1,2,3,4,5,6-hexasila-7,8-distannabicyclo[2.2.2]octanes: A novel approach toward bicyclo derivatives of group 14 elements

Article abstract of DOI:10.1021/om010801q

Stannasilanes of the 1,2,3,4,5,6-hexasila-7,8-distannabicyclo[2.2.2]octanes were synthesized by the reaction of 1,4-dihalogen-substituted decamethylcyclohexasilanes with diorganodichlorostannanes in the presence of magnesium. The NMR, MS and elemental analysis were used for the characterization of the compounds. The solid-state structure of the compound was determined using x-ray crystallography.

Full text of DOI:10.1021/om010801q

986
Organometallics 2002, 21, 986-988
1,2,3,4,5,6-Hexa sila -7,8-d ista n n a bicyclo[2.2.2]octa n es: A
Novel Ap p r oa ch tow a r d Bicyclo Der iva tives of Gr ou p 14
Elem en ts†
Markus Schu¨rmann and Frank Uhlig*
Fachbereich Chemie der Universita¨t Dortmund, Anorganische Chemie II, Otto-Hahn-Strasse 6,
D-44221 Dortmund, Germany
Received September 6, 2001
Ch a r t 1: Exa m p les for Mon ocyclic Six- a n d
Seven -Mem ber ed Sta n n a sila n es (R ) Me, t-Bu , P h )
Summary: Stannasilanes of the 1,2,3,4,5,6-hexasila-7,8-
distannabicyclo[2.2.2]octane type (Me10R4Si6Sn2: R )
Me, 5; R ) Ph, 6) were synthesized by the reaction of
1,4-dihalogen-substituted decamethylcyclohexasilanes
(Si6Me10X2: X ) F, 1; X ) Cl, 2) with diorganodichlo-
rostannanes (R2SnCl2: R ) Me, 3; R ) Ph, 4) in the
presence of magnesium. Compounds 5 and 6 were
characterized by NMR, MS, and elemental analysis. The
solid-state structure of 6 was determined by X-ray
crystallography.
In tr od u ction
The chemistry of monocyclic, oligomeric silanes of the
type (R2Si)n (n ) 3-20) has been well-investigated over
the past few decades.1 In contrast, little is known about
bicyclic silanes containing only group 14 atoms in the
ring skeletons.1-3
Compound A is available as a byproduct from the
reaction of Me2SiCl2 and MeSiCl3 with sodium-potas-
sium alloy2 or as a rearrangement product in the ther-
molysis of octadecamethylbicyclo[4.4.0]decasilane (B).3
bis(di-tert-butylhydridostannyl)silanes followed by ha-
logenation and ring closure metathesis with magne-
sium.5 One-pot reactions of halosilanes with chlorostan-
nanes and magnesium yielded six-, seven-, and eight-
membered Si-Sn rings of type E-H (Chart 1), indicat-
ing that this synthetic route should also be applicable
to the synthesis of bicyclic stannasilanes.6 This paper
describes the synthesis and structure of novel com-
pounds of the bicyclo[2.2.2]octane type containing only
Sn and Si atoms in the ring skeletons.
Recently, we reported the first attempts to synthesize
group 14 bicyclo[2.2.2]octanes via multistep synthesis
starting from MeSi[SiMe2Sn(H)-t-Bu2]3.4 However, in
rather complex amine-catalyzed bond cleavage-
coupling reactions, only monocyclic Si-Sn derivatives
were accessible. During the last few years we also
reported a number of novel monocyclic compounds
exclusively containing tin and silicon atoms in the ring
skeleton (Chart 1) in order to investigate the influence
of organostannyl groups on the properties of cyclic
oligosilanes.5,6
Resu lts a n d Discu ssion
The reaction of equimolar amounts of the 1,4-dihalo-
decamethylcyclohexasilanes Me(X)Si(Me2SiSiMe2)2Si-
(X)Me (1, X ) F; 2, X ) Cl) and diorganodihalogenostan-
nanes R2SnCl2 (3, R ) Me; 4, R ) Ph) with magnesi-
um provided the 1,2,3,4,5,6-hexasila-7,8-distannabicyclo-
[2.2.2]octanes 5 and 6 in moderate yields (Scheme 1).
Compounds 5 and 6 are colorless solids which are well
soluble in aprotic, polar organic solvents. Reactions in
The four-, five-, and six-membered rings C-E were
obtained in a stepwise manner by starting from R,ω-
† Dedicated to Prof. H. Bu¨rger on the occasion of his 65th birthday.
