Isolation of tetranuclear organoantimony oxo clusters and hexa-decanuclear polyoxostibonates

Article abstract of DOI:10.1021/om900942q

Reaction of phenolic pyrazolyl ligands with arylstibonic acids afforded two novel tetranuclear clusters [(p-X-C₆H₄Sb) ₄(O)₅(OH)₂(HPhPzR¹)₄] (where X = Cl, R¹ = Ph (1);

Full text of DOI:10.1021/om900942q

Organometallics 2010, 29, 1137–1143 1137
DOI: 10.1021/om900942q
Isolation of Tetranuclear Organoantimony Oxo Clusters and
Hexa-decanuclear Polyoxostibonates
Ananda Kumar Jami, M. Santhana Raj Prabhu, and Viswanathan Baskar*
School of Chemistry, University of Hyderabad, Hyderabad 500046, India
Received October 27, 2009
Reaction of phenolic pyrazolyl ligands with arylstibonic acids afforded two novel tetranuclear clusters
[(p-X-C6H4Sb)4(O)5(OH)2(HPhPzR1)4] (where X = Cl, R1=Ph (1); X=Br, R1=Ph (2); X=Br, R1=
t-Bu (3)) and [(p-Br-C6H4Sb)4(PhPz)4(O)4] (4). Depending on the steric bulk of the group present on the
pyrazole ring, either one (1-3) or two (4) of the ring nitrogens have been found to coordinate to the metal
atoms. Remarkably, when 3,5-DMPz is reacted with arylstibonic acid, hexa-decanuclear polyoxostibo-
nates [(p-X-C6H4Sb)16(O)28(OH)8](3,5-DMPz)6 (X=Cl (5), Br (6)) have been isolated.
Introduction
arylstibonic acid,7 which crystallized as a dimer in the solid
state with the geometry around the Sb atoms being trigonal
bipyramidal, as predicted by earlier studies. The reactivity of
organostibonic acid toward strong acids and bases has been
investigated, unraveling the unusual reactivity of organosti-
bonic acid compared to phosphorus and arsenic analogues.8
Further, the ability of organostibonic acid to act as an
inorganic cryptand incorporating transition metal and alkali
metals in their cavities has also been reported recently.9 The
isolation of these reverse-keggin-type structures draws inter-
Synthesis, structure, and reactivity of organostibonic
acids1 are less studied compared to the analogous com-
pounds of phosphorus2 and arsenic3 despite potential appli-
cations of organoantimony compounds in the field of
catalysis4 and biology.5 As arylstibonic acids are poorly
soluble in most of the common organic solvents, their
structures in the solid state have been a matter of debate.
Earlier reports by Schmidt, Doak, and Bowen using mole-
121
cular weight measurements1 and Sb Mossbauer spectro-
€
esting parallels to well-established POM chemistry reported
scopy6 suggested that arylstibonic acids exist with a high
degree of association in the solid state and that the geo-
metry around the Sb atom is trigonal bipyramidal. Recently
Beckmann et al. reported the controlled hydrolysis of 2,6-
Mes2C6H3SbCl4 under basic conditions, leading to the iso-
lation and structural characterization of the first molecular
10
by Muller, Pope,11 and others.12 Further reactions of
€
organostibonic acids with phosphonic acid13 and silanols14
have been carried out, leading to the isolation of novel
organoantimony oxo clusters. It is of interest to mention
that an organoantimony phosphonate cluster has been
shown to act as a proligand for synthesizing multinuclear
cobalt clusters using solvothermal reaction conditions. Anti-
mony oxo clusters have also been studied in the gas phase or
condensed phase by mass spectrometry,15 and it has been
*Corresponding author. E-mail: vbsc@uohyd.ernet.in. Phone: þ91-
40-66794825. Fax: þ91-40-23012460.
(1) (a) Schmidt, H. Liebigs Ann. Chem. 1920, 421, 174. (b) Doak, G. O.;
Steinman, H. G. J. Am. Chem. Soc. 1946, 68, 1987. (c) Doak, G. O. J. Am.
Chem. Soc. 1946, 68, 1991.
(7) Beckmann, J.; Finke, P.; Hesse, M.; Wettig, B. Angew. Chem. Int.
Ed. 2008, 47, 9982.
(2) (a) Freedman, L. D.; Doak, G. O. Chem. Rev. 1957, 57, 479.
(b) Freedman, L. D.; Doak, G. O. J. Org. Chem. 1964, 29, 2450. (c) Arnold,
G. B.; Hamilton, C. S. J. Am. Chem. Soc. 1941, 63, 2637. (d) Freedman, L. D.;
Doak, G. O. J. Am. Chem. Soc. 1955, 77, 6221. (e) Rabinowitz, R. J. Am.
Chem. Soc. 1960, 82, 4564. (f) Henderson, W.; Alley, S. R. J. Organomet.
