Stannyl-substituted disilenes and a disilastannirane

Article abstract of DOI:10.1002/zaac.200900234

The reaction of disilenide Tip₂Si=Si(Tip)Li (1, Tip = 2,4,6iPr₃CoH₂) with chlorostannanes R₃SnCl quantitatively affords die first stannyl-substituted disuenes Tip ₂Si=Si(Tip)SnR₃ (2a: R = M

Full text of DOI:10.1002/zaac.200900234

ARTICLE
DOI: 10.1002/zaac.200900234
Stannylꢀsubstituted Disilenes and a Disilastannirane
Kai Abersfelder,[a] Thiꢀloan Nguyen,[a] and David Scheschkewitz*[a]
Dedicated to Professor Michael Veith on the Occasion of His 65th Birthday
Keywords: Group 14 elements; Metallacycles; Multiple bonds; Silicon; Stannanes
Abstract. The reaction of disilenide Tip2Si=Si(Tip)Li (1, Tip = 2,4,6ꢀ first heavy analogue of cyclopropanes containing two endocyclic siliꢀ
iPr3C6H2) with chlorostannanes R3SnCl quantitatively affords the first con and one tin atom was prepared from 1 and Me2SnCl2. All new
stannylꢀsubstituted disilenes Tip2Si=Si(Tip)SnR3 (2a: R = Me, 2b: R = compounds were characterised by multinuclear NMR spectroscopy and
Bu, 2c: R = Ph). The Snꢀfunctional derivative Tip2Si=Si(Tip)SntBu2Cl the thus deduced structural assignments corroborated by singleꢀcrystal
(3) is accessible in good yield from 1 and tBu2SnCl2. Additionally, the Xꢀray diffraction.
were isolated in yields between 59 % and 95 % after crystalliꢀ
sation from hexane and characterised by multinuclear NMR
spectroscopy. Single crystals of 2a and 3 were analysed by Xꢀ
ray diffraction.
Introduction
Organotin compounds are widely applied in synthetic orꢀ
ganic chemistry. The palladiumꢀcatalysed coupling of organoꢀ
tin reagents with a variety of organic substrates (Stille coupꢀ
ling) allows for the generation of sp2–sp2 carbon–carbon
linkages under mild and neutral conditions; a broad variety of
unprotected functional groups on both coupling partners are
tolerated [1]. The transmetallation of tin organyls is a useful
tool for the preparation of organo lithium species, e.g. vinylꢀ
lithium[2] or allyllithium [3] compounds.
During the last five years we and others have reported a
variety of disilenides, disila analogues of vinyl anions [4, 5].
The rising interest in this class of compounds stems from their
ability to transfer the Si=Si double bond to organic and inorꢀ
ganic substrates [5a, 5d, 5g, 6]. In order to broaden the scope
of the Si=Si transfer, the preparation of a range of hitherto
unknown stannylꢀsubstituted disilenes appeared desirable and
will be reported here. Additionally, we discuss the preparation
of a Snꢀchlorinated derivative, a chlorostannyl disilene, as well
Scheme 1. Syntheses of stannyl disilenes 2a–c (a: R = Me, b: R = Bu,
c: R = Ph) and 3 as well as disilastannirane 4 (Tip = 2,4,6ꢀiPr3C6H2).
as that of a related saturated cyclic compound, a disilastanniꢀ
rane.
The 119Sn NMR resonances of 2a–c from –52.9 to
Results and Discussion
–108.9 ppm are found in the expected range for tetracoordiꢀ
nated tin atoms (Table 1). The chemical shifts in the 29Si NMR
chemical shifts of the stannyl disilenes 2a–c between 113.3
and 103.4 ppm for the SiTip2 moiety and 38.9 and 30.4 ppm
for the tinꢀbonded silicon atom are similar to those of the monꢀ
osilyl disilenes were reported earlier [5a, 6e]. All signals were
unambiguously assigned with the help of 29Si,1H 2DꢀNMR
spectra and show well resolved 119Sn–29Si coupling patterns.
The reactions of disilenide 1 with R3SnCl or tBu2SnCl2 in
hexane or toluene lead to stannylꢀsubstituted disilenes 2a–c (a:
R = Me, b: R = Bu, c: R = Ph) and 3 (Scheme 1). The products
* Dr. D. Scheschkewitz
Fax: +44ꢀ20ꢀ7594ꢀ5804
EꢀMail: d.scheschkewitz@imperial.ac.uk
[a] Department of Chemistry
Imperial College London
South Kensington Campus
Exhibition Road
1
For all stannyl disilenes 2a–c the J(119Sn/29Si) coupling conꢀ
stants are between 3.5 and 4.0 times larger than the correꢀ
2
London SW7 2AZ, UK
sponding J values.
