Tetranuclear stiboxanes (RSb)4O6, exhibiting an adamantane-type structure

Article abstract of DOI:10.1039/c2dt30587a

Depolymerization reactions of organostibonic acids with protic ligands have been investigated. Reaction of arylstibonic acids with 8-hydroxyquinoline (8-HQ), or {2-[1H-pyrazol-5(3)-yl]naphthalene-1-ol} (H₂naphpz) in a 1:1 stoichiometry in refluxing toluene affords adamantane-like L ₄(RSb)₄O₆ clusters [(p-XC₆H ₄Sb)₄(O)₆(Q)₄] (where X = Cl (1), Br (2), QH = 8-hydroxyquinoline), [(p-ClC₆H₄Sb) ₄(O)₆(Hnaphpz)₄]·H₂naphpz (3) and [(p-Br-C₆H₄Sb)₄(O)₆(Hnaphpz) ₄]₂·H₂naphpz (4). Further a tetrameric organoantimony oxo cluster, L₄(RSb)₄O₄ [(p-ClC₆H₄Sb)₄(O)₄(naphpz) ₄] (5) has also been isolated as a side product in the reaction of arylstibonic acid with naphthylphenolic pyrazole. Interestingly 1-4 structurally resemble the dimeric form of the antimony oxide Sb₂O₃ and its mineral senarmontite.

Full text of DOI:10.1039/c2dt30587a

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PAPER
Tetranuclear stiboxanes (RSb)4O6, exhibiting an adamantane-type structure†
Ananda Kumar Jami and Viswanathan Baskar*
Received 11th January 2012, Accepted 17th August 2012
DOI: 10.1039/c2dt30587a
Depolymerization reactions of organostibonic acids with protic ligands have been investigated. Reaction
of arylstibonic acids with 8-hydroxyquinoline (8-HQ), or {2-[1H-pyrazol-5(3)-yl]naphthalene-1-ol}
(H2naphpz) in a 1 : 1 stoichiometry in refluxing toluene affords adamantane-like L4(RSb)4O6 clusters
[(p-XC6H4Sb)4(O)6(Q)4] (where X = Cl (1), Br (2), QH = 8-hydroxyquinoline), [(p-ClC6H4Sb)4(O)6-
(Hnaphpz)4]·H2naphpz (3) and [(p-Br-C6H4Sb)4(O)6(Hnaphpz)4]2·H2naphpz (4). Further a tetrameric
organoantimony oxo cluster, L4(RSb)4O4 [(p-ClC6H4Sb)4(O)4(naphpz)4] (5) has also been isolated as
a side product in the reaction of arylstibonic acid with naphthylphenolic pyrazole. Interestingly 1–4
structurally resemble the dimeric form of the antimony oxide Sb2O3 and its mineral senarmontite.
acids with protic ligands like organosilanediols,12 phenolic pyra-
Introduction
zoles13 and the utility of mixed antimonate–phosphonate clusters
Synthesis and structural characterization of discrete molecular
oxo clusters is an area of active research as clusters are believed
to be the linkers between molecules and materials and help in
understanding the size-related properties of materials.1 Though
metal oxides have been found to be useful in numerous catalytic
processes,2 their insolubility in common organic solvents due to
their polymeric nature limits their potential applications and
the understanding of the chemistry involved with such systems.
In such cases, interaction of oxides with organic ligands proves
to be an efficient method as it helps in solubilizing the oxides
providing a better insight into their solid-state structures and
hence their properties.3
as pro-ligands for synthesizing 3d clusters have also been
reported.14 Self-condensation reactions of organostibonic acids
in the presence of bases have been investigated leading to the
isolation of novel nonanuclear,15 dodecanuclear16,17 and hexa-
decanuclear isopolyoxostibonates.13 It should also be mentioned
here that though chemistry of monoorganostibonic acids is less
investigated, several di- and triorganoantimony oxo clusters have
been synthesized and structurally characterized by Sowerby and
Breunig et al.18
In our continued effort to understand the reactivity of organo-
stibonic acids with various protic ligands and to have a better
insight in to the basic structural units involved in organo-
antimony oxo clusters, reactions of organostibonic acids with
8-hydroxyquinoline and naphthylphenolic pyrazole has been
studied. Details of the synthesis along with the single crystal
X-ray structural characterization of the products obtained are
presented in this manuscript.
