Synthesis, characterisation and reactivity of 2-functionalised vinylstannanes

Article abstract of DOI:10.1016/S0022-328X(00)00887-1

The functionalised vinylstannanes of the type (E)/(Z)-Ph₃SnCR′=CHYR_n and (E)/(Z)-Ph₃SnC(YR_n)=CHR′ (YR_n=NMe₂, OEt, SMe, SEt; R′=Ph, Bu (n-butyl), Pe (n-pentyl), H) were prepared by non-catal

Full text of DOI:10.1016/S0022-328X(00)00887-1

Journal of Organometallic Chemistry 625 (2001) 86–94
www.elsevier.nl/locate/jorganchem
Synthesis, characterisation and reactivity of 2-functionalised
vinylstannanes
T. Le´bl a,*, J. Holecˇek a, M. Dyma´k a, D. Steinborn b
a
&
Department of General and Inorganic Chemistry, Uni6ersity of Pardubice, Cs. Legi´ı, 565, 532 10 Pardubice, Czech Republic
b Department of Inorganic Chemistry, Martin-Luther-Uni6ersita¨t Halle-Wittenberg, Kurt-Mothes-Straße 2, 06120 Halle (Saale), Germany
Received 10 August 2000; received in revised form 18 October 2000; accepted 8 November 2000
Abstract
The functionalised vinylstannanes of the type (E)/(Z)-Ph3SnCR%ꢀCHYRn and (E)/(Z)-Ph3SnC(YRn)ꢀCHR% (YRn=NMe2,
OEt, SMe, SEt; R%=Ph, Bu (n-butyl), Pe (n-pentyl), H) were prepared by non-catalysed or Pd-catalysed hydrostannylation
reactions. Particular stereoisomers were isolated by means of preparative HPLC and fully characterised using 1H-, 13C- and
119Sn-NMR spectroscopy. The reactions of 2-functionalised vinylstannanes (E)/(Z)-Ph3SnCR%ꢀCHYRn with acetic and
chloroacetic acid in CDCl3 proceeded by protodestannylation yielding Ph3SnOOCCH2X (X=H, Cl) and CHR%ꢀCHYRn. The
results of kinetics measurements reveal that Lewis-basic substituents YRn facilitate the electrophilic cleavage of SnꢁCꢀ bonds, and
this effect increases with the basicity of the heteroatom Y, i.e. in the order SBOBN. In contrast, an alkyl substituent at the
a-carbon atom slightly suppresses the reaction rate. Furthermore it was found that the E-isomers react faster than the
corresponding Z-isomers. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Functionalised vinylstannanes; Hydrostannylation; Protodestannylation; NMR; Kinetics
erolytic fragmentation at this type of compound are
quite rare and partially ambiguous.
1. Introduction
This work therefore deals with the preparation, char-
acterisation and reactivity of 2-functionalised vinylstan-
nanes of the type Ph3SnCR%ꢀCHYRn (YRn=NMe2,
OEt, SMe, SEt; R%=Ph, Bu (n-butyl), Pe (n-pentyl),
Organometallics containing not only MꢁC bonds as
reactive sites but also other centres of high reactivity
represent a very interesting field of organometallic
chemistry. Introduction of a heteroatom Y (Y Group
14–17 element) into an organoligand can have a pro-
H). The aim is to elucidate relationships between the
type of the Lewis-basic substituent and stereoisomerism
found influence on the structure, stability and reactivity
on the one hand and reactivity on the other hand.
of organometallic compounds and consequently open
the possibility of entirely new reactions [1].
For example, organometallic compounds with Lewis-
basic 2-functionalised ethyl ligands LxMꢁCH2ꢁ
CH2ꢁYRn (YRn=NR2, OR, Cl,...; R=alkyl, aryl, H)
can undergo elimination reaction, so-called heterolytic
fragmentation [2], either spontaneously (M=Li or Mg)
[3] or after reaction with a suitable electrophile (Scheme
1) [4]. However, there are only a few reports on
analogous 2-functionalised vinylmetallic compounds
LxMꢁCHꢀCHꢁYRn, and the observations of het-
2. Results and discussion
2.1. Synthesis
The functionalised vinyltin compounds were pre-
pared by either non-catalysed or Pd-catalysed hy-
drostannylation of functionalised alkynes 1–5 with
triphenyltin hydride which proceeds according to
Scheme 2. Selectivities of particular reactions deter-
mined by means of 1H- and/or 119Sn-NMR spec-
troscopy of crude reaction mixtures are summarised in
Tables 1 and 2.
* Corresponding author. Tel.: +42-40-6037169; fax: +42-40-
6037068.
E-mail address: tomas.lebl@upce.cz (T. Le´bl).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00887-1

T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
87
Scheme 1.
Table 2
Selectivity of Pd-catalysed hydrostannylation
Entry
Alkyne
Selectivity (%)
R%
YRn
b-E (a)
a-E (c)
Scheme 2.
1
2
3
4
2
3
4
5
H
Bu
H
OEt
OEt
SEt
70
46
0
30
54
100
100
Pe
SMe
0
Non-catalysed hydrostannylations were carried out
in hexane at elevated temperature (50–55°C). No radi-
cal initiator was used because a slightly elevated tem-
perature is sufficient to induce homolytic cleavage of
the SnꢁH bond and initiation of the radical reaction.
The Pd-catalysed hydrostannylation ([Pd(PPh3)4]) was
performed in THF at −30°C in order to suppress
radical reaction of Ph3SnH. In all cases, non-catalysed
hydrostannylation as well as Pd-catalysed hydrostanny-
lation provided vinyltin compounds in yields of about
90% or higher along with a negligibly small amount of
hexaphenyldistannane and other minor side products.