Z. Anorg. Allg. Chem. 2009, 635, 2093–2098
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K. Abersfelder, T.ꢀl. Nguyen, D. Scheschkewitz
ARTICLE
Table 1. Comparison of 29Si NMR and UV/Vis Data of Stannyl Disileꢀ
nes 2a, 2b, 2c and 3.
2a
2b
2c
3
δ29Si1
38.9
36.8
105.3
–52.9
353.6
98.8
430
30.4
40.9
114.5
109.5
88.4
106.9
431
δ29Si2
103.4
–68.3
474.2
122.9
441
113.3
–108.9
480.7
119.7
417
δ119Sn
1JSn,Si /Hz
2JSn,Si /Hz
λmax /nm
ε /103 L·M–1·cm–1
8.3
9.6
10
10
The UV/Vis spectra of 2a–c are very similar to that of the
monosilylꢀsubstituted disilenes as well (Table 1). The extincꢀ
tion coefficients range from ε = 8300 to 10000.
Single crystals of 2a were investigated by Xꢀray diffraction
to confirm the structure deduced from the spectroscopic data
(Figure 1). Stannyl disilene 2a crystallised with two indepenꢀ
dent molecules plus half a molecule of hexane in the asymmetꢀ
ric unit. Both molecules differ slightly in the Si=Si bond length
[2a: Si1–Si2: 216.18(8); Si3–Si4 217.18(9) pm]. A similar obꢀ
servation had been made in case of Tip2Si=Si(Tip)SiPh2Cl,
which exhibits four different Si=Si bond lengths in the asymꢀ
metric unit [6e]. Similarly, in case of 2a, the variability of the
Si=Si bond length can be rationalised with the conformational
flexibility of the Si=Si double bond: the relatively weak crystal
packing forces account for a substantial variations in transꢀ
bending of the disilene molecules, which in turn are closely
related to the Si=Si bond length. In case of 2a, the smaller
transꢀbent angles θ are found in the molecule with the shorter
Si=Si distance (2a: θSi1 = 10.85°, θSi2 = 14.74°, θSi3 = 18.82°,
θSi4 = 17.87°; θ is the angle between the Si=Si bond vector
Figure 1. Structure of 2a in the solid state. Thermal ellipsoids at the
30 % probability level. Only one of the two independent molecules
shown. Disordered iPr groups and protons omitted for clarity. Selected
bond lengths /pm and angles /° (for the depicted molecule only): Si1–
Si2 216.18(8), Si1–Sn1 256.75(6), Si1–C1 189.6(2), Si2–C16
190.9(2), Si2–C31 189.3(2), Si2–Si1–Sn1 120.57(3), Sn1–Si1–C1
117.79(7), C1–Si1–Si2 121.56(7), C16–Si2–Si1 125.40(7), C16–Si2–
C31 122.17(10), C31–Si2–Si1 111.69(7).
and the normal of the plane defined by a silicon atom and the structural parameters at the tin atom have been reported for the
ipso atoms of the pendant groups). The Sn–Si distances of the simple monostannane Mes*Sn(Cl)tBu2 (Mes* 2,4,6ꢀ
=
two molecules of 2a are virtually identical [256.75(6) to tBu3C6H2) [8]. Although not manifested in the observed intraꢀ
256.23(6) pm] and in the expected range for Sn–Si single molecular Sn1–Si2 distances [419.92(10) and 418.56(10) pm],
bonds from 252 to 261 pm [7].
a weak through space interaction and thus a certain degree of
Like in the case of 2a, the structure of chlorostannylꢀsubstiꢀ coordination sphere expansion of tin from four to five cannot
tuted disilene 3 in the solid state as determined by Xꢀray difꢀ be excluded.
fraction on single crystals shows two independent molecules
At least in solution, the NMR spectroscopic analysis of 3
in the asymmetric unit (Figure 2). The Si=Si bonds of 3 are indeed suggests the presence of a through space interaction
slightly longer than those of 2a [3: Si1–Si2: 218.82(12), Si3– between Sn1 and Si2, the silicon atom in βꢀposition to the
Si4: 217.67(11) pm]. The same holds true for the Sn–Si bonds stannyl group. The 119Sn signal of 3 is considerably shifted to
[3: Si1–Sn1 259.74(9), Si3–Sn2 258.97(9) pm], which sugꢀ low field by the presence of the electronegative chlorine atom.
