equatorial N2
atom is s-bonded to the Si2 atom. A similar conformation
À
À
NC(H)N proton of the amido ligand. It also shows four sin-
glets at d=1.14, 1.22, 1.23, and 1.24 ppm, corresponding to
four non-equivalent tBu groups. The 29Si NMR spectrum of
3 features two singlets at d=À17.4 and À80.4 ppm attribut-
able to the four-coordinate and five-coordinate silicon cen-
ters, respectively. The 29Si NMR resonances of 3 lie between
those of the three-coordinate silicon in F (d=14.6 ppm) and
À
À
À
can be found in [(C5H3N-6-Me-2-NSiMe3)SiCl3] (Si
equatorial: 1.773(3) ꢁ, Si Naxial: 1.870(2) ꢁ).[14]
À
the five-coordinate silicon in [{PhC
G
N
À96.6 ppm).[6a] The 29Si NMR signals of 3 also show an up-
The reaction of 2 with one equivalent of diphenylacetyl-
ene in toluene afforded the 1,2-disilacyclobutene
(Scheme 2), which contains a pentacoordinate silicon center.
field shift compared with that of compound
10.7 ppm).[13]
4
The molecular structure of 3 is shown in Figure 1. The
four-membered Si1-Si2-N5-N6 ring is puckered, with the N6
atom being displaced from the Si1-Si2-N5 least-squares
plane by 0.486 ꢁ. The phenyl substituents on the Si1-Si2-
N5-N6 ring adopt a trans conformation to minimize the re-
pulsion of the phenyl rings and the lone pair electrons on
the nitrogen atoms. The amidinate ligand is bonded in a
N,N’-chelate fashion to the Si2 atom, which displays a dis-
torted trigonal-bipyramidal geometry with the N1 and N5
atoms in the axial positions. On the other hand, the geome-
Scheme 2. Synthesis of 4.
Similar 1,2-disilacyclobutenes J and K, containing one or
two pentacoordinate silicon centers, have been synthesized
and structurally characterized.[6b,15] Similar to the formation
of 3, the reaction appears to proceed through a [1+2] cyclo-
addition and 1,2-chlorine shift to give 4.
Compound 4 was isolated as a highly air- and moisture-
sensitive colorless crystalline solid in 44% yield. It is soluble
in toluene and THF. It is stable in solution or the solid state
1
at room temperature in an inert atmosphere. The H NMR
spectrum of 4 at room temperature shows a broad singlet
for the tBu groups, which is inconsistent with the solid-state
structure. In this regard, the 1H NMR spectrum of 4 was
also acquired at À608C, whereupon four singlets were re-
solved at d=0.74, 0.86, 1.19, and 1.32 ppm for the four non-
equivalent tBu groups. The results suggest that the amidi-
nate ligand may be fluxional in solution at room tempera-
ture. The 29Si NMR spectrum of 4 at room temperature fea-
tures two singlets at d=26.4 and À52.8 ppm attributable to
the four-coordinate and five-coordinate silicon centers, re-
spectively. The 29Si NMR signals show downfield shifts com-
Figure 1. Molecular structure of 3 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms are omitted for clarity except the H32
À
À
atom. Selected bond lengths [ꢁ] and angles [8]: Si1 Si2 2.340(2), Si1 N6
pared with those in compounds
3
and
K
(d=
À
À
À
À
1.754(5), Si2 N5 1.880(5), Si2 Cl1 2.109(2), N5 N6 1.446(6), Si1 N3
À109.5 ppm).[6b] The 29Si NMR resonance of the four-coordi-
nate silicon center is comparable with those in compound L
(d=13.0, 22.6 ppm).[4e]
À
À
À
1.708(5), Si1 N4 1.716(5), N3 C32 1.495(7), N4 C32 1.482(7), Si2-N1
À
À
À
1.968(5), Si2 N2 1.818(5), C5 N1 1.308(7), C5 N2 1.368(7); Si1-Si2-N5
73.2(2), Si2-N5-N6 99.0(3), N5-N6-Si1 104.8(3), N6-Si1-Si2 75.3(2), Si1-
Si2-Cl1 127.0(1), N5-Si2-Cl1 98.4(2), Si2-N1-C5 90.1(4), N1-C5-N2
106.2(5), C5-N2-Si2 94.8(2), N1-Si2-N2 68.7(2), N3-Si1-N4 79.5(2), Si1-
N3-C32 92.8(3), N3-C32-N4 94.6(4), C32-N4-Si1 93.0(3), N3-Si1-Si2
137.8(2), N1-Si2-Si1 104.3(2).