Non-catalysed hydrostannylations afforded the de-
sired b-Z-isomers with quite high stereo- and regiose-
lectivity. There is an exception for HCꢂCSEt (4) (Table
1, entry 4) which could be caused either by a higher rate
of isomerisation or by a small excess of organotin
hydride arising due to lability of the alkyne [5]. Fur-
thermore, slightly lower regioselectivity was observed in
the case of BuCꢂCOEt (3) (Table 1, entry 3) where
about 20% of a-isomers were formed. For the non-
catalysed reaction of triphenyltinhydride with
PeCꢂCSMe (5) (Table 1, entry 5) selectivity could not
be determined exactly because it was impossible to
identify unambiguously minor products.
provided the a-E-isomers 4c and 5c (Table 2, entries 3
and 4) selectively, as was already shown for R%/
YRnꢀPh/SMe [7]. On the other hand, Pd-catalysed
hydrostannylation of alkoxyalkynes 2 and 3 (Table 2,
entries 1 and 2) afforded the desired b-E-isomers 2a
and 3a but with low regioselectivity.
Except for (E)-Ph3SnCHꢀCHSEt (4a), standard
work-up procedures did not give b-functionalised vinyl-
stannanes in the isomerically pure state. Therefore, the
desired stereoisomers (E)- and (Z)-Ph3SnCHꢀCHOEt
(2a/2b), (E)- and (Z)-Ph3SnC(Bu)ꢀCHOEt (3a/3b), (Z)-
Ph3SnCHꢀCHSEt (4b) were isolated from crude reac-
tion mixtures by means of preparative HPLC using
direct phase (silicagel, hexane:THF=100:6). For (Z)-
Ph3SnC(Ph)ꢀCHNMe2 (1b) [7] and (Z)-Ph3Sn-
C(Pe)ꢀCHSMe (5b) the selectivity of hydrostannylation
was relatively high, and these compounds were used
without further purification.
2.2. Characterisation
Except for (Z)-Ph3SnC(Ph)ꢀCHNMe2 (1b) [7], 1H-
NMR parameters of vinylic protons, summarised in
Table 3, enable one to distinguish between particular
isomers and to identify them unambiguously even in
Pd-catalysed hydrostannylation, being a stereoselec-
tive cis-addition, was used for preparation of E-isomers
[6]. However, the reactions of thioalkynes 4 and 5
Table 1
Selectivity of non-catalysed hydrostannylation
Entry
Alkyne
Selectivity (%)
R%
YRn
b-E (a)
b-Z (b)
a-E (c)
a-Z (d)
1
2
3
4
5
1 a
2
3
4
5
Ph
H
Bu
H
NMe2
OEt
OEt
SEt
0
12
0
100
88
80
19
]92
0
0
3
0
17
81
0
b
b
b
Pe
SMe
a Ref. [7].
b Not unambiguously spectroscopically proved.

88
T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
complex mixtures. The data of 1b are given in Ref. [7].
The values of 1H chemical shifts lie in a very wide
region (l1H 4.2–7.4) and they are strongly dependent
on the heteroatom Y, and on the configuration of
substituents on the vinylic group.
parameter predicts the mutual positions of the tin and
the hydrogen atom at the CꢀC bond (see above). The
3
magnitude of J(119Sn,1H) in the range of 30–70 Hz
indicates the mutual cis positions of the Ph3Sn sub-
stituent and vinylic proton (E-isomers), and in the
range of 120–160 Hz the mutual trans positions (Z-iso-
mers). Constitutional isomers can be distinguished us-
ing the spectral pattern of the vinylic proton. In the
case of a-isomers, the signal of the vinylic proton
reveals coupling with protons on the a-carbon atom of
alkyl substituent R%. The appropriate coupling con-
For functionalised vinylstannanes with two vinylic
protons (R%=H) there are three possible isomers (b-Z,
b-E and a). The b-isomers have vinylic protons in
vicinal positions. In the case of the b-E isomers 2a and
4a, the vinylic protons are mutually in trans-positions
and the corresponding coupling constants 3J(1H,1H) are
15.6 and 18.4 Hz, respectively. On the contrary, in the
case of b-Z isomers 2b and 4b, the vinylic protons are
in mutual cis-positions and the 3J(1H,1H) coupling
constants are roughly two times smaller (6.8 Hz 2b,
11.3 Hz 4b). The a-isomers 2c and 4c have vinylic
protons in geminal position, and thus the coupling
3
stants J(1H,1H) are within the range 6.8–7.6 Hz. On
the other hand, vinylic protons of b-isomers give rise to
1
singlet signals in H-NMR spectra. In particular cases
of well resolved spectra, triplets can be observed but the
4
corresponding coupling constant J(1H,1H) is less than
1 Hz.
2
constants J(1H,1H) are usually less than 2 Hz [8]. The
In the case of (Z)-Ph3SnC(Ph)ꢀCHNMe2 (1b), it was
impossible to distinguish between a- and b-isomers by
means of conventional 1H-NMR experiment because
the signal of the vinylic proton is singlet in both cases.
Therefore, 1b was fully identified by means of
1J(13C,13C) obtained using the 1D INADEQUATE
technique [7].
assignment of both vinylic proton resonances was done
on the basis of the relationship between relevant
J(119Sn,1H) coupling constants. The coupling constants
2J(119Sn,1Hgem) are slightly larger than 3J(119Sn,1Hcis)
3
while J(119Sn,1Htrans) are about two times larger than
3J(119Sn,1Hcis) [9]. In the cases of b-E-isomers, the
2
values of both coupling constants J(119Sn,1Hgem) and
3J(119Sn,1Hcis) are very similar. The assignment was
confirmed by the evaluation of 1H chemical shifts:
resonances of protons in vicinal position (SnCHꢀCH)
are shifted significantly downfield with respect to the
resonances of protons in geminal position (SnCHꢀCH).
