Synthesis, structure and reactivity of hydrated and dehydrated organotin cations

Article abstract of DOI:10.1002/ejic.200600468

Monomeric organotin dications {[nBu₂Sn(H₂O) ₄]²⁺· 2C₆H₅SO ₃^-} and {[nBu₂Sn(H₂O) ₄]²⁺·1,5-C₁₀H₆(SO ₃^-)₂} have been synthesized by the reaction of [nBu₂SnO]_n and the corresponding arylsulfonic acid. Dodecanuclear organooxotin macrocations {[(nBuSn)₁₂(μ₃- O)₁₄(μ₂-OH)₆]²⁺·2RSO ₃^-} (R = C₆H₅; 2,5-Me ₂C₆H₃) have been synthesized by the reaction of nBuSn(O)(OH) and the corresponding arylsulfonic acid. The X-ray crystal structure of one of the dodecanuclear cages is reported. These organotin cations have been shown to be effective catalysts in acetylation and transacetylation reactions. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600468

FULL PAPER
DOI: 10.1002/ejic.200600468
Synthesis, Structure and Reactivity of Hydrated and Dehydrated Organotin
Cations
Vadapalli Chandrasekhar,*[a] Ramamoorthy Boomishankar,[a] Kandasamy Gopal,[a]
Palani Sasikumar,[a] Puja Singh,[a] Alexander Steiner,[b] and Stefano Zacchini[b]
Keywords: Organotin cations / Organooxotin / Organostannoxane / Acetylation / Transacetylation
Monomeric
organotin
dications
{[nBu2Sn(H2O)4]2+
·
The X-ray crystal structure of one of the dodecanuclear cages
is reported. These organotin cations have been shown to be
2C6H5SO3–} and {[nBu2Sn(H2O)4]2+·1,5-C10H6(SO3–)2} have
been synthesized by the reaction of [nBu2SnO]n and the cor- effective catalysts in acetylation and transacetylation reac-
responding arylsulfonic acid. Dodecanuclear organooxotin
tions.
–
macrocations {[(nBuSn)12(µ3-O)14(µ2-OH)6]2+·2RSO3
} (R =
C6H5; 2,5-Me2C6H3) have been synthesized by the reaction
of nBuSn(O)(OH) and the corresponding arylsulfonic acid.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
compounds in esterification and transesterification reac-
tions we have explored the catalytic activity of 1–6 towards
acetylation of alcohols and phenols.
Introduction
Organotin oxides [(R3Sn)2O; (R2SnO)n], hydroxides
[R3SnOH] and oxide hydroxides [{RSn(O)OH}n] are impor-
tant precursors for the synthesis of a large number of or-
ganotin compounds.[1] These precursors are the eventual
hydrolysis products of the corresponding organotin halides.
Initial hydrolysis of organotin halides leads to the forma-
tion of hydrated organotin cations.[2] Inspite of their appar-
ent simplicity there have been very few reports on the isola-
tion of such species in the solid state.[3] In most cases, dehy-
drated hydroxide-bridged compounds[4a] or oxo-bridged
ladders[4b] are the products. In preliminary communications
we have recently reported that arylsulfonic acids are effec-
Results and Discussion
Synthesis of Organotin Cations
The synthesis of the organotin cations has been ac-
complished in high yields by the reaction of an organotin
oxide with an arylsulfonic acid. The work-up of the reac-
tion mixture and subsequent crystallization in open air al-
lows the isolation of the compounds 1–4. All of these or-
ganotin cations are air-stable solids. Compounds 3 and 4
are prepared by a reaction of the polymeric [nBu2SnO]n
with the corresponding sulfonic acids (Scheme 1). This pro-
cedure is similar to that reported by us recently for the syn-
thesis of 1 (Scheme 1).[5a] Compound 2, which contains two
tin units bridged by a disulfonate, is synthesized by the deal-
kylation reaction involving a 1:1 reaction of (nBu3Sn)2O
with naphthalene-1,5-disulfonic acid.[5b] The dodecanuclear
organooxotin cages 5 and 6 are assembled by the reaction
of n-butylstannonic acid, nBuSn(O)(OH) with the corre-
sponding sulfonic acids (Scheme 2).[6]
–
tive in stabilizing {[nBu2Sn(H2O)4]2+·2 2,5-Me2C6H3SO3 }
(1)[5a] and {[nBu2Sn(H2O)3]2[µ-1,5-C10H6(SO3)2]}2+·1,5-
–
C10H6(SO3 )2 (2).[5b] Herein we report the general applica-
bility of this synthetic procedure. Accordingly, the hydrated
organotin cations, {[nBu2Sn(H2O)4]2+·[xY]2–}, where x = 2,
Y = C6H5SO3 (3); x = 1, Y = 1,5-C10H6(SO3)2 (4) have been
prepared and characterized. Attempts to prepare hydrated
monoorganotin cations resulted in the macromeric dodeca-
nuclear organooxotin cages (foot-ball cages), {[(nBuSn)12-
–
(µ3-O)14(µ2-OH)6]2+·2RSO3 }, where R = C6H5 (5); 2,5-
Me2C6H3 (6). The X-ray crystal structure of 6 is reported
and compared with other members of this structural type.