Chem. 2001, 637, 216. (g) Murugavel, R.; Choudhury, A.; Walawalkar, M .G.;
Pothiraja, R.; Rao, C. N. R. Chem. Rev. 2008, 108, 3549. (h) Chandrasekhar, V.;
Kingsley, S. Angew. Chem., Int. Ed. 2000, 39, 2320. (i) Maheswaran, S.;
Chastanet, G.; Teat, S. J.; Mallah, T.; Sessoli, R.; Wernsdorfer, W.; Winpenny,
R. E. P. Angew. Chem., Int. Ed. 2005, 44, 5044. (j) Tolis, E. I.; Helliwell, M.;
Langley, S.; Raftery, J.; Winpenny, R. E. P. Angew. Chem., Int. Ed. 2003, 42,
3804. (k) Khan, M. I.; Meyer, L. M.; Haushalter, R. C.; Schweitzer, A. L.;
Zubieta, Z.; Dye, J. L. Chem. Mater. 1996, 8, 43. (l) Clearfield, A. Curr. Opin.
Solid State Mater. Sci. 1996, 1, 268.
(8) (a) Beckmann, J.; Hesse, M. Organometallics 2009, 28, 2345.
(b) Beckmann, J.; Heck, T.; Takahashi, M. Organometallics 2007, 26, 3633.
(9) Baskar, V.; Shanmugam, M.; Helliwell, M.; Teat, S. J.; Winpenny,
R. E. P. J. Am. Chem. Soc. 2007, 129, 3042.
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Kluwer Academic Publishers: Dordrecht, The Netherlands, 2003; p 297.
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(b) M€uller, A.; Shah, S. Q. N.; Bogge, H.; Schmidtmann, M.; Kogerler, P.;
Hauptfleish, B.; Leiding, S.; Wittler, K. Angew. Chem., Int. Ed. 2000, 39,
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1614. (c) M€uller, A.; Beckmann, E.; Bogge, H.; Schmidtmann, M.; Dress, A.
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(11) Pope, M. T. Poloxo Anions: Synthesis and Structure. In Com-
prehensive Coordination Chemistry II; McCleverty, J., Meyer, T. J., Eds.;
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Z.-M. Chem.;Eur. J. 2008, 14, 4093. (b) Xie, Y.-P.; Ma, J.-F.; Yang, J.; Liu,
Y.-Y.; Ma, J.-C.; Su, M.-Z. Eur. J. Inorg. Chem. 2009, 2144. (c) Lloyd, N. C.;
Morgan, H. W.; Nicholson, B. K.; Ronimus, R. S. J. Organomet. Chem.
2008, 693, 2443.
(12) (a) Borras-Almenar, J. J., Coronado, E., Muller, A., Pope, M. T.,
Cronin, L., Eds. Polyoxometalate Molecular Science; Kluwer: Dordrecht,
The Netherlands, 2003; Vol. 98. (b) Long, D.-L.; Burkholder, E.; Cronin, L.
Chem. Soc. Rev. 2007, 36, 105.
(13) Ali, S.; Baskar, V.; Muryn, C. A.; Winpenny, R. E. P. Chem.
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r
2010 American Chemical Society
Published on Web 02/03/2010
pubs.acs.org/Organometallics

1138 Organometallics, Vol. 29, No. 5, 2010
Jami et al.
Chart 1
Scheme 1
reported that at room temperature the stable solid phase of
Sb2O3 is the cubic senarmontite, which contains a Sb4O6
molecule,16 whereas the high-temperature orthorhombic
phase valentinite has a polymeric sheet built up of eight-
membered Sb4O4 rings.17 Generally in these clusters anti-
mony atoms are present in both the III and V state of
oxidation, but at higher oxygen concentrations it has been
shown that the formation of oxide clusters containing anti-
mony atoms solely in the V state of oxidation is favored.18
Synthesis and structural characterization of the first poly-
oxoantimonate [Sb8O12(OH)20]4- devoid of any Sb-C
bonds were reported by Yagasaki et al,19 which was followed
by the isolation of polyoxoantimonates built up from an
Sb4O16 core.20 Despite the rich structural variations and
utility of organoantimony oxo clusters, the reactions of
arylstibonic acid with ligands containing mixed N,O-donor
or N,N-donor atoms have not been investigated.
Herein, we report the synthesis and structure of the
products (1-6) obtained on the reaction of organostibonic
acid with pyrazolyl ligands having substitution at the 3,5-
positions. The ligands chosen are depicted in Chart 1. These
ligands have been utilized for synthesizing multinuclear
transition metal clusters, some of which possess interesting
magnetic properties.21
toluene, and xylene. 1H NMR spectra (in CDCl3 solution for
2, 3, 5, and 6) showed the appearance of multiplets from 6.7
to 7.8 ppm, corresponding to aromatic groups present. For
compounds 5 and 6 signals at 1.3 ppm are assigned to
pyrazole methyl groups. IR spectra of the compounds
(except for 4) exhibit broad peak around 3300-3400 cm-1
,
indicating the presence of hydroxyl groups.
The crystal structure of 1 (X = Cl) and 2 (X = Br) revealed
the formation of a tetranuclear organoantimony oxo cluster,
[(p-X-C6H4Sb)4(O)5(OH)2(HPhPzR1)4]. Clusters 1 and 2
crystallize in triclinic space group P1 with varying solvent
of crystallization, namely, toluene in 1 and chloroform in 2.
