Bis[di-n-alkyl(fluoro)stannyl]methanes, (R2FSn) 2CH2 (R = n-octyl, n-dodecyl): Stable fluoride-selective carriers

Article abstract of DOI:10.1002/ejic.200300780

The synthesis of bis[di-n-alkyl(fluoro)stannyl]methanes, [(R ₂)FSn]₂CH₂, (3, R = n-octyl; 4, R = n-dodecyl), is reported and their unprecedented dimeric structure in solution with pentacoordinate tin atoms is rationalized on the basis of ¹⁹F and ¹¹⁹Sn NMR spectroscopy, osmometric molecular mass determination and electrospray mass spectrometry (ESMS). ¹⁹F and ¹¹⁹Sn MAS NMR and Moessbauer spectroscopy also indicate pentacoordinate tin atoms for the solid state. The ability of compounds 3 and 4 to bind fluoride ion selectively and reversibly is evaluated through potentiometric measurements. Compared with the previously reported organotin(iv)-based fluoride ionophore [Cl(Ph₂)Sn]₂CH₂, 3 and 4 exhibit a drastically improved lifetime, while retaining their high preference for fluoride over all other lipophilic anions evaluated. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200300780

FULL PAPER
Bis[di-n-alkyl(fluoro)stannyl]methanes, (R2FSn)2CH2 (R ؍ n-octyl, n-dodecyl):
Stable Fluoride-Selective Carriers
Nikolas Chaniotakis,*[a] Klaus Jurkschat,*[b] Dirk Müller,[c] Katerina Perdikaki,[a] and
Gregor Reeske[b]
Keywords: Tin / Fluorine / Anion carrier / NMR spectroscopy
The synthesis of bis[di-n-alkyl(fluoro)stannyl]methanes,
ability of compounds 3 and 4 to bind fluoride ion selectively
[(R2)FSn]2CH2, (3, R = n-octyl; 4, R = n-dodecyl), is reported and reversibly is evaluated through potentiometric measure-
and their unprecedented dimeric structure in solution with
pentacoordinate tin atoms is rationalized on the basis of 19F
and 119Sn NMR spectroscopy, osmometric molecular mass
ments. Compared with the previously reported organotin(IV)-
based fluoride ionophore [Cl(Ph2)Sn]2CH2, 3 and 4 exhibit a
drastically improved lifetime, while retaining their high pref-
determination and electrospray mass spectrometry (ESMS). erence for fluoride over all other lipophilic anions evaluated.
19F and 119Sn MAS NMR and Mössbauer spectroscopy also
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
indicate pentacoordinate tin atoms for the solid state. The Germany, 2004)
Introduction
peated use influences both the sensitivity (the slope of the
calibration curve expressed in mV per Ϫlog[anion] units)
and detection limit of the sensor. This signal drift could be
due to carrier decomposition, ligand exchange, or poison-
Various recent publications deal with the anion recog-
nition properties of organotin compounds. As shown,
mainly by variable-temperature NMR spectroscopy and
single-crystal X-ray diffraction analysis, open-chain as well
as cyclic bis(haloorganostannyl)alkanes function as bicen-
tric Lewis acids towards Lewis bases such as fluoride and
chloride ions[1Ϫ7]. The methylene-, dimethylene- and o-
phenylene-bridged ditin derivatives [Ph2(X)Sn]2CH2,[3]
ing due to the very strong binding to the primary ion[10]
.
Such signal drift is the only obstacle to the application and
commercialization of these ionophores in chemical sensors.
The origin of the carrier instability in the sensor membrane
is not completely understood, but is postulated to be hy-
drolysis for [Cl2(Ph)Sn]2CH2. Furthermore, with both
[Cl2(Ph)Sn]2CH2 and [Cl(Ph2)Sn]2CH2, chloride exchange
with other anions present in the solution to be analyzed
could occur. Additionally, the stability problem might
originate from anion-induced organic group migration[11]
and also from too low a lipophilicity of the carriers. Low
carrier lipophilicity facilitates leaching from the organic
phase, drastically influencing membrane characteristics.[12]
We present here the synthesis and structure of bis[di-n-
alkyl(fluoro)stannyl]methanes [F(R2)Sn]2CH2 (3, R ϭ n-oc-
tyl; 4, R ϭ n-dodecyl)) designed to overcome the above-
mentioned problems. Their higher lipophilicity, in combi-
nation with an improved membrane composition, gives an
optimal fluoride-selective electrode.
[1]
Ph2XSnCH2CH2SnXPh2,[4] and o-C6H4(SnXMe2)2 (X ϭ
F, Cl), respectively, preferably chelate fluoride over chloride
ions.
