Synthesis and structural characterization of (4,7-dioxaoctyl)phenyldichlorostannane and triphenyltin compounds containing various polyoxaalkyl moieties

Article abstract of DOI:10.1016/S0022-328X(01)01088-9

The synthesis and characterization of (4,7-dioxaoctyl)triphenyltin (1), (4,7,10-trioxaundecyl)triphenyltin (2), (4,7,10,13-tetraoxatetradecyl)triphenyltin (3), and (4,7-dioxaoctyl)phenyldichlorostannane (4) are reported. Investigatons using ¹H-, ¹³C-, and ¹¹⁹Sn-NMR, gradient assisted 2D ¹H-¹³C HMBC and HMQC NMR, 1D ¹H-¹¹⁹Sn HMQC NMR demonstrate that 1-3 are essentially tetracoordinated. By contrast, the structure of compound 4, determined by X-ray diffraction methods, reveals a hexacoordinated, distorted octahedral geometry, in which the 4,7-dioxaoctyl ligand is tridentate, with a facial arrangement of the C, O, O atoms with respect to tin. NMR investigations reveal that this structure exists in solution, but is labilized by a double ring opening-closing mechanism.

Full text of DOI:10.1016/S0022-328X(01)01088-9

Journal of Organometallic Chemistry 634 (2001) 55–60
www.elsevier.com/locate/jorganchem
Synthesis and structural characterization of
(4,7-dioxaoctyl)phenyldichlorostannane and triphenyltin
compounds containing various polyoxaalkyl moieties
Martine Kemmer a,c, Monique Biesemans a,b, Marcel Gielen a,c, Edward R.T. Tiekink d,
Rudolph Willem a,b,
*
a AOSC Unit, Faculty of Applied Sciences, Free Uni6ersity of Brussels (VUB), Pleinlaan 2, B-1050 Brussel, Belgium
b High Resolution NMR Centre HNMR, Free Uni6ersity of Brussels (VUB), Room 8G508, Pleinlaan 2, B-1050 Brussel, Belgium
c Ser6ice de Chimie Organique, Brussels Free Uni6ersity (ULB), A6enue F. D. Roose6elt 50, B-1050 Bruxelles, Belgium
d Department of Chemistry, The Uni6ersity of Adelaide, Adelaide 5005, Australia
Received 25 April 2001; received in revised form 18 May 2001; accepted 25 June 2001
Abstract
The synthesis and characterization of (4,7-dioxaoctyl)triphenyltin (1), (4,7,10-trioxaundecyl)triphenyltin (2), (4,7,10,13-tetraox-
atetradecyl)triphenyltin (3), and (4,7-dioxaoctyl)phenyldichlorostannane (4) are reported. Investigatons using 1H-, 13C-, and
119Sn-NMR, gradient assisted 2D 1H–13C HMBC and HMQC NMR, 1D 1H–119Sn HMQC NMR demonstrate that 1–3 are
essentially tetracoordinated. By contrast, the structure of compound 4, determined by X-ray diffraction methods, reveals a
hexacoordinated, distorted octahedral geometry, in which the 4,7-dioxaoctyl ligand is tridentate, with a facial arrangement of the
C, O, O atoms with respect to tin. NMR investigations reveal that this structure exists in solution, but is labilized by a double
ring opening–closing mechanism. © 2001 Published by Elsevier Science B.V.
Keywords: Polyoxaalkylstannanes; NMR; X-ray diffraction
(CH3)2]2SnCl2 [12] and [(CH3)2NCH2CH2CH2]2SnF2
[13] all feature a hexacoordinated tin atom because of
two additional intramolecular O“Sn or N“Sn inter-
actions.
Related to these studies, the coordination behavior of
different alkyl substituted monoorganotin trichlorides
has also been investigated for CH3COO(CH2)nSnCl3
(n=3–5) [14], HO(CH2)nSnCl3 (n=3–5) [15] and
CH3OCH2CH2OCH2CH2CH2SnCl3 [11] which display
intra- and/or inter-molecular associations in solution
and/or solid state.
