Structural motifs in phenylbismuth heterocyclic carboxylates - Secondary interactions leading to oligomers

Article abstract of DOI:10.1039/c1dt11207d

The reaction of triphenylbismuth [BiPh₃] with several heterocyclic carboxylic acids was explored. Seven crystalline compounds, [PhBi(2-O₂C-3-(OH)C₅H₃N)₂(2-O ₂C-3-(OH)C₅H₃NH)] (5), [(Bi(2-O ₂C-3-(OH)C₅H₃N)₄)(C ₅H₅NH)(C₅H₅N)] (7), [PhBi(2-O ₂C-C₄H₃N₂)₂(2-O ₂C-C₄H₄N₂)·H₂O] (8), [PhBi(2-O₂C-C₉H₆N)₂· H₂O] (9), [Ph₂Bi(O₂C-C₄H ₃O)] (10), [Ph₂Bi(O₂C-C₄H ₃S)] (11) and [PhBi(O₂C-C₄H₃S) ₂]₂ (12), were prepared by simple reactions using BiPh₃ and the corresponding acids, 3-hydroxypicolinic acid, pyrazine-2-carboxylic acid, quinoline-2-carboxylic (quinaldic) acid, furan-2-carboxylic acid and thiophene-2-carboxylic acid. Compound 5 primarily exhibits a coordination number of six with pentagonal pyramidal geometry at bismuth, but an additional weak Bi...O interaction in the direction of the lone pair of electrons is present. This feature leads to a weakly bound dimer. The use of pyridine as the solvent in a similar reaction, however, led to 7, in which all of the Bi-Ph bonds are cleaved. In this compound, bismuth exhibits a coordination number of eight and distorted dodecahedral geometry. In compound 8, the geometry around bismuth is primarily a pentagonal pyramid, however, clear-cut but weak secondary Bi...N interactions leading to a dimeric formulation are discernible in the structure. The quinaldate compound 9 exhibits a lower formal coordination number of five for bismuth, with square pyramidal geometry, but again two secondary Bi...O interactions for each bismuth in the direction of the lone pair lead to a dimer. A similar secondary Bi...O interaction involving furan oxygen is present in the furoate compound 10, which is a polymeric chain (one dimensional coordination polymer). Although the thiophene carboxylate 11 is also a polymeric chain, no Bi...S interactions are present. Unlike the previously reported tetrameric biscarboxylate [PhBi(2-O₂C-C₅H₃N)₂]₄, the thiophene carboxylate [PhBi(O₂C-C₄H₃S) ₂]₂ (12) is a dimer considering only primary interactions. However, these dimers are arranged in such a way that there are secondary Bi...S interactions in the structure in the expected direction of the lone pair of electrons on bismuth. Thus, these studies suggest that the stereochemical activity (or inactivity) of the bismuth lone pair of electrons need to be judged more cautiously. TGA studies are consistent with the presence of Bi-Ph groups in all of the compounds, except 7, as indicated by their formulae.

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PAPER
Structural motifs in phenylbismuth heterocyclic carboxylates – secondary
interactions leading to oligomers†
O. Anjaneyulu, D. Maddileti and K. C. Kumara Swamy*
Received 25th June 2011, Accepted 17th October 2011
DOI: 10.1039/c1dt11207d
The reaction of triphenylbismuth [BiPh3] with several heterocyclic carboxylic acids was explored.
Seven crystalline compounds, [PhBi(2-O2C-3-(OH)C5H3N)2(2-O2C-3-(OH)C5H3NH)] (5),
[(Bi(2-O2C-3-(OH)C5H3N)4)(C5H5NH)(C5H5N)] (7), [PhBi(2-O2C–C4H3N2)2(2-O2C-C4H4N2)·H2O] (8),
[PhBi(2-O2C–C9H6N)2·H2O] (9), [Ph2Bi(O2C–C4H3O)] (10), [Ph2Bi(O2C–C4H3S)] (11) and
[PhBi(O2C-C4H3S)2]2 (12), were prepared by simple reactions using BiPh3 and the corresponding acids,
3-hydroxypicolinic acid, pyrazine-2-carboxylic acid, quinoline-2-carboxylic (quinaldic) acid,
furan-2-carboxylic acid and thiophene-2-carboxylic acid. Compound 5 primarily exhibits a
coordination number of six with pentagonal pyramidal geometry at bismuth, but an additional weak
Bi ◊ ◊ ◊ O interaction in the direction of the lone pair of electrons is present. This feature leads to a weakly
bound dimer. The use of pyridine as the solvent in a similar reaction, however, led to 7, in which all of
the Bi–Ph bonds are cleaved. In this compound, bismuth exhibits a coordination number of eight and
distorted dodecahedral geometry. In compound 8, the geometry around bismuth is primarily a
pentagonal pyramid, however, clear-cut but weak secondary Bi ◊ ◊ ◊ N interactions leading to a dimeric
formulation are discernible in the structure. The quinaldate compound 9 exhibits a lower formal
coordination number of five for bismuth, with square pyramidal geometry, but again two secondary
Bi ◊ ◊ ◊ O interactions for each bismuth in the direction of the lone pair lead to a dimer. A similar
secondary Bi ◊ ◊ ◊ O interaction involving furan oxygen is present in the furoate compound 10, which is a
polymeric chain (one dimensional coordination polymer). Although the thiophene carboxylate 11 is
also a polymeric chain, no Bi ◊ ◊ ◊ S interactions are present. Unlike the previously reported tetrameric
biscarboxylate [PhBi(2-O2C–C5H3N)2]4, the thiophene carboxylate [PhBi(O2C–C4H3S)2]2 (12) is a dimer
considering only primary interactions. However, these dimers are arranged in such a way that there are
secondary Bi ◊ ◊ ◊ S interactions in the structure in the expected direction of the lone pair of electrons on
bismuth. Thus, these studies suggest that the stereochemical activity (or inactivity) of the bismuth lone
pair of electrons need to be judged more cautiously. TGA studies are consistent with the presence of
Bi–Ph groups in all of the compounds, except 7, as indicated by their formulae.
