Synthesis and Characterization of Lipophilic Organotins
Organometallics, Vol. 26, No. 23, 2007 5579
A universal liquid IR cell OMNICELL (Eurolabo) and KBr pellets
were used to record solution and solid-state IR spectra, respectively.
the ratio of these values, which is equal to 1.5, closely matched
the ratio of the chain density determined for 2 and 1, i.e., 2.1
and 1.4 chain‚nm-2, respectively. This result strongly suggests
that the chain loading is governed by the cross-sectional area
of the chain linked to the tin center, assessing the validity of
our approach. Finally, it must also be emphasized that the
reaction rate of 2 with silica was slower than that found with 1.
Indeed, in this study, the reaction is complete after 6 days,
whereas 1 furnished maximum chain loadings after 17 h. This
could be rationalized by considering that the weak electron-
donating alkyl chain slightly diminished the electrophilicity of
the tin center, whereas the latter was enhanced by the electron-
withdrawing perfluoroalkyl chain, which would favor the
nucleophilic attack of hydroxylated species at the tin atom.
Tricyclohexyldocosyltin, 4. In a three-necked flask, n-butyl-
lithium (2.5 M) in hexane (10 mL, 25.0 mmol) was added to
diisopropylamine (2.6 g, 25.7 mmol) in 20 mL of THF at 0 °C.
After stirring for 15 min at this temperature, tricyclohexyltin hydride
(8 g, 21.6 mmol) in THF (20 mL) was added drop by drop, and
stirring was continued for 30 min. At 0 °C, 1-bromodocosane (7.6
g, 19.5 mmol) in THF (30 mL) was then added. The mixture was
warmed to room temperature and stirred for a further 20 h. After
hydrolysis with a saturated solution of NH4Cl, the mixture was
extracted into petroleum ether, and the resulting organic phases
were washed with water (3 × 80 mL) and dried over MgSO4 to
give a white solid after evaporation of the solvent. Recrystallization
from absolute ethanol gave a white powder. Yield: 9.75 g (74%),
mp 71 °C.
1H NMR (300 MHz, CDCl3, 293 K): δ 0.83 (m, 2H, H1), 0.92
(t, 7.2, 3H, H22); 1.29-1.89 (m, 73H, Ha, Hb, Hc, Hd, H2-21). 13C
NMR (74.5 MHz, CDCl3, 293 K): δ 6.8 ([260], C1), 14.1 (C22),
22.7 (C20 or C21), 25.9 ({[313], Ca), 27,3 (Cd), 29.2 (C2), 29.3 ([51],
Cc), 29.4 (C4-19), 31.9 (C20 or C21), 32.4 ([18], Cb), 35 (C3). 119Sn
NMR (74.5 MHz, CDCl3, 293 K): δ -64.4. Anal. Found (Calcd
for C40H78Sn): C 70.4 (70.9), H 11.6 (11.6), Sn 17.5 (17.5).
Triphenyldocosyltin, 5. In a three-necked flask under a nitrogen
atmosphere was prepared a Grignard reagent from 1-bromodocosane
(10 g, 12.8 mmol) and magnesium (1.2 g, 50 mmol) in THF (16
mL). The mixture was refluxed for 15 min and then was added
slowly via canula to a solution of triphenyltin chloride (7.9 g, 20.5
mmol) in THF (16 mL) cooled to 0 °C. Then, the mixture was
allowed to return to room temperature and was then heated at reflux
for 1 h. After hydrolysis with a saturated soluation of NH4Cl, the
usual workup (extraction into petroleum ether, washings with water,
drying over MgSO4) followed by column chromatography over
silica gel (elution gradient petroleum ether/ethyl acetate from 100:0
to 97:3 (v/v)) afforded the expected compound as a white solid.
Yield: 7.2 g (53%), mp 83 °C.
