Syntheses and reactivity of stannyloligosilanes. III. Lithiated stannasilanes - Building blocks for monocyclic Si-Sn rings

Article abstract of DOI:10.1002/1521-3749(200103)627:3<453::AID-ZAAC453>3.0.CO;2-6

Dilithiated di(stannyl)oligosilanes (^tBu₂Sn(Li)-(SiMe₂)_n-Sn(Li) ^tBu₂; 4, n = 2; 5, n = 3) were synthesized by the reaction of lithium diisopropylamide (LDA) with the α,ω-hydrido tin substit

Full text of DOI:10.1002/1521-3749(200103)627:3<453::AID-ZAAC453>3.0.CO;2-6

Syntheses and Reactivity of Stannyloligosilanes. III [1]
Lithiated Stannasilanes ± Building Blocks for Monocyclic Si±Sn Rings
Uwe Hermann, Gregor Reeske, Markus SchuÈrmann, and Frank Uhlig*
Dortmund, Anorganische Chemie II, Fachbereich Chemie der UniversitaÈt
Received September 12th, 2000.
Professor Herbert Jacobs zum 65. Geburtstag gewidmet
Abstract. Dilithiated di#stannyl)oligosilanes #tBu2Sn#Li)±
#SiMe2)n±Sn#Li)tBu2; 4, n = 2; 5, n = 3) were synthesized by
the reaction of lithium diisopropylamide #LDA) with
the a,x-hydrido tin substituted oligosilanes #tBu2Sn#H)±
#SiMe2)n±Sn#H)tBu2; 1, n = 2; 2, n = 3). Surprisingly, the re-
action of 1 and 3 #tBu2Sn#H)±#SiMe2)4±Sn#H)tBu2) with
LDA resulted not in the formation of the lithiated com-
pound, but what one can find is the formation of the 5,5-di-
tert.butyl-octamethyl-1,2,3,4-tetrasila-5-stannacyclopentane #8)
#n = 4) in addition to the expected product 4 #n = 4) and the
3,3,6,6-tetratert.butyl-octamethyl-1,2,4,5-tetrasila-3,6-distan-
nacyclohexane #7) #n = 3).
Reactions of 4 and 5 with dimethyl and diphenyldichloro-
silanes yielding monocyclic Si±Sn derivatives #9±11) are also
discussed. The solid-state structures of 7 and 11 were deter-
mined by X-ray crystallography.
Keywords: Tin; Stannasilanes; monocyclic Silicon-Tin rings;
NMR spectroscopy; Crystal structure
Synthese und ReaktivitaÈt von Stannyloligosilanen. III.
Lithiierte Stannasilane ± Bausteine fuÈr monocyclische Si±Sn-Ringe
InhaltsuÈbersicht. Zweifach lithiierte Di#stannyl)oligosilane
#tBu2Sn#Li)±#SiMe2)n±Sn#Li)tBu2; 4, n = 2; 5, n = 3) werden
durch die Reaktion von Lithiumdiisopropylamid #LDA)
mit den a,x-Hydridozinn-substitutierten Oligosilanen
#tBu2Sn#H)±#SiMe2)n±Sn#H)tBu2; 1, n = 2; 2, n = 3) erhalten.
Ûberraschenderweise ergibt die Umsetzung von 1 und 3
#n = 4) mit LDA nicht nur die erwarteten lithiierten Verbin-
dungen 4 und 6. Statt dessen findet man die Bildung eines
5,5-Ditert.butyl-octamethyl-1,2,3,4-tetrasila-5-stannacyclopen-
tanes #8) #n = 4) und, bei Verwendung von 1 als Ausgangs-
stoff, eines 3,3,6,6-Tetratert.butyl-octamethyl-1,2,4,5-tetra-
sila-3,6-distannacyclohexanes #7) als Konkurrenzprodukt zu
4. Umsetzung von 4 und 5 mit Dimethyl- oder Diphenyl-
dichlorosilan ergeben die monocyclischen Si±Sn-Derivate
9±11. Die MolekuÈlstrukturen von 7 und 11 werden ebenfalls
diskutiert.