The molecular structure of 4 is shown in Figure 2. The
four-membered Si1-Si2-C23-C16 ring is almost planar. The
amidinate ligand is bonded in a N,N’-chelate fashion to the
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Chem. Eur. J. 2011, 17, 3490 – 3499

Reactions of a Silylsilylene Derivative
FULL PAPER
NAr)N(Ar)L’]
(5,
L=PhC
G
L’=Si(Cl)-
AHCTUNGTRENNUNG
West et al. and Lappert et al. reported that the reactions of
A or BI with one equivalent of RN3 (R=1-adamantyl,
SiMe3, Ph, or p-tolyl) proceed through a silaimine inter-
mediate, which then undergoes a [2+3] cycloaddition with
another molecule of RN3 to form the corresponding silate-
trazolines in high yield.[3c,4i,x] It is interesting that 2 reacted
with excess ArN3 (1.6 equivalents) to afford compound 5
rather than a silatetrazoline. With reference to the reactions
of A or BI with azides, the formation of 5 can be rational-
ized in terms of an oxidative addition of the divalent Si
center in 2 with ArN3 to afford a silaimine intermediate,
which then undergoes a [2+3] cycloaddition with another
molecule of ArN3 to form a silatetrazoline intermediate.
Due to the steric congestion between the silatetrazoline ring
and the amidinate ligand, the silatetrazoline intermediate
undergoes a 1,2-silyl shift with the elimination of a N2 mole-
cule to give compound 5. Another possible explanation is
that the silaimine intermediate undergoes a nitrene insertion
reaction to form 5. Compounds containing a Si=N double
Figure 2. Molecular structure of 4 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms are omitted for clarity except the H30
À
À
atom. Selected bond lengths [ꢁ] and angles [8]: Si1 Si2 2.3646(8), Si1
À
À
À
C16 1.972(2), Si1 Cl1 2.1368(8), Si2 C23 1.869(2), C16 C23 1.365(3),
À
À
À
À
À
Si1 N1 1.827(2), Si1 N2 2.004(2), C1 N1 1.369(3), C1 N2 1.303(3), Si2
bond are rare. To date, only [{tBuNCH=CHN
ACHTUNGTRENNUNG(tBu)}-
À
N3 1.734(2), Si2 N4 1.720(2); Si2-Si1-C16 72.52(7), Si1-C16-C23
A
ACHTUNGTRENNUNG
104.72(15), C16-C23-Si2 105.00(15), C23-Si2-Si1 77.16(7), Si2-Si1-Cl1
118.86(3), C16-Si1-Cl1 96.84(6), N1-Si1-N2 68.10(8), Si1-N1-C1 95.24(13),
N1-C1-N2 107.13(18), C1-N2-Si1 89.50(13), N3-Si2-N4 78.31(8), Si2-N3-
C30 93.40(13), N3-C30-N4 94.46(15), C30-N4-Si2 93.75(12), N3-Si2-Si1
135.82(7), N2-Si1-Si2 106.46(6).
NR] (R=CH2Ph, Ph, 1-adamantyl, SiMe3) have been syn-
thesized and structurally characterized by X-ray crystallog-
raphy.[4t,z]
Compound 5 was isolated as a highly air- and moisture-
sensitive colorless crystalline solid in low yield (9.5%). It is
soluble in toluene and hexane. It is stable in solution or the
solid state at room temperature in an inert atmosphere. The
1H and 13C NMR spectra of 5 display resonances due to the
amidinate, amido, and Ar substituents. The 29Si NMR spec-
trum of 5 features two singlets at d=À47.8 and À87.3 ppm
attributable to two non-equivalent silicon centers.
Si1 atom, which displays a distorted trigonal-bipyramidal ge-
ometry with the C16 and N2 atoms in the axial positions.
On the other hand, the geometry about the Si2 atom is dis-
À
À
torted tetrahedral. The Si1 C16 (1.972(2) ꢁ) and Si2 C23
(1.869(2) ꢁ) bond lengths are similar to those in compound
J (four-coordinate silicon: 1.891(3) ꢁ; five-coordinate sili-
The molecular structure of 5 is shown in Figure 3. The
amidinate ligand is bonded in a N,N’-chelate fashion to the
con: 1.932(3) ꢁ).[15] The Si1 Si2 (2.3646(8) ꢁ) and C16 C23
(1.365(3) ꢁ) bond lengths are comparable to those of a typi-
À
À
À
Si2 atom, which displays a tetrahedral geometry. The Si2
À
À
cal Si Si single bond (2.34 ꢁ) and a C=C double bond, re-
N4 (1.589(5) ꢁ) and Si2 N3 (1.795(4) ꢁ) bond lengths are
À
spectively. The Si1 N2 bond
(2.004(2) ꢁ) is significantly
À
longer than the Si1 N1 bond
(1.827(2) ꢁ). Similar to the sit-
uation in compound 3, the axial
N2 atom forms a dative bond to
the Si1 atom, whereas the equa-
torial N1 atom is s-bonded to
À
the Si1 atom. The long Si1 N2
bond length indicates that the
amidinate ligand may be fluxio-
nal in solution, as suggested by
1
the H NMR spectrum of 4.
