Microwave assisted solid-state synthesis of functional organotin carboxylates from sterically encumbered 3,5-di-tert-butylsalicylic acid

Article abstract of DOI:10.1016/j.jorganchem.2008.04.001

Microwave assisted solid-state reaction between equimolar quantities of sterically encumbered 3,5-di-tert-butylsalicylic acid (H₂-DTBSA) and n-butylstannoic acid results in the formation of hexameric drum shaped stannoxane [ⁿBuSn(O)(H-DTBSA)]₆ (1). Synthesis of 1 could not be achieved under normal thermal conditions or mechanical grinding. However, the azeotropic removal of water produced in the reaction of ⁿBu₂SnO with 3,5-di-tert-butyl salicylic acid in benzene yielded the tetrameric ladder shaped stannoxane [{ⁿBu₂Sn(H-DTBSA)}₂O]₂ (2), which could also be synthesized in better yields by microwave irradiation as in the case of 1. Compounds 1 and 2 have been characterized by elemental analysis, IR, MALDI-MS and NMR (¹H and ¹³C) spectroscopy. The structures of compound 1 and 2 are determined by single crystal X-ray diffraction techniques. Compound 1 is hexameric with a Sn₆O₆ drum core while compound 2 forms a ladder structure with three Sn₂O₂ rings, both decorated with -OH functionalities on the exterior of the polyhedral structure. While the formation of 1 from n-butylstannoic acid is straightforward, the formation of 2 from nBu₂SnO (and not a cyclic structure similar to 3, where the phenolic oxygen also coordinates to tin) can be understood in terms of the increased steric hindrance in DTBSA for the phenolic protons to react with tin.

Full text of DOI:10.1016/j.jorganchem.2008.04.001

Journal of Organometallic Chemistry 693 (2008) 3111–3116
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Microwave assisted solid-state synthesis of functional organotin carboxylates
from sterically encumbered 3,5-di-tert-butylsalicylic acid
*
Ramaswamy Murugavel , Nayanmoni Gogoi
Department of Chemistry, IIT-Bombay, Powai, Mumbai 400 076, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Microwave assisted solid-state reaction between equimolar quantities of sterically encumbered 3,5-di-
tert-butylsalicylic acid (H2-DTBSA) and n-butylstannoic acid results in the formation of hexameric drum
shaped stannoxane [nBuSn(O)(H-DTBSA)]6 (1). Synthesis of 1 could not be achieved under normal ther-
mal conditions or mechanical grinding. However, the azeotropic removal of water produced in the reac-
tion of nBu2SnO with 3,5-di-tert-butyl salicylic acid in benzene yielded the tetrameric ladder shaped
stannoxane [{nBu2Sn(H-DTBSA)}2O]2 (2), which could also be synthesized in better yields by microwave
irradiation as in the case of 1. Compounds 1 and 2 have been characterized by elemental analysis, IR,
MALDI-MS and NMR (1H and 13C) spectroscopy. The structures of compound 1 and 2 are determined
by single crystal X-ray diffraction techniques. Compound 1 is hexameric with a Sn6O6 drum core while
compound 2 forms a ladder structure with three Sn2O2 rings, both decorated with –OH functionalities
on the exterior of the polyhedral structure. While the formation of 1 from n-butylstannoic acid is
straightforward, the formation of 2 from nBu2SnO (and not a cyclic structure similar to 3, where the phe-
nolic oxygen also coordinates to tin) can be understood in terms of the increased steric hindrance in
DTBSA for the phenolic protons to react with tin.
Received 8 January 2008
Received in revised form 27 March 2008
Accepted 1 April 2008
Available online 7 April 2008
Keywords:
Organotin
Carboxylates
NMR
X-ray structures
Microwave synthesis
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
via dearylation reaction of Ph3Sn(OH) with Cl3CCOOH [7]. On the
other hand, tetrameric tin carboxylates [{R2Sn(R0COO)2}2O]2 (type
Exploring newer and better experimental techniques to carry
out chemical transformations has been an important premise of
chemical synthesis. Irradiation of microwave on homogenous reac-
tion mixtures and on solid surfaces has been one such technique,
which has emerged as a useful method for achieving better yields
of the products, significant reduction in reaction time, and reduc-
tion or elimination of environmentally detrimental solvents. For
these reasons, microwave assisted synthesis has clearly become a
rapidly growing field of study especially for various organic trans-
formations [1].