Moreover,
bis[chloro(diphenyl)stannyl]methane,
[Cl(Ph2)Sn]2CH2, and bis[dichloro(phenyl)stannyl]methane,
[Cl2(Ph)Sn]2CH2, when incorporated into polymeric-mem-
brane ion-selective electrodes, are highly selective carriers
for fluoride[8] and phosphate ions,[9] respectively. When
these carriers are used to develop chemical sensors, the ob-
served signal is unstable over prolonged periods, while re-
[a]
Laboratory of Analytical Chemistry, Department of Chemistry
University of Crete,
Crete, Greece
Fax: (internat.) ϩ 30-81-393601
E-mail: nchan@chemistry.uch.gr
[b]
Lehrstuhl für Anorganische Chemie II der Universität
Dortmund
Results and Discussion
44221 Dortmund, Germany
Fax: (internat.) ϩ 49-(0)231-7555048
E-mail: kjur@platon.chemie.uni-dortmund.de
klaus.jurkschat@uni-dortmund.de
Synthesis of the Title Compound and Its Structure in
Solution and in the Solid State
Bis[dibromo(phenyl)stannyl]methane, [Br2(Ph)Sn]2CH2,[13]
[c]
Institut für Angewandte Chemie Berlin-Adlershof e.V.
Richard-Willstätter Straße 12, 12489 Berlin, Germany
Fax: (internat.) ϩ 49-(0)30-63924165
E-mail: mueller dirk@aca-Berlin.de
and four equivalents of n-octylMgBr react to give bis[di-n-
Ϫ
Eur. J. Inorg. Chem. 2004, 2283Ϫ2288
DOI: 10.1002/ejic.200300780
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N. Chaniotakis, K. Jurkschat, D. Müller, K. Perdikaki, G. Reeske
The 19F and 119Sn NMR spectra of compound 4 are simi-
FULL PAPER
octyl(phenyl)stannyl]methane, [n-octyl2(Ph)Sn]2CH2 (1)
which was subsequently treated with iodine to provide bis- lar (see Exp. Sect.).
[iodo(di-n-octyl)stannyl]methane, [I(n-octyl)2Sn]2CH2 (2).
The 119Sn MAS NMR spectrum of 3 is dominated by
Reaction of the latter with excess of potassium fluoride then anisotropy of chemical shift interaction. The isotropic peak
gave bis[fluoro(di-n-octyl)stannyl]methane, [F(n-octyl)2Sn]2- shows a triplet at δ ϭ 2.4 ppm [ν1/2 325, J(119SnϪ19F) ϭ
CH2 (3) (Scheme 1). Bis[di-n-dodecyl(fluoro)stannyl]- 1270 Hz]. From the intensities of the corresponding triplet-
methane, [(n-dodecyl)2FSn]2CH2, (4), was prepared anal- shaped spinning side bands the main components of the
ogously.
shielding tensor were estimated to be δ ϭ 261.9, Ϫ113.0
and Ϫ141.7 ppm, respectively. The solid-state 19F NMR
spectrum recorded at a spinning rate of 30 kHz exhibits a
singlet at δ ϭ Ϫ142.1 ppm (ν1/2 150 Hz) with unresolved
J(19FϪ117/119Sn) satellites of 1272 Hz (satellite-to-signal-to-
satellite ratio 12.6:74:13.4). These spectroscopic data are
reasonably consistent with the polymeric structure (B)
shown in Figure 2, with, at least on the 19F and 119Sn time
scales, symmetric SnϪFϪSn bridges. This view is further
supported by the Mössbauer spectrum (I.S. 1.34 mm/s, Q.S.
3.69 mm/s), which unambiguously indicates pentacoordi-
nate tin atoms. Similar spectroscopic data have been re-
ported for dimethylphenyltin fluoride[14]
Scheme 1. Synthesis of bis[fluoro(di-n-octyl)stannyl]methane (3)
and bis[di-n-dodecyl(fluoro)stannyl]methane (4)
Compounds 3 and 4 were obtained as colorless amorph-
ous materials that are sparingly soluble in common organic
solvents such as CH2Cl2 and CHCl3. The 119Sn NMR spec-
trum at ambient temperature (CH2Cl2/D2Ocapillary) of com-
pound 3 reveals a doublet of doublet of doublets at δ ϭ
Figure 2. Polymeric structure of 3 in the solid state
3
38.8 ppm [1J(119SnϪ19F) 690, 1468, J(119SnϪ19F) 107 Hz].