Since the cluster cores of 1 and 2 are identical, the structure of
1 is considered for discussion (Figure 1). It can be visualized
as being build up of two Sb3O3 rings, which are nearly
perpendicular to each other, sharing a Sb2O unit. Four
ligands were found coordinating to the metal atoms in a
chelating mode of binding through the phenolic oxygen and
the nitrogen of the pyrazole ring, while the other N atom is
noncoordinating. All Sb atoms lie at the center of an
octahedron with the CO4N coordination mode. Two sets
of Sb atoms are found in the cluster. The first set of Sb atoms,
Sb1 and Sb4, are connected between themselves and to the
two other Sb atoms by an oxo bridge; the fourth coordina-
tion is to the deprotonated oxygen of the phenolic group,
with the fifth and the sixth coordination to the pyrazole
nitrogen and the halophenyl carbon completing the primary
coordination sphere. The other set of two Sb atoms are
connected to the neighboring Sb atoms by oxo bridges, with
coordination from the phenolic oxygen and the fourth and
fifth coordinations from the nitrogen, the carbon of the
pyrazole, and the halophenyl ring, respectively. The sixth
coordination is to a terminal O atom, which on the basis of
charge neutrality conditions is considered to be present as a
terminal hydroxyl group. The Sb-O distances fall in the
Results and Discussion
The general synthetic methodology adopted (Scheme 1)
and the standard spectroscopic and analytical data for 1-6
are given in the Experimental Section. Crystals suitable for
single-crystal X-ray diffraction for 1-6 were obtained either
by slow evaporation of toluene or by a diffusion method
using dichloromethane or chloroform/hexane. Crystals of 1
and 4 had poor solubility in common organic solvents, while
2, 3, 5, and 6 were soluble in dichloromethane, chloroform,
˚
(16) Reinicke, R. Z. Elektrochem. 1935, 41, 23.
range 1.928(3) to 1.965(2) A. The phenolic oxygen to Sb
(17) Buerger, M. J.; Hendricks, S. B. J. Phys. Chem. 1937, 5, 600.
(18) (a) Kaiser, B.; Bernhardt, T. M.; Kinne, M.; Rademann, K.;
Heidenreich, A. J. Chem. Phys. 1999, 110, 1437. (b) Optiz-Coutureau, J.;
Fielicke, A.; Kaiser, B.; Rademann, K. Phys. Chem. Chem. Phys. 2001, 3,
3034.
(19) Nakano, H.; Ozawa, Y.; Yagasaki, A. J. Am. Chem. Soc. 1995,
117, 12007.
˚
distance falls in the range 2.000(3) to 2.005(3) A. The Sb-N
˚
distances fall in the range 2.170(3) to 2.187(3) A. The Sb-O
(hydroxyl) distances fall in the range 1.942(3) to 1.960(2) A.
˚
Cluster 1 cocrystallizes with a molecule of the ligand and
toluene in the crystal lattice. It should be mentioned here that
the tetranuclear clusters (1 and 2) are similar to a recently
reported triorganoantimony phosphinate cluster, [(Ph3Sb)2-
(μ-O)(cycPO2)2],22 except that in the present case P atoms
have been replaced by Sb atoms, leading to the formation of
a tetranuclear cluster. The Sb-O distances in 1 are shorter
than the phenolic oxygen to Sb distance, similar to the
(20) Kusaka, Y.; Ozawa, Y.; Yagasaki, A. Inorg. Chem. 2001, 40,
2634.
(21) (a) Tanase, S.; Aromi, G.; Bouwman, E.; Kooijman, H.; Spek, A.
L.; Reedijk, J. Chem. Commun. 2005, 3147. (b) Bai, Y.-L.; Tao, J.;
Wernsdorfer, W.; Huang, R.-B.; Zheng, L.-S. J. Am. Chem. Soc. 2006, 128,
16428. (c) Viciano-Chumillas, M.; Tanase, S.; Mutikainen, I.; Turpeinen, M.;
de Jongh, L. J.; Reedijk, J. Inorg. Chem. 2008, 47, 5919. (d) Aromi, G.;
Bouwman, E.; Burzuri, E.; Carbonera, C.; Krzystek, J.; Luis, F.; Sehlegel, C.;
Slageren, J. V.; Tanase, S.; Teat, S. J. Chem.-Eur. J. 2008, 14, 11158.
(e) Bai, Y.-L.; Tangoulis, V.; Huang, R.-B.; Zheng, L.-S.; Tao, J. Chem.-Eur.
J. 2009, 15, 2377.
(22) Chandrasekhar, V.; Thirumoorthi, R. Organometallics 2009, 28,
2637.