(1) Weidenbruch, M. Chem. Rev. 1995, 95, 1479. (b) Hengge, E.;
J anoschek, R. Chem. Rev. 1995, 95, 1495. (c) The Chemistry of Organic
Silicon Compounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: Chichester,
U.K., 1998; Vol. 2, p 2177.
(2) West, R.; Indriksons, A. J . Am. Chem. Soc. 1972, 94, 6110.
(3) Ishikawa, M.; Watanabe, M.; Iyoda, J .; Ikeda, H.; Kumada, M.
Organometallics 1982, 1, 317.
(4) Costisella, B.; Englich, U.; Prass, I.; Schu¨rmann, M.; Ruhlandt-
Senge, K.; Uhlig, F. Organometallics 2000, 19, 2546.
(5) Hermann, U.; Prass, I.; Uhlig, F. Phosphorus, Sulfur, Silicon
Relat. Elem. 1997, 124/ 125, 425.
(6) (a) Kayser, C.; Klassen, R.; Schu¨rmann, M.; Uhlig, F. J . Orga-
nomet. Chem. 1998, 556, 165. (b) Uhlig, F. Manuscript in preparation.
10.1021/om010801q CCC: $22.00 © 2002 American Chemical Society
Publication on Web 02/02/2002

Notes
Organometallics, Vol. 21, No. 5, 2002 987
Sch em e 1. Rea ction s of
1,4-Dih a locycloh exa sila n es w ith R2SiCl2 in th e
P r esen ce of Ma gn esiu m
F igu r e 1. General view (SHELXTL-PLUS) of one of the
two independent molecules of 6, showing 30% probability
displacement ellipsoids and the atom numbering.
a molar ratio of silane to stannane of 1.5:1 increased
the yields of 5 and 6 to 35%. If the exact stoichiometric
amounts of 2:1 were used, unidentified byproducts
without Si-Sn moieties were observed, preventing the
isolation of 5 and 6 from the reaction mixtures.
The starting materials 1 and 2 were used as a 1:1
mixture of the cis/trans isomers. We have no experi-
mental evidence as to whether both or only one of the
isomers react toward the cage-like compounds 5 and 6.
However, it is well-known from the literature that cis/
trans mixtures of 2 can be converted nearly quantita-
tively into bicyclo[2.2.1]heptane derivatives.7,8
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Deta ils for 6
formula
fw
cryst syst
cryst size, mm
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C34H50Si6Sn2
864.66
triclinic
0.40 × 0.12 × 0.10
P1h
10.639(1)
19.879(1)
20.708(1)
94.402(1)
102.718(1)
94.991(1)
4256.7(5)
4
Z
F
calcd, Mg/m3
1.349
1.363
1752
µ, mm-1
F(000)
θ range, deg
2.95-25.70
-11 e h e 11
-24 e k e 24
-25 e l e 24
51 901
91.7
14 853/0.052
6933
index ranges
The tin-silicon moieties in compounds 5 and 6 were
no. of rflns collected
completeness to θmax, %
no. of indep rflns/Rint
no. of rflns obsd with I > 2σ(I)
no. of refined params
GOF(F2)
confirmed by NMR experiments, with coupling con-
1
stants for J (119Sn-117Sn) at 1505 Hz (5) and 1170 Hz
(6). These values agree well with 1J (119Sn-117Sn) for
759
0.828
monocyclic rings of type E.6 The J (119Sn-29Si) (243 Hz
1
R1(F) (I > 2σ(I))
0.0389
0.0678
0.001
0.465/-0.428
(5), 238 Hz (6)) are around 100 Hz smaller than in the
related compounds of types E and F . These differences
might be explained by the different environments of the
wR2(F2) (all data)
(∆/σ)max
largest diff peak/hole, e/Å3
1
2
silicon atom. J (29Si-29Si) and J (29Si-29Si) have been
determined at 50.5 and 10 Hz for 5 and 49.5 and 10 Hz
for 6 and are therefore significantly smaller (8 and 3
Hz) than in monocyclic cyclohexasilane derivatives 1
and 2. The lack of comparable data does not allow a
complete discussion.
tural features of compound 6 compare favorably with
those of other heteroatom-substituted silabicyclo[2.2.2]-
octanes,9 cyclic distannanes,10 or the diphenyltin deriva-
tive of F .6
The synthesis of the bicyclo[2.2.2]octane compounds
5 and 6 indicate not only the potentials but also the
limitations of one-pot reactions between halogen silanes
and chlorostannanes in the presence of magnesium.