heterometallic carboxylates are useful starting materials for the
Introduction
synthesis of binary oxide materials.6 Photoluminiscent materials
Among all bismuth derivatives, bismuth oxo-carboxylates are of
based on dicarboxylic acids have also been recently reported.7
special interest as they are used in chemotherapy.1,2 Examples
For any of these applications, it is important to understand the
include bismuth subsalicylate (BSS, trade name Pepto-Bismol),
structural features in order to fine-tune the desired properties.
colloidal bismuth subcitrate (CBS, trade name De-Nol) and
However, the large size and significant Lewis acidity of bismuth
ranitidine bismuth citrate (RBC, trade name Tritec) that are
often results in coordination polymers with carboxylates.1b,8
used for the treatment of diarrhea, dyspepsia, peptic and duo-
The full structure for the clinically useful BSS is not known,
denal ulcers related to the infection of helicobacter pylori.1a–c,3
Compounds of bismuth also find several other applications,
including in organic synthesis4 and materials chemistry.5 Bismuth–
but good models like [Bi38O44(Hsal)26(Me2CO)16(H2O)2]·(Me2CO)4
and [Bi9O7(Hsal)13(Me2CO)5]·(Me2CO)1.5 are available (Fig. 1a).9
For the subcitrate or citrate complexes, several structural forms
are known, but most of them contain the stable [Bi(cit)2Bi]2-
School of Chemistry, University of Hyderabad, Hyderabad, 500046, AP,
dimer/s with additional O2-, OH- and H2O ligands (Fig. 1b).10
India. E-mail: kckssc@uohyd.ernet.in, kckssc@yahoo.com
Thus, the wide range of coordination environments and polyhedral
† CCDC reference numbers 825246–825251 For crystallographic data in
arrangements makes bismuth (relative to antimony11) chemistry
CIF or other electronic format see DOI: 10.1039/c1dt11207d
1004 | Dalton Trans., 2012, 41, 1004–1012
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a fertile ground for exploring coordination chemistry.1b,c The
main hindrance, however, is the low solubility of most of these
complexes. Our interest in this direction has been to obtain
structurally well-characterized derivatives of picolinic and related
acids that are biocompatible for possible pharmaceutical use. In
a couple of recent papers, we have described Bi(III) complexes
derived from 2-pyridine carboxylic (picolinic) acid, 2,6-pyridine
dicarboxylic (dipicolinic) and quinoline-2-carboxylic (quinaldic)
acids (e.g. 1–4).8,12 Compounds 2 and 3 are structural modifications
that differ in the coordinated water molecules. Compound 1
exhibited two polymorphs, as described in a recent paper.12
Andrews et al. have utilized the reaction of BiPh3 and picolinic
acid to obtain a novel picolinate derivative;13 similar cleavage
reactions using BiPh3 are also well-documented.14 In an ear-
lier paper, Ranjbar et al. have utilized bismuth subnitrate and
2,6-pyridine dicarboxylic acid in hydrochloric acid to prepare
[BiCl(H2O)(dipicolinate)]2.15 Loye and coworkers have recently
isolated [Bi3(m3-O)2(pydc)2(Hpydc)(H2O)2] (H2pydc = pyridine 3,5-
dicarboxylic acid) with a Bi6O4 core and three different bismuth
environments, by using a hydrothermal method.16 Hence, given the
propensity of bismuth to exhibit diverse coordination geometries
and the stereochemical activity of the lone pair of electrons
on bismuth, it can be expected that a wide range of structural
entities are possible, even when using the same ligand under
different conditions.17,18 Bismuth, being a borderline metal, is
presumed to be thiophilic,19 but nitrogen- and oxygen-containing
ligands coordinate more effectively. In this paper, we describe
our results on the products obtained from the reaction of BiPh3,
which has a low melting point and is fairly soluble in organic
solvents,20 with 3-hydroxypicolinic acid, pyrazine-2-carboxylic
acid, quinoline-2-carboxylic acid, furan-2-carboxylic acid and
thiophene-2-carboxylic acid.
Fig. 1 (a) The Bi9O7 core in [Bi9O7(Hsal)13(Me2CO)5]·(Me2CO)1.5 (cf. ref.
9). (b) Bi(cit)2Bi]2- subunit found in many bismuth citrate compounds (cf.
ref. 10).
Results and discussion
The reaction of the bismuth precursor BiPh3 with 3-hydroxy picol-
inic acid (1 : 3 molar ratio) in ethanol at room temperature (25 ◦C)
resulted in [PhBi(2-O2C-3-(OH)C5H3N)2(2-O2C-3-(OH)C5H3NH]
(5). As mentioned above, Andrews et al. have obtained the tetramer
[PhBi(2-O2C–C5H3N)2]4 (6) using BiPh3 and picolinic acid in
refluxing toluene, as well as under solvent free conditions.13 It may
be noted that there is one additional N-protonated carboxylate
per bismuth in compound 5 that is monodentate and not present
in compound 6. This new compound, 5, is essentially monomeric
in bismuth with a BiN2O4 skeleton with a pentagonal pyramidal
geometry, as shown in Fig. 2; the bond parameters are given in
Table 1. While the phenyl carbon is at the apical position, the three
oxygen and two nitrogen atoms form the base of the pyramid.
The bond distances are in the same range as that observed in
6. Thus, at first glance, it appears that the bismuth lone pair of
electrons is stereochemically active. However, a closer look at the
Fig. 2 Top: The molecular structure of compound 5. Bottom: The
structure of 5 showing weak dimer formation via additional Bi ◊ ◊ ◊ O
˚
interactions. The Bi–O8 distance is 4.592(6) A.