The use of antimony oxides as fire retardants4 and in catalysis5
has been well known for decades. In comparison, the chemistry
of organostibonic acids is much less explored despite potential
applications of organoantimony compounds in catalysis6 and
biology.7 Very recently, organostibonic acids have been shown to
bind specifically to B-ZIP proteins at micromolar concentrations,
thereby inhibiting their DNA binding capability and hence could
be used as potential anticancer agents.8 Despite these appli-
cations, due to the amorphous and powdery nature of organo-
stibonic acids, their solid-state structure has been a matter of
debate.9 In this regard, a report by Beckmann et al. on the struc-
ture of the first molecular aryl stibonic acid using bulky substitu-
ents on antimony needs special mention.10 Another interesting
report in the chemistry of organostibonic acids is their ability to
act as inorganic cryptands incorporating transition metals in their
cavity.11 Further, depolymerization reactions of organostibonic
Results and discussion
Reaction of arylstibonic acid (aryl = p-ClC6H4, p-BrC6H4) with
8-hydroxyquinoline in a 1 : 1 stoichiometry was carried out in
refluxing toluene for 6 h. Evaporation of the solvent followed by
crystallization in toluene at room temperature yielded pale
yellow/colourless crystals in moderate yields (Scheme 1). The
products were characterized by standard analytical and spectro-
scopic techniques.
Crystals suitable for single crystal X-ray diffraction were
grown in a week by slow evaporation of toluene. The solid-state
structures of 1 and 2 were found to be isostructural, hence the
structure of 1 (Fig. 1) is considered only for discussion. Com-
pound 1 crystallizes in tetragonal space group I41/a. The struc-
ture of 1 is a highly symmetric adamantyl core consisting of
antimony and oxygen atoms. Each Sb atom lies at the vertex of
School of Chemistry, University of Hyderabad, Hyderabad 500046, A.P.,
India. E-mail: vbsc@uohyd.ernet.in; Tel: +91-40-23134825
†Electronic supplementary information (ESI) available: ORTEP for 2
and 4 and supramolecular interactions for the compounds 3 and 4 are
provided. CCDC 808827–808831. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c2dt30587a
12524 | Dalton Trans., 2012, 41, 12524–12529
This journal is © The Royal Society of Chemistry 2012

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Table 1 Bond length and bond angle comparison between
senarmontite and compounds 1–4 (average bond parameters are given)
Bond length (Å)
Bond angles (°)
Compound
Sb–O
Sb–O–Sb
O–Sb–O
Senarmontite
1.977
1.944
1.936
1.976
1.946
132.50
130.50
130.20
130.76
130.83
95.60
96.43
96.57
96.09
96.19
1
2
3
4
Scheme 1
Fig. 2 Molecular structure of 3 with thermal ellipsoids shown at 30%
probability. A molecule of free ligand and solvent (toluene) that co-crys-
tallized with 3 have been removed for clarity.
while the other nitrogen of the pyrazole ring remains essentially
non-coordinating. The Sb–O bond distances and the angles (Sb–
O–Sb and O–Sb–O) are 1.946 Å, 130.83° and 96.19° respect-
ively. The observed bond parameters again fall in the range as in
the mineral senarmontite. A closer look in to the crystal structure
of 3 revealed interesting N–H⋯O and N–H⋯π supramolecular
interactions (ESI†). Of the N–H⋯O interactions observed in 3,
four are intramolecular N–H⋯O and one is intermolecular. The
intramolecular bond parameters fall in the range 2.479–2.573 Å
with the bond angles ranging from 106.2–108.5°. For the inter-
molecular N10H⋯O1 interaction, the observed bond distance
and angle are 2.199 Å and 146.0° respectively. For the N–H⋯π
(of electron-rich oxyphenyl) interactions observed in 3, the bond
lengths fall in the range from 2.740 to 2.802 Å with the bond
angles ranging from 155.9–162.6°. It should be noted that a
similar kind of N–H⋯O and N–H⋯π interactions are also
observed in 4 (ESI†). For the N–H⋯O interaction the bond dis-
tances range from 2.470–2.655 Å with the bond angles ranging
from 102.8–109.7°. Similarly for the N–H⋯π (of electron-rich
oxyphenyl) interaction, the observed bond distances and angles
fall in the range 2.530–3.169 Å and 153.5–164.4° respectively.20
The formation of the Sb4O6 adamantane-type framework is
interesting considering the fact that the dimeric form of Sb2O3
and its mineral senarmontite are built up of similar frameworks.
