Spacer-bridged ladder compounds - Syntheses, structures and synthetic applications

Article abstract of DOI:10.1016/S0022-328X(98)00935-8

The reaction of α,ω-bis(organodichlorostannyl)alkanes [R(Cl₂)SnCH₂]₂Z with their corresponding organotin oxides [R(O)SnCH₂]₂Z or (t-Bu₂SnO)₃ provides the new spacer-bridged tetra

Full text of DOI:10.1016/S0022-328X(98)00935-8

Journal of Organometallic Chemistry 574 (1999) 176–192
Spacer-bridged ladder compounds—syntheses, structures and synthetic
applicationsꢀ
Michael Mehring a, Markus Schu¨rmann a, Ingo Paulus a, Dagmar Horn a, Klaus Jurkschat a,*,
Akihiro Orita b, Junzo Otera b, Dainis Dakternieks c, Andrew Duthie c
a Lehrstuhl fu¨r Anorganische Chemie II der Uni6ersita¨t Dortmund, D-44221 Dortmund, Germany
b Department of Applied Chemistry, Okayama Uni6ersity of Science, Ridai-cho, Okayama 700-0005, Japan
c School of Biological and Chemical Science, Deakin Uni6ersity, Geelong, Victoria 3217, Australia
Received 3 August 1998; received in revised form 24 August 1998
Abstract
The reaction of h,ꢀ-bis(organodichlorostannyl)alkanes [R(Cl2)SnCH2]2Z with their corresponding organotin oxides
[R(O)SnCH2]2Z or (t-Bu2SnO)3 provides the new spacer-bridged tetraorganodistannoxanes {[R(Cl)SnCH2]2Z]O}n (22, Z=CH2,
R=Me3SiCH2; 23, Z=CH2, R=Me3CCH2; 24, Z=CH2CH2, R=Me3SiCH2; 25, Z=CH2CH2, R=Me3CCH2; 26, Z=
CH2CH2, R=Me2CHCH2; 27, Z=Me2Si, R=Me3SiCH2). The acetate substituted derivative 28 {[R(AcO)SnCH2]2CH2]O}n
(R=Me3SiCH2) is obtained by reaction of 22 with silver acetate or by treatment of the organotin oxide [R(O)SnCH2]2CH2
(R=Me3SiCH2) with acetic acid. The crystal structures of 23, 24, and 28 are described and reveal that these compounds adopt
double ladder structures. Depending on the identity of Z and R in chloroform solution the compounds are either dimers (n=2,
25–28) or tetramers (n=4, 22–24). Also reported are preliminary studies on the catalytic activity in acylation reactions of
compounds 22, 24–26, and 28. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Tin; Distannoxanes; Crystal structure; NMR; Catalysis
1. Introduction
rmed that the so-called ladder geometry originally
proposed by Okawara et al. [15,16] is retained in the
solid state [17]. The characteristic structural feature of
this ladder type arrangement (A) is the planar four
membered Sn2O2 ring. However, cryoscopic measure-
ments [18] and solution 119Sn-NMR studies [19] for
[R2(AcO)SnOSn(OAc)R2]2 (R=Bu, Et, Me) indicate
partial dissociation into the monomeric species at low
concentrations (B0.02 mol l−1). Furthermore, 119Sn-
NMR studies in solution of an equimolar mixture of
the tetraorganodistannoxanes [Bu2(X)SnOSn(X)Bu2]2
and [Bu2(Y)SnOSn(Y)Bu2]2 provided evidence for the
formation of the mixed tetraorganodistannoxane
[Bu2(X)SnOSn(Y)Bu2]2 (X=O2CMe2, Cl, OPh, OMe;
Y=Cl, OPh, OMe) [20].
Dimeric tetraorganodistannoxanes of the type
[R2XSnOSnXR2]2 (X=Cl, OH, R%COO, NCS; R, R%=
alkyl, aryl) have been found to be efficient catalysts in
a variety of organic reactions [1–14]. Their potential in
organic synthesis has been demonstrated especially for
transesterifications under virtually neutral conditions
[2–6] and for the highly selective acylation of alcohols
[7,8]. The catalytic activity of distannoxanes in this type
of reaction was reported to be the result of their
dimeric structure [1,4–6] in solution. X-ray crystallog-
raphy of a great number of distannoxanes has confi-
ꢀ Dedicated to the memory of the late Professor Rokuro Okawara.
* Corresponding author. Tel.+49-231-755-3800; fax: +49-231-
755-3797; e-mail: kjur@platon.chemie.uni-dortmund.de.
Recently, we reported on the synthesis of spacer-
bridged di- and tri-tin compounds such as [R(Cl2)Sn]2-
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00935-8

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
177
(CH2)n (R=Me3SiCH2, (Me3Si)2CH, Ph; n=1–4) [21]
and [(RCl2Sn)(CH2)3]2SnCl2 (R=Me3SiCH2) [22]. The
reaction of (Me3SiCH2(Cl2)SnCH2)2CH2 with (t-
Bu2SnO)3 [23] provided the first organostannoxane
{[Me3SiCH2(Cl)Sn(CH2)3Sn(Cl)CH2SiMe3]O}4 with a
B-type double ladder structure [24]. A triple ladder
structure was formed by the reaction of {[Me3SiCH2-
(Cl2)Sn](CH2)3]2SnCl2 with (t-Bu2SnO)3 [22]. In con-
trast the reaction of sterically crowded [(Me3Si)2-
CH(Cl2)SnCH2]2CH2 with KF/H2O gave {(Me3Si)2-
CH(F)Sn(CH2)3Sn(F)CH(SiMe3)2]O}2 with a dimeric
C-type ladder structure of [25] whereas the reaction of
[(Me3Si)2CH(Cl2)SnCH2]2CH2 with (t-Bu2SnO)3 pro-
vided the monomeric diorganostannoxane {(Me3Si)2-
CH(Cl)Sn(CH2)3Sn(Cl)CH(SiMe3)2]O} (D-type) [25].
Apparently, the nature of both R and X control the
degree of association in spacer-bridged organodistan-
noxanes of the general formula {[R(X)Sn(CH2)3-
Sn(X)R]O}n.
Scheme 1. Reaction sequence for the preparation of compounds 4–9.
(i) 2I2, −2 PhI, (ii) excess KF/H2O, 2KI, (iii) 2RMgCl, −2MgClF
(R=Me3SiCH2, Me3CCH2, Me2CHCH2).
solvents. They were used in subsequent reactions with-
out further purification. Compounds 1–3 were con-
verted into the tetraorganotin derivatives (Ph2RSn-
CH2)2Z (4, Z=CH2, R=Me3SiCH2 [24]; 5, Z=CH2,
R=Me3CCH2; 6, Z=CH2CH2, R=Me3SiCH2; 7,
Z=CH2CH2, R=Me3CCH2; 8, Z=CH2CH2, R=
Me2CHCH2; 9, Z=SiMe2, R=Me3SiCH2) by reaction
with the appropriate Grignard reagents RMgCl (R=
Me3SiCH2, Me3CCH2, Me2CHCH2) (Scheme 1). Com-
pounds 4–9 were obtained as oils and were used in
subsequent reactions without further purification. The
119Sn-NMR data of the intermediate products 4–9 are
given in Table 1.
Reaction of the tetraorganotin derivatives 4–9 with
HCl or mercuric chloride afforded the tetrachloro
derivatives [R(Cl2)SnCH2]2Z (10, Z=CH2, R=Me3Si-
CH2 [24]; 11, Z=CH2, R=Me3CCH2; 12, Z=CH2-
CH2, R=Me3SiCH2; 13, Z=CH2CH2, R=Me3CCH2;
14, Z=CH2CH2, R=Me2CHCH2; 15, Z=SiMe2,
R=Me3SiCH2) (Eq. (1)). The tetrachloro derivatives
10–15 were isolated as crystalline solids. The 119Sn-
NMR data of compounds 10–15 are given in Table 1.
4HCl/−4PhH
(Ph2RSnCH2)2
Z
“
or 4HgCl /−4PhHgCl (10, 12, 15)
2
[R(Cl2)SnCH2]2Z
(1)
In continuation of our investigations on the influence
of R, X, and the alkylidene spacer on the structure of
organostannoxanes we now report on the syntheses of
various compounds with B- and C-type ladder struc-
tures. Furthermore, we also report on the catalytic
activity of some representative organostannoxanes in
acylation reactions of alcohols.
Table 1
119Sn-NMR data of (Ph2RSnCH2)2Z (4–9) and [R(Cl2)SnCH2]2Z
(10–15). Chemical shifts are given in ppm
(Ph2RSnCH2)2Z
[R(Cl)SnCH2]2Z
l(119Sn)
l(119Sn)
Z=CH2;
R=Me3SiCH2 [24]
Z=CH2;
(4)
(5)
(6)
(7)
(8)
(9)
−62.4
(10)
(11)
(12)
(13)
(14)
(15)
132.8
107.9
135.9
113.4
120.2
134.7
2. Results and discussion
−87.6
−59.9
−83.3
−76.9
−89.7
R=Me3CCH2
Z=CH2CH2;
R=Me3SiCH2
Z=CH2CH2;
R=Me3CCH2
Z=CH2CH2;
R=Me2CHCH2
Z=SiMe2;
2.1. Synthetic aspects
The reaction of (Ph3SnCH2)2Z (Z=CH2 [21a],
CH2CH2 [26], SiMe2 [22]) with iodine and subsequently
with KF/H2O gave the organotin fluorides (Ph2FSn-
CH2)2Z (1, Z=CH2 [27]; 2, Z=CH2CH2; 3, Z=SiMe2
[22]) which are almost insoluble in common organic
R=Me3SiCH2

