A spacer-linked molecular diorganotin oxide

Article abstract of DOI:10.1021/om020749d

The synthesis and molecular structure are reported of the first example of a diorganotin oxide, {p-[R(O)SnCH₂SiMe₂]₂C₆H₄} ₃ (3) (R = (Me₃Si)₂CH), in which two six-membered Sn₃O₃ units are linked by three -CH₂Si(Me)₂C₆H₄Si(Me)₂ CH₂- spacers.

Full text of DOI:10.1021/om020749d

Organometallics 2003, 22, 1343-1345
1343
A Sp a cer -Lin k ed Molecu la r Dior ga n otin Oxid e
Dainis Dakternieks* and Bernhard Zobel
Centre for Chiral and Molecular Technologies, Deakin University,
Geelong, Victoria 3217, Australia
Klaus J urkschat* and Marcus Schu¨rmann
Lehrstuhl fu¨r Anorganische Chemie II der Universita¨t Dortmund,
D-44221 Dortmund, Germany
Edward R. T. Tiekink*
Department of Chemistry, National University of Singapore, Singapore 117543
Received September 10, 2002
Summary: The synthesis and molecular structure are
reported of the first example of a diorganotin oxide,
{p-[R(O)SnCH2SiMe2]2C6H4}3 (3) (R ) (Me3Si)2CH), in
which two six-membered Sn3O3 units are linked by three
-CH2Si(Me)2C6H4Si(Me)2CH2- spacers.
Recently, we used the concept of the preassembly of
suitably architectured precursors containing two or
three tins to generate larger molecular units. Such
precursors in which the tin atoms are connected by
flexible oligomethylene-bridged spacers could be trans-
formed to double- and triple-ladders of types C and D,
respectively (Chart 1).12,13a,b For example, double ladders
of type C were obtained by reaction of a spacer-bridged
diorganotin dichloride of type A with the corresponding
spacer-bridged diorganotin oxide of type B (Chart 1).
The spacer-linked oxide species B have hitherto
been amorphous solids and poorly characterized. The
use of more rigid spacers such as -CH2Si(Me)2C6H4Si-
(Me)2CH2- can give rise to different molecular archi-
tectures, for example, a unique twisted DL-double-ladder
containing eight chiral tin atoms.14 We now report the
use of a more rigid spacer that has enabled character-
ization for the first time of a spacer-linked molecular
tin oxide (3).
In tr od u ction
Diorganotin oxides (R2SnO)n have been known for
many years. Generally they are polymeric (n ) ∞, R )
Me, Et, Bu, vinyl, Ph).1,2 However, some molecular
species have been characterized for diorganotin oxides
containing bulky substituents. When R ) (Me3Si)2CH,
a dimer (n ) 2)3 is formed, whereas trimers (n ) 3) have
been reported for cases where R ) CH2SiMe3,4 t-Bu,
Me2EtC,5 (Me3Si)3C/Me,6 2,6-Me2-C6H3,7 2,6-Et2-C6H3,8
2,4,6-(CF3)3-C6H2,9 and 2,4,6-i-Pr-C6H2.10 Furthermore,
for R ) Me3SiCH2, the existence in solution of a
tetramer (n ) 4) was proposed on the basis of NMR
studies.4 A convenient synthesis of diorganotin oxides
is the complete hydrolysis of diorganotin dihalides,
R2SnX2 (X ) Cl, Br). Dimeric tetraorganodistannoxanes
of the type [R2(X)SnOSn(Y)R2]2 (X, Y ) Cl, Br, OH) are
formed along the hydrolysis path. In addition to some
interesting structural features such as the almost
perfect planarity of the Sn4O2X2Y2 layer, the latter class
of compound is of high practical value, as representa-
tives are efficient catalysts for a variety of organic
reactions.11
Resu lts a n d Discu ssion
Compound 3 has been obtained in a multistep pro-
cedure as shown in Scheme 1. It is a colorless, crystal-
line solid that does not melt or decompose until 345 °C
and which is only slightly soluble in chloroform, hot
benzene, or toluene. Crystals suitable for X-ray crystal-
lography were obtained as the tri-toluene solvate.