The essentially concentration-independent 19F NMR spec-
trum (CDCl3) shows two triplet resonances of equal inte-
The 119Sn NMR spectrum of 3 at room temperature in
CD2Cl2 solution to which had been added one molar equiv-
alent of Bu4NF·2H2O shows a complex resonance (four
lines with different half widths) centered at δ ϭ Ϫ38 ppm,
which upon cooling to Ϫ80°C turns into a doublet of doub-
let of doublets at δ ϭ Ϫ32 ppm [1J(119SnϪ19F) 648, 1946,
3J(119SnϪ19F) 121 Hz]. These findings are consistent with
the formation of the organostannate complex 5 [Equa-
tion (1)].
gral ratio at Ϫ112.9 ppm [1J(19FϪ119/117Sn)
ϭ
683,
2J(19FϪ19F)
ϭ
71 Hz] and Ϫ157.2 ppm [1J(19FϪ
2
119/117Sn) ϭ 1474, J(19FϪ19F) ϭ 69 Hz]. The satellite-to-
signal-to-satellite integral ratio (15:70:15) for both reson-
ances indicates that each fluorine atom couples with two
117Sn and two 119Sn nuclei. Based on these spectroscopic
data and osmometric molecular weight determinations in
chloroform (1336 g/mol) and n-hexane (1493 g/mol) com-
pound 3 probably adopts the dimeric structure (A) (Fig-
ure 1) in solution. This is supported by the electrospray
mass spectrometric studies reported below.
The 119Sn NMR spectrum was unchanged upon addition
of a second molar equivalent of Bu4NF·2H2O. Compound
4 behaves analogously upon addition of one molar equiva-
lent of Bu4NF·2H2O [δ (119Sn) ϭ Ϫ40 ppm at room tem-
perature in CD2Cl2 solution, complex pattern with four
lines].
Figure 1. Dimeric structure of 3 in solution
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Eur. J. Inorg. Chem. 2004, 2283Ϫ2288

Bis[di-n-alkyl(fluoro)stannyl]methanes
FULL PAPER
Chloride ions can break the fluoride bridges in the A-
type dimer. Thus, the 119Sn NMR spectrum of 3 at room
temperature in CD2Cl2 solution to which had been added
one molar equivalent Ph4PCl shows a broad resonance at
δ ϭ Ϫ19 ppm that upon cooling to Ϫ20 °C turns into a
complex pattern centered at δ ϭ Ϫ20, which was not ana-
lyzed further.
The ESMS spectrum (negative mode) of a solution of
3 and Ph4PCl in acetonitrile shows the following mass
clusters with the expected isotopic patterns: {[F(n-
octyl)2Sn]2CH2·F}Ϫ (761.6), {[F(n-octyl)2Sn]2CH2·Cl}Ϫ
(777.5), {[Cl(n-octyl)2Sn]2CH2·F}Ϫ (793.6), [{[F(n-octyl)2-
Sn]2CH2}2·F]Ϫ (1502.7), and [{[F(n-octyl)2Sn]2CH2}2·Cl]Ϫ
(1520.3). The latter two support the dimeric structure (A)
(Figure 1) of compound 3 in solution (see above).
Potentiometric Studies
Figure 3. Calibration curves of the ISEs based on compounds 3
(solid triangle) and 4 (solid square) in aqueous solutions buffered
with MES to pH 5.5
Bis[fluoro(di-n-octyl)stannyl]methane, [F(n-octyl)2Sn]2-
CH2, (3), and bis[di-n-dodecyl(fluoro)stannyl]methane, [(n-
dodecyl)2FSn]2CH2, (4), were used to develop a solvent
polymeric membrane electrode that was examined for its
selectivity and sensitivity (slope) to fluoride. The results
are compared with previously obtained potentiometric
data based on bis[chloro(diphenyl)stannyl]methane,
[Cl(Ph2)Sn]2CH2.[8] Compounds 3 and 4 are more lipophilic
than [Cl(Ph2)Sn]2CH2 and do not favor halide exchange.
Therefore, they are expected not only to preserve the excel-
lent fluoride selectivity obtained with the [Cl(Ph2)Sn]2CH2-
based system, but also to exhibit a considerably longer life-
time within the organic membrane layer.
phase of the sensor.[18,19] This stoichiometry was not ob-
served in the NMR titrations performed in CD2Cl2.
Ionophore Stability Studies: A very important character-
istic of an ionophore is its stability (chemical and struc-
tural) over time under operational conditions, which can
be very well studied using potentiometry. The interfacial
potential generated due to the ability of the carrier to com-
plex the ion under investigation is directly related to the
state of the ionophore. Any signal drift, loss in sensitivity
or selectivity is thus a measure of the ionophore’s instability.
Therefore, the sensitivity of ISEs based on carriers 3 and 4
was monitored for a period of 40 days. Figure 4 shows that
the sensitivity of the membrane to fluoride remained practi-
cally unchanged for over 20 days of continuous use, the
slope remaining above 50 mV/Ϫlog[FϪ].
Potentiometric Response
The potentiometric response of a liquid polymeric mem-
brane doped with an ion carrier provides direct evidence of
the interaction of the carrier with the ions in solution.