In view of the interest in neutral and cationic organotin
Solution Studies
[a] Department of Chemistry, Indian Institute of Technology,
Kanpur,
All of these compounds have been characterized by ana-
lytical and spectroscopic techniques (see experimental sec-
tion). Consistent with the above formulation; conductivity
studies on 3 and 4 revealed that these compounds are 1:2
electrolytes. While the specific and molar conductivities of
3 are 1811 µScm–1 and 300 Scm2 mol–1 (3 mmol/L in
Kanpur 208 016, India
Fax: +91-512-2590007 / 2597436
E-mail: vc@iitk.ac.in
[b] The Donnan and Robinson Laboratories, Department of
Chemistry, University of Liverpool,
Liverpool L697ZD, U.K.
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V. Chandrasekhar et al.
FULL PAPER
Scheme 1. Synthesis of diorganotin cations 1–4. (i) 2 2,5-Me2C6H3SO3H, toluene, reflux, 8 h. (ii) 2 C6H5SO3H, toluene, reflux, 8 h. (iii)
1,5-C10H6(SO3H)2, toluene, reflux, 8 h. (iv) 2 1,5-C10H6(SO3H)2, toluene, reflux, 6 h.
Scheme 2. Synthesis of monoorganotin macrocations 5 and 6. (i) toluene, reflux, 72 h.
CH3OH), 4 has a specific conductivity of 898 µScm–1 and a
The solution ionic conductivity measurement on 2 shows
molar conductivity of 150 Scm2 mol–1 (3 mmol/L in DMF) that the observed specific and molar conductivities are
(Table 1). The increased ionic conductivity of 3 when com- 2257 µScm–1 and 376 Scm2 mol–1 (3 mmol/L in CH3OH),
pared to 1 [specific conductivity 946 µScm–1; molar con- respectively. These values suggest that in solution 2 does
ductivity 158 Scm2 mol–1 (3 mmol/L in CH3OH)][5a] and 4 not exist as a 1:2 electrolyte but presumably undergoes an
is attributed to the increased acidic nature of 3 which arises unsymmetrical disproportionation of the tin–sulfonate oxy-
due to the benzenesulfonate ligand. The 119Sn NMR spec- gen bond and thereby producing different kinds of cationic
tra of 3 and 4 show a single resonance at –360.6 and species. Support for such a hypothesis also comes from the
–384.9 ppm, respectively (Table 1), which are comparable to 119Sn NMR chemical shifts of the compound 2. 119Sn
that observed for 1 (a single resonance at δ = –360.0 NMR spectrum of a [D6]DMSO solution of 2 shows two
ppm)[5a] which is characteristic of a C2O4 environment resonances at –385.7 and 8.3 ppm (Table 1). Whereas, the
around tin atoms.[1b]
signal at δ = –385.7 ppm corresponds to the six-coordinate
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Synthesis, Structure, Reactivity of Hydrated and Dehydrated Organotin Cations
Table 1. Solution studies of some of the selected organotin compounds.