gests that all elongations relative to 2a are mainly because of Additionally, an electronegative substituent such as chlorine is
the increased steric demand of the substitution pattern in 3 expected to lower the σ* orbitals at tin and thus facilitate any
rather than to any σ*ꢀconjugative effects. Similarly as in 2a, through space interaction. Indeed, the chlorostannylꢀsubstiꢀ
the shorter Si=Si bond correlate to smaller transꢀbent angles tuted disilene 3 exhibits a rather small oneꢀbond coupling conꢀ
1
(3: θSi1 = 22.42°, θSi2 = 17.95°, θSi3 = 15.36°, θSi4 = 10.53°). stant of J(119Sn/29Si) = 88.4 Hz, which is in fact smaller than
It is noteworthy that the tin coordination environments are conꢀ the twoꢀbond coupling of 2J(119Sn/29Si) = 106.9 Hz. This
siderably distorted from the ideal tetrahedral one. The sums of would be nicely explained by a second coupling pathway with
1
bonds angles at the tin atoms disregarding the angles involving reversed sign attenuating the J coupling constant.
chlorine is close to 360°, which indicates an almost triangular
As mentioned before, however, no corroborating evidence
pyramidal coordination sphere (Sn1 354.6°, Sn2 351.7°). The for such an interaction could be obtained from neither spectroꢀ
tin–chlorine distance is inconspicuous [Sn1–Cl1 239.63(9), scopic nor crystallographic data. It is known that tin coupling
Sn2–Cl2 240.70(10) pm] and therefore the described distortion constants are very sensitive to small variations in structural
could well be attributed to steric congestion. In fact, similar parameters even though there are only few examples of clearꢀ
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Z. Anorg. Allg. Chem. 2009, 2093–2098

Stannylꢀsubstituted Disilenes and a Disilastannirane
zene is exposed to ambient light, complete conversion to an as
yet unidentified product is attained after one week.
Disilastannirane 4 crystallises with two independent molecuꢀ
les in the asymmetric unit (Figure 3). The Si–Si bond lengths
are determined to 237.66(9) pm and 237.99(9) pm, which is
significantly longer than the corresponding Si–Si bond of the
related cyclotrisilane 5 [235.8(1) pm] [6e]. Given the unavailaꢀ
bility of data on disilastannirane, comparison with the known
disilagermiranes seems appropriate. Derivative 6 was reported
by Watanabe, Goto et al. in 1996 [12], 7 by Sekiguchi et al. in
2003 (Scheme 2) [13].
Figure 2. Structure of 3 in the solid state. Thermal ellipsoids at the
30 % probability level. Only one of the two independent molecules
shown. Coꢀcrystallised hexane, disordered iPr groups and protons
omitted for clarity. Selected bond lengths /pm and angles /° (for the
depicted molecule only): Si1–Si2 218.82(12), Si1–Sn1 259.74(9), Si1–
C1 189.8(3), Si2–C16 189.9(3), Si2–C31 188.6(3), Sn1–Cl1 239.63(9),
Si2–Si1–Sn1 122.44(4), Sn1–Si1–C1 115.62(9), C1–Si1–Si2
117.86(10), C16–Si2–Si1 130.05(9), C16–Si2–C31 111.34(12), C31–
Si2–Si1 115.39(9), Si1–Sn1–Cl1 99.91(3), Si1–Sn1–C46 125.06(9),
Si1–Sn1–C50 112.87(9).
Figure 3. Structure of 4 in the solid state. Thermal ellipsoids at the
30 % probability level. Only one of the two independent molecules is
displayed and hydrogen atoms are omitted for clarity. Selected bond
lengths /pm and angles /° (for the depicted molecule only): Si1–Si2
237.66(9), Si1–Sn1 254.22(6), Si2–Sn1 261.26(7), Si1–Cl1 210.45(9),
Si1–C1 189.8(2), Si2–C16 190.5(2), Si2–C31 191.2(2), C1–Si1–Si2
141.59(7), C1–Si1–Sn1 135.91(8), Si2–Si1–Sn1 64.06(2), Si1–Si2–
Sn1 61.05(2), Si1–Sn1–Si2 54.89(2), Si2–Si1–Sn1–C91 97.33(10),
Si2–Si1–Sn1–C91 121.61(10).
1
2
cut correlations between J(119Sn/13C) and J(119Sn/1H) coupꢀ
ling constants and bond angles or distances [9]. Likewise the
prediction of 119Snꢀcoupling constants by quantum chemical
methods is still in its infancy and a matter of current research
[10].