1
Introduction
linear #tBu2Sn#Z)±#SiMe2)n±Sn#Z)tBu2; Z = H, Cl, Br,
n = 2±6) [2] and branched #MeSi[SiMe2±Sn#Z)R2]3;
Z = H, Me, Ph, Cl, Br, R = Me, Bu, Ph) [1] stannyloli-
t
Chain type a,x-functionalized oligosilanes are possi-
ble precursors for the synthesis of polymeric materials
as well as the formation of cyclic derivatives. The de-
velopment of silicon polymers containing other group
14 elements, requires a detailed investigation of the
synthesis and reactivity of precursor molecules. Our
special interest is focused on cyclic Si±Sn containing
compounds due to their possible applications in ring
opening polymerisations.
gosilanes. Initial studies concerned with the chemistry
of branched stannylsilanes with lithium diisopropyl-
amide yielding cyclic derivatives were discussed as well
[1]. The utilization of linear halogen substituted stan-
nyloligosilanes as building blocks for the preparation
of monocyclic Si±Sn derivatives with ring sizes ranging
from four to six were also reported [3]. As a continua-
tion of this work, we are now describing the reactions
of linear stannyloligosilanes with lithium diisopropyla-
mide #LDA) and subsequent of reactions of the result-
ing dilithio derivatives with diorganodichlorosilanes.
Recently we described the exploration of synthetic
avenues, structural features, and the reactivity of
* Privatdozent Dr. F. Uhlig,
Anorganische Chemie II, Fachbereich Chemie,
UniversitaÈt Dortmund,
2
Results and Discussion
Otto-Hahn-Str. 6,
The reaction of 1,1,5,5-tetratert.butyl-hexamethyl-1,5-
D-44221-Dortmund
e-mail: fuhl@platon.chemie.uni-dortmund.de
distanna-2,3,4-trisilapentane #2) with two equivalents
Z. Anorg. Allg. Chem. 2001, 627, 453±457
Ó WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0044±2313/01/627453±457 $ 17.50+.50/0
453

U. Hermann, G. Reeske, M. SchuÈrmann, F. Uhlig
of LDA served well in the preparation of the expected
dilithio derivative 5 #eq. #1)).
tBu2Sn#H)±#SiMe3)2±Sn#H)tBu2
‡2 LDA
t
! Bu2Sn#Li)±#SiMe2)3±Sn#Li)tBu2
#1)
À2 HNiPr2
5
Compound 2 can be converted quantitatively into de-
rivative 5 by maintaining a temperature range be-
tween ±30 °C and 0 °C.
Scheme 2 Reaction of 3 with LDA.
Surprisingly, one can not apply this reaction to stan-
nasilanes containing disila #1) or tetrasila #3) moieties
instead of the trisilane unit. The reaction of the disi-
lane derivative 1 resulted in a mixture of the expected
dilithio compound 4, the tetratert.butyldihydridodi-
stannane, and a silicon and tin containing ring. The
latter one was identified as the 3,3,6,6-tetratert.butyl-
1,1,2,2,4,4,5,5-octamethyl-1,2,4,5-tetrasila-3,6-distanna-
cyclohexane #7) #Scheme 1).
the rate determining step of the reaction. Rearrange-
ment and ring closure reactions of branched stan-
nasilanes have been observed recently when reacting
MeSi[SiMe2±Sn#H)tBu2]3 with three equiv. of LDA [1].
Novel monocyclic Si±Sn derivatives were obtained
by reacting 5 or mixtures of 4 and 7 with diorganodi-
chlorosilanes. The reaction of 5 with one equiv. of di-
methyldichlorosilane afforded the six membered ring
9 #Eq. #2)).
ꢀ2†
Treatment of the mixture of 4 and 7 with dimethyl- or
diphenyldichlorosilane gave 7 together with the five
membered rings 10 or 11 #Scheme 3).
Scheme 1 Reaction of 1 with two equiv. of LDA.
The ratio of the products 4 and 7 can be varied by
changing the reaction conditions; lower temperatures
yield higher amounts of 4, whereas higher tempera-
tures affords higher yields of compound 7, but the
concurrent formation of derivative 4 is still observed.
The reaction of the tetrasilane derivative 3 with two
equiv. of LDA results not in the formation of the ex-
pected dilithio compound 6, instead the five mem-
bered Si±Sn ring 8 under formation of the byproduct
tetratert.butyldihydridodistannane is observed. In con-
trast to the reaction of 1 the composition of the pro-
duct mixture did not depend on the reaction tempera-
ture.