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Table 1 Selected geometric parameters (A, ◦) of 5
˚
Bi–C1
Bi–O1
Bi–O4
Bi–O7
Bi–N1
Bi–N2
Bi ◊ ◊ ◊ O7¢
2.233(3)
2.323(2)
2.442(2)
2.478(2)
2.568(3)
2.513(3)
3.449(5)a
O1–Bi–O7
O4–Bi–O7
C1–Bi–N2
O1–Bi–N2
O4–Bi–N2
O7–Bi–N2
C1–Bi–N1
O1–Bi–N1
O4–Bi–N1
O7–Bi–N1
N2–Bi–N1
144.45(8)
70.88(8)
85.89(10)
78.58(9)
65.69(9)
136.51(9)
86.88(10)
67.49(8)
147.06(9)
76.97(8)
145.42(9)
C1–Bi–O1
C1–Bi–O4
O1–Bi–O4
C1–Bi–O7
88.72(10)
85.48(10)
144.10(8)
88.74(11)
a Symm. equiv. 1 - x, -y, -z.
structure reveals that there is an additional weak, but discernible
interaction between the coordinated O7 and bismuth atom of a
˚
second molecule (distance 3.449(5) A, sum of the van der Waals
distances 3.9 A14a) in the direction of the lone pair, leading to a
˚
weakly held dimer, as shown in Fig. 2 (bottom). Similar dimeric
formulations in bismuth oxinates have also been reported.21 Both
intra- and intermolecular hydrogen bonding are present in 5,
but they do not appear to have influenced the coordination on
bismuth.
Interestingly, the use of pyridine as the solvent in the 1 : 3
stoichiometric reaction of BiPh3 and 3-hydroxy picolinic acid
at room temperature resulted in an entirely different product,
[(Bi(2-O2C-3-(OH)C5H3N)4)(C5H5NH)(C5H5N)] (7).22 The yield
of this product could be maximized by increasing the amount of
acid. Single crystals of 7 were directly obtained from the reaction
mixture after slow evaporation of most of the solvent (pyridine).
The coordination number around bismuth is eight and we may
describe the geometry as a distorted dodecahedron. Although
the bond distances are in the expected normal range, the Bi–O10
Fig. 3 Top: The molecular structure of the anion in compound 7.
Intramolecular O–H ◊ ◊ ◊ O hydrogen bonding is also shown. Bottom: A
polyhedral representation around bismuth.
˚
distance is slightly longer (by ca 0.1 A) than the rest of the Bi–O
distances (Table 2, Fig. 3).
The compound [PhBi(2-O2C–C4H3N2)2(2-O2C–C4H4N2)·H2O]
(8) was obtained by the 1 : 3 reaction of BiPh3 and pyrazine-
2-carboxylic acid in refluxing ethanol. To our knowledge, this
is the first structural report on bismuth pyrazine-2-carboxylate.
Wenkin et al. and Zevaco et al. have earlier reported the syntheses
of only insoluble materials of bismuth pyrazine and pyrazole
carboxylates.23 Taking into consideration only the stronger in-
teractions, the geometry at bismuth may still be treated as a
pentagonal pyramid. Although the structure (Fig. 4, Table 3) is
somewhat analogous to that of compound 5, the Bi(1) ◊ ◊ ◊ O(6)
Table 2 Selected geometric parameters (A, ◦) of 7
˚
Bi–O1
Bi–O4
Bi–O7
Bi–O10
Bi–N1
Bi–N2
Bi–N3
Bi–N4
2.343(2)
2.380(3)
2.447(3)
2.587(2)
2.559(3)
2.583(3)
2.449(3)
2.630(3)
O4–Bi–N2
O4–Bi–N3
O4–Bi–N4
O7–Bi–O10
O7–Bi–N1
O7–Bi–N2
O7–Bi–N3
O7–Bi–N4
O10–Bi–N1
O10–Bi–N2
O10–Bi–N3
O10–Bi–N4
N1–Bi–N2
N1–Bi–N3
N1–Bi–N4
N2–Bi–N3
N2–Bi–N4
N3–Bi–N4
66.04(9)
80.75(10)
78.66(9)
76.21(8)
78.11(9)
76.00(9)
66.98(9)
138.97(9)
79.34(9)
83.56(9)
143.04(9)
62.89(8)
151.69(9)
89.82(10)
96.58(10)
90.46(10)
95.45(10)
154.03(10)
˚
distance (3.332(5) A) is significantly shorter than that observed
˚
for the corresponding Bi ◊ ◊ ◊ O(8) distance of 4.592(6) A in 5. The
water molecule present in the structure does not interact with
bismuth; it is only involved in hydrogen bonding interactions with
oxygen atoms O1, O4 and O6. Of the two nitrogen atoms N5 and
N6 in the unique carboxylate, N6, which is farther away from the
carboxylate moiety, is protonated and hydrogen bonded to O1 and
O2 (not shown in Fig. 4). What is unique in the system, however,
is that the bismuth atoms of the two molecules come close to N2¢
O1–Bi–O4
O1–Bi–O7
O1–Bi–O10
O1–Bi–N1
O1–Bi–N2
O1–Bi–N3
O1–Bi–N4
O4–Bi–O7
O4–Bi–O10
O4–Bi–N1
74.99(9)
131.82(8)
125.05(9)
66.81(9)
140.94(9)
80.54(10)
78.98(9)
129.41(9)
128.12(9)
141.67(9)
˚
of a second molecule (distance 3.509(8) A; sum of the van der
Waals distances 4.0 A),14 resulting in a weak dimer. Although this
˚
distance is not in the realm of any significant bonding interactions,
the fact that the nitrogen atom is located on the same side as the
expected region for the lone pair of electrons on bismuth is unusual
(or fascinating).