Functionalised vinylstannanes with one vinylic pro-
ton (R%=alkyl) form four isomers (b-E, b-Z, a-E and
2.3. Reactions of 2-functionalised 6inylstannanes with
acids
2-Functionalised
vinylstannanes
(E)/(Z)-
Ph3SnC(R%)ꢀCHYRn (R%/YRnꢀPh/NMe2 1b, H/OEt 2a/
2b, Bu/OEt 3a/3b, H/SEt 4a/4b and Pe/SMe 5b) were
treated with about two equivalents of acetic acid in
CDCl3 at room temperature. In all cases,
protodestannylation reactions took place and vinylic
3
a-Z). The J(119Sn,1H) coupling constants enable one
to distinguish between stereoisomers because this
Table 3
1H chemical shifts in ppm and relevant coupling constants in Hz of vinylic protons of functionalised vinylstannanes
Compound
2a
2b
2c
3a
3b
3c
3d
4a
4b
4c
5b
5c
l(1Hgem
)
4.92
52.0
6.43
42.8
4.88
62.2
6.21
75.0
6.67
75.1
6.38
73.9
J(119Sn,1Hgem
l(1Hcis
3J(119Sn,1Hcis
)
)
4.27
41.6
4.87
130.3
1.5
5.93
42.0
4.90
34.5
5.40
71.7
5.69
5.88
67.5
)
l(1Htrans
)
6.94
127.7
6.8
6.68
122.7
5.50
126.9
7.6
7.34
167.7
11.3
d
6.78
3J(119Sn,1Htrans
)
148.6
151.3
J(1H,1H)
15.6
d
7.0
t
18.4
d
6.8
t
a
Multiplicities
d
d
s
s
t
d
s
a Not resolved.
Scheme 3.

T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
89
Scheme 4.
Fig. 1. Verification of second-order kinetics derived from the decrease in the organotin substrate 2a (") and increase in product CH2ꢀCHOEt (×)
for the reaction of 2a with acetic acid in CDCl3.
substituents were cleaved selectively (Scheme 3a). No
evidence of heterolytic fragmentation (Scheme 3b) or
other side reactions was obtained.
(Z)-Ph3SnC(Ph)ꢀCHNMe2 (1b) reacted with acetic
acid very readily, and the selective cleavage of the
2-aminofunctionalised vinyl group (Scheme 3a) was
complete within 5 min. Moreover, it was found that 1b
is even moisture sensitive because water as weak acid
cleaves the tin–vinyl bond affording Ph3SnOH and
(E)-2-(N,N-dimethylamino)phenylethene.
On the other hand, for (Z)-Ph3SnC(Pe)ꢀCHSMe (5b)
a very slow reaction was observed. Therefore stronger
chloroacetic acid was used instead of acetic acid. Then
protodestannylation was significantly faster and about
50% of organotin substrate 5b was converted within 20
h. However, this reaction afforded likewise about 30%
of Ph2Sn(OOCCH2Cl)2 and benzene which denoted
that the phenyl group was also cleaved off. Further-
more less then 5% of 1-heptyne was formed. Thus, it
might be supposed that the heterolytic fragmentation
proceeded as a minor side reaction. However, the third
product of prospective heterolytic fragmentation, i.e.
methyl mercaptane, was not found in the reaction
mixture. Moreover, since 5b was used as a raw product
of hydrostannylation with purity of 92% the source of
alkyne might be an impurity.
conditions was found to be rather slow and complex.
After 2 days about 30% of starting triphenylvinylstan-
nane remained unreacted. Furthermore it was proved
that the reaction mixture contained a significant
amount of benzene indicating that phenyl groups were
cleaved. The 119Sn-NMR spectrum showed that the
reaction provided four organotin compounds
(l(119Sn)= −279.1 ppm/18%, −284.3 ppm/49%,
−290.9 ppm/28%, −390.5 ppm/5%). Thus, it seems
that phenyl and vinyl groups were cleaved simulta-
neously.
For the remaining six analogous 2-functionalised
vinylstannanes
(E)/(Z)-Ph3SnC(R%)ꢀCHYRn
(R%/
YRn=H/OEt 2a/2b, Bu/OEt 3a/3b, H/SEt 4a/4b) reac-
tion rates of prodestannylation (Scheme 3a) were
between those two limits mentioned above. Thus, it was
1
possible to follow the courses of reactions by H-NMR
spectroscopy and evaluate kinetics. In all cases, the rate
of disappearance of the organotin substrate was found
to be strictly second-order, in accordance with the
suggested mechanism (Scheme 4) which is consistent
with the general mechanism of electrophilic cleavage of
the metal–vinyl bond [10]. However, the rates of
product formation revealed considerable deviations
from second-order kinetics as shown in Fig. 1 with 2a
as example.
For comparison, the reactions of Ph3SnCHꢀCH2 (6)
with acids were also investigated. When 6 was treated
with acetic acid (molar ratio 1:2) in CDCl3 at room
temperature no reaction was observed within one
month. The reaction of Ph3SnCHꢀCH2 with
chloroacetic acid (molar ratio 1:5) under the same
Separate 1H-NMR spectroscopic investigations
showed that the primary products of protodestannyla-
tion CHR%ꢀCHYRn (Scheme 3a) can undergo subse-
quent reactions. Namely, ethyl vinyl ether (formed in
the reaction of 2a/2b with AcOH) reacts with acetic
acid under the same reaction conditions yielding 1-

90
T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
Scheme 5.