Although we have only little experimental evidence
to postulate a reaction mechanism, we propose that
the formation of the dilithio substituted Si±Sn deriva-
tives is the kinetically controlled step while the forma-
tion of the five and the six membered rings 7 and 8 is
the thermodynamically controlled part of the reaction.
In the cases of using the disilane 1 or the tetrasilane 3
as starting materials the formation of the thermodyna-
mically favored five #7) and six membered #8) rings is
Scheme 3 Treatment of a mixture of 4 and 7 with diorgano-
dichlorosilanes.
Fortunately, the two reaction products may be sepa-
rated using column chromatography #using silica gel)
and fractional crystallization from n-hexane. The X-
454
Z. Anorg. Allg. Chem. 2001, 627, 453±457

Syntheses and Reactivity of Stannyloligosilanes. III. Lithiated Stannasilanes
Table 1 Crystal data and structure refinement for 7 and 11
7
11
Formula
fw, g/Mol
C24H60Si4Sn2
698.46
C32H58Si3Sn2
764.43
cryst syst
monoclinic
0.20 ´ 0.18 ´ 0.18 mm
P2#1)/n
9.505#2)
21.947#4)
17.404#3)
96.69#3)
3605.9#12)
4
monoclinic
0.25 ´ 0.15 ´ 0.13
P2#1)/n
10.553#2)
18.521#4)
19.966#4)
101.13#3)
3829.0#13)
4
cryst size, mm
space group
Ê
a, A
Ê
b, A
Ê
c, A
b°
3
Ê
V, A
Z
qcalcd, Mg/m3
1.287
1.528
1.326
1.416
l, mm±1
F#000)
1440
1568
h range, deg
index ranges
3.00 to 25.99
0 £ h £ 11
0 £ k £ 27
±21 £ l £ 21
7502
7066/0.0636
292
0.971
3.00 to 25.49
0 £ h £ 12
0 £ k £ 22
±24 £ l £ 23
7505
7102/0.0546
352
1.012
Fig. 1 View of a molecule of 7 showing 30% probability
displacement ellipsoids #ORTEP3). Hydorgen atoms and
carbon atoms bonded to silicon have been removed for
clarity.
no. of reflections collected
no. of indep reflns/Rint
no. of refined params
GooF #F 2)
R1 #F) #I > 2r#I))
0.0743
0.1593
0.772/±0.580
0.0626
0.1686
0.994/±1.121
wR2 #F 2) #all Data)
3
Ê
Largest diff. Peak/hole, e/A
R1 = R||Fo| ± |Fc||/R|Fo|, wR2 = sqrtRw{#Fo)2 ± #Fc)2}/Rw{#Fo)2}2.
Ê
Table 2 Selected Bond Lengths/A and Angles/° for 7 and 11
7
11
Sn#1)±Si#4)
Sn#1)±Si#1)
Si#1)±Si#2)
Sn#2)±Si#2)
Sn#2)±Si#3)
Si#3)±Si#4)
2.595#3)
2.597#3)
2.341#4)
2.586#3)
2.594#3)
2.334#4)
Sn#1)±Si#3)
Sn#1)±Si#1)
Sn#2)±Si#1)
Sn#2)±Si#2)
Si#3)±Si#2)
2.597#3)
2.623#2)
2.616#2)
2.623#3)
2.339#4)
C#5)±Sn#1)±C#1)
C#5)±Sn#1)±Si#4)
C#1)±Sn#1)±Si#4)
C#5)±Sn#1)±Si#1)
C#1)±Sn#1)±Si#1)
Si#4)±Sn#1)±Si#1)
108.9#4)
C#35)±Sn#1)±C#31) 107.5#4)
108.9#3)
109.8#3)
109.8#4)
109.5#3)
110.36#9)
C#35)±Sn#1)±Si#3)
C#31)±Sn#1)±Si#3)
C#35)±Sn#1)±Si#1)
C#31)±Sn#1)±Si#1)
Si#3)±Sn#1)±Si#1)
111.4#3)
109.8#3)
112.1#3)
113.4#3)
102.69#8)
C#15)±Sn#2)±C#11) 110.6#5)
C#21)±Sn#2)±C#25) 109.0#4)
C#15)±Sn#2)±Si#2)
C#11)±Sn#2)±Si#2)
C#15)±Sn#2)±Si#3)
C#11)±Sn#2)±Si#3)
Si#2)±Sn#2)±Si#3)
108.7#3)
109.6#3)
110.1#3)
108.2#3)
109.53#9)
C#21)±Sn#2)±Si#1)
C#25)±Sn#2)±Si#1)
C#21)±Sn#2)±Si#2)
C#25)±Sn#2)±Si#2)
Si#1)±Sn#2)±Si#2)
114.2#3)
115.4#3)
110.5#3)
107.4#4)
99.82#8)
Fig. 2 View of a molecule of 11 showing 30% probability
displacement ellipsoids #ORTEP3). Hydorgen atoms have
been removed for clarity.
