Preparation, reactivities, and NMR spectra of pentafluorophenyltin derivatives

Article abstract of DOI:10.1016/S0022-328X(98)00928-0

A variety of pentafluorophenyltin compounds were prepared and their chemical properties were examined. These compounds effectively catalyzed Mukaiyama-aldol reaction of ketene silyl acetal in sharp contrast to the inertness of normal alkyltin halides like Bu₂SnCl₂. The increased Lewis acidity of the pentafluorophenyltin halides was proved by ¹¹⁹Sn- and ¹³C-NMR spectra. On the other hand, the pentafluorophenyl group reduced the reactivities of tin towards both nucleophiles and electrophiles. ¹⁹F-NMR spectroscopy was invoked to elucidate this anomaly.

Full text of DOI:10.1016/S0022-328X(98)00928-0

Journal of Organometallic Chemistry 574 (1999) 58–65
Preparation, reactivities, and NMR spectra of pentafluorophenyltin
derivativesꢀ
Jian-xie Chen, Katsumasa Sakamoto, Akihiro Orita, Junzo Otera *
Department of Applied Chemistry, Okayama Uni6ersity of Science, Ridai-cho, Okayama 700-0005, Japan
Received 8 June 1998; received in revised form 3 August 1998
Abstract
A variety of pentafluorophenyltin compounds were prepared and their chemical properties were examined. These compounds
effectively catalyzed Mukaiyama-aldol reaction of ketene silyl acetal in sharp contrast to the inertness of normal alkyltin halides
like Bu2SnCl2. The increased Lewis acidity of the pentafluorophenyltin halides was proved by 119Sn- and 13C-NMR spectra. On
the other hand, the pentafluorophenyl group reduced the reactivities of tin towards both nucleophiles and electrophiles. 19F-NMR
spectroscopy was invoked to elucidate this anomaly. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: NMR spectra; Pentafluorophenyltin derivatives; Mukaiyama-aldol reaction
1. Introduction
Several pentafluorophenyltin compounds are known
[3–7]. Their chemical properties have also been re-
vealed to some extent but not comprehensively. In this
paper, we report the general and convenient method for
preparation of various pentafluorophenyltin derivatives
and their unique features that are different from normal
organotin compounds. Their Lewis acidity is assessed in
terms of the Mukaiyama aldol reaction. Moreover,
reactions with nucleophiles and electrophiles are exam-
ined. These reactivity profiles are discussed on the basis
of NMR spectra.
Despite their availability, alkyltin halides have sel-
dom worked as Lewis acids in organic synthesis on
account of their weak acidity [1]. We had postulated
that incorporation of pentafluorophenyl groups on tin
should increase the acidity. In fact, (C6F5)2SnBr2
proved the validity of this postulation [2]. A variety of
nucleophilic reactions of silyl and stannyl reagents were
effectively catalyzed by this compound under mild con-
ditions, thus allowing otherwise difficult-to-achieve dif-
ferentiations between various carbonyls or between
carbonyl and acetal. The catalyst is hydrolytically sta-
ble enough to be isolated by column chromatography
or recrystallization in open air. This is quite unique
because most of the conventional Lewis acids that are
sufficiently acidic to promote synthetically useful reac-
tions are readily hydrolyzed. We were intrigued by
these results to further expand the scope of our investi-
gation on relevant pentafluorophenyltin compounds.
2. Results and discussion
2.1. Synthesis
The precedent methods to prepare pentafluoropheny-
ltin halides basically had recourse to treatment of SnCl4
with C6F5MgBr [3,4]. Quite naturally, it is not easy to
obtain a single product by this procedure: usually
(C6F5)3SnCl and (C6F5)2SnCl2 constitute a major frac-
tion of the product mixture even if the stoichiometry of
the Grignard reagent was adjusted to produce one of
ꢀ Dedicated to the late Professor Rokuro Okawara, a pioneer of
organotin chemistry.
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00928-0

J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
59
these halides. One exceptional method involved the
(3)
selective cleavage of the p-tolyl group in p-tolyltris(pen-
tafluorophenyl)tin to furnish (C6F5)3SnCl [5]. Now, we
have explored more general routes to arrive at pen-
tafluorophenyltin halides 1–5 utilizing readily cleavable
allyl and benzyl groups. Allylpentafluorophenyltin
derivatives 6 and 7 were produced using allyltin chlo-
rides that could be conveniently prepared by redistribu-
tion of commercially available (CH2ꢀCHCH2)4Sn and
SnCl4 [8]. Exposure of these allyltin chlorides to an
excess of C6F5MgBr [6,9] provided 6 and 7 quantita-
tively (Eqs. (1) and (2)). Treatment of these compounds
with bromine furnished sole products (C6F5)3SnBr (1)
and (C6F5)2SnBr2 (2), respectively (Eqs. (3) and (4)).