FULL PAPER
Entry Compound
Specific conductivity Molar conductivity
119Sn NMR
[δ, ppm]
Ref.
[µScm–1]
[Scm2 mol–1]
[3c]
[3c]
[3d]
[5a]
1
2
3
4
5
6
7
8
{nBu2Sn(µ-OH)(H2O)(O3SCF3)}2
870[a]
43.5[a]
49.7[a]
40.0[a]
158[b]
300[b]
150[c]
376[b]
250[b]
162[b]
–
–203.2[h] (–209.7[i])
–249.7[h] (–249.6[i])
–188.4[i]
–
{[tBu2Sn(µ-OH)(H2O)]+·CF3SO3 }2
994[a]
–
{[(2-C6H5–C4H8)2Sn(µ-OH)(H2O)]+·CF3SO3 }2
805[a]
1
3
4
2
5
6
946[b]
–360.04[j]
1811[b]
898[c]
–360.61[j]
this work
this work
this work
this work
–384.91[k]
2257[b]
1503[b]
971[b]
–385.7, +8.3[k]
–284.28, –463.8[l]
–283.97, –462.77[l]
–296.4[l] (–343.9[i])
–302.1[l] (–363.5[i])
–282.8, –461.8[m]
9
this work
[Me2Sn(H2O)2(OPPh3)2]2+·2CF3SO3
714[d]
–
[3e]
10
11
12
[nBu2Sn(H2O)2(OPPh3)2]2+·2CF3SO3
705[d]
–
–
–
[3e]
[6]
foot-ball cage[n]
5[e]
200[f]–1210[g]
[a] 10 mmol/L in CH3CN. [b] 3 mmol/L in CH3OH. [c] 3 mmol/L in DMF. [d] 3.3 mmol/L in CH3CN. [e] 5 mmol/L in CD2Cl2 (for pure
CD2Cl2, 5 µScm–1). [f] 5 mmol/L in DMSO. [g] 50 mmol/L in DMSO. [h] [D6]acetone. [i] CD3CN. [j] CD3OD. [k] [D6]DMSO. [l] CDCl3.
–
[m] CD2Cl2. [n] Anion: 2 4-MeC6H4SO3 .
Scheme 3. Solution equilibrium exhibited by the cation 2. S: more polar solvents (CH3OH or [D6]DMSO).
C2O4 environment around tin, the value of +8.3 ppm is Molecular Structure
quite unusual for a diorganotin oxo species and could be
attributed to a tetracoordinate tin containing two coordi-
Whereas the molecular structures of 1 and 2 have been
nated DMSO molecules.[7] If a very dilute solution is used determined previously,[5] that of 6 is reported here. The mo-
only the signal at +8.3 ppm is seen. This could presumably lecular structure of 6·2(dioxane) is shown in Figure 1 (a).
due to the highly polar nature of the solvent DMSO which The macrocation is composed of a centrosymmetric
displaces all the ligated (water and sulfonate) groups of tin [(nBuSn)12(µ3-O)14(µ2-OH)6]2+ moiety with the asymmetric
and thereby producing a [nBu2Sn(DMSO)2]2+ species 2b unit possessing two symmetry-related “half molecules”. The
(Scheme 3).
structure of this cationic tin cage was described previously
The conductivity values of 5 and 6 suggest that these by the use of anions such as chloride,[8a] hydroxide[8b] or
compounds are 1:2 electrolytes in solution. While the ob- phosphinate.[8c] There has been one report on the structure
served specific and molar conductivities of
5 are of this macrocation where p-toluenesulfonate is the counter
1503 µScm–1 and 250 Scm2 mol–1 (3 mmol/L in CH3OH), anion.[6] The structure of the macrocation in 6 is like a
the respective values observed for 6 are 971 µScm–1 and “football” consisting of twelve tin atoms which are linked
162 Scm2 mol–1 (3 mmol/L in CH3OH), respectively by µ3-oxo and µ2-hydroxo bridges. All the n-butyl chains
(Table 1). The 119Sn NMR spectra of 5 and 6 show two situated on the tin atom are pointing outside the cage core.