Reaction of 2 with 2,6-diisopro-
pylphenylazide: The reaction of
2 with 1.6 equivalents of 2,6-dii-
sopropylphenylazide in toluene
afforded the silaimine [LSiACTHUNTGRNEUNG(= Scheme 3. Synthesis of 5 and proposed mechanism via the silatetrazoline intermediate.
Chem. Eur. J. 2011, 17, 3490 – 3499
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3493

C.-W. So et al.
the divalent Si center in 2 with sulfur to afford a silylsilane-
thione intermediate, which then undergoes a 1,2-chlorine
shift with the displacement of an [DSiACTHNUTRGNEN{UG (NtBu)2C(H)Ph}] inter-
mediate to afford 6 (Scheme 5). The silylene intermediate
reacts with elemental sulfur to form compound 7. Stable si-
lanechalcogenones M–Q and dithiodisiletanes R are known,
which can be synthesized by reactions of elemental chalco-
gens with silanes or with the corresponding silylenes, respec-
tively.[4q,y,8o,16]
A mixture of 6 and 7 was isolated as a highly air- and
moisture-sensitive colorless crystalline solid, which was
found to be soluble in toluene and CH2Cl2. It is stable in so-
lution or the solid state at room temperature in an inert at-
mosphere. Pure compound 6 was synthesized in 46% yield
by the reaction of [{PhCACTHNUTRGNE(UGN NtBu)2}SiCl] (9) with elemental
sulfur in toluene (Scheme 6). With pure 6 at hand, the sig-
1
nals of the H, 13C, and 29Si NMR spectra of the mixture of 6
and 7 could be assigned. The 29Si NMR spectrum of the mix-
ture features two singlets at d=À17.5 and À41.4 ppm for 6
and 7, respectively. The 29Si NMR resonance of 6 is compa-
Figure 3. Molecular structure of 5 with thermal ellipsoids at the 30%
probability level. Hydrogen atoms are omitted for clarity except the H5
À
À
atom. Selected bond lengths [ꢁ] and angles [8]: Si2 N3 1.795(4), Si2 N4
À
À
À
À
1.589(5), Si2 N5 1.867(5), Si2 N6 1.888(4), C44 N5 1.330(7), C44 N6
rable with those of [{PhC
ACHTUNGTRENNUNG
À
À
À
À
1.337(7), Si1 Cl1 2.076(2), Si1 N3 1.740(4), Si1 N1 1.726(4), Si1 N2
1.57 ppm),[17]
PI
(d=À34.9 ppm),
À
À
1.734(5), C5 N1 1.498(7), C5 N2 1.500(7); N3-Si2-N4 114.7(2), N4-Si2-
N5 118.9(2), N3-Si2-N5 113.2(2), N5-Si2-N6 70.4(2), Si2-N5-C44 90.9(3),
N5-C44-N6 108.5(5), C44-N6-Si2 89.9(3), N3-Si1-Cl1 105.1(2), N3-Si1-N1
122.2(2), N1-Si1-Cl1 112.8(2), N1-Si1-N2 81.4(2), Si1-N1-C5 90.6(3), N1-
C5-N2 97.7(4), C5-N2-Si1 90.2(3), Si1-N3-Si2 131.5(3).
À33.5 ppm).[8o] The 29Si NMR signal of 7 is similar to those
of RI (d=À45.3 ppm) and RII (d=À38.8 ppm).[4y,18]
The molecular structures of 6 and 7 are shown in Fig-
ures 4 and 5, respectively. The S and Cl atoms are seen to
be disordered in the X-ray crystal structure of 6. The disor-
comparable to those of the Si=
N double bond (1.599(4) ꢁ) and
À
Si N single bonds (1.735(3),
1.736(3) ꢁ)
in
[{tBuNCH=
CHN
(tBu)}
U
Reactions of 2 with chalcogens:
Reactions of 2 with one or two
equivalents of elemental sulfur
afforded the chlorosilanethione
6 and dithiodisiletane 7 in a
ratio of 2:1 (Scheme 4), which
was confirmed by NMR spec-
troscopy. These products were
characterized by X-ray crystal-
lography. An attempt to isolate
pure 6 or 7 by recrystallization
failed. The reaction proceeds
through an oxidative addition of
dered atoms have been omitted for clarity in Figure 4. Com-
pound 6 is monomeric. The amidinate ligand is bonded in a
N,N’-chelate fashion to the Si1 atom, which displays a tetra-
À
hedral geometry. The Si1 S1 bond (2.079(6) ꢁ) in 6 is
slightly longer than that in [{PhC
N
(1.984(8) ꢁ),[17] but it is similar to those in
M
(2.013(3) ꢁ)[16a] and PI (2.006(1) ꢁ).[8o] The results show
À
that the Si1 S1 bond could have double-bond character or
À
Scheme 4. Synthesis of 6 and 7.
zwitterionic Si+ S bonding character.
