Extending distannoxane double ladders using rigid spacers: A double ladder with eight chiral tin atoms- and a twist!

Article abstract of DOI:10.1021/om0105627

The new bulky silicon-containing ditin precursor p-(RCl₂SnCH₂SiMe₂)₂C₆H ₄ (R = CH₂SiMe₃ (4)) has been synthesized and further reacted to form a unique double ladder {[p-(R(Cl)SnCH₂SiMe₂)₂C₆H₄ ]O}₄ (6). The two layers within 6 are twisted with respect to one another, resulting in a helical motif and a total absence of molecular symmetry so that there are eight chiral tin atoms within the system. The structure is compared to the double ladder {[m-(R(Cl)SnCH₂CH₂)₂C₆H₄] O}₄ (11), which was prepared from the less sterically demanding ditin precursor m-(RCl₂SnCH₂CH₂)₂C₆H ₄ (10). The two layers within 11 are parallel, and the molecule contains only two kinds of tin atom.

Full text of DOI:10.1021/om0105627

Organometallics 2002, 21, 647-652
647
Exten d in g Dista n n oxa n e Dou ble La d d er s Usin g Rigid
Sp a cer s: A Dou ble La d d er w ith Eigh t Ch ir a l Tin
Atom ssa n d a Tw ist!
Dainis Dakternieks,* Andrew Duthie, and Bernhard Zobel
Centre for Chiral and Molecular Technologies, Deakin University,
Geelong, Victoria 3217, Australia
Klaus J urkschat* and Markus Schu¨rmann
Lehrstuhl fu¨r Anorganische Chemie II der Universita¨t Dortmund,
D-44221 Dortmund, Germany
Edward R. T. Tiekink*,†
Department of Chemistry, University of Adelaide, South Australia 5005, Australia
Received J une 25, 2001
The new bulky silicon-containing ditin precursor p-(RCl2SnCH2SiMe2)2C6H4 (R ) CH2-
SiMe3 (4)) has been synthesized and further reacted to form a unique double ladder {[p-
(R(Cl)SnCH2SiMe2)2C6H4]O}4 (6). The two layers within 6 are twisted with respect to one
another, resulting in a helical motif and a total absence of molecular symmetry so that there
are eight chiral tin atoms within the system. The structure is compared to the double ladder
{[m-(R(Cl)SnCH2CH2)2C6H4]O}4 (11), which was prepared from the less sterically demanding
ditin precursor m-(RCl2SnCH2CH2)2C6H4 (10). The two layers within 11 are parallel, and
the molecule contains only two kinds of tin atom.
In tr od u ction
chiral transformations, probably because no suitable
chiral distannoxanes have yet been reported. Further-
more, distannoxanes undergo extensive dissociation in
solution, a property that also reduces their potential as
chiral information transfer reagents.19-23 By contrast,
double and triple ladders undergo fewer dissociation
reactions in solution, but, significantly, in these cases
chiral information is retained at the tin centers.4 A key
motivation for our investigations has been the synthesis
of new double ladders that have little or no symmetry
as well as to increase the size of the interlayer region.24
Such new molecular tin-oxo species hold considerable
potential both for chiral catalysis and for genuine host-
guest chemistry.
Among the many and varied applications of organotin
compounds, their use in catalysis continues to attract
considerable attention.1 In this context we have recently
reported examples of double and triple ladders (A, R )
alkyl, X ) Cl, OAc; B, X ) Cl, R ) CH2SiMe3).2-4 Their
structures are related to the well-known single ladders
(distannoxanes) C (R ) alkyl, aryl, X ) range of anions),
which are useful as mild Lewis acid catalysts in a
variety of organic reactions.5-18 Interestingly, distan-
noxanes have not yet found utility in synthesis requiring
† Present address: Department of Chemistry, National University
of Singapore, Singapore 117543.
(1) Beckmann, J .; J urkschat, K.; Kaltenbrunner, U.; Rabe, S.;
Schu¨rmann, M.; Dakternieks, D.; Duthie, A.; Mueller, D. Organome-
tallics 2000, 19, 4887.
(12) Orita, A.; Mitsutome, A.; Otera, J . J . Org. Chem. 1998, 63,
2420.
(2) Dakternieks, D.; J urkschat, K.; Schollmeyer, D.; Wu, H. Orga-
nometallics 1994, 13, 4121.
(13) Otera, J .; Yano, T.; Himeno, Y.; Nozaki, H. Tetrahedron Lett.
1986, 27, 4501.
(14) Otera, J .; Nozak, H. Tetrahedron Lett. 1986, 27, 5743.
(15) Otera, J .; Kawada, K.; Yano, T. Chem. Lett. 1996, 225.
(16) Houghton, R. P.; Mulvaney, A. W. J . Organomet. Chem. 1996,
517, 107.
(17) Houghton, R. P.; Mulvaney, A. W. J . Organomet. Chem. 1996,
518, 21.
(18) Suciu, E. N.; Kuhlmann, B.; Knudsen, G. A.; Michaelson, R. C.
J . Organomet. Chem. 1998, 556, 41.
(19) Maeda, Y.; Okawara, R. J . Organomet. Chem. 1967, 10, 247.