Scheme 7.
the differences in reactivity of stereoisomers are
evident. E-isomers 2a and 4a react roughly ten times
faster than the corresponding Z-isomers 2b and 4b,
respectively. The compounds 3a and 3b containing a
butyl substituent at the a-carbon atom reveal even
greater diversity in the reaction rate: the E-isomer
3a reacts more than fifty times faster than the
Z-isomer 3b.
Scheme 6.
ethoxyethyl acetate (Scheme 5). Furthermore it was
found that (E)-1-ethoxyhex-1-ene (formed in the reac-
tion of 3b with AcOH) most likely undergoes acid
catalysed E/Z-isomerisation under the reaction condi-
tions (Scheme 6). Probably, these slow subsequent reac-
tions cause the deviations from second-order kinetics
observed for product formations. In order to simplify
evaluation of the kinetics, the subsequent reactions
were neglected and the second-order rate constants
were derived only from the decay of starting vinylstan-
nanes which were practically unaffected because acetic
acid was used in sufficient excess.
3. a-Substituent. The comparison of 2a, 2b and 4b on
the one hand and 3a, 3b and 5b, respectively, on the
other hand shows that compounds with a butyl
substituent at the a-carbon atom react slower than
compounds without this substituent. The effect of
the butyl substituent seems to be significantly
stronger in the case of Z-isomers (2b and 3b) which
differ in reaction rate approximately eighteen times,
while E-isomers (2a and 3a) differ in reaction rate
only about three times.
The values of second-order rate constants for partic-
ular 2-functionalised vinylstannanes summarised in
Table 4 indicate three general effects.
2.4. Discussion
1. Lewis-basicity of substituent YRn. It seems obvious
from mutual comparison of 2-functionalised vinyl-
stannanes Ph3SnCR%ꢀCHYRn (1b–5b) with the cor-
In the accepted mechanism of protodestannylation of
vinylstannanes (Scheme 4) the electrophile attacks the
a-carbon atom yielding a carbocationic intermediate
stabilised by hyperconjugation. Then the rapid attack
of the nucleophile at the tin atom and subsequent
splitting of the tin–carbon bond finishes the reaction
[10]. Considering this mechanism the electronic influ-
ence of Lewis-basic substituents YRn on the b-vinylic
carbon atom can be discussed in the following way.
1. The interaction of the Lewis-basic substituent YRn
with the vinylic p bond results in an increase of
responding
non-functionalised
triphenylvinyl-
stannane Ph3SnCHꢀCH2 (6) that Lewis-basic sub-
stituents in b-position with respect to the tin atom
facilitate electrophilic cleavage of the vinyl group.
Moreover, a comparison of 2-thio-, 2-alkoxy- and
2-aminovinylstannanes reveals that the effect of
Lewis-basic heteroatom increases with its basicity,
i.e. in the sequence SBOBN.
2. Stereochemistry (E- versus Z-isomers). In all cases,
Table 4
Second-order rate constants of protodestannylation reactions, NBO charges and 13C chemical shifts of the a-carbon atom of 2-functionaliased
vinylstannanes
R%
YRn
Isomer
k (l mol−1 min−1
)
l(13Ca) (ppm)
NBO charges a
Ca
Cb
Y
b
b
b
1b
2a
2b
3a
3b
4a
4b
5b
6
Ph
H
H
Bu
Bu
H
H
Pe
H
NMe2
OEt
OEt
OEt
OEt
SEt
SEt
SMe
H
Z
E
Z
E
Z
E
Z
Z
\1 a
113.53
88.97
94.92
112.73
114.79
117.61
126.19
148.47
134.92
4.10×10−1
4.39×10−2
1.27×10−1
2.35×10−3
6.54×10−3
6.29×10−4
B10−4 a
−0.59
−0.58
−0.53
−0.53
−0.47
+0.10
+0.10
+0.07
+0.08
−0.16
−0.20
−0.22
−0.22
−0.19
+0.05
−0.47
−0.16
+0.03
b
b
b
ꢀ10−5 a
−0.49
−0.06
a Estimated.
b Not calculated.

T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
91
in comparison with electrophilic attack at the Lewis-ba-
sic heteroatom Y with subsequent heterolytic fragmen-
tation reaction. Furthermore it was found that the
substituents YRn facilitate the rate of protodestannyla-
tion. The overall effect depends on the nature of the
heteroatomic centre YRn and its stereo-orientation with
respect to the tin atom (E- versus Z-isomers).
negative charges at the a-vinylic C atom (Scheme 7)
which facilitates the rate-determining step of
protodestannylation (Scheme 4). Regarding the elec-
tronegativity of the heteroatom Y and the prefer-
ence for p conjugation for first-row elements over
second-row elements, the expected order is SBOB
N. For 2-ethoxy and 2-thiofunctionalised vinylstan-
nanes it is fully in agreement with the values of rate
constants, NBO charges [11] and 13C chemical shifts
of a-carbon functionalised vinylstannane atoms
listed in Table 4.
3. Experimental
3.1. General
2. The carbocationic intermediate (Scheme 4) is
strongly stabilised by a Lewis-basic substituent YRn
through a p-type interaction (Scheme 8). The ex-
pected order is OBSꢀN [12]. Thus, this seems to
be the reason for the significantly faster reaction of
2-aminofunctionalised vinylstannane 1b with acids
in comparison with ethoxy- and thio-functionalised
derivatives. Analogously, the stability of the non-
functionalised triphenylvinylstannane 6 under the
same reaction conditions in spite of the relatively
low charge on the a-carbon atom can be
understood.