1. Introduction
In the solid state, diorganotin dihalides show a
strong tendency to undergo polymeric associations of
the type SnꢀX···Sn by intermolecular coordination [1,2].
They can also expand the valence shell at tin by addi-
tional intramolecular coordination of electronegative
substituents containing an O or N atom linked to
carbon chains themselves bound to tin. Thus, a number
of octahedral L2SnX2 complexes, where L2 is a chelat-
ing ligand forming one SnꢀC covalent bond and a
O“Sn or N“Sn coordinative bond, have been re-
ported [3–7]. The following compounds, (RCOCH2-
CH2)2SnCl2 (R=OCH3 or NH2) [8], (EtOOCCH2-
CHRCH2)2SnBr2 (R=COOEt) [9,10], (CH3OCH2CH2-
This report describes the synthesis and characteriza-
tion of (4,7-dioxaoctyl)triphenyltin (1), (4,7,10-triox-
aundecyl)triphenyltin
(2),
(4,7,10,13-tetraoxatetra-
decyl)triphenyltin (3), and (4,7-dioxaoctyl)phenyl-
dichlorostannane (4) (Fig. 1). They each possess at least
two potential additional donor sites. Our main inves-
OCH2CH2CH2)2SnCl2
[11],
[(CH3)2NCH2CH2C-
1
tigative tools are H-, 13C-, and 119Sn-NMR, gradient
* Corresponding author. Tel.: +32-2-6293282; fax: +32-2-
6293281.
E-mail address: rwillem@vub.ac.be (R. Willem).
assisted 2D 1H–13C HMBC and HMQC NMR, 1D
1H–119Sn HMQC NMR, as well as electrospray mass
0022-328X/01/$ - see front matter © 2001 Published by Elsevier Science B.V.
PII: S0022-328X(01)01088-9

56
M. Kemmer et al. / Journal of Organometallic Chemistry 634 (2001) 55–60
Fig. 1. Structures of compounds 1–4.
spectrometry and 119mSn Mo¨ssbauer spectroscopy. The
crystal structure of compound 4 has been determined
by X-ray diffraction methods.
23Na, 35Cl, 39K, 120Sn), were observed in the cationic
mode, in MeOH solution.
2.2. Crystal structure determination
2. Experimental
Intensity data for colorless 4 were measured at 173 K
on a Rigaku AFC7R diffractometer employing Mo–Ka
radiation and the ꢀ–2q scan technique such that qmax
was 27.5°. Corrections were made for Lorentz and
polarization effects [28] and for absorption employing
an empirical procedure [29]. Crystallographic data are
summarized in Table 1.
2.1. Spectroscopic measurements
NMR spectra for basic compound characterization
were recorded at 303 K on a Bruker Avance DRX250
instrument equipped with a Quattro probe tuned to
250.13, 62.93 and 89.15 MHz for H, 13C and 117Sn
1
The structure was solved by heavy-atom methods [30]
and refined by a full-matrix least-squares procedure
based on F [28]. All non-hydrogen atoms were refined
with anisotropic displacement parameters and hydrogen
atoms were included in the model in their idealized
positions. After the inclusion of a weighting scheme of
nuclei, respectively. Other NMR data were acquired on
a Bruker AMX500 spectrometer at 500.13 and 186.50
1
1
MHz for H and 119Sn nuclei, respectively. H and 13C
chemical shifts were referenced to the appropriate sol-
vent peak with the usual values calibrated against
Me4Si. The 117Sn and 119Sn reference frequencies were
calculated from the absolute references ](117Sn)=
35.632295 MHz and ](119Sn)=37.290655 MHz [16].
2D 1H–13C HMQC [17] and HMBC [18] as well as
1H–119Sn HMQC correlation spectra were acquired
using the pulse sequences of the Bruker program li-
brary, adapted to include gradient pulses [19–22] as
described previously [23,24].
2
the form w=1/[|2(F)+0.00001ꢀFꢀ ], the refinement
Table 1
Crystallographic parameters for compound 4
Formula
C12H18Cl2O2Sn
Formula weight
Crystal size (mm)
Crystal system
Space group
383.9
0.13×0.24×0.27
Monoclinic
P21/c
Chemical shifts are in ppm, coupling constants in Hz,
nJ(1H–1H) in parentheses, and nJ(119Sn–1H) and
nJ(119Sn–13C) between square brackets; abbreviations:
s=singlet; t=triplet, tt=triplet of triplets; m=com-
plex multiplet.