Article
Organometallics, Vol. 29, No. 5, 2010 1139
Figure 1. Molecular structure of 1with thermal ellipsoids shown at 30% probability. The p-Cl-phenyl group on the Sb atoms and a molecule
˚
of free ligand that cocrystallized with 1 have been removed for clarity. Selected bond lengths (in A) and bond angles (in deg): Sb1-O1 =
1.928(2), Sb1-O3=1.965(2), Sb1-O5 = 1.953(2), Sb1-O6 = 2.022(2), Sb2-O1=1.948(2), Sb2-O2 = 1.949(2), Sb2-O7 = 2.005(2),
Sb2-O10=1.962(2), Sb3-O2=1.947(2), Sb3-O3 = 1.958(2), Sb3-O4 = 1.938(2), Sb3-O8 = 2.025(2), Sb4-O4 =1.942(2), Sb4-O5 =
1.961(2), Sb4-O11 = 1.960(2), Sb4-O9 = 2.000(2), Sb1-N1 = 2.187(3), Sb2-N3 = 2.186(3), Sb3-N5 = 2.170(3), Sb4-N7 = 2.173(3),
O1-Sb1-O5 = 97.30(9), O1-Sb1-O3 = 94.60(9), O5-Sb1-O3 = 92.33(9), O1-Sb2-O2 = 92.71(9), O2-Sb3-O3 = 93.43(9),
O4-Sb4-O5=92.66(9), O1-Sb1-N1=84.40(10), O4-Sb3-N5=85.13(9), Sb1-O1-Sb2=137.01(12), Sb1-O5-Sb4=132.71(12),
Sb3-O3-Sb1 = 130.26(11), Sb3-O4-Sb4 = 134.47(12), Sb3-O2-Sb2 = 134.85(12).
triorganoantimony phosphinate cluster, where the μ-O to Sb
distances have been reported to be shorter than the Sb-O
distances from the phosphinate ligands. The Sb-O (hydro-
xyl) distances in 1 also fall in the range previously reported in
the literature.22
cluster. In the case of 1-3 only one N atom of the pyrazole
ring participates in binding to the Sb atom, while the other N
is noncoordinating. When a sterically less demanding group
is present on the 5-position of the pyrazole ring, it acts as a
bridging ligand, coordinating through both ring nitrogens,
leading to the formation of a tetranuclear cluster (4) struc-
turally different from 1-3. This observation prompted us to
investigate the reaction of arylstibonic acids with pyrazole
devoid of any oxo donor substitution on the 3- and 5-posi-
tions. Hence the reaction of arylstibonic acid with 3,5-di-
methylpyrazole (3,5-DMPz) was carried out following simi-
lar procedures to that of 1-4. Single-crystal X-ray studies for
5 and 6 revealed the formation of hexa-decanuclear organo-
antimony oxo clusters [(p-X-C6H4Sb)16(O)28(OH)8](3,5-
DMPz)6 (X=Cl (5), Br (6)), which crystallize in monoclinic
space group P2(1)/n. Since 5 and 6 are isostructural, the
structure of 5 is considered for discussion (Figure 3). The
geometry around each antimony is octahedral, with a O5C
coordination mode. Four Sb3O3 and two Sb2O2 rings are
found in 5, which are held together by oxo bridges. Each
Sb3O3 ring is capped by a μ3-oxygen, reminiscent of O-
capped clusters previously reported for similar organotin
compounds.23 The Sb3O3 units along with the capping μ3-
oxygen atom present in 5 can also be visualized as a cube with
a vertex missing. Of the 36 oxo groups present in 5, 28 are μ2-
bridging, while the other eight oxygen atoms are μ3-bridging
to the metal centers. These eight μ3-bridging oxygen atoms
are considered to be part of hydroxyls for charge neutrality
considerations. The polyoxostibonate core is encapsulated
Single-crystal X-ray elucidation studies for 3 revealed the
formation of a tetranuclear organoantimony oxo cluster,
isostructural to 1 and 2. Hence the change in the group
present at the 5-position of the pyrazolyl ligand from a
phenyl to a tert-butyl had no effect on the structure of the
product on reaction with arylstibonic acids. In further efforts
to understand the steric effects on the reaction products, we
carried out the reaction of p-Br-phenylstibonic acid with
3-(2-hydroxyphenyl)pyrazole. X-ray studies of the resulting
product revealed the formation of a neutral tetranuclear
organoantimony oxido cluster, [(p-Br-C6H4Sb)4(PhPz)4-
(O)4] (4), which crystallizes in monoclinic space group
P2(1)/n (Figure 2). Coordination geometry around each Sb
atom is octahedral. All four Sb atoms lie in almost the same
plane bridged through oxo groups, leading to the formation
of an eight-membered Sb4O4 ring. The structure of 4 can be
visualized as being built from two Sb2O units held together
by two oxo bridges. Each Sb2O unit is a part of two Sb2ON2-
containing five-membered rings, which are nearly perpendi-
cular to each other. Each Sb2O unit consists of two dianionic
ligands with each ligand exhibiting both chelating (O,N-
donors) and bridging modes of binding (N,N-coordination
mode). The Sb-O distances fall in the range from 1.936(3) to
˚
1.955(3) A. The phenolic oxygen to Sb distance falls in the
˚
range 1.981(3) to 2.006(3) A. The Sb-N distances fall in the
range 2.111(3) to 2.216(4) A.
˚
(23) (a) Day, R. O.; Holmes, J. M.; Chandrasekhar, V.; Holmes, R.
R. J. Am. Chem. Soc. 1987, 109, 940. (b) Chandrasekhar, V.; Baskar, V.;
Vittal, J. J. Am. Chem. Soc. 2003, 125, 2392.