(20) Yano, T.; Nakashima, K.; Otera, J .; Okawara, R. Organome-
tallics 1985, 4, 1501.
(21) Gross, D. C. Inorg. Chem. 1989, 28, 2355.
(22) Primel, O.; Llauro, M.-F.; Petiaud, R.; Michel, A. J . Organomet.
Chem. 1998, 558, 19.
(3) Mehring, M.; Schu¨rmann, M.; Reuter, H.; Dakternieks, D.;
J urkschat, K. Angew. Chem., Int. Ed. Engl. 1997, 36, 1112.
(4) (a) Mehring, M.; Schu¨rmann, M.; Paulus, I.; Horn, D.; J urkschat,
K.; Orita, A.; Otera, J .; Dakternieks, D.; Duthie, A. J . Organomet.
Chem. 1999, 574, 176. (b) Mehring, M.; Paulus, I.; Zobel, B.; Schu¨r-
mann, M.; J urkschat, K.; Duthie, A.; Dakternieks, D. Eur. J . Inorg.
Chem. 2001, 153.
(5) Otera, J .; Yano, T.; Okawara, R. Organometallics 1986, 5, 1167.
(6) Otera, J . Chem. Rev. 1993, 93, 1449.
(7) Otera, J .; Ioka, S.; Nozaki, H. J . Org. Chem. 1989, 54, 4013.
(8) Otera, J .; Yano, T.; Kawabata, A.; Nozaki, H. Tetrahedron Lett.
1986, 27, 2383.
(9) Otera, J .; Dan-Oh, N.; Nozaki, H. J . Chem. Soc., Chem. Commun.
1991, 1742.
(10) Otera, J .; Danoh, N.; Nozaki, H. J . Org. Chem. 1991, 56, 5307.
(11) (a) Otera, J . In Advances in Detailed Reaction Mechanisms;
Coxan, J . M., Ed.; J AI Press Inc.: London, 1994; Vol. 3, p 67. (b) Otera,
J .; Danoh, N.; Nozaki, H. Tetrahedron 1992, 48, 1449.
(23) Dakternieks, D.; J urkschat, K.; van Dreumel, S.; Tiekink, E.
R. T. Inorg. Chem. 1997, 36, 2023.
(24) Schulte, M.; Schu¨rmann, M.; Dakternieks, D.; J urkschat, K.
Chem. Commun. (Cambridge) 1999, 1291.
10.1021/om0105627 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 01/24/2002

648 Organometallics, Vol. 21, No. 4, 2002
Dakternieks et al.
Double ladders are obtained by the controlled hy-
drolysis or oxygenolysis of precursors containing two tin
atoms linked by appropriate organic spacers. Recently,
we found that incorporation of a Me2Si group at a â
position to tin in ditin precursors gives rise to novel
structures, probably as a consequence of the steric
requirements of the silicon-bound Me groups.3,4,24 With
this in mind we designed and synthesized new spacers
including one containing a rigid phenylene group linked
to two tin atoms via Me2Si units. This modification leads
to the first example of a double ladder containing eight
different chiral tin centers. Particularly interesting is
that the new spacer group confers a novel helical motif
on the overall molecular geometry. The results of this
study are reported herein.
F igu r e 1. Molecular structure and atomic numbering
scheme for 6; hydrogen atoms have been omitted for clarity.
Carbon atoms are indicated by number only.
Resu lts a n d Discu ssion
noxanes likely to adopt double ladder structures (and/
or other oligomers) in which chloride is partially re-
placed by hydroxide. There was no significant change
in spectral appearance of the 119Sn NMR spectrum
measured in toluene at 80 °C. Attempts to obtain a solid
state 119Sn NMR spectrum for 6′ were not successful.
From this material a single crystal, 6, suitable for X-ray
diffraction was obtained.
Reaction of the chloromethyldimethylsilylated ben-
zene, 1, with NaSnPh3 affords the triphenyltin-substi-
tuted derivative 2 as colorless crystals (eq 1).
p-(ClCH2SiMe2)2C6H4
+
1
liq. NH3
p-(Ph SnCH SiMe ) C H
2 Ph3SnNa -2 NaCl8
(1)
3
2
2 2
6
4
The X-ray structure analysis of 6 (Figure 1) was
modeled as the chloride species (see below) and estab-
lishes the double ladder motif as seen in previous
examples, but contrary to previous structures of this
type, there is no center of inversion. Solutions of 6′ in
CH2Cl2 show no optical rotation, and it appears that
isolation of 6 is an example of fortuitous spontaneous
crystallization of one enantiomer. The structure may be
described as being a construction of two ladders, of the
type shown in C, linked by -CH2SiMe2C6H4SiMe2CH2-
spacers and with the remaining tin-bound groups being
CH2SiMe3. Each of the two Sn4O2Cl4 planes are nearly
planar (mean deviations 0.13 and 0.14 Å, respectively)
and approximately parallel, forming a dihedral angle
of 7.7°. The tin atoms exist in distorted trigonal bipy-
ramidal geometries with trigonal C2O and axial O, Cl
donor sets for Sn(1), Sn(2), Sn(5), and Sn(6) and trigonal
C2O and axial Cl, Cl donor sets for the remaining tin
atoms. The geometric parameters for 6 are largely as
expected and are not discussed in detail.