,
a (A)
13.373(5)
7.464(2)
14.602(2)
97.31(2)
1445.6(7)
4
1.764
760
21.24
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
The Mo¨ssbauer spectra were recorded as described
elsewhere [25].
Dcalc (cm−3
F(000)
)
The electrospray mass spectra [26,27] were recorded
in the cationic mode on a Micromass Quattro II instru-
ment coupled to a Masslynx system (ionization in an
electric field of 3.5 kV; source temperature: 80 °C;
source pressure 1 atm; analyzer pressure 10−5 mbar).
The monoisotopic fragment-ions (1H, 12C, 14N, 16O,
v (cm−1
)
Unique data
3573
Data with I]3|(I)
2589
R
0.022
Rw
z (e A
0.025
0.56
−3
,
)

M. Kemmer et al. / Journal of Organometallic Chemistry 634 (2001) 55–60
57
ESMS: M+Na+, 491; M+K+, 507.
Mo¨ssbauer: QS, 0.71 mm s−1; IS, 1.29 mm s−1
.
2.3.2. (4,7,10-Trioxaundecyl)triphenyltin
The same procedure was used as described for 1 in
the synthesis of (4,7,10-trioxaundecyl)triphenyltin, com-
pound 2, except for the column chromatography [silica/
1: CH2Cl2; 2: CH2Cl2–CH3CH2OH (1:1)] (65%).
Anal. Calc. for C26H32O3Sn: C, 61.08; H, 6.31.
Found: C, 60.6; H, 6.4%.
1H-NMR (CDCl3): l=7.50–7.55 m, 6H [2J(119Sn–
1H)=47], H(o); l=7.31–7.38 m, 9H, H(m) and H(p);
l=1.46–1.52 m, 2H [2J(119Sn–1H)=57], H(1); l=
1.95–2.02 m, 2H [3J(119Sn–1H)=55], H(2); l=3.42–
3.47 m, 4H, H(3) and H(5); l=3.48–3.53 m, 4H, H(6)
and H(9); l=3.55–3.59 m, 2H, H(8); l=3.35 s, 3H,
H(11).
13C-NMR: l=139.7 [1J(119Sn–13C)=489], C(i); l=
137.2 [2J(119Sn–13C)=35], C(o); l=129.1 [3J(119Sn–
13C)=47], C(m); l=129.4 [4J(119Sn–13C)=11], C(p);
l=7.7 [1J(119Sn–13C)=400], C(1); l=27.2 [2J(119Sn–
13C)=21], C(2); l=74.7 [3J(119Sn–13C)=64], C(3);
l=70.7, C(5); l=71.13, l=71.15, C(6) and C(8);
l=72.6, C(9); l=59.6, C(11).
Fig. 2. Molecular structure and crystallographic numbering scheme
employed for compound 4.
was continued until convergence. Final refinement de-
tails are given in Table 1 and the crystallographic
numbering scheme is shown in Fig. 2, which was drawn
at the 50% probability level [31].
117Sn-NMR: l= −100.3.
ESMS: M+Na+, 535; M+K+, 551.
2.3. Synthesis
Mo¨ssbauer: QS, 0.90 mm s−1; IS, 1.33 mm s−1
.
2.3.1. (4,7-Dioxaoctyl)triphenyltin
2.3.3. (4,7,10,13-Tetraoxatetradecyl)triphenyltin
4,7-Dioxaoctene was obtained as described previ-
ously [32]. Compound 1 (4,7-dioxaoctyl)triphenyltin,
was prepared by hydrostannation of the 4,7-
dioxaoctene (500 mg, 4.30 mmol) with triphenyltin
hydride (750 mg, 2.14 mmol) in the presence of AIBN
(45 mg, 0.27 mmol) [33]. The reaction was carried out
under nitrogen at 70 °C over 24 h. The resulting mix-
ture was extracted with petroleum ether and only the
filtrate was evaporated in vacuo. Purification was
achieved by column chromatography (silica/1: CH2Cl2;
2: CHCl3) and gave 1.6 g (3.42 mmol) of 1 as a
colorless oil (62%).