In order to probe whether the steric demand of the tertꢀbutyl
groups at tin might prevent a more tangible 1,3ꢀinteraction beꢀ
tween Sn1 and Si2, we investigated the reaction of 1 with
Me2SnCl2. The treatment of disilenide 1 with a 1.2ꢀfold excess
of Me2SnCl2 indeed results among other unidentified products
in the formation of a threeꢀmembered ring compound
(Scheme 1), albeit one where the chlorine atom has shifted
from Sn1 to Si1 in what resembles the isomerisation of chloroꢀ
silylꢀsubstituted disilenes to cyclotrisilanes [6e].
Scheme 2. Heavy cyclopropane analogues 5 [6e, 6 12], and 7 (Tip =
2,4,6ꢀiPr3C6H2, R = tBu) [13].
The first disilastannirane 4 was isolated in 21 % yield by
crystallisation at 0 °C from hexane and was characterised by
One of the Si–Si–Sn angles of each molecule of 4 is considꢀ
multinuclear NMR spectroscopy and singleꢀcrystal Xꢀray difꢀ erably wider than the others [Si2–Si1–Sn1 64.06(2)°, Si4–Si3–
fraction. The 29Si NMR spectrum shows two signals at Sn2 63.67(2)°; Si1–Si2–Sn1 61.05(2)°, Si3–Si4–Sn2
–28.3 ppm and –57.3 ppm in the typical region for heavier 61.38(2)°], which avoids the steric congestion around Si2 to
cyclopropanes [11]. The 119Sn NMR signal is observed at some extent. In accord with the larger covalent radius, the enꢀ
–252.4 ppm. Because of the relatively broad signals, the tin– docyclic angle of 4 at tin [Si1–Sn1–Si2 54.89(2)°; Si3–Sn2–
silicon coupling constants could not be resolved in case of 4. Si4 54.94(2)°] is significantly smaller than the corresponding
Unlike the openꢀchained derivatives 2a–c and 3, the cyclic angles of 6 and 7 at germanium (6: 58.6°; 7: 57.19°) [12, 13].
compound 4 is sensitive to light. When a solution of 4 in benꢀ The resulting higher ring strain should favour any ring opening
Z. Anorg. Allg. Chem. 2009, 2093–2098
© 2009 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim
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2095

K. Abersfelder, T.ꢀl. Nguyen, D. Scheschkewitz
ARTICLE
temp.): δ = –68.3 (1J(Sn,Si) = 474.2, 2J(Sn,Si) = 122.9, 1J(Sn,C) =
283.7 Hz, SnMe3). UV/Vis (hexane): λmax (ε) 441 nm
(8300 L·mol–1·cm–1). Exact Mass (ESIꢀMS) Calcd. m/z for
C48H78Si2Sn+ (M+): 830.4664. Found: 830.4662. MS (CI, isobutane)
m/z = 830 (M+), 697 (M++O2–SnMe3), 665 (M+–SnMe3), 449
or expansion reaction, which could explain the relatively high
sensitivity of 4 towards light. Additionally, unlike the correꢀ
sponding cyclotrisilane 5 the tin derivative 4 is sensitive toꢀ
wards oxygen and moisture. This increased reactivity of 4
might well be of preparative use in future studies.
+
(Tip2SiMe+), 433, 321, 261, 245, 231, 203, 189, 43 (C3H7 ).
1ꢀTributylstannylꢀ1,2,2ꢀtris(2',4',6'ꢀtriisopropylphenyl)disilene
(2b): Toluene (30 mL) was added to disilenide 1 (5.14 g, 6.023 mmol)
through a cannula. The orange solution was cooled to 0 °C and
Bu3SnCl (1.96 g, 6.021 mmol) was added through a syringe. After
stirring for 16 h, the precipitated LiCl was removed by filtration. All
volatiles were removed in vacuo and the solid residue was dissolved
in pentane (approx. 5 mL). After 5 days at 0 °C, 4.97 g (86 %) 2b
were separated from the mother liquor as red crystals (mp. 64–67 °C).