1006 | Dalton Trans., 2012, 41, 1004–1012
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Table 3 Selected geometric parameters (A, ◦) of 8
Table 4 Selected geometric parameters (A, ◦) of 9
˚
˚
Bi–C16
Bi–O1
Bi–O3
Bi–O5
Bi–N1
Bi–N3
Bi ◊ ◊ ◊ N2¢
Bi ◊ ◊ ◊ O6
2.233(8)
2.398(5)
2.472(6)
2.368(5)
2.613(5)
2.625(6)
3.509(8)a
3.333(5)
C16–Bi–N1
C16–Bi–N3
O1–Bi–O3
O1–Bi–O5
O1–Bi–N1
O1–Bi–N3
O3–Bi1–O5
O3–Bi–N1
O3–Bi–N3
O5–Bi–N1
O5–Bi–N3
N1–Bi–N3
80.4(2)
81.4(2)
Bi–C1
Bi–O1
Bi–O3
Bi–N1
Bi–N2
Bi ◊ ◊ ◊ O3¢
Bi ◊ ◊ ◊ O4¢
2.237(7)
2.213(5)
2.241(4)
2.610(5)
2.619(5)
3.347(5)a
3.495 (7)a
C1–Bi–O3
C1–Bi–N1
C1–Bi1–N2
O1–Bi–O3
O1–Bi–N1
O1–Bi1–N2
O3–Bi1–N1
O3–Bi1–N2
N1–Bi1–N2
90.5(2)
82.46(18)
83.32(18)
74.04(16)
67.48(16)
141.21(18)
140.81(17)
67.90(19)
147.76(19)
136.08(16)
83.36(15)
65.27(16)
158.67(18)
140.33(17)
71.80(18)
64.13(17)
144.12(17)
76.21(18)
131.42(17)
C1–Bi–O1
89.9(2)
C16–Bi–O1
C16–Bi–O3
C16–Bi–O5
90.1(2)
91.6(2)
82.8(2)
a Symm. equiv.: -x, 1 - y, 2 - z.
a Symm. equiv.: -x, -y, 1 - z.
Fig. 5 The molecular structure of compound 9, excluding the non-coor-
dinated water molecule.
O2C–C5H3N)2]4 (6) reported by Andrews et al.13 in that the latter
is a tetramer with primarily a pentagonal pyramidal geometry
around bismuth. Curiously though, compound 9 forms a weakly
held dimer with two additional Bi–O interactions involving O3 and
˚
˚
O4 [Bi1 ◊ ◊ ◊ O3¢ 3.347(5) A; Bi ◊ ◊ ◊ O4¢ 3.495(7) A; symm. equiv.: -x,
1 - y, 2 - z] in the direction of the lone pair of electrons, as shown
in Fig. 5.
Furan-2-carboxylic (furoic) acid and thiophene-2-carboxylic
acids feature potentially coordinating ring oxygen or sulphur
in addition to the carboxylate group, in a manner analogous
to picolinic acids. To our knowledge, the structural chemistry
of Bi(III) compounds of these acids has not been reported.
Examples of only Bi(V) compounds are, however, known.24,25 In
the present work, we isolated crystalline [Ph2Bi(O2C–C4H3O)]
(10) by the reaction of BiPh3 and 2-furoic acid (used 1 : 3 molar
ratio) in ethanol at room temperature (25 ◦C). Bismuth–thiophene
carboxylates [Ph2Bi(O2C–C4H3S)] (11) and [PhBi(O2C–C4H3S)2]2
(12) were obtained from a procedure similar to that for compound
10. Compound 11 was obtained only in very small quantities, but
a few crystals suitable for X-ray structure analysis were available;
compound 12 was the major product.
Fig. 4 Top: The molecular structure of compound 8. Bottom: Dimer
formation via weak Bi ◊ ◊ ◊ N interaction in 8.
Quinoline-2-carboxylic (quinaldic) acid is expected to react
in a manner analogous to picolinic acid. However, the 1 : 3
stoichiometric reaction of BiPh3 with this acid, conducted in
refluxing ethanol afforded the bis-carboxylated product [PhBi(2-
O2C–C9H6N)2·H2O] (9) in fair yields. It crystallises in the mon-
oclinic space group P21/n, wherein the primary coordination
number of bismuth is 5 (Fig. 5, Table 4). This basic geometry
can be construed as a square pyramid with quinaldate N/O at the
base of the pyramid. The lower coordination number relative to
compound 4 may be directly correlated with the expected lower
Lewis acidity of bismuth in 9 due to the Bi–C bond in lieu of a
Bi–O bond in 4. The structure differs from the tetramer [PhBi(2-
Compound 10 (Fig. 6, Table 5) crystallises in monoclinic P21/n
space group, wherein the primary coordination number of bismuth
can be considered to be five, with the longest Bi–O1¢ bond being
˚
2.981(5) A. The structure is shown in Fig. 6. Excluding the
˚
weaker Bi ◊ ◊ ◊ O3 interaction (3.32(2) A) to the furoate oxygen,
the geometry at bismuth can be considered to square pyramidal
with C7 as the apical bond and the remaining atoms C1, O1, O1¢
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Table 5 Selected geometric parameters (A, ◦) of 10
Table 6 Selected geometric parameters (A, ◦) of 11
˚
˚
Bi–C1
Bi–C7
Bi–O1
Bi–O2¢
Bi–O1¢
Bi ◊ ◊ ◊ O3
2.235(3)
2.243(4)
2.479(2)
2.368(5)a
2.982(5)a
3.32(2)
C1–Bi–C7
C1–Bi–O1
C1–Bi–O2¢
C7–Bi–O1
C7–Bi–O2¢
O1–Bi–O2¢
94.60(13)
82.86(10)
84.68(10)
83.02(12)
85.71(12)
162.45(8)
Bi1–C1
Bi1–C7
Bi1–O1
Bi1–O2
Bi1–O4
2.244(8)
2.236(8)
2.317(6)
2.564(6)
3.005(6)
C1–Bi1–C7
C1–Bi1–O1
C1–Bi1–O2
C7–Bi1–O1
C7–Bi1–O2
O1–Bi1–O2
C18–Bi2–C24
C18–Bi2–O3
C18–Bi2–O4
C24–Bi2–O3
C24–Bi2–O4
O3–Bi2–O4
C41–Bi3–C35
C35–Bi3–O5
C35–Bi3–O6
C41–Bi3–O5
C41–Bi3 O6
O5–Bi3–O6
94.2(3)
86.9(2)
84.1(2)
85.5(2)
86.6(2)
167.6(2)
97.5(3)
87.3(3)
82.2(3)
85.0(2)
83.5(2)
163.3(2)
99.7(3)
81.8(2)
83.0(2)
89.0(3)
81.3(2)
160.3(2)
Bi2–C18
Bi2–C24
Bi2–O3
Bi2–O4
Bi2–O2
2.223(8)
2.239(9)
2.324(6)
2.580(6)
2.941(6)
a Symm. equiv. 0.5 - x, 0.5 + y, 0.5 - z.