Reaction of 7 with HCl gas proceeded smoothly at
room temperature (r.t.) to give (C6F5)2SnCl2 (4) (Eq.
(5)) while the reaction of 6 should be run at refluxing
temperature in CCl4 to give (C6F5)3SnCl (3) (Eq. (7))
(vide infra for the detailed discussion). The conversion
of 7 to 4 was also effected by use of ICl though the
yield was somewhat lower (Eq. (6)). Benzyltin deriva-
tives serve as well. Thus, action of C6F5MgBr on
(C6H5CH2)2SnCl2, that is feasible from benzyl chloride
and tin powder [10], led to 8 (Eq. (8)). Exposure of this
compound to bromine offered another access to 2 (Eq.
(9)). Notably, this route is somewhat better than the
allytin protocol (Eq. (4)) because a by-product, 1,2,3-
tribromopropane forms occasionally if the amount of
Br2 deviates from the pinpoint stoichiometry. Separa-
tion of this by-product from 2 by column chromatogra-
phy is rather difficult. However, the allyltin method
for 1 (Eq. (3)) has no problem since 1,2,3-tribro-
mopropane, if formed, can be readily separated from
1. In addition, the benzyltin method was applied
to produce C6F5SnBr3 (5) from C6F5Sn(CH2C6H5)3
(9) (Eq. (10)). The requisite 9 was prepared by the
Grignard reaction with tribenzyltin chloride that is also
readily available from benzyl chloride and tin powder
[10]. The selective cleavage of one of the benzyl groups
in 8 afforded mixed triorganotin chloride 10 (Eq. (11)).
The three methods employed here gave rise to virtually
no difference in yield. In all of the above cases, the
desired compounds were isolated solely without con-
tamination of by-products. The compounds thus ob-
tained are stable to hydrolysis and can be purified by
column chromatography or recrystallization in open
air.
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
2.2. Acti6ity as Lewis acid catalysts
The catalytic activity of pentafluorophenyltin com-
pounds was assessed for the aldol reaction of acetophe-
none with ketene silyl acetal (Table 1). It is rather
surprising that (C6F5)4Sn [6] exhibited no activity (entry
1) because a considerable degree of the acidity is ex-
pected from the estimated order of electron-withdraw-
ing power: Cl\C6F5\Br [4]. Replacement of one of
the C6F5 groups with bromine dramatically improves
the activity (entry 2). The dihalides gave rise to further
increase of the yield (entries 3 and 4) but a lower yield
was obtained with tribromide 5. It follows from these
reactivity profiles that the catalytic activity cannot be
straightforwardly associated with the electron-with-
drawing power. Diallyl- and dibenzyltin derivatives 7
and 8 afforded poor yields (entries 6 and 7). Notably,
both 2 and 4 are the first diorganotin dihalides that
function as Lewis acids in the synthetically useful reac-
tion. More remarkable is the effectiveness of 1 since
usually triorganotin halides are not employable in or-
ganic synthesis due to the weak acidity. In this regard,
(1)
(2)

60
J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
Table 1
the acceptor property by incorporation of the C6F5
groups.
Reaction of ketene ethyl tert-butyldimethylsilyl acetal with acetophe-
none catalyzed by pentafluorophenyltin derivativesa
2.3. Reacti6ity
There appeared several reports which referred to the
reactivities of pentafluorophenyltin derivatives [4–7].
These studies, however, were focused mostly on eluci-
dation of the characteristics of the Sn–C6F5 bond itself.
We disclose herein that the C6F5 group exerts signifi-
cant influences on the reactivities of other residues
attached on tin. As shown in Eq. (12), pen-
tafluorophenyltin bromides 1 and 2 underwent no reac-
tion with NaOMe. This stands in sharp contrast to
normal organotin halides that are readily converted to
the methoxides under the same reaction conditions.
Analogously, no reaction occurred with sodium N,N-
diethyldithiocarbamate (Eq. (13)). The replacement of
the bromines in 2 with nucleophiles was achievable only
when silver salts were employed. Thus, dithiocabamate
11 could be obtained by use of silver N,N-diethyldithio-
carbamate (Eq. (14)). The C6F5 group also suppressed
the nucleophilic attack by Grignard and organozinc
reagents. Reaction with C6H5MgBr was monitored by
TLC and the reactivity was qualitatively assessed in
terms of the reaction temperature and time required for
disappearance of the pentafluorophenyltin halides [12].