À
3494
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ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 3490 – 3499

Reactions of a Silylsilylene Derivative
FULL PAPER
in 2 with selenium to afford a
silylsilaneselone intermediate,
which then displaces the diami-
nochlorosilyl substituent “ClSi-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Scheme 5. Proposed mechanism for the formation of 6 and 7.
Scheme 6. Synthesis of 6 from [{PhCACTHNUTRGEN(UNG NtBu)2}SiCl] (9).
Figure 5. Molecular structure of 7 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms are omitted for clarity except the H5
À
À
atom. Selected bond lengths [ꢁ] and angles [8]: Si1 S1 2.1471(5), Si1
À
À
À
S1A 2.1399(5), Si1 N1 1.7057(13), Si1 N2 1.7061(13), C5 N1 1.480(2),
À
C5 N2 1.483(2); Si1-S1-Si1A 84.58(2), S1-Si1-S1A 95.42(2), S1-Si1-N1
120.52(5), S1-Si1-N2 121.66(5), N1-Si1-N2 79.79(6), Si1-N1-C5 92.38(9),
N1-C5-N2 95.23(10), C5-N2-Si1 92.24(9).
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Figure 4. Molecular structure of 6 with thermal ellipsoids at the 50%
probability level. Hydrogen atoms are omitted for clarity. Selected bond
do not dimerize to form dichalcogenadisiletanes, but rear-
range to form 6 and 8, respectively.
Compound 8 was also synthesized in 10% yield by the re-
À
À
À
lengths [ꢁ] and angles [8]: Si1 S1 2.079(6), Si1 Cl1A 1.940(5), Si1 N1
À
1.808(2), C1 N1 1.337(2); S1-Si1-Cl1A 117.19(8), S1-Si1-N1 118.78(16),
action of [{PhCACTHNUTRGNEUNG(NtBu)2}SiD]2 (10) with two equivalents of ele-
Cl1A-Si1-N1 111.14(16), N1-Si1-N1A 72.85(10), Si1-N1-C1 90.13(13),
N1-C1-N1A 106.9(2).
mental selenium in THF (Scheme 8). The results show that
the SiI atoms in 10 undergo oxidative addition with selenium
to form compound 8. Recently, Roesky et al. suggested that
the reaction of 10 with N2O proceeds through an [LSi-O-
Compound 7 is a centrosymmetric spirocyclic dimer
(Figure 5). The Si1-S1-Si1A-S1A ring is planar and almost
perpendicular to the Si1-N1-C5-
N2 ring (dihedral angle: 88.88).
À
The
2.1471(5) ꢁ)
Si S
(2.1399(5),
À
and
Si N
(1.7057(13), 1.7061(13) ꢁ) bond
lengths are similar to those in
À
À
RII (Si S: average 2.134 ꢁ; Si
N: average 1.719 ꢁ).[18]
The reaction of 2 with one
equivalent of elemental seleni-
um in THF afforded the di(sila-
Scheme 7. Synthesis of 8 from 2.
neselone)
8
in 24% yield,
which was confirmed by NMR
spectroscopy and X-ray crystal-
lography (Scheme 7). It is sug-
gested that the reaction pro-
ceeds through an oxidative ad-
dition of the divalent Si center Scheme 8. Synthesis of 8 from 10.
Chem. Eur. J. 2011, 17, 3490 – 3499
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3495

C.-W. So et al.
SiL] (L=PhC
G
Conclusion
I
Si(O)L]. In contrast, selenium does not insert into the Si
SiI bond of 10.[19]
Novel 1,2-diaza-3,4-disilacyclobutane 3, which contains a
Compound 8 was isolated as a highly air- and moisture-
sensitive colorless crystalline solid, and proved to be soluble
in THF and dichloromethane. It is stable in the solid state at
room temperature under an inert atmosphere. Compound 8
has been characterized by elemental analysis, spectroscopic
five-coordinate silicon center, has been synthesized by the
reaction of [{PhCACHTNUTRGENNUG(NtBu)2}SiSi(Cl)ACHTUNGTRNEN{NGU (NtBu)2C(H)Ph}] (2) with
one equivalent of azobenzene. Similarly, the 1,2-disilacyclo-
butene 4 with a pentacoordinate silicon center was afforded
by the reaction of 2 with one equivalent of diphenylacety-
lene. Compound 2 reacted with ArN3 (Ar=2,6-iPr2C6H3) to
1
methods, and X-ray crystallography. The H and 13C NMR
spectra of 8 display resonances due to the amidinate ligand.