Elemental analysis: calcd. for C57H96Si2Sn: C, 71.59; H, 10.12. Found:
Conclusions
The first stannylꢀsubstituted disilenes 2a–c were synthesised
from disilenide 1 and the appropriate chlorostannanes. While
the reaction of 1 and tBu2SnCl2 yields Snꢀfunctional stannyl
disilene 3, treatment of 1 with Me2SnCl2 affords the first disiꢀ
lastannirane 4. All new compounds were characterised by mulꢀ
tinuclear NMR spectroscopy and the derived structures were
confirmed by singleꢀcrystal Xꢀray diffraction for each class of C, 71.55; H, 9.96.
compounds. Studies concerning the reactivity of stannyl disileꢀ
1H NMR (500 MHz, C6D6, room temp.): δ = 7.072, 7.070, 6.99 (each
nes 2a–c are currently in progress.
s, each 2 H, TipꢀH), 4.36, 4.12, 3.86 (each hept., each 2 H, iPrꢀCH),
2.79, 2.75, 2.66 (each hept., each 1 H, iPrꢀCH), 1.57 (m, 6 H, Buꢀ
CγH2), 1.38 (d, 12 H, iPrꢀCH3), 1.32 (q, 6 H, BuꢀCαH2), 1.24, 1.19,
1.10 (each d, altogether 36 H, iPrꢀCH3), 0.98 (m, 6 H, BuꢀCβH2), 0.96
(d, 6 H, iPrꢀCH3), 0.88 (t, 9 H, BuꢀCδH3). 13C NMR (125 MHz, C6D6,
room temp.): δ = 155.84, 155.24, 154.99 (TipꢀCo), 151.13, 150.85,
150.13 (TipꢀCp), 135.65, 135.47, 132.92 (TipꢀCi), 122.33, 121.97,
121.66 (TipꢀCH), 38.34, 37.41, 36.54, 34.84, 34.77, 34.49 (iPrꢀCH),
30.45, 27.94 (1J(Sn,C) = 63.4 Hz, BuꢀCγ/α), 24.60, 24.17, 23.94 (iPrꢀ
Experimental Section
All manipulations were carried out under a protective atmosphere of
argon or nitrogen using standard Schlenk techniques and a glovebox.
Ethereal solvents were heated under reflux over sodium/benzopheꢀ
none; hexane over sodium and deuterated benzene over potassium. All
solvents were stored under argon and degassed prior to use. NMR
spectra were recorded with a Bruker DRX–400 FTꢀNMR spectrometer
CH3), 13.98, 12.44 (2J(Sn,C)
=
280.1 Hz, BuꢀCδ/β). 29Si NMR
(
119Sn, 149.21 MHz) or a Bruker Avance 500 FTꢀNMR spectrometer
(99.36 MHz, C6D6, room temp.): δ = 105.3 (2J(Sn,Si) = 98.8 Hz,
SiTip2), 36.8 (1J(Sn,Si) = 353.6 Hz, SiTip). 119Sn NMR (186.46 MHz,
C6D6, room temp.): δ = –52.9 (1J(Sn,Si) = 353.6, 2J(Sn,Si) = 98.8,
(1H, 500.13 MHz, 13C, 125.76 MHz, 29Si, 99.36 MHz). 1H and
13C{1H} NMR spectra were referenced to the peaks of residual protons
of deuterated solvents (1H) or the deuterated solvent itself (13C). 29Si
NMR spectra were referenced to external TMS and 119Sn NMR spectra
were referenced to external Bu4Sn in C6D6 (–11.7 ppm). All chemical
shifts are reported in ppm. Elemental analyses (C, H) were performed
with a Leco Instruments Elemental Analyzer, type CHNS 932. UV/
Vis spectra were recorded with a Perkin–Elmer Lambda 20 UV/Vis
Spectrometer. Melting points were determined under argon or nitrogen
in closed NMR tubes and are uncorrected. Tip2Si = Si(Tip)Li (1) was
prepared according to our published procedure [5a]. Chlorostannanes
were purchased from Sigma–Aldrich and used as received.
1
2J(Sn,C) = 280.1, J(Sn,C) = 63.4 Hz, SnBu3). UV/Vis (hexane): λmax
(ε) 430 nm (9620 L·mol–1·cm–1). MS (CI, isobutane) m/z = 956 (M+),
931 (M++O2–C4H9), 899 (M+–C4H9), 697 (M++O2–SnBu3), 665 (M+–
SnBu3), 491 (Tip2SiBu+), 433, 345, 323 (SnBu3++O2), 289, 231, 203,
+
189, 43 (C3H7 ).
1ꢀTriphenylstannylꢀ1,2,2ꢀtris(2',4',6'ꢀtriisopropylphenyl)ꢀdisilene
(2c): Toluene (25 mL) was added to a mixture of disilenide 1 (2.54 g,
2.976 mmol) and Ph3SnCl (1.15 g, 2.983 mmol) through a cannula at
0 °C. The resulting orange suspension was stirred overnight at room
temperature. Precipitated solids were filtered off and volatiles were
removed from the filtrate in vacuo. The remaining solid was dissolved
in hot hexane (5 mL). After 16 h at room temperature, 2.21 g (73 %)
2c were isolated as red crystals (mp. 170 °C, dec). Elemental analysis:
Calcd. for C63H84Si2Sn: C, 74.46; H, 8.33. Found: C, 74.00; H, 8.36.