resonances around –280 and –460 ppm. The chemical shift The bonding parameters found in this cage are given in
value of δ = –280 ppm is characteristic of the five-coordi- Table 2 and are comparable with the literature values.[6,8]
nate tin situated at the equator of the molecule whereas the The structure of the molecule can be understood as follows.
signal at δ = –460 ppm is due to the presence of six-coordi- Among the twelve tin atoms present in the molecule, six are
nate tins at the poles.[6]
situated at the two poles of the cage and the remaining six
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V. Chandrasekhar et al.
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Figure 1. (a) View of the two molecules of 6 present in its asymmetric unit (at 50% ellipsoidal probability level). The unlabeled atoms
are symmetric counterparts of the labeled atoms. All the n-butyl groups on tin atoms along with their protons and protons in the sulfonate
moieties are removed. (b) View of the two poles consist of two trimeric O-capped subunits of Sn3(µ3-O)(µ2-OH)3. (c) View of the equator
is spanned by a hexameric oxotin cycle Sn6(µ3-O)12.
Table 2. Comparison of (bond) distances in the core structures of selected monoorgano oxotin cages.
Compound
Average Sn–O(µ3) Average Sn–OH(µ2) Average Sn–O(X) Average Sn···Sn[e] Inter pole [O(µ3)···O(µ3)]
Ref.
[Å]
[Å]
[Å]
[Å]
[Å]
Foot-ball cage 6[a]
2.087(4)[f]
2.117(4)[g]
2.059(4)[h]
2.086(4)[i]
2.112(4)[j]
2.063(4)[k]
2.080(2)[f]
2.115(2)[g]
2.057(8)[h]
2.091(7)[f]
2.054(8)[g]
2.140(8)[h]
2.117(2)[f]
2.098(2)[g]
2.060(2)[h]
2.075(5)
2.110(5)
–
6.366(5)
3.955(5)
this work
2.109(4)
2.119(2)
2.096(8)
2.142(2)
–
–
–
–
6.386(6)
6.379(3)
6.331(6)
6.373(3)
3.938(4)
3.984(2)
3.899(6)
3.996(3)
Foot-ball cage[b]
Foot-ball cage[c]
Foot-ball cage[d]
[6]
[8b]
[8a]
[9b]
[9a]
[9c]
O-Capped cluster
Double O-capped cluster
Drum
2.128(6)
2.172(2)
–
2.122(6), X = P
2.072(2), X = P
2.155(5), X = C
–
6.337(1)[l]
–
–
3.778(4)
–
2.065(3)
2.101(5)
–
–
[a] Two crystallographically independent molecules are present; anion: two 2,5-Me2C6H3SO3 . [b] Anion: two 4-MeC6H4SO3 . [c] Anion:
two OH–. [d] Anion: two Cl–. [e] Average distance between the diametrically opposite tin atoms present in the equator. [f] Sn is bonded
with µ3-capped oxygen (O-capped) in the poles. [g] Pole tin atoms bonded with µ3-oxygens which are part of the equator. [h] Equator tin
atoms bonded with µ3-oxygens which are part of the equator. [i] Sn is bonded with µ3-capped oxygen (O-capped) in the poles. [j] Pole tin
atoms bonded with µ3-oxygens which are part of the equator. [k] Equator tin atoms bonded with µ3-oxygens which are part of the
equator. [l] Average distance between the diametrically opposite phosphorus atoms present in the equator.