It turned out that the reactivity increases with the
decrease in the number of the C6F5 group: 1B2B5
(Eqs. (15) (16) and (17)). A similar trend holds in the
reaction with Et2Zn (Eqs. (18) (19) and (20)). Appar-
ently, the reactivity of 1 and 2 towards nucleophiles is
low in spite of the strong acidity of tin compared to
normal organotin halides.
Entry
L.A.
Yield (%)b
1
2
3
4
5
6
7
(C6F5)4Sn
(C6F5)3SnBr (1)
(C6F5)2SnBr2 (2)
(C6F5)2SnCl2 (4)
C6F5SnBr3 (5)
0
71
92
93
77
10
4
(C6F5)2Sn(CH2CHꢀCH2)2 (7)
(C6F5)2Sn(CH2C6H5)2 (8)
a Reaction conditions; ketone:ketene silyl acetal:L.A. was
1.0:1.3:0.1, Ch2Cl2, −78°C, 4 h.
b Isolated yield.
we conclude that the C6F5 group is effective for increas-
ing the Lewis acidity but, unfortunately, not so power-
ful as chlorine and bromine.
To get further insight into this aspect, the interac-
tions between the organotin halides with carbonyls
were probed by 119Sn- and 13C-NMR (Table 2) [11].
Upon addition of five equivalents of acetophenone or
propanal, the 119Sn signal of 2 experienced appreciable
upfield shifts [Dl (119Sn)] which reflected the increase in
coordination number of tin. On the other hand, much
smaller variations were observed with Bu2SnCl2 that
was catalytically inactive for the aldol reaction. The
variation of 13C chemical shifts of the carbonyl carbon
[Dl (13C)] is in accord with the 119Sn-NMR. The l
values moved downfield appreciably upon mixing with
2 whereas only slight or virtually no change was in-
duced with Bu2SnCl2. Obviously, the pen-
tafluorophenyltin compound undergoes stronger
coordination than Bu2SnCl2 indicative of the increase in
In addition to the above nucleophilic reactions, the
pentafluorophenyltin compounds are also reluctant to
undergo electrophilic attacks. As described already, the
tin–allyl bond in 7 was readily cleaved by HCl gas at
r.t. (Eq. (5)). Under the same conditions no reaction
took place with 6 and the refluxing temperature in
Table 2
Organotin/carbonyl interaction studied by 119Sn- and 13C-NMR spectraa
l (119Sn)
Dl (119Sn)b
l (13C)c
Dl (13C)b
(C6F5)2SnBr2 (2)
−236
Bu2SnCl2
127
PhCOMe
C2H5CHO
(C6F5)2SnBr2 (1.0)+PhCOMe (5.0)
(C6F5)2SnBr2 (1.0)+C2H5CHO (5.0)
Bu2SnCl2 (1.0)+PhCOMe (5.0)
Bu2SnCl2 (1.0)+C2H5CHO (5.0)
197.6
202.7
198.4
204.6
197.7
203.2
−358
−356
85
−122
−120
−42
0.8
1.9
0.1
0.5
74
−53
a In dry CH2Cl2 with Me4Sn and Me4Si as internal standards at r.t.
b Change of chemical shifts upon coordination.
c The chemical shift of carbonyl carbon.

J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
61
Table 3
19F-NMR spectra of pentafluorotin compoundsa
lp (Dl)b
lm (Dl)b
lo (Dl)b
(C6F5)4Sn
−82.4
−93.8
−57.6
(C6F5)3SnBr (1)
(C6F5)2SnBr2 (2)
(C6F5)3SnCl (3)
(C6F5)2SnCl2 (4)
(C6F5)3SnCH2CHꢀCH2 (6)
(C6F5)2Sn(CH2CHꢀCH2)2 (7)
(C6F5)2Sn(CH2C6H5)2 (8)
C6F5Sn(CH2C6H5)3 (9)
(C6F5)2Sn(C6H5)2 (13)
(C6F5)2Sn(SSCNEt2)2 (11)
(C6F5)2Sn(Cl)CH2C6H5 (10)
−81.4 (1.0)
−80.7 (1.7)
−81.4 (1.0)
−80.6 (1.8)
−84.1 (−1.7)
−85.8 (−3.4)
−86.0 (−3.6)
−87.3 (−4.9)
−85.5 (−3.1)
−91.2 (−8.8)
−83.4 (−1.0)
−93.5 (0.3)
−93.4 (0.4)
−93.5 (0.3)
−93.4 (0.4)
−94.6 (−0.8)
−95.3 (−1.5)
−95.6 (−1.8)
−96.0 (−2.2)
−95.1 (−1.3)
−97.6 (−3.8)
−94.7 (−0.9)
−57.2 (0.4)
−58.3 (−0.7)
−57.8 (−0.2)
−58.4 (−0.8)
−57.2 (0.4)
−57.1 (0.5)
−56.8 (0.8)
−56.2 (1.4)
−55.7 (1.9)
−64.3 (−6.7)
−57.8 (−0.2)
a In dry CH2Cl2 with CF3C6H5 as an internal standard at r.t.
b The difference from that of (C6F5)4Sn is given in the parentheses.