Based on these data, one can determine the selectivity, the
binding constant in the organic phase, the reversibility and
the stability of the ionophoreϪanion complex. Thus, the
overall potentiometric response (∆E), the calibration curve,
and the base line return and stability of the electrodes based
on carriers 3 and 4, were monitored and analyzed. Figure 3
shows the potential changes observed and the resulting cali-
bration curve of the ion-selective electrodes (ISEs).
Figure 3 shows that the two sensors have different ana-
lytical characteristics. The slope of the calibration curves
for the ISEs based on carriers 3 and 4 are Ϫ87.8 and Ϫ68.2
mV/Ϫlog[FϪ], respectively. Carrier 3 with the octyl sub-
stituents shows a higher sensitivity to fluoride anion, indi-
cating that the organic substituents R have little influence
on the coordination of the carrier to fluoride. The slope to
fluoride of both carriers is higher than can be explained by
the Nernst theory, according to which the sensitivity for
monovalent anions such as fluoride is Ϫ59.16 mV/
Ϫlog[anion]. The high sensitivity of organometallic carriers
to anions observed previously [15Ϫ17] is suggested to be con-
nected with a less than one-to-one complex formed between
Figure 4. Stability of the ISE1 and ISE2 sensors, based on carriers
3 (solid triangle) and 4 (solid square), respectively, according to the
sensitivity of the sensor over time under continuous monitoring in
the carrier and the primary ion in the polymeric membrane MES (buffered to pH 5.5)
Eur. J. Inorg. Chem. 2004, 2283Ϫ2288
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N. Chaniotakis, K. Jurkschat, D. Müller, K. Perdikaki, G. Reeske
FULL PAPER
pot
The effect is even more obvious when the more lipophilic
dodecyl-substituted carrier (carrier 4) is used. This is a large
improvement when compared with the previously reported
carrier [(ClPh2Sn)2CH2] which showed a lifetime of not
longer than 4 days.
Ionophore Selectivity: The selectivity of the ionophore
was studied using the overall potentiometric response of the
membrane between a solution of plain buffer, and that con-
taining 0.01  of the salt under study. Figure 5 shows the
overall potentiometric response (in ∆E) of sensors based on
Table 1. Potentiometric selectivity coefficients K of the ISE based
on carrier 3.
F,J
Anion
log Kpot
Ϫ
NO3
Ϫ1.9
Ϫ1.0
0.0
Ϫ1
Ϫ0.1
0.8
ClϪ
FϪ
Ϫ
ClO4
IϪ
SCNϪ
carriers 3 and 4. Based on these data, the logarithms of the
pot
potentiometric selectivity coefficients log K
were deter-
F,J
pot
Table 2. Potentiometric selectivity coefficients K of the ISE based
on carrier 4
F,J
mined according to the NikolskiiϪEisenman equation
(Equation 2) (Table 1 and 2).
Anion
log Kpot
(2)
Ϫ
NO3
Ϫ1.6
Ϫ1.3
0.0
Ϫ1.2
Ϫ0.9
Ϫ0.4
ClϪ
FϪ
Ϫ
EM is the membrane potential in mV, ai the activity (con-
centration) of the primary ion, aj the activity of the interfer-
ing ion and zi and zj the charge of the primary and interfer-
ClO4
IϪ
SCNϪ
ing ions, respectively. Negative potentiometric selectivity co-
pot
efficients K indicate that the ISE is more selective to the
F,J
primary ion (fluoride in this study), whereas positive values
indicate that the ISE is more selective to the interfering ion.
The selectivity order based on the overall potentiometric
response in a MES-buffered solution at pH 5.5 for both
ISEs is similar, FϪ ഠ SCNϪ Ͼ IϪ Ͼ ClO4Ϫ Ͼ ClϪ Ͼ NO3.
For comparison, the classical Hofmeister selectivity order
Ϫ
for a quaternary ammonium ion-based sensor is ClO4
Ͼ
Ϫ
SCNϪ Ͼ IϪ Ͼ NO3 Ͼ ClϪ Ͼ FϪ.
Evidently, from the overall potentiometric response and
the calculated selectivity coefficients, the fluoride ion is pre-
ferred over several other more lipophilic ions, such as per-
chlorate, nitrate, and iodide. The anti-Hofmeister selectivity
sequence obtained for 3 and 4 is closely related to that ob-
tained for the less stable ionophore [Cl(Ph2)Sn]2CH2.[8]
These results clearly show that, even though the sensor
based on ionophore 3 has a good sensitivity and selectivity
for fluoride, an improved sensor in terms of selectivity and
stability over time is produced when the membrane is doped
with ionophore 4.
