Synthesis and characterization of lithiated dendrimers

Article abstract of DOI:10.1021/om020799i

The synthesis of the precursor phenylthiomethyl-functionalized carbosilane dendrimers Si[(CH₂)₃SiMe₂CH₂SPh]₄ (1) and Si{(CH₂)₃Si[(CH₂)₃SiMe₂ CH₂SPh]₃}₄ (2) is described. Reacting 1 and 2 with lithium naphthalenide gives the first lithiomethyl-functionalized dendrimers Si[(CH₂)₃SiMe₂CH₂Li]₄ (7) and Si{(CH₂)₃Si[(CH₂)₃ SiMe₂CH₂Li]₃}₄ (11). Deutero, trimethylsilyl, trimethylstannyl, and tri-n-butylstannyl derivatives of these dendrimers, as well as a method to enable isolation of the lithiated dendrimers as solids, are described.

Full text of DOI:10.1021/om020799i

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Organometallics 2003, 22, 1811-1815
1811
Syn th esis a n d Ch a r a cter iza tion of Lith ia ted Den d r im er s
Reinout Meijboom, Alan T. Hutton, and J ohn R. Moss*
Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
Received September 24, 2002
The synthesis of the precursor phenylthiomethyl-functionalized carbosilane dendrimers
Si[(CH2)3SiMe2CH2SPh]4 (1) and Si{(CH2)3Si[(CH2)3SiMe2CH2SPh]3}4 (2) is described. React-
ing 1 and 2 with lithium naphthalenide gives the first lithiomethyl-functionalized dendrimers
Si[(CH2)3SiMe2CH2Li]4 (7) and Si{(CH2)3Si[(CH2)3SiMe2CH2Li]3}4 (11). Deutero, trimethyl-
silyl, trimethylstannyl, and tri-n-butylstannyl derivatives of these dendrimers, as well as a
method to enable isolation of the lithiated dendrimers as solids, are described.
In tr od u ction
such as THF. Since dendrimer synthesis requires quan-
titative reactions, the synthesis of such lithiated den-
drimers constitutes a considerable challenge.
The rising demand for materials with improved and
novel properties has shifted the emphasis in polymer
research from traditional linear polymers, via cross-
linked and branched polymers, to the hyperbranched
or dendritic polymers. This new class of highly branched
three-dimensional molecules has intrigued researchers,
and numerous review articles have been published in
recent years.1,2 Many applications for dendrimers have
been found, one of the most exciting applications being
the use of dendrimers as an immobilization phase for
homogeneous catalysts.3 From our ongoing research into
dendrimers and their applications in organometallic
chemistry,2,4 it has become clear that the number of
synthetic routes available to attach an organometallic
moiety to the branches of a dendrimer is limited. This
limitation is mainly due to the requirement to employ
reactions that have a quantitative yield in order to
prevent imperfections in the dendrimer buildup.5,6 It
was envisaged that a greater range of dendrimers could
be synthesized by using a polylithiated dendrimer.7
Despite the fact that alkyllithium reagents are useful
and versatile reagents for both organic and organome-
tallic synthesis, they (i) are air and moisture sensitive,
(ii) are prone to decomposition by â-hydride elimina-
tion,8 and (iii) have limited stability in some solvents
For the synthesis of known bis(lithiomethyl)silanes,
a limited number of reports are available in the litera-
ture. Recently a report by Strohmann et al. described
the high-yield synthesis of a series of bis(lithiomethyl)-
silanes9 and tetrakis(lithiomethyl)silanes10 by reductive
cleavage of C-S bonds with lithium naphthalenide. Our
strategy was to apply the method of Strohmann et al.9,10
to the synthesis of dendrimers. An important consider-
ation in our strategy was to prevent possible decomposi-
tion through â-hydrogen elimination, as well as stabi-
lizing the carbanion, by using a lithiomethyldimethylsilyl
group.
Resu lts a n d Discu ssion
We synthesized the first generation carbosilane den-
drimer Si[(CH2)3SiMe2CH2SPh]4 (1) and the correspond-
ing second generation dendrimer Si{(CH2)3Si[(CH2)3-
SiMe2CH2SPh]3}4 (2). These compounds are accessible
via catalytic hydrosilylation of tetraallylsilane (3) and
Si[(CH2)3Si(CH2CHdCH2)3]4 (4) with the known11 H-
SiMe2CH2SPh (5) (see Scheme 1). Compounds 1 and 2
were isolated as colorless, air-stable oils in nearly
quantitative yields.
* Corresponding author. Fax: +27-(0)21-6897499. E-mail: jrm@
science.uct.ac.za.