Though adamantane-type structures are known for metal oxides
like As4O6 in the solid state,21 similar structures for Bi4O6 have
been proposed as neutral species only in the gas phase.22 So far
Fig. 1 Molecular structure of 1 with thermal ellipsoids shown at 30%
probability.
the tetrahedron with the oxygens at the edges forming an Sb4O6
framework. The ligand chelates to the Sb atom through the O,N-
donor site forming a slightly puckered 5-membered ring. Each
Sb atom is in an octahedral site with O4NC coordination
mode. The Sb–O bond distances and the angles (Sb–O–Sb and
O–Sb–O) are 1.944 Å, 130.50° and 96.43° respectively. Interest-
ingly the bond parameters in 1 and 2 are very similar to the ones
found in senarmontite which is summarized in (Table 1).
Further reactions of arylstibonic acid (aryl = p-ClC6H4,
p-BrC6H4) with H2naphpz19 in 1 : 1 stoichiometry were carried
out in refluxing toluene and the products were crystallized in
toluene by slow evaporation (Scheme 1). Single crystal X-ray
structural elucidation of 3 and 4 revealed the formation of an
adamantane-type structure similar to 1 and 2. The clusters 3 and
4 crystallize in monoclinic space group P21/n and triclinic space
ˉ
group P1 respectively. A free ligand molecule co-crystallized
along with compound 3 (Fig. 2) in the asymmetric unit, where
as in compound 4 two independent adamantane-like molecules
and a free ligand molecule crystallized in the asymmetric unit.
The ligand (O,N,N-donor) chelates to the metal atom through an
O,N-mode resulting in the formation of a six-membered ring
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The reaction mixture was cooled to room temperature and the
solvent was evaporated to yield a colourless product. Standard
analytical and spectroscopic techniques revealed that the colour-
less product was 3 and not 5 as expected. Even using an
organic dehydrating agent like phthalic anhydride could not
convert 3 to 5.
Conclusion
In summary, we report the formation of an unprecedented Sb4O6
adamantane-type framework for the first time in antimony-based
molecular metal-oxo clusters, which can be considered as struc-
tural analogues of the mineral senarmontite. Currently reactions
of organostibonic acids with various other protic ligands are
being explored in an attempt to stabilize novel structural forms
based on Sb–O frameworks.
Fig. 3 Molecular structure of 5 with thermal ellipsoids shown at 30%
probability.
as main group metal-oxo clusters are concerned, adamantane-
type structures are a rarity, though they are quite common in tran-
sition metal chemistry.23 Though adamantane-type M4O6 clus-
ters are reported for main group metals like aluminium,24
gallium,24 indium25 and tin,26 with respect to antimony there are
no reports on such framework though Sb4O6 non-adamantane-
type clusters are known. The closest structurally related molecu-
lar compound is a cage compound MeC(CH2SbO)3 which
consists of a six-membered Sb3O3 ring with the rest of the
adamantane core made of carbons.26b It has to be mentioned
here that an adamantane-like cluster has been proposed as a
possible alternative structure for a product resulting from
the reaction of organoantimony halides with dicyclohexyl
phosphinic acid.27
The molecular structures (1–4) also have close resemblance to
the recently isolated unusual natural polyarsenic compound
Arsenicin A, from the New Caledonian sponge Echinochalina
bargibanti.28 A recent report on the chemical synthesis and the
single crystal X-ray structure elucidation of Arsenicin A is sig-
nificant considering its potential application as bacterial and
fungicidal activities on human pathogenic strains.29 1–4 can be
considered as high oxidation state antimony analogues of
Arsenicin A, with three CH2 groups in the polyarsenic com-
pound replaced by oxygens.