178
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
where 10, Z=CH2, R=Me3SiCH2; 11, Z=CH2, R=
Me3CCH2; 12, Z=CH2CH2, R=Me3SiCH2; 13, Z=
CH2CH2, R=Me3CCH2; 14, Z=CH2CH2, R=Me2
CHCH2; 15, Z=SiMe2, R=Me3SiCH2.
Polymeric organotin oxides are usually obtained by
complete hydrolysis of diorganotin dichlorides whereas
partial hydrolysis of the latter gives dimeric tertaorgan-
odistannoxanes [28]. In case of spacer-bridged di-tin
compounds the reaction conditions of partial hydrolysis
are difficult to control and normally lead to complex
reaction mixtures. However, (t-Bu2SnO)3 can be used as
source of anhydrous O2− to convert the tetrachloro
di-tin precursors 10–15 into their corresponding organ-
otin-oxo-chloro-species (B–D) [22,24,25].
Scheme 2. Synthesis of the double ladder compounds (B–type) 22–
24.
An alternative and even better method to obtain these
compounds is the reaction of the tetrachloro di-tin
derivatives with their corresponding organotin oxides
[25]. The polymeric organotin oxides 16–21 were pre-
pared by heating at reflux a mixture of the corresponding
tetrachloro di-tin compounds 10–15 and sodium hydrox-
ide in toluene/water (Eq. (2)). The almost insoluble
organotin oxides 16–21 were isolated as colourless solids
with melting points above 300°. The 119Sn-MAS-NMR
spectra of the organotin oxides 16, 17, and 21 show broad
signals (W1/2 ca. 3000 Hz) at −153 (16), −165 (17), and
−157 ppm (21), which are indicative for polymeric
structures with hypercoordinate tin atoms.
C-type geometries with the B-type species dominating.
The double ladder structures of compounds 22–24 in
solution were confirmed by molecular weight determina-
tions (Table 3).
However, the negative ion ES mass spectrum of a
solution of 24 in acetonitrile show cluster patterns at
m/z=1126, m/z=2217, and m/z=2236 which are in-
dicative for the presence of [24 (B-type)+2 OH]2−, [24
(B-type)−Cl+2OH]−, and [26 (B-type)+OH]−. Fur-
thermore at m/z=590 a cluster pattern being consistent
with the anion E (Chart 2). The formation of E can be
explained by dissociation of the C-type structure of 24
and complexation of a chloride.
n{R(Cl2)SnCH2]2ZNaOH/water/toluene
{[R(O)SnCH2]2Z}n
“
(2)
where 16, Z=CH2, R=Me3SiCH2; 17, Z=CH2, R=
Me3CCH2; 18, Z=CH2CH2, R=Me3SiCH2; 19, Z=
CH2CH2, R=Me3CCH2; 20, Z=CH2CH2, R=Me2-
CHCH2; 21, Z=SiMe2, R=Me3SiCH2.
Reaction of [R(Cl2)SnCH2]2Z (10, Z=CH2, R=
Me3SiCH2; 11, Z=CH2, R=Me3CCH2; 12, Z=
CH2CH2, R=Me3SiCH2) with (t-Bu2SnO)3 as well as
the reaction of 10–12 with their corresponding organotin
oxides 16–18 provided almost quantitatively the tin-oxo-
chloro clusters 22–24 (Scheme 2). The use of polymeric
[Me2SnO]n instead of (t-Bu2SnO)3 as source of O2−
resulted in an incomplete conversion of the tetrachloro
di-tin compounds into compounds of type B. Obviously,
this is the result of a side reaction of Me2SnCl2 formed
during the reaction with unreacted [Me2SnO]n to give the
tetraorganodistannoxane [(Me2ClSn)2O]2 [29].
Table 2
119Sn-NMR data of the ladder type compounds 22–28a
Snexo
Snendo
22
23
24
−96.1 [67]
−132.9 [69]
−106.0
−155.1
−68.1 [70] (48%);
−68.9 (2%)
−141.2 (2%);
The119Sn-NMR spectra (Table 2) of 22–24 show two
signals of equal integral ratio at −96.1/−132.9 ppm
(22), −106.0/−155.1 ppm (23), and −68.1/−143.0
ppm (24), respectively. Furthermore, in the 119Sn-NMR
spectrum of the tetramethylene-bridged compound 24
there appeared two additional signals of minor but equal
intensity (ca. 2%) at −68.9 and −141.2 ppm which are
assigned to the C-type ladder compound (Scheme 3). For
the tetramethylene-bridged organostannoxane 24 an
equilibrium probably exists in solution between B- and
−143.0 [70] (48%)
−152.5 [61] (25%);
−153.0 [61] (25%)
−147.2 [71] (10%);
−149.8 [71] (40%)
−116.6 [82]
25
26
−84.7 [61] (25%);
−86.1 [61] (25%)
−77.6 [71] (10%);
−78.8 [71] (40%)
−60.6
27
28b
−169.0 [191] (45%);
−194.9 [112] (5%)
−202.0 [192] (45%);
−224.4 [112] (5%)
a . The chemical shifts are given in ppm and the coupling constants
(2J(119Sn–O–117/119Sn)) in Hz.
b Concentration: 100 mg ml−1
.

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
179
Scheme 3. Proposed equilibrium between B–type and C–type ladder structures of 24–26 in solution.
In the solid state the double ladder structures of 22
[22], 23, and 24 were confirmed by X-ray crystallogra-
phy (see below). The 119Sn-CP-MAS-NMR spectrum of
compound 23 displays two resonances at −104 and
−158 ppm which are very close to the resonances
found in solution (−106.0/−155.1 ppm). This indi-
cates the structure of the stannoxane to be basically the
same in solution and in the solid state.
To get further information on the influence of the
spacer on the structure of spacer-bridged tin-oxo-chloro
species we prepared [Me3SiCH2(Cl2)SnCH2]2SiMe2 (15)
which has the more bulky –CH2SiMe2CH2-spacer. Re-
action of 15 with its corresponding tin oxide as well as
its reaction with (t-Bu2SnO)3 gave the tetraorgan-
odistannoxane 27 (Scheme 5). The molecular weight
determination of 27 (Table 3) is consistent with the
formation of a C-type structure in solution. Two signals
of equal intensity at −60.6 and −116.6 ppm are
observed in the 119Sn-NMR spectrum of 27 in solution
(Table 2). The 119Sn-CP-MAS-NMR spectrum shows
two broad resonances at −71 and −136 ppm which
indicate the solution and solid state structures of 27 to
be very similar.
The exchange of the chlorine atoms in compound 22
by acetate groups leads to the formation of the organ-
otin-oxo-acetate cluster 28 (Scheme 6) with a B-type
structure in the solid state which was confirmed by
X-ray crystallography. In solution, compound 28 ex-
hibits the same B-type/C-type equilibrium that was
postulated for the tetramethylene-bridged ladder com-
pounds 24–26. The acetate substituted ladder com-
pound 28 was prepared by the reaction of the B-type
ladder compound 22 with silver acetate or by the
reaction of the organotin oxide 16 with acetic acid. The
molecular weight determination of 28 in CHCl3 is in
agreement with a C-type ladder structure dominating in
solution at low concentration (Table 3). The 119Sn-
NMR spectrum of 28 in CH2Cl2 at low concentration
(100 mg ml−1) displays two major signals at −169.0
and −202.0 ppm and two signals of minor but equal
intensity at −194.9 and −224.4 ppm. At a higher
concentration (200 mg ml−1) the intensity of the latter
signals increases. When the concentration is lowered
again, the intensity of these signals decrease. This con-
centration dependent 119Sn-NMR spectrum can be ex-
plained by the existence of an equilibrium between B-
and C-type structures with the B-type structure domi-
nating at higher concentration. The 119Sn-CP-MAS-
NMR spectrum of 28 shows two equally intense signals
at −179 and −194 ppm.
Replacement of R=Me3SiCH2 in the tetrachloro
di-tin compound 12 by R=Me3CCH2 (13) or
Me2CHCH2 (14) has a strong influence on the structure
of the compounds formed by partial oxygen/chlorine
exchange. The reaction of [R(Cl2)SnCH2]2Z (13, Z=
CH2CH2, R=Me3CCH2; 14, Z=CH2CH2, R=
Me2CHCH2) with (t-Bu2SnO)3 as well as the reaction of
13 and 14 with their corresponding tin oxides 19 and 20
provided the tetraorgandistannoxanes 25 and 26
(Scheme 4). In solution, 25 and 26 exist in an equi-
librium between B- and C-type ladder geometries as was
described for 24 (Scheme 3). The 119Sn-NMR spectrum
of 25 and 26 each displays two sets of two signals at
−84.7/−152.5 ppm and −86.1/−153.0 ppm for 25
with an integral ratio of 1:1:1:1 and at −77.6/−147.2
ppm and −78.8/−149.8 ppm for 26 with the integral
ratio of 1:1:4:4. The resonances at low field are assigned
to the exocyclic tins and those at high field to the
endocyclic tins of both B- and C-type ladder structures.
The molecular weights in solution of 25 and 26 lie in
between the expected values for a B- and C-type struc-
ture (Table 3) and support the proposed equilibrium
according to Scheme 3. In addition the electrospray
mass spectrum of a solution of 25 in acetonitrile indi-
cates the presence of both B- and C-type structures. The
negative ion mass spectrum shows a cluster pattern at
m/z=2088 which is consistent with the existence of [25
(B-type)+2OH−Cl]−. The positive ion mass spec-
trum shows cluster patterns at m/z=2054 for [25 (B-
type)−Cl]+, m/z=2037 for [25 (B-type)−2Cl
+OH]+, m/z=2017 for [25 (B-type)−3Cl+2OH]+,
and at m/z=523 which is assigned to the presence of
the cation F (Chart 2). The latter is formed by a
dissociation/protonation process of the C-type structure
of 25.