(5) The composition of dendrimers formed in reaction of the arms
with less than 100% yield can be calculated from the yield of the
specific reaction using the following formula: P ) (N!/n!m!)Yn(1 - Y)m;
where P ) mole fraction of product; N ) n + m ) total number of
reactive groups; n ) number of reacted groups; m ) number of
unreacted groups; and Y ) reaction yield. For example a reaction with
a yield of 95% on a dendrimer with 4 arms gives a mole fraction of P
) (4!/4!0!)(0.95)4(0.05)0 ) 0.815 of pure product. The other 18.5% are
impure dendrimers with one or more branches unreacted.
(6) Meijboom, R. Ph.D. Thesis, University of Cape Town, 2001.
(7) (a) Wijkens, P.; J astrzebski, J . T. B. H.; Van der Schaaf, P. A.;
Kolly, R.; Hafner, A.; Van Koten, G. Org. Lett. 2000, 2, 1621. (b)
Vasilenko, N. G.; Ignat’eva, G. M.; Rebrov, E. A.; Myakushev, V. D.;
Moeller, M.; Muzafarov, A. Polym. Prepr. 2001, 42, 238.
(8) (a) Seetz, J . W. F. L.; Schat, G.; Akkerman O. S.; Bickelhaupt,
F. J . Am. Chem. Soc. 1982, 104, 6848. (b) Seetz, J . W. F. L. Ph.D.
Thesis, Vrije Universiteit Amsterdam, 1983. (c) Maercker, A.; Theis,
M. Top. Curr. Chem. 1987, 138, 1.
(1) Some reviews: (a) Mekelburger, H.-B.; J aworek, W.; Vo¨gtle, F.
Angew. Chem., Int. Ed. Engl. 1992, 31, 1571. (b) Tomalia, D. A.; Durst,
H. D. Top. Curr. Chem. 1993, 165, 193. (c) Issberner, J .; Moors, R.;
Vo¨gtle, F. Angew. Chem., Int. Ed. Engl. 1994, 33, 2413. (d) Cuadrado,
I.; Mora´n, M.; Losada, J .; Casado, C. M.; Pascual, C.; Alonso B.; Lobete,
F. Adv. Dendritic Macromol. 1996, 3, 61. (e) Gudat, D. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1951. (f) Frey, H.; Lach C.; Lorenz, K. Adv.
Mater. 1998, 10, 279. (g) Puddephatt, R. J . J . Chem Soc., Chem.
Commun. 1998, 1055. (h) Majoral, J .-P.; Caminade, A.-M. Chem. Rev.
1999, 99, 845. (i) Smith, D. K.; Diederich, F. Chem. Eur. J . 1998, 4,
1353. (j) Fischer, M.; Vo¨gtle, F. Angew. Chem., Int. Ed. 1999, 38, 884.
(2) (a) Hearshaw, M. A.; Moss, J . R. J . Chem. Soc., Chem. Commun.
1999, 1. (b) Hearshaw, M. A.; Hutton, A. T.; Moss J . R.; Naidoo, K. J .
Adv. Dendritic Macromol. 1999, 4, 1.
(3) (a) Knapen, J . W. J .; Van der Made, A. W.; De Wilde, J . C.; Van
Leeuwen, P. W. N. M.; Wijkens, P.; Grove, D. M.; Van Koten, G. Nature
1994, 372, 659. (b) Oosterom, G. E.; Reek, J . N. H.; Kamer, P. C. J .;
Van Leeuwen, P. W. N. M. Angew. Chem., Int. Ed. 2001, 40, 1828.
(4) (a) Liao, Y.-H.; Moss, J . R. J . Chem. Soc., Chem. Commun. 1993,
1774. (b) Liao, Y.-H.; Moss, J . R. Organometallics 1995, 14, 2130. (c)
Liao, Y.-H.; Moss, J . R. Organometallics 1996, 15, 4307.
(9) Strohmann, C.; Lu¨dtke, S.; Wack, E. Chem. Ber. 1996, 129, 799.
(10) Strohmann, C.; Lu¨dtke, S.; Ulbrich, O. Organometallics 2000,
19, 4223.
(11) Yoshida, J .-I.; Tsujishima, H.; Nakano, K.; Isoe, S. Inorg. Chim.
Acta 1994, 220, 129.
10.1021/om020799i CCC: $25.00 © 2003 American Chemical Society
Publication on Web 04/02/2003

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1812 Organometallics, Vol. 22, No. 9, 2003
Sch em e 1. Syn th esis of 1 a n d 2
Meijboom et al.