1ꢀTrimethylstannylꢀ1,2,2ꢀtris(2',4',6'ꢀtriisopropylphenyl)ꢀdisilene
(2a): Hexane (40 mL) was added to a mixture of disilenide 1 (1.69 g,
1.980 mmol) and Me3SnCl (0.39 g, 1.957 mmol) through a cannula.
The resulting orange suspension was stirred overnight at room temperꢀ
ature. Precipitated solids were filtered off and the solvents were evapoꢀ
rated to yield red oil. After a few days, 1.56 g (95 %) 2a were obtained
as red crystals (mp. 141 °C, dec) from a minimum amount of pentane.
Elemental analysis: calcd. for C48H78Si2Sn: C, 69.46; H, 9.47. Found:
C, 68.70; H, 9.37.
1H NMR (500 MHz, C6D6, room temp.): δ = 7.74–7.60 (m, 6 H, Phꢀ
H), 7.09–7.03 (m, 9 H, PhꢀH), 7.02, 6.99, 6.91 (each s, each 2 H, Tipꢀ
H), 4.42, 4.06, 3.88 (each hept., each 2 H, iPrꢀCH), 2.68 (m, 3 H, iPrꢀ
CH), 1.25 (br., 6 H, iPrꢀCH3), 1.144, 1.137, 1.12 (each d, each 6 H,
iPrꢀCH3), 1.05, 0.98 (each d, each 12 H, iPrꢀCH3). 13C NMR
1H NMR (500 MHz, C6D6, room temp.): δ = 7.10, 7.08, 7.01 (each s, (125 MHz, C6D6, room temp.): δ = 155.96, 155.13, 154.56 (TipꢀCo),
each 2 H, TipꢀH), 4.35, 4.10, 3.90 (each hept., each 2 H, iPrꢀCH), 2.82 151.25, 151.09, 150.77 (TipꢀCp), 142.35 (1J(Sn,C) = 434.5 Hz, PhꢀCi),
(m, 2 H, iPrꢀCH), 2.72 (hept., 1 H, iPrꢀCH), 1.33, 1.26, 1.24, 1.14, 137.85 (2J(Sn,C) = 40.8 Hz, PhꢀCo), 135.71, 134.34, 130.97 (TipꢀCi),
0.99 (each d, altogether 54 H, iPrꢀCH3), 0.19 (SnꢀCH3). 13C NMR 128.59 (PhꢀCm/p), 122.51, 122.31, 122.00 (TipꢀCH), 38.15, 38.04,
(125 MHz, C6D6, room temp.): δ = 155.96, 155.38, 155.15 (TipꢀCo), 37.54, 34.77, 34.58, 34.50 (iPrꢀCH), 24.86, 24.55, 24.10, 24.04, 23.96
151.32, 150.92, 150.15 (TipꢀCi), 135.14, 134.61, 132.18 (TipꢀCp), (iPrꢀCH3). 29Si NMR (99.36 MHz, C6D6, room temp.): δ = 113.3
122.24, 122.01, 121.56 (TipꢀCH), 38.41, 37.53, 36.39, 34.94, 34.88,
(2J(Sn,Si) = 119.7 Hz, SiTip2), 30.4 (1J(Sn,Si) = 480.7 Hz, SiTip).
34.54 (iPrꢀCH), 25.16 (br.), 24.68, 24.29, 24.26, 24.03 (iPrꢀCH3), 119Sn NMR (186.46 MHz, C6D6, room temp.): δ = –108.9 (1J(Sn,Si) =
–5.17 (1J(Sn,C) = 283.7 Hz, SnꢀCH3). 29Si NMR (99.36 MHz, C6D6, 480.7, 2J(Sn,Si) = 119.7, 1J(Sn,C) = 434.5, 2J(Sn,C) = 40.8 Hz, SnPh3).
room temp.):
(1J(Sn,Si) = 474.2 Hz, SiTip). 119Sn NMR (186.46 MHz, C6D6, room isobutane) m/z = 1048 (M++O2), 1016 (M+), 971 (M++O2–C6H5), 767
δ = =
103.4 (2J(Sn,Si) 122.9 Hz, SiTip2), 38.9 UV/Vis (hexane): λmax (ε) 417 nm (10050 L·mol–1·cm–1). MS (CI,
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Z. Anorg. Allg. Chem. 2009, 2093–2098

Stannylꢀsubstituted Disilenes and a Disilastannirane
(11), 742 (M+–SnPh2), 697 (M++O2–SnPh3), 511 (Tip2SiPh+), 494, gen stream at the goniometer. The accumulation of data sets was carꢀ
+
+
433, 351 (SnPh3 ), 273, 231, 204, 189, 43 (C3H7 ).