The molecular structure of the spacer-bridged dior-
ganotin oxide 3 is illustrated in Figure 2, and key
geometric parameters are listed in the caption;15 there
is no molecular symmetry in the structure. The struc-
ture features two Sn3O3 units, each of which adopts a
flattened chair conformation, that are linked by the
three -CH2Si(Me)2C6H4Si(Me)2CH2- spacers that
adopt extended conformations as seen in the range of
Sn-C-Si-C torsion angles of 163.0(3)-173.4(2)°. The
links are arranged so that the tin atoms are directed
* Correspondence to K.J . Tel: 49-231-7553800. Fax: 49-231-
7555048. E-mail: kjur@platon.chemie.uni-dortmund.de.
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J urkschat, K. Angew. Chem., Int. Ed. Engl. 1997, 36, 1112.
(13) (a) Mehring, M.; Paulus, I.; Zobel, B.; Schu¨rmann, M.; J urk-
schat, K.; Duthie, A.; Dakternieks, D. Eur. J . Inorg. Chem. 2001, 153.
(b) Dakternieks, D.; Duthie, A.; J urkschat, K.; Schu¨rmann, M.; Tiekink,
E. R. T. Main Group Met. Chem. 2002, 25, 73.
(14) Dakternieks, D.; Duthie, A.; Zobel, B.; J urkschat, K.; Schu¨r-
mann, M.; Tiekink, E. R. T. Organometallics 2002, 21, 647.
10.1021/om020749d CCC: $25.00 © 2003 American Chemical Society
Publication on Web 02/08/2003

1344 Organometallics, Vol. 22, No. 6, 2003
Notes
Ch a r t 1
Sch em e 1
F igu r e 1. Molecular structure of 3 showing the crystal-
lographic numbering scheme. The O2 atom is obscured,
only the major conformation of the disordered C20 and C21
atoms is shown, all hydrogen atoms and the three toluene
molecules of solvation have been omitted for clarity, and
atoms otherwise not indicated are carbons. Selected ranges
for bond lengths (Å) and angles (deg): Sn-O 1.964(3)-
1.974(3), Sn-C 2.134(6)-2.163(5), O-Sn-O 103.6(1)-
104.6(1), O-Sn-C 106.1(2)-111.9(2) and C-Sn-C 116.1-
(2)-119.0(2).
toward the center of the cavity thus formed and the
silicon-bound methyl groups are oriented outside the
cavity, the latter presumably so as to minimize steric
interactions. The triangles formed by the two sets of tin
atoms are almost parallel (dihedral angle 4.1°) and
projecting through the molecule, Sn3 triangle to Sn3
triangle, showing that each tin atom of one Sn3O3 ring
is superimposable upon an oxygen of the second ring.
The average separation between the two triangles is
approximately 12.2 Å, and the twist between them is
estimated to be 37°. In terms of a solid geometry and to
a first approximation, the tin oxide/spacer framework
may be described as a molecular prism, the aforemen-
tioned twist not withstanding. The coordination geom-
etry about each tin atom is completed by a CH(SiMe3)2
substituent, each of which is directed away from the
central part of the molecule. The tin atoms exist in
distorted C2O2 tetrahedral geometries with the narrow-
est angles (approximately 104°) involving endocyclic
oxygen atoms and the widest subtended by the exocyclic
organic substituents (approximately 117°).
(15) Crystal data for C78H174O6Si18Sn6‚3C7H8: Mr ) 2702.3, triclinic,
P1h, a ) 15.234(1) Å, b ) 20.056(1) Å, c ) 23.854(1) Å, R ) 77.180(1)°,
â ) 77.455(1)°, γ ) 79.989(1)°, V ) 6876.1(6) Å3, Z ) 2, Dx ) 1.305 g
cm-3, µ ) 12.71 cm-1. Intensity data (47 270) were collected at 153(2)
K on a Nonius KappaCCD fitted with graphite-monochromated Mo
KR radiation (λ 0.71073 Å) so that θmax was 25.0°. Data were corrected
for absorption using SADABS,16 solved with SHELXLS97,17 and refined
Con clu sion
The results reported confirm the utility of the preas-
sembly concept and opens the way to rational design of
other new high-nuclearity organotin oxides. Control over
the nuclearity and interlaminar spacing offers new op-
portunities for catalytic and other practical applications.