Sch em e 3. Syn th esis of Lith ia ted Den d r im er w ith
12 F u n ction a lities a n d Its Rea ction
Sch em e 2. Syn th esis of 7 a n d Its Rea ction s
Gen er a tion of Lith ia ted Den d r im er s in Situ .
Following the method of Strohmann et al.,9,10 we reacted
1 with a slight excess of lithium naphthalenide (LiC10H8)
at -41 °C, followed by quenching with excess D2O. The
reaction proceeded rapidly and completely to give the
desired deuterated dendrimer Si[(CH2)3SiMe2CH2D]4
(6), as was concluded from the 1H and 13C NMR spectra
of the product after isolation. In addition to the deu-
terated dendrimer, however, 4 equiv of DSPh was
formed, as well as 8 equiv of naphthalene. The product
was isolated by repeated column chromatography, which
reduced the yield of final product to 9%. The NMR
signals attributable to the four branches appeared at
the same chemical shift due the high symmetry of the
molecule, confirming that complete conversion had
taken place.
After several attempts, we formulated a system that
successfully avoided the problems in separation of the
product from the side products.12 In this procedure, ca.
25 mol % naphthalene is used, with an excess of lithium,
at 0 °C. The phenylthiomethyl dendrimers 1 and 2 are
added slowly, making sure the green/blue color of the
lithium naphthalenide is always present during reac-
tion. These reactions are complete in about 1 h. Fortu-
nately, the generated lithium reagent is stable enough
in THF to “survive” for this time.
The tetralithiated reagent Si[(CH2)3SiMe2CH2Li]4 (7)
was analyzed by quenching the generated reagent in
situ with D2O, ClSiMe3, ClSnMe3, or ClSnBu3 at 0 °C
(Scheme 2). The products were separated from the salts
by extraction into hexane. Separation from the thiol
HSPh (formed by hydrolysis of LiSPh) was achieved by
washing the hexane solutions with dilute aqueous base.
Heating under vacuum at (100 °C removed the bulk of
the naphthalene through sublimation. The resulting
mixtures contained ca. 90% of the desired dendrimers,
which were then purified by column chromatography
over silica gel, eluting with hexane to yield Si[(CH2)3-
SiMe2CH2D]4 (6), Si[(CH2)3SiMe2CH2SiMe3]4 (8), Si-
[(CH2)3SiMe2CH2SnMe3]4 (9), and Si[(CH2)3SiMe2CH2-
SnBu3]4 (10) as colorless, air-stable oils. Full and
1
unambiguous characterizations were performed by H,
13C, and 29Si NMR spectroscopy, mass spectrometry, and
elemental analysis (see Experimental Section).
A similar procedure was successfully performed for
the second generation phenylthiomethyl dendrimer 2,
resulting in the formation of the second generation
lithiated dendrimer 11. Quenching 11 with ClSnBu3 in
situ gave the second generation tributyltin-terminated
derivative 12 (see Scheme 3). Satisfactory characteriza-
tion data for 12 were obtained (see Experimental
Section). To the best of our knowledge, 7 and 11 are
the first examples of methyllithium-functionalized den-
drimers, and the second generation dendrimer 11 is,
with 12 carbanionic functionalities, the largest alkyl-
lithium reagent reported to date.
Isola tion of Lith ia ted Den d r im er s. Due to the
difficulty of isolation of a lithiated dendrimer from the
side products formed, and with a view to obtaining pure
materials, we investigated a slightly different route.
Alkyltributyltin compounds are known to be convenient
precursors for the generation of alkyllithium reagents
via metathetical metal-metal exchange.13 In 1980, Seitz
and Zapata14 reported the high-yield synthesis of (tri-
methylsilylmethyl)lithium from (trimethylsilylmethyl)-
tributyltin and BuLi in THF. The side product of the
(13) See for example: (a) Wittig, G.; Schollkopf, U. Tetrahedron
1958, 3, 91. (b) Seyferth, D.; Weiner, M. A.; Vaughan, L. G.; Raab, G.;
Welch, D. E.; Cohen, H. M.; Alleston, D. L. Bull. Soc. Chim. Fr. 1963,
1364. (c) Peterson, D. J . J . Am. Chem. Soc. 1971, 93, 4027. (d) Seyferth,
D.; Murphy, G. J .; Mauze B. J . Am. Chem. Soc. 1977, 99, 5317. (e)
Seyferth, D.; Wusthorn, K. R. J . Organomet. Chem. 1977, 137, C17.
(f) Still, W. C. J . Am. Chem. Soc. 1978, 100, 1481. (g) Still, W. C.;
Sreekumar, C. J . Am. Chem. Soc. 1980, 102, 1201. (h) Meyer, N.;
Seebach, D. Chem. Ber. 1980, 113, 1290. (i) Goswani, R. J . Am. Chem.