ray structures of 7 and 11 are shown in figure 1 and 2.
Unit cell data, refinement details, and selected intera-
tomic parameters are summarized in tables 1 and 2.
X-ray quality crystals of 7 and 11 were obtained from
saturated n-hexane solutions. Compounds 7 and 11 ex-
hibit almost perfect tetrahedral environment at the tin
and silicon atoms. Small deviations from the tetrahe-
dral structure are induced by sterical effects. Si±Sn,
Si±C, and Sn±C distances are within the usual range.
Remarkable is the ring conformation of compound 7
#Figure 1), exhibiting a twisted conformation caused
by the larger steric demands of the tert.butyl groups, a
more rare example for the conformation of six mem-
bered oligosilanes [4].
3
Experimental Part
3.1 General Methods
All reactions were carried out under an atmosphere of inert
gas #N2 or Ar) using Schlenk techniques. All solvents were
dried by standard methods and freshly distilled prior to use.
The compounds 1±3 [2] and lithium diisopropylamide [5]
were prepared according to published procedures. All other
chemicals used as starting materials were obtained commer-
cially. H and 13C NMR spectra were recorded using a Bru-
1
ker DPX 400 spectrometer #solvents CDCl3 or C6D6, inter-
nal reference Me4Si). 29Si and 119Sn NMR spectra were
recorded using a Bruker DPX 400 spectrometer #solvents
CDCl3 or C6D6, internal reference Me4Si or Me4Sn, respec-
Z. Anorg. Allg. Chem. 2001, 627, 453±457
455

U. Hermann, G. Reeske, M. SchuÈrmann, F. Uhlig
tively) or a Bruker DRX 300 spectrometer #solvents hexane
or THF with D2O-capillary, internal reference Me4Si or
Me4Sn, respectively). If not otherwise stated, the NMR ex-
periments were carried out H decoupled. MS analyses were
recorded using a MAT 8200. Elemental analyses were per-
formed on a LECO-CHNS-932 analyzer.
4,4,6,6-tetratert-butyl-1,1,2,2,3,3,5,5-octamethyl-1,2,3,5-
tetrasila-4,6-distannacyclohexane ꢀ9)
Starting materials: 2.4 mmol of 5, 0.31 g #2.4 mmol) Me2SiCl2.
Reaction temperature 0 °C. The resulting oil was purified by
column chromatography #silica gel/n-hexane). Recrystalliza-
tion from n-hexane/diethylether #1 : 1) gave 1.2 g #71%) of 9.
EA: C24H60Si4Sn2, 698.49 g/mol, found #calc.): C 41.8
#41.27), H 8.8 #8.66)%.
1
3.2 General Procedure for the formation of 4 and 5
Mp.:
168 °C.
29Si
72 Hz],
NMR
#59.63 MHz,
±37.0[
D2O-cap.):
d = ±38.2
273/261 Hz,
[2J#119/117Sn±29Si):
1J#119/117Sn±29Si):
A solution of LDA #5.4 mmol in 15 mL of n-hexane and
15 mL of THF) was added dropwise to a cooled solution
#0 °C) of 1, 2 or 3 #2.7 mmol) in 100 mL of a 1 : 1 mixture of
THF and n-hexane. The reaction mixture was stirred at this
temperature for 1 h. The solution was examined by 29Si and
119Sn NMR spectroscopy.