2
Reaction of compound 2 with iodine gives p-(Ph2-
ISnCH2SiMe2)2C6H4, which was further reacted with
ClMgR (R ) CH2SiMe3) to yield p-(Ph2RSnCH2-
SiMe2)2C6H4, 3. The phenyl groups in the tetraorganotin
derivative 3 were replaced by chlorine upon treatment
with HgCl2 to yield the tetrachloro-substituted ditin
derivative p-(RCl2SnCH2SiMe2)2C6H4, 4, which in turn
was reacted with sodium hydroxide. The product of the
latter reaction was formulated as the tetrahydroxy-
substituted organotin compound p-[R(OH)2SnCH2-
SiMe2]2C6H4, 5.
Reaction of the organotin chloride 4 with the spacer-
bridged bis-diorganotin dihydroxide 5 provided, after the
workup procedure, a colorless solid, hereafter referred
to as compound 6′, the elemental analysis of which is
in agreement with the empirical formula C80H169Cl7O5-
Si16Sn8. The IR spectrum of 6′shows a ν(OH) at 3652
cm-1, and the 119Sn NMR (C6D6/CD2Cl2, 5:1) spectrum
showed at least 26 clearly defined resonances in the
region usually associated with tetraorganodistannox-
anes adopting ladder-type structures (δ -55 to -160
ppm). The number of signals suggests the existence in
solution of a statistical mixture of tetraorganodistan-
A close inspection of the Sn-Cl separations in the
X-ray structure of 6 supports the interpretation, as
given above, for the large number of 119Sn NMR reso-
nances measured for the bulk material. The Sn-Cl
distances of the Sn(5)-Sn(8) distannoxane are system-

Extending Distannoxane Double Ladders
Organometallics, Vol. 21, No. 4, 2002 649
Sch em e 1
atically shorter than those within the other distannox-
ane, indicating the possibility of (partial) substitution
of chloride for hydroxide. Attempts at refinement with
partial occupancy did not result in a significantly better
model, but it is noted that the structure analysis is less
than optimal (see Experimental Section) and such small
changes in a large structure of this type and quality
would not be readily detectable.
F igu r e 2. Molecular structure and atomic numbering
scheme for the double ladder in 11‚toluene; hydrogen atoms
have been omitted for clarity.
Of particular interest in the structure of 6 is the
chirality adopted by the overall molecule. This is
manifested in the twist between the top and bottom
distannoxane “faces” that results in an overall helical
arrangement for the molecule.
silicon-bound methyl groups are directed outside of the
cavity. In turn, this arrangement forces a preferred ori-
entation of the spacers in order to minimize repulsions
between the silicon-bound methyl substituents. So,
rather than having the spacers spanning two ap-
proximately superimposable Sn4O2 units in an extended
conformation resulting in the formation of a molecular
box, as in 11, the spacers in 6 are forced into an arrange-
ment linking two Sn4O2 units of differing orientations.
Thus, the result of the conformational requirements of
the spacer ligands is to introduce a twist in the molecule
as a whole, leading to molecular chirality, i.e., one face
of the molecular box in 11 is rotated relative to the other
in 6. The magnitude of this twist can be estimated by
calculating the relative orientation of the central Sn4O2
cores, which in 6 approximates 31°. Views highlighting
the relative distribution of the spacer groups and central
cores for each of 6 and 11 are shown in Figure 3. From
this diagram it is evident that the distribution of the
spacer groups is symmetric in 11 and far from sym-
metric in 6. The sequence of dihedral angles formed
between adjacent aromatic rings gives a quantitative
measure of the deviation from a centrosymmetric dis-
tribution of these groups. Thus, the dihedral angles
formed between the C(4)-C(9) and C(28)-C(33) rings
is 116.4°, C(28)-C(33) and C(16)-C(21) 61.2°,
C(16)-C(21) and C(40)-C(45) 53.8°, and C(40)-C(45)
and C(4)-C(9) 75.4°. The comparable sequence of angles
for the structure of centrosymmetric 11 is 69.5°.
Crystals of another distannoxane, 11, containing the
meta -(CH2)2C6H4(CH2)2- spacer, were also obtained
(Scheme 1), and its crystal structure was determined.
The crystallographically determined structure of 11,
characterized as the toluene solvate, is shown in Figure
2; the crystallographic unit cell comprises two double
ladders, each disposed about a center of inversion, and
four disordered toluene molecules (see Experimental
Section). The structure of 11 resembles closely that
found for related species, including that of 6. To a first
approximation the Sn4Cl4O2 face of the molecule is
planar with the range of deviations from their least-
squares plane being 0.0143(3) Å for Sn(1) to -0.174(3)
Å for O(1). The average separation between the two
faces (from symmetry the dihedral angle is 0°) is
calculated to be 10.6 Å. The tin atoms exist in distorted
trigonal bipyramidal geometries with trigonal C2O and
axial O, Cl donor sets for Sn(1) and Sn(2), and trigonal
C2O and axial Cl, Cl donor sets for the Sn(3) and Sn(4).