The 29Si NMR spectrum of 8 features one singlet at d=
10.4 ppm, which lies between the signals of four-coordinate
silaneselones (PIII: d=À33.3 ppm; Q: d=À30.3 ppm)[8o,16c]
give the silaimine [LSi
ACHTUGTNRENN(GU =NAr)N(Ar)L’] (5, L=PhCACHTUNGTRENNUNG(NtBu)2,
L’=Si(Cl){(NtBu)2C(H)Ph}), which contains a Si=N double
AHCTUNGTRENNUNG
bond. The results show that the reactions of 2 are initiated
by oxidative addition of the divalent silicon center, and then
the intermediate formed undergoes a rearrangement involv-
ing the diaminochlorosilyl substituent. The reaction of 2
with one or two equivalents of elemental sulfur afforded the
chlorosilanethione [LSi(S)Cl] (6) and the dithiodisiletane
[{Ph(H)CACHTNUTRGENN(UG NtBu)2}SiACHTUGNTREN(NUGN m-S)]2 (7). The results show that the re-
action proceeds through a silylsilanethione intermediate,
which then undergoes a 1,2-chlorine shift with displacement
and
a
three-coordinate dialkylsilaneselone (OII: d=
227.7 ppm).[4q] The 77Se NMR spectrum of 8 shows a singlet
at d=À322.9 ppm, which is comparable to those of com-
pounds PIII (d=À374.4 ppm) and Q (d=À344 ppm).[8o,16c]
The molecular structure of 8, along with the atom num-
bering scheme, is shown in Figure 6. The amidinate ligands
are bonded in a N,N’-chelate fashion to the silicon centers,
of the [DSi
ACHTUNGTERNUN{NG (NtBu)2C(H)Ph}] intermediate to afford 6. The
[DSi{(NtBu)2C(H)Ph}] intermediate then reacts with sulfur to
AHCTUNGTRENNUNG
form 7. A novel di(silaneselone) [LSi(Se)Si(Se)L] (8) has
also been synthesized by the reaction of 2 with one equiva-
lent of selenium or by the reaction of [{PhCACTHNUGTRNEUNG(NtBu)2}SiD]2
(10) with two equivalents of selenium. The results demon-
strate that the diaminochlorosilyl substituent in 2 can serve
as a leaving group in these reactions.
Experimental Section
General procedures: All manipulations were carried out under an inert
atmosphere of argon using standard Schlenk techniques. Toluene, THF,
and hexane were dried over and distilled over Na/K alloy prior to use.
CH2Cl2 was dried over and distilled over CaH2 prior to use. 2, 9, and 10
were prepared as described in the literature.[6a,12,20] 1H, 13C, 29Si, and
77Se NMR spectra were recorded on a JEOL ECA 400 spectrometer.
Figure 6. Molecular structure of 8 with thermal ellipsoids at the 50%
À
probability level. Selected bond lengths [ꢁ] and angles [8]: Si1 Se1
À
À
À
À
2.1346(16), Si1 N1 1.828(4), Si1 N2 1.830(4), C5 N1 1.339(7), C5 N2
1
Chemical shifts d are relative to SiMe4 for H, 13C, and 29Si; and to Ph2Se
À
1.333(6), Si1 Si1A 2.384(3); N1-Si1-N2 71.61(19), N1-Si1-Se1 118.58(16),
for 77Se. Elemental analyses were performed at the Division of Chemistry
and Biological Chemistry, Nanyang Technological University. Melting
points were measured in sealed glass tubes and were not corrected.
N2-Si1-Se1 117.60(16), Si1A-Si1-Se1 117.89(8), C5-N1-Si1 90.9(3), N2-
C5-N1 106.5(4), C5-N2-Si1 91.0(3), Si1A-Si1-N1 109.95(17).
Synthesis of 3: A solution of azobenzene (0.12 g, 0.64 mmol) in toluene
(10 mL) was added dropwise to 2 (0.31 g, 0.55 mmol) in toluene (15 mL)
at room temperature. The reaction mixture was stirred for 3 h. Volatiles
were removed in vacuo and the orange residue was extracted with
hexane. The orange solution was filtered and concentrated to afford 3 as
colorless crystals. Yield: 0.076 g (19%). M.p. 179.18C; 1H NMR
(395.9 MHz, [D6]benzene, 21.48C): d=1.14 (s, 9H; tBu), 1.22 (s, 9H;
tBu), 1.23 (s, 9H; tBu), 1.24 (s, 9H; tBu), 5.57 (s, 1H; NC(H)N), 6.80–
6.87 (t, 1H; Ph), 6.86–6.93 (m, 5H; Ph), 7.16–7.26 (m, 6H; Ph), 7.32 (t,
2H; Ph), 7.41–7.45 (m, 1H; Ph), 7.57 (brs, 2H; Ph), 7.80–7.81 (m, 2H;
Ph), 8.54–8.56 ppm (m, 1H; Ph); 13C{1H} NMR (100.5 MHz, [D6]benzene,
22.08C): d=30.9 (CMe3), 31.2 (CMe3), 31.9 (CMe3), 32.9 (CMe3), 50.36
(CMe3), 50.42 (CMe3), 54.2 (CMe3), 55.7 (CMe3), 77.2 (NC(H)N), 116.6,
118.5, 118.7, 128.1, 128.3, 128.4, 128.45, 128.5, 129.4, 129.5, 133.6, 145.5,
146.4, 148.1 (Ph), 169.5 ppm (NCN); 29Si{1H} NMR (79.4 MHz,
[D6]benzene, 22.18C): d=À17.4, À80.4 ppm; elemental analysis calcd
(%) for C42H57ClN6Si2: C 68.40, H 7.80, N 11.40; found: C 68.27, H 7.56,
N 11.31.