ried out using a Bruker SMART CCD areaꢀdetector diffractometer with
MoꢀKα radiation (λ = 0.71073 Å) [14]. Unit cells were determined
using a number of representative frames. Intensities were determined
from several series of frames, each covering 0.3° in ω of an entire
sphere. Numerical absorption corrections were applied using SADꢀ
ABS. The structures were solved by direct methods or with a Patterson
map and refined by leastꢀsquares on weighted F2 values for all reflecꢀ
tions. Refinements (SHELXLꢀ97) yielded the crystallographic parameꢀ
ters summarized in Table 2. Crystallographic data (excluding structure
factors) for the structural analyses of 2a, 3, and 4 have been deposited
with the Cambridge Crystallographic Data Centre as CCDCꢀ728277,
ꢀ728278, ꢀ728279 Copies of this information may be obtained free of
charge from CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax:
+44ꢀ1223ꢀ336033; EꢀMail: deposit@ccdc.cam.ac.uk) or under http://
www.ccdc.cam.ac.uk
1ꢀ(Chlorodiꢀtertꢀbutylstannyl)ꢀ1,2,2ꢀtris(2',4',6'ꢀ
triisopropylphenyl)disilene (3): Hexane (25 mL) was added to a mixꢀ
ture of disilenide 1 (1.40 g, 1.640 mmol) and tBu2SnCl2 (0.50 g,
1.646 mmol) through a cannula at room temperature. The colour of
the mixture turned to dark red. After stirring overnight, all insoluble
parts were removed by filtration. The filtrate was reduced until the
product started to precipitate, which was redissolved by gentle heating
to 35 °C. After keeping at room temperature overnight, compound 3
(0.91 g, 59 %) was obtained as deep red crystals (mp. 155 °C dec.).
Elemental analysis: calcd. for C53H87Si2SnCl: C, 68.11; H, 9.38.
Found: C, 67.22; H, 9.30.
1H NMR (500 MHz, C6D6, room temp.): δ = 7.07, 7.03, 6.98 (each s,
each 2 H, TipꢀH), 4.39, 3.97, 3.65 (each hept., each 2 H, iPrꢀCH), 2.72
(m, 2 H, iPrꢀCH), 2.63 (hept., 1 H, iPrꢀCH), 1.43 (d, 12 H, iPrꢀCH3),
1.27 (s, 18 H, tBuꢀCH3), 1.18, 1.14, 1.07, 0.92 (each d, altogether 42
H, iPrꢀCH3). 13C NMR (125 MHz, C6D6, room temp.): δ = 156.36,
155.17, 155.06 (TipꢀCo), 151.77, 151.24, 150.78 (TipꢀCi), 135.27,
134.88, 132.80 (TipꢀCp), 122.81, 122.38, 122.32 (TipꢀCH), 40.88
(1J(Sn,C) = 302.1 Hz, tBuꢀCMe3), 38.47, 38.02, 36.85, 34.85, 34.72,
34.38 (iPrꢀCH), 31.82 (tBuꢀCH3), 25.69 (br.), 24.70, 24.19, 24.02,
Table 2. Selected Crystallographic Details for Compounds 2a, 3, and 4.
2a
3
4
Formula
T /K
C99H163Si4Sn2
173(2)
C53H87ClSi2Sn C47H75ClSi2Sn
173(2)
173(2)
System
triclinic
orthorhombic
Pca21
22.389(5)
19.011(4)
25.944(5)
90°
triclinic
¯
¯
P1
Space group
P1
23.86 (iPrꢀCH3). 29Si NMR (99.36 MHz, C6D6, room temp.): δ = 114.5 a /Å
11.5193(6)
14.1341(9)
17.9108(11)
20.6439(13)
69.9390(10)°
77.0990(10)°
89.8660(10)°
4769.3(5)
4
(2J(Sn,Si) = 106.9 Hz, SiTip2), 40.9 (1J(Sn,Si) = 88.4 Hz, SiTip). 119Sn
NMR (186.46 MHz, C6D6, room temp.): δ = 109.5. UV/Vis (hexane):
λmax (ε) 431 nm (10000 L·mol–1·cm–1). MS (CI, isobutane) m/z = 935
(M+), 909 (M++O2–C4H9), 877 (M+–C4H9), 853, 671, 665 (M+–
b /Å
c /Å
α
17.6904(10)
25.5702(14)
96.7910(10)°
β
γ
101.0180(10)° 90°
92.0510(10)°
5069.7(5)
2
90°
tBu2SnCl), 469 (Tip2SiCl+), 435, 265, 230, 204, 189, 57 (C4H9 ), 43
+
V /Å3
Z
11043(4)
8
+
(C3H7 ).