on F2 using SHELXL97.17 The
H atoms were included in their
geometric positions using a riding model approximation. One of the
phenyl rings of the spacer groups, i.e., C16-C21, was found to be
disordered, but two positions were discernible for the C20 and C21
atoms only. These were refined isotropically with site occupancy factors
of 0.7 and 0.3 (determined from refinement). Similarly, severe disorder
was found in one of the three solvent toluene molecules, and this was
Exp er im en ta l Section
refined isotropically as a rigid group. The final R values were R1
)
0.038 (for 12 619 data with I > 2σ(I)) and wR2 ) 0.082 (for 22 366
unique data). The diagram was drawn with ORTEP at the 50%
probability level.18
All solvents were dried and purified by standard procedures.
NMR spectra were obtained using a Varian 300 MHz Unity

Notes
Organometallics, Vol. 22, No. 6, 2003 1345
solvent was evaporated in vacuo, and the resulting yellow oil
was kept 1 h at 130 °C and 10-3 Torr to remove all volatile
byproducts to give 4.32 g of 1,4-bis[bis(trimethylsilyl)methyl-
diphenylstannylmethyldimethylsilyl)]benzene (δ 29Si (59.6
MHz, CDCl3) -2.01 (s, 2J (117/119Sn-29Si) ) 22, SiMe2); 1.57
(s, 2J (117/119Sn-29Si) ) 31, 1J (13C-29Si) ) 51, SiMe3); δ
119Sn (111.85 MHz, CDCl3) -55.2 1J (13C-119Sn) ) 479,
1J (13C-119Sn) ) 256), which was used for the subsequent
reaction without further purification.
To a magnetically stirred and cooled (0 °C) solution of the
latter compound (4.32 g, 3.99 mmol) in acetone (50 mL) was
added dropwise a solution of HgCl2 (5.50 g, 20.26 mmol) in
acetone (50 mL) during 30 min. The reaction mixture was
stirred for 7 days and the acetone removed in vacuo. Hexane
(100 mL) was added to the residue, and the suspension was
heated at reflux for 10 min. The hot solution was filtered to
remove PhHgCl, and the organic solvent of the filtrate was
evaporated in vacuo to give 3.74 g of a yellow oil, which was
recrystallized from CHCl3 (15 mL) to give 1.96 g (51%) of
1,4-bis[bis(trimethylsilyl)methyldichlorostannylmethyldi-
methylsilyl)]benzene, mp 133-136 °C. 1H NMR (299.98
MHz, CDCl3): δ -0.11 [s, 1H, 2J (117/119Sn-1H) ) 101/106,
CH]; 0.16 (s, 18H, SiMe3); 0.51 (s, 6H, SiMe2); 1.00 (s, 2H,
2J (117/119Sn-1H) ) 84/89, CH2); 7.59 (s, 2H, C6H4). 13C
NMR (75.44 MHz, CDCl3): δ SiMe2 -0.67 J (117/119Sn-13C) )
3
20, 1J (29Si-13C) ) 55; SiMe3 2.77 3J (117/119Sn-13C) ) 27,
1J (29Si-13C) ) 52; CH 14.81, 1J (117/119Sn-13C) ) 314/329,
1J (29Si-13C) ) 46; CH2 18.24, 1J (117/119Sn-13C) ) 204/213,
1J (29Si-13C) ) 35; Co 133.21; Ci 140.66. 119Sn NMR (111.85
MHz, CDCl3): δ 123.7. Anal. Calcd for C26H58Cl4Si6Sn2: C,
34.00; H, 6.36. Found: C, 33.99; H, 6.38.
F igu r e 2. Tilted view of 3 highlighting the framework in
the molecular diorganotin oxide. Only the major conforma-
tion of the disordered C20 and C21 atoms is shown. All
methyl groups, hydrogen atoms, and the three toluene
molecules of solvation have been omitted for clarity.