3J#119/117Sn±29Si): 95 Hz], ±30,7 [1J#119/117Sn±29Si): 229/218 Hz]. 119Sn
NMR #111.92 MHz, D2O-cap.): d = ±156.2 [2J#119Sn±117Sn): 291 Hz,
1J#119/117Sn±29Si): 228 Hz].
3,3,5,5-tetratert-butyl-1,1,2,2,4,4-hexamethyl-1,2,4-
trisila-3,5-distannacyclopentane ꢀ10)
Starting materials: 8 mmol of a mixture of 4 and 7, 1.03 g
#8 mmol) Me2SiCl2. Reaction temperature 0 °C. The result-
ing oil was purified by column chromatography #silica gel/
n-hexane) to give 3.07 g of a mixture of 7 and 10. The resi-
due was dissolved in 20ml of n-hexane, stored at ±35 °C to
give 1.18 g #23%) of 7. After removel of three quarter of the
solvent in vacuo the solution was stored again at ±35 °C to
give 1.38 g #25%) of 10. Mp.: 150 °C #dec.).
Attempts towards the formation of 1,4-Dilithio-1,1,4,4-
tetratert.butyl-tetramethyl-1,4-distanna-2,3-disilabutane ꢀ4)
Starting materials: 8.0mmol #3.5 g) of 1 in 100 mL of THF/
hexane #1 : 1), 16.0mmol LDA in 60mL of THF/hexane
#1 : 1). 7 occurs as a byproduct of the synthesis of 4.
NMR investigation of the reaction solution: 4: 29Si NMR #59.63 MHz,
D2O-cap.): d ±28.4 [1J#119/117Sn±29Si): not detected], 119Sn #111.92 MHz,
D2O-cap.):
d
±94.8. 7; 29Si NMR #59.63 MHz, D2O-cap.): d = ±33.6
EA: C22H54Si3Sn2, 640.34 g/mol, found #calc.): C 41,1
#41,3), H 9,0#8,5)%.
[1J#119/117Sn±29Si): 272/260Hz, 2J#119/117Sn±29Si): 80Hz]. 119Sn NMR
#111.92 MHz, D2O-cap.): d = ±164.2 [1J#119/117Sn±29Si): 274 Hz].
1H NMR #400.15 MHz, CDCl3): d = 0.36 [12 H, 2 ´ SiMe2], 0.39 [6 H,
SiMe2], 1.26 [36 H, Sn±C±Me3, 3J#119/117Sn±1H): 43 Hz]. 29Si NMR
#59.63 MHz, D2O-cap.): d = ±32.3 [1J#119/117Sn±29Si): 294/281 Hz,
2J#119/117Sn±29Si): 90Hz], ±31.1 [ 1J#119/117Sn±29Si): 228/212 Hz]. 119Sn
NMR #111.92 MHz, D2O-cap.): d = ±147.6 [2J#119Sn±117Sn): 365]. MS #M/
z): 640[M +, 100%], 583 [M+ ± tert.butyl, 20%], 527 [M+ ± 2 ´ tert.butyl,
20%], 469 [M+ ± 3 ´ tert.butyl, 40%].
tBu2SnꢀH)±SnꢀH)tBu2: 119Sn NMR #111.92 MHz, D2O-cap.):
d = ±83.7 [1J#119Sn±117Sn): 1260Hz].
1,5-Dilithio-1,1,5,5-tetratert.butyl-hexamethyl-1,5-
distanna-2,3,4-trisilapentane ꢀ5)
Starting materials: 2.4 mmol #1.52 g) of 2 in 100 mL of THF/
hexane #1 : 1), 5.4 mmol LDA in 30mL of THF/hexane
#1 : 1).
3,3,5,5-tetratert-butyl-1,1,2,2-tetramethyl-4,4-diphenyl-
1,2,4-trisila-3,5-distannacyclopentane ꢀ11)
29Si NMR #59.63 MHz, D2O-cap.): d = ±29.6 [1J#119/117Sn±29Si): not de-
tected], d = ±37.0[ 2J#119/117Sn±29Si): not detected]. 119Sn #111.92 MHz,
D2O-cap.): d = ±104.7.
5,6 mmol of a mixture of 4 and 7, 1.42 g #5.6 mmol) Ph2SiCl2.