Bi3–C35
Bi3–C41
Bi3–O5
Bi3–O6
Bi3–O6
2.238(8)
2.235(8)
2.290(6)
2.568(6)
3.045(6)
Fig. 6 Left: The molecular structure of compound 10, also showing the
weaker Bi ◊ ◊ ◊ O interaction. Right: The polymeric chain in 10.
and O2¢ at the base. It can be noted that the carboxylate acts as
both a bridging and a chelating ligand. The resulting entity is a
coordination polymer.
Unlike compound 10, compound 11 was obtained only in trace
quantities in a pure state. Although we made an attempt to
maximize the yield of this compound, due to similar solubility
characteristics, more quantities of the pure material could not be
obtained. The structure (Fig. 7, Table 6), gratifyingly, could be
obtained. The compound crystallises in the orthorhombic P212121
space group. There are three molecules in the asymmetric unit. As
observed in the structure of 9, the carboxylate moiety acts both as
a chelating and as a bridging ligand, leading to a polymeric chain.
The main difference though is that Bi1 and Bi2 are involved in one
chain, while Bi3 is involved in a second chain. One Bi–O distance
˚
is longer and is in the range 2.95–3.05 A. Although bismuth is
considered to be thiophilic,19 there are also no apparent Bi ◊ ◊ ◊ S
˚
interactions of <4 A in the molecule. The coordination geometry
at bismuth is rather irregular, but may be approximated as a square
pyramid with C1 (for Bi1), C8 (for Bi2) and C41 (for Bi3) at the
apices of the corresponding bismuth atom.
Fig. 7 The molecular structure of compound 11. Top: A chain involving
Bi1 ad Bi2. Bottom left: The structure around Bi3. Bottom right: A chain
involving Bi3.
¯
Compound 12 crystallises in the triclinic P1 space group. This
˚
compound has two carboxylates per bismuth. One carboxylate is
purely chelating, while the other is involved in both chelation and
bridging (Fig. 8, Table 7). The molecule can thus be considered to
be a dimer of [PhBi(O2C–C4H3S)2] and is again a new structural
type for bismuth. The primary coordination sphere around
bismuth has five oxygen atoms and one carbon atom, but the
geometry is non-octahedral. The overall geometry involving these
groups is a pentagonal pyramid (Fig. 8, bottom picture). The Bi–
O4¢ (symm. code: 1 - x, -y, 1 - z) distance is the longest (2.818(3)
A), but still in the range expected for such compounds; thus all of
these Bi–O and Bi–C bond lengths are in the normal range.
The structure of 12, though, shows another interesting crystal-
lographic feature that is not very common and is not exhibited
by compound 11. The carbon adjacent to C8/C13 and sulphur
exchange positions in the packing, resulting in essentially half
occupancy by S and C–H moieties at each position.26 However,
˚
one of these positions is close to bismuth (distance: 3.597(3) A,
14a
˚
sum of the van der Waals distances 4.2 A; symm. equiv. -x,
1008 | Dalton Trans., 2012, 41, 1004–1012
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Table 7 Selected geometric parameters (A, ◦) of 12
˚
Further comments on synthesis
In general, the products reported herein had poor solubility
in normal organic solvents (dichloromethane, THF, acetonitrile,
DMF, etc.) and, hence, when partially substituted products
were obtained, purification was somewhat tedious, although the
precursor BiPh3 could be readily removed by washing with organic
solvents. Under the conditions employed, there was no guarantee
that the stoichiometry used would result in replacement of the
corresponding number of phenyl groups. Only when the product
obtained was fairly crystalline did characterization become easier.
Bi–C1
Bi–O1
Bi–O2
Bi–O3
Bi–O4
Bi–O4¢
Bi ◊ ◊ ◊ S2¢¢
2.222(4)
2.535(3)
2.282(3)
2.266(3)
2.635(3)
2.818 (4)a
3.597 (3)a
C1–Bi–O3
C1–Bi–N1
C1–Bi1–N2
O1–Bi–O3
O1–Bi–N1
O1–Bi1–N2
O3–Bi1–N1
O3–Bi1–N2
N1–Bi1–N2
90.5(2)
82.46(18)
83.32(18)
74.04(16)
67.48(16)
141.21(18)
140.81(17)
67.90(19)
147.76(19)
C1–Bi–O1
89.9(2)
a Symm. equiv.: (i) 1 - x, -y, 1 - z, (ii) -x, 1 - y, 1 - z.
1
Although we tried to obtain the H NMR spectra (DMSO-d6
or DMSO-d6 + CDCl3) of these samples, only compounds 9,
10 and 12 gave decent spectra; compounds 5 and 7 gave broad
resonances, but the OH/NH protons could be detected. In the
case of 8, repeated washing with ethanol appears to hydrolyze
the compound. Pure compound 11 was obtained only in trace
quantities and, hence, the spectrum was not recorded. We have also
conducted 1 : 3 stoichiometric reactions of BiPh3 with several other
carboxylic (2-hydroxynicotinic, 2-thionicotinic and pyridine-2,6-
dicarboxylic) acids at room temperature, as well as under reflux in
ethanol; only insoluble microcrystalline material or powder was
obtained in each case.