Soc. 1980, 102, 5973. (j) Kauffmann, T.; Kriegesmann, R.; Altepeter
B.; Steinseifer, F. Chem. Ber. 1982, 115, 1810. (k) Quintard, J . P.;
Elissondo B.; Pereyre, M. J . Org. Chem. 1983, 48, 1559. (l) Piers, E.;
Karunaratne, V. J . Org. Chem. 1983, 48, 1774. (m) Sawyer, J . S.;
Macdonald T. L.; McGarvey, G. J . J . Am. Chem. Soc. 1984, 106, 3376.
(n) Corey, E. J .; Eckrich, T. M. Tetrahedron Lett. 1984, 25, 2415.
(14) Seitz, D. E.; Zapata, A. Tetrahedron Lett. 1980, 21, 3451.
(12) Several problems and their solutions have been described:
Cohen, T.; Bhupathy, M. Acc. Chem. Res. 1989, 22, 152, and references
therein.

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Lithiated Dendrimers
Organometallics, Vol. 22, No. 9, 2003 1813
Sch em e 4. Syn th esis of 7 via Tin -Lith iu m
methyl-functionalized dendrimer. This dendrimer was
isolated as a solid and characterized by NMR spectros-
copy.
Exch a n ge Rea ction
Exp er im en ta l Section
Gen er a l Rem a r k s. Lithiated dendrimers are extremely
air-sensitive compounds. Manipulations were carried out
under purified nitrogen using glovebox (MBraun Unilab) or
standard Schlenk line techniques under purified argon.17
Solvents were dried by passage through a column containing
alumina (neutral, Brockmann grade I) and distilled from
sodium/benzophenone ketyl prior to use.18 All reagents were
stored under argon. Butyllithium (1.6 M in hexanes), chlo-
rodimethylsilane, chlorotrimethylsilane, thioanisol, and trichlo-
rosilane were purchased from Sigma Aldrich. HSiMe2CH2-
reaction, tetrabutyltin, can easily be removed by extrac-
tion into pentane.
Following this method,14 we attempted the synthesis
of the tetralithiated compound 7. A solution of 10 in
THF was treated with 4.0 equiv of BuLi at 0 °C (Scheme
4). The yellow mixture slowly decolorized. After 30 min
the solvent was evaporated and the mixture of a white
solid and a clear liquid was extracted with pentane. 1H
NMR spectroscopy on the isolated solid product in
benzene-d6/THF-d8 indicated that 7 had formed. The
resonances due to the tributyltin moiety had disap-
peared and a singlet at ca. -1.8 ppm, integrating for
eight protons, was evident. This signal was attributed
to the four CH2Li moieties in the dendrimer. The value
of -1.8 ppm is similar to literature values for (trimeth-
ylsilylmethyl)lithium.15,16 The rest of the spectrum
showed the expected resonances consistent with the
product.
19
SPh11 and Si[(CH2)3Si(CH2CHdCH2)3]4 were prepared by
literature methods. Karstedt catalyst20 was prepared according
to literature methods and stored under argon as a 1% Pt
solution in toluene.
NMR spectra were recorded on either a Varian Unity-400
(1H, 400 MHz; 13C, 100.6 MHz; 29Si, 79.5 MHz) spectrometer
or a Varian Mercury-300 (1H, 300 MHz; 13C, 75.5 MHz)
spectrometer at ambient temperature. Chemical shifts were
referenced to TMS using either the residual protio impurities
in the solvent (1H NMR), the solvent resonances (13C NMR),
or external TMS (29Si NMR). Infrared spectra were recorded
on a Perkin-Elmer Paragon 1000 FT-IR spectrometer in the
range 450-4400 cm-1. Spectra were recorded on neat samples
between NaCl plates. Mass spectra were determined by Dr.
P. Boshoff of the mass spectrometry unit at the Cape Tech-
Compound 7 is not soluble in any common organic
solvents other than THF; it is an extremely air-sensitive
solid, and it reacts slowly with THF. We tried several
strategies to obtain suitable crystals for X-ray crystal-
lography, but only amorphous solids were obtained.
Further evidence for the formation and isolation of
the lithiated dendrimer was provided by quenching
NMR samples with D2O and ClSiMe3. After quenching,
1H NMR spectra identical to those obtained from the
previously isolated 6 and 8 were observed.
It is important in these reactions that exactly 4 equiv
of butyllithium is used, as any excess of butyllithium
co-aggregates with the dendrimer upon workup. We
found that it was subsequently not possible to separate
the aggregated butyllithium from the lithiated den-
drimer. The polylithiated compounds 7 and 11 may be
versatile reagents with useful applications in the field
of organometallic dendrimers.