The synthesis and purification of (4,7,10,13-tetraox-
atetradecyl)triphenyltin (3), are as described for com-
pound 2 (60%).
Anal. Calc. for C28H36O4Sn: C, 60.56; H, 6.54.
Found: C, 59.8; H, 6.8%.
1H-NMR (CDCl3): l=7.49–7.57 m, 6H [2J(119Sn–
1H)=43], H(o); l=7.29–7.39 m, 9H, H(m) and H(p);
l=1.46–1.55 m, 2H [2J(119Sn–1H)=57], H(1); l=
1.93–2.07 m, 2H [3J(119Sn–1H)=58], H(2); l=3.40–
3.75 m, 14H, H(3), H(5), H(6), H(8), H(9), H(11) and
H(12); l=3.34 s, 3H, H(14).
13C-NMR: l=139.7 [1J(119Sn–13C)=489], C(i); l=
137.7 [2J(119Sn–13C)=35], C(o); l=129.1 [3J(119Sn–
13C)=47], C(m); l=129.4 [4J(119Sn–13C)=11], C(p);
l=7.8 [1J(119Sn–13C)=397], C(1); l=27.2 [2J(119Sn–
13C)=20], C(2); l=74.7 [3J(119Sn–13C)=64], C(3);
l=70.7, C(5); l=71.11, l=71.14, l=71.20, l=
71.25, C(6), C(8), C(10) and C(11); l=72.6, C(12);
l=59.6, C(14).
Anal. Calc. for C24H28O2Sn: C, 61.70; H, 6.05.
Found: C, 61.9; H, 5.9%.
1H-NMR (CDCl3): l=7.50–7.57 m, 6H [2J(119Sn–
1H)=46], H(o); l=7.30–7.38 m, 9H, H(m) and H(p);
l=1.46–1.55 m, 2H [2J(119Sn–1H)=57], H(1); l=
1.95–2.08 m, 2H [3J(119Sn–1H)=57], H(2); l=3.46 t
(7), 2H, H(3); l=3.40–3.44 m, 4H, H(5) and H(6);
l=3.32 s, 3H, H(8).
117Sn-NMR: l= −100.4.
13C-NMR: l=139.6 [1J(119Sn–13C)=489], C(i); l=
137.6 [2J(119Sn–13C)=35], C(o); l=129.0 [3J(119Sn–
13C)=48], C(m); l=129.4 [4J(119Sn–13C)=11], C(p);
l=7.7 [1J(119Sn–13C)=399], C(1); l=27.1 [2J(119Sn–
13C)=21], C(2); l=74.8 [3J(119Sn–13C)=67], C(3);
l=70.6, C(5); l=72.5, C(6); l=59.6, C(8).
117Sn-NMR: l= −100.3.
ESMS: M+NH+4 , 574; M+Na+, 579; M+K+,
594.
Mo¨ssbauer: QS, 0.00 mm s−1; IS, 1.53 mm s−1
.
2.3.4. (4,7-Dioxaoctyl)phenyldichlorostannane
(4,7-Dioxaoctyl)phenyldichlorostannane (4), was ob-
tained after treatment of 1 with anhydrous HCl at

58
M. Kemmer et al. / Journal of Organometallic Chemistry 634 (2001) 55–60
−78 °C in methylene chloride (95%). Crystals suitable
for X-ray analysis were grown in petroleum ether at
−10 °C (m.p. 49–50 °C).
Anal. Calc. for C12H18Cl2O2Sn: C, 37.55; H, 4.73.
Found: C, 37.4; H, 4.7%.