The TGA data (Fig. 10) show that compound 5 is stable
up to ~210 ◦C, after which initially the phenyl group will be
eliminated. Remaining ligands are let off at 250–350 ◦C and
complete decomposition occurs near to 400 ◦C. For compound
7 at 150 ◦C, pyridine and protonated pyridine are eliminated. The
remaining decomposition pattern is similar to 5, as the ligand used
is same for both. Compound 8 behaves differently, with the non-
coordinated water molecules coming off before the decomposition
sets in. Decomposition for this molecule starts at 270 ◦C and
completes at 350 ◦C. Compounds 10 and 12 are thermally less
stable and decompose more readily, probably because of the ease
of cleavage of the phenyl group. For 10, decomposition starts
at 210 ◦C and for 12 at 240 ◦C; it is complete at ~360 ◦C.
In all cases, the final product of decomposition is most likely
Bi2O3.4,23a
Fig. 8 The molecular structure of compound 12. Top: A labeled structure
showing the dimeric unit. Bottom: Polyhedra depicting the primary
coordination sphere of the pentagonal pyramid around bismuth.
1 - y, 1 - z), as shown in Fig. 9. This interaction is again the
direction of the lone pair of electrons on bismuth.
Fig. 10 A drawing showing the TGA behaviour of compounds 5, 7–9, 10
and 12.
Conclusion
Using BiPh3 as a precursor, seven structurally diverse heterocyclic
carboxylates of bismuth were synthesized and characterized. The
use of several other heterocyclic carboxylic acids led only to
Fig. 9 A diagram depicting weak Bi ◊ ◊ ◊ S interactions in the crystal
packing in compound 12.
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microcrystalline materials. Unlike the picolinate tetramer
[PhBi[(2-O2C–C5H3N)2]4 (6),13 our compound [PhBi(O2C–
C4H3S)2]2 (12) is a dimer. This feature suggests that other
oligomeric/polymeric forms may be possible using slightly dif-
ferent ligands or under different experimental conditions. In
addition to providing a wide array of geometries around bismuth,
the intricate details reveal that additional secondary Bi ◊ ◊ ◊ O,
Bi ◊ ◊ ◊ N or Bi ◊ ◊ ◊ S interactions are present in compounds 5 and
8–12. These interactions are in the direction expected for the
lone pair of electrons on bismuth. Although one may discount
them as secondary (or weak), we do find secondary Bi ◊ ◊ ◊ O
Synthesis of [PhBi(2-O2C–C4H3N2)2(2-O2C–C4H4N2)·H2O] (8)
To a refluxing solution of BiPh3 (0.100 g, 0.227 mmol) in dry
ethanol (20 cm3) under dry nitrogen atmosphere was added
pyrazine-2-carboxylic acid (0.084 g, 0.681 mmol) and the clear
solution obtained was heated under reflux for a further 6 h.
The solution was filtered to remove any suspended impurities
and the clear, colourless filtrate was kept at 4 ◦C (in an open
container). After 10–12 d, colourless crystals suitable for X-
ray single crystal analysis were obtained. Yield: 0.077 g, 50%.
Elemental analysis (calc◦d): C, 37.51 (37.44); H, 2.31 (2.37); N,
12.35 (12.48); Mp: >320 C; IR (cm-1) 3474(br), 3057(w), 1645(s),
1599(m), 1558(m), 1471(w),1408(w), 1375(m), 1336(m), 1155(s),
1032(s), 846(s), 788(s), 729(s), 690(m), 632(m). The water could not
be removed satisfactorily. 1H NMR (400 MHz, CDCl3 + DMSO-
d6) d = 9.21 (s, 3H, Ar-H), 8.84 (br, 6H, Ar-H), 8.44–8.42 (m, 1H,
Ar-H), 7.67–7.10 (many peaks, 4H, Ar-H).
˚
interactions in the range 2.955–3.271 A, even in the recently
reported compound [Bi3(m3-O)2(pydc)2(Hpydc)(H2O)2] (H2pydc =
pyridine 3,5-dicarboxylic acid).16 Finally, TGA studies suggest the
decomposition to Bi2O3 in all cases in the temperature range 200–
350 ◦C.
Experimental section
Synthesis of [PhBi(2-O2C–C9H6N)2·H2O] (9)
The precursor BiPh3 was prepared from reaction of PhMgBr
with anhydrous BiCl327 and was recrystallised from ethanol. Other
chemicals were procured from Aldrich or local manufacturers. IR
spectra were recorded on a JASCO FT-IR 5400 spectrophotome-
ter. Elemental analyses were carried out on a Thermo Finnigan
EA1112 analyser. Thermogravimetric and differential thermal
analysis (TG-DTA) were performed on a (Netzsch STA 409 Pc)
TG-DTA instrument at 30–500 ◦C with a scanning rate of 10 deg
min-1. under nitrogen flow.
The procedure was same as that for 8 using BiPh3 (0.100 g, 0.227
mmol) and quinoline-2-carboxylic acid (0.118 g, 0.681 mmol).
Yield: 0.099 g, 67%. Elemental analysis (c◦alcd): C, 48.16 (48.51);
H, 2.95 (2.45),N, 4.3 (4.32); m.p.: 234–238 C; IR (cm-1): 3557(w),
3499(w) 3045(w), 1630(s), 1566(m), 1506(m), 1460(s), 1429(w),
1319(s), 1213(m), 1161(m), 958(w), 895(s), 798(s), 773(s), 733(s).
1H NMR (400 MHz, CDCl3 + DMSO-d6) d = 8.52 (br, 5H, Ar-
H), 8.07–7.99 (m, 7H, Ar-H), 7.64 (m, 5H, Ar-H), 4.50 (ca 2H,
H2O).