1
nikon. The selected m/z values given refer to the isotopes H,
12C, 28Si, 32S, and 120Sn. In all cases, the isotopic distribution
pattern was checked against the theoretical distribution.
Elemental analyses were performed using a Carlo Erba
EA1108 elemental analyzer in the microanalytical laboratory
of the University of Cape Town.
Syn th esis of 1. A mixture of 5 (4.92 g, 27 mmol), 3 (1.5
mL, 6.48 mmol), and Karstedt catalyst solution (200 µL) was
heated to 120 °C for 18 h.21 The volatiles were removed in
vacuo at 140 °C, leaving a colorless oil and a black precipitate.
The oil was filtered over a pad of silica gel, eluting with
hexane. Removal of the volatiles in vacuo gave 1 as a colorless
oil. Yield: 5.79 g (97%). IR (cm-1): 3072 (w, ν(CHar)), 3057
(w, ν(CHar)), 3016, 2952 (s, νas(CH3)), 2911 (s, νas(CH2)), 1934
(w), 1851 (w), 1784 (w), 1717 (w) (monosubstituted benzene),
1581 (m, ν(CdC)), 1479 (m, ν(CdC)), 1438 (s, δas(CH2)), 1390,
1333, 1249 (s, δs(CH3)), 1138, 1085, 1067, 1025, 982, 943, 909,
844 (s, ν(SiMe2)), 736 (s, γ(CH)), 697, 689 (s, γ(CH)), 668 (S-
Isolation of 11 via the tin/lithium exchange reaction
was hampered by the increased sensitivity of the
compound. In our hands we always found observable
traces of decomposition in the NMR spectra of 11,
presumably due to reaction with traces of moisture and/
or oxygen during workup.
1
C), 472. H NMR (CDCl3, 400 MHz): δ 0.06 (24 H, s, 8 Me),
3
3
0.55 (8 H, m, J (H,H) ) 8 Hz, 4 CH2Si), 0.70 (8 H, m, J (H,H)
) 8 Hz, 4 SiCH2), 1.30 (8 H, m, 4 CH2CH2CH2), 2.09 (8 H, s,
4 CH2S), 7.3-6.9 (20 H, m, 4 Ph). 13C{1H} NMR (CDCl3, 75.5
MHz): δ -3.2 (8 C, 8 Me), 17.2 (4 C, 4 CH2S), 17.4 (4 C, 4
CH2Si), 18.5 (4 C, 4 SiCH2), 19.9 (4 C, 4 CH2CH2CH2), 124.6
(4 C, C-4 of SPh), 126.1 (8 C), 128.6 (8 C) (C-2, -6 and C-3, -5
of SPh), 140.4 (4 C, C-1 of SPh). 29Si{1H} NMR (CDCl3, 79.45
MHz): δ 0.95 (1 Si, SiCH2), 2.04 (4 Si, SiMe2). MS (FAB): m/z
919 (0.5, M+ - H), 905 (2, M+ - CH3), 811 (3, M+ - SPh), 797
(100, M+ - CH2SPh), 697 (30, M+ - C3H6Si(Me2CH2SPh), 589
Con clu sion s
Dendrimers containing four and 12 phenylthiomethyl
functionalities have been prepared. These dendrimers
react with lithium naphthalenide in a C-S bond-
cleavage reaction to give lithiomethyl-functionalized
dendrimers. The dendrimer with four functionalities
was derivatized by reaction with various trialkylsilyl
and -stannyl chlorides. The dendrimer with 12 func-
tionalities was derivatized by reaction with tributyltin
chloride. The tetrakis(tributyltin) dendrimer was sub-
sequently reacted with butyllithium to give the lithio-
(17) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-
sensitive Compounds; Wiley-Interscience: New York, 1986; p 80.
(18) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: Oxford, 1988.
(19) Van der Made, A. W.; Van Leeuwen, P. W. N. M. J . Chem. Soc.,
Chem. Commun. 1992, 1400.
(20) (a) Chandra, G.; Lo, P. Y.; Hitchcock, P. B.; Lappert, M. F.
Organometallics 1987, 6, 191. (b) Hitchcock, P. B.; Lappert, M. F.;
Warhurst, N. J . W. Angew. Chem., Int. Ed. Engl. 1991, 30, 438.
(21) The reaction was followed by monitoring the disappearance of
the peak at 1610 cm-1 in the IR spectrum of the mixture (associated
with ν(CdC)).
(15) Connolly, J . W.; Urry, G. Inorg. Chem. 1963, 2, 645.
(16) Hartwell, G. E.; Brown, T. L. Inorg. Chem. 1964, 3, 1656.