Reaction temperature ±65 °C. The resulting oil was purified
by column chromatography #silica gel/n-hexane) to give
2.28 g of a mixture of 7 and 11 #75% 11; 25% 7; determined
by NMR spectroscopy). The residue was dissolved in 20ml
of n-hexane, and stored at ±35 °C to give 0.85 g #22%) of 7.
After removel of three quarter of the solvent in vacuo the
solution was stored again at ±35 °C to give 0.85 g #20%) of
11. Mp.: 160 °C. EA: C32H58Si3Sn2, 764.49 g/mol, found
#calc.): C 50,5 #50,28), H 8,1 #7,65)%.
1H NMR #400.15 MHz, CDCl3): d = 0.53 [12 H, 2 ´ SiMe2, 3J#119/
117Sn±1H): 23 Hz], 1.18 [36 H, Sn±C±Me3, 3J#119/117Sn±1H): 60Hz],
7.24 ppm [Si±Ph], 7.56 [Si±Ph]. 13C NMR #100.63 MHz, CDCl3): d = ±1.8
[2 ´ SiMe2], 32.3 [Sn±C±Me3, 1J#119Sn±13C): 244 Hz], 34.2 [Sn±C±Me3],
127.6, 128.3, 137.5, 138.2 [12 C, Si±Ph]. 29Si NMR #59.63 MHz, D2O-cap.):
d = ±31.5 [1J#119/117Sn±29Si): 274/265 Hz, 2J#119/117Sn±29Si): 67 Hz], ±11.2
[1J#119/117Sn±29Si): 190Hz]. 119Sn NMR #111.92 MHz, D2O-cap.): d =
±152.3 [2J#119Sn±117Sn): 310Hz]. MS #M/z): 765 [M +, 2%], 707 [M+ ± tert.-
butyl, 75%], 649 [M+ ± 2 ´ tert.butyl, 10%], 591 [M+ ± 3 ´ tert.butyl, 15%],
534 [M+ ± 4 ´ tert.butyl, 17%], 478 [M+ ± 4 ´ tert.butyl ± SiMe2, 10%], 457
[M+ ± 4 ´ tert.butyl ± Ph, 10%], 400 [M+ ± 4 ´ tert.butyl ± SiMe2 ± Ph,
30%].
3.3 Attempts towards the formation of 6 ± Synthesis of 8
Starting materials: 2.0mmol #1.38 g) of 3 in 100 mL of THF/
hexane #1 : 1), 4.0mmol LDA in 30mL of THF/hexane
#1 : 1). 8 was recrystallized from n-hexane. Yield: 0.50 g
#54%).
EA: C16H42Si4Sn, 465.5 g/mol, found #calc.): C 39.7 #41.28),
H 8.8 #9.09)%.
Mp.: 74±76 °C. 1H NMR #400.15 MHz, CDCl3): d = 0.17 [12 H,
Sn±Si±SiMe2], 0.39 [12 H, Sn±SiMe2, 3J#119/117Sn±1H): 24 Hz], 1.29
[36 H, Sn±C±Me3, 3J#119/117Sn±1H): 58/56 Hz]. 13C NMR #100.63 MHz,
CDCl3): d = ±3.99 [Sn±Si±SiMe2], 0.00 [Sn±SiMe2], 32.04 [Sn±C±Me3], 36.7
[Sn±C±Me3].
29Si
NMR
#59.63 MHz,
D2O-cap.):
d = ±38.0
[
2/3J#119/117Sn±29Si): 73 Hz], ±36.8 [1J#119/117Sn±29Si): 276/261 Hz]. 119Sn
NMR #111.92 MHz, D2O-cap.): d = ±151.0[ 1J#119/117Sn±29Si): 273 Hz]. MS
#M/z): 465 [M+, 20%], 408 [M+ ± tert.butyl, 90%], 351 [M+ ± 2 ´ tert.butyl,
30%], 278 [SnSi3Me5, 92%].
3,3,6,6-tetratert-butyl-1,1,2,2,4,4,5,5-octamethyl-1,2,4,5-
tetrasila-3,6-distannacyclohexane ꢀ7)
7: Mp.: 214 °C.