À
which display a distorted tetrahedral geometry. The Si1 Se1
bond length (2.1346(16) ꢁ) in 8 is comparable to those in
base-stabilized silaneselones (PIII: 2.1457(9) ꢁ; Q: 2.153(1),
2.156(1) ꢁ),[8o,16c] but it is longer than that in dialkylsilanese-
lone OII (2.0963(5) ꢁ).[4q] The Si1 Se1 bond is significantly
shorter than an average Si Se single bond (2.27 ꢁ). The
À
À
À
Si1 Si1A bond length (2.384(3) ꢁ) is comparable to that in
10 (2.413(2) ꢁ).[20] The C N bond lengths (C5 N1:
À
À
À
1.339(7) ꢁ, C5 N2: 1.333(6) ꢁ) are approximately inter-
À
mediate between the C=N double-bond and C N
N
single-bond lengths. This geometry favors considerable elec-
tron delocalization throughout the NCN backbone of the
ligand.
Crystal data for 3: [C42H57ClN6Si2]; M=737.57; monoclinic; space group
P21/c; a=18.227(3), b=11.138(2), c=20.935(3) ꢁ; b=100.504(9)8; V=
3496
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ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 3490 – 3499

Reactions of a Silylsilylene Derivative
FULL PAPER
4178.9(11) ꢁ3; Z=4; 1calcd =1.172 mgmÀ3; 37687 measured reflections;
7398 independent reflections; 472 refined parameters; R1 =0.0778, wR2 =
0.1648 (I>2s(I)).
colorless crystals. Method B: A solution of S8 (0.042 g, 0.16 mmol) in tol-
uene (10 mL) was added dropwise to 2 (0.27 g, 0.48 mmol) in toluene
(15 mL) at room temperature. The reaction mixture was stirred at room
temperature for 3 h and filtered. After concentration, a mixture of 6 and
7 was obtained as colorless needle-like crystals. X-ray quality crystals of
7 were grown from dichloromethane/toluene. By reference to the NMR
spectrum of 6 synthesized by the reaction of 9 with sulfur, the NMR reso-
nances of 7 could be identified. 1H NMR of 7 (399.5 MHz, [D6]benzene,
21.98C): d=1.23 (s, 36H; tBu), 5.40 (s, 2H; NC(H)N), 6.96–7.14 ppm (m,
10H; Ph); 13C{1H} NMR (100.5 MHz, [D6]benzene, 21.48C): d=30.6
(CMe3), 51.6 (CMe3), 75.5 (NC(H)N), 128.4, 146.4, 154.2 ppm (Ph);
29Si{1H} NMR (79.4 MHz, [D6]benzene, 21.98C): d=À41.4 ppm. An at-
tempt to isolate pure 7 by recrystallization failed. Therefore, the chemical
yield, melting point, and elemental analysis of 7 could not be obtained.
Synthesis of 4: Toluene (10 mL) was added to a mixture of 2 (0.28 g,
0.51 mmol) and diphenylacetylene (0.010 g, 0.56 mmol) at room tempera-
ture. The reaction mixture was stirred for 3 h and then filtered. The re-
sulting orange solution was concentrated to afford 4 as colorless crystals.
Yield: 0.17 g (44%). M.p. 231.68C; 1H NMR (399.5 MHz, [D6]benzene,
21.68C): d=1.19 (brs, 36H; tBu), 5.68 (s, 1H; NC(H)N), 6.70–7.85 ppm
(m, 20H; Ph); 13C{1H} NMR (100.5 MHz, [D6]benzene, 258C): d=32.3
(CMe3), 32.8 (CMe3), 50.8 (CMe3), 54.9 (CMe3), 80.1 (NC(H)N), 125.9,
126.0, 126.3, 127.8, 128.9, 129.0, 129.1, 129.3, 129.7, 130.7, 132.3, 135.0,
143.6, 144.7, 147.1 (Ph), 167.6, 173.5 (C=C), 193.8 ppm (NCN);
29Si{1H} NMR (78.7 MHz, [D6]benzene, 21.98C): d=26.4, À52.8 ppm;
1H NMR (395.9 MHz, [D8]THF, À608C): d=0.74 (s, 9H; tBu), 0.86 (s,
9H; tBu), 1.19 (s, 9H; tBu), 1.32 (s, 9H; tBu), 5.54 (s, 1H; NC(H)N),
6.90–7.72 ppm (m, 20H; Ph); elemental analysis calcd (%) for
C44H57ClN4Si2: C 72.05, H 7.84, N 7.64; found: C 71.82, H 7.96, N 7.76.