Conclusion
The stability of previously evaluated highly selective flu-
oride carriers can be drastically improved by the use of lipo-
philic organic substituents. The closely related carriers
(FR2Sn)2CH2 (3, R ϭ n-octyl; 4, R ϭ n-dodecyl) and the
previously reported [Cl(Ph2)Sn]2CH2 are compared for their
fluoride selectivity and their ability to develop stable fluor-
ide-selective electrodes. Based on spectroscopic studies, in
organic phases these carriers form a reversible one-to-one
complex with fluoride anions. Furthermore, the stability of
the sensors depends on the lipophilicity of the carrier, which
in turn can be controlled by the organic substituents at-
tached to the tin atoms. However, the selectivity is not influ-
Figure 5. Overall potentiometric response of the ISEs based on
carriers 3 (A) and 4 (B) towards several anions at pH 5.5 (MES,
0.001 )
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Bis[di-n-alkyl(fluoro)stannyl]methanes
FULL PAPER
suming that the electrode shows a theoretical slope of Ϫ59.16 mV
for monovalent anions.
enced drastically, allowing the development of a robust and
highly selective liquid polymeric fluoride-selective electrode.
This result will be useful in improving the stability and life-
time of other ionophores that are highly selective for anions
such as phosphate and chloride.
Synthesis
of
Bis[di-n-octyl(phenyl)stannyl]methane,
[(n-oc-
tyl)2(Ph)Sn]2CH2 (1): A solution of n-octylmagnesium bromide pre-
pared from n-octyl bromide (5.01 g, 25.9 mmol) and magnesium
(0.63 g, 25.9 mmol) in THF (50 mL) was added to a solution of
bis[dibromo(phenyl)stannyl]methane[13] (4.70 g, 6.48 mmol) in
THF (150 mL). After stirring at room temperature (4 h) the re-
sulting mixture was hydrolyzed with water (50 mL). The organic
layer was then separated, dried with Na2SO4 and filtered. Evapor-
ation of the solvent gave 3.9 g (70% yield) of bis[di-n-octyl(phenyl)-
stannyl]methane (1) as a colorless oil. 1H NMR (500.13 MHz,
CDCl3, 300 K): δ ϭ 0.12 [s, 2J(1H-119Sn) ϭ 57.4 Hz, 2 H,
SnϪCH2ϪSn], 0.92 [t, 2J(1H-1H) ϭ 7 Hz, 12 H, ϪCH3], 0.99Ϫ1.63
[m, J ϭ 56 Hz, ϪCH2Ϫ], 7.26Ϫ7.55 [m, 10 H, SnϪPh] ppm.
13C{1H} NMR (125.77 MHz, CDCl3 300 K): δ ϭ Ϫ19.5 [1J(13C-
117Sn) ϭ 226.9, 1J(13C-119Sn) ϭ 236.7 Hz, SnϪCH2ϪSn], 11.67
[1J(13C-117Sn) ϭ 337.2, 1J(13C-119Sn) ϭ 253.3 Hz, C-1], 14.12 (C-
Experimental Section
General Remarks: All manipulations were performed under nitro-
gen using standard Schlenk and vacuum line techniques. Solvents
were distilled from the appropriate desiccants prior to use. Litera-
ture procedures were used to prepare bis[dibromo(phenyl)stannyl]-
[13]
methane, [Br2(Ph)Sn]2CH2.
NMR spectra were recorded in
CDCl3 using a spectrometer at 500.13 (1H), 100.63 (13C) 182.36
(19F), 111.92 and 149.21 (119Sn) MHz. Chemical shifts (δ ppm)
were referenced to Me4Sn (119Sn), CFCl3 (19F) and Me4Si (13C,
1H). 119Sn MAS NMR spectra were recorded with a Varian Unity-
plus 500 spectrometer at 186.40 MHz using a Doty supersonic CP/
MAS probe (rotor diameter 5 mm) with a 10 kHz spinning rate.
The corresponding 19F MAS NMR spectra were recorded with a
Bruker Avance 400 spectrometer at 376.52 MHz using rotors of
2.5 mm diameter with spinning rates of up to 32 kHz. Elemental
analyses were performed with an instrument from Carlo Erba In-
strumentation (model 1106). Molecular weight determinations
were carried out with a Knauer Dampfdruck-Osmometer K-7000.
The calibration standard was Polystyrene 2000 (Fluka) with n-hex-
ane and chloroform as solvents.
8), 22.71 (C-7), 26.82 [2J(13C-117/119Sn)
ϭ 20.1 Hz, C-2],
29.18Ϫ29.73 (C-4, C-5), 31.96 (C-6), 34.44 [3J(13C-117/119Sn) ϭ
59.4 Hz, C-3], 127.93 [3J(13C-117/119Sn) ϭ 41.8 Hz, Cm], 12810 [Cp],
136.24 [2J(13C-117/119Sn)
ϭ 32.7 Hz, Co], 142.92 [Ci] ppm.