3.4 General Procedure for the formation of 9±11
A freshly prepared solution of 4 or 5 in 20mL of THF were
cooled to the temperature given below. The specified amount
of R2SiCl2 was solved in thf and added dropwise to the cooled
reaction mixture which was then allowed to reach room tem-
perature and stirred overnight. The solvents were evaporated
in vacuo and the solid residue was treated with n-hexane.
After filtration #G4) the solvent was removed in vacuo.
EA: C24H60Si4Sn2, 698.49 g/mol, found #calc.): C 41.6
#41.27), H 9.0#8.66)%.
1H NMR #400.15 MHz): d = 0.37 [24 H, Sn±SiMe2, 3J#119/117Sn±1H):
56 Hz], 1.28 [36 H, Sn±C±Me3, 3J#119/117Sn±1H): 24 Hz]. 29Si NMR
#59.63 MHz): d = ±33.6 [1J#119/117Sn±29Si): 272/260Hz, 2J#119/117Sn±29Si):
80Hz]. 119Sn NMR #111.92 MHz): d = ±164.2 [1J#119/117Sn±29Si): 274 Hz].
456
Z. Anorg. Allg. Chem. 2001, 627, 453±457

Syntheses and Reactivity of Stannyloligosilanes. III. Lithiated Stannasilanes
Crystallography of 7 and 11. The crystals were mounted on
the diffractometer in a sealed Lindemann capillary. The data
were collected on a Nonius MACH3 diffractometer using
Acknowledgments. The authors thank the Deutsche For-
schungsgemeinschaft #DFG), the Fond der Chemischen
Industrie #Germany) and the federal state Northrhine West-
falia for financial support. We are grateful to Prof. Dr.
K. Jurkschat for support.
Ê
graphite monochromated MoKa radiation #k = 0.71073 A) at
291 K. Three standard reflections were recorded every
60minutes and an anisotropic intensity loss up to 5.6% for
compound 7 and 4.5% for compound 11 was detected during
X-ray exposure. The structure was solved by Direct Methods
#SHELXS97) [6]. Missing atoms were located in subsequent
Difference Fourier Cycles and refined by full-matrix least-
squares of F2 #SHELXL97) [7]. All hydrogen atoms were
placed geometrically and refined using a riding model with a
References
[1] B. Costisella,
U. Englich,
I. Prass,
M. SchuÈrmann,
K. Ruhlandt-Senge, F. Uhlig, Organometallics 2000, 19,
2546.
[2] F. Uhlig, C. Kayser, R. Klassen, U. Hermann, L. Brecker,
M. SchuÈrmann, K. Ruhlandt-Senge, U. Englich, Z. Natur-
forsch. 1998, 54 b, 278.
[3] F. Uhlig, U. Hermann, M. SchuÈrmann, J. Organomet.
Chem. 1999, 585, 211.
[4] a) E. Lukevics, O. Pudowa, Main Group Metal Chemistry
1998, 21, 125; b) ebenda 1999, 22, 385.
Ê
common isotropic temperature factor #7: C±Hprim. 0.96 A,
2
2
Ê
Ê
Ê
Uiso 0.111#6) A ; 11: C±Hprim. 0.96 A, Uiso 0.173#9) A ;
2
Ê
Ê
C±HAryl 0.93 A, Uiso 0.097#12) A . Atomic scattering factors
for neutral atoms and real imaginary dispersion terms were
taken from International tables for X-ray Crystallography
[8].
[5] L. F. Tietze, T. Eichler, Reaktionen und Synthesen im
organisch-chemischen Praktikum, 2. Auflage, G. Thieme
Verlag, 1991, p. 40 .
[6] G. M. Sheldrick, Acta Crystallogr. 1990, A 46, 467.
[7] G. M. Sheldrick, SHELXL-97, University of GoÈttingen
1997.
4
Supplementary material
Full details for the structural analysis have been deposited
with the Cambridge Crystallographic Data Centre, CCDC
No. 149463 for compound 7, CCDC No. 149464 for com-
pound 11. Copies of data can be obtained free of charge on
application to The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK #Fax: int.code +#12 23) 3 36-033; e-
mail: teched@chemcrys.cam.ac.uk), and are also available in
CIF format from the authors.
[8] International Tables for X-ray Crystallography, 1992,
Vol. C, Dordrecht Kluwer Academic Publishers.
Z. Anorg. Allg. Chem. 2001, 627, 453±457
457