Crystal data for 6: [C15H23ClN2SSi]; M=326.95; monoclinic; space group
C2/c; a=14.4427(9), b=10.9192(7), c=12.7686(8) ꢁ; b=117.510(3)8, V=
1785.96(19) ꢁ3; Z=4; 1calcd =1.216 mgmÀ3; 11878 measured reflections;
2847 independent reflections; 105 refined parameters; R1 =0.0573, wR2 =
0.1505 (I>2s(I)).
Crystal data for 4: [C47.5H61ClN4Si2]; M=779.63; monoclinic; space group
C2/c; a=38.9898(12), b=9.7439(3), c=25.3286(8) ꢁ; b=114.058(2)8; V=
¯
Crystal data for 7: [C30H48N4S2Si2]; M=585.02; triclinic; space group P1;
8786.8(5) ꢁ3; Z=8; 1calcd =1.179 mgmÀ3
; 13413 measured reflections;
a=6.3048(3), b=10.7046(4), c=12.1115(5) ꢁ; a=78.643(3), b=
85.360(2), g=88.261(2)8; V=798.69(6) ꢁ3; Z=1; 1calcd =1.216 mgmÀ3
;
13413 independent reflections; 537 refined parameters; R1 =0.0562,
wR2 =0.1300 (I>2s(I)).
20073 measured reflections; 7027 independent reflections; 178 refined
parameters; R1 =0.0489, wR2 =0.1190 (I>2s(I)).
Synthesis of 5:
0.79 mmol) in toluene (10 mL) was added dropwise to
A
solution of 2,6-diisopropylphenylazide (0.16 g,
(0.28 g,
Synthesis of 8: Method A: A solution of 2 (0.27 g, 0.49 mmol) in THF
(15 mL) was added dropwise at room temperature to a suspension of Se
(0.046 g, 0.58 mmol) in THF (10 mL). The reaction mixture was stirred
for 13 h and then filtered. Dichloromethane was added to the resulting
orange solution. After concentration, 8 was obtained as colorless crystals
(0.040 g, 24%). Method B: A solution of 10 (0.18 g, 0.34 mmol) in THF
(16 mL) was added to a stirred suspension of Se (0.058 g, 0.73 mmol) in
THF (2 mL) at À788C. The reaction mixture was warmed to room tem-
perature and stirred for a further 12 h. The insoluble precipitate was fil-
tered off, and the pale-yellow filtrate was concentrated to yield colorless
crystals of 8. Yield: 0.023 g (10%). M.p. 288.88C; 1H NMR (395.9 MHz,
CD2Cl2, 258C): d=1.39 (s, 36H; tBu), 7.32–7.58 ppm (m, 10H; Ph);
13C{1H} NMR (100.5 MHz, CD2Cl2, 258C): d=32.2 (CMe3), 56.5 (CMe3),
128.1, 128.7, 129.0, 129.1, 131.2, 131.5 (Ph), 175.2 ppm (NCN);
29Si{1H} NMR (79.4 MHz, CD2Cl2, 21.78C): d=10.4 ppm; 77Se{1H} NMR
(76.2 MHz, CD2Cl2, 21.78C): d=À322.9 ppm; elemental analysis calcd
(%) for C30H46N4Se2Si2: C 53.24, H 6.86, N 8.28; found: C 53.13, H 6.77,
N 8.25.