180
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
Table 3
Molecular weight determinations (g mol−1) of ladder type compounds 22–28
Compound
B-type (calc.)
C-type (calc.)
Found
Solvent
Concentration (mg ml−1
)
22
23
24
25
26
27
28
2163
2034
2219
2090
1978
2334
2352
1082
1017
1105
1045
989
1948
2247
2173
1207
1213
1048
972
CHCl3
CHCl3
CH2Cl2
CH2Cl2
CHCl3
CHCl3
CHCl3
7
20
11
16
21
20
20
1167
1176
The infrared spectrum in KBr of 28 shows two
w(COO)as and w(COO)sym absorptions. The w(COO)as at
1627 cm−1 is attributed to a monodentate acetate
group and the w(COO)as at 1564 cm−1 to a bidentate
acetate group [18,30]. In the free acid the asymmetric
absorbtion w(COO)as is at 1718 cm−1 and in sodium
acetate w(COO)as is observed at 1583 cm−1 [31]. For
the monodentate acetate group the w(COO)sym appears
at 1324 cm−1 whereas the w(COO)sym of the chelating
carboxylate group appears at 1376 cm−1. Thus, the Dw
values (Dw=w(COO)as−w(COO)sym) amount to 303
cm−1 for the monodentate and 188 cm−1 for the
unsymmetrically chelating acetate group of 28. These
results are in line with the molecular structure discussed
below. The infrared spectrum of 28 in solution (5% in
CHCl3) shows the same general trend that was found in
the solid state. Two absorptions appear for w(COO)as at
1596 and 1555 cm−1 and two absorptions for
w(COO)sym at 1423 and 1383 cm−1, which are assigned
to one bidentate and one monodentate acetate group.
The Dw value for the bidentate ligand amounts to 213
cm−1, which indicates a weaker bonding of the acetate
group to the tin atom in solution.
greatest deviation from the plane found in 23 for Cl(1)
˚
˚
(0.159(1) A) and in 24 for O(1) (0.080(6) A). In the
acetate derivative 28 a large distortion of the Sn4X4O2
(X=OAc) layer was observed and the largest deviation
˚
is found for O(56) (0.806(4) A).
The tin atoms in 23 and 24 each have a distorted
trigonal bipyramidal geometry. For the exocyclic tin
atoms, two carbons and one oxygen occupy the equato-
rial positions and two chlorines occupy the axial posi-
tions, while for the endocyclic tins the equatorial
positions are occupied by two carbons and one oxygen
and the axial positions by one oxygen and one chlorine.
The bond lengths and bond angles in 23 and 24 show
no peculiarities and are similar to those reported for 22
[24]. In 23 and 24 the shortest Sn–O bond lengths are
˚
found for the exocyclic tins (23 Sn(1)–O(1) 2.020(3) A;
˚
24 Sn(4)–O(2) 2.010(6) A) and the longest Sn–O bonds
˚
exist in the Sn2O2 core (23 Sn(2)–O(2) 2.187(3) A; 24
˚
Sn(3)–O(2) 2.111(6) A). It is worth noting that the
difference in the Sn–O bond lengths is greater in 23
than 24, which corresponds to the shorter Sn–Cl bond
lengths of the bridging chlorine atoms found in 23
˚
˚
(Sn(2)–Cl(2) 2.577(2) A, Sn(3)–Cl(4) 2.625(2) A) com-
˚
pared to 24 (Sn(2)–Cl(4) 2.784(3) A, Sn(3)–Cl(1)
˚
2.2. Molecular structures of 23, 24, and 28
2.829(3) A).
In 28 the configuration around the tin atoms is best
described as distorted trigonal bipyramid with each tin
atom having two carbons and one oxygen in the equa-
torial positions and two oxygens in the axial positions.
In contrast to 23, 24, [(Me2SnO2CC6H4-p-CH3)2O]2
[17c], [(n-Bu2SnO2CC6H4-o-CH3)2O]2 [17d], and [(n-
Bu2SnO2CC6H4-o-OH)2O]2 [17d] the shortest Sn–O
The molecular structures of compound 23, 24, and 28
are shown in Figs. 1–3 and selected bond distances and
bond angles are given in Tables 4–6. The structures of
23, 24, and 28 contain a center of inversion and consist
of typical double-ladder B-type arrangements [22,24] in
which the monolayers are linked by four trimethylene
(23, 28) and four tetramethylene bridges (24). The
Sn4Cl4O2 layers in 23 and 24 are almost planar with the
Scheme 4. Synthesis of ladder compounds starting from
[R(Cl2)SnCH2]2Z (13, Z=CH2CH2, R=Me3CCH2; 14, Z=
CH2CH2, R=MeCH2CH2) by reaction with (i) (t–Bu2SnO)3 or (ii)
the corresponding tin oxides {[R(O)SnCH2]2Z}n (19, 20).
Scheme 5. Synthesis of the C–type ladder compound 27. (i) (t–
Bu2SnO)3 or (ii) {[R(O)SnCH2]2Z}n (21) (Z=SiMe2; R=
Me3SiCH2).

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
181
change reaction. Normally, this process requires protic
reaction conditions [40]. Recently, the use of
Cp2*Sm(THF)2 and SmI2 as catalysts in the transester-
ification under inert conditions has been reported [41].
Previously, we reported that 1,3-dichlorotetrabu-
tyidistannoxane [16], which adopts a ladder structure,
serves as an efficient catalyst in the acylation of alco-
hols as well as in transesterification (enol-ester route)
under virtually neutral conditions [8]. We therefore
investigated the properties of selected spacer-bridged
stannoxanes as catalysts in acylation reactions of alco-
hols with acetic anhydride (Scheme 7) and in acyla-
tion reactions with alkenyl acetates (Scheme 8).
In the acylation reaction of PhCH2CH2OH and n-
C8H17OH with Ac2O the compounds 22 and 24–26
have been tested (Table 8). Although all compounds
show moderate catalytic activities it is worth noting
that the conversion rate of PhCH2CH2OH catalyzed
by 22 is very low (entry 1), whereas 24–26 show no
significant differences in activity. For the conversion
of n-C8H17OH, high yields were obtained by the use
of 25 (entry 7), but only moderate yields were ob-
tained with 22, 24, and 26.
Scheme 6. Preparation of the acetate ladder 28.
bond lengths for 28 were found in the Sn2O2 core
˚
˚
(Sn(2)–O(2) 2.036(5) A; Sn(3)–O(1) 2.028(5) A) as
was previously described for [(n-Bu2SnO2CCH2-
C6F6)2O]2 [17e]. In 28 as well as in the above men-
tioned dicarboxylatotetraorganodistannoxanes two
carboxylate groups of each layer are bonded in a
bidentate fashion and two carboxylate groups show a
monodentate coordination mode. The Sn–O bond
distances for the chelating acetate lie in between the
˚
value for Sn(3)–O(52) (2.231(6) A) and Sn(4)–O(56)
˚
(2.282(7) A). The Sn–O bond lenghts for the
˚
monodentate acetate groups amount to 2.207(6) A for
˚
Sn(1)–O(53) and 2.213(6) A for Sn(4)–O(57). The
Transesterifications with alkenyl acetates were car-
ried out with the compounds 22, 24–26, and 28 as
catalysts (Scheme 8, Table 9). In the presence of 25,
2-phenylethanol as well as n-octanol were converted
in high yields (entries 3, 7 and 11) and the same holds
for 24 (entry 2) and 26 (entries 4 and 12). The
trimethylene-bridged acetate double ladder 28 shows
slightly lower conversion rates (entries 5, 9 and13)
than the tetramethylene-bridged compounds 24–26. In
contrast to these results only low yields of conversion
have been observed for the trimethylene-bridged dou-
ble-ladder 22 (entries 1, 6 and 10).
These preliminary experiments suggest that the
tetramethylene-bridged compounds 24–26 are more
efficient catalysts in acylation reactions than the
trimethylene-bridged compound 22. Furthermore, the
catalytic activity of the trimethylene-bridged and
acetate containing compound 28 is only slightly lower
than the activity of the tetramethylene-bridged deriva-
tives 24–26. These differences in catalytic activity
seem to correlate with their structures in solution. We
have shown the double-ladder structure of 22 to be
kinetically inert in solution, whereas 24–26 and 28 are
kinetically labile and show an equilibrium between B-
and C-type structures in solution. Although all of the
compounds tested here are less efficient catalysts when
compared to the simple 1,3-dichlorotetrabutyldistan-
noxane, they can serve as models to study the rela-
tionship of structure and catalytic activity.
Furthermore, preliminary investigations show com-
pound 25 to discriminate effectively between primary
and secondary alcohols in acetylation reactions.
bond angles of the bridging carboxylate ligands
(O(51)–C(51)–O(52) 127.0(10)°; O(55)–C(55)–O(56)
127.3(10)°) correspond to
a bidentate character,
whereas the bond angles of the non-bridging carboxy-
late ligands (O(53)–C(53)–O(54) 119.4(11)°; O(58)–
C(57)–O(57) 123.9(11)°) are indicative of
a
monodentate coordination mode. Furthermore, there
are weak intramolecular Sn···O interactions between
˚
Sn(1) and O(54) (2.634(7) A), Sn(2) and O(53)
˚
˚
(3.124(7) A), Sn(3) and O(57) (3.077(7) A), and Sn(4)
˚
and O(58) (2.622(7) A), which result in distortions
from the ideal trigonal bipyramidal geometries at the
tin atoms. The structural arrangement within the lad-
der layer of 28 represents that of the most common
type of dicarboxylatotetraorganodistannoxanes [17b].
2.3. Distannoxane-catalyzed acylation of alcohols
Acylation of alcohols [32] as well as transesterifica-
tions [1,33] are the most important synthetic routes
for the convenient synthesis of ester functionalized or-
ganic reagents. Due to their synthetic importance a
large variety of catalysts has been studied in the last
decade. For the acylation of alcohols with acetic an-
hydride either basic systems such as 4-(dialkyl-
aminopyridine)-catalysts [34], Bu3P [35], MgBr2–R3N
[36] and an aminophosphine superbase [37] or Lewis
acidic catalysts such as Sc(OTf)3 [38] and TiCl(OTf)3
[39] were used. The reversibility of the transesterifica-
tion limits their application, but this problem can be
overcome by the use of enol esters, which are trans-
formed into aldehydes or ketones upon the inter-