Reactions of organotin oxides with carboxylic acids have been
studied in detail because of the industrial [2] and biological [3]
applications of the organotin carboxylates. In addition, a wide
spectrum of interesting and exotic structural types can be obtained
by changing either the stoichiometry of the reactants or changing
the additional functionality on the carboxylate ligand [4–9]. Reac-
tion of various carboxylic acids with RSn(O)(OH) has been exten-
A–D; Fig. 1) are obtained when the reaction between R2SnO and
R0COOH is carried out in strictly 1:1 stoichiometry [8d,9d].
Recently we reported that the presence of other reaction centers
on the carboxylate ligand (e.g. 3,5-di-isopropyl salicylic acid) leads
to the formation of a hexameric cyclic tin carboxylate of formula
[nBu2Sn(3,5-iPr2C6H2(O)(COO))]6 [8a]. Later this reaction was gen-
eralized by Ma et al. with the synthesis of [nBuSn(o-SC6H4COO)]6
[10].
The reaction between an organotin oxide or acid and a carbox-
ylic acid proceeds through the elimination of water to produce
oligomeric organotin carboxylate clusters. Traditionally, the water
produced in the above reaction is removed from the reaction mix-
ture via simultaneous azeotropic distillation from a benzene or tol-
uene medium, depending on the temperature required for the
reaction. Not only these reactions are very slow but often require
high temperatures in environmentally detrimental solvents. Con-
sidering the industrial and biological utilization of organotin car-
boxylates, a much faster and environmentally benign method for
their synthesis is desired. Chandrasekhar et al. have recently re-
ported the synthesis of organotin carboxylates having most com-
monly observed structure using a solventless methodology where
the starting materials are ground together [11]. The only limita-
tions of this very useful method are the relatively slower rates
and the hazards associated with prolonged grinding of the reaction
sively studied and in most of the cases
a drum shaped
[RSn(O2CR0)]6 stannoxane with a Sn6O6 core has been isolated
[4a,6]. The only exception where a mono-organotin carboxylate
adopts linear chain structure, [SnPh(O2CCCl3)O]6, was obtained
* Corresponding author. Tel.: +91 22 2576 7163; fax: +91 22 2572 3480.
E-mail address: rmv@chem.iitb.ac.in (R. Murugavel).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.04.001

3112
R. Murugavel, N. Gogoi / Journal of Organometallic Chemistry 693 (2008) 3111–3116
R'
R'
R'
R'
HO
O
OH
R
O
O
O
O
O
O
O
O
R
O
HO
Sn
O
O
Sn
Sn
O
Sn
Sn
O
O
O
nBuSn(O)(OH). xH2O
O
R
Sn
OH
O
O
Sn
O
Sn
O
Sn
Sn
Sn
O
O
O
O
1. Microwave
2. C6H6, Reflux
O
O
Sn
Sn
R
O
O
O
O
Sn
O
R
O
O
O
O
R
O
O
HO
R'
OH
COOH
OH
R'
R'
R'
1
Type B
e.g. R' = C6H4NH2-
Type A
e.g. R' = CF3
p
OH
R'
R'
O
R'
O
R'
O
O
O
O
R
O
R
R
Sn
Sn
O
R
Sn
Sn
O
O
Sn
O
OH
O
O
Sn
O
O
O
Sn
Sn
O
O
O
Sn
Sn
Sn
O
O
HO
R
Sn
R
O
OH
O
O
R
R
COOH
O
O
O
O
R'
O
HO
`2
O
R'
R'
R'
Type C
e.g. R' = Me
Type D
e.g. R' = tBu
nBu2SnO
C6H6, Reflux
R
Fig. 1. Four different structural types of [{R2Sn(R0COO)2}2O]2.