Of particular interest in the structure and relevant to
the solution studies reported below is the coordination
mode of the 4,7-dioxaoctyl ligand, which is tridentate,
forming a covalent interaction to tin via one of the
terminal carbon atoms as well as two coordinative
bonds to tin involving oxygen atoms. This mode of
coordination results in the formation of puckered
ꢀSnꢀCꢀCꢀCꢀOꢀ (the respective torsion angles for Sn–
C(1)–C(2)–C(3), Sn–O(1)–C(3)–C(2) and O(1)–C(3)–
C(2)–C(1) are −60.3(3), −21.4(2) and 52.1(3)°) and
ꢀSnꢀOꢀCꢀCꢀOꢀ five-membered rings (Sn–O(1)–C(4)–
C(5), Sn–O(2)–C(5)–C(4) and O(1)–C(4)–C(5)–O(2)
are −51.4(2), −28.1(3) and 52.9(3)°, respectively). It is
noted that while the SnꢀO bond distances of 2.553(2)
1H-NMR (CDCl3): l=7.76–7.82 m, 6H [2J(119Sn–
1H)=85], H(o); l=7.43–7.52 m, 9H, H(m) and H(p);
l=1.99 t (7), 2H [2J(119Sn–1H)=181], H(1); l=2.23
tt (6, 7), 2H [3J(119Sn–1H)=83], H(2); l=3.76 t (6),
2H, H(3); l=3.64 t (5), 2H, H(5); l=3.30 t (6), 2H,
H(6); l=3.14 s, 3H, H(8).
13C-NMR: l=141.6 [1J(119Sn–13C)=not visible],
C(i); l=135.1 [2J(119Sn–13C)=68], C(o); l=129.0
[3J(119Sn–13C)=87], C(m); l=130.7 [4J(119Sn–13C)=
18], C(p); l=22.6 [1J(119Sn–13C)=629], C(1); l=25.3
[2J(119Sn–13C)=40], C(2); l=70.8 [3J(119Sn–13C)=
20], C(3); l=70.4, C(5); l=71.1, C(6); l=58.6, C(8).
117Sn-NMR: l= −73.6.
,
and 2.540(2) A are longer than the sum of the covalent
,
radii of tin and oxygen (2.1 A), they are well within the
,
sum of their van der Waals radii (3.7 A) and hence,
these must be considered significant bonding interac-
tions. A small disparity in the SnꢀO distances is
reflected in a more significant disparity in the SnꢀCl
distances. Thus, the shorter SnꢀO(2) bond is trans to
the longer SnꢀCl(1) bond. There does not appear to be
any inherent chemical reason for these differences and
it is therefore argued that these arise as a result of intra-
and inter-molecular Sn···H interactions. The impor-
tance of such interactions in organotin chemistry has
been noted previously [6,34,35]. In the present case, the
Cl(1) atom that forms the longer SnꢀCl bond sits in a
pocket defined by four hydrogen atoms and forms a
relatively close intramolecular interaction. By contrast,
the Cl(2) atom forms a close intramolecular interaction
with a phenylꢀH and three weaker intermolecular
Cl···H interactions. There is no evidence for p···p inter-
actions in the crystal structure but there are interactions
of the type CꢀH···p.
ESMS: (C6H5)ClSnR+, 349.
Mo¨ssbauer: QS, 3.78 mm s−1; IS, 1.53 mm s−1
.
3. Results and discussion
3.1. Crystal structure of compound 4
The molecular strucure of 4 is illustrated in Fig. 2
and selected geometric parameters are collected in
Table 2. The tin atom is hexacoordinated, existing in a
C2Cl2O2 donor set. The disposition of the donor atoms
is such that the oxygen atoms occupy mutually cis
positions as do the chlorides, and the carbon atoms
occupy positions approximately trans to each other.
The trans angles, i.e. Cl(1)ꢀSnꢀO(2), Cl(2)ꢀSnꢀO(1) and
C(1)ꢀSnꢀC(7), of 171.61(4), 154.20(5) and 155.5(1)°,
respectively, indicate significant deviations from the
ideal geometry.
One of the C(5) methylene hydrogens is disposed so
as to lie over a symmetry related phenyl group. Thus,
,
the C(5)ꢀH(10) atom is separated by 2.76 A from the
Table 2
ring centroid of C(7)iꢀC(12)i and the angle subtended at
H(10) by C(5) and the ring centroid is 127°; symmetry
operation i: x, 1+y, z.