182
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
Fig. 1. General view (SHELXTL-PLUS) of a molecule showing 30% probability displacement ellipsoids and the atom numbering (symmetry
transformations used to generate equivalent atoms: a= −x, −y, −z) for 23.
3. Experimental
of 10 ml min−1. Nitrogen was used as both a drying gas
and for nebolization with flow rates of approx 200 ml
min−1, and 20 ml min−1, respectively. Pressure in the
mass analyzer region was usually about 4×10−5 mbar.
Typically ten signal averaged spectra were collected.
The organotin fluorides (Ph2FSnCH2)2Z (1, Z=CH2;
2, Z=CH2CH2; 3, Z=SiMe2) were prepared according
to literature procedures [27] and were used in further
reactions without purification. Published procedures
were used to prepare [Ph3SnCH2]2(CH2)2 [26], [Ph2(Me3
SiCH2)SnCH2]2CH2 (4), [(Me3SiCH2)(Cl2)SnCH2]2CH2
All solvents were dried and purified by standard
procedures. Bruker DPX-300 and DRX400 spectrome-
ters were used to obtain 1H-, 13C-, 29Si- and 119Sn-NMR
spectra. Chemical shifts l are given in ppm and were
referenced against Me4Si or Me4Sn. 119Sn-CP-MAS
spectra were obtained from a Bruker MSL 400 spec-
trometer using cross-polarization and high power pro-
ton decoupling. Cy4Sn was used as a secondary
reference (l −97.35 ppm). The IR spectra were
recorded on a Bruker IFS 28 spectrometer. Molecular
weight determinations were performed on a Knaur
osmometer.
The electrospray mass spectra obtained with a Plat-
form II single quadrupole mass spectrometer (Micro-
mass, Altrincham, UK) using an acetonitrile mobile
phase. Acetonitrile solutions of the compounds were
injected directly into the spectrometer via a Rheodyne
injector equipped with a 50 ml loop. A Harvard 22
syringe pump delivered the solutions to the vaporiza-
tion nozzle of the electrospray ion source at a flow rate
(10),
{[Me3SiCH2(Cl)Sn(CH2)3Sn(Cl)CH2SiMe3]O}4
(22) [24] and di(tert-butyl)tin oxide [23].
The typical experimental procedures for the acylation
reactions follow below.
3.1. Acylation with acetic anhydride
An acetonitrile solution (1 ml) of alcohol (5 mmol),
Ac2O (10 mmol) and an organotin cluster (0.05 mmol)
was stirred at 30°C for 20–50 h. The reaction mixture
was washed with a NaHCO3 solution and extracted

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
183
Fig. 2. General view (SHELXTL-PLUS) of a molecule showing 25% probability displacement ellipsoids and the atom numbering (symmetry
transformations used to generate equivalent atoms: a= −x, −y+1, −z+1) for 24.
with EtOAc. The solvent was removed in vacuum and
the residue subjected for GLC analysis with C18H38 as
internal standard. The crude mixture was purified by
column chromatography on silica gel.
to-detector distance was 2.6 cm (23) and 2.7 cm (24,
28). Crystal decay was monitored by repeating the
initial frames at the end of data collection. Analyzing
the duplicate reflections showed no indication of any
decay. The structures were solved by direct methods
SHELXS86 [42] and successive difference Fourier syn-
theses. Refinement applied full-matrix least-squares
methods SHELXL93 [43].
3.2. Acylation with alkenyl esters
To an alkenyl ester solution (3 ml) was added alcohol
(5 mmol) and an organotin cluster (0.05 mmol). The
solution was stirred for 24–48 h. The alkenyl ester was
evaporated and the residue was subjected for GLC
analysis with C18H38 as internal standard. The crude
mixture was purified by column chromatography on
silica gel.
The H atoms were placed in geometrically calculated
positions using a riding model and refined with a
˚
common isotropic temperature factor (Caryl–H 0.93 A,
Cprim. –H 0.96, Csec..–H 0.97, Uiso 0.104(8) (23), 0.202(8)
2
˚
(24), and 0.106(8) (28) A ).
Disordered SiMe3 groups were found in 24 with an
occupancy of 0.65 (C(42), C(43)), 0.35 (C(42%), C(43%)),
and 0.5 (C(12), C(13), C(14), C(44); C(12%), C(13%),
C(14%), C(44%)) and in 28 with an occupancy of 0.7
(Si(1), C(12), C(13), C(14); Si(4), C(42), C(43), C(44))
and 0.3 (Si(1%), C(12%), C(13%), C(14%); Si(4%), C(42%),
C(43%), C(44%)). Solvent molecules benzene 24 and
toluene 28 (with an occupancy of 0.5) and the C atoms
of the disordered SiMe3 groups in 28 were refined
isotropically.
3.3. Crystallography
Intensity data for the colorless crystals were collected
on a Nonius KappaCCD diffractometer with graphite-
˚
monochromated Mo–Kh radiation (0.71069 A) at 291
K. The data collections covered the sphere of reciprocal
space with 360 frames via ꢀ-rotation (D/ꢀ=1°) at two
times 5 s (23) and 10 s (24, 28) per frame. The crystal-

184
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
Fig. 3. General view (SHELXTL-PLUS) of a molecule showing 30% probability displacement ellipsoids and the atom numbering (symmetry
transformations used to generate equivalent atoms: a= −x, −y, −z+1) for 28.
Atomic scattering factors for neutral atoms and real
and imaginary dispersion terms were taken from refer-
ence [44]. Figures were created by SHELXTL-Plus [45].
Crystallographic data are given in Table 7 and selected
bond distances and bond angles are listed in Table 4
(23), Table 5 (24) and Table 6 (28).
solution was extracted two times with 50 ml diethyl
ether and the etheral extract dried over Na2SO4. After
filtration the solvent was removed in vacuo, yielding
10.61 g of 1,3-bis[diphenyl(2,2-dimethylpropyl)stannyl]
propane (5) (119Sn-NMR (CDCl3/Cr(acac)3, 111.92
MHz): l= −87.6 ppm) as a yellow oil. The oily
residue was dissolved in 100 ml methylene chloride and
a stream of HCl gas passed through the solution for 2
h. The solid material was filtered, the solvent removed
in vacuo and the residue recrystallized from hexane to
give 4.54 g (56%) 11 as colourless crystals of m.p.
72–73°C.
3.4. Synthesis of [(Me3CCH2)(Cl2)SnCH2]2CH2 (11)
To a solution of Me3CCH2MgBr prepared from
Me3CCH2Br (7.98 g, 53 mmol) and magnesium turn-
ings (1.41 g, 58 mmol) in 70 ml THF, 1,3-bis(diphenyl-
fluorostannyl)propane (1) (9.95 g, 16 mmol) was added
in small portions. The reaction mixture was stirred for
16 h at room temperature and than heated at reflux for
1 h. The solvent was removed in vacuo to give a yellow
oil which was dissolved in 70 ml diethyl ether and
washed with 250 ml aqueous 2 M HCl. The aqueous
1H-NMR (CDCl3, 400.13 MHz): l 1.12 (s, 18H,
C(CH3)3); l 1.87 (t, 4H, CH2Sn); l 2.08 (s, 4H,
CH2Sn); l 2.37 (complex pattern, 2H, CH2). 13C-NMR
(CDCl3, 100.63 MHz): l 20.8 (CH2); l 30.0, 32.1
(CH2Sn); l 33.1 (Me3C); l 46.8 (Me3C).119Sn-NMR
(CDCl3, 111.92 MHz): l 107.9. Anal. Calc. for