O
O
O
Sn
R
O
O
O
R
R
O
Sn
Sn
R
O
R
OH
COOH
mixture (organotin carboxylates are known to have anti-neoplastic
properties) [12]. Continuing our earlier studies on tin carboxylates
derived from bulkier carboxylic acids [8a] we wish to report in this
contribution a synthetic strategy that utilizes both grinding and
microwave irradiation to efficiently remove the water produced
in the condensation reaction between an organotin acid/oxide
and 3,5-di-tert-butylsalicylic acid.
O
O
O
R
O
O
R
Sn
O
Sn
R
R
R
Sn
R
O
O
O
O
3
R = nBu
2. Results and discussion
Scheme 1. Synthesis of 1–3.
2.1. Synthesis and characterization of [nBuSn(O)(H-DTBSA)]6 (1)
2.2. Molecular structure of 1
The reaction between n-butylstannoic acid and H2-DTBSA in
refluxing benzene or toluene did not yield 1, but an insoluble pow-
der which could not be characterized. Similarly, the use of grinding
methodology described by Chandrasekhar et al. [11] also did not
lead to product formation in this case. Hence this reaction was at-
tempted using microwave irradiation. Initially the solid reactants
were ground together in a mortar to obtain a homogeneous mix-
ture and transferred to a Petri dish. The homogeneous mixture
was covered with another Petri dish and placed inside a microwave
oven and irradiated for 2 min at 400 W. The irradiation was re-
peated three times during which time water produced from the
reaction condensed on the lid. In order to completely remove the
water from the product formed, the contents of the Petri dish were
dissolved in benzene and heated under reflux using a Dean–Stark
apparatus. After all the water has been removed as azeotrope,
the clear benzene solution was left for crystallization to obtain sin-
gle crystals of [nBuSn(O)(H-DTBSA)]6 (1) in good yield (Scheme 1).
Compound 1 is a stable colorless solid that melts at 200–203 °C.
The IR spectrum of compound 1 shows a broad band centered at
3239 cmꢀ1, indicating the presence of unreacted phenolic –OH
group on the carboxylate ligand. The symmetrical double absorp-
tion observed for 1 at 1566 and 1531 cmꢀ1 is due to the antisym-
metric stretching vibrations of the carboxylate ligands, which
bridge the tin centers in the drum structure. The 1H and 13C NMR
data obtained are consistent with the formulation of compound
1. In particular, the presence of a broad resonance at 10.62 ppm
is indicative of the non-participation of the phenolic group of the
ligand in the reaction with the tin acid.
Colorless rectangular crystals of 1 obtained directly from the
reaction mixture were found to be suitable for single crystal
X-ray diffraction measurements. The compound crystallizes in
ꢀ
the centrosymmetric triclinic P1 space group with four molecules
of benzene. The final refined molecular structure of compound 1
is shown in Fig. 2 while important bond lengths and bond angles
are listed in Table 2. The centrosymmetric structure of 1 is built
around a drum shaped Sn6O6 central stannoxane core that is made
up of two hexameric Sn3O3 rings. These hexameric Sn3O3 rings ex-
ist in a puckered chair conformation and form the upper and lower
lids of the drum polyhedron. The two Sn3O3 rings are connected
further by six Sn–O bonds containing tri-coordinate O atoms and
thus the side faces of the drum are characterized by six four-mem-
bered Sn2O2 rings. It can be seen from Fig. 2 that the four-mem-
bered Sn2O2 rings are not planar; the oxygen atoms are tilted
toward the cavity of the drum. Thus the interior of the drum can
be considered as a crown made of six oxygen atoms in a trigonal
antiprismatic arrangement. The two tin atoms in each of the six
Sn2O2 rings are bridged by a carboxylate ligand to form a symmet-
rical bridge between two carboxylate ligands. The Sn–O bond
lengths inside the core range between 2.072(3) and 2.157(4) Å.