As for 6, a detailed discussion of the derived interatomic
parameters is not warranted. The structure, including
its centrosymmetricity, resembles that observed previ-
ously for related systems2-4 but clearly contrasts the
chiral distannoxane observed for 6. In the following
discussion, an argument based on steric reasons is
proposed to account for the unique helical motif found
in 6.
Thus, while previous examples of double ladder struc-
tures (A) may be thought of as being comprised of two
enantiomeric halves, this description is not valid for 6,
which may be described as adopting a helical motif.
As can be seen from Figure 1, the tin atoms in 6 lie
on opposite sides of each spacer, as for 11, and the

650 Organometallics, Vol. 21, No. 4, 2002
Dakternieks et al.
NMR (59.6 MHz, CDCl3): δ -2.9 [2J (117/119Sn-29Si) ) 21,
SiMe2]. 119Sn{1H} NMR (111.85 MHz, CDCl3): δ -89.0 [1J (13C-
119Sn) ) 506]. Anal. Calcd for C48H50Si2Sn2: C 62.63, H 5.47.
Found: C 62.81, H 5.59.
Syn th esis of Bis{[(tr im eth ylsilylm eth yl)d ip h en yl-
sta n n ylm eth yl]d im eth ylsilyl}ben zen e, 3. To a magneti-
cally stirred solution (0 °C) of 2 (7.8 g, 8.49 mmol) in CH2Cl2
(80 mL) was added I2 (4.275 g, 16.95 mmol) in small portions
over 30 min. The reaction mixture was stirred for 2 h, the
solvent removed in vacuo, and the resulting yellow oil kept
for 3 h at 130 °C and 10-3 Torr to remove all volatile
byproducts. The oily residue (8.64 g, 8.49 mmol) was dissolved
in THF (120 mL) and added dropwise at room temperature
during 1 h to a Grignard solution prepared from chlorometh-
yltrimethylsilane (3.00 g, 24.45 mmol) and Mg (588 mg, 24.48
mmol) in THF (120 mL). The reaction mixture was refluxed
overnight and the THF removed in vacuo. To the resulting
colorless solid was added Et2O and the suspension hydrolyzed
with saturated NH4Cl solution. The organic layer was washed
twice with water and dried over Na2SO4. After filtration the
organic solvent was evaporated in vacuo and the resulting
yellow oil kept for several hours at 130 °C and 10-3 Torr to
remove all volatile byproducts to give 7.32 g crude product
that could be used without further purification. 13C{1H}
F igu r e 3. Views of the double ladders in 6 and 11‚toluene,
highlighting the relative distribution of the spacer groups.
Terminal methyl groups and hydrogen atoms have been
omitted for clarity.
We are currently investigating the influence of other
R groups and the variation of the bridging spacers on
the twist of the double ladder structure.
Exp er im en ta l Section
NMR (75.44 MHz, CDCl3):
δ )
-4.6 [1J (117/119Sn-13C)
247/258, 1J (29Si-13C) ) 49, CH2], -3.8 [1J (117/119Sn-13C) ) 257/
All solvents were dried and purified by standard procedures.
NMR spectra were obtained using a Varian 300 MHz Unity
1
269, J (29Si-13C) ) 47, CH2], -0.0 [1J (29Si-13C) ) 53, SiMe3],
1.6 [1J (29Si-13C)
)
51, SiMe2], 128.2 (Cm), 128.5 (Cp),
1
Plus NMR spectrometer. H, 13C, and 119Sn chemical shifts δ
132.6 (CoSi), 136.3 [2J (117/119Sn-13C)
)
38, Co], 141.2
are given in ppm and are referenced against Me4Si and
Me4Sn, respectively. Uncorrected melting points were deter-
mined on a Kofler hot stage. Microanalyses were performed
using a CE 1106 elemental analyzer.
[1J (117/119Sn-13C)
)
458/479, CI], 141.5 (CiSi). 119Sn{1H}
NMR (111.85 MHz, CDCl3): δ -48.9 [1J (13C-119Sn) ) 480,
1J (13C-119Sn) ) 269].