CC14 was required for the effective conversion (Eq.
(7)). The reactivity decreased as the number of C6F5
group was increased as was the case in the nucleophilic
reactions. The reduced reactivity of 6 is rather surpris-
ing because allyl–tin bond usually undergoes the facile
cleavage [13]. The reluctance was also observed in the
reaction of 6 with BiCl3 (Eq. (21)). This contrasts with
our finding that Bu2Sn(CH2CHꢀCH2)2 was readily con-
verted to Bu2SnCl2 on treatment with BiCl3 in benzene
at r.t. Deactivation by the C6F5 groups was not re-
stricted to the tin–allyl bond but the tin–phenyl bond
also was not cleaved by BiCl3 in refluxing benzene (Eq.
(22)) while Bu2SnPh2 was converted smoothly to
Bu2SnCl2 under the same reaction conditions [14].
(19)
(20)
(21)
(22)
2.4. 19F-NMR
(12)
(13)
With a view to obtain information about the unusual
reactivities of pentafluorophenyltin compounds,19F-
NMR spectroscopy was invoked. It is accepted that the
chemical shift (lp) of p-fluorine in the C6F5 group is
sensitive to the mesomeric effect and thus diagnostic for
the perturbation of the electronic states [15,16]. In
Table 3 these values for various pentafluorophenyltin
derivatives are given along with those of the ortho- (lo)
and meta-fluorine (lm) chemical shifts. The Dl values
given in parentheses represent the deviations from the
corresponding chemical shifts of (C6F5)4Sn. Apparently,
Dlp are larger than Dlo and Dlm [5]. The replacement
of one or two C6F5 groups in (C6F5)4Sn by halogen(s)
gave rise to downfield shifts of the lp values (positive
Dl values) while upfield shifts (negative Dl values)
resulted from the substitution by the organic groups.
These outcomes are accounted for in terms of the
difference in the conflicting resonance structures shown
below. In general, the increase in the Lewis acidity of
(14)
(15)
(16)
(17)
(18)
pentafluorophenyltin
compounds
unambiguously
reflects the major contribution of structure A.

62
J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
on Bruker-400 spectrometer with internal Me4Sn and
trifluoromethylbenzene standards, respectively. Mass
spectra were obtained with a JEOL JMS-700 mass
spectrometer. Elemental analyses were performed with
a Perkin Elmer 2400 CHN instrument.
3.1. (C6F5)3SnCH2CHꢀCH2 (6)
However, the electron-withdrawing halogens increases
the contribution of B, resulting in the downfield shift of
lp compared to that of (C6F5)4Sn whereas the electron-
donating organic groups have the opposite effect. The
superiority of pentafluorophenyltin halides to (C6F5)4Sn
in the catalytic activity suggests that the polarization by
A does not play a primary role for increasing the
acidity as compared with the electron withdrawal by
halogens. This electron-withdrawing power, further-
more, overwhelms the partial electron return induced
by B, thus serving for enhancement of the catalytic
activity. The failure of the nucleophilic displacement of
bromine in 1 and 2 (Eqs. (12) and (13)) and the
decreasing reactivity towards organometallic reagents
with increasing number of the C6F5 groups (Eqs. (15)
(16) (17) (18) (19) and (20)) would also be accommo-
dated in this notion. The mesomeric effect could coun-
terbalance, to some extent, the affinity of tin for
nucleophiles that is induced by the innate electron-with-
drawing character of the C6F5 group. The reluctance to
the electrophilic attack, on the other hand, cannot be
interpreted straightforwardly. Obviously, the relatively
large upfield shifts of l (19F) of 6 indicate the transfer
of electron from the allyl group to the C6F5 group
consistent with the decrease of reactivity. However, if
such simple interpretation is valid, allytin chlorides
should also suffer from the analogous but stronger
effect due to the higher electronegativity of chlorine
than the C6F5 group. However, this compound, in fact,
underwent the facile cleavage of the allyl group by
BiCl3 under the same conditions. As a whole, the
reactivities of pentafluorophenyltin derivatives are gov-
erned by the delicate balance of the polarity and meso-
meric effects.