These distances are comparatively shorter than the Sn–O bonds
to the bridging carboxylate ligands (2.145(3)–2.197(4) Å). All the
six tin atoms are chemically equivalent and are six coordinate with
three of the coordination sites occupied by bridging tri-coordinate
oxygen atoms. While oxygen atoms from the bridging carboxylate

R. Murugavel, N. Gogoi / Journal of Organometallic Chemistry 693 (2008) 3111–3116
3113
Fig. 2. Molecular structure of 1.
ligands occupy two of the coordination sites, the sixth coordination
site is occupied by the n-butyl group. The most interesting feature
of the structure of 1 is the presence of the free phenolic –OH group
on each of the DTBSA ligand. Thus the total of six –OH functional-
ities on the surface of the tin cluster offer excellent opportunities
for further reactions with other metal centers.
integrated intensities are also consistent with a different formula-
tion for compound 2 compared to the earlier reported 3 [8a]. Fur-
ther, the presence of a singlet resonance for the phenolic OH group
at d 11.81 ppm confirms that compound 2 has a different structure
and stoichiometry.
2.4. Molecular structure of 2
2.3. Synthesis and characterization of [{nBu2Sn(H-DTBSA)}2O]2 (2)
Colorless rectangular crystals of 2 that are suitable for X-ray
measurements were obtained from a CH2Cl2/ petroleum ether mix-
ture at 5 °C after 1 week. Single crystal X-ray diffraction measure-
ments indicate that the compound crystallizes in centrosymmetric
We had earlier reported that the reaction of one equivalent of
nBu2SnO with one equivalent of 3,5-di-iso-propyl salicylic acid
(DIPSA) leads to the formation of an unprecedented hexameric cyc-
lic diorganotin carboxylate 3 where both the carboxylate and
phenoxide terminals of the DIPSA ligand bind to the tin atoms
through chelating and bridging modes of coordination (Scheme
1) [8a]. In order to establish the generality of this reaction for other
substituted salicylic acids and further evaluate the effect of even
larger substituents on the salicylic acid [13], the reaction of dibu-
tyltin oxide with H2-DTBSA was carried out in the present study.
Unlike in the case of reaction leading to the formation of 1 where
the use of microwave radiation was absolutely necessary, the reac-
tion between nBu2SnO and H2-DTBSA proceeds in benzene under
reflux conditions with simultaneous azeotropic removal of water
to result in 2 in 81% yield (Scheme 1). Interestingly, the use of
microwave irradiation for the synthesis of 2 resulted in better
yields in much shorter time (92 %).
Stable colorless crystalline sample of 2, which melt at 242–
245 °C, has been characterized with the aid of elemental analysis,
infrared, mass, and NMR spectroscopic techniques. The IR spec-
trum of 2 shows strong absorptions at 2960 and 2866 cmꢀ1 due
to the C–H stretching vibrations of the n- and t-butyl groups. In
addition, the t(COO)asym vibration is observed as a doublet cen-
tered at 1531 cmꢀ1 while t(COO)sym vibration is also observed as
a doublet centered at 1414 cmꢀ1. Occurrence of two different sig-
nals both for t(COO)asym and t(COO)sym vibrations reveal that com-
pound 2 contains carboxylate ligands in two different coordination
mode unlike in the case of 3. The 1H NMR spectral pattern and the
ꢀ
triclinic P1 space group with two molecules of CH2Cl2. A perspec-
tive view of the molecular structure of compound 2 shown in
Fig. 3 indicates that compound 2 falls into the category of struc-
tural type B (Fig. 1) where a central cyclic four-membered Sn2O2
core is linked to two terminal nBu2Sn entities through the l3-O
atoms (O(7)). Each pair of the central and terminal tin atoms are
asymmetrically bridged by the H-DTBSA ligand through the car-
boxylate oxygen. Thus the central Sn2O2 core is linked to the two
outer Sn2O2 rings to result a ladder-like structure as shown in
Fig. 3. In addition, the two terminal tin atoms are bonded to a ter-
minal H-DTBSA ligand (O(1)).
The coordination geometry around each of the tin atoms is best
described as distorted trigonal bipyramidal. Distortion from ideal
trigonal bipyramidal geometry in the case of Sn(1) arises primarily
due to the close proximity of the sixth, but weak, ligation through
O(2) atom. The acyl O(2) atom is located only 2.652(2) Å away from
Sn(1), which is significantly below the sum of the van der Waals ra-
dii for these atoms (3.70 Å). If this interaction is considered signif-
icant enough, then the Sn(1) atom would be best described to have
a skew-trapezoidal bipyramidal geometry with the nBu groups dis-
posed over the four Sn–O bonds. The O(1), O(2), O(4) and O(7)
atoms comprise a trapezoidal plane which is almost perpendicular
to the plane passing through C(1), Sn(1) and C(5). The Sn(1)ꢁ ꢁ ꢁO(2)
distance in 2 (2.652(2) Å) is shorter compared to those observed
for similar skew-trapezoidal bipyramid complexes reported earlier,

3114
R. Murugavel, N. Gogoi / Journal of Organometallic Chemistry 693 (2008) 3111–3116
Fig. 3. Molecular structure of 2.