119Sn{1H} NMR (149.21 MHz, CDCl3): δ ϭ Ϫ16.5 [2J117Sn-
119Sn) ϭ 239 Hz] ppm. C45H80Sn2 (858.5): calcd. C 63.0, H 9.4;
found C 63.7, H 9.9.
Synthesis of Bis[iodo(di-n-octyl)stannyl]methane, [I(n-octyl)2-
Sn]2CH2 (2): Iodine (3.61 g, 10.22 mmol) was added in small por-
tions under ice-cooling to a stirred solution of 1 (6.10 g, 7.11 mmol)
in CH2Cl2 (50 mL). The reaction mixture was then stirred over-
night, after which the solvent and the iodobenzene were removed
in vacuo. Addition of CH2Cl2 (20 mL), filtration and evaporation
of the solvent then afforded 6.4 g (94% yield) bis[iodo(di-n-octyl)-
Electrochemical Studies: Instrumentation: Potentiometric measure-
ments were performed with a XENON CI-317 8-channel elec-
trometer (Halandri, Athens, Greece) versus an Orion Research (Be-
verly, MA, USA) 900200 double junction reference electrode. Data
were collected with a personal computer program written in BASIC
for storage and further analysis.
1
stannyl]methane (2) as a light yellow oil. H NMR (500.13 MHz,
CDCl3, 300 K): δ ϭ 0.87 [t, 2J(1H-1H) ϭ 7 Hz, 12 H, ϪCH3],
1.19Ϫ1.65 (m, 56 H, ϪCH2Ϫ] ppm. 13C{1H} NMR (125.77 MHz,
CDCl3 300 K): δ ϭ Ϫ3.01 [SnϪCH2ϪSn], 14.09 (C-8), 19.45
[1J(13C-117Sn) ϭ 334.0, 1J(13C-119Sn) ϭ 349.3 Hz, C-1], 22.63 (C-
7), 26.83 [2J(13C-117/119Sn) ϭ 25.9 Hz, C-2], 28.90Ϫ29.18 [C-4ϪC-
5], 31.84 (C-6), 33.44 [3J(13C-117/119Sn) ϭ 70.1 Hz, C-3] ppm.
Reagents: High purity potassium salts (p.a. Fluka, p.a. Merck)
were used for the preparation of electrolyte solutions. 2-Morpholin-
oethanesulfonic acid (MES) (Merck) was used as the pH buffer.
The membranes were constructed from poly(vinyl chloride) (PVC)
(high molecular weight, Selectophore, Fluka), as membrane matrix,
bis(2-ethylhexyl) sebacate (DOS) (Selectophore, Fluka) as plas-
ticizer, and tetrahydrofuran (THF) (p.a. Merck), doubly distilled
before use, as membrane solvent.
119Sn{1H} NMR (111.92 MHz, CDCl3):
δ
ϭ
87.3 ppm.
C33H70I2Sn2 (958.14): calcd. C 41.4, H 7.4; found C 42.0, H 7.5.
Synthesis of Bis[fluoro(di-n-octyl)stannyl]methane, [F(n-octyl)2-
Sn]2CH2 (3): A solution of bis[iodo(di-n-octyl)stannyl]methane
(5 g, 5.23 mmol) in diethyl ether (50 mL) was poured into a solu-
tion of potassium fluoride (2.98 g, 52.2 mmol) in water (50 mL).