Experimental section
General procedures
Solvents, 8-hydroxyquinoline and common reagents were pur-
chased from commercial sources, whereas p-halophenylstibonic
acids and phenolic pyrazole were synthesized using literature
procedures.9,19 Infrared spectra were recorded on a JASCO-
5300FT-IR spectrometer as KBr pellets. The H and 13C NMR
1
spectra were recorded on a Bruker DRX 400 instrument.
Elemental analysis was performed on a Flash EA Series 1112
CHNS analyser. Compounds 1–5 lose solvent of crystallization
rapidly. Hence the isolated crystals were powdered and subjected
to high vacuum for 1 h before elemental analysis and NMR were
taken. Hence the signals corresponding to solvent of crystalliza-
tion toluene do not appear in the 1H and 13C NMR spectra.
Similarly the elemental analysis also shows a solvent-free CHN
analysis report. Further 1H and 13C NMR spectra are not
reported for compounds 1 and 2 owing to poor solubility in
common organic solvents.
General synthetic method
ˉ
Compound 5 crystallizes in triclinic space group P1 as a side
p-Halophenylstibonic acid and the ligand (8-HQ or H2naphpz)
were taken in 1 : 1 stoichiometry in 50 ml toluene and refluxed
for 6 h using a Dean–Stark apparatus to remove water eliminated
in the reaction as an azeotropic mixture. The clear solution that
was obtained was cooled to room temperature and were filtered.
Molar ratios and weights of reactants used are as follows.
product along with 3 in small quantities (Fig. 3). Structural eluci-
dation revealed the formation of a tetranuclear organoantimony
oxo cluster similar to the product isolated on reaction of aryl-
stibonic acids with phenolic pyrazoles which we have reported
recently.13 In 5 the ligand binds to the metal atoms through both
a chelating (O,N-donor) as well as bridging mode (N,N-donor).
It is of interest to mention here that the adamantane-type struc-
ture which forms initially can lose two molecules of water
leading to the formation of the tetranuclear organoantimony-oxo
cluster (eqn (1)). In fact an independent experiment was carried
out by refluxing 3 in toluene for 6 h and a Dean–Stark apparatus
was used to remove the water molecules formed in the course of
the reaction as an azeotropic mixture.
Compound 1. p-Chlorophenylstibonic acid (0.35 g,
1.23 mmol) and 8-HQ (0.18 g, 1.23 mmol). Crystals suitable for
single crystal X-ray diffraction were obtained by the diffusion
method using filtrate/hexane over the course of a week. Yield of
isolated crystals: 0.20 g (40.80% based on p-chlorophenyl-
stibonic acid). Dec. temp: 240 °C. IR (cm−1, KBr pellet): 3057
w, 2959 w, 1601 m, 1575 m, 1498 s, 1462 s, 1377 m, 1323 m,
1261 s, 1107 m, 796 s, 518 m, 486 m. Elemental analysis:
found: C, 44.73; H, 2.46; N, 3.51. Calc. for C60H40N4O10-
Cl4Sb4: C, 44.87; H, 2.51; N, 3.48%.