The bicyclooctane derivative 6, depicted in Figure 1,
crystallizes with two independent molecules in the unit
cell, of which only one is shown. Crystallographic data
and selected interatomic parameters are listed in Tables
1 and 2, respectively. The central tin-silicon backbone
consists of Si4Sn2 and Si6 rings each displaying a
“twisted boat” conformation (Figure 1).
The two independent molecules differ only slightly in
their bond lengths and angles. The tin and silicon atoms
display a slightly distorted tetrahedral geometry, with
bond distances of 2.7814(5) and 2.7866(5) Å for Sn-Sn
and 2.354(2) and 2.336(2) Å for Si(1)-Si(4). The struc-
(7) Wojnowski, W.; Dreczewski, B.; Herman, A.; Peters, K.; Peters,
E.-M.; von Schnering, H. G. Angew. Chem. 1985, 97, 978.
(8) Spielberger, A.; Gspaltl, P.; Siegl, H.; Hengge, E.; Gruber, K. J .
Organomet. Chem. 1995, 499, 241.
(9) (a) Winkler, U.; Schieck, M.; Pritzkow, H.; Driess, M.; Hyla-
Kryspin, I.; Lange, H.; Gleiter, R. Chem. Eur. J . 1997, 3, 874. (b)
Hassler, K.; Kollegger, G. M.; Siegl, H.; Klintschar, G. J . Organomet.
Chem. 1997, 533, 51.
(10) Puff, H.; Breuer, B.; Gehrke-Brinkmann, G.; Kind, P.; Reuter,
H.; Schuh, W.; Wald, W.; Weidenbru¨ck, G. J . Organomet. Chem. 1989,
363, 265.

988 Organometallics, Vol. 21, No. 5, 2002
Notes
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Tw o In d ep en d en t Molecu les of 6 (6′)
(b) The starting materials used were 3.71 g (10 mmol) of 1
and 3.3 g (15 mmol) of 3. Recrystallization from n-hexane/Et2O
(1:1) yielded 2.16 g (35%) of 5 as a colorless solid.
6
6′
119Sn NMR (111.92 MHz, CDCl3): δ -227.9, 1J (119Sn-117Sn)
)
1505 Hz. 29Si NMR (59.63 MHz, CDCl3):
δ -80.9
Bond Lengths
(1J (119Sn-29Si) ) 243 Hz, 2J (119Sn-29Si) ) 94 Hz, SiMe), -37.6
(2J (119Sn-29Si) ) 58 Hz, 3J (119Sn-29Si) ) 38 Hz, SiMe2),
1J (29Si-29Si) ) 50.5 Hz, 2J (29Si-29Si) ) 10 Hz.13C NMR (100.63
MHz, C6D6): δ -9.8 (2J (119Sn-13C) ) 32 Hz, SiMe), -2.8, -3.1
(3J (119Sn-13C) ) 41 Hz, SiMe2), -5.6 (1J (119Sn-13C) ) 195 Hz,
Sn(1)-Sn(2)
Sn(1)-Si(1)
Sn(2)-Si(6)
Si(1)-Si(2)
Si(2)-Si(3)
Si(3)-Si(6)
Si(4)-Si(5)
Si(5)-Si(6)
Si(1)-Si(4)
Sn(2)-C(31)
Sn(2)-C(41)
Sn(1)-C(11)
Sn(1)-C(21)
2.7814(5) Sn(1′)-Sn(2′)
2.573(1) Sn(1′)-Si(1′)
2.576(1) Sn(2′)-Si(6′)
2.341(2) Si(1′)-Si(2′)
2.349(2) Si(2′)-Si(3′)
2.346(2) Si(3′)-Si(6′)
2.360(2) Si(4′)-Si(5′)
2.345(2) Si(5′)-Si(6′)
2.354(2) Si(1′)-Si(4′)
2.147(5) Sn(2′)-C(31′)
2.153(5) Sn(2′)-C(41′)
2.131(5) Sn(1′)-C(11′)
2.146(5) Sn(1′)-C(21′)
2.7866(5)
2.589(1)
2.571(1)
2.353(2)
2.362(2)
2.337(2)
2.350(2)
2.345(2)
2.336(2)
2.152(5)
2.146(5)
2.141(5)
2.132(5)
SnMe2). H NMR (400.13 MHz, CDCl3): δ 0.41 (2J (119Sn-1H)
1
) 36 Hz, 12H 2 × SnMe2), 0.37 (3J (119Sn-1H) ) 24 Hz, 6H,
SiMe), 0.35 (12H, 2 × SiMe2). Mp: 208-210 °C. Molecular mass
determination (CHCl3, 20 mg mL-1): 612 g mol-1. Anal. Calcd
for C14H42Si6Sn2 (616.41): C, 27.28; H, 6.87. Found: C, 27.1;
H, 6.6, MS: m/z 616 (M+/80%), 601 (M+ - Me/10%), 586 (M+
- 2 Me/5%), 318 (Si6Me10/100%).