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
185
Table 4
Selected bond distances (A) and angles (°) for 23
˚
Sn(1)–O(1)
Sn(2)–O(1)
Sn(1)–Cl(1)
Sn(1)–Cl(2)
Sn(1)–C(1)
Sn(1)–C(11)
Sn(2)–C(2)
2.020(3)
2.056(3)
2.735(2)
2.452(2)
2.129(5)
2.124(5)
2.114(5)
Sn(2)–O(2)
Sn(3)–O(1)
Sn(2)–Cl(1)
Sn(3)–Cl(4)
Sn(2)–C(21)
Sn(3)–C(2¦a)
Sn(3)–C(31)
2.187(3)
2.157(3)
2.577(2)
2.625(2)
2.122(5)
2.119(5)
2.125(5)
Sn(3)–O(2)
Sn(4)–O(2)
Sn(4)–Cl(3)
Sn(4)–Cl(4)
Sn(4)–C(1¦a)
Sn(4)–C(41)
2.046(3)
2.029(3)
2.437(2)
2.809(2)
2.134(5)
2.127(5)
O(1)–Sn(1)–C(11)
O(1)–Sn(1)–C(1)
C(11)–Sn(1)–C(1)
O(1)–Sn(1)–Cl(2)
C(11)–Sn(1)–Cl(2)
C(1)–Sn(1)–Cl(2)
O(1)–Sn(1)–Cl(1)
C(11)–Sn(1)–Cl(1)
C(1)–Sn(1)–Cl(1)
Cl(2)–Sn(1)–Cl(1)
O(1)–Sn(2)–C(2)
O(1)–Sn(2)–C(21)
C(2)–Sn(2)–C(21)
O(1)–Sn(2)–O(2)
C(2)–Sn(2)–O(2)
C(21)–Sn(2)–O(2)
107.1 (2)
114.9(2)
135.1(2)
91.31(9)
98.3(2)
96.0(2)
76.52(9)
89.1(2)
O(1)–Sn(2)–Cl(1)
C(2)–Sn(2)–Cl(1)
C(21)–Sn(2)–Cl(1)
O(2)–Sn(2)–Cl(1)
O(2)–Sn(3)–C(2¦a)
O(2)–Sn(3)–C(31)
C(2¦a)–Sn(3)–C(31)
O(2)–Sn(3)–O(1)
C(2¦a)–Sn(3)–O(1)
C(31)–Sn(1)–O(1)
O(2)–Sn(3)–Cl(4)
C(2¦a)–Sn(3)–Cl(4)
C(31)–Sn(3)–Cl(4)
O(1)–Sn(3)–Cl(4)
O(2)–Sn(4)–C(41)
O(2)–Sn(4)–C(1¦a)
79.78(10)
88.7(2)
C(41)–Sn(4)–C(1¦a)
O(2)–Sn(4)–Cl(3)
C(41)–Sn(4)–Cl(3)
C(1¦a)–Sn(4)–Cl(3)
O(2)–Sn(4)–Cl(4)
C(41)–Sn(4)–Cl(4)
C(1¦a)–Sn(4)–Cl(4)
Cl(3)–Sn(4)–Cl(4)
Sn(2)–Cl(1)–Sn(1)
Sn(3)–Cl(4)–Sn(4)
Sn(1)–O(1)–Sn(2)
Sn(1)–O(1)–Sn(3)
Sn(2)–O(1)–Sn(3)
Sn(4)–O(2)–Sn(3)
Sn(4)–O(2)–Sn(2)
Sn(3)–O(2)–Sn(2)
135.0(2)
91.77(9)
97.7(2)
98.0(2)
75.07(9)
88.8(2)
100.71(14)
152.39(8)
117.7(2)
108.5(2)
133.7(2)
74.44(11)
97.9(2)
94.9(2)
79.24(9)
88.7(2)
85.5(2)
166.59(5)
82.74(6)
81.88(4)
119.1(2)
133.1 (2)
105.58(13)
122.0(2)
130.69(14)
104.85(12)
85.9(2)
167.24(6)
117.7(2)
110.2(2)
132.1(2)
73.60(11)
97.1(2)
99.3(2)
152.95(9)
106.6(2)
114.8(2)
95.3(2)
C13H28Cl4Sn2: C, 27.70; H, 4.97. Found: C, 27.60; H,
5.00%.
ppm). To a solution of 6 (36.60 g, 47 mmol) in 250 ml
acetone was added a solution of HgCl2 (51.18 g, 188
mmol) in 200 ml acetone at 0°C, followed by stirring
for 15 h at room temperature. The precipitate of Ph-
HgCl was removed by filtration and the solvent re-
moved in vacuo. Diethyl ether (100 ml) was added to
the residue and the suspension was stirred at room
temperature for 10 min. After filtration the solvent was
removed in vacuo. This procedure was repeated three
times giving a colourless solid which was recrystallized
from diethyl ether/hexane (1:1) to give 24.86 g (87%
from 6) of 12 as colourless crystals of m.p. 64–65°C.
1H-NMR (CDCl3, 400.13 MHz): l 0.17 (s, 18H,
3.5. Synthesis of [(Me3SiCH2)(Cl2)SnCH2]2(CH2)2 (12)
To a solution of [Ph3SnCH2]2(CH2)2 (90.0 g, 0.12
mol) in 200 ml methylene chloride was added iodine
(60.4 g, 0.24 mol) at 0°C in small portions. The reaction
mixture was stirred for 16 h at room temperature
before evaporating the solvent in vacuo and removing
the iodobenzene by distillation at 60°C (1×10−3
Torr). The residue was dissolved in 200 ml acetone and
added dropwise to a magnetically stirred solution of
KF (42.0 g, 0.72 mol) in 90 ml water. The suspension
was stirred for 4 h at room temperature and the precip-
itate filtered and washed with 150 ml water and 150 ml
diethyl ether to give quantitatively [Ph2FSnCH2]2(CH2)2
(2) as a colourless solid (75 g, m.p. \300°C), which
was used in subsequent reactions without further purifi-
cation. To a solution of Me3SiCH2MgCl, prepared
from Me3SiCH2Cl (16.1 g, 0.13 mol) and Mg (3.51 g,
0.14 mol) in 250 ml THF, was added 2 (35.0 g, 55
mmol) in small portions. The reaction mixture was
heated at reflux for 2 h and hydrolyzed with 150 ml of
saturated ammonia chloride solution. The organic
phase was separated and the aqueous solution extracted
three times with 150 ml diethyl ether. The combined
organic phases were dried over sodium sulfate which
was then removed by filtration and the solvent evapo-
2
SiMe3); l 0.86 (s, 4H, SiCH2, J(1H–117/119Sn)=87/91
2
Hz); l 1.73 (t, 4H, SnCH2, J(1H–117/119Sn)=52 Hz); l
1.91 (quint, CH2). 13C-NMR (CDCl3, 100.63 MHz): l
1.1 (SiMe3, 3J(13C–117/119Sn)=29 Hz; 1J(13C–29Si)=53
Hz; l 14.8 (SiCH2, 1J(13C–117/119Sn)=378/395 Hz);
20.8 (CH2); l 28.5 (CH2, 2J(13C–117/119Sn)=40 Hz;
3J(13C–117/119Sn)=112/117 Hz);
l
29.8 (SnCH2,
1J(13C–117/119Sn)=556/583 Hz). 119Sn-NMR (CDCl3,
149.21 MHz): l 135.9. 29Si-NMR (acetone-d6, 79.49
MHz): l 2.2. Anal. Calc. for C12H30Cl4Si2Sn2: C, 27.70;
H, 4.97. Found: C, 27.60; H, 5.00%.
3.6. Synthesis of [(Me3CCH2)Ph2SnCH2]2(CH2)2 (7)
To a solution of Me3CCH2MgBr prepared from
Me3CCH2Br (16.0 g, 0.106 mol) and Mg (2.83 g, 0.116
mol) in 250 ml THF was added 1,4-bis(diphenylfluo-
rostannyl)butane (2) (35.0 g, 55 mmol) in small por-
tions. The reaction mixture was heated at reflux for 1
rated
in
vacuo
to
give
36.60
g
(86%)
[Ph2(Me3SiCH2)SnCH2]2(CH2)2 (6) as yellow oil (119Sn-
NMR (CH2Cl2/D2O-cap., 111.92 MHz): l= −59.9

186
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
Table 5
˚
Selected bond distances (A) and angles (°) for 24
Sn(1)–O(1)
Sn(2)–O(1)
Sn(1)–Cl(1)
Sn(1)–Cl(2)
Sn(1)–C(1)
Sn(1)–C(11)
Sn(2)–C(5)
2.018(6)
2.105(5)
2.677(3)
2.497(4)
2.142(13)
2.082(11)
2.069(13)
Sn(2)–O(2)
Sn(3)–O(1)
Sn(2)–Cl(4)
Sn(3)–Cl(1)
Sn(2)–C(21)
Sn(3)–C(8¦a)
Sn(3)–C(31)
2.078(6)
2.063(7)
2.784(3)
2.829(3)
2.068(10)
2.15(2)
Sn(3)–O(2)
Sn(4)–O(2)
Sn(4)–Cl(3)
Sn(4)–Cl(4)
Sn(4)–C(4¦a)
Sn4)–C(41)
2.111(6)
2.010(6)
2.514(4)
2.722(4)
2.10(2)
2.094(10)
2.085(9)
O(1)–Sn(1)–C(11)
O(1)–Sn(1)–C(1)
C(11)–Sn(1)–C(1)
O(1)–Sn(1)–Cl(2)
C(11)–Sn(1)–Cl(2)
C(1)–Sn(1)–Cl(2)
O(1)–Sn(1)–Cl(1)
C(11)–Sn(1)–Cl(1)
C(1)–Sn(1)–Cl(1)
Cl(2)–Sn(1)–Cl(1)
O(1)–Sn(2)–C(5)
O(1)–Sn(2)–C(21)
C(5)–Sn(2)–C(21)
O(1)–Sn(2)–O(2)
C(5)–Sn(2)–O(2)
C(21)–Sn(2)–O(2)
115.2(3)
O(1)–Sn(2)–Cl(4)
C(5)–Sn(2)–Cl(4)
C(21)–Sn(2)–Cl(4)
O(2)–Sn(2)–Cl(4)
O(2)–Sn(3)–C(8¦a)
O(2)–Sn(3)–C(31)
C(8¦a)–Sn(3)–C(31)
O(2)–Sn(3)–O(1)
C(8¦a)–Sn(3)–O(1)
C(31)–Sn(1)–O(1)
O(2)–Sn(3)–Cl(1)
C(8¦a)–Sn(3)–Cl(4)
C(31)–Sn(3)–Cl(1)
O(1)–Sn(3)–Cl(1)
O(2)–Sn(4)–C(41)
O(2)–Sn(4)–C(4¦a)
149.6(2)
C(41)–Sn(4)–C(4¦a)
O(2)–Sn(4)–Cl(3)
C(41)–Sn(4)–Cl(3)
C(4¦a)–Sn(4)–Cl(3)
O(2)–Sn(4)–Cl(4)
C(41)–Sn(4)–Cl(4)
C(4¦a)–Sn(4)–Cl(4)
Cl(3)–Sn(4)–Cl(4)
Sn(1)–Cl(1)–Sn(3)
Sn(2)–Cl(4)–Sn(4)
Sn(1)–O(1)–Sn(2)
Sn(1)–O(1)–Sn(3)
Sn(2)–O(1)–Sn(3)
Sn(4)–O(2)–Sn(3)
Sn(4)–O(2)–Sn(2)
Sn(3)–O(2)–Sn(2)
139.2(7)
84.3(2)
93.9(4)
97.0(7)
77.8(2)
108.2(4)
135.5(5)
83.6(2)
96.3(4)
98.0(4)
78.3(2)
91.4(3)
87.0(4)
161.88(13)
97.8(4)
101.0(3)
147.3(5)
74.3(2)
102.4(5)
108.3(3)
90.0(4)
87.1 (3)
75.3(2)
94.2(4)
101.8(3)
146.4(5)
74.5(2)
104.5(5)
108.1 (3)
148.5(2)
94.7(4)
86.9(3)
74.0(2)
110.5(4)
109.6(6)
92.4(4)
89.1(6)
162.06(12)
82.19(8)
82.19(8)
128.4(3)
125.1 (3)
105.9(3)
130.0(3)
124.6(3)
105.1(2)
day and hydrolyzed with 150 ml of saturated ammonia
chloride solution. The organic phase was separated and
the aqueous solution extracted three times with 150 ml
diethyl ether. The combined organic phases were dried
over sodium sulfate, which was then removed by filtra-
tion and the solvent evaporated in vacuo to give 7 (23.0
g, 83%) as a colourless solid of m.p. 65–66°C.
removal of the solvent in vacuo. This procedure was
repeated until no precipitate was formed. The crude
product was crystallized from diethyl ether/hexane (1:1)
to give 13.66 g (81%) of 13 as colourless crystals of m.p.
76–78°C.
1H-NMR (CDCl3, 400.13 MHz): l 1.11 (s, 18H,
CMe3); l 1.77 (t, 4H, SnCH2, 2J(1H–117/119Sn)=44
Hz); l 1.94 (quint, 4H, CH2); l 2.07 (s, 4H, CCH2,
2J(1H–117/119Sn)=69 Hz). 13C-NMR (acetone-d6,
100.63 MHz): l 27.9 (CH2, 2J(13C–117/119Sn)=35/42
1H-NMR (CDCl3, 400.13 MHz): l 0.96 (s, 18H,
CMe3); l 1.24 (t, 4H, SnCH2); l 1.41 (s, 4H, CCH2,
2J(1H–117/119Sn)=56 Hz); l 1.61 (quint, 4H, CH2);
7.26–7.51 (complex pattern, 20H, Haryl). 13C-NMR
(CDCl3, 100.63 MHz): l 11.7 (SnCH2, 1J(13C–117/
3
1
Hz, J(13C–117/119Sn)=76 Hz); l 29.8 (SnCH2, J(13C–
117/119Sn)=465/486 Hz); l 31.9 (C, J(13C–117/119Sn)=
2
2
119Sn)=349/361 Hz); l 30.3 (C); l 31.5 (CH2, J(13C–
24 Hz); l 32.4 (CMe3, 3J(13C–117/119Sn)=62 Hz); l
47.1 (CCH2, 1J(13C–117/119Sn)=456/477 Hz). 119Sn-
NMR (CH2Cl2/D2O-Cap., 111.92 MHz): l 113.4. Anal.
Calc. for C14H30Cl4Sn2: C, 29.11; H, 5.23. Found: C,
28.95; H, 5.45%.
117/119Sn)=20 Hz, 3J(13C–117/119Sn)=66 Hz); l 31.7
(CCH2); l 33.4 (CMe3 3J(13C–117/119Sn)=35 Hz); l
128.2 (Cm, 3J(13C–117/119Sn)=45 Hz);
l
128.22
(Cp);136.8 (Co, J(13C–117/119Sn)=33 Hz); l 140.1 (Ci,
1J(13C–117/119Sn)=414/432 Hz). 119Sn-NMR (CH2Cl2/
D2O-Cap., 111.92 MHz): l −83.3. Anal. Calc. for
C38H50Sn2: C, 61.33; H, 6.77. Found: C, 61.37; H,
6.36%.
2
3.8. Synthesis of [(Me2CHCH2)(Cl2)SnCH2]2(CH2)2
(14)
To a solution of Me2CHCH2MgBr prepared from
Me2CHCH2Br (12.85 g, 94 mmol) and Mg (2.51 g, 103
mmol) in 250 ml THF was added, 1,4-bis(diphen-
lyfluorostannyl)butane (2) (25.00 g, 39 mmol) in small
portions. The reaction mixture was heated at reflux for
1 day and hydrolyzed with 150 ml of saturated ammo-
nia chloride solution. The organic phase was separated
and the aqueous solution extracted three times with 150
ml diethyl ether. The combined etheral phase was dried
over sodium sulfate, filtered and the solvent evaporated
in vacuo to give 26.88 g (96%) of [Ph2(Me2CHCH2)-
3.7. Synthesis of [(Me3CCH2)(Cl2)SnCH2]2(CH2)2 (13)
To a solution of 7 (21.78 g, 29 mmol) in 250 ml
acetone was added a solution of HgCl2 (31.78 g, 117
mmol) in 150 ml acetone at 0°C. The mixture was
stirred for 15 h at room temperature before removing
the precipitate of PhHgCl by filtration and evaporating
the solvent in vacuo. Diethyl ether (100 ml) was added
to the residue and the suspension stirred at room
temperature for 10 min, followed by filtration and