Arylstibonic acid when reacted with a phenolic pyrazolyl
ligand leads to the formation of a novel organoantimony oxo

1140 Organometallics, Vol. 29, No. 5, 2010
Jami et al.
low yields as a byproduct in a reaction involving nickel(II)
salts and arylstibonic acid in the presence of NaOMe as base
under solvothermal reaction conditions.9 The structure re-
vealed that the repeat unit consists of aggregates [(RSb)16-
O28(OH)8] coordinated to four Naþ ions. In another recent
report, it has been shown that RSbO3H2 preferentially forms
aggregates of the type [H8(RSb)12O28] when crystallized from
NH3/HOAc.24 Under basic conditions these aggregates have
been shown to act as precursors for formation of isopolyoxo-
stibonates [Na2H9(RSb)12O30]-. Despite several attempts to
isolate aggregates [H8(RSb)12O28], polyoxostibonates have
been crystallized only in the presence of alkali metal cations
such as Naþ ions. Even when no sodium was used in the
reaction, under basic conditions the arylstibonic acid has been
reported to form complexes with Naþ ions from glassware,
leading to isolation of alkali metal coordinated isopolyoxo-
stibonates. But in our study, in the presence of mildly basic 3,5-
DMPz ligands, aggregates of the type [(RSb)16O28(OH)8]
have been isolated in the absence of any complexing alkali
or transition metal ion. This is remarkable since [(RSb)16O28-
(OH)8] canbevisualized as a naked inorganiccryptandassem-
bled by self-condensation of RSbO3H2 by elimination of
water molecules. Further, parallels to classical POM chemis-
try need mentioning, as 5 and 6 resemble a type of POM
cluster that is rare among otherwise rich structural variations
that has been reported. Hexadecanuclear core containing
POMs are a rarity, and only a few molybdenum-25 and vana-
dium26-containing clusters are reported.
Figure 2. Molecular structure of 4 with thermal ellipsoids
˚
shown at 30% probability. Selected bond lengths (in A) and
bond angles (in deg): Sb1-O1=1.948(19), Sb1-O4=1.945(19),
Sb1-N1=2.216(2), Sb1-N4=2.113(2), Sb2-O1=1.934(19),
Sb2-O2=1.947(19), Sb2-N5=2.150(2), Sb2-N8=2.166(2)
Sb3-O2=1.942(19), Sb3-O3=1.948(19), Sb3-N6=2.110(2),
Sb3-O7=1.985(2), Sb4-O3=1.940(19), Sb4-O4=1.953(19),
Sb4-N2=2.163(2), Sb4-N3=2.146(2), O4-Sb1-O1=94.82(8),
O1-Sb2-O2 = 100.86(8), O2-Sb3-O3 = 95.53(8), O3-Sb4-
O4 = 101.88(8), Sb2-O1-Sb1 = 132.21(10), Sb3-O2-Sb2 =
120.91(10), Sb1-O4-Sb4=120.63(10), Sb4-O3-Sb3=131.58(10).
Conclusion
In summary, reaction of a phenolic pyrazolyl ligand with
arylstibonic acid has led to the isolation of two novel tetra-
nuclear organoantimony oxido clusters. Depending on the
steric bulk of the group present on the 5-position of the
pyrazole ring, either one or two of the ring N atoms have
been found to coordinate to the metal atoms. Remarkably,
when 3,5-DMPz is reacted with arylstibonic acids, hexa-
decanuclear polyoxostibonates have been isolated.
by 16 p-Cl-phenyl groups. A further three molecules of 3,5-
DMPz crystallize in the asymmetric unit; hence six molecules
of 3,5-DMPz crystallize along with the neutral hexa-decan-
uclear polyoxostibonate. The Sb-O distances in 5 fall in the
˚
Experimental Section
range from 1.931(5) to 2.149(5) A. The Sb-C distances fall in
˚
the range 2.107(8) to 2.129(10) A.
General Procedures. Solvents, 3,5 DMPz, and common re-
agents were purchased from commercial sources and used as
such. p-Halophenylstibonic acids and phenolic pyrazoles were
synthesized using literature procedures.1,27 Infrared spectra
were recorded on a JASCO-5300FT-IR spectrometer as KBr
The structure of 5 can also be visualized in polyhedral
arrangements. Each Sb lies at the center of the polyhedron;
three such polyhedra share two of its edges with the neighbor-
ing polyhedron, forming a triad. Each triad shares two edges
with its neighboring triad on both sides, forming a cyclic
framework built up of four triads. Further, two polyhedra
share an edge and form dimers. Two such dimers are present in
5; one above and the other below the central polyhedral
arrangement formed by the four triads, leading to the forma-
tion of a closed-cage-like framework. The dimers are con-
nected to the triads by three corner- and one edge-sharing
polyhedra, resulting in the formation of eight triangular and
four pentagonal faces in the cluster. It is well known that
polymeric arylstibonic acids are insoluble white powders, and
hence structural information is limited. Structures 5 and 6 can
be considered as partially anhydrous forms of arylstibonic
1
pellets. H and 13C NMR spectra were recorded on a Bruker
DRX 400 instrument. Elemental analysis was performed on a
Flash EA Series 1112 CHNS analyzer.