2
0.50 mmol) in toluene (15 mL) at room temperature. The resulting mix-
ture was stirred at room temperature for 3 h. Volatiles were then re-
moved under reduced pressure and the solid was extracted with hexane
(25 mL). The resulting orange-brown solution was filtered and concen-
trated to give 5 as colorless crystals. Yield: 0.043 g (9.5%). M.p. 203.58C;
1H NMR (399.5 MHz, [D6]benzene, 21.78C): d=1.25 (d, 12H; CHMe2),
1.29 (s, 18H; tBu), 1.32 (s, 18H; tBu), 1.35 (d, 6H; CHMe2), 1.47 (d, 6H;
CHMe2), 3.18–3.26 (sept, 2H; CHMe2), 3.85–3.91 (sept, 2H; CHMe2),
5.02 (s, 1H; NC(H)N), 6.41 (brs, 2H; Ph), 6.93–7.03 (m, 7H; Ph), 7.24
(d, 2H; Ph), 7.32–7.35 (m, 3H; Ph), 7.59 (d, 1H; Ph), 7.75–7.77 ppm (m,
1H; Ph); 13C{1H} NMR (100.5 MHz, [D6]benzene, 22.18C): d=26.7
(CHMe2), 27.5 (CHMe2), 28.5 (CHMe2), 28.6 (CHMe2), 29.4 (CHMe2),
30.9 (CMe3), 32.4 (CMe3), 54.4 (CMe3), 55.5 (CMe3), 72.6 (NC(H)N),
117.0, 122.7, 127.2, 127.4, 127.6, 127.9, 129.2, 129.4, 130.3, 130.9, 131.6,
138.7, 142.0, 146.9, 147.7, 148.8 (Ph), 178.4 ppm (NCN); 29Si{1H} NMR
(79.4 MHz, [D6]benzene, 21.98C): d=À47.8, À87.3 ppm; elemental anal-
ysis calcd (%) for C54H81ClN6Si2: C 71.60, H 9.02, N 9.28; found: C 71.45,
H 8.72, N 9.03.
Crystal data for 8: [C30H46N4Se2Si2]; M=676.81; monoclinic; space group
C2/c; a=25.812(6), b=9.040(2), c=17.857(4) ꢁ; b=127.016(7); V=
3327.2(14) ꢁ3; Z=4; 1calcd =1.351 mgmÀ3; 17457 measured reflections;
3384 independent reflections; 178 refined parameters; R1 =0.0545, wR2 =
0.1040 (I>2s(I)).
Crystal data for 5: [C54H81ClN6Si2]; M=905.88; orthorhombic; space
group P2(1)2(1)2(1); a=12.6584(12), b=17.9506(17), c=22.629(2) ꢁ;
V=5142.0(8) ꢁ3; Z=4; 1calcd =1.170 mgmÀ3; 59349 measured reflections;
14966 independent reflections; 588 refined parameters; R1 =0.0847,
wR2 =0.1497 (I>2s(I)).
X-ray data collection and structural refinement: Intensity data for com-
pounds 3–8 were collected using a Bruker APEX II diffractometer. The
crystals of 3–8 were measured at 103(2) K. The structures were solved by
direct phase determination (SHELXS-97) and refined for all data by full-
matrix least-squares methods on F2.[21] All non-hydrogen atoms were sub-
jected to anisotropic refinement. The hydrogen atoms were generated
geometrically and allowed to ride on their respective parent atoms; they
were assigned appropriate isotopic thermal parameters and included in
the structure-factor calculations.
Synthesis of 6 from [{PhC
ACHTUNGTRENNUNG
0.15 mmol) in toluene (10 mL) was added dropwise to
9
0.99 mmol) in toluene (10 mL) at room temperature. The resulting
yellow solution was stirred at room temperature overnight. It was then
filtered and concentrated to give 6 as colorless crystals. X-ray quality
crystals were grown from a dichloromethane/toluene mixture. Yield:
1
0.15 g (46%). M.p. 231.68C; H NMR (395.9 MHz, [D6]benzene, 21.28C):
d=1.11 (s, 18H; tBu), 6.61–6.63 (m, 1H; Ph), 6.73–6.77 (m, 3H; Ph),
6.84–6.86 ppm (m, 1H; Ph); 13C{1H} NMR (99.5 MHz, [D6]benzene,
21.48C): d=31.2 (CMe3), 56.2 (CMe3), 127.8, 129.5, 131.1 (Ph), 176.4 ppm
(NCN); 29Si{1H} NMR (78.7 MHz, [D6]benzene, 21.38C): d=
À17.53 ppm; elemental analysis calcd (%) for C15H23ClN2SSi: C 55.12, H
7.10, N 8.58; found: C 54.78, H 6.89, N 8.43.
CCDC-791618 (3), CCDC-791619 (4), CCDC-791620 (5), CCDC-791621
(6), CCDC-791622 (7), and CCDC-791623 (8) contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Synthesis of 6 and 7 from 2: Method A: A solution of S8 (0.021 g,
0.082 mmol) in toluene (10 mL) was added dropwise to a solution of 2
(0.30 g, 0.54 mmol) in toluene (15 mL) at room temperature. The result-
ing yellow solution was stirred at room temperature for 3 h. Volatiles
were then removed under reduced pressure and the solid was extracted
with a mixture of THF/hexane (1:1). The resulting yellow solution was
filtered and concentrated to give a mixture of 6 (major product) and 7 as
Chem. Eur. J. 2011, 17, 3490 – 3499
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Acknowledgements
This work was supported by the Academic Research Fund Tier 1 (RG
47/08). The authors thank Dr. Y. Li for performing the X-ray crystallo-
graphic analyses.
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Reactions of a Silylsilylene Derivative
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