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Synthesis, Structure, Reactivity of Hydrated and Dehydrated Organotin Cations
FULL PAPER
tin atoms occupy the equator of the cage. The poles consist cages have resulted in the formation of two different rings; a
of two trimeric O-capped subunits of [(nBuSn)3(µ3-O)(µ2- seven-membered Sn2O4S ring and a 12-membered Sn2O8S2
OH)3] (Figure 1, b).[9a] Within these subunits the tin atoms ring. The average O···O distance observed in this molecule
are hexa-coordinate and possess bridging oxo and hydroxo is 2.72 Å and are comparable with the p-toluenesulfonate
groups.
derivative.[6] The distance between two such polymeric
The shorter and longer Sn···Sn distances between the two sheets is 11.11 Å. Ribot et al. have utilized a similar type of
poles are given in Figure 1 (b). The equator of the cage is cage as versatile nanobuilding blocks for the design of tin-
spanned by a hexameric cycle [(nBuSn)6(µ2-O)12] (Figure 1, based organic–inorganic hybrid materials.[10]
c).[9a] In this sub-unit the tins are five-coordinate and are
nearly square pyramidal. This hexameric cycle is stitched by
Catalysis
In solution all the organotin cations behave as 1:2 elec-
trolytes (Table 1). In view of their anticipated Lewis acidity,
these compounds were tested as catalysts for acetylation of
alcohols. All the organotin cations are very effective in the
acetylation reactions of alcohols (Table 3 and Table 4).
These reactions are completed much faster than those cata-
means of six distannoxane motifs (Sn2O2) with the average
diameter of the cycle being 6.366(5) Å. Thus, it is possible
to envisage the construction of the cage by capping each
side of the hexameric cycle by the two trimeric tin units.
Supramolecular Assembly
In compound 6, two molecules of the 2,5-dimethylben- lyzed by neutral tetraorganodistannoxanes.[11] Thus, acety-
zenesulfonate anion interact with three hydroxy groups at lation of menthol (7d) and cholesterol (7e) are completed
the poles through intermolecular O–H···O hydrogen bond- only in 15 min (Table 3; Entries 19–25 and 26–32). Interest-
ing to generate a one-dimensional chain structure (Fig- ingly, inspite of low positive charge, the macrocations 5 and
ure 2). The bonding parameters involved in these hydrogen 6 are also reasonably effective although the reaction times
bonds point to the fact that these are essentially strong hy- are slightly longer.[3d] The dications 1 and 3 are the most
drogen bonds. Hydrogen-bonding interactions among these effective, in keeping with their increased Lewis acidity.
Figure 2. O–H···O hydrogen-bond-mediated one-dimensional supramolecular assembly in compound 6. All the n-butyl groups on tin
atoms along with their protons and protons in the sulfonate moieties are removed. Bonding parameters for hydrogen bonding are:
O8–H8 0.701(1), H8···O103 2.027(2), O8···O103 2.701(1) Å, O8–H8···O103 161.45(3)°; O9–H9 0.680(4), H9···O101 2.104(3), O9···O101
2.757(3) Å, O9–H9···O101 161.21(4)°; O10–H10 0.688(2), H10···O102 2.043(4), O10···O102 2.725(5) Å, O10–H10···O102 171.22(1)°; O11–
H11 0.696(6), H11···O203 1.985(4), O11···O203 2.681(8) Å, O11–H11···O203 178.18(5)°; O18–H18 0.696(1), H18···O202 2.053(3),
O18···O202 2.736(8) Å, O18–H18···O202 167.44(1)°; O20–H20 0.690(1), H20···O201 2.058(3), O20···O202 2.721(5) Å, O20–H20···O201
161.45(2)°.
Eur. J. Inorg. Chem. 2006, 4129–4136
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Thus, even 0.05 mol-% of 1 is sufficient to drive the reaction Table 4. Acetylation of phenols catalyzed by organotin cations.[a]
to completion (Table 3; Entries 2 and 10). In all instances,
just 0.2 mol-% of the organotin catalyst is sufficient for the
completion of acetylation.
Table 3. Acetylation of alcohols catalyzed by organotin cations.[a]
[a] For reaction Scheme, see Table 3; Reaction conditions: R–OH
(1 mmol); Ac2O (1 mL); catalyst (mol-%); room temp. [b] Isolated
yield. [c] See ref.[5a]
required (1 mol-%). Interestingly the dodecanuclear macro-
cations (5 and 6) are as effective as the mononuclear dicat-
ions (1, 3 and 4).