Bond Angles
7,7,8,8-Tetr a p h en yld eca m eth yl-1,2,3,4,5,6-h exa sila -7,8-
d ista n n a bicyclo[2.2.2]octa n e, Me10P h 4Si6Sn 4 (6). (a) The
starting materials were 4.04 g (10 mmol) of 2 and 3.43 g (10
mmol) of 4. Recrystallization from CHCl3/Et2O (1:1) yielded
1.29 g (15%) of 6 as a colorless solid.
(b) The starting materials were 4.24 g (11 mmol) of 1 and
5.5 g (16 mmol) of 4. Recrystallization from CHCl3/Et2O (1:1)
gave 2.59 g (27%) of 6 as a colorless solid.
C(11)-Sn(1)-C(21) 103.7(2) C(11′)-Sn(1′)-C(21′) 102.9(2)
C(11)-Sn(1)-Si(1) 109.1(1) C(11′)-Sn(1′)-Si(1′) 111.3(1)
C(21)-Sn(1)-Si(1) 112.0(2) C(21′)-Sn(1′)-Si(1′) 110.6(2)
C(11)-Sn(1)-Sn(2) 113.6(2) C(11′)-Sn(1′)-Sn(2′) 111.8(1)
C(21)-Sn(1)-Sn(2) 114.3(1) C(21′)-Sn(1′)-Sn(2′) 115.3(2)
Si(1)-Sn(1)-Sn(2) 104.32(3) Si(1′)-Sn(1′)-Sn(2′) 105.03(3)
C(1)-Si(1)-Si(2)
C(1)-Si(1)-Si(4)
Si(2)-Si(1)-Si(4)
C(1)-Si(1)-Sn(1)
108.4(2) C(1′)-Si(1′)-Si(2′)
112.6(2) C(1′)-Si(1′)-Si(4′)
108.37(7) Si(2′)-Si(1′)-Si(4′)
111.0(2) C(1′)-Si(1′)-Sn(1′)
108.0(2)
111.3(2)
109.86(8)
112.3(2)
119Sn NMR (149.21 MHz, CDCl3): δ -206.1, 1J (119Sn-117Sn)
)
1170 Hz. 29Si NMR (79.49 MHz, CDCl3):
δ -74.4
Si(2)-Si(1)-Sn(1) 107.35(6) Si(2′)-Si(1′)-Sn(1′) 108.83(7)
Si(4)-Si(1)-Sn(1) 108.94(6) Si(4′)-Si(1′)-Sn(1′) 106.51(7)
(1J (119Sn-29Si) ) 238 Hz, 2J (119Sn-29Si) ) 97 Hz, SiMe), -37.1
(2J (119Sn-29Si) ) 53 Hz, 3J (119Sn-29Si) ) 40 Hz, SiMe2),
1J (29Si-29Si) ) 49.5 Hz, 2J (29Si-29Si) ) 10 Hz. 13C NMR
(100.63 MHz, C6D6): δ 139.8(1J (119Sn-13C) ) 298 Hz, Ci), 138.4
(2J (119Sn-13C) ) 41 Hz, Co), 128.0 (3J (119Sn-13C) ) 42 Hz, Cm),
127.7 (Cp), -10.7 (2J (119Sn-13C) ) 34 Hz, SiMe), -2.3, -2.5
There is no evidence for the formation of the thermo-
dynamically less favored, more strained bicyclo[2.2.1]-
heptane 7 (Scheme 1), but the reactions are well suited
for the formation of thermodynamically favored products
such as six-, seven-, or eight-membered mono- and
bicyclic Si-Sn rings.