ð1Þ
12526 | Dalton Trans., 2012, 41, 12524–12529
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Table 2 X-ray data collection parameters for 1–5
1
2
3
4
5
Formulae
C88H72Cl4N4O10Sb4 C88H72Br4N4O10Sb4 C96H70Cl4N10O11Sb4 C186H138Br8N18O21Sb8 C90H64Cl4N8O8Sb4
Fw, g mol−1
1974.30
Tetragonal
0.20 × 0.16 × 0.10
I41/a
2152.14
Tetragonal
0.22 × 0.14 × 0.10
I41/a
2168.42
Monoclinic
0.24 × 0.18 × 0.12
P21/n
4574.42
Triclinic
0.22 × 0.16 × 0.12
ˉ
P1
2014.29
Triclinic
0.24 × 0.18 × 0.12
ˉ
P1
Cryst syst
Cryst size, mm
Space group
a, Å
b, Å
c, Å
α, °
19.4622(10)
19.4622(10)
20.882(10)
90.0
90.0
90.0
7909.8(10)
4
1.658
100
1.550
19.226(9)
19.226(9)
21.370(19)
90.0
90.0
90.0
7899(9)
4
1.810
100
3.440
20.029(10)
21.285(10)
21.577(10)
90.0
95.200(7)
90.0
9161(7)
4
1.572
17.3569(12)
21.1518(14)
24.9421(17)
79.6580(10)
85.4730(10)
76.5070(10)
8753.0(10)
2
11.1209(9)
11.5866(10)
17.2087(14)
83.2620(10)
81.3270(10)
69.8120(10)
2052.3(3)
1
β, °
γ, °
v, Å3
Z
Dcalcd Mg m−3
T, K
1.736
100
3.113
1.630
100
1.495
100
1.349
μ, mm−1
F(000)
θ range, °
No. of. refln colled
Completeness to θ max (%)
No. of. indep refln/Rint
GooF (F2)
3920
1.43 to 25.08
36 644
99.6
3503/0.032
1.068
4208
4304
1.35 to 25.00
84 836
100.0
16 131/0.091
1.084
4472
1.21 to 25.00
84 882
99.7
30 737/0.032
1.062
996
1.20 to 25.00
19 965
99.8
7219/0.054
1.109
1.42 to 25.13
26 764
99.7
3472/0.047
1.070
R1 (F) (I > 2σ(I))
0.028
0.076
0.050
0.144
2.237/−1.289
0.048
0.119
1.295/−0.682
0.037
0.100
2.955/−3.023
0.048
0.103
1.39/−1.038
wR2 (F2) (All data)
Largest diff peak/hole, e Å−3 1.080/−0.591
Table 3 Bond length (Å) and bond angle (°) parameters for compounds 1–3
1
2
3
Sb1–O1
Sb1–O2
Sb1–O3
Sb1–N1
2.065(2)
Sb1–O1
Sb1–O2
Sb1–O3
Sb1–N1
2.046(5)
1.933(4)
1.933(3)
2.222(6)
2.114(7)
132.70(2)
126.00(5)
92.73(16)
93.67(17)
92.20(2)
89.60(2)
Sb1–O1
Sb1–O2
Sb1–O3
Sb1–O7
Sb1–N1
Sb2–O5
Sb2–O6
Sb2–O8
Sb2–N3
Sb3–O4
Sb3–O9
Sb3–N5
Sb4–O6
Sb4–O2
Sb4–O10
Sb4–N7
Sb1–C14
Sb1–O3–Sb2
Sb1–O1–Sb3
Sb1–O2–Sb4
O1–Sb1–O2
O2–Sb1–O3
O2–Sb4–O6
O2–Sb1–O7
O5–Sb3–O4
O7–Sb1–N1
N1–Sb1–C14
C14–Sb1–O3
1.951(3)
1.948(3)
1.960(3)
2.024(3)
2.206(4)
1.958(3)
1.939(3)
2.017(3)
2.196(4)
1.945(3)
2.012(3)
2.196(4)
1.931(3)
1.957(3)
2.017(3)
2.192(4)
2.116(5)
132.72(17)
126.38(16)
133.66(16)
91.11(13)
92.17(12)
102.36(13)
86.54(12)
91.59(12)
79.10(14)
92.52(17)
91.83(16)
1.948(19)
1.938(13)
2.238(2)
Sb1–C10
2.133(3)
Sb1–C10
Sb1–O2a–Sb1a
Sb1–O3–Sb1b
O2–Sb1–O2a
O2–Sb1–O3
C10–Sb1–O2
C10–Sb1–N1
132.88(10)
125.93(14)
92.15(7)
103.99(8)
92.31(10)
89.7(10)
Sb1–O2a–Sb1a
Sb1–O3–Sb1b
O2–Sb1–O2a
O2–Sb1–O3
C10–Sb1–O2a
C10–Sb1–N1
acid). Dec. temp: 245 °C. IR (cm−1, KBr pellet): 3061 w,
2964 m, 1604 m, 1577 m, 1498 s, 1460 s, 1377 m, 1325 m,
1261 s, 1093 m, 800 s, 482 m. Elemental analysis: found: C,
40.38; H, 2.21; N, 3.09. Calc. for C60H40N4O10Br4Sb4: C,
40.40; H, 2.26; N 3.14%.