To an ether solution (100 ml) of tetraallyltin (0.71 g,
2.5 mmol) was added tin chloride (1.95 g, 7.5 mmol) at
−50°C. The mixture was warmed to 0°C in 30 min.
Then, a Grignard solution in ether (50 ml) (prepared
from Mg turnings (0.96 g, 40 mmol) and C6F5Br (9.34
g, 38 mmol)) was added dropwise at 0°C. After being
stirred at r.t. for 45 h, the mixture was filtered on a
celite pad and quickly passed through a short silica gel
column (hexane). The filtrate was evaporated and the
residue was purified by column chromatography on
silica gel (hexane) to give 6 (5.67 g, 86%) m.p. 65°C.
1H-NMR l 2.85 (d, 2H, J=8.2 Hz, JSn–H=92 Hz),
4.94 (d, 1H, J=10.0 Hz), 5.07 (d, 1H, J=16.9 Hz),
5.84–5.99 (m, 1H); 119Sn-NMR: l −153.7;19F-NMR l
−57.2, −84.1, −94.6; MS (m/z) 662(M+); Anal.
calc. for C21H5F15Sn: C, 38.16; H,0.76; Found C 38.12,
H 1.12.
3.2. (C6F5)2Sn(CH2CHꢀCH2)2 (7)
To an ether solution (100 ml) of tetraallyltin (2.12 g,
7.5 mmol) was added tin chloride (1.95 g, 7.5 mmol) at
−50°C. The mixture was warmed to 0°C in 30 min.
Then, a Grignard solution in ether (50 ml) (prepared
from Mg turnings (0.91 g, 38 mmol) and C6F5Br (8.61
g, 35 mmol)) was added at 0°C. After being stirred at
r.t. for 75 h, the mixture was filtered on a pad celite and
quickly passed through a silica gel column (hexane).
The filtrate was evaporated and the residue was purified
by column chromatography on silica gel (hexane) to
give 7 (7.9 g, 98%).1H-NMR l 2.58 (d, 4H, J=8.2 Hz,
J
Sn–H=81 Hz), 4.89 (d, 2H, J=10.3Hz), 5.02 (d, 2H,
J=18.1 Hz), 5.86–6.03 (m, 2H); 119Sn NMR l
−101.6; 19F-NMR l −57.1, −85.8, −95.3; MS (m/z)
536(M+); Anal. calc. for C18H10F10Sn: C, 40.41; H,
1.88; Found C, 40.62; H, 1.84.
3. Experimental section
All reactions were performed under argon atmo-
sphere. THF and diethyl ether were distilled from
sodium benzophenone ketyl and dichloromethane was
distilled from calcium hydride prior to use. CCl4 was
distilled from P2O5 and stored over molecular sieves 4A
before use. Dibenzyltin dichloride and tribenzyltin chlo-
ride were prepared according to literature procedure
3.3. (C6F5)3SnBr (1) [4]
To a dry CCl4 solution (30 ml) of (C6F5)3SnCH2
CHꢀCH2 (5.67 g, 8.6 mmol) was added dropwise
bromine (1.36 g, 8.6 mmol) at 0°C. The mixture was
stirred at r.t. for 3 h and evaporated. The resulting
yellow oil was purified by column chromatography
(hexane followed by benzene) to give 1 (5.13 g, 86%):
m.p. 108–110°C; lit. m.p. 107–108°C; 119Sn-NMR l
−198.3; MS (m/z) 700 (M+).
1
[10]. Melting points were not corrected. H- and 13C-
NMR were recorded on Bruker-400 and Varian Ger-
mini-300 spectrometers in CDCl3 with Me4Si as an
internal standard. 119Sn- and 19F-NMR were recorded

J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
63
3.4. (C6F5)2SnBr2 (2) [4]
74 Hz), 6.93–7.18 (m, l0 H); 119Sn-NMR l
−
102.0;19F-NMR: l −56.8, −86.0, −95.6; MS (m/z):
636(M+); Anal. calc. for C26H14F10Sn, C, 49.17, H,
2.22. Found C, 48.98, H, 2.16.
To a dry CCl4 solution (20 ml) of (C6F5)2Sn(CH2
CHꢀCH2)2 (1.50 g, 2.80 mmol) was added dropwise
bromine (0.89 g, 5.60 mmol) at 0°C. The mixture was
stirred at r.t. for 1 h and evaporated. The resulting
yellow oil was purified by column chromatography
(hexane followed by benzene) to give 2 (1.54 g, 90%):
119Sn-NMR l −236.5; MS (m/z): 612 (M+); Anal.
calc. for C12Br2F10Sn: C, 23.53; found C: 23.47.