3.1.1. Instruments
Microanalyses (C, H, S) were carried out using a
Fison EA 1108 instrument in the Microanalytical Labo-
ratory at the University of Pardubice. 1H-, 13C- and
119Sn-NMR spectra were recorded using a 5 mm tune-
able probe on a Bruker AMX 360 spectrometer in
CDCl3 at 300 K. Chemical shifts are given in parts per
1
million with respect to Me4Si [l H (HMDS)=0.05; l
13C (CDCl3)=77.00] and Me4Sn [l 119Sn=0.0 for J
(
119Sn)=37.2906174 MHz] [14]. Preparative HPLC was
performed on a Septech Merck apparatus equipped
with UV detector (254 nm) using direct phase system–
mobile phase n-hexane–THF (100:6); stationary phase
Lichrosorb Silicagel 60 (7 mm); column length 25 cm;
column diameter 2.5 cm. Gas samples were analysed
using a Chrompack CP 9000 instrument equipped with
capillary column (plot fused silica, Al2O3/KCl, length
50 m) and FID detector. Peaks were identified by
means of reference substances.
3. The higher reactivity of E-isomers over Z-isomers
might be a consequence of intramolecular nucle-
ophilic assistance Y“Sn, which can suppress the
cleavage of the vinyl group in Z-isomers. An
analogous
phenomenon
was
found
for
halodestannylations of some vinylstannanes, which
form five- or four-membered rings involving weak
Y“Sn interaction [13]. This hypothesis is sup-
ported by the fact that an upfield shift of l(119Sn)
by about 18 ppm is observed for Z-isomers with
respect to E-isomers in all three pairs of 2-function-
alised vinylstannanes 2a/2b, 3a/3b and 4a/4b. How-
ever, this result is not conclusive because 119Sn
resonances are usually shifted by more than 60 ppm
to upper field if an additional Y“Sn coordination
exists [9].
3.1.2. Preparati6e techniques and starting materials
The reactions were carried out under argon using
standard Schlenk techniques [15]. Hexane was dried
with LiAlH4. THF was distilled from sodium ben-
zophenone ketyl. 1-Heptyne, dimethyldisulfide, n-butyl-
lithium and ethoxyethyne
2
were commercially
available. Except for 2, which was distilled in vacuo at
room temperature prior to use, all starting compounds
were used without further purification. Tetrakis(tri-
phenylphosphine)palladium(0) [16], triphenyltin hydride
[17], N,N-dimethylaminophenylethyne (1) [18], 1-
ethoxyhex-1-yne (3) [19], ethylthioethyne (4) [20],
triphenylvinylstannane (6) [21] were prepared in accor-
dance with procedures described in the literature.
4. The experimental findings that alkyl substituents on
the a-vinylic C atom give rise to a slight decrease of
reaction rate (cf. 3a/2a, 3b/2b, 5b/4b) can be ex-
plained in terms of steric demand of these
substituents.
Summarising, this paper shows that for 2-function-
alised vinylstannanes an electrophile preferably attacks
the a-carbon atom resulting in the cleavage of SnꢁCꢀ
bonds (protodestannylation). Under normal circum-
stances this seems to be the preferred reaction pathway
3.1.3. Synthesis of 1-(methylthio)hept-1-yne (5)
A solution of n-BuLi in hexane (1.55 m, 50 ml) was
added dropwise to hept-1-yne (7.3 g, 76 mmol) in THF
(200 ml) at −78°C. After 10 min dimethyldisulfide (7.2
g, 76 mmol) in THF (15 ml) was added and the
reaction mixture was stirred at −78°C for 10 min and
for a further 45 min at room temperature. The precipi-
tation of LiSMe was filtered off and CH2Cl2 (50 ml)
Scheme 8.

92
T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
and sodium chloride solution (10%, 100 ml) was added.
The organic layer was separated, washed with KOH
(5%, 100 ml) and sodium chloride solutions (10%, 100
ml) and dried over Na2SO4. After solvent evaporation
under reduced pressure, the residue was distilled at 4
Torr and 5 (4.4 g, yield 41%, purity 99%) was obtained
as the fraction boiling at 62–63°C.
3.2.3.3. Method c. The solvent was removed in vacuo.
The residue was purified by rapid column chromatogra-
phy on silicagel, eluting with hexane.
3.2.4. Characterisation of functionalised 6inylstannanes
3.2.4.1. (E)-1-Ethoxy-2-triphenylstannylethene (2a)
1H-NMR: l=2.33 (3H, s, SCH3), 2.26 (2H, t,
CꢂCCH2), 1.40–1.59 (2H, m, CH2(CH2)3CH3), 1.21–
1.4 (4H, m, CH2(CH2)3CH3), 0.88 (3H, t,
CH2(CH2)3CH3). 13C-NMR: l=93.23 (CꢂCS), 69.74
(CꢂCS), 30.96/28.40/22.12/19.12 ((CH2)4CH3), 19.96
(SCH3), 13.88 ((CH2)4CH3).
Work-up procedure a. Purity 100% (1H-NMR). H-
1
NMR: l=7.25–7.74 (15H, m, C6H5), 6.43 (1H, d,
3JH,H=15.6 Hz, 3JSn,H=42.8 Hz, SnCHꢀCH), 4.92
3
2
(1H, d, JH,H=15.6 Hz, JSn,H=52.0 Hz, SnCHꢀCH),
3.83 (2H, q, OCH2CH3), 1.25 (3H, t, OCH2CH3). 13C-
NMR: l=158.00 (2JSn,C=64.8 Hz, SnCHꢀC), 138.41
(1JSn,C=545.0 Hz, i-C), 136.92 (2JSn,C=37.7 Hz, o-
CH), 128.96 (4JSn,C=13.0 Hz, p-CH), 128.49 (3JSn,C
=
3.2. Syntheses of functionalised 6inylstannanes
52.3 Hz, m-CH), 88.97 (1JSn,C=540.0 Hz, SnCHꢀC),
63.18 (OCH2CH3), 14.53 (OCH2CH3). 119Sn-NMR:
l= −116.3.