[{nBu2SnO2CCH2CH2C(O)C6H5}2O]2 (2.746(7) Å) [8d] and [{nBu2-
Sn(O2CCH2-C6H4F- p)}2O]2 (2.746(7) Å) [9e] but longer than that
observed for [{Me2Sn(O2CC6H4-p-NH2)}2O]2 (2.573(6) Å) [8g].
As in the case of 1, compound 2 also contains phenolic func-
tional groups on each of the DTBSA ligand in the complex thus ren-
dering this compound as a useful starting material for further
reactions at the –OH terminal to build multimetallic systems.
(UniLab) glovebox maintained at <1 ppm of O2 and H2O. All the
chemicals used are procured from commercial sources and used
as received without any further purification. Solvents were purified
by conventional techniques and distilled prior to use. The 1H (using
Me4Si as the internal standard) and 13C NMR spectra were recorded
on a Varian VSR 400S spectrometer operated at 400 and 100 MHz,
respectively. Infrared spectra were obtained from a Perkin Elmer
FT-IR spectrophotometer with use of KBr disc. Microanalyses were
performed on a Thermo Finnigan (FLASH EA 1112) microanalyzer.
Microwave synthesis was carried out on a 1000 W Samsung
kitchen microwave oven operating at 40% of the power. Mass spec-
tra were collected using an Axima-CFR MALDI-TOF-MS (Kratos
Analytical, Manchester, UK), in the reflectron positive ion mode.
3. Conclusion
We have shown in this contribution that the reaction between
3,5-di-tert-butyl salicylic acid and nBuSn(O)(OH) ꢁ xH2O/nBu2SnO
proceeds the best under microwave irradiation conditions fol-
lowed by the complete removal of water produced in the reaction
by azeotropic distillation. It is further shown that the change of the
substituent on the aryl ring of the salicylic acid from iso-propyl to
tert-butyl has brought about interesting differences both in the
reactivity and the type of products formed. The significant out-
come of the present investigation is the isolation of two oligomeric
tin carboxylates with surface phenolic –OH groups. This opens up
further potential for using these two compounds as starting mate-
rials for cluster expansion by exploiting the highly acidic nature of
the phenolic protons. Especially interesting would be the reaction
of 1 with catalytically useful transition metal precursors. Currently
we are investigating this aspect.
4.2. Synthesis of 1 ꢁ (C6H6)4
In a mortar nBuSn(O)(OH) ꢁ (H2O)x (0.417 g, 2 mmol) and 3,5-di-
tert-butyl salicylic acid (0.500 g, 2 mmol) were mixed together and
then transferred to a Petri dish and covered with another Petri dish
and then placed in a microwave oven (400 W) and heated three
times for 2 min. The reaction mixture was transferred to a Schlenk
flask and benzene (100 mL) was added and under reflux for 6 h
using Dean–Stark apparatus for the compete removal of water.
The colorless solution obtained was kept at room temperature to
yield colorless needle shaped crystals of [1 ꢁ (C6H6)4] after 24 h.