To a dry CCl4 solution (30 ml) of (C6F5)2Sn(CH2C6
H5)2 (2.5 g, 3.94 mmol) was added dropwise bromine
(1.25 g, 7.88 mmol) at 0°C. The mixture was stirred at
r.t. for 2 h and evaporated. The resulting yellow oil was
purified by column chromatography (hexane followed
by benzene) to give 2 (2.22 g, 93%).
3.8. C6F5Sn(CH2C6H5)3 (9)
To a suspension of Mg turnings (168 mg, 7 mmol) in
dry ether (10 ml) was added an ether solution (5 ml) of
C6F5Br (1.48 g, 6 mmol) at 0°C. The mixture was
stirred for 2 h. A THF solution (10 ml) of tribenzyltin
chloride (2.13 g, 5 mmol) was added dropwise at 0°C.
After being stirred at r.t. for 63 h, the mixture was
filtered on a celite pad and quickly passed through a
short silica gel column (hexane). The filtrate was evapo-
rated and the residue was purified by column chro-
matography on silica gel (hexane) to give 9 (2.70 g,
3.5. (C6F5)2Sncl2 (4) [4]
1
97%): m.p. 51–52°C; H-NMR: l 2.60 (s, 6H, JSn–H
=
67 Hz), 6.76–7.18 (m, l5 H); 119Sn-NMR l −63.2;
Into a dry CCl4 solution (30 ml) of (C6F5)2Sn(CH2
CHꢀCH2)2 (1.07 g, 2.0 mmol) was bubbled dry hydro-
gen chloride gas at r.t. for 1.5 h. After removal of the
solvent, the residual oil was purified by column chro-
matography (hexane followed by benzene) to give 4
(0.94 g, 90%): 119Sn-NMR l −88.9; MS (m/z): 526
(M+).
19F-NMR
l
−56.2, −87.3, −96.0; MS (m/z):
560(M+); Anal. calc. for C27H21F5Sn: C, 58.00; H,
3.79; Found C, 57.85, H, 3.71.
3.9. C6F5SnBr3 (5)
To a dry CCl4 solution (30 ml) of C6F5Sn(CH2C6H5)2
(1.51 g, 2.7 mmol) was added dropwise bromine (1.28 g,
8.1 mmol) at 0°C. The mixture was stirred at r.t. for 3
h and evaporated. The residue was purified by column
chromatography (hexane followed by benzene) to give 5
(0.98 g, 70%): 119Sn-NMR l −289.4; 19F-NMR l
−57.8, −81.4, −93.5; MS (m/z): 524 (M+); HRMS
calc. for C6Br3F5Sn 523.6494, found 523.6509.
A dry CCl4 solution (30 ml) of (C6F5)2Sn(CH2
CHꢀCH2)2 (2.11 g, 4.0 mmol) and ICl (1.41 g, 8.0
mmol) was heated under reflux for 4 h. After removal
of the solvent, the residual oil was purified by column
chromatography (hexane followed by benzene) to give 4
(1.50 g, 72%).
3.6. (C6F5)3Sncl (3) [5]
Into a refluxing CCl4 solution (50 ml) of (C6F5)3Sn
CH2CHꢀCH2 (4.54 g, 6.88 mmol) was bubbled dry
hydrogen chloride gas for 4 h. After removal of the
solvent, the crude product was recrystallized from
petroleum ether (b.p.B50°C) to give 3 (4.34 g, 96%):
m.p. 108–110°C, lit. m.p. 108–109°C; 119Sn-NMR l
−123.9; MS (m/z): 656 (M+).
3.10. (C6F5)2Sn(Cl)CH2C6H5 (10)
To a dry CCl4 solution (30 ml) of (C6F5)2Sn(CH2
C6H5)2 (1.0 g, 1.58 mmol) was added ICl (563 mg, 3.48
mmol) at r.t. The mixture was heated under reflux for 3
h and evaporated. The residue was purified by column
chromatography (hexane followed by benzene) to give
10 (0.73 g, 80%): 119Sn-NMR l −96.6; 19F-NMR l
−58.2, −80.2, −93.1; MS (m/z): 580 (M+); HRMS
calc. for C19H7ClF10Sn 579.9098, found 579.9099.
(C6F5)2Sn(CH2C6H5)2 (1.0 g, 1.58 mmol) and SOCl2
(1.63 g, 13.8 mmol) was mixed at 0°C. The mixture was
heated under reflux for 3 h and evaporated. The residue
was purified by column chromatography (hexane fol-
lowed by benzene) to give 10 (0.69 g, 76%).