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1814 Organometallics, Vol. 22, No. 9, 2003
Meijboom et al.
(2, M+ - CH2SPh - C2H4SiMe2CH2SPh), 575 (2, M+ - CH2-
SPh - C3H6SiMe2CH2SPh), 475 (4, M+ - 2 C3H6SiMe2CH2-
SPh), 181 (80, SiMe2CH2SPh+). Anal. Calcd for C48H76S4Si5:
C, 62.54; H, 8.31; S, 13.91. Found: C, 62.1; H, 8.4; S, 13.5.
Syn t h esis of 2. Karstedt catalyst solution (100 µL) was
added to a mixture of 4 (0.50 g, 0.62 mmol) and 5 (1.5 g, 8.24
mmol), and the mixture was heated to 130 °C for 16 h. The
excess silane was distilled off in vacuo at 130 °C, and the
catalyst was removed by filtration over a pad of silica, eluting
with dichloromethane. The solvent was removed in vacuo to
m/z 776 (M+, 0.8), 705 (7), 643 (13), 566 (C28H62Si6, 60), 493
(C25H53Si5, 100), 442 (C21H50Si5, 59), 331 (C18H31Si3, 93%). Anal.
Calcd for C36H92Si9: C, 55.58; H, 11.92. Found: C, 55.8; H,
12.2.
9: colorless oil. Yield: 0.74 g (80%). IR (cm-1): 2951 (s,
νas(Me)), 2911 (s, νas(CH2)), 2875 (s, νs(Me)), 1448 (m, δs(Me)),
1412, 1357, 1333, 1246 (s, δs(SiMe)), 1215, 1188 (m, δs(SnMe)),
1141, 1079, 998, 941, 906, 833 (s, νas(SiC)), 772, 720, 581, 524
(s, νas(SnC)). 1H NMR (CDCl3, 400 MHz): δ -0.26 (8 H, s,
2J (H,Sn) ) 56 Hz, 4 SiCH2Sn); -0.02 (24 H, s, 4 SiMe2), 0.10
(36 H, s, 4 SnMe3), 0.58 (16 H, t, 3J (H,H) ) 8 Hz, 8 SiCH2),
1.34 (8 H, m, 4 CH2CH2CH2). 13C{1H} NMR (CDCl3, 100.6
1
give 2 as a colorless oil. Yield: 1.79 g (96%). H NMR (CDCl3,
300 MHz): δ 0.11 (72 H, s, 24 Me), 0.59 (40 H, m, 20 CH2Si),
0.75 (24 H, m, 12 CH2SiMe2), 1.45-1.20 (32 H, m, 16 CH2CH2-
CH2), 2.13 (24 H, s, 12 SCH2), 7.3-7.0 (60 H, m, 12 SPh). 13C-
{1H} NMR (CDCl3, 75.5 MHz): δ -3.1 (24 C, 8 Me), 17.2 (12
C, 4 CH2S), 17.4 (12 C, 4 CH2Si), 18.5 (12 C, 4 SiCH2), 19.9
(12 C, 4 CH2CH2CH2), 124.6 (12 C, C-4 of SPh), 126.1 (24 C),
128.6 (24 C)(C-2, -6 and C-3, -5 of SPh), 140.4 (12 C, C-1 of
SPh), The “core” propyl chain was not visible due to low intens-
ity of the signal. 29Si{1H} NMR (CDCl3, 79.45 MHz): δ 0.50 (1
Si, Si(CH2)4), 0.76 (4 Si, SiCH2), 1.99 (12 Si, SiMe2). Anal. Calcd
for C156H252S12Si17: C, 62.67; H, 8.50. Found: C, 63.0; H, 8.6.
Syn th esis of 6, 8, 9, a n d 10. The preparation of 6, 8, 9
and 10 all followed the same general method; a representative
preparation is given for 6.
1
MHz): δ -8.00 (4 C, J (C, 119/117Sn) ) 202/193 Hz, SiCH2Sn),
-5.65 (12 C, 4 SnMe3), -0.22 (8 C, 4 SiMe2), 17.65 (4C,
SiCH2C), 18.75 (4 C, SiCH2C), 22.24 (4 C, CH2CH2CH2).
29Si{1H} NMR (CDCl3, 79.45 MHz): δ 0.82 (1 Si, Si(CH2)4),
4.07 (4 Si, 4 SiMe2). Anal. Calcd for C36H92Si5Sn4: C, 37.95;
H, 8.13. Found: C, 38.1; H, 8.4.
10: colorless oil. Yield: 0.992 g, (92%), Rf(silica/hexane) 0.95.