Yield 0.780 g, 88%, m.p.: 200–203 °C. Elemental Anal. Calc. For
C114H180O24Sn6: C, 51.73; H, 6.85. Found: C, 51.77; H, 7.41%. IR
(KBr pallets, cmꢀ1): 3239(br), 2959(s), 2871(m), 1617(m),
1566(s), 1531(s), 1447(vs), 1389(vs), 1280(m), 1260(m), 1240(m),
1096(m), 1023(m), 896(w), 804(m), 674(w), 551(w), 491(w). 1H
NMR (CDCl3, ppm): d 10.62(s, 1H, OH), 7.73–7.80 (m, 1H, Ar–H),
7.36–7.48(m, 1H, Ar–H), 1.18–1.34(m, 24H, CH2 & (CH3)3C), 0.77–
0.91(m, 3H, CH3). 13C NMR (CDCl3, ppm): d 175.53 (C@O), 158.76
(Ar–C2), 140.61 (Ar–C5), 137.19 (Ar–C3), 130.74 (Ar–C4), 125.74
4. Experimental
4.1. Apparatus
Reactions were carried out under an inert atmosphere of puri-
fied nitrogen using standard Schlenk line techniques, and samples
for characterization were prepared in a nitrogen filled MBraun

R. Murugavel, N. Gogoi / Journal of Organometallic Chemistry 693 (2008) 3111–3116
3115
Table 1
(Ar–C6), 114.39 (Ar–C1), 35.31(C(CH3)3), 31.51(CH3), 29.72(aCH2),
27.84 (bCH2), 27.02 (cCH2), 13.85 (CH3). 119Sn NMR(CDCl3,
300 MHz) d: ꢀ483. Mass spectra (MALDI-MS) m/z: 884 (100%)
[(DTBSA-H)2Bu2Sn2O(H2O)]+, 843 [(DTBSA-H)2BuSn2O2(H2O)]+,
770 [(DTBSA-H)2Sn2O(H2O)]+.
Crystal data and structure refinement parameters for compounds 1 and 2
Compound
[1 ꢁ (C6H6)4]
138H204O24Sn6
2959.15
150(2)
[2 ꢁ (CH2Cl2)2]
C94H160Cl4O14Sn4
2130.78
150(2)
0.71073
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a (°)
b (°)
C
0.71073
Triclinic
4.3. Synthesis of 2 ꢁ 2CH2Cl2
Triclinic
ꢀ
ꢀ
P1
P1
4.3.1. Thermal synthesis
14.344(3)
16.3354(15)
16.3561(11)
83.292(6)
80.200(10)
73.621(13)
3613.7(9)
1
1.360
1.084
1524
0.33 ꢂ 0.26 ꢂ 0.11
2.93–25.00
31535
12.606(3)
13.396(4)
17.7186(14)
76.557(14)
73.378(14)
65.14(3)
2579.5(10)
1
1.372
1.116
1104
0.22 ꢂ 0.15 ꢂ 0.10
3.09–25.00
25898
To a suspension of nBu2SnO (0.634 g, 2.54 mmol) in benzene
(150 mL) is added 3,5-di-tert-butylsalicylic acid (0.637 g,
2.54 mmol) and heated under reflux for 6 h using Dean–Stark
apparatus during this time water produced in the reaction sepa-
rated out. The resulting solution was then dried under vacuum to
obtain a white solid which is dissolved in CH2Cl2 (20 mL)/petro-
leum ether (40 mL) mixture and filtered. The filtrate was concen-
trated under vacuum and dissolved in minimum amount of
CH2Cl2. Colorless crystals of [2 ꢁ (CH2Cl2)2] were obtained from
the filtrate at 10 °C after 1 week. Yield 1.10 g (81%).