Table 5. Transacetylation reactions using organotin cations.[a]
[a] Reaction conditions: R–OH (1 mmol); Ac2O (1 mL); catalyst
(mol-%); room temp. [b] Isolated yield. [c] See ref.[5a] [d] Product:
diester.
Acetylation of phenols is also catalyzed quiet readily by
the dications 1 and 3. β-Naphthol (7h) is acetylated in the
presence of 3 in nearly 55 min (Table 4; Entry 17). The reac-
tions catalyzed by dinuclear and dodecanuclear organotin
cations 2, 5 and 6 require longer times (Table 4; Entries 5–
7, 12–14 and 19–21). However, as before only 0.2 mol-% of
the catalyst is required for completion of the reaction.
In order to assess if the organotin cations can be used
for transacetylation reactions, two test cases were examined,
using the reaction of the alcohols 7a and 7b with vinyl ace-
[a] Reaction conditions: R–OH (1 mmol); vinyl acetate (10 mmol);
catalyst (1 mol-%); 75 °C. [b] Isolated yield.
Conclusions
In summary, we report a series of organotin cations with
tate (10) (Table 5). Transacetylation was completed in all varying nuclearity and charge and have shown their efficacy
cases quantitatively, although higher catalyst loadings were in acetylation and in transacetylation reactions. All of the
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Synthesis, Structure, Reactivity of Hydrated and Dehydrated Organotin Cations
FULL PAPER
w/w water solution) (0.45 g, 2.87 mmol) in toluene (150 mL) was
heated under reflux for 72 h using a Dean–Stark apparatus to re-
move the water formed in the reaction by azeotropic distillation.
The reaction mixture was cooled and filtered through a sintered
funnel (G-4) and the clear filtrate was evaporated in vacuo to yield
5 as a white amorphous solid (1.88 g, 95% yield). M.p. 196 °C.
C60H124O26S2Sn12 (2750.26): calcd. C 26.20, H 4.54; found C 26.09,
organotin cations are air-stable solids that can be prepared
in excellent yields in a one-step synthesis, thus making them
as potentially useful reagents.
Experimental Section
H 4.24. IR (KBr, cm–1): ν = 3214 (br., OH), 1258 (s, SO assym.
General Remarks: Solvents were dried with sodium benzophenone
ketyl and were collected from the still at the time of reaction.