Compound 2. p-Bromophenylstibonic acid (0.40 g,
1.22 mmol) and 8-HQ (0.17 g, 1.22 mmol). Crystals suitable for
single-crystal X-ray diffraction were obtained by the diffusion
method using filtrate/hexane over the course of a week. Yield of
isolated crystals: 0.20 g (37.0% based on p-bromophenylstibonic
This journal is © The Royal Society of Chemistry 2012
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Table 4 Bond length (Å) and bond angle (°) parameters for
compounds 4–5
1527 s, 1473 m, 1390 m, 1253 m, 1224 m, 1136 m, 1084 s,
1006 m, 887 m, 808 m, 773 m, 729 m, 609 m, 580 m, 480 m.
1H NMR (400 MHz, CDCl3) δ: 6.87–7.91 ppm (m) for aromatic
protons. 13C NMR (100 MHz, CDCl3): δ 155.84, 150.51,
149.23, 134.91, 134.46, 130.53, 129.05, 128.75, 128.24, 127.77,
127.31, 126.54, 126.02, 125.59, 125.31, 124.80, 122.91, ppm.
Elemental analysis: found: C, 49.71; H, 2.51; N, 6.15. Calc. for
C76H48N8O8Cl4Sb4: C, 49.88; H, 2.64; N, 6.12%.
4
5
Sb1–O1
Sb1–O2
Sb1–O3
Sb1–O7
Sb1–N1
Sb2–O5
Sb2–O6
Sb2–O8
Sb2–N3
Sb3–O1
Sb3–O4
Sb3–O9
Sb3–N5
Sb4–O6
Sb4–O10
Sb4–N7
Sb1–C14
Sb1–O2–Sb2
Sb1–O3–Sb4
Sb1–O1–Sb3
Sb4–O4–Sb3
O1–Sb1–O2
O2–Sb1–O3
C14–Sb1–N1
O3–Sb4–O4
O2–Sb1–O7
O7–Sb1–N1
1.941(3)
1.945(3)
1.957(3)
2.024(3)
2.197(3)
1.954(3)
1.932(3)
2.029(3)
2.213(4)
1.932(3)
1.946(3)
2.025(3)
2.207(3)
1.943(3)
2.009(3)
2.210(3)
2.129(4)
132.52(16)
133.67(14)
127.30(15)
133.99(15)
91.69(12)
92.64(12)
88.82(15)
91.71(12)
85.51(12)
79.07(13)
Sb1–O2
Sb1–O1*
Sb1–N1
Sb1–C14
Sb1–O3
Sb1–N4
Sb2–O1
Sb2–O2
1.953(3)
1.933(3)
2.146(4)
2.117(5)
2.000(3)
2.141(4)
1.948(3)
1.943(3)
1.992(3)
2.264(4)
2.116(4)
120.82(17)
131.96(18)
95.82(14)
99.73(14)
85.11(15)
93.14(14)
81.86(15)
94.34(17)
X-ray crystallography
Sb2–O4
Sb2–N2
Sb2–N3
Important crystal data parameters are given in Table 2. Selected
bond lengths and bond angles for 1–5 are given in Tables 3 and
4. Single crystal X-ray data collection for 1–5 were carried out at
100(2) K on a Bruker Smart Apex CCD area detector system
(λ(Mo Kα) = 0.71073 Å) with a graphite monochromator. The
data were reduced using SAINTPLUS. The structures were
solved using SHELXS-97 and refined using SHELXS-97.30 All
non-hydrogen atoms were refined anisotropically. Some of the
structures have residual electron density owing to solvent of
crystallization which could not be properly fixed. In compound
1, solvent of crystallization toluene molecules were constrained
to be hexagonal using the AFIX 66 command. In compounds 3,
4 and 5, solvent voids were noticed but we were unable to locate
the corresponding solvent of crystallization. These solvent con-
tributions were removed by the SQUEEZE31 command in the
PLATON program. In compound 4, the residual electron density
is also due to a heavily disordered bromine atom (Br2) which has
not been modeled.