c (°)
Volume (Å3)
Z
Dcalc (mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
Crystal size (mm3)
h Range for data collection (°)
Reflections collected
Independent reflections
Completeness of h (%)
Absorption coefficient
Refinement method
12608 [R(int) = 0.0727] 9045 [R(int) = 0.0395]
4.3.2. Microwave route
99.1
99.7
An equimolar mixture of nBu2SnO (0.499 g, 2 mmol) and 3,5-di-
tert-butylsalicylic acid (0.500, 2 mmol) was ground together to ob-
tain a homogenous mixture. It was then transferred to a Petri dish
and covered with another Petri dish and was heated in a micro-
wave at 400 W for 2 min and then cooled for 2 min. The microwave
heating cycle was repeated for two times and the resultant thick
gelatinous product was extracted with benzene (60 mL) and re-
fluxed for 6 h using a Dean–Stark apparatus in order to distill out
the water produced in the reaction. Solvent was removed under
vacuo and the residue was dissolved in 20 mL CH2Cl2–Petry ether
(2:1) mixture and filtered. White crystalline [2 ꢁ (CH2Cl2)2] were
obtained from the filtrate at 0 °C after 1 day. Yield: 0.986 g, 92 %,
m.p.: 238–240 °C. Elemental analysis for C94H160O14Cl4Sn4: Calc.:
C, 52.98; H, 7.56. Found: C, 53.51; H, 8.29%. IR (KBr pallets,
cmꢀ1): 3449(br), 2960(m), 2866(w), 1615(w), 1552(m), 1432(m),
1392(m), 1254(m), 1094(s), 1025(s), 807(s), 683(w), 630(w). 1H
NMR(CDCl3, ppm): d 11.81 (s, 1H, OH). 7.56–7.62 (m, 1H, Ar–H),
7.44 (s, 1H, Ar–H), 1.20–1.77 (m, 26H, CH2 and (CH3)3C), 0.72–
0.80 (m, 6H, CH3). 13C NMR (CDCl3, ppm): d 177.27 (C@O),
163.71/159.34 (Ar–C2), 142.00/140.14 (Ar–C5), 138.82/137.19
(Ar–C3), 130.82/130.09 (Ar–C4), 127.18/124.92 (Ar–C6), 114.92/
113.86 (Ar–C1), 35.88/34.47 (C(CH3)3), 31.76 (CH3), 30.10/29.71
(aCH2), 27.09/26.89 (bCH2), 26.75/25.91 (cCH2), 13.70/13.95
(CH3). 119Sn NMR(CDCl3, 300 MHz) d: (ꢀ203)–(ꢀ201) (quintet),
ꢀ189(m), (ꢀ182)–(ꢀ183) (m). Mass spectra (MALDI-MS) m/z:
884 [(DTBSA-H)2Bu2Sn2O(H2O)]+, 770 [(DTBSA-H)2Sn2O(H2O)]+,
650 (100%) [(DTBSA-H)2SnO(OH)]+.
0.8901 and 0.7163
Full matrix least
square on F2
12608/0/769
0.888
0.8966 and 0.7913
Full matrix least
squares on F2
9045/0/563
1.048
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R1 = 0.0467,
wR2 = 0.0826
R1 = 0.1002,
wR2 = 0.0923
0.849 and ꢀ0.855
R1 = 0.0337.
wR2 = 0.0723
R1 = 0.0546,
wR2 = 0.0745
1.183 and ꢀ1.240
R indices (all data)
Largest difference in peak and
hole (e Åꢀ3
)
Table 2
Selected bond lengths (Å) and angles (°) in 1 and 2
[nBuSn(O)(H-DTBSA)]6 (1)
Sn(1)–O(10)
Sn(1)–O(11)
Sn(1)–O(12)
Sn(1)–O(4)
2.081(4)
2.083(4)
2.092(3)
2.157(4)
2.176(3)
2.072(3)
2.083(4)
2.090(3)
Sn(2)–O(2)
Sn(2)–O(7)
Sn(3)–O(12)
Sn(3)–O(10)#1
Sn(3)–O(11)
Sn(3)–C(9)
Sn(3)–O(8)
Sn(3)–O(5)
2.145(3)
2.181(4)
2.079(4)
2.083(3)
2.098(3)
2.121(6)
2.159(4)
2.197(4)
Sn(1)–O(1)
Sn(2)–O(11)
Sn(2)–O(10)
Sn(2)–O(12)#1
O(10)–Sn(1)–O(11)
O(10)–Sn(1)–O(12)
O(11)–Sn(1)–O(12)
O(10)–Sn(1)–O(4)
O(11)–Sn(1)–O(4)
O(12)–Sn(1)–O(4)
O(10)–Sn(1)–O(1)
O(11)–Sn(1)–O(1)
O(12)–Sn(1)–O(1)
[{nBu2Sn(H-DTBSA)}2O]2 (2)
Sn(1)–O(7)#1
Sn(1)–O(1)
Sn(1)–C(1)
Sn(1)–C(5)
77.80(14)
104.84(13)
77.91(13)
157.96(14)
86.74(14)
86.86(13)
86.30(13)
87.60(14)
159.18(15)
O(11)–Sn(2)–O(10)
O(11)–Sn(2)–O(12)#1
O(10)–Sn(2)–O(12)#1
O(2)–Sn(2)–O(7)
O(11)–Sn(2)–Sn(1)
O(10)–Sn(2)–Sn(1)
O(12)–Sn(3)–O(10)#1
O(12)–Sn(3)–O(11)
O(10)#1–Sn(3)–O(11)
77.99(14)
104.85(13)
77.70(13)
77.81(14)
39.84(10)
39.85(10)
77.94(14)
77.88(13)
104.81(13)
4.4. X-ray structure determination of 1 and 2
The intensity data collection for 1 and 2 were carried out on an
Oxford Diffraction XCalibur-S diffractometer equipped with a CCD
system. Intensity data collection and cell determination protocols
were carried out using a graphite-monochromatized Mo Ka radia-
tion (k = 0.71073 Å). Structure solution for each of the compound
was obtained using direct methods (SHELXS-97) [14] and refined
using full-matrix least square methods on F2 using SHELXL-97 [15].