The resultant mixture was stirred for 24 h, and then the organic
layer was separated, washed with water (2 ϫ 50 mL), filtered and
dried with sodium sulfate. After removing the solvent, the remain-
ing residue was washed with dichloromethane (20 mL), filtered and
dried in vacuo to give 2.3 g (60%) of compound 3. 1H NMR
(400.13 MHz, CDCl3): δ ϭ 0.87 [t, 2J(1H-1H) ϭ 7 Hz, 24 H,
ϪCH3], 1.05Ϫ1.65 [m, 14 H, ϪCH2Ϫ] ppm. 13C{1H} NMR
(100.62 MHz, CDCl3): δ ϭ 14.12 (C-8), 20.23 (t, C-1), 22.72 (C-7),
25.53 [2J(13C-117/119Sn) ϭ 26.2 Hz, C-2], 29.32Ϫ29.44 (C-4, C-5),
31.99 (C-6), 34.14 [3J(13C-117/119Sn) ϭ 80.7 Hz, C-3] ppm. 19F{1H}
NMR (282.36 MHz, CDCl3): δ ϭ Ϫ115.1 [t, 2J(19F-19F) ϭ 71.2,
1J(19F-119Sn) ϭ 686.6 Hz], Ϫ159.3 [2J(19F-19F) ϭ 68.9, 1J(19F-
Membrane preparation: All the membranes examined had the fol-
lowing composition: 2% carrier, 33% PVC and 65% DOS. The mix-
ture of components (100 mg) was dissolved in THF (ca. 1.5 mL),
and the resultant solution was poured into a glass ring (i.d. 17 mm),
the latter being placed on a glass plate. Membranes were formed
after solvent evaporation. Circular pieces (diameter 7 mm) of the
membranes were cut off and mounted for testing on type IS 561
Phillips electrode bodies (from Willi Möller AG, Glasbläserei,
Zürich, Switzerland). The internal solution of the electrode was
0.01  KCl.
Selectivity measurements and calibration curves: All electrodes
were tested without prior pretreatment, except when specifically
mentioned. All electrolyte solutions were 10Ϫ2, and buffered with
MES 10Ϫ3  (pH ϭ 5.5). The potential was monitored and the
potential difference recorded when the readings were stable in
either the calibrating or test solutions. The selectivity coefficients 119Sn) ϭ 1472.0 Hz] ppm. 119Sn{1H} NMR (149.21 MHz, CH2Cl2,
1
1
were determined by the separate solution method (SSM)[20], as-
D2Ocapillary): δ ϭ 38.1 [ddd, J(19F-119Sn) ϭ 1468, J(19F-119Sn) ϭ
Eur. J. Inorg. Chem. 2004, 2283Ϫ2288
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2287

N. Chaniotakis, K. Jurkschat, D. Müller, K. Perdikaki, G. Reeske
FULL PAPER
690, J(19F-119Sn) ϭ 107 Hz] ppm. C33H70F2Sn2 (742.33): calcd. C
3
[1]
R. Altmann, K. Jurkschat, M. Schürmann, D. Dakternieks, A.
53.4, H 9.5; found C 53.2, H 9.6.
Duthie, Organometallics 1998, 17, 5858Ϫ5866.
R. Altmann, O. Gausset, D. Horn, K. Jurkschat, M.
[2]
Synthesis of Bis[di-n-dodecyl(fluoro)stannyl]methane, [(n-dode-
cyl)2FSn]2CH2 (4): Compound 4 was prepared by a procedure anal-
ogous to that for 3. Thus, bis[dibromo(phenyl)stannyl]methane
(9.4 g, 13.0 mmol) was reacted with the Grignard reagent made
from 1-dodecyl bromide (1.34 g, 56.0 mmol) and magnesium turn-
ings to give bis[di-n-dodecyl(phenyl)stannyl]methane (7.4 g, 53%)
as a viscous oil (119Sn{1H} NMR (111.92 MHz, CDCl3): δ ϭ
Ϫ15.1), which was used for the subsequent reaction without further
purification. Treatment of bis[di-n-dodecyl(phenyl)stannyl]methane
(6.40 g, 5.9 mmol) with iodine (3.00 g, 11.8 mmol) gave bis[iodo(di-
n-dodecyl)stannyl]methane (6.9 g, 93%) as a slightly yellow oil
Schürmann, M. Fontani, P. Zanello, Organometallics 2000,
17, 430Ϫ443.
[3]
D. Dakternieks, K. Jurkschat, H. Zhu, T. Tiekink, Organomet-
allics 1995, 14, 2512Ϫ2521.
K. Jurkschat, F. Hesselbarth, M. Dargatz, J. Lehmann, E. Kle-
inpeter, A. Tzschach, J. Meunier-Piret, J. Org. Chem. 1990,
381, 259Ϫ271.
K. Jurkschat, H. G. Kuivila, S. Liu, J. A. Zubieta, Organomet-
allics 1989, 8, 2755Ϫ2759.
K. Jurkschat, A. Rühlemann, A. Tzschach, J. Organomet.
Chem. 1990, 381, C53ϪC56.
M. Schulte, M. Schürmann, K. Jurkschat, Chem. Eur. J. 2001,
7, 347Ϫ355.
[4]
[5]
[6]
[7]
(
119Sn{1H} NMR (111.92 MHz, CDCl3): δ ϭ 85.8 ppm) that was
used without further purification for the subsequent reaction.