3.2.1. Non-catalysed hydrostannylation (general
procedure)
A mixture of triphenyltin hydride (7.0 g, 20 mmol)
and the requisite functionalised acetylene 1–5 (22
mmol) in hexane (20 ml) was stirred at 50–55°C for
6–8 h. Then the reaction mixture was worked up as
described below.
3.2.4.2. (Z)-1-Ethoxy-2-triphenylstannylethene (2b)
1
Work-up procedure a. Purity 100% (1H-NMR). H-
NMR: l=7.25–7.74 (15H, m, C6H5), 6.94 (1H, d,
3JH,H=6.8 Hz, 3JSn,H=127.7 Hz, SnCHꢀCH), 4.88
3
2
(1H, d, JH,H=6.8 Hz, JSn,H=62.2 Hz, SnCHꢀCH),
3.68 (2H, q, OCH2CH3), 0.97 (3H, t, OCH2CH3). 13C-
NMR: l=159.07 (2JSn,C=25.5 Hz, SnCHꢀC), 139.68
(1JSn,C=545.0 Hz, i-C), 137.10 (2JSn,C=38.7 Hz, o-
3.2.2. Pd-catalysed hydrostannylation (general
procedure)
Triphenyltin hydride (7.4 g, 21 mmol) in THF (15
ml) was added dropwise to a solution of 1–5 (21 mmol)
and [Pd(PPh3)4] (240 mg, 0.21 mmol) in THF (15 ml) at
−30°C in the dark. After 30 min, the dark brown
reaction mixture was worked up as described below.
CH), 128.70 (4JSn,C=11.2 Hz, p-CH), 128.34 (3JSn,C
=
52.2 Hz, m-CH), 94.92 (1JSn,C=510.8 Hz, SnCHꢀC),
67.41 (OCH2CH3), 15.18 (OCH2CH3). 119Sn-NMR:
l= −135.2.
3.2.4.3. 1-Ethoxy-1-triphenylstannylethene (2c)
Work-up procedure a. Purity 98% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 4.87 (1H, d,
3.2.3. Work-up procedures
3
2JH,H=1.5 Hz, JSn,H=130.3 Hz, trans-SnCꢀCH), 4.27
3.2.3.1. Method a. The solvent was removed in vacuo.
The residue was purified by means of preparative
HPLC. 5–10 HPLC runs result in about 100 mg of
isomerically pure substance starting from 300–500 mg
of crude mixture. Fractions were collected in manual
mode. When mobile phase was removed in vacuo chlo-
roform (2×50 ml) was added and evaporated in vacuo
to remove residual mobile phase. The residue was di-
luted in CDCl3 (0.5 ml) and the solution was trans-
ferred to the NMR tube. After characterisation by
means of NMR spectroscopy the kinetics measurement
was performed (see Section 3.3).
2
3
(1H, d, JH,H=1.5 Hz, JSn,H=41.6 Hz, cis-SnCꢀCH),
3.90 (2H, q, OCH2CH3), 1.37 (3H, t, OCH2CH3). 13C-
NMR: l=169.67 (1JSn,C=661.0 Hz, SnCꢀCH2),
137.98 (1JSn,C=540.3 Hz, i-C), 137.10 (2JSn,C=37.7
Hz, o-CH), 129.11 (4JSn,C=11.4 Hz, p-CH), 128.49
(3JSn,C=46.2 Hz, m-CH), 98.67 (2JSn,C=89.7 Hz,
SnCꢀCH2), 62.89 (OCH2CH3), 14.48 (OCH2CH3).
119Sn-NMR: l= −161.6.
3.2.4.4. (E)-1-Ethoxy-2-triphenylstannylhex-1-ene (3a)
1
Work-up procedure a. Purity 100% (1H-NMR). H-
NMR: l=7.25–7.74 (15H, m, C6H5), 5.93 (1H, s,
3JSn,H=42.0 Hz, SnCꢀCH), 3.77 (2H, q, OCH2CH3),
3
3.2.3.2. Method b. At room temperature the crystals of
4a were filtered off and recrystallised from hexane (4.5
g, yield 51%, m.p. 86–90°C). The solvent was removed
from mother liquor in vacuo. The obtained colourless
oil (4.2 g, yield 46%) consisting of 4a and 4b (3:4) was
further purified by means of preparative HPLC in order
to obtain pure 4b (see above, method a).
2.39 (2H, m, JSn,H=69.2 Hz, SnCCH2CH2), 1.17–1.34
(4H, m, CH2(CH2)2CH3), 1.21 (3H, t, OCH2CH3), 0.71
(3H, t, CH2CH2CH3). 13C-NMR: l=151.95 (2JSn,C
=
100.6 Hz, SnCꢀC), 138.99 (1JSn,C=520.0 Hz, i-C),
137.11 (2JSn,C=36.8 Hz, o-CH), 128.92 (3JSn,C=49.4
Hz, m-CH), 128.79 (4JSn,C=11.0 Hz, p-CH), 112.73
(1JSn,C=553.5 Hz, SnCꢀC), 67.45 (OCH2CH3), 32.68

T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
93
(3JSn,C=12.2 Hz, SnCCH2CH2), 28.49 (2JSn,C=26.8
Hz, SnCCH2CH2), 22.39 (CH2CH2CH3), 15.38
(OCH2CH3), 13.70 (CH2CH2CH3). 119Sn-NMR: l=
−112.5.