1
Plus NMR spectrometer. H, 13C, and 119Sn chemical shifts δ
Syn th esis of th e Dior ga n otin Oxid e (3). To a magneti-
cally stirred solution of 1,4-bis[bis(trimethylsilyl)methyldi-
chlorostannylmethyldimethylsilyl)]benzene (2) (400 mg, 0.44
mmol) in toluene (6 mL) at 70-80 °C was added dropwise a
solution of NaOH (1.3 g, 32.50 mmol) in water (6 mL) during
2 min. The reaction mixture was stirred at 80 °C for 12 h
followed by addition of a further 3 mL of hot toluene. The
organic layer was separated and the solvent evaporated in
vacuo to give 380 mg of a white solid, which was recrystallized
from hot toluene (15 mL) to give the diorganotin oxide 3 (240
mg, 68%) as colorless crystals that do not melt or decompose
below 345 °C. Upon exposure to air, these crystals within
minutes become opaque, indicating the loss of solvent. 1H NMR
(299.98 MHz, CDCl3): δ -0.04 [s, 2J (117/119Sn,1H) ) 96/102 Hz,
6H, CH]; 0.22 (s, 108H, SiMe3), 0.34 (s, 36H, SiMe2), 0.73 [s,
2J (117/119Sn,1H) ) 87/92 Hz, 12H, CH2], 7.58 (s, 12H, C6H4).
13C{1H} NMR (75.44 MHz, CDCl3): δ 0.93 [1J (29Si,13C) ) 52
Hz, SiMe2], 3.35 [3J (117/119Sn,13C) ) 22 Hz, 1J (29Si,13C) ) 51
Hz, SiMe3], 11.06 [1J (117/119Sn,13C) ) 299/311 Hz, CH], 14.93
[1J (117/119Sn,13C) ) 303/318 Hz, 1J (29Si,13C) ) 37 Hz, CH2],
132.46 (Co), 141.82 (Ci). 119Sn{1H} NMR (111.85 MHz,
CDCl3): δ 38.0 [2J (117Sn,119Sn) ) 415 Hz]. Anal. Calcd for
are given in ppm and are referenced against Me4Si and
Me4Sn, respectively. Coupling constants J are given in Hz.
Uncorrected melting points were determined on a Kofler hot
stage. Microanalyses were performed using a CE 1106 elemen-
tal analyzer. The synthesis of compound 1 has been described
elsewhere.14
Syn th esis
of
1,4-Bis[bis(tr im eth ylsilyl)m eth yld i-
ch lor ost a n n ylm et h yld im et h ylsilyl)]b en zen e (2). To a
magnetically stirred and cooled (0 °C) solution of 1,4-bis-
(triphenylstannylmethyldimethylsilyl)benzene (1) (2.6 g, 2.83
mmol) in CH2Cl2 (30 mL) was added in small portions I2 (1.435
g, 5.65 mmol) during 30 min. The reaction mixture was stirred
for 2 h, and the solvent and all volatile byproducts were
removed in vacuo (3 h at 130 °C and 10-3 mm/Hg) to give 1,4-
bis(iododiphenylstannylmethyldimethylsilyl)benzene as a yel-
low oil (δ 119Sn (111.85 MHz, CDCl3) -58.7, 1J (13C-119Sn) )
538, 269 Hz), which was used for the subsequent reaction
without further purification.
To a solution of LiCH(SiMe3)219 in Et2O (23 mL, c ) 0.4 mol/
L) was added at room temperature a solution of 1,4-bis-
(iododiphenylstannylmethyldimethylsilyl)benzene (4.43 g, 4.35
mmol) in Et2O (40 mL) during 40 min. The reaction mixture
was stirred overnight and hydrolyzed with saturated NH4Cl
solution. The organic layer was separated, washed twice with
water, and dried over Na2SO4. After filtration the organic
C
78H174O6Si18Sn6: C, 38.62; H, 7.23. Found: C, 38.51; H, 7.21.
Ack n ow led gm en t. We thank the Australian Re-
search Council and the Deutsche Forschungsgemein-
schaft for financial support.
(16) Sheldrick, G. M. SADABS; University of Go¨ttingen: Germany,
1996.
(17) Sheldrick, G. M. SHELXS97 and SHELX97; University of
Go¨ttingen: Germany, 1997.
(18) J ohnson, C. K. ORTEP, Report ORNL-5138; Oak Ridge Na-
tional Laboratory: TN, 1976.
(19) Davidson, P. J .; Harris, D. H.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1976, 2268.
Su p p or tin g In for m a tion Ava ila ble: Tables of all coor-
dinates, anisotropic displacement parameters, and geometric
data for compound 3. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM020749D