[8]
K. Perdikaki, I. Tsagatakis, N. A. Chaniotakis, R. Altmann,
K. Jurkschat, G. Reeske, Anal. Chim. Acta 2002, 467, 197Ϫ204.
J. K. Tsagatakis, N. A. Chaniotakis, K. Jurkschat, Helv. Chim.
A
solution of bis[iodo(di-n-dodecyl)stannyl]methane (1.67,
[9]
1.4 mmol) in diethyl ether (30 mL) was added to a solution of pot-
assium fluoride (0.82, 14.1 mmol) in water (20 mL). The mixture
was then stirred for 24 h followed by the workup procedure de-
scribed for compound 3 to give bis[di-n-dodecyl(fluoro)stannyl]me-
thane (1.07 g, 79%) as a colorless amorphous solid. 1H NMR
(400.13 MHz, CDCl3): δ ϭ 0.86 [t, 2J(1H-1H) ϭ 6 Hz, 12 H,
ϪCH3], 1.05Ϫ1.65 [m, 84 H, ϪCH2Ϫ] ppm. 13C{1H} NMR
(100.62 MHz, CDCl3): δ ϭ 14.12 (C-12), 20.26 (t, C-1), 22.72 (C-
11), 25.54 [2J(13C-117/119Sn) ϭ 26.2 Hz, C-2], 29.36Ϫ29.45 (C-4ϪC-
9), 31.97 (C-10), 34.15 [3J(13C-117/119Sn) ϭ 80.2 Hz, C-3] ppm.
19F{1H} NMR (282.36 MHz, CDCl3): δ ϭ Ϫ115.0 [t, 2J(19F-19F) ϭ
68.8, 1J(19F-119Sn) ϭ 686.6 Hz], Ϫ159.3 [t, 2J(19F-19F) ϭ 66.6,
1J(19F-119Sn) ϭ 1479.1 Hz] ppm. 119Sn{1H} NMR (149.21 MHz,
Acta 1994, 77, 2191Ϫ2196.
I. Tsagatakis, N. A. Chaniotakis, R. Altmann, K. Jurkschat,
R. Willem, J. C. Martins, Y. Quin, E. Bakker, Helv. Chim. Acta
2001, 84, 1952Ϫ1961.
D. Dakternieks, H. J. Zhu, Organometallics 1992, 11,
3820Ϫ3825.
O. Dinten, U. E. Spichiger, N. A. Chaniotakis, P. Gehrig, B.
Rusterholz, W. E. Morf, W. Simon, Anal. Chem. 1991, 63,
596Ϫ603.
M. Gielen, K. Jurkschat, J. Organomet. Chem. 1984, 273,
303Ϫ312.
J. Beckmann, D. Horn, K. Jurkschat, F. Rosche, M.
Schürmann, U. Zachwieja, D. Dakternieks, A. Duthie, A. E.
K. Lim, Eur. J. Inorg. Chem. 2003, 164Ϫ174.
K. Perdikaki, J. K. Tsagatakis, N. A. Chaniotakis, Mikrochim.
Acta 2001, 136, 217Ϫ221.
[10]
[11]
[12]
[13]
[14]
1
1
CH2Cl2, D2Ocapillary) δ ϭ 38.2 [ddd, J(19F-119Sn) ϭ 1466, J(19F-
119Sn) ϭ 688, 3J(19F-119Sn) ϭ 105 Hz]. C49H102F2Sn2 (965.9): calcd.
C 59.9, H 10.5; found C 59.5, H 10.6.
[15]
[16]
U. Wuthier, H. V. Pham, E. Pretsch, D. Ammann, A. K. Beck,
D. Seebach, W. Simon, Helv. Chim. Acta 1985, 68, 1822Ϫ1826.
M. L. Lehaire, R. Scopelliti, H. Piotrowski, K. Severin, Angew.
[17]
Chem. Int. Ed. 2002, 41, 1419Ϫ1422.
U. Schaller, E. Bakker, U. E. Spichiger, E. Pretsch, Anal. Chem.
1994, 66, 391Ϫ398.
S. Amemiya, P. Bühlmann, E. Pretsch, B. Rusterholz, Y. Umez-
awa, Anal. Chem. 2000, 72, 1618Ϫ1631.
G. G. Guilbault, R. A. Durst, M. S. Frant, H. Freiser, E. H.
Hansen, T. S. Light, E. Pungor, G. Rechnitz, N. M. Rice, T. J.
Rom, W. Simon, J. D. R. Thomas, Pure Appl. Chem. 1976,
48, 127Ϫ131.
[18]
Acknowledgments
K. J., G. R., and D. M. thank the Deutsche Forschungsgemein-
schaft for financial support. N. C. and K. P. thank Professor Eurip-
ides Stefanou for the coordination of the program YPER Ј97 and
the States Scholarship Foundation of Greece (97 YPER 174) for
financial support. We are grateful to Dr. B. Mahieu, Louvain-la-
Neuve, Belgium, for recording the Mössbauer spectrum of com-
pound 3 and to Dr. D. Heidemann, Humboldt-Universität Berlin,
for recording the 19F MAS NMR spectrum. This work includes
parts of the intended Ph.D. thesis of G. Reeske.
[19]
[20]
Received October 24, 2003
Early View Article
Published Online April 7, 2004
2288
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Eur. J. Inorg. Chem. 2004, 2283Ϫ2288