−130.5. Microanalysis: Found (Calc.): C: 60.88
(60.44); H: 5.08 (5.07); S: 7.25 (7.33).
3.2.4.9. (Z)-1-Ethylthio-2-triphenylstannylethene (4b)
Work-up procedure b and a. Purity 100% (1H-NMR).
1H-NMR: l=7.25–7.74 (15H, m, C6H5), 7.32 (1H, d,
3JH,H=11.3 Hz, 3JSn,H=167.7 Hz, SnCHꢀCH), 6.38
(1H, d, 3JH,H=11.3 Hz, 2J(119Sn,1H)=73.9 Hz,
SnCHꢀCH), 2.61 (2H, q, SCH2CH3), 1.16 (3H, t,
SCH2CH3). 13C-NMR: l=146.80 (2JSn,C=9.2 Hz,
SnCHꢀC), 138.85 (1JSn,C=542.3 Hz, i-C), 137.08
(2JSn,C=38.0 Hz, o-CH), 128.82 (4JSn,C=11.2 Hz, p-
3.2.4.5. (Z)-1-Ethoxy-2-triphenylstannylhex-1-ene (3b)
Work-up procedure a. Purity 93% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 6.68 (1H, s,
3JSn,H=122.7 Hz, SnCꢀCH), 3.61 (2H, q, OCH2CH3),
3
2.17 (2H, m, JSn,H=67.5 Hz, SnCCH2CH2), 1.08–1.32
(4H, m, CH2(CH2)2CH3), 0.89 (3H, t, OCH2CH3), 0.68
(3H, t, CH2CH2CH3). 13C-NMR: l=152.15 (2JSn,C
=
4.5 Hz, SnCꢀC), 139.97 (1JSn,C=523.8 Hz, i-C), 137.17
CH), 128.39 (3JSn,C=52.3 Hz, m-CH), 126.19 (1JSn,C
=
(2JSn,C=37.1 Hz, o-CH), 128.41 (4JSn,C=11.2 Hz, p-
509.1 Hz, SnCHꢀC), 28.11 (SCH2CH3), 15.40
CH), 128.13 (3JSn,C=50.2 Hz, m-CH), 114.79 (1JSn,C
=
(SCH2CH3). 119Sn-NMR: l= −149.2.
508.3 Hz, SnCꢀC), 66.92 (OCH2CH3), 33.72
(3JSn,C=13.1 Hz, SnCCH2CH2), 31.87 (2JSn,C=31.2
Hz, SnCCH2CH2), 22.03 (CH2CH2CH3), 14.85
(OCH2CH3), 13.65 (CH2CH2CH3). 119Sn-NMR: l=
−130.4.
3.2.4.10. 1-Ethylthio-1-triphenylstannylethene (4c)
Work-up procedure c. Purity 89% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 5.69 (1H, s,
3JSn,H=148.6 Hz, trans-SnCꢀCH), 5.40 (1H, s,
3JSn,H=71.7 Hz, cis-SnCꢀCH), 2.73 (2H, q,
SCH2CH3), 1.18 (3H, t, SCH2CH3). 13C-NMR: l=
3.2.4.6. (E)-1-Ethoxy-1-triphenylstannylhex-1-ene (3c)
Work-up procedure a. Purity 95% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 4.90 (1H, t,
143.79 (1JSn,C=463.5 Hz, SnCꢀCH2), 137.24 (1JSn,C
=
542.3 Hz, i-C), 136.98 (2JSn,C=38.1 Hz, o-CH), 129.15
(4JSn,C=11.4 Hz, p-CH), 128.52 (3JSn,C=52.5 Hz, m-
CH), 118.47 (2JSn,C=21.6 Hz, SnCꢀCH2), 25.08
(3JSn,C=25.0 Hz, SCH2CH3), 12.81 (SCH2CH3). 119Sn-
NMR: l= −135.6.
3
3JH,H=7.0 Hz, JSn,H=34.5 Hz, SnCꢀCH), 3.72 (2H,
q, OCH2CH3), 2.25 (2H, m, CꢀCHCH2), 1.22–1.33
(4H, m, CH2(CH2)2CH3), 1.08 (3H, t, OCH2CH3), 0.87
(3H, t, CH2CH2CH3). 13C-NMR: l=159.27 (1JSn,C
=
604.1 Hz, SnCꢀC), 138.95 (1JSn,C=520.0 Hz, i-C),
136.97 (2JSn,C=37.4 Hz, o-CH), 128.97 (4JSn,C=11.4
Hz, p-CH), 128.58 (3JSn,C=50.7 Hz, m-CH), 128.77
(SnCꢀC), 68.44 (3JSn,C=26.2 Hz, OCH2CH3), 31.86
3.2.4.11. (Z)-1-Methylthio-2-triphenylstannylhept-1-ene
(5b)
Work-up procedure c. Purity 92% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 6.78 (1H, s,
3JSn,H=151.3 Hz, SnCꢀCH), 2.31 (2H, m,
SnCCH2CH2), 2.02 (3H, s, SCH3), 1.26 (2H, m,
SnCCH2CH2), 1.04–1.08 (4H, m, CH2(CH2)2CH3), 0.72
(4JSn,C=6.2 Hz, SnCꢀCHCH2CH2), 25.32 (3JSn,C
=
41.2 Hz, SnCꢀCHCH2), 22.41 (CH2CH2CH3), 15.37
(OCH2CH3), 13.94 (CH2CH2CH3). 119Sn-NMR: l=
−149.4.
