Metal-organic hybrids of 1,3,5-tris(4-pyridylsulfanylmethyl)-2,4,6- trimethylbenzene with mercuric halides

Article abstract of DOI:10.1002/ejic.200600867

Synthesis and solid-state structure elucidation of metal-organic hybrids of 1,3,5-tris(4-pyridylsulfanylmethyl)-2,4,6-trimethylbenzene with Hg^II halides (HgCl₂, HgBr₂, and HgI₂) are reported. In the metal-hybrids of L¹, a reaction with HgCl₂ in dmso as well as in dmf gave host-guest complexes, 1a and 1b, respectively, with the corresponding solvent of crystallization as the guests, while a reaction with HgI₂ gave open-frame network structures without any solvent of crystallization from both dmso and dmf (1c). However, reaction with HgBr ₂ gave crystals of two different morphologies from each solvent dmso and dmf (1d-1f), which corresponds to the structures with and without solvent of crystallization that resemble the related structures formed by HgCl₂ and HgI₂, respectively. Three-dimensional structures of all the compounds were characterized by single-crystal X-ray diffraction methods. While 1a and 1b crystallize in triclinic P1 space groups 1a: a = 9.049(2), b = 13.646(4), c = 16.298(4) A, a = 111.99(1), β = 90.43(1), γ = 101.57(1)°, Z = 2, V = 1820.6(8) A³; 1b: a = 8.979(3), b = 13.611(5), c = 16.355(5) A, a = 111.57(1), β = 92.37(1), γ = 101.07(1)°, Z = 2, V = 1810.05(11) A³, complexes 1c-1f crystallize into monoclinic space groups [1c: C2/c, a = 27.661(7), b = 18.821(4), c = 15.786(4) A, β = 113.13(1), Z = 4, V = 7558(3) A³, 1d: P2₁/c, a = 17.950(5), b = 9.031(2), c = 22.200(6) A, β = 113.62(1), Z = 4, V = 3297.3(15) A³, 1e: C2/c, a = 26.753(15), b = 18.415(10), c = 14.940(7) A, β = 109.50(1), Z = 4, V = 6938(6) A³, 1f: P2 ₁/n, a = 17.697(10), b = 9.224(5), c = 21.933(12) A, β = 112.50(1), Z = 4, V = 3308(3) A³]. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200600867

FULL PAPER
DOI: 10.1002/ejic.200600867
Metal–Organic Hybrids of 1,3,5-Tris(4-pyridylsulfanylmethyl)-2,4,6-trimethyl-
benzene with Mercuric Halides
Jayarama PrakashaReddy[a] and Venkateswara Rao Pedireddi*[a]
Keywords: Metal–organic hybrids / Supramolecular chemistry / Crystal engineering / Fluxional thio ligands / Mercuric
halides
¯
Synthesis and solid-state structure elucidation of metal–or-
ganic hybrids of 1,3,5-tris(4-pyridylsulfanylmethyl)-2,4,6-tri-
methylbenzene with HgII halides (HgCl2, HgBr2, and HgI2)
are reported. In the metal-hybrids of L1, a reaction with
HgCl2 in dmso as well as in dmf gave host–guest complexes,
1a and 1b, respectively, with the corresponding solvent of
crystallization as the guests, while a reaction with HgI2 gave
open-frame network structures without any solvent of
crystallization from both dmso and dmf (1c). However, reac-
tion with HgBr2 gave crystals of two different morphologies
from each solvent dmso and dmf (1d–1f), which corresponds
to the structures with and without solvent of crystallization
that resemble the related structures formed by HgCl2 and
HgI2, respectively. Three-dimensional structures of all the
compounds were characterized by single-crystal X-ray dif-
fraction methods. While 1a and 1b crystallize in triclinic P1
space groups 1a: a = 9.049(2), b = 13.646(4), c = 16.298(4) Å,
α = 111.99(1), β = 90.43(1), γ = 101.57(1)°, Z = 2, V =
1820.6(8) Å3; 1b: a = 8.979(3), b = 13.611(5), c = 16.355(5) Å,
α = 111.57(1), β = 92.37(1), γ = 101.07(1)°, Z = 2, V =
1810.05(11) Å3, complexes 1c–1f crystallize into monoclinic
space groups [1c: C2/c, a = 27.661(7), b = 18.821(4), c =
15.786(4) Å, β = 113.13(1), Z = 4, V = 7558(3) Å3, 1d: P21/c, a
= 17.950(5), b = 9.031(2), c = 22.200(6) Å, β = 113.62(1), Z =
4, V = 3297.3(15) Å3, 1e: C2/c, a = 26.753(15), b = 18.415(10),
c = 14.940(7) Å, β = 109.50(1), Z = 4, V = 6938(6) Å3, 1f: P21/
n, a = 17.697(10), b = 9.224(5), c = 21.933(12) Å, β = 112.50(1),
Z = 4, V = 3308(3) Å3].
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
lished synthetic routes for the preparation of the required
fluxional organic molecules, novel thio-based ligands with
multi-armed, tripodal geometry, such as pyridylsulfanyl-
methyl derivatives, were synthesized, and these ligands dem-
onstrated their significance in the supramolecular studies.[10]
Because of our continued interest in both molecular and
supramolecular synthesis,[11] we were motivated to study the
influence of such thio-based, flexible-armed molecules in
the creation of assemblies with tailor-made geometries that
possess cavities, channels, etc., and subsequently to evaluate
possible applications. Thus, we have synthesized a pyr-
idylsulfanyl compound 1,3,5-tris(4-pyridylsulfanylmethyl)-
2,4,6-trimethylbenzene (L1) and prepared its host–guest
complexes in the form of metal–organic hybrid assemblies
in which solvents are incorporated in the channels. Thus, in
this manuscript, we report on coordination polymers of L1
with different halides of HgII obtained by carrying out
supramolecular synthesis from different solvents as illus-
trated in Scheme 1.
Introduction
Design and synthesis of coordination polymers with ex-
otic supramolecular architectures in the solid state are of
current research interest because of the potential applica-
tions of the assemblies in the areas of separation technol-
ogy, catalysis, gas storage devices, etc.[1–5] Thus, there are
numerous reports of a myriad of supramolecular assemblies
of coordination polymers utilizing different types of organic
ligands possessing varied functionalities like carboxylates,
aza-donor groups, etc., in recent literature.[6,7] In general,
most of the assemblies known in the literature, however,
were synthesized by utilizing organic moieties as rigid,
spacer entities.[8] Thus, the crucial role of organic ligands
with respect to the geometry and position of the functional
groups was demonstrated in the formation of the desired
topology. Also, another important feature of organic li-
gands is their conformational flexibility, which has been uti-
lized in metal–organic framework structures in recent stud-
ies.[9] In this process, taking into account the well-estab-
[a] Solid State and Supramolecular Structural Chemistry Labora-
tory, Division of Organic Chemistry National Chemical Labo-
ratory,
Results and Discussion
Solid-State Structure of Complex [Hg(L1)Cl2]·(dmso)2 (1a)
Pune 411008, India
Fax: +91-2025902624
E-mail: vr.pedireddi@ncl.res.in
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Crystallization of a precipitate of L1 and HgCl2 from
dmso gave single crystals that were suitable for analysis by
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Eur. J. Inorg. Chem. 2007, 1150–1158