Syn th esis of Bis{[(tr im eth ylsilylm eth yl)d ich lor o-
sta n n ylm eth yl]d im eth ylsilyl}ben zen e, 4. To a magneti-
cally stirred solution (0 °C) of 3 (7.32 g, 7.80 mmol) in acetone
(70 mL) was added dropwise a solution of HgCl2 (8.46 g, 31.20
mmol) in acetone (70 mL) over 30 min. The reaction mixture
was stirred overnight and the resulting precipitate (PhHgCl)
filtered off. After removing the acetone in vacuo Et2O (120
mL) was added and the suspension stirred for 10 min. The
PhHgCl was removed by filtration and the organic solvent
evaporated in vacuo to give 5.4 g of crude product that was
recrystallized from Et2O/hexane to give 4 as a colorless solid
(3.15 g, 52% yield, mp 87-90 °C). 1H NMR (299.98 MHz,
CDCl3): δ 0.12 (s, 9H, SiMe3), 0.49 (s, 6H, SiMe2), 0.52 [s, 2H,
Syn th esis of 1,4-Bis(ch lor om eth yld im eth ylsilyl)ben -
zen e, 1. A solution of the di-Grignard of 1,4-dibromobenzene
(24.12 g, 84.77 mmol) in THF (700 mL) was added during 2.5
h via a cannula to a magnetically stirred solution of ClSiMe2-
CH2Cl (22.28 mL, 24.20 g, 169.3 mmol) in THF (100 mL).25
The resulting reaction mixture was stirred overnight and
hydrolyzed with saturated NH4Cl solution. After removing the
THF in vacuo Et2O was added; the organic layer was separated
and dried over Na2SO4. The Et2O was evaporated, and the
remaining crude product (20.5 g yellow oil) was recrystallized
from hexane to give 1 as a colorless solid (11.4 g, 46% yield,
1
mp 56-58 °C). H NMR (299.98 MHz, CDCl3): δ 0.40 (s, 3H,
SiMe2), 2.93 (s, 1H, CH2), 7.54 (s, 1H, C6H4). 13C{1H} NMR
(75.44 MHz, CDCl3): δ -4.6 [1J (29Si-13C) ) 55, SiMe2], 30.2
[1J (29Si-13C) ) 53, CH2], 133.2 (Co), 137.8 (Ci). 29Si{1H} NMR
2
2J (117/119Sn-1H) ) 88/92, CH2], 1.03 [s, 2H, J (117/119Sn-1H) )
90/94, CH2], 7.57 (s, 2H, C6H4). 13C{1H} NMR (75.44 MHz,
CDCl3): δ -0.6 [1J (29Si-13C) ) 55, 3J (117/119Sn-13C) ) 22,
(59.6 MHz, CDCl3): δ -2.9 (SiMe2). Anal. Calcd for C12H20
Cl2Si2: C 49.49, H 6.87. Found: C 49.63, H 6.94.
-
3
SiMe3], 1.0 [1J (29Si-13C) ) 52, J (117/119Sn-13C) ) 27, SiMe2],
12.5 [1J (117/119Sn-13C) ) 325/340, 1J (29Si-13C) ) 45 CH2],
12.6 [1J (117/119Sn-13C) ) 309/323, 1J (29Si-13C) ) 46, CH2], 133.1
(Co), 140.3 (Ci). 29Si{1H} NMR (59.6 MHz, CDCl3): δ -4.2
[2J (117/119Sn-29Si) ) 30, SiMe2], 1.5 [2J (117/119Sn-29Si) ) 40,
SiMe3]. 119Sn{1H} NMR (111.85 MHz, CDCl3): δ 140.9. Anal.
Calcd for C20H42Cl4Si4Sn2: C 31.05, H 5.43. Found: C 31.28,
H 5.54.
Syn th esis of Bis[(tr ip h en ylsta n n ylm eth yl)d im eth yl-
silyl]ben zen e, 2. To a magnetically stirred suspension (-78
°C) of Ph3SnNa (10.25 g, 27.49 mmol) in a mixture of THF (50
mL) and NH3 (200 mL) prepared from sodium (1.26 g, 54.78
mmol) and Ph3SnCl (10.59 g, 27.49 mmol) was added dropwise
a solution of 1 (4 g, 13.74 mmol) in THF (60 mL) over 20 min.
The reaction mixture was stirred at -78 °C for 3 h and allowed
to warm to room temperature overnight. After removing the
THF in vacuo Et2O was added and the precipitate (NaCl) was
filtered off. The Et2O was evaporated and the remaining crude
product (12.5 g, colorless solid) recrystallized from CH2Cl2/
hexane to give 2 (10.3 g, 81.5% yield, mp 141-143 °C) as a
Syn th esis of Bis{[(tr im eth ylsilylm eth yl)d ih yd r oxy-
sta n n ylm eth yl]d im eth ylsilyl}ben zen e, 5. To a magneti-
cally stirred solution (0 °C) of NaOH (1.0 g, 25 mmol) in 15
mL of H2O was added dropwise a solution of 4 (1.0 g, 1.29
mmol) in 20 mL of MeOH. The reaction mixture was stirred
for 24 h and the resulting colorless precipitate filtered off and
washed with water, MeOH, and EtOH to give 5 as a colorless
solid (850 mg, 99% yield, mp 130-140 °C). The compound was
insufficiently soluble to allow NMR spectroscopic investigation.
IR (KBr): νOH 3600 cm-1 (br). Anal. Calcd for C20H46O4Si4-
Sn2: C 34.30, H 6.62. Found: C 34.24, H 6.10.
1
colorless solid. H NMR (299.98 MHz, CDCl3): δ 0.35 (s, 6H,
2
SiMe2), 0.86 [s, 2H, J (117/119Sn-1H) ) 74/77, CH2], 7.35-7.98
(m, 17H, C6H4, SnPh3). 13C{1H} NMR (75.44 MHz, CDCl3): δ
-5.9 [1J (117/119Sn-13C) ) 263/275, 1J (29Si-13C) ) 49, CH2], -0.1
[1J (29Si-13C) ) 53, SiMe2], 128.4 [3J (117/119Sn-13C) ) 50, Cm],
128.8 (Cp), 132.59 (CoSi), 136.9 [2J (117/119Sn-13C) ) 38, Co], 139.4
[1J (117/119Sn-13C)
)
484/507, CI], 141.3 (CiSi). 29Si{1H}
Rea ction of Com p ou n d 4 w ith Com p ou n d 5. 5 (327 mg,
0.467 mmol) and 4 (361 mg, 0.467 mmol) were combined with
CHCl3 (12 mL) and stirred for 48 h at 60 °C to give a clear
solution. After removing the organic solvent in vacuo the crude
(25) Rieke, R. D.; Bales, S. E. J . Chem. Soc., Chem. Commun. 1973,
879.