General Synthetic Method. p-Halophenylstibonic acid and the
ligand were taken in 1:1 stoichiometry in 50 mL of 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,
filtered, and evaporated to obtain the crude products. Molar
ratios and weights of reactants used are as follows.
(24) Clark, C. J.; Nicholson, B. K.; Wright, C. E. Chem. Commun.
2009, 923.
€
acid. Although an earlier literature report based on Mossbauer
€
(25) (a) Long, D.-L.; Kogerler, P.; Farrugia, L. J.; Cronin, L. Angew.
spectroscopy studies6 suggested that Sb atoms are present in
trigonal-bipyramidal geometry, in the present case (in 5 and 6)
the Sb atom is found to favor octahedral geometry.
Chem., Int. Ed. 2003, 42, 4180. (b) Hill, L. M. R.; Abrahams, B. F.; Young,
C. G. Chem.;Eur. J. 2008, 14, 2805.
(26) Lin, B.-Z.; Liu, S.-X. Chem. Commun. 2002, 2126.
(27) (a) Addison, A. W.; Burke, P. J. J. Heterocycl. Chem. 1981, 8,
803. (b) Amoroso, A. J.; Thompson, A. M. C.; Jeffery, J. C.; Jones, P. L.;
McCleverty, J. A.; Ward, M. D. Chem. Commun. 1994, 2751.
It has to be mentioned here that a hexa-decanuclear core
containing coordination polymer has been reported in very

Article
Organometallics, Vol. 29, No. 5, 2010 1141
˚
Figure 3. (a) Molecular structure of 5 with thermal ellipsoids shown at 30% probability. (b) Sb-O core of 5. Selected bond lengths (in A)
and bond angles (in deg): Sb1-O1=2.091(6), Sb1-O2=2.037(6), Sb1-O4 = 2.023(6), Sb1-O5=1.953(6), Sb1-O6=1.943(6), Sb2-O1=
2.084(6), Sb2-O2 = 1.989(6), Sb2-O3 = 1.952(6), Sb2-O7 = 1.953(6), Sb2-O11 = 2.117(6), Sb3-O1 = 2.116(6), Sb3-O3 = 1.953(6),
Sb3-O4=1.967(6), Sb4-O8=2.126(5), Sb4-O10 = 2.094(6), Sb5-O7=1.980(6), Sb5-O8=2.110(5), Sb5-O9=1.961(6), Sb5-O11=
2.110(5), Sb6-O12=1.958(6), Sb6-O14=1.984(6), Sb7-O11 = 2.062(5), Sb7-O14=1.980(6), Sb8-O15=2.042(6), Sb8-O17=1.943(6),
Sb6-O6* = 1.942(6), Sb4-O17* = 1.931(6), Sb8-O5* =1.940(6), O5-Sb8* = 1.940(6), O10-Sb3* = 2.149(5), O17-Sb4* = 1.931(6),
O2-Sb1-O1=77.5(2), O4-Sb1-O1=77.6(2), O4-Sb1-O2=91.9(2), O6-Sb1-O5 = 95.1(2), O5-Sb1-O4=170.9(2), O3-Sb2-
O2=98.0(2), O7-Sb2-O2 = 93.9(2), O3-Sb2-O1=79.8(2), O3-Sb3-O1=79.0(2), O18-Sb3-O1 = 91.9(2), O9-Sb4-O8=78.1(2),
O10-Sb4-O8=87.9(2), O9-Sb5-O7=91.3(2), O9-Sb5-O8=78.4(2), O14-Sb6-O13=78.4(2), Sb2-O3-Sb3=105.5(3), O14-Sb7-
O16=93.8(2), O16-Sb8-O15=88.7(2), Sb6*-O6-Sb1=136.6(3), Sb4*-O17-Sb8=136.1(3), O5*-Sb8-O17=91.9(2), O17*-Sb4-
O10 = 96.7(2), O16-Sb7-O10* = 86.6(2), O11-Sb7-O10* = 90.9(2), O6*-Sb6-O13 = 89.5(2), Sb8*-O5-Sb1 = 136.7(3).
Compound 1: p-chlorophenylstibonic acid (0.50 g, 1.76 mmol)
and H2PhPzPh (0.40 g, 1.76 mmol). Colorless crystals of 1 were
isolated in a week’s time by slow evaporation of toluene. Yield of
isolated crystals: 0.42 g (42.80% based on p-chlorophenylstibo-
nic acid). Dec temp: 175 °C. Anal. Calcd (%) for C99H74O12-
N10Cl4Sb4: C 53.45, H 3.35, N 6.29. Found: C 53.25, H 3.31, N
6.35. IR (cm-1, KBr pellet): 3408 w, 2916 w, 1602 m, 1564 s, 1473
s, 1375 m, 1251 m, 1087 m, 810 s, 758 s, 690 m, 486 m.