1H NMR (300 MHz, CDCl3, 293 K): δ 1.00 (t, 6.8, 3H, H22),
1.28-1.48 (m, 38H, H3-21), 1.63 (m, 2H, H1), 1.82 (m, 2H, H2),
7.42 (m, 9H, Hc,d), 7.63 (m, 6H, Hb). 13C NMR (74.5 MHz, CDCl3,
293 K): δ 11.2 ([397], C1), 14.1 (C22), 22.7 (C21), 26.6 ([23], C2),
29.1-29.7 (C4-19), 31.9 (C20), 34.2 ([60], Cb), 128.4 ([35], Cb),
128.8 ([11], Cd), 137.0 ([48], Cc), 139.2 ([480], Ca). 119Sn NMR
(74.6 MHz, CDCl3, 293 K): δ -100.1. Anal. Found (Calcd for
C40H60Sn): C 73.1 (72.8), H 9.2 (9.2), Sn 18.5 (18.0).
Trichlorodocosyltin, 3. Procedure A: In a three-necked flask,
tin tetrachloride (3.7 g, 14.3 mmol) was added drop by drop to a
solution of tricyclohexyldocosyltin (4) (9.7 g, 14.3 mmol) in CH2-
Cl2 (100 mL). The reaction mixture was refluxed overnight. After
evaporation of the solvent and sublimation of the tricyclohexyltin
chloride formed, the expected compound 3 was isolated as a waxy
solid. Yield: 6.4 g (83%).
Conclusion
New lipophilic tetraorgano- and trichloroorganotins have been
synthesized and thoroughly characterized. Docosyltrihex-1-
ynyltin(IV) achieved the chemical functionalization of silica
surfaces, yielding modified silica powders. The cleavage of the
three alkynyl functionalities and the concomitant formation of
-Sibulk-O-Sn-C- linkages led to the irreversible chemisorp-
tion of the organotin precursor, providing a maximum alkyl
chain loading of 0.34 mmol‚g-1, i.e., 2.1 chain‚nm-2. A
comparisonoftheresultsobtainedwithdocosyl-and(1H,1H,2H,2H-
heptadecafluorodecyl)trihex-1-ynyltins revealed that the chain
loading can be rationalized by considering the cross-sectional
areas of the different chains, which were inferred from the X-ray
structure data of the precursors.
These results impart versatility to our method based on
alkynylorganotins and allow one to add specific organic
functionalities to oxide surfaces such as silica or tin dioxide,
widening the scope of the precursors available to design
functional hybrid materials.
Experimental Section
General Procedures and Starting Materials. Each chemical
used was purchased from Aldrich or Acros and used without further
purification. Tricyclohexyltin chloride was synthesized from tri-
cylohexyltin hydroxide (Phyteurop) according to a literature
procedure.23 Compound 1 has been prepared as previously described.9a
All reactions involving air- and/or moisture-sensitive compounds
were carried out using standard Schlenk-line techniques under an
atmosphere of nitrogen. THF and toluene were distilled from sodium
benzophenone ketyl prior to use. Acetonitrile, chloroform, dichlo-
romethane, and n-hexane were refluxed over CaH2 and collected
by distillation. Diisopropylamine was distilled on KOH.
Instrumentation. 1H and 13C{1H} NMR spectra were recorded
on a Bruker DPX-300 spectrometer in CDCl3 at room temperature
1
with Me4Si as internal reference. H and 13C assignments were
1
confirmed when necessary with the use of two-dimensional H-
1H COSY, 13C-1H HMQC, and 13C-1H HMBC NMR experiments.
119Sn NMR spectra were recorded at 74.6 MHz (solvent CDCl3,
internal reference Me4Sn). Chemical shifts are quoted in δ (ppm),
coupling constants in hertz, while “s” stands for singlet, “d” for
doublet, “dd” for doublet of doublets, “t” for triplet, and “m” for
multiplet. Tin-carbon coupling constants (Hz) are given in brackets.
Mass spectrometry data were collected with a VG Autospec-Q
working in the electronic impact mode. Elemental analyses were
carried out in the Center of Chemical Analysis of the CNRS
(Vernaison, France). Infrared spectra were performed in the
absorption mode using a FTIR Perkin-Elmer spectrophotometer.
Procedure B: In a Schlenk tube under a nitrogen atmosphere,
docosyltriphenyltin (4) (3.55 g, 5.4 mmol) was mixed with 40 mL
of concentrated hydrochloric acid and heated at 60 °C for 3 days
under magnetic stirring. The reaction mixture was cooled to room
temperature and the solvent removed under reduced pressure. The
(23) Pommier, J. C.; Pereyre, M.; Valade, J. C. R. Acad. Sci. 1965, 260,
6397.