Extending Distannoxane Double Ladders
product was recrystallized from toluene/hexane/CH2Cl2
mixture (35 mL, 8 mL, 5 mL) to give 6′ as a colorless solid
(520 mg, 78% yield, mp 225-235 °C). IR (Nujol): νOH 3652
cm-1. Anal. Calcd for C80H169Cl7O5Si16Sn8: C 33.42, H 5.84;
Cl, 8.68. Found: C 33.40, H 6.01; Cl 8.25.
Organometallics, Vol. 21, No. 4, 2002 651
Ta ble 1. Cr ysta llogr a p h ic Da ta for 6 a n d
a
11‚Tolu en e
6
11‚toluene
formula
fw
C80H168Cl8O4Si16Sn8 C79H144Cl8O4Si8Sn8
2876.7
2615.8
Syn t h esis of 1,3-Bis[(2-t r ip h en ylst a n n yl)et h yl]b en -
zen e, 7. A solution of Ph3SnH (15.39 g, 43.85 mmol) and AIBN
(0.36 g, 2.19 mmol) in benzene (50 mL) was added dropwise
to a magnetically stirred solution of 1,3-divinylbenzene
(2.85 g, 21.92 mmol) in benzene (50 mL) at reflux. The
resulting reaction mixture was stirred at reflux for 2 h. After
removing the benzene in vacuo the crude product was crystal-
lized from dichloromethane/hexane to give 7 as a colorless solid
(15.1 g, 83% yield, mp 143-146 °C). 1H NMR (299.98 MHz,
cryst size, mm
cryst syst
space group
a, Å
b, Å
c, Å
0.10 × 0.10 × 0.18
monoclinic
Pc
22.913(1)
12.680(1)
22.019(1)
101.592(1)
6266.9(5)
2
1.524
2880
19.28
24 166
0.10 × 0.10 × 0.15
monoclinic
P21/n
19.091(1)
13.155(1)
24.413(1)
104.945(1)
5923.7(5)
2
1.466
2596
19.55
34 550
â, deg
V, Å3
Z
D
calcd, g cm-3
2
CDCl3): δ 1.98 [t, 4H, J (117/119Sn-1H) ) 52, SnCH2], 3.14 [t,
F(000)
4H, 3J (117/119Sn-1H) ) 54, CH2], 7.09 (s, 1H, C6H4), 7.18 (d,
2H, C6H4), 7.34 (t, 1H, C6H4), 7.45-7.80 (m, 30H, SnPh3). 13C-
{1H} NMR (75.44 MHz, CDCl3): δ 13.0 [1J (117/119Sn-13C) ) 367/
384, SnCH2], 32.4 [2J (117/119Sn-13C) ) 19, CH2], 125.5 (C6H4),
127.6 (C6H4), 128.4 [3J (117/119Sn-13C) ) 47, Cm], 128.6 (C6H4),
128.8 [4J (117/119Sn-13C) ) 11, Cp], 137.0 [2J (117/119Sn-13C) ) 35,
Co], 138.7 [1J (117/119Sn-13C) ) 466/488, Ci], 144.9 [3J (117/119Sn-
µ, cm-1
no. of data colld
θmax, deg
25.7
25.7
10 509
10 031
no. of unique data 18 138
no. of unique data 6261
with I g 3.0σ(I)
R
Rw
0.090
0.105
0.063
0.034
13C) ) 57, C6H4]. 119Sn{1H} NMR (111.85 MHz, CDCl3):
δ
-100.1 [1J (13C-119Sn) ) 386, 1J (13C-119Sn) ) 488]. Anal. Calcd
4H, 2J (117/119Sn-1H) ) 54, SnCH2], 3.11 [t, 4H, 3J (117/119Sn-
1H) ) 112, CH2], 7.14 (d, 2H, C6H4), 7.16 (s, 1H, C6H4), 7.31 (t,
1H, C6H4). 13C{1H} NMR (75.44 MHz, CDCl3): δ 1.0 [1J (29Si-
for C46H42Sn2: C 66.39, H 5.09. Found: C 66.15, H 4.72.