IR (cm-1): 2954 (s, νas(Me)), 2921 (s, νas(CH2)), 2871 (s, νs(Me)),
2853 (s, νs(CH2)), 1464 (s, δas(CH2)), 1416, 1376 (s, δs(Me)),
1356, 1339, 1291, 1246 (s, δs(SiMe3)), 1214, 1180, 1142,
1070, 1043, 992. 960, 906, 861, 831 (s, ν(SiMe2)), 770,
723 (s, δ((CH2)x)), 689, 668, 592 (s, ν(SnC)), 506 (s, νas(SnC)).
1H NMR (CDCl3, 400 MHz): δ -0.40 (8 H, s, 2J (H,Sn) ) 56
Hz, 4 SiCH2Sn), -0.09 (24 H, s, 4 SiMe2), 0.50 (16 H, m, 8
SiCH2C), 0.95-0.68, 1.5-1.2 (116 H, m, SnCH2C, CCH2C,
CCH2Me, CMe, SiCCH2). 13C{1H} NMR (CDCl3, 100 MHz): δ
-8.8 (4 C, 1J (C,119/117Sn) ) 202/193 Hz, 4 SiCH2Sn), -0.1 (8
C, 3J (C,119/117Sn) ) 12.0/10.6 Hz, 4 SiMe2), 10.4 (12 C,
1J (C,119/117Sn) ) 323.6/309.8 Hz, 4 Sn(CH2C)3), 13.7 (12 C, 12
CMe), 17.7 (4 C, 4 SiCH2C), 18.8 (4 C, 4 SiCH2C), 23.5 (4 C,
4 SiCH2CH2CH2), 27.5 (12 C, 2J (C,119/117Sn) ) 58.2/55.0 Hz,
12 CH2Me), 29.2 (12 C, 3J (C,119/117Sn) ) 20.0/18.4 Hz, 4
Sn(CH2CH2)3). 29Si{1H} NMR (CDCl3, 79.45 MHz) δ 0.59 (1
Si, SiCH2), 3.10 (4 Si, 2J (Si,Sn) ) 22.9 Hz, 4 SiCH2Sn). MS
(FAB): m/z fragments only. Anal. Calcd for C72H164Si5Sn4: C,
52.56; H, 10.04. Found: C, 53.0; H, 9.4.
Syn th esis of 6. Lithium metal pieces (0.090 g, 13 mmol)
were added to a solution of naphthalene (0.090 g, 0.70 mmol)
in THF (5 mL) at 0 °C and stirred for 30 min. A dark green
solution of lithium naphthalenide developed seconds after
adding the metal. A solution of 1 (0.600 g, 0.65 mmol) in THF
(4 mL) was added at such a rate that the green color of lithium
naphthalenide did not disappear ((1 h). The mixture was
cooled to -40 °C, and D2O (2.0 mL) in THF (2.0 mL) was
added. The color of the lithium naphthalenide disappeared
completely within seconds to leave a colorless/gray solution.
The volatiles were removed in vacuo, and the products were
partitioned between hexane (10 mL) and water (10 mL). The
aqueous layer was extracted with hexane (3 × 10 mL), and
the organic phases were combined. The organic phase was
washed successively with water (3 × 10 mL), dilute aqueous
NaOH (3 × 10 mL), water (3 × 10 mL), and brine (3 × 10
mL), dried over MgSO4, and filtered, and the volatiles were
evaporated in vacuo. The bulk of the naphthalene was
sublimed out of the product at 150 °C, 10-3 mmHg. Chroma-
tography over silica gel, eluting with hexane, gave 6 as a
colorless oil. Yield: 0.265 g (83%). 1H NMR (CDCl3, 400
MHz): δ -0.12 (8 H, t, 2J (D,H) ) 2 Hz, 4 CH2D), -0.10 (24 H,
Syn th esis of 12. Lithium metal pieces (0.100 g, 14.5 mmol)
were added to a solution of naphthalene (0.100 g, 0.78 mmol)
in THF (5 mL) at 0 °C and stirred for 30 min. A dark green
solution of lithium naphthalenide developed seconds after
adding the metal. A solution of 2 (0.600 g, 0.201 mmol) in THF
(3 mL) was added at such a rate that the green color of lithium
naphthalenide did not disappear ((1 h). The resulting solution
was cooled to -40 °C, and tributyltin chloride (1.0 mL, 3.7
mmol) was added quickly. The color disappeared completely
within seconds to leave a colorless/gray solution. The volatiles
were removed in vacuo, and the products were suspended in
hexane (5 cm3). The solution was filtered over a pad of alumina,
eluting with hexane. The volatiles were evaporated in vacuo,
and the residual tributyltin chloride was distilled off at 230
°C/0.01 mmHg. Chromatography over silica gel, eluting with
hexane, gave 12 as a colorless oil. Yield: 0.992 g (92%). 1H
3
s, 8 Me), 0.49 (16 H, m, J (H,H) 8 Hz, 4 CH2Si), 1.27 (8 H, m,
4 CH2CH2CH2). 13C{1H} NMR (CDCl3, 100.6 MHz): δ -1.9 (4
1
C, t, J (C,D) ) 18 Hz, 4 CH2D), -1.6 (8 C, 8 Me), 17.5 (4 C, 4
CH2Si), 18.6 (4 C, 4 CH2Si), 21.6 (4 C, 4 CH2CH2CH2).