(3H, t, CH2CH2CH3). 13C-NMR: l=148.47 (1JSn,C
=
3.2.4.7. (Z)-1-Ethoxy-1-triphenylstannylhex-1-ene (3d)
Work-up procedure a. Purity 75% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 5.50 (1H, t,
505.8 Hz, SnCꢀC), 139.48 (1JSn,C=523.7 Hz, i-C),
137.04 (2JSn,C=47.7 Hz, o-CH), 136.60 (SnCꢀC),
128.67 (4JSn,C=12.9 Hz, p-CH), 128.29 (3JSn,C=50.5
Hz, m-CH), 39.98 (2JSn,C=44.4 Hz, SnCCH2CH2),
31.10 (CH2CH2CH3), 29.88 (3JSn,C=12.5 Hz,
SnCCH2CH2), 22.15 (CH2CH2CH3), 17.50 (4JSn,C=5.6
Hz, SCH3), 13.88 (CH2CH2CH3). 119Sn-NMR: l=
−143.0.
3
3JH,H=7.6 Hz, JSn,H=126.9 Hz, SnCꢀCH), 3.80 (2H,
q, OCH2CH3), 1.92 (2H, m, SnCꢀCHCH2), 0.99–1.36
(4H, m, CH2(CH2)2CH3), 0.93 (3H, t, OCH2CH3), 0.66
(3H, t, CH2CH2CH3). 119Sn-NMR: l= −168.3.
3.2.4.8. (E)-1-Ethylthio-2-triphenylstannylethene (4a)
1
Work-up procedure b. Purity 100% (1H-NMR). H-
3.2.4.12. (Z)-1-Methylthio-1-triphenylstannylhept-1-ene
(5c)
NMR: l=7.25–7.74 (15H, m, C6H5), 6.67 (1H, d,
3JH,H=18.4 Hz, 3JSn,H=73.2 Hz, SnCHꢀCH), 6.21
Work-up procedure c. Purity 97% (1H-NMR). 1H-
NMR: l=7.25–7.74 (15H, m, C6H5), 5.88 (1H, t,
3
2
(1H, d, JH,H=18.4 Hz, JSn,H=75.1 Hz, SnCHꢀCH),
2.75 (2H, q, SCH2CH3), 1.27 (3H, t, SCH2CH3). 13C-
NMR: l=143.28 (2JSn,C=24.5 Hz, SnCHꢀC), 138.11
(1JSn,C=539.7 Hz, i-C), 136.96 (2JSn,C=37.6 Hz, o-
3
3JH,H=6.8 Hz, JSn,H=67.5 Hz, SnCꢀCH), 2.34 (2H,
m, CꢀCHCH2), 2.10 (3H, s, SCH3), 1.37 (2H, m,
CꢀCHCH2CH2), 1.24–1.31 (4H, m, CH2(CH2)2CH3),
0.85 (3H, t, CH2CH2CH3). 13C-NMR: l=146.26
(2JSn,C=34.2 Hz, SnCꢀC), 138.96 (1JSn,C=527.2 Hz,
CH), 129.05 (4JSn,C=11.1 Hz, p-CH), 128.55 (3JSn,C
=
51.4 Hz, m-CH), 117.61 (1JSn,C=503.5 Hz, SnCHꢀC),
24.86 (SCH2CH3), 14.01 (SCH2CH3). 119Sn-NMR: l=
i-C), 136.91 (2JSn,C=36.8 Hz, o-CH), 136.04 (1JSn,C
=

94
T. Le´bl et al. / Journal of Organometallic Chemistry 625 (2001) 86–94
505.6 Hz, SnCꢀC), 129.09 (4JSn,C=11.1 Hz, p-CH)
128.65 (3JSn,C=52.7 Hz, m-CH), 31.52 (CH2CH2CH3),
31.05 (3JSn,C=52.0 Hz, SnCꢀCHCH2), 28.53
References
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=
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3.3. Reactions with acids in CDCl3 and kinetic
measurements
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added to the organotin substrate (ca. 100 mg) in CDCl3
(ca. 0.5 ml) in an NMR tube. Obtained solutions were
ca. 0.2 M in tin substrate and ca. 0.4 M in acid. The
1
courses of reaction were followed by means of H- and
119Sn-NMR spectroscopy. Gas samples from the NMR
tube were analysed by means of gas chromatography
for 2a, 2b, 4a and 4b.
For kinetic mesurements (2a, 2b, 3a, 3b, 4a, and 4b)
the exact amount of HMDS (5 ml) was also added and
1H-NMR spectra were measured in particular intervals.
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xt is conversion at a particular time, versus time were
obtained and second-order rate constants were calcu-
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Acknowledgements
We thank Dr A.H. Maulitz (Martin-Luther-Universi-
ta¨t Halle-Wittenberg, Halle (Saale), Germany) for per-
forming calculations of NBO charges and Dr A.
Kolonicˇny´ (Research Institute of Organic Synthesis,
Pardubice-Rybitv´ı, Czech Republic) for help with
preparative HPLC. Financial support from the Grant
Agency of the Czech Republic (grant GA 203/00/920;
T.L., J.H., M.D.), from the Ministry of Education,
Youth and Sports (grant COST OC D8.20/1997; T.L.,
J.H., M.D.) is gratefully acknowledged. T.L. thanks the
Land Sachsen Anhalt for a grant.
[19] L. Brandsma, Preparative Acetylenic Chemistry, 2nd edn, El-
sevier, Amsterdam, 1988, p. 54.
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