Sb1–O2–Sb2
Sb2–O1–Sb1*
O1–Sb2–O2
O1*–Sb1–O2
O2–Sb1–N4
O1*–Sb1–O3
O3–Sb1–N1
C14–Sb1–O2
Compound 3. p-Chlorophenylstibonic acid (0.35 g,
1.23 mmol) and H2naphpz (0.26 g, 1.23 mmol). Colorless crys-
tals were isolated over the course of a week by slow evaporation
of filtrate (toluene). Yield: 0.24 g (37.5% based on p-chlorophenyl-
stibonic acid). Dec. temp: 260 °C. IR (cm−1, KBr pellet):
2961 w, 1624 w, 1562 m, 1473 m, 1388 m, 1261 s, 1087 s,
Acknowledgements
VB thanks the Department of Science and Technology for a
financial grant under the SERB programme. AKJ thanks the
CSIR for a fellowship.
1
1016 m, 887 m, 804 s, 486 m. H NMR (400 MHz, CDCl3)
a broad signal at δ: 8.98 ppm (–OH), δ 6.90–8.59 ppm (m) for
aromatic protons; 13C NMR (100 MHz, CDCl3): δ 151.88, 149.
80, 149.29, 134.90, 134.56, 134.16, 129.14, 128.83, 127.84,
127.73, 127.34, 126.53, 125.73, 125.45, 125.20, 124.77,
122.99 ppm. Elemental analysis: found: C, 51.36; H, 3.12; N
6.65. Calc. for C89H62N10O11Cl4Sb4: C, 51.48; H, 3.01; N,
6.74%.
Notes and references
1 (a) Clusters and Colloids: From Theory to Applications, ed. G. Schmidt,
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2 (a) W. Kaminsky, Catal. Today, 1994, 20, 257; (b) H. Sinn and
W. Kaminsky, Adv. Organomet. Chem., 1980, 18, 99; (c) H.-H. Brintzinger,
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1995, 500, 149.
3 (a) C. N. R. Rao and B. Raveau, Transition Metal Oxides, VCH,
Weinheim, 1995; (b) W. J. Thomas, Principles and Practice of Hetero-
geneous Catalysis, VCH, Weinheim, 1997; (c) G. Ertl, H. Knözinger and
J. Weitkamp, Handbook of Heterogeneous Catalysis, VCH, Weinheim,
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4 (a) F. Li, J. T. Wang, B. G. Wang and J. J. Song, J. Compos. Mater.,
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Compound 4. p-Bromophenylstibonic acid (0.35 g,
1.06 mmol) and H2naphpz (0.22 g, 1.06 mmol). Colorless crys-
tals were isolated over the course of a week by slow evaporation
of filtrate (toluene). Yield: 0.26 g (45.3% based on p-bromophe-
nylstibonic acid). Dec. temp. 270 °C. IR (cm−1, KBr pellet):
2962 w, 1633 w, 1562 m, 1475 m, 1390 m,1261 s, 1086 s,
1
1022 m, 885 m, 802 s, 478 m. H NMR (400 MHz, CDCl3) a
broad signal at δ 9.20 ppm (–OH), δ 6.74–8.62 ppm (m) for aro-
matic protons; 13C NMR (100 MHz, CDCl3): δ 151.95,149.26,
134.91,134.44, 130.58, 129.05, 128.79, 127.81, 127.30, 126.54,
125.64, 125.46, 125.31, 125.18, 124.78, 123.98, 123.03 ppm.
Elemental analysis: found: C, 46.17; H, 2.58; N, 5.79. Calc. for
C
165H114Br8N18O21Sb8: C, 46.11; H, 2.67; N, 5.87%.
5 (a) S. E. Golunski, Appl. Catal., 1989, 48, 123; (b) U. A. Schubert,
F. Anderle, J. Spengler, J. Zuhlke, H. J. Eberle, R. K. Grasselli and
H. Knozinger, Top. Catal., 2001, 15, 195; (c) B. Pillep, P. Behrens,
U. A. Schubert, J. Spengler and H. Knozinger, J. Phys. Chem. B, 1999,
103, 9595; (d) S. I. Woo, B. O. Kim, H. S. Jun and H. N. Chang, Polym.
Compound 5. Obtained as a side product along with 3. Yield:
0.12 g (21.2% based on p-chlorophenylstibonic acid) Dec. temp:
280 °C. IR (cm−1, KBr pellet): 3341 m, 3055 w, 1664 w, 1562 s,
12528 | Dalton Trans., 2012, 41, 12524–12529
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