,
Geometric parameters (A, °) for compound 4
Bond distances
SnꢀCl(1)
SnꢀO(1)
SnꢀC(1)
O(1)ꢀC(3)
O(2)ꢀC(5)
2.468(1)
2.553(2)
2.129(3)
1.450(4)
1.440(3)
SnꢀCl(2)
SnꢀO(2)
SnꢀC(7)
O(1)ꢀC(4)
O(2)ꢀC(6)
2.407(1)
2.540(2)
2.124(3)
1.443(4)
1.431(4)
3.2. Solution structure of compound 4
The assignment of all 1H and 13C resonances was
1
Bond angles
achieved by 2D H–13C HMQC and HMBC experi-
Cl(1)ꢀSnꢀCl(2)
Cl(1)ꢀSnꢀO(2)
Cl(1)ꢀSnꢀC(7)
Cl(2)ꢀSnꢀO(2)
Cl(2)ꢀSnꢀC(7)
O(1)ꢀSnꢀC(1)
O(2)ꢀSnꢀC(1)
C(1)ꢀSnꢀC(7)
SnꢀO(1)ꢀC(4)
SnꢀO(2)ꢀC(5)
C(5)ꢀO(5)ꢀC(6)
99.58(3)
171.61(4)
94.40(7)
88.56(5)
100.42(7)
72.92(9)
87.14(9)
155.5(1)
110.8(1)
117.8(1)
110.8(2)
Cl(1)ꢀSnꢀO(1)
Cl(1)ꢀSnꢀC(1)
Cl(2)ꢀSnꢀO(1)
Cl(2)ꢀSnꢀC(1)
O(1)ꢀSnꢀO(2)
O(1)ꢀSnꢀC(7)
O(2)ꢀSnꢀC(7)
SnꢀO(1)ꢀC(3)
C(3)ꢀO(1)ꢀC(4)
SnꢀO(2)ꢀC(6)
105.76(4)
93.25(8)
154.20(5)
101.16(7)
66.35(6)
82.63(8)
82.00(8)
109.4(1)
113.7(2)
123.1(2)
ments in CDCl3 solution. The concentration indepen-
dent 117Sn chemical shift of compound 4 at −73.6 ppm
is rather different from a reference compound without a
Lewis donor, C6H5Cl2Sn(n-Bu) (+45 ppm), but is
fairly typical for a hypervalent diorganotin dichloride
[3]. Its alkyl 1J(119Sn–13C) coupling constants of 629 Hz
also reflect a stronger coordination at tin as compared
to C6H5Cl2Sn(n-Bu) (503 Hz). Compound 4 contains
two oxygen atoms potentially available for coordina-
tion to tin, as demonstrated in the crystalline state. In

M. Kemmer et al. / Journal of Organometallic Chemistry 634 (2001) 55–60
59
Since our 119Sn-NMR data are concentration inde-
pendent, intermolecular O“Sn interactions can rea-
sonably be excluded. The dynamic equilibrium of Fig. 3
is proposed for 4. Our results in solution confirm the
existence of intramolecular O“Sn interactions with,
however, a dynamic double cycle closing/opening mech-
1
anism which is fast on the H-, 13C-, and 117Sn-NMR
time scales. Only at the lowest temperature accessible,
163 K, the broad 117Sn resonance has started to decoa-
lesce into a major resonance at −106.2 ppm, charac-
teristic for five-coordination and a broader minor one
around −255 ppm characteristic for six-coordination.
This emphasizes that in solution, the thermal instability
of the long polyoxalkyl chain favors single rather than
double O“Sn complexation, unlike the crystal struc-
ture where the latter is favored.