The positions of hydrogen atoms were either located in the succes-
sive difference maps or were geometrically placed and refined using
a riding model. All non-hydrogen atoms were refined anisotropi-
cally. No disorder or symmetry related problems were encountered
for both the compounds. Further details of the crystal data and
refinement convergence are listed in Table 1. Additional supporting
information available contains the CIF details for both 1 and 2.
2.011(2)
2.110(3)
2.125(4)
2.134(4)
2.046(2)
Sn(2)–C(9)
Sn(2)–C(13)
Sn(2)–O(7)
Sn(2)–O(4)
2.118(4)
2.132(4)
2.166(2)
2.264(2)
Sn(2)–O(7)#1
O(7)#1–Sn(1)–O(1)
O(7)#1–Sn(2)–O(7)
O(7)#1–Sn(2)–O(4)
O(7)–Sn(2)–O(4)
Sn(1)#1–O(7)–Sn(2)#1
Sn(1)#1–O(7)–Sn(2)
Sn(2)#1–O(7)–Sn(2)
84.66(9)
73.63(10)
74.89(9)
148.48(9)
122.01(12)
131.54(11)
106.37(10)
O(7)#1–Sn(1)–C(1)
O(1)–Sn(1)–C(1)
O(7)#1–Sn(1)–C(5)
O(1)–Sn(1)–C(5)
C(1)–Sn(1)–C(5)
O(7)#1–Sn(2)–C(9)
O(7)#1–Sn(2)–C(13)
106.72(13)
103.17(12)
107.85(13)
101.05(13)
139.16(16)
113.02(13)
115.34(13)

3116
R. Murugavel, N. Gogoi / Journal of Organometallic Chemistry 693 (2008) 3111–3116
(b) V. Chandrasekhar, K. Gopal, S. Nagendran, P. Singh, A. Steiner, S. Zacchini,
Acknowledgements
J.F. Bickley, Chem.-Eur. J. 11 (2005) 5437;
(c) V. Chandrasekhar, S. Nagendran, S. Bansal, A.W. Cordes, A. Vij,
Organometallics 21 (2002) 3297.
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(b) R.R. Holmes, C.G. Schmid, V. Chandrasekhar, R.O. Day, J.M. Holmes, J. Am.
Chem. Soc. 109 (1987) 1408;
This work was supported by DST, New Delhi, in the form of a
Swarnajayanti Fellowship to RM. NG thanks CSIR, New Delhi for re-
search fellowship. We thank National Single Crystal X-ray Diffrac-
tion Facility at IIT-Bombay for the intensity data of 1 and 2. We also
thank the SAIF, IIT-Bombay, for spectroscopic and analytical data.
(c) V. Dokorou, Z. Ciunik, U. Russo, D. Kovala-Demertzi, J. Organomet. Chem.
630 (2001) 205;
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Appendix A. Supplementary material
(f) T.P. Lockhart, W.F. Manders, E.M. Holt, J. Am. Chem. Soc. 108 (1986) 6611;
(g) V. Chandrasekhar, R.O. Day, J.M. Holmes, R.R. Holmes, Inorg. Chem. 27
(1988) 958.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2008.04.001.
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