Compound 2: p-bromophenylstibonic acid (0.50 g, 1.52
mmol) and H2PhPzPh (0.36 g, 1.52 mmol). Crystals suitable
for single-crystal X-ray diffraction were obtained by the diffu-
sion method using CHCl3/hexane in a week’s time. Yield: 0.45 g
(54.80% based on p-bromophenylstibonic acid). Dec temp: 185
°C. Anal. Calcd (%) for C84H62O11N8Br4Sb4: C 46.57, H 2.88, N
5.17. Found: C 46.55, H 2.96, N 5.31. IR (cm-1, KBr pellet):
3400 w, 2964 w, 1602 m, 1564 s, 1454 s, 1259 m, 1006 m, 804 s,
758 s, 690 m, 480 m. 1H NMR (400 MHz, CDCl3): δ 6.95-7.81
ppm (m, 62 H). 13C NMR (100 MHz CDCl3): δ 129.4, 129.2,
129.1, 128.7, 126.6, 125.6, 119.4, 117.1, 116.4 ppm.
method using CH2Cl2/hexane in a week’s time. Yield: 0.4 g
(50.6% based on p-bromophenylstibonic acid). Dec temp: 170
°C. Anal. Calcd (%) for C76H78O11N8Br4Sb4: C 43.75, H 3.76, N
5.37. Found: C 43.72, H 3.75, N 5.55. IR (cm-1, KBr pellet):
3271 w, 3065 w, 2962 w, 1602 m, 1558 s, 1475 s, 1381 m, 1257 m,
1116 m, 1087 s, 1064 m, 1037 m, 1012 m, 858 m, 810 m, 756 m,
488 m. 1H NMR (400 MHz, CDCl3): δ 6.6-7.6 (m, 40 H), 1.27
ppm (s, 36 H). 13C NMR (100 MHz CDCl3): 148.4, 135.5, 134.7,
130.6, 129.06, 129.2, 126.5, 123.0, 122.8, 119.2, 117.1, 116.9,
31.4, 30.9, 29.7, 28.6, 22.6, 14.17 ppm.
Compound 4: p-bromophenylstibonic acid (0.45 g, 1.37
mmol) and H2PhPz (0.22 g, 1.37 mmol). Colorless crystals were
isolated in a week’s time by slow evaporation of toluene. Yield:
0.38 g (61.3% based on p-bromophenylstibonic acid). Dec temp:
165 °C. Anal. Calcd (%) for C60H40O8N8Br4Sb4: C 39.86, H
2.23, N 6.19. Found: C 40.12, H 2.28, N 6.32. IR (cm-1, KBr
pellet): 3124 w, 2964 w, 1602 m, 1602 m, 1564 s, 1485 s, 1358 m,
1261 m, 1228 m, 1082 m, 1006 m, 848 m, 804 s,754 m, 663 m,
480 m.
Compound 3: p-bromophenylstibonic acid (0.50 g, 1.52 mmol)
and H2PhPzt-Bu (0.33 g, 1.52 mmol). Crystals suitable for
single-crystal X-ray diffraction were obtained by the diffusion
Compound 5: p-chlorophenylstibonic acid (0.45 g, 1.58 mmol)
and 3,5 DMPz (0.15 g, 1.58 mmol). Crystals suitable for single-
crystal X-ray diffraction were obtained by the diffusion method

1142 Organometallics, Vol. 29, No. 5, 2010
Table 1. X-ray Data Collection Parameters for 1-6
Jami et al.
1
2
3
formula
fw, g mol-1
cryst syst
C
113H90Cl4N10O12Sb4
2408.75
C87H65Br4Cl9N8O11Sb4
2524.16
triclinic
C76H78Br4N8O14Sb4
2134.10
monoclinic
0.34 ꢀ 0.24 ꢀ 0.16
P2(1)/c
12.131(3)
56.572(13)
14.151(3)
90
104.257 (4)
90
9413(4)
4
1.506
100
2.890
4184
triclinic
0.34 ꢀ 0.20 ꢀ 0.18
cryst size, mm
space group
0.34 ꢀ 0.26 ꢀ 0.18
P1
P1
˚
a, A
14.072(11)
17.181(14)
21.742(17)
93.338(10)
105.911(10)
99.635(10)
4954.2(7)
2
1.615
100
1.257
2412
15.639(2)
17.062(3)
19.793(3)
74.305(2)
83.621(2)
66.700(2)
4669.8(13)
2
1.795
100
3.175
2456
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Z
Dcalcd Mg m-3
T, K
μ, mm-1
F(000)
θ range, deg
index ranges
1.47 to 26.01
-17 e h e 17
-21 e k e 21
-26 e l e 26
51 784
99.3
19 378
1.047
0.0351
1.42 to 26.06
-19 e h e 19
-20 e k e 21
-24 e l e 24
39 052
98.5
18 203
1.057
0.0549
4.09 to 25.03
-14 e h e 15
-67 e k e 67
-16 e l e 16
84 726
99.2
16 501
1.075
0.0825
no. of reflns colled
completeness to θmax, %
no. of indep reflns/Rint
GooF(F2)
R1(F) (I > 2σ(I))
wR2(F2) (all data)
largest diff peak/hole, e A
0.0899
2.005/-0.903
0.1697
2.844/-1.548
0.2004
1.298/-1.147
-3
˚
4
5
6
formula
fw, g mol-1
cryst syst
C88H72Br4N8O8Sb4
2176.18
monoclinic
0.32 ꢀ 0.28 ꢀ 0.18
P2(1)/n
11.767(8)
28.368(19)
24.565(16)
90
99.242(10)
90
8093.8(9)
4
1.786
100
3.358
4256
C126H120Cl16N12O36Sb16
4893.54
monoclinic
0.38 ꢀ 0.28 ꢀ 0.22
P2(1)/n
18.466(17)
19.013(17)
25.074(2)
90