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
187
Table 6
Selected bond distances (A) and angles (°) for 28
˚
Sn(1)–O(1)
Sn(1)–O(51)
Sn(1)–O(53)
Sn(2)–O(1)
Sn(1)–C(1)
Sn(1)–C(11)
Sn(2)–C(2)
Sn(2)···O(53)
2.061(5)
2.263(7)
2.207(6)
2.167(5)
2.107(8)
2.110(8)
2.122(7)
3.124(7)
Sn(2)–O(2)
Sn(2)–O(55)
Sn(3)–O(1)
Sn(3)–O(2)
Sn(2)–C(21)
Sn(3)–C(2¦a)
Sn(3)–C(31)
Sn(3)···O(57)
2.036(5)
2.232(6)
2.028(5)
2.161(5)
2.103(7)
2.132(8)
2.112(7)
3.077(7)
Sn(3)–O(52)
Sn(4)–O(2)
2.231(6)
2.054(5)
2.282(7)
2.213(6)
2.112(8)
2.106(8)
2.634(7)
2.622(7)
Sn(4)–O(56)
Sn(4)–O(57)
Sn(4)–C(1¦a)
Sn(4)–C(41)
Sn(1)···O(54)
Sn(4)···O(58)
O(1)–Sn(1)–C(1)
O(1)–Sn(1)–C(11)
C(1)–Sn(1)–C(11)
O(1)–Sn(1)–O(53)
C(1)–Sn(1)–O(53)
C(11)–Sn(1)–O(53)
O(1)–Sn(1)–O(51)
C(1)–Sn(1)–O(51)
C(11)–Sn(1)–O(51)
O(53)–Sn(1)–O(51)
O(2)–Sn(2)–C(21)
O(2)–Sn(2)–C(2)
C(21)–Sn(2)–C(2)
O(2)–Sn(2)–O(1)
C(21)–Sn(2)–O(1)
C(2)–Sn(2)–O(1)
O(2)–Sn(2)–O(55)
107.3(3)
C(21)–Sn(2)–O(55)
C(2)–Sn(2)–O(55)
O(1)–Sn(2)–O(55)
O(1)–Sn(3)–C(31)
O(1)–Sn(3)–C(2¦a)
C(31)–Sn(3)–C(2¦a)
O(1)–Sn(3)–O(2)
C(31)–Sn(3)–O(2)
C(¦2a)–Sn(3)–O(2)
O(1)–Sn(3)–O(52)
C(31)–Sn(3)–O(52)
C(2¦a)–Sn(3)–O(52)
O(2)–Sn(3)–O(52)
O(2)–Sn(4)–C(42)
O(2)–Sn(4)–C(1¦a)
C(41)–Sn(4)–C(1¦a)
O(2)–Sn(4)–O(57)
89.1(3)
86.2(3)
165.4(2)
106.1(3)
117.2(3)
136.6(3)
76.0(2)
98.9(3)
93.9(3)
91.0(2)
88.4(3)
88.5(3)
166.4(2)
106.0(3)
109.0(3)
144.2(3)
83.8(2)
C(41)–Sn(4)–O(57)
C(1¦a)–Sn(4)–O(57)
O(2)–Sn(4)–O(56)
C(41)–Sn(4)–O(56)
C(1¦a)–Sn(4)–O(56)
O(57)–Sn(4)–O(56)
Sn(3)–O(1)–Sn(1)
Sn(3)–O(1)–Sn(2)
Sn(1)–O(1)–Sn(2)
Sn(2)–O(2)–Sn(4)
Sn(2)–O(2)–Sn(3)
Sn(4)–O(2)–Sn(3)
O(51)–C(51)–O(52)
O(55)–C(55)–O(56)
O(53)–C(53)–O(54)
O(58)–C(57)–O(57)
98.0(3)
93.1(3)
90.7(2)
88.8(3)
83.5(3)
172.1(2)
129.1(2)
103.0(2)
124.3(2)
129.2(3)
103.0(2)
124.5(2)
127.0(10)
127.3(10)
119.4(11)
123.9(11)
104.3(3)
147.6(4)
84.8(2)
95.3(3)
94.7(3)
91.0(2)
83.4(3)
88.9(3)
175.0(3)
107.3(3)
116.3(2)
136.1(3)
75.7(2)
100.0(3)
94.7(3)
90.9(2)
SnCH2]2(CH2)2 (8) as
a
yellow oil
(
119Sn-NMR
magnesium turnings (1.30 g, 54 mmol) in 40 ml THF
was added 1,3-bis(diphenylfluorostannylmethyl)dime-
thylsilane (3) (11.00 g, 16 mmol) in small portions. The
reaction mixture was stirred for 18 h at room tempera-
ture and heated at reflux for 1 h. The solvent was
removed in vacuo, the resulting oily residue dissolved in
70 ml diethyl ether and hydrolyzed with 60 ml aqueous
2 M HCl. After washing the aqueous solution three
times with 20 ml of diethyl ether the combined organic
extracts were dried over Na2SO4. After filtration the
solvent was removed in vacuo to give 10.1 g of bis
[diphenyl(trimethylsilylmethyl)stannylmethyl]dime-
thylsilane (9) as a yellow oil (119Sn-NMR (CDCl3/Cr(a-
cac)3, 111.92 MHz): l= −89.7). The oily residue was
dissolved in 80 ml acetone and a solution of HgCl2
(14.48 g, 53.34 mmol) in 30 ml acetone was added
dropwise at 0°C. The resulting suspension was stirred
overnight before removing the PhHgCl by filtration.
After removing the solvent in vacuo the solid residue
was suspended in 70 ml diethyl ether, the solid material
filtered off and the solvent removed in vacuo. The
residue was recrystallized from 80 ml hexane to give
4.41 g (43%) of 15 as a colourless solid of m.p. 109–
111°C.
(CH2Cl2/D2O-Cap., 111.92 MHz): l= −76.9 ppm).
Through a solution of 8 (26.88 g, 38 mmol) in 400 ml
CH2Cl2 was passed a stream of HCl gas for 4 h at room
temperature. The solvent was evaporated in vacuo and
the residue crystallized from diethyl ether/hexane (1:1)
to give 19.84 g (96%) of 14 as a colourless solid of m.p.
105–106°C.
1H-NMR (CDCl3, 400.13 MHz): l 1.06 (d, 12H,
CHMe2); l 1.77 (t, 4H, SnCH2); l 1.90 (d, 4H, CHCH2,
2J(1H–117/119Sn)=58/61 Hz); l 1.92 (quint, 4H, CH2);
2.29 (sept, 2H, CH).13C-NMR (acetone-d6, 100.63
MHz): l 25.8 (CHMe2, J(13C–117/119Sn)=77 Hz); l
3
26.1 (CH, 2J(13C–117/119Sn=33 Hz); l 28.5 (CH2,
2J(13C–117/119Sn)=38 Hz, 3J(13C–117/119Sn)=101/105
1
Hz); l 29.1 (SnCH2, J(13C–117/119Sn)=483/504 Hz); l
40.2 (CHCH2, 1J(13C–117/119Sn)=479/502 Hz). 119Sn-
NMR (CH2Cl2/D2O-Cap., 111.92 MHz): l 120.2. Anal.
Calc. for C12H26Cl4Sn2: C, 26.23; H, 4.77. Found: C,
26.51; H, 4.21%.
3.9. Synthesis of [(Me3SiCH2)(Cl2)SnCH2]2SiMe2 (15)
To a solution of Me3SiCH2MgCl prepared from
chloromethyltrimethylsilane (6.50 g, 53 mmol) and
Scheme 7. Stannoxane catalyzed acylation with Ac2O.
Scheme 8. Stannoxane catalyzed acylation with alkenyl acetates.