Synthesis of [PhBi(2-O2C-3-(OH)C5H3N)2(2-O2C-3-
(OH)C5H3NH)] (5)
Synthesis of [Ph2Bi(O2C–C4H3O)] (10)
To a solution of BiPh3 (0.100 g, 0.227 mmol) in ethanol (25 cm3)
was added furan-2-carboxylic acid (0.076 g, 0.681 mmol) and the
clear solution obtained was stirred at room temperature for a fur-
ther 1 d. The solution was filtered and the filtrate kept at 4 ◦C. After
12–14 d, colourless crystals were obtained. When the reaction
was conducted under reflux conditions, an insoluble precipitate
was obtained. Yield: 0.058 g, 54%. Elemental analysis (calcd):
To a solution of BiPh3 (0.100 g, 0.227 mmol) in ethanol (10 cm3)
was added 3-hydoxypicolinic (3-hydoxy-pyridine-2-carboxylic)
acid (0.094 g, 0.681 mmol) in ethanol (15 cm3) all at once and the
clear solution obtained was stirred for a further 12 h. The solution
was filtered to remove any suspended impurities and the colourless
filtrate was left for slow evaporation of the solvent at 4 ◦C. After
8 d, crystals suitable for X-ray single crystal analysis were formed.
Yield: 0.079 g, 56%. Elemental analysis (calcd): C, 41.15 (41.08); H,
2.51 (2.56); N, 5.91 (5.99); m.p.: >320 ◦C; IR (cm-1) 3456(br), 3090
(w), 1633(s), 1610(w), 1572(w), 1452(s), 1390(s), 1325(s), 1248(s),
1215(s), 1143(w), 1111(m), 1059(w), 883(s), 825(s), 729(w), 677(w).
1H NMR (400 MHz, CDCl3+DMSO-d6) d = 13.71 (br, 3H), 8.34–
8.33 (br, 3H, Ar-H + NH), 7.59–7.56 (m, ca 11H, Ar-H), 7.15–7.12
(m, 1H, Ar-H).
◦
C, 43.12 (43.03); H, 2.68 (2.74); m.p.: 222–224 C; IR (cm-1)
3111(w), 3059 (w), 2920(w), 1583(s), 1537(m), 1516(m), 1469(m),
1
1412(s),1363(m), 1010(m), 812(s),775(s), 725(s). H NMR (400
MHz, CDCl3+DMSO-d6) d = 8.23–8.22 (d, J = 6.0 Hz, 3H, Ar-
H), 7.69–7.67 (m, 1H, Ar-H), 7.56–7.55 (m, 3H, Ar-H), 7.51 (br,
1H, Ar-H), 7.34–7.24 (m, 3H, Ar-H), 6.91 (br, 1H, Ar-H), 6.41
(br, 1H, Ar-H).
Synthesis of [(Bi(2-O2C-3-(OH)C5H3N)4)(C5H5NH)(C5H5N)] (7)
Synthesis of [Ph2Bi(O2C–C4H3S)] (11) and [PhBi(O2C–C4H3S)2]2
(12)
To a solution of BiPh3 (0.100 g, 0.227 mmol) in pyridine (5 cm3)
was added 3-hydroxy-picolinic acid (0.094 g, 0.681 mmol) and
the clear solution obtained was stirred for 12 h. The solution was
filtered to remove any suspended impurities and the filtrate was left
at room temperature. After 2 d, colourless crystals were obtained.
Yield: 0.103 g, 48%. Elemental analysis◦(calcd): C, 44.26 (44.34); H,
2.85 (2.93); N, 9.21 (9.13); m.p.: >320 C; IR (cm-1) 3427(w) 3057
(w), 2359(s) 1622(s), 1556(m), 1454(s), 1383(s),1307(s), 1244(m),
Compound 11 (needle type, a few crystals, low solubility) was
obtained in trace quantities along with compound 12 (rectangular
blocks) by the same procedure as that for 10 using BiPh3
(0.100 g, 0.227 mmol) and thiophene-2-carboxylic acid (0.087 g,
0.681 mmol). Attempted maximization of the yield of 11 by using
ca 1 : 1 stoichiometry of the reactants under reflux conditions led to
an essentially insoluble material after washing off unreacted BiPh3.
Compound 12: Yield: 0.078 g, 70%. Elemental analysis (calcd): C,
35.56 (35.62); H, 2.0 (1.71); m.pp: 224–228 ◦C; IR (cm-1) 3088(w),
2920(w), 2841(s), 1545(s), 1521(s), 1419(s), 1381(s), 1111(s), 862(s),
1
1143(w), 1057(w), 879(s), 806(s), 763(m), 677(s). H NMR (400
MHz, DMSO-d6) d = 13.94 (br, ca 4H), 8.70–7.50 (br m, ca 21H,
Ar-H + NH), 7.18 (~s, 2H, Ar-H).
1010 | Dalton Trans., 2012, 41, 1004–1012
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Table 8 Crystallographic data for compounds 5 and 7–12
Compound
5
7
8
9
10
11a
12
Emp. formula
Formula wt
Crystal system
C24H18BiN3O9
701.39
C34H27BiN6O12
920.60
C21H17BiN6O7
674.39
monoclinic
C26H19BiN2O5
648.41
monoclinic
C17H13BiO3
474.25
monoclinic
P21/n
10.340(2)
9.725(2)
15.679(3)
90
101.02(3)
90
1547.6(5)
4
C51H39Bi3O6S3
1470.94
orthorhombic
P212121
9.238(2)
17.369(4)
30.368(7)
90
90
90
4873(2)
4
2.005
C16H11BiO4S2
540.35
triclinic
triclinic
triclinic
¯
¯
¯
Space group
P1
P1
C2/c
P21/n
P1
˚
a/A
9.672(1)
11.413(1)
11.541(1)
77.802(2)
78.026(3)
72.353(2)
1172.3(2)
2
9.982(1)
13.869(2)
13.908(2)
73.185(2)
70.121(2)
70.084(2)
1669.2(3)
2
27.571(2)
10.287(1))
17.080(1)
90
10.120(2)
13.740(3)
16.630(3)
90
8.645(1)
9.601(1)
10.697(1)
81.279(1)
71.418(1)
71.429(1)
796.5(1)
2
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
109.015(1)
90
4580.0(6)
8
1.956
7.755
101.00(3)
90
2269.9(8)
4
1.897
7.809
3
˚
V/A
Z
Dcalcd
m
F000
1.987
7.581
676
4774/0/337
1.832
5.358
904
5870/0/494 3
2.035
11.399
888
2.253
11.346
508
2802/0/208
10.984
2760
8553/62/558
2592
4001/4/325
1248.0
3986/3/313
Data/restraints/
2726/0/190
parameters
S
R1
wR2 (all data)
max./min. residual
elec. dens./e A
1.021
0.0217
0.0500
0.825/-0.436
1.054
0.0247
0.0597
0.752/-0.537
1.051
0.0544
0.1355
3.703/-2.755
0.988
0.0359
0.0739
1.489/-0.806
1.086
0.0191
0.0471
0.758/-0.705
1.051
0.0338
0.0828
1.453/-0.667
1.055
0.0221
0.0556
1.318/-1.158
-3
˚
a Flack parameter: 0.005(8).