(nBu3Sn)2O, [nBu2SnO]n, nBuSn(O)(OH), 1,5-C10H6(SO3H)2·4H2O
(Aldrich), -menthol (Lancaster), cholesterol (Acro chemicals), cin-
namyl alcohol (Fluka), C6H5SO3H (75% w/w water solution), phe-
nol, p-cresol, acetic anhydride, vinyl acetate and β-naphthol (sd-
fine, India) were purchased and used as such without any further
purification. 2,5-Me2C6H3SO3H,[12] 1-phenylethanol,[12] 1,3-di-
phenyl-2-propen-1-ol[12] and organotin cations 1[5a] and 2[5b] were
prepared by literature methods. Melting points were measured with
a JSGW melting point apparatus and are uncorrected. Elemental
analyses were carried out with a Thermoquest CE instruments
model EA/110 CHNS-O elemental analyzer. Infrared spectra were
recorded in dichloromethane solution as well as neat liquid or as
KBr pellets with a FT-IR Bruker-Vector Model. 1H and 119Sn
NMR spectra were obtained with a JEOL-JNM LAMBDA 400
model spectrometer using CDCl3, CD3OD and (CD3)2SO solutions
˜
3
str.), 1194 (s, SO3 assym. str.), 1126 (s, SO3 sym. str.), 1035 (s, SO3
1
ionic) and 618 (m, C–S). H NMR (400 MHz, CDCl3, ppm): δ =
0.79–0.89 (m, 36 H, butyl CH3), 1.05–1.69 (m, 72 H, Sn–
CH2CH2CH2) and 6.88–7.79 (m, 10 H, aromatic). 119Sn NMR
(150 MHz, CDCl3, ppm): δ = –284.28 [s, 2J(117/119Sn–13C) = 204,
2
208 Hz] and –463.8 [s, J(117/119Sn–13C) = 204 Hz].
–
Synthesis of [(nBuSn)12(µ3-O)14(µ2-OH)6]2+·2 2,5-Me2C6H3SO3
(6): A mixture of nBuSn(O)(OH) (3.36 g, 16.10 mmol) and 2,5-
Me2C6H3SO3H (1.0 g, 5.37 mmol) in toluene (150 mL) was heated
under reflux for 72 h using a Dean–Stark apparatus to remove the
water formed in the reaction by azeotropic distillation. The reac-
tion mixture was cooled and filtered through a sintered funnel (G-
4) and the clear filtrate was evaporated in vacuo to yield 6 as a
white amorphous solid (3.62 g, 96% yield). Crystals suitable for
single-crystal X-ray diffraction were obtained by recrystallizing
compound
6 in dioxane with 0.5% water. M.p. 158 °C.
1
with shifts referenced to tetramethylsilane (for H NMR) and tet-
C64H132O26S2Sn12 (2806.39): calcd. C 27.39, H 4.74; found C 26.97,
ramethyltin (for 119Sn NMR), respectively. 119Sn NMR spectra
were recorded under broad-band decoupled conditions. Conductiv-
ity measurements were done with a Century Digital Conductivity
Meter Model CC-601.
H 4.85. IR (KBr, cm–1): ν = 3198 (br., OH), 1193 (s, SO assym.
˜
3
str.), 1195 (s, SO3 assym. str.), 1088 (s, SO3 sym. str.), 1021 (s, SO3
1
ionic) and 616 (m, C–S). H NMR (400 MHz, CDCl3, ppm): δ =
0.80 (t, J = 7.32 Hz, 18 H, butyl CH3), δ = 0.88 (t, J = 7.36 Hz, 18
H, butyl CH3), 1.19–1.32 (m, 24 H, Sn–CH2), 1.38–1.70 (m, 48 H,
butyl CH2CH2), 2.23 (s, 6 H, Ar–CH3), 2.55 (s, 6 H, Ar–CH3), 7.00
(s, 2 H, aromatic), 7.09 (s, 2 H, aromatic) and 7.69 (s, 2 H, aro-
matic). 119Sn NMR (150 MHz, CDCl3, ppm): δ = –283.97 [s,
2J(117/119Sn–13C) = 204, 207 Hz] and –462.77 [s, 2J(117/119Sn–13C) =
205 Hz].
Synthesis of [nBu2Sn(H2O)4]2+·2C6H5SO3 (3):
A mixture of
–
[nBu2SnO]n (0.42 g, 1.68 mmol) and C6H5SO3H (75% w/w water
solution) (0.70 g, 3.34 mmol) in toluene (60 mL) was heated under
reflux for 8 h using a Dean–Stark apparatus to remove the water
formed in the reaction by azeotropic distillation. A white puffy
solid formed in the reaction was filtered by a sintered funnel (G-
4), dried (in air) and identified as 3 (0.87 g, 87% yield). M.p. 270 °C
(dec.). C20H36O10S2Sn (619.33): calcd. C 38.78, H 5.85; found C
General Procedure for Acetylation of Alcohols and Phenols:[5a]
A
37.94, H 5.61. IR (KBr, cm–1): ν = 3420 (br., H O), 1251 (s, SO
mixture of the alcohol or phenol (7a–h) (1 mmol), acetic anhydride
(8) (1 mL) and catalytic amount (mol%) of the organotin catalyst
1–6 were stirred at room temperature. The progress of the reaction
was monitored by TLC. At the end of the reaction excess acetic
anhydride was removed in vacuo. The residual portion was dis-
solved in minimum amount of dichloromethane and filtered
through a short column (in some cases the compound was eluted
with ethyl acetate and hexane) to yield the corresponding acetate
˜
2
3
assym. str.), 1192 (s, SO3 assym. str.), 1070 (s, SO3 sym. str.), 1022
(s, SO3 ionic) and 624 (m, C–S). 1H NMR (400 MHz, CD3OD,
ppm): δ = 0.83 (t, J = 7.31 Hz, 6 H, butyl CH3), 1.25 (q, J =
7.31 Hz, 4 H, Sn–CH2), 1.58–1.64 (m, 4 H, butyl CH2), 1.75–1.80
(m, 4 H, butyl CH2), 7.43–7.51 (m, 6 H, aromatic) and 7.82–7.85
(m, 4 H, aromatic). 119Sn NMR (150 MHz, CD3OD, ppm): δ =
–360.61 (s).