108.453(10)
90
8351.1(13)
2
1.946
100
2.867
4672
C126H120Br16N12O42Sb16
5700.90
monoclinic
0.36 ꢀ 0.22 ꢀ 0.16
P2(1)/n
18.548(2)
19.193(3)
24.981(3)
90
108.415(2)
90
8437.4(19)
2
2.244
100
6.377
5344
cryst size, mm
space group
˚
a, A
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
3
˚
V, A
Z
Dcalcd, Mg m-3
T, K
μ, mm-1
F(000)
θ range, deg
index ranges
1.44 to 25.06
-13 e h e 14
-33 e k e 33
-29 e l e 29
77 393
99.7
14 291
1.086
0.0258
1.58 to 25.04
-21 e h e 21
-22 e k e 22
-29 e l e 29
78 209
99.7
14 727
1.090
0.0483
1.37 to 25.14
-21 e h e 22
-22 e k e 22
-29 e l e 29
79 363
99.1
14 952
1.050
0.0625
no. of reflns colled
completeness to θmax (%)
no. of indep reflns/Rint
GooF(F2)
R1(F) (I > 2σ(I))
wR2(F2) (all data)
largest diff peak/hole, e A
0.0621
0.885/-0.592
0.1547
2.750/-1.685
0.2012
4.001/-2.317
-3
˚
using CH2Cl2/hexane in a week’s time. Yield: 0.20 g (41.2%
based on p-chlorophenylstibonic acid). Dec temp: 150 °C. Anal.
Calcd (%) for C126H120O36N12Cl16Sb16: C 30.92, H 2.47, N 3.43.
Found: C 31.05, H 2.52, N 3.55. IR (cm-1, KBr pellet): 3202 w,
3136 w, 2928 w, 1574 s, 1475 s, 1381 m, 1298 m, 1261 m, 1089 s,
1066 s, 1012 s, 814 m, 725 m, 488 m. 1H NMR (400 MHz,
CDCl3): δ 6.9-7.7 (m, 76 H), 1.3 ppm (s, 36 H). 13C NMR (100
MHz CDCl3): δ 143.6, 136.4, 135.4, 134.8, 132.4, 130.8, 128.1,
127.5, 30.3, 29.2, 28.5, 26.7, 22.9, 19.5, 14.05 ppm.
Compound 6: p-bromophenylstibonic acid (0.40 g, 1.22 mmol)
and 3,5 DMPz (0.12 g, 1.22 mmol). Crystals suitable for single-
crystal X-ray diffraction were obtained by the diffusion method
using CHCl3/hexane in a week’s time. Yield: 0.18 g (42.1%
based on p-bromophenylstibonic acid)). Dec temp: 165 °C.
Anal. Calcd (%) for C126H120O36N12Br16Sb16: C 27.00, H
2.15, N 2.99. Found: C 27.45, H 2.26, N 3.11. IR (cm-1, KBr
pellet): 3198 w, 3113 w, 2916 w, 1558 s, 1473 s, 1419 m, 1371 m,
1
1258 m, 1057 m, 1008 s, 808 m, 704 m, 478 m. H NMR (400
MHz, CDCl3): δ 6.9-7.5 (m, 76 H), 1.28 ppm (s, 36 H). 13C
NMR (100 MHz CDCl3): δ 143.7, 135.2, 134.9, 134.3, 131.1,
130.8, 130.0, 124.6, 29.7, 14.14 ppm.
X-ray Crystallography. Single-crystal X-ray data collection
for 1-6 were carried out at 100(2) K on a Bruker Smart Apex
˚
CCD area detector system (λ(Mo KR) = 0.71073 A) with a
graphite monochromator. The data were reduced using SAINT-
PLUS, and the structures were solved using SHELXS-97 and

Article
Organometallics, Vol. 29, No. 5, 2010 1143
refined using SHELXS-97. Crystals of the compound 3 dif-
fracted weakly at higher angles due to diffused solvated water
molecules, and hence a 2θ = 50° cutoff was applied. We were
able to model only three solvated water positions at half-
occupancies. The remaining solvent contributions were re-
moved by the SQUEEZE28 command in the Platon program.
A disordered bromine atom was freely refined using the FVAR
command of the SHELXTL program. The disordered methyl
groups of tert-butyl units were split into two positions and
refined isotropically using similar distance (SADI) and simi-
lar U restraints (SIMU). The solvated water molecules were
refined isotropically, and their hydrogens were not located.
Data collection parameters for 1-6 are summarized in Table 1.
CCDC 750276-750281 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgment. V.B. thanks the Department of
Science and Technology for financial assistance under
the SERC-Fast Track Scheme.
Supporting Information Available: ORTEP diagrams of 2, 3,
and 6 with selected bond lengths and angles are also given. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(28) Sluis, P. V. D.; Spek, A. L. Acta Crystallogr. 1990, A46, 194.