814(s), 767(s), 721(s), 653(m). 1H NMR (400 MHz, CDCl3
DMSO-d6) d = 8.73–8.72 (d, J = 11.2 Hz, 2H, Ar-H), 7.80–7.74 (m,
2H, Ar-H), 7.61–7.54 (m, 2H, Ar-H), 7.47–7.46 (m, 2H, Ar-H),
7.28–7.26 (m, 1H, Ar-H), 7.03–7.02 (m, 2H, Ar-H).
+
Acknowledgements
We acknowledge the Department of Science and Technology
(DST), New Delhi for financial support under the Metal Based
Drugs program, for setting up a National Single Crystal Diffrac-
tometer facility and for the J. C. Bose fellowship (to KCK). Thanks
are also due to UPE program of UGC (New Delhi) for other
equipment. OA thanks CSIR (New Delhi) for a fellowship.
Other reactions
To a boiling solution of 0.227 mmol of BiPh3 in 25 cm3 of
ethanol was added 0.681 mmol of carboxylic (2-hydroxynicotinic,
2-thionicotinic, or pyridine 2,6-dicarboxylic) acid and the contents
heated under reflux for 6 h to obtain a precipitate. The solution
was filtered, the precipitate washed with ethanol and dried in air.
All of these had melting points > 320 ◦C.
Notes and references
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˚
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calculated for sulphur = 11.5/16 = 0.71875]. This procedure gives
slightly different values of Mr, m, density etc.; Fig. 8 also illustrates
this. The crystal data are summarized in Table 8. CCDC numbers
are 825245–825251†.
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22 Callens et al. have reported the structure of the interesting compound
Na{Bi(2-CO2–C5H4N)}4, which was prepared by a different route. It
appears that the precursor contained some NaBi(OEt)4, which provided
the Na+ source. See: E. Callens, A. J. Burton, A. J. P. White and A. G.
M. Barrett, Tetrahedron Lett., 2008, 49, 3709.
23 (a) M. Wenkin, R. Touillaux and M. Devillers, New J. Chem., 1998, 22,
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11 See, for example: (a) M. A. Said, K. C. Kumara Swamy, D. M. Poojary,
A. Clearfield, M. Veith and V. Huch, Inorg. Chem., 1996, 35, 3235;
(b) M. A. Said, K. C. Kumara Swamy, Kamlesh Babu and M. Nethaji,
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24 M. Domagala, H. Preut and F. Huber, Acta Crystallogr., Sect. C: Cryst.
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25 A. Miloudi, G. Boyer, D. EI-Abed, J.-P. Finet and J.-P. Galy, Main
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26 Such exchange of positions among certain moieties does occur in
the crystal structures. For some examples from our work, see: (a) C.
Muthiah, K. Praveen Kumar, S. Kumaraswamy and K. C. Kumara
Swamy, Tetrahedron, 1998, 54, 14315 (CH3 and Cl interchange);
(b) Manab Chakravarty, Praveen Kommana and K. C. Kumara Swamy,
Chem. Commun., 2005, 5396 (oxygen and lone pair interchange);
(c) Manab Chakravarty, R. Rama Suresh and K. C. Kumara Swamy,
Inorg. Chem., 2007, 46, 9819 (S and Se interchange); (d) M. Phani
Pavan, Manab Chakravarty and K. C. Kumara Swamy, Eur. J. Org.
Chem., 2009, 5927 (CH and O interchange).
12 O. Anjaneyulu and K. C. Kumara Swamy, J. Chem. Sci., 2011, 123,
131.
13 P. C. Andrews, G. B. Deacon, P. C. Junk, I. Kumar and M. Silberstein,
Dalton Trans., 2006, 4852.
14 (a) C. Silvestru, H. J. Breunig and H. Althaus, Chem. Rev., 1999, 99,
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15 M. Ranjbar, H. Aghabozorg, A. Moghimi and A. Yanovsky, Anal. Sci.,
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16 A. C. Wibowo, M. D. Smith and H.-C. zur Loye, Inorg. Chem., 2010,
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17 Secondary weak interactions were not taken into account in several
reports. For a discussion of some such examples, see section F in ref.
14(a).
18 Even using the simple chloride ion as a ligand gives a variety of
coordination environments around bismuth. See, for example: (a) A.
27 J. Supniewski and R. Adams, J. Am. Chem. Soc., 1926, 48, 507.
28 (a) G. M. Sheldrick, SHELX-97- A program for crystal structure solution
and refinement, University of Go¨ttingen, 1997; (b) G. M. Sheldrick,
SADABS Siemens Area Detector Absorption Correction, University of
Go¨ttingen, Germany, 1996; (c) G. M. Sheldrick, SHELXTL NT Crystal
Structure Analysis Package, Bruker AXS, Analytical X-ray System, WI,
USA, 1999, version 5.10.
1012 | Dalton Trans., 2012, 41, 1004–1012
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