To a dry CCl4 solution (30 ml) of (C6F5)2Sn(CH2
C6H5)2 (1.0 g, 1.58 mmol) was added SO2Cl2 (1.68 g,
12.5 mmol) at 0°C. The mixture was heated under
reflux for 6 h and evaporated. The resulting yellow oil
was purified by column chromatography (hexane fol-
lowed by benzene) to give 10 (0.76 g, 83%).
3.7. (C6F5)2Sn(CH2C6H5)2 (8)
To a suspension of Mg turnings (0.72 g, 30 mmol) in
dry ether (50 ml) was added an ether solution (15 ml) of
C6F5Br (6.15 g, 25 mmol) at 0°C. The mixture was
stirred for 2 h. A THF solution (15 ml) of dibenzyltin
dichloride (3.70 g, 10 mmol) was added dropwise at
0°C. After being stirred at r.t. for 38 h, the mixture was
filtered on a celite pad and quickly passed through a
short silica gel column (hexane). The filtrate was evapo-
rated and the residue was purified by column chro-
matography on silica gel (hexane) to give 8 (5.55 g,
1
88%): m.p. 67–68°C; H-NMR: l 3.06 (s, 4H, JSn–H
=

64
J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
3.11. (C6F5)2Sn(SCSNEt2)2 (11)
was stirred at r.t. for 3 h and subjected to column
chromatography on silica gel (hexane) to give 15 (178
mg, 82%): m.p. 98–99°C; 1H-NMR l 1.39 (t, 3H,
J=7.9 Hz), 2.03 (q, 2H, J=7.9 Hz, JSn–H=67 Hz);
119Sn-NMR l −136.3; MS (m/z): 650 (M+).
To an ether solution (5 ml) of (C6F5)3SnBr (209 mg,
0.3 mmol) was added a Grignard reagent in ether (5 ml)
(prepared from Mg (10.6 mg, 0.44 mmol) and EtBr
(43.6 mg, 0.4 mmol)) at 0°C. After being stirred at r.t.
for 7 h, the mixture was subjected to column chro-
matography on silica gel (hexane) to give 15 (175 mg,
81%).
To an acetonitrile solution (10 ml) of (C6F5)2SnBr2
(610 mg, 1 mmol) was added Et2NCSSAg (512 mg, 2
mmol) at r.t. The solution was stirred for 1 h and then
evaporated. Benzene was added and the mixture was
filtered to remove AgBr. The benzene was evaporated
and the crude product was recrystallized from
dichloromethane–hexane to give 11 (607 mg, 81%):
1H-NMR l 1.31 (t, 12 H, J=7.1 Hz), 3.71 (q, 8 H,
J=7.1 Hz); 119Sn-NMR l −540.2; 119F-NMR l −
64.2, −91.2, −97.5; MS (m/z): 750 (M+); Anal. calc.
for C22H20F10N2S4Sn: C, 35.26, H, 2.69. N; 3.74 found
C, 35.45, H, 2.64, N. 3.24.
3.16. (C6F5)2SnEt2 (16) [7]
3.12. (C6F5)3SnC6H5 (12) [5]
To a CH2Cl2 solution (3 ml) of (C6F5)2SnBr2 (245
mg, 0.4 mmol) was added Et2Zn (0.40 ml 1 M solution
in hexane, 0.40 mmol) −78 °C. The reaction mixture
was stirred for 0.5 h and was subjected to column
chromatography on silica gel (hexane) to give 16 (183
mg, 90%): 119Sn-NMR l −61.5; MS (m/z): 512 (M+).
To an ether solution (3 ml) of (C6F5)3SnBr (209 mg,
0.3 mmol) was added Grignard reagent C6H5MgBr
(prepared from Mg turnings (9.6 mg, 0.4 mmol) and
C6H5Br (57 mg, 0.36 mmol) in dry ether (3 ml)) at 0°C.
The reaction mixture was stirred for 8 h. Then, the
mixture was filtered on a celite pad and quickly passed
through a short silica gel column (hexane) to give 12
(192 mg, 83%): m.p. 95–96°C, lit. m.p. 95–96°C; 119Sn-
NMR l −186.9; MS (m/z): 698 (M+).
3.17. C6F5SnEt3 (17) [7]
To an ether solution (3 ml) of C6F5SnBr3 (200 mg,
0.38 mmol) was added Et2Zn (0.57 ml 1 M solution in
hexane, 0.57 mmol) at −78°C. The reaction mixture
was stirred for 10 min at −78°C and was subjected to
column chromatography on silica gel (hexane) to give
17 (114 mg, 80%): 119Sn-NMR l −6.8. MS (m/z): 374
(M+).