1
(3J (119Sn-13C) ) 39 Hz, SiMe2), H NMR (400.13 MHz, C6D6):
δ 7.75 (3J (119Sn-1H) ) 45 Hz, d, 8H, SnPh), 7.18 (m, 12H,
SnPh), 0.64 (3J (119Sn-1H) ) 23 Hz, SiMe), 0.37, 0.30 (SiMe2).
Mp: 168-170 °C, Anal. Calcd for C34H50Si6Sn2 (864.69): C,
47.23; H, 5.82, Found: C, 46.8, H, 5.7, MS: m/z 863 (M+/100%),
848 (M+ - Me/3%), 786 (M+ - Ph/10%), 333 (Si6Me10/90%),
272 (SnPh2/60%).
Exp er im en ta l Section
Gen er a l Meth od s. 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 1,4-dihalodecamethylcyclohexasi-
lanes 1 and 2 were prepared according to published proce-
dures.11 All other chemicals were obtained commercially. 1H
and 13C NMR spectra were recorded using a Bruker DPX 400
spectrometer (solvent CDCl3 or C6D6, internal reference Me4-
Si). 29Si and 119Sn NMR spectra were recorded using a Bruker
DPX 400 spectrometer (solvent CDCl3 or C6D6, internal refer-
ence Me4Si or Me4Sn, respectively) or a Bruker DRX 300
spectrometer (solvent hexane or THF with D2O capillary,
internal reference Me4Si or Me4Sn, respectively). The xJ (29Si-
29Si) coupling constants were determined as described previ-
ously.12 MS analyses were recorded using a MAT 8200.
Molecular mass determinations were performed with a Knauer
osmometer at 56 °C. Elemental analyses were performed on a
LECO-CHNS-932 analyzer.
Cr ysta llogr a p h y. The data of 6 were collected to a θ value
of 25.70° with 360 frames via ω-rotation (∆/ω ) 1°) with a 60
s exposure time per frame on a Nonius KappaCCD diffracto-
meter (λ ) 0.71073 Å) and was corrected for LP but not for
absorption effects. The structure was solved by direct methods
SHELXS97.14 Refinement used SHELXL9715 full-matrix least-
squares methods. The H atoms were placed on geometrically
calculated positions using a riding model and refined with a
common isotropic temperature factor for aliphatic and aro-
matic H atoms.
Ack n ow led gm en t. We thank the Deutsche Fors-
chungsgemeinschaft (DFG), the Fonds der Chemischen
Industrie (Germany), and the federal state Northrhine
Westfalia for financial support. We are grateful to Prof.
Dr. K. J urkschat for his interest in this work.
Gen er a l P r oced u r e. In a 250 mL Schlenk tube 10 mmol
of 1 or 2 and 10-20 mmol of 3 or 4 were dissolved in 100 mL
of THF. A 2 g amount (83 mmol, excess) of magnesium
(activated with iodine13) was added. The resulting reaction
mixture was stirred at room temperature for 3 days (1) or 6
days (2). After evaporation of the THF the resulting residue
was extracted twice with 50 mL portions of a n-hexane/Et2O
(1:1) mixture. The extracts were filtered through a frit (G3) to
remove magnesium salts. After evaporation of the filtrate, the
crude products were purified by recrystallization.
Te t r a d e ca m e t h yl-1,2,3,4,5,6-h e xa sila -7,8-d ist a n n a -
bicyclo[2.2.2]octa n e, Me14Si6Sn 4 (5). (a) The starting ma-
terials used were 3.71 g (10 mmol) of 1 and 2.2 g (10 mmol) of
3. Recrystallization from n-hexane/Et2O (1:1) gave 1.23 g (20%)
of 5 as colorless solid.
Su p p or tin g In for m a tion Ava ila ble: This material is
available free of charge via the Internet at http://pubs.acs.org.
OM010801Q
(11) Mitter, F. K.; Hengge, E. J . Organomet. Chem. 1987, 332, 47-
52.
(12) Uhlig, F.; Kayser, C.; Klassen, R.; Hermann, U.; Brecker, L.;
Schu¨rmann, M.; Ruhlandt-Senge, K.; Englich, U. Z. Naturforsch. 1999,
54b, 278.
(13) A 10 g amount of magnesium was heated with 0.2 g iodine
under inert conditions for 5 min up to 100 °C. After the mixture was
cooled to room temperature, the magnesium was used without further
purification.
(14) Sheldrick, G. M. SHELXS-97. Acta Crystallogr. 1990, A46, 467.
(15) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1997.