1
9a–h. All the acetates were characterized by H NMR spectra and
–
Synthesis of [nBu2Sn(H2O)4]2+·1,5-C10H6(SO3 )2 (4): A mixture of
compared with authentic samples.
[nBu2SnO]n (0.30 g, 1.20 mmol) and 1,5-C10H6(SO3H)2·4H2O
(0.43 g, 1.20 mmol) was taken in toluene (60 mL) and heated under
reflux for 8 h using a Dean–Stark apparatus to remove the water
formed in the reaction by azeotropic distillation. A white solid
formed in the reaction was filtered by a sintered funnel (G-4) and
dried (in air) to obtain 4 in good yield (0.66 g, 93% yield). M.p. Ͼ
280 °C (dec.). C18H32O10S2Sn (591.91): calcd. C 36.56, H 5.45;
General Procedure for trans-Acetylation Reactions: A mixture of
alcohol (7a–b) (1 mmol), vinyl acetate (10) (10 mmol) and catalytic
amount (1 mol%) of the tin catalyst 1–6 were refluxed at 75 °C.
The progress of the reaction was monitored by TLC. After the reac-
tion was complete, excess vinyl acetate was evaporated and the resi-
due was subjected to column chromatography on silica gel to give
acetates 9a–b in good yields. All the acetates were characterized by
1H NMR spectra and compared with authentic samples.
found C 36.29, H 5.19. IR (KBr, cm–1): ν = 3454 (br., H O), 1206
˜
2
(s, SO3 assym. str.), 1161 (s, SO3 assym. str.), 1044 (s, SO3 ionic)
and 613 (s, C–S). 1H NMR (400 MHz, [D6]DMSO, ppm): δ = 0.86
(t, J = 7.2 Hz, 6 H, butyl CH3), 1.28 (q, J = 7.2 Hz, 4 H, Sn–
CH2), 1.47–1.49 (m, 8 H, butyl CH2CH2), 7.44 (t, J = 7.2 Hz, 2 H,
aromatic), 7.95 (d, J = 6.8 Hz, 2 H, aromatic) and 8.86 (d, J =
8.4 Hz, 2 H, aromatic). 119Sn NMR (150 MHz, [D6]DMSO,
ppm): –384.91(s).
X-ray Crystallographic Study: Colorless block-like crystal of 6 suit-
able for single-crystal X-ray diffraction was loaded on a Bruker
AXS Smart Apex CCD diffractometer. The details pertaining to
the data collection and refinement for 6 are as follows: size 0.4×
0.4× 0.3 mm3; empirical formula C66H136O27S2Sn12; Mw = 2850.15;
¯
triclinic; space group P1; a = 12.6693(11) Å; b = 16.4765(14) Å; c
Synthesis of [(nBuSn)12(µ3-O)14(µ2-OH)6]2+·2C6H5SO3– (5): A mix-
ture of nBuSn(O)(OH) (1.80 g, 8.62 mmol) and C6H5SO3H (75%
= 24.8100(2) Å; α = 77.131(2)°; β = 86.091(2)°; γ = 69.637(2)°; V
= 4733.1(7) Å3; Z = 2; T = 150(2) K; Dcalcd. = 2.000 Mg·m–3; Mo-
Eur. J. Inorg. Chem. 2006, 4129–4136
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4135

V. Chandrasekhar et al.
FULL PAPER
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Acknowledgments
We are thankful to the DST, India, for financial support. K. G.,
P. S. and P. S. gratefully acknowledge the CSIR, New Delhi, India,
for Research Fellowships. A. S. and S. Z. thank the EPSRC of the
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Received: May 19, 2006
Published Online: August 10, 2006
4136
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 4129–4136