3.3. Structure of compounds 1–3 in solution
The three compounds were characterized by 1H-,
13C-, and 117Sn-NMR in CDCl3 solution, including 2D
1H–13C HMQC and HMBC experiments. The 117Sn
chemical shift of 1 (−100.3 ppm) is temperature as
well as concentration independent and hardly differs
from the chemical shift found for (C6H5)3Sn(n-Bu)
Fig. 3. Dynamic equilibrium proposed for compound 4.
n
(−97.8 ppm). The J(119Sn–13C) coupling satellites are
order to ascertain whether only one or both oxygen
atoms are engaged in complexation to tin, we per-
likewise not very different from the reference com-
pound and display the usual open chain sequence
1
formed gradient assisted 1D H–119Sn HMQC NMR
1
3
2
ꢀ J(119Sn–13C)ꢀꢀꢀ J(119Sn–13C)ꢀ\ꢀ J(119Sn–13C)ꢀ [36].
experiments. The 1H resonances of all protons of 4
exhibit a 119Sn–1H correlation with the 119Sn nucleus,
1D H–119Sn HMQC NMR spectra reveal clear 119Sn–
1
1H correlations between the 119Sn nucleus and protons
H(1), H(2) and H(3) only. The latter is not an unequiv-
ocal indicator of a coordination between O(4) and Sn,
n
including H(5), H(6) and H(8). As J(119Sn–1H) cou-
plings are not observed above n=6 under the measure-
ment conditions used [24], it can be deduced that
6J(119Sn–1H), 7J(119Sn–1H) as well as 9J(119Sn–1H)
coupling constants through the 4,7-dioxaoctyl group
are merely to be understood as 3J(119Sn–1H) and
4J(119Sn–1H) coupling pathways involving coordinative
O“Sn bonds. On the basis of these results it can be
stressed that both oxygen atoms interact with the tin
atom.
because it may result either from a J(119Sn–1H) cou-
4
pling through the organic chain, from a J(119Sn–1H)
3
through the coordinative O(4)ꢀSn bond, or from both.
If it were to exist, the resulting five-coordinate species
has necessarily a very low molar fraction in the equi-
librium with the four-coordinate species since all other
NMR parameters essentially reflect four-coordination.
Moreover, this four-coordination favoring equilibrium
is fast on all NMR time scales.
n
In contrast to C6H5Cl2Sn(n-Bu), J(119Sn–13C) cou-
pling constants do not follow the general relationship
1
3
2
ꢀ J(119Sn–13C)ꢀꢀꢀ J(119Sn–13C)ꢀ\ꢀ J(119Sn–13C)ꢀ valid
for open chains [36]. Therefore, conformations of the
alkyl groups must necessarily be different for both
compounds.
4. Conclusions
Hexacoordination of the tin atom in CH3-
OCH2CH2OCH2CH2CH2SnCl3 in the solid state results
from two ether O“Sn interactions. In solution, a
dynamic equilibrium including intramolecular O“Sn
Furthermore, the 119Sn-NMR signal shifts to lower
frequency upon temperature decrease (l119Sn= −104
ppm at 183 K in CD2Cl2). A weak temperature depen-
1
dence is observed exclusively for the H chemical shift
interactions are observed. Even though
4
and
of H(8). These observations indicate that the interac-
tion involving the second oxygen of the 4,7-dioxaoctyl
chain is more labile and that the complexation equi-
librium at the latter oxygen is more favored at lower
temperatures, as might be expected.
CH3OCH2CH2OCH2CH2CH2SnCl3 differ only by one
substituent at the tin atom, their stereochemistry is
dramatically different both in the solid state and in
solution. Related with the lower Lewis acidity of te-
traorganotins, compounds 1–3 are tetracoordinated.

60
M. Kemmer et al. / Journal of Organometallic Chemistry 634 (2001) 55–60
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Crystallographic data for compound 4 have been
deposited with the Cambridge Crystallographic Data
Centre with deposition number CCDC 161858. Copies
of the information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
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We thank Engineer I. Verbruggen for recording the
NMR spectra, Professor Dr B. Mahieu for the Mo¨ss-
bauer spectra and Professor Dr G. Laus and M.
Desmet for the mass spectra. M.B., M.G. and R.W. are
indebted to the Fund for Scientific Research Flanders
(Belgium) (F.W.O.) for financial support (Grants
G.0192.98 (M.B., R.W.) and G.0074.00 (M.G.)). M.K.
thanks the ‘Ministe`re de l’Education Nationale du Lux-
embourg’ (Grants Nos. BFR93/052, BRU96/130,
BPU97/138, BPU98/071, BPU99/123) and the Action
‘Vaincre le Cancer du Luxembourg’. We are thankful
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