Syn th esis
of
1,3-Bis{[2-(tr im eth ylsilylm eth yl)d i-
3
13C) ) 52, J (117/119Sn-13C) ) 26, SiMe3], 11.7 [1J (29Si-13C) )
p h en ylsta n n yl]eth yl}ben zen e, 8. To a magnetically stirred
solution (0 °C) of 7 (10.00 g, 12.01 mmol) in CHCl3 (100 mL)
was added I2 (6.10 g, 24.02 mmol) in small portions over 30
min. The reaction mixture was stirred for 2 h, the solvent
removed in vacuo, and the resulting yellow oil kept for 3 h at
130 °C and 10-3 Torr to remove all volatile byproducts. The
oily residue (11.19 g, 12.01 mmol) was dissolved in THF (100
mL) and added dropwise at room temperature during 1 h to a
Grignard solution prepared from chloromethyltrimethylsilane
(4.42 g, 36.05 mmol) and Mg (1.75 g, 72.10 mmol) in THF (100
mL). The reaction mixture was refluxed overnight and the
THF removed in vacuo. To the resulting colorless solid was
added Et2O and the suspension hydrolyzed with saturated
NH4Cl solution. The organic layer was washed twice with
water and dried over Na2SO4. After filtration the organic
solvent was evaporated in vacuo and the resulting yellow oil
kept for several hours at 130 °C and 10-3 Torr to remove all
volatile byproducts to give 8.57 g of crude product that could
be used without further purification. 1H NMR (299.98 MHz,
CDCl3): δ 0.25 (s, 18H, SiMe3), 0.45 [s, 4H, 2J (117/119Sn-1H) )
72/75, SiCH2], 1.87 [t, 4H, 2J (117/119Sn-1H) ) 45, SnCH2], 3.13
[t, 4H, 3J (117/119Sn-1H) ) 51, CH2], 7.22 (d, 2H, C6H4), 7.26 (s,
1H, C6H4), 7.41 (t, 1H, C6H4), 7.50-7.85 (m, 20H, SnPh2).
13C{1H} NMR (75.44 MHz, CDCl3): δ -5.5 [1J (117/119Sn-13C)
) 244/255, SiCH2], 1.6 [3J (117/119Sn-13C) ) 16, SiMe3], 13.7
[1J (117/119Sn-13C) ) 350/366, SnCH2], 32.5 [2J (117/119Sn-13C) )
17, CH2], 125.3 (C6H4), 127.5 (C6H4), 128.2 [3J (117/119Sn-13C)
) 47, Cm], 128.4 (C6H4), 128.5 (Cp), 136.6 [2J (117/119Sn-13C)
) 35, Co], 140.5 [1J (117/119Sn-13C) ) 440/462, Ci], 145.1
[3J (117/119Sn-13C) ) 57, C6H4]. 119Sn{1H} NMR (111.85 MHz,
CDCl3): δ -59.0 [1J (13C-119Sn) ) 463, 1J (13C-119Sn) ) 368,
1J (13C-119Sn) ) 254].
43, 1J (117/119Sn-13C) ) 284/297, SiCH2], 29.4 [1J (117/119Sn-13C)
) 450/471, SnCH2], 30.5 [2J (117/119Sn-13C) ) 30, CH2], 126.5
(C6H4), 127.9 (C6H4), 129.7 (C6H4), 143.1 [3J (117/119Sn-13C) )
76, C6H4]. 119Sn{1H} NMR (111.85 MHz, CDCl3): δ 130.6. Anal.
Calcd for C18H34Cl4Si2Sn2: C 31.52, H 5.00. Found: C 31.15,
H 5.05.
Syn th esis of th e Or ga n otin Oxid e 10. To a magnetically
stirred solution (0 °C) of NaOH (1 g, 25 mmol) in 15 mL of
H2O was added dropwise a solution of C (1.0 g, 1.46 mmol) in
20 mL of MeOH. The reaction mixture was stirred for 24 h
and the resulting white precipitate filtered off, washed with
water, and dried at 60 °C and 10-3 Torr to give 10 as a colorless
solid (840 mg, 100% yield, mp 290 °C dec). Anal. Calcd for
C
18H34O2Si2Sn2: C 37.53, H 5.95. Found: C 37.60, H 6.28.
Syn th esis of th e Tetr a m er ic Tetr a or ga n od ista n n ox-
a n e 11. 9 (595 mg, 0.868 mmol) and 10 (500 mg, 0.868 mmol)
were combined, toluene (20 mL) was added, and reaction
mixture was stirred for 24 h at reflux to give a clear solution.
The solution was concentrated to 2 mL to give 11 as color-
less crystals (790 mg, 72% yield, mp 278-279 °C). 1H NMR
(299.98 MHz, CDCl3): δ 0.23 (s, 18H, SiMe3), 0.23 (s, 18H,
SiMe3), 0.98 [s, 4H, 2J (117/119Sn-1H) ) 123, SiCH2], 1.02 [s, 4H,
2J (117/119Sn-1H) ) 123, SiCH2], 1.93 [m, 4H, SnCH2], 2.23 [m,
4H, SnCH2], 2.89 [t, 4H, CH2], 3.23 [t, 4H, CH2], 6.10 (s, 1H,
C6H4), 6.98 (d, 2H, C6H4), 7.01 (s, 1H, C6H4), 7.18-7.26 (m,
4H, C6H4). 13C{1H} NMR (75.44 MHz, CDCl3): δ 1.4 [1J (29Si-
13C) ) 52, 3J (117/119Sn-13C) ) 32, SiMe3], 2.0 [1J (29Si-13C) )
52, 3J (117/119Sn-13C) ) 30, SiMe3], 18.4 [1J (29Si-13C) ) 43,
1J (117/119Sn-13C) ) 402/420, SiCH2], 19.5 [1J (29Si-13C) ) 43,
1J (117/119Sn-13C) ) 377/394, SiCH2], 30.9 [2J (117/119Sn-13C) )
33, CH2], 31.1 [2J (117/119Sn-13C) ) 33, CH2], 32.3 [1J (117/119Sn-
13C) ) 569/595, SnCH2], 34.9 [1J (117/119Sn-13C) ) 612/640,
SnCH2], 124.8 (C6H4), 125.4 (C6H4), 126.9 (C6H4), 127.6
(C6H4), 128.8 (C6H4), 129.7 (C6H4), 143.2 [3J (117/119Sn-13C) )
76, C6H4], 143.5 [3J (117/119Sn-13C) ) 76, C6H4]. 119Sn{1H} NMR
(111.85 MHz, CDCl3): δ -79.1 [2J (119Sn-117/119Sn) ) 72],
-141.5 [2J (119Sn-117/119Sn) ) 72]. Anal. Calcd for C72H136Cl8O4-
Si8Sn8: C 34.26, H 5.43. Found: C 34.25, H 5.55.