188
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
Table 7
Crystallographic data for 23, 24, and 28
23
24
28
Formula
C
52H112Cl8O4Sn8
C48H120Cl8O4Si8Sn8·C6H6
2297.39
Triclinic
C60H136O20Si8Sn8·C7H8
2444.06
Monoclinic
0.25×0.20×0.20
P21/n
16.026(1)
22.323(1)
16.744(1)
90
116.984(1)
90
5338.0(5)
2
Formula weight
Crystal system
Crystal size (mm)
Space group
2034.54
Monoclinic
0.15×0.10×0.10
P21/n
15.743(1)
11.335(1)
22.889(1)
90
106.920(1)
90
3907.7(5)
2
0.20×0.10×0.08
(
P1
˚
a (A)
13.015(1)
13.888(1)
16.186(1)
82.693(1)
70.904(1)
61.167(1)
2420.3(3)
1
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
3
˚
V (A )
Z
zcalc. (mg m−3
)
1.729
12.820
1984
1.576
2.380
1130
1.521
1.981
2436
v (mm−1
F(000)
)
q range (°)
Index ranges
4.55–25.67
−195h519
−135k513
−275l526
48 629
2.81–19.61
−125h512
−105k513
−145lB15
12 166
2.55–23.00
−175h517
−245k524
−185l516
26 738
No. of reflections collected
Completeness to qmax
99.6
96.5
91.5
No. of independent reflections (Rint
No. of reflections observed with (I\2|(I))
Absorption correction
)
7335/0.054
4041
None
4104/0.027
2097
None
6825/0.051
3861
None
No. of refined parameters
338
0.859
433
0.864
474
0.917
Goodness-of-fit on F2
R1 (F) (I\2|(I))
0.0330
0.0672
0.0380
0.0954
0.0447
0.0933
wR2 (F2) (all data)
(D/|)max
0.001
0.740/−0.877
B0.001
0.452/−0.379
B0.001
1.196/−0.694
−3
˚
Largest difference peak/hole (e A
)
1H-NMR (CDCl3, 200.13 MHz): l 0.18 (s,18H,
SiMe3); l 0.36 (s, 6H, SiMe2); l 0.88 (s, 4H, SnCH2,
2J(119Sn–1H)=97 Hz); l 0.97 (s, 4H, SnCH2, 2J(119Sn–
1H)=81 Hz). 13C-NMR (CDCl3, 100.63 MHz): l 1.1
(SiMe3); l 2.2 (CH2Si); l 13.3 (CH2Sn); l 13.7
(CH2Sn). 119Sn-NMR (CDCl3/Cr(acac)3, 111.92 MHz):
l 134.7. Anal. Calc. for C12H32Cl4Si3Sn2: C, 22.56; H,
4.85. Found: C, 22.10; H, 4.90%.
3.10. Synthesis of [(Me3SiCH2)(O)SnCH2]2CH2 (16)
To a solution of 10 (3.56 g, 5.88 mmol) in 80 ml
toluene, was added dropwise at room temperature a
solution of NaOH (7.17 g, 0.18 mol) in 50 ml water.
The reaction mixture was heated at reflux for 55 h. The
aqueous phase was separated and the precipitate iso-
lated by filtration to give 16 (2.50 g, 88%) as a colour-
less solid with a m.p. \300°C.
Table 8
Acylation with Ac2Oa
Entry ROH
Com-
pound
Reaction time Yield (%)
(h)
119Sn-CP-MAS-NMR: l −153 ppm. Anal. Calc. for
C11H28O2Si2Sn2: C, 27.18; H, 5.81. Found: C, 27.10; H,
6.30%.
1
2
3
4
5
6
7
8
PhCH2CH2OH 22
48
20
20
48
50
30
30
50
48b
79b
82b
76b
73c
75c
93c
70c
24
25
26
22
24
25
26
3.11. Synthesis of [(Me3CCH2)(O)SnCH2]2CH2 (17)
n-C8H17OH
To a solution of NaOH (4.24 g, 0.11 mmol) in 75 ml
water was added dropwise at room temperature a solu-
tion of 11 (2.00 g, 3.55 mmol) in 75 ml methanol. The
reaction mixture was stirred for 65 h. The precipitate
was isolated by filtration to give 17 (0.93 g, 58%) as a
colourless solid with a m.p. \300°C.
a Reaction conditions: ROH (5 mmol); compound (0.05 mmol);
Ac2O (10 mmol); CH3CN (1 ml).
b Isolated yield after column chromatography.
c GLC yield.

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
189
Table 9
Acylation with alkenyl acetatesa
Entry
ROH
R%
Compound
Reaction time (h)
Yield (%)
1
2
3
4
5
6
7
8
PhCH2CH2OH
H
22
24
25
26
28
22
25
26
28
22
25
26
28
48
24
24
48
48
48
48
48
48
48
24
48
48
57(20)b
94(72)b
95(72)b
92(66)b
88
15
85
75
88
67
98
97
76
CH3
9
10
11
12
13
n-C8H17OH
a Reaction conditions: ROH (5 mmol); compound (0.05 mmol); alkenyl ester (3 ml).
b GLC yield; isolated yield after column chromatography in parenteses.
119Sn-CP-MAS-NMR: −165 ppm. Anal. Calc. for
Cl3H28O2Sn2: C, 34.41; H, 6.22. Found: C, 35.00; H,
6.55%.
3.15. Synthesis of [(Me3SiCH2)(O)SnCH2]2SiMe2 (21)
To a solution of 15 (1.18 g,1.84 mmol) in 35 ml
toluene was added dropwise a solution of NaOH (2.21
g, 55.20 mol) in 20 ml water. The reaction mixture was
heated at reflux for 3 days. The precipitate which
formed was isolated by filtration to give 21 (0.85 g,
87%) as a colourless solid of m.p. \300°C.
119Sn-CP-MAS-NMR: −157 ppm. Anal. Calc. for
C12H32O2Si3Sn2: C, 27.19; H, 6.09. Found: C, 27.40; H,
6.20%.
3.12. Synthesis of [(Me3SiCH2)(O)SnCH2]2(CH2)2 (18)
To a solution of NaOH (5.90 g, 148 mmol) in 50 ml
water was added, dropwise at 0°C, a solution of 12
(3.00 g, 5 mmol) in 30 ml methanol. The reaction
mixture was stirred for 4 days. The precipitate was
isolated by filtration and washed with 100 ml water and
150 ml methanol to give 18 (1.65 g, 67%) as colourless
a solid with a m.p. \350°C.
3.16. Synthesis of {[(Me3CCH2(Cl)SnCH2)2CH2]O}4
(23)
Anal. Calc. for C12H30O2Si2Sn2: C, 28.83; H, 6.05.
Found: C, 28.60; H, 6.10%.
3.16.1. Method A
To a solution of 11 (800 mg, 1.40 mmol) in 10 ml
methylene chloride was added (t-Bu2SnO)3 (353 mg,
0.50 mmol) at room temperature. The resulting solution
was heated at reflux for 10 min and left for 2 h at room
temperature. The precipitate was filtered and dried in
vacuo to give 616 mg (86%) of 23 as a colourless solid
of m.p. 295–297°C.
3.13. Synthesis of [(Me3CCH2)(O)SnCH2]2(CH2)2 (19)
In a similar manner to 18, compound 19 was pre-
pared from NaOH (6.23 g, 156 mmol) and 13 (3.00 g, 5
mmol) and was obtained as a colourless solid (2.06 g,
85%) of m.p. \350°C. Anal. Calc. for C14H30O2Sn2: C,
35.95; H, 6.46. Found: C, 35.30; H, 6.70%.
3.16.2. Method B
3.14. Synthesis of [(Me2CHCH2)(O)SnCH2]2(CH2)2
(20)
To a solution of 11 (274 mg, 0.49 mmol) in 10 ml
methylene chloride was added 17 (222 mg, 0.49 mmol)
at room temperature. The resulting suspension was
stirred at room temperature until the solution became
clear. Recrystallization from methylene chloride at
−20°C yielded 277 mg (57%) of 23 as a colourless solid
of m.p. 300–302°C.
In a similar manner to 18, compound 20 was pre-
pared from NaOH (8.73 g, 218 mmol) and 14 (3.00 g, 5
mmol) and was obtained as a colourless solid (2.24 g,
93%) of m.p. \350°C.
Anal. Calc. for C12H26O2Sn2: C, 32.78; H, 5.96.
Found: C, 32.40; H, 5.90%.
1H-NMR (CDCl3, 400.13 MHz): l 1.09 (s, 36H,
(CH3)3C); l 1.21 (s, 36H, (CH3)3C); l 1.73 (complex