29Si{1H} NMR (CDCl3, 79.45 MHz): δ 0.50 (1 Si, SiCH2), 0.74
(4 Si, SiMe2). MS (FAB): m/z 492.37854 (M+) (C24H56D4Si5
requires 492.37925), 462 (M+ - 2Me), 376 (M+ - C3H6SiMe2-
CH2D), 361 (M+ - C3H6SiMe2CH2D - CH3), 260 (M+ - 2C3H6-
SiMe2CH2D), 186 (C3H6SiC3H6SiMe2CH2D+), 144 (SiC3H6-
SiMe2CH2D+), 100 (SiC3H6SiMe2+), 74 (SiMe2CH2D+). Anal.
Calcd for C24H56D4Si5: C, 58.45; H, 11.44. Found: C, 59.1; H,
11.7.
2
NMR (CDCl3, 400 MHz): δ -0.34 (24 H, s, J (H,Sn) ) 56 Hz,
12 SiCH2Sn), -0.02 (72 H, s, 24 Me), 0.55 (64 H, m, 32
SiCH2C), 0.95-0.68, 1.5-1.2 (116 H, m, SnCH2C, CCH2C,
CCH2Me, CMe, SiCCH2). 13C{1H} NMR (CDCl3, 100.6 MHz):
8: colorless oil. Yield: 0.461 g (87%). IR: (cm-1) 2952 (s,
νas(Me)), 2911 (s, νas(CH2)), 1448 (m, δas(CH2)), 1412 (m), 1353
(m), 1333 (m), 1250 (s, δs(Me)), 1141 (m), 1051 (s), 983 (w),
943 (w), 909 (s), 837 (vs br, ν(SiMe3)), 789 (s), 762 (s, ν(SiMe3)),
1
δ -8.7 (4 C, J (C,119/117Sn) ) 202/193 Hz, 4 SiCH2Sn); -0.1 (8
C, 3J (C,119/117Sn) ) 12.0/10.6 Hz, 4 SiMe2), 10.4 (12 C,
1J (C,119/117Sn) ) 323.6/309.8 Hz, 4 Sn(CH2C)3), 13.7 (12 C,
12 CMe), 17.7 (4 C, 4 SiCH2C), 18.8 (4 C, 4 SiCH2C), 23.5
1
687 (s), 614 (w), 589 (w), 553 (w). H NMR (CDCl3, 400 MHz):
δ -0.29 (8 H, s, 4 SiCH2Si), 0.00 (24 H, s, 4 SiMe2), 0.03 (36
2
(4 C, 4 SiCH2CH2CH2), 27.5 (12 C, J (C,119/117Sn) ) 58.2/55.0
3
H, s, 4 SiMe3), 0.57 (16 H, m, J (H,H) ) 8 Hz, 8 CH2Si), 1.35
Hz, 12 CH2Me), 29.2 (12 C, 3J (C,119/117Sn) ) 20.0/18.4 Hz, 4
Sn(CH2CH2)3). Anal. Calcd for C228H516Si17Sn12: C, 53.07; H,
10.08. Found: C, 53.3; H, 9.9.
(8 H, m, 4 CH2CH2CH2). 13C{1H} NMR (CDCl3, 100.6 MHz):
δ -0.5 (8 C, 4 SiMe2), 1.4 (12 C, 4 SiMe3), 2.8 (4 C, 4 SiCH2-
Si), 17.7 (4 C, 4 CH2Si), 18.7 (4 C, 4 CH2Si), 23.0 (4 C, 4
CH2CH2CH2). 29Si{1H} NMR (CDCl3, 79.45 MHz): δ 0.5 (1 Si,
Si(CH2)4), 0.82 (4 Si, 4 SiMe3), 1.0 (4 Si, 4 SiMe2). MS (EI):
Syn th esis of 7. A solution of BuLi in hexane (450 µL, 2.2
M, 0.99 mmol) was added to a solution of 10 (0.360 g, 0.224