Syn th esis
of
1,3-Bis{[2-(tr im eth ylsilylm eth yl)d i-
ch lor osta n n yl]eth yl}ben zen e, 9. To a magnetically stirred
solution (0 °C) of 8 (8.57 g, 10.05 mmol) in acetone (100 mL)
was added dropwise a solution of HgCl2 (10.92 g, 40.20 mmol)
in acetone (100 mL) over 30 min. The reaction mixture was
stirred overnight and the resulting precipitate (PhHgCl)
filtered off. After removing the acetone in vacuo Et2O (100 mL)
was added and the suspension stirred for 10 min. The PhHgCl
was removed by filtration and the organic solvent evaporated
in vacuo to give the crude product, which was recrystallized
from hexane to give 9 as a colorless solid (3.7 g, 54% yield, mp
64-67 °C). 1H NMR (299.98 MHz, CDCl3): δ 0.12 (s, 18H,
X-r a y Cr ysta llogr a p h y. Data were collected for colorless
crystals of 6 and 11‚toluene at 173 K employing graphite-
monochromatized Mo KR radiation, λ ) 0.7107 Å, on a Nonius
KappaCCD diffractometer. Corrections were made for Lorentz
and polarization effects26 and for absorption using an empirical
procedure (SORTAV). Crystal data are given in Table 1.
2
SiMe3), 0.55 [s, 4H, J (117/119Sn-1H) ) 87/91, SiCH2], 2.08 [t,

652 Organometallics, Vol. 21, No. 4, 2002
Dakternieks et al.
The structures were solved by heavy-atom methods27 and
refined by a full-matrix least-squares procedure based on F.26
The analysis for 6 was nontrivial, but successful refinement
was achieved in space group Pc. Considerable difficulties were
encountered in the refinement with several atomic positions
being poorly resolved; however, the molecular connectivity has
been established unambiguously. The tin atoms were refined
anisotropically with all other atoms being treated isotropically.
It was not possible to determine the absolute structure, as
there were no significant differences between Friedel pairs
included in the data set. A residual electron density peak (4.1
e Å-3) was located in a chemically nonsensible position, and it
is concluded that this was an artifact of the data. It should be
noted that some 15 different crystals were examined over the
course of the examination. All samples showed the same metric
symmetry and the same systematic extinctions, lending sup-
port to the choice of space group. The data reported here for 6
represents the best that we were able to obtain. For 11‚toluene,
non-hydrogen atoms were refined with anisotropic displace-
ment parameters and H atoms were included in the model in
their calculated positions (C-H 0.95 Å) with two exceptions.
The Si(3)-bound methyl groups were found to be disordered,
and each was modeled (isotropic, no hydrogens) over two
positions with 50% site occupancy (from refinement). In
addition, a disordered molecule of toluene was located in
difference maps toward the end of refinement so that the
asymmetric unit comprises one-half of a tetranuclear double
ladder and one solvent molecule. This molecule was modeled
as three approximately superimposed molecules such that
three positions (33% occupancy) were found for the methyl
groups and seven positions for the aromatic carbons (86%
occupancy). The refinements were continued until convergence
with the application of a weighting scheme of the form w )
1/[σ2(Fo)], and final refinement details are given in Table 1.
Numbering schemes (ORTEP,28 at the 50% probability level)
are shown in Figures 1 and 2.
Ack n ow led gm en t. We are grateful to the Austra-
lian Research Council and the Deutsche Forschungs-
gemeinschaft for financial support.
Su p p or tin g In for m a tion Ava ila ble: Further details of
the structure determination including atomic coordinates, bond
distances and angles, and thermal parameters. This ma-
terial is available free of charge via the Internet at http://
pubs.acs.org.
OM0105627
(27) Beurskens, P. T.; Admiraal, G.; Beurskens, W. P.; Bosman, W.
P.; Garcia-Granda, S.; Smits, J . M. M.; Smykalla, C. The DIRDIF
program system; Technical report of the Crystallography Laboratory;
University of Nijmegen: The Netherlands, 1992.
(26) teXsan: Structural Ananlysis Software; Molecular Structure
Corp.: The Woodlands, TX.
(28) J ohnson, C. K. ORTEP; Report ORNL-5138; Oak Ridge Na-
tional Laboratory: TN, 1976.