3.13. (C6F5)2Sn(C6H5)2 (13) [5]
To an ether solution (3 ml) of (C6F5)2SnBr2 (306 mg,
0.5 mmol) was added Grignard reagent C6H5MgBr
(prepared from Mg turnings (36 mg, 1.5 mmol) and
C6H5Br (220 mg, 1.4 mmol) in dry ether (3 ml)) at 0°C.
The reaction mixture was stirred for 4 h. Then, the
mixture was filtered on a celite pad and quickly passed
through a short silica gel column (hexane) to give 13
(295 mg, 97%): m.p. 84–85°C, lit. m.p. 85°C; 119Sn-
NMR l −158.2; MS (m/z): 608 (M+).
References
[1] M. Pereyre, J.-P. Quintard, A. Rahm, Tin in Organic Synthesis,
Butterworths, London, 1987.
[2] (a) J. Chen, K. Sakamoto, A. Orita, J. Otera, Synlett (1996) 877.
(b) J. Chen, J. Otera, Angew. Chem. Int. Ed. Engl. 37 (1998) 91.
(c) J. Chen, J. Otera, Tetrahedron Lett. 39 (1998) 1767.
[3] J.M. Holmes, R.D. Peacock, J.C. Tatlow, Proc. Chem. Soc.
(1963) 108.
[4] J.M. Holmes, R.D. Peacock, J.C. Tatlow, J. Chem. Soc. (A)
(1966) 150.
[5] R.D. Chambers, T. Chivers, J. Chem. Soc. (1964) 4782.
[6] C. Tamborski, E.J. Soloski, S.M. Dec, J. Organomet. Chem. 4
(1965) 446.
[7] M.N. Bochkarev, N.S. Vyazankin, L.P. Maiorova, G.A. Razu-
vaev, Zh. Obshch. Khim. 48 (1978) 2706.
[8] Y. Naruta, Y. Nishigaichi, K. Maruyama, Tetrahedron 45 (1989)
1067. Diallyltin dibromide can also be obtained from allyl bro-
mide and tin: K. Sisido, Y. Takeda, J. Org. Chem. 26 (1961)
2301.
3.14. C6F5Sn(C6H5)3 (14) [5]
To an ether solution (3 ml) of C6F5SnBr3 (209 mg,
0.4 mmol) was added Grignard reagent C6H5MgBr
(prepared from Mg turnings (43 mg, 1.8 mmol) and
C6H5Br (251 mg, 1.6 mmol) in dry ether (3 ml)) at 0°C.
The reaction mixture was stirred for 2 h. Then, the
mixture was filtered on a celite pad and quickly passed
through a short silica gel column (hexane) to give 14
(184 mg, 89%): m.p. 84–85°C, lit. m.p. 86°C; 119Sn-
NMR l −139.3; MS (m/z): 518 (M+).
[9] E. Nield, R. Stephens, J.C. Tatlow, J. Chem. Soc. (1959) 166.
[10] K. Sisido, Y. Takeda, Z. Kinugasa, J. Am. Chem. Soc. 83 (1961)
538.
[11] Dry CH2Cl2 as a solvent with the CDCl3 external lock was
employed for these measurements to avoid the influence of the
contamination of H2O.
3.15. (C6F5)3SnEt (15) [7]
To a CH2Cl2 solution (3 ml) of (C6F5)3SnBr (209 mg,
0.3 mmol) was added Et2Zn (0.15 ml 1 M solution in
hexane, 0.15 mmol) at −78°C. The reaction mixture

J.-x. Chen et al. / Journal of Organometallic Chemistry 574 (1999) 58–65
65
[12] It was reported that treatment of 1 with EtMgBr in boiling ether
furnished a mixture of (C6F5)3SnEt (14%) (C6F5)2SnEt2 (50%),
C6F5SnEt3 (85%) and (C6F5)4Sn (21%) [7]. However, we have
found that the reaction at 0°C–r.t. in ether provided the desired
compound, (C6F5)3SnEt, in a 81% yield.
[14] The tin–carbon bonds are usually converted to tin–chlorine
bonds by the use of HgCl2. The BiCl3 method offers a conve-
nient and non-toxic alternative way to arrive at tin chlorides.
The cleavage of tin–vinyl bond was reported: D. Seyferth,
Naturwissenschaften 44 (1957) 34.
[13] The analogous high kinetic stability in the reaction of
heptafluoropropyltin compounds with bromine was reported:
D. Seyferth, F. Richter, J. Organomet. Chem. 499 (1995)
131.
[15] J.R. Bourn, D.G. Gillies, E.W. Randall, Proc. Chem. Soc. (1963)
200.
[16] R.W. Taft, F. Prosser, L. Goodman, G.T. Davis, J. Chem. Phys.
38 (1963) 380.
.
.