190
M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
pattern, 8H, CH2); l 1.86 (s, 8H, CH2Sn); l 2.02 (s, 8H,
CH2Sn); l 2.43 (complex pattern, 8H, CH2Sn); l 2.55
(complex pattern, 8H, CH2Sn). 13C-NMR (CDCl3,
100.63 MHz): l 20.9 (CH2); l 21.5 (CH2); l 31.8 (Me3C);
l 32.3 (Me3C); l 33.4 (Me3C); l 33.7 (Me3C); l 38.1
(CH2Sn); l 39.9 (CH2Sn); l 48.2 (CH2Sn); l 52.5
(CH2Sn). 119Sn-NMR (CDCl3, Cr(acac)3, 111.92 MHz):
l −106.0; l −155.1. Molecular weight determination
=61 Hz, 25%); l −153.0 (2J(Sn–117/119Sn)=61 Hz,
25%). Molecular weight determination (CH2Cl2): 1207 g
mol−1. Anal. Calc. for C28H60Cl4O2Sn4: C, 32.17; H,
5.78. Found: C, 31.70; H, 5.50%.
3.18.2. Method B (in situ generation)
Compound 13 (200 mg, 0.346 mol) and (t-Bu2SnO)3
(86 mg, 0.115 mmol) were dissolved in 3 ml CHCl3 and
heated to 50°C for 2 min. A 119Sn-NMR spectrum of this
solution was recorded. 119Sn-NMR (CHCl3, D2O-Cap.,
111.92 MHz): l 53.9 (t-Bu2SnCl2); l −83.9 (22%); l
−86.2 (28%); l −147.6 (28%); l −148.2 (22%).
(CHCl3): 2247
g
mol−1
.
Anal. Calc. for
C64H112Cl8O4Sn8: C, 30.70; H, 5.55. Found: C, 31.20; H,
5.95%.
3.17. Synthesis of {[(Me3SiCH2(Cl)SnCH2)2(CH2)2]O}4
(24)
3.19. Synthesis of {[(Me2CHCH2(Cl)SnCH2)2
(CH2)2]O}2 (26)
To a solution of 12 (1.52 g, 2.50 mmol) in 50 ml
toluene was added 18 (1.25 g, 2.50 mmol) at room
temperature. The reaction mixture was heated at reflux
for 12 h. After filtration the solvent was evaporated in
vacuo and the residue crystallized from toluene to give
24 (2.42 g, 87%) as colourless crystals of m.p. 203–
204°C.
3.19.1. Method A
In a similar manner to 23 (method A), compound 26
was prepared from 14 (0.62 g, 1.14 mmol) and 20 (0.50
g, 1.14 mmol) and obtained as a colourless solid (1.08 g,
96%) with a m.p. 215–216°C.
1H-NMR (CDCl3, 400.13 MHz): l 1.02–1.06 (com-
plex pattern, 24H, Me2CHCH2); 1.73–1.97 (complex
pattern, 24H, SnCH2/CH2); 2.25–2.40 (complex pattern,
4H, Me2CHCH2). 13C-NMR (CDCl3, 100.63 MHz):
l=24.50, 24.86, 24.99 (Me2CHCH2); 24.70, 24.81,
25.06, 25.13 (Me2CHCH2); 26.57, 27.09, 27.70, 28.04,
30.00, 31.36, 32.78, 41.95, 42.55, 43.13, 43.43 (CH2Sn)
[46]. 119Sn-NMR (toluene, D2O-Cap., 111.92 MHz): l
−77.6 (2J(119Sn–117/119Sn)=71 Hz, 10%); l −78.8
(2J(119Sn–117/119Sn)=71 Hz, 40%); l −147.2 (2J(119Sn–
1H-NMR (CDCl3, 400.13 MHz): l 0.13 (s, 36H,
Me3Si); l 0.17 (s, 36H, Me3Si); l 0.88 (s, 8H, CH2Si); l
0.92 (s, 8H, CH2Si); l 1.67–2.06 (complex pattern, 32H,
CH2Sn/CH2). 13C-NMR (CDCl3, 100.63 MHz): l 1.28
3
(CH3Si, J(13C–117/119Sn)=52/60 Hz); l 1.84 (CH3Si,
3J(13C–117/119Sn)=52/60 Hz); l 18.10 (SiCH2); l 19.41
(SiCH2); l 28.31 (CH2); l 29.14 (CH2); l 30.94 (SnCH2);
l 32.65 (SnCH2). 119Sn-NMR (toluene, D2O-Cap.,
111.92 MHz): l −68.1 (2J(119Sn–117/119Sn)=70 Hz,
48%); l −68.9 (2%); l −141.2 (2%); l −143.0
(2J(119Sn–117/119Sn)=70 Hz, 48%). Molecular weight
determination (CHCl3): 2173 g mol−1. Anal. Calc. for
C48H120Cl8O4Si8Sn8: C, 25.98; H, 5.45. Found: C, 25.80;
H, 5.60%.
117/119Sn)=71 Hz, 40%);
l
−149.8 (2J(119Sn–
117/119Sn)=71 Hz, 10%). Molecular weight determina-
tion (CHCl3): 1213 g mol−1. Anal. Calc. for C24H52-
Cl4O2Sn4: C, 29.14; H, 5.30. Found: C, 28.90; H, 5.10%.
3.19.2. Method B
3.18. Synthesis of {[(Me3CCH2(Cl)SnCH2)2(CH2)2]O}2
(25)
Compound 14 (200 mg, 0.364 mmol) and (t-Bu2SnO)3
(91 mg, 0.121 mmol) were dissolved in 3 ml CHCl3 and
heated at 50°C for 2 min. A 119Sn-NMR spectrum of this
solution was recorded. 119Sn-NMR (CHCl3, D2O-Cap.,
111.92 MHz): l 53.6 (t-Bu2SnCl2); l −78.1 (2J(119Sn–
117/119Sn) not observed, 10%); l −78.4 (2J(119Sn–
3.18.1. Method A
In a similar manner to 23 (method A), compound 25
was prepared from 13 (1.85 g, 3.2 mmol) and 19 (1.50
g, 3.2 mmol) and obtained as a colourless solid (2.86 g,
85%) of m.p. 183–184°C.
117/119Sn)=72 Hz, 40%);
l
−144.1 (2J(119Sn–
117/119Sn)=72 Hz, 40%); l −145.4 (2J(119Sn–117/119Sn)
1H-NMR (CDCl3, 400.13 MHz): l 1.08 (s, 9H, Me3C);
l 1.09 (s, 9H, Me3C); l 1.18 (s, 9H, Me3C); l 1.20 (s,
9H, Me3C); l 1.62–2.24 (complex pattern, 16H, CH2Sn/
CH2); l 2.04 (CH2Sn); l 2.05 (CH2Sn); l 2.12 (CH2Sn);
l 2.13 (CH2Sn). 13C-NMR (CDCl3, 100.63 MHz): l=
24.84, 27.01, 27.53, 29.07, 30.05, 32.05 34.54 (CH2/
SnCH2); 31.98, 32.00, 32.03 (C); 33.04, 33.14, 33.28
(CMe3); 49.91; 50.10, 52.56, 52.65 (CCH2) [46]. 119Sn-
NMR (toluene, D2O-Cap., 111.92 MHz): l −84.7
(2J(119Sn–117/119Sn)=61 Hz, 25%); l −86.1 (2J(119Sn–
117/119Sn)=61 Hz, 25%); l −152.5 (2J(119Sn–117/119Sn)
not observed, 10%).
3.20. Synthesis of {[(Me3SiCH2(Cl)SnCH2)2SiMe2]O}2
(27)
3.20.1. Method A
To a solution of 15 (362 mg, 0.57 mmol) in 35 ml
methylene chloride was added 21 (300 mg, 0.57 mmol).
The reaction mixture was heated at reflux for 20 h and
after filtration the solvent was evaporated to give 540 mg
(82%) 27 as a colourless solid of m.p. 123–126°C.

M. Mehring et al. / Journal of Organometallic Chemistry 574 (1999) 176–192
191
1H-NMR (CDCl3, 400.13 MHz): l 0.12 (s, 18H,
Me3Si); l 0.20 (s, 18H, Me3Si); l 0.26 (s, 6H, Me2Si); l
0.34 (s, 6H, Me2Si); l 0.67-1.23 (complex pattern, 16H,
CH2Sn). 13C-NMR (CDCl3, 100.63 MHz): l 1.2
(Me3Si, 1J(13C–29Si)=29 Hz); 1.8 (Me3Si, 1J(13C–
29Si)=30 Hz); l 3.7 (Me2Si); l 5.8 (Me2Si, 1J(13C–
29Si)=50 Hz); l 14.9 (CH2Sn); l 17.7 (CH2Sn); 19.8
(CH2Sn); 21.2 (CH2Sn). 119Sn-NMR (CDCl3, 111.92
MHz): l −60.6; l −116.6 (2J(119Sn–117/119Sn)=82
Hz). 29Si-NMR (CDCl3, 59.63): 1.2 (SiMe2); 1.9
(2J(29Si–119Sn)=39 Hz, Me3Si); l 4.7 (2J(29Si–119Sn)=
59 Hz, Me3Si). 119Sn-CP-MAS-NMR: l −71; l −136
ppm. Molecular weight determination (CHCl3): 1048 g
mol−1. Anal. Calc. for C24H64O2Cl2Si6Sn4: C, 24.64; H,
5.52. Found: C, 25.00; H, 5.90%.
3.21.2. Method B (in situ generation of 28)
Compound 16 (300 mg, 0.62 mmol) and acetic acid
(74 mg, 1.23 mmol) were dissolved in 40 ml toluene.
The reaction mixture was heated at reflux in a Dean
Stark apparatus for 6 h. The solvent was removed in
vacuo and the residue dissolved in 2.5 ml CHCl3/
CDCl3. The clear solution was examined by 119Sn-
NMR spectroscopy. 119Sn-NMR (CHCl3/CDCl3,
111.92 MHz): l −169.6; l −196.1; l −204.3; l
−225.5 (integral ratio 5:1:5:1).
4. Supplementary material available
Tables of anisotropic thermal parameters and hydro-
gen atom coordinates, complete bond lengths, angles
and torsions angles for compounds 23, 24, and 28 are
available from KJ.
3.20.2. Method B
Compound 15 (100 mg, 0.17 mmol) and (t-Bu2SnO)3
(84 mg, 0.34 mmol) were dissolved in 3 ml CHCl3 and
heated at 50°C for 2 min. A 119Sn-NMR spectrum of
this solution was recorded. 119Sn-NMR (CHCl3, D2O-
Acknowledgements
2
Cap., 111.92 MHz): l −64.8 J(119Sn–117/119Sn)=80
2
Hz; l −121.3 J(119Sn–117/119Sn) 78 Hz).
We are grateful to the Deutsche Forschungsgemein-
schaft, the Fonds der Chemischen Industrie and the
Australian Research Council for financial support.
3.21. Synthesis of {[(Me3SiCH2(OAc)SnCH2)2CH2]O}4
(28)
References
3.21.1. Method A
Silver acetate (1.11 g, 6.66 mmol) was added at room
temperature to a solution of 22 (1.80 g, 0.832 mmol) in
250 ml toluene and the reaction mixture stirred for 8
days in the dark. The solid material was removed by
filtration and the solution concentrated to 10 ml. Crys-
tallization at 0°C yielded 740 mg (38%) of 28 as colour-
less crystals of m.p. 163–167°C.
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1H-NMR (CDCl3, 400.13 MHz): l 0.09 (s, 36H,
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