d /g·cm–3
µ /mm–1
F(000)
θmax
1.116
1.124
0.585
4000
1.184
1,1ꢀDimethylꢀ2ꢀchloroꢀ2,3,3ꢀtris(2',4',6'ꢀtriisopropylphenyl)ꢀ
disilastannirane (4): A solution of disilenide 1 (2.04 g, 2.390 mmol)
in toluene (20 mL) was added dropwise to a solution of Me2SnCl2
0.580
0.671
1826
1808
26.08°
73180
20064
1.063
26.02°
92746
21703
1.066
0.0344
0.0827
26.37°
(0.85 g, 3.869 mmol) over a period of 15 min at room temperature. Refl.total
85064
Refl.unique
S
19517
The resulting orange suspension was stirred overnight at room temperꢀ
ature. All precipitates were filtered off and the filtrate was evaporated
to give 2.25 g of a yellow solid. Crystallisation from hexane (10 mL)
at 0 °C yields 0.43 g (21 %) of 4 as colourless blocks (mp. 168 °C,
dec).
1.026
R1 (I > 2σ)
0.0393
0.0353
wR2 (all data) 0.1080
0.0898
1H NMR (500 MHz, [D8]toluene, room temp.): δ = 7.10, 7.09, 7.07
(each s, each 1 H, TipꢀH), 6.92 (s, 2 H, TipꢀH), 6.86 (s, 1 H, TipꢀH),
4.45–4.32 (m, 2 H, iPrꢀCH), 3.86 (hept., 1 H, iPrꢀCH), 3.60, 3.51, 3.18
(each br., each 1 H, iPrꢀCH), 2.71 (m, 2 H, iPrꢀCH), 2.63 (hept., 1 H,
iPrꢀCH), 1.42 (d, 6 H, iPrꢀCH3), 1.33 (br., 3 H, iPrꢀCH3), 1.30, 1.27,
1.17, 1,16, 1.14, 1.13, 1.082, 1.077 (each d, altogether 36 H, iPrꢀCH3),
0.81 (SnꢀCH3), 0.64, 0.44 (each br., altogether 9 H, iPrꢀCH3), 0.16 (Snꢀ
CH3). 13C NMR (125 MHz, [D8]toluene, room temp.): δ = 156.25,
156.18, 156.06, 156.01, 153.91 (TipꢀCo), 152.08, 150.80, 150.31 (Tipꢀ
Ci), 133.37, 130.42, 130.01 (TipꢀCp), 122.66, 122.12, 121.97, 121.71,
121.27, 121.23 (TipꢀCH), 38.17, 37.29, 37.14, 36.00, 35.68, 34.87,
34.66, 34.53, 34.29 (iPrꢀCH), 28.49 (br.), 27.94, 27.45, 27.11, 26.23,
24.59, 24.38, 24.05, 23.99, 23.62, 23.00, 22.45 (iPrꢀCH3), –8.72, –
10.81 (SnꢀCH3). 29Si NMR (99.36 MHz, [D8]toluene, room temp.):
δ = –28.3, –57.3. 119Sn NMR (186.46 MHz, [D8]toluene, room temp.):
δ = –252.4. Exact Mass (ESIꢀMS) Calcd. m/z for C47H75Si2SnCl+
(M+): 850.4118. Found: 850.4121. MS (CI, isobutane) m/z = 850 (M+),
665 (M+–Me2SnCl), 469 (Tip2SiCl+), 449 (Tip2SiMe+), 435, 323, 265,
Acknowledgement
Financial support by the Deutsche Forschungsgemeinschaft (DFG
SCHE906/3ꢀ2), the Aventis Foundation (KarlꢀWinnacker Fellowship),
Imperial College London (startꢀup funds) is gratefully acknowledged.
The authors thank Prof. Holger Braunschweig and his group for their
continuous support, as well as Dr. R. Bertermann (University of Würzꢀ
burg), Richard N. Sheppard and Dr. Peter R. Haycock (Imperial Colꢀ
lege London) for recording the NMR spectra.
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Received: April 21, 2009
Published Online: August 20, 2009
2098
www.zaac.wileyꢀvch.de
© 2009 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 2093–2098