Metal–Organic Hybrids of HgII Halides
FULL PAPER
Scheme 1.
X-ray diffraction methods. The crystal structure determi- tion methods, and each HgII is connected to ligand L1 in
nation reveals that, as expected, the pyridyl N atoms of L1 exactly the same mode as that observed in 1a (Figure 3a).
form coordination bonds with HgII (Figure 1). The ob- The Hg–N distances are in the range 2.464–2.515 Å, and
served Hg–N bond distances (2.457–2.479 Å) are in agree- the Hg–Cl distances are 2.430 and 2.451 Å.
ment with distances presented in the literature.[12] Further,
Thus, in the crystals of 1b, dmf molecules are present in
each HgII is connected to two halide ions to form Hg–Cl the cavities like the dmso molecules in 1a, but both the dmf
bonds with distances of 2.458 and 2.491 Å. The pertinent molecules are disordered in 1b. Further, the symmetry-inde-
coordination bonds and angles are given in Table 1. Thus, pendent dmf molecules interact with each other through C–
each HgII with pentacoordination has a square-pyramidal H···O hydrogen bonds with C···O distances of 3.07 and
geometry. This interaction results in the formation of a cav- 3.13 Å. A typical hydrogen-bonding network between the
ity of dimension 9ϫ12 Å2 and each cavity is created by two dmf molecules is shown in the inset of Figure 3b. However,
molecules of L1 and HgII as shown in Figure 2a. The cavi- unlike in 1a, no interaction exists between symmetry-de-
ties are further aligned in a three-dimensional arrangement pendent molecules.
to yield channels (see Figure 2b), which are occupied by
dmso molecules (solvent of crystallization) that exist in
both ordered and disordered forms. Furthermore, both
types of dmso molecules exist as dimers independently
Supramolecular Structure of [Hg(L1)I2] (1c)
through the formation of C–H···O hydrogen bonds (see in-
sets in Figure 2a).
A precipitate of ligand L1 and HgI2 (used in a ratio of
2:3) from dmso gave 1c. Crystallographic details of 1c are
given in Table 2. In this structure, ligand L1 forms coordina-
Solid-State Structure of Complex [Hg(L1)Cl2]·(dmf)2 (1b)
tion bonds with HgII with Hg–N distances of 2.353–
A precipitate of ligand L1 with HgCl2 from dmf gave 2.440 Å. Furthermore, HgII forms Hg–I coordination
solvent-incorporated crystals as confirmed by X-ray diffrac- bonds with distances in the range 2.623–2.661 Å (Figure 4).
Figure 1. ORTEP drawing of the asymmetric unit in the coordination complex 1a, along with dmso molecules.
Eur. J. Inorg. Chem. 2007, 1150–1158
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J. PrakashaReddy, V. R. Pedireddi
Table 1. Selected bond lengths [Å] and bond angles [°] around the coordination sphere in complexes 1a–1f.
FULL PAPER
1a
1b
Hg–N(1)
Hg–N(2)
Hg–N(3)
Hg–Cl(1)
Hg–Cl(2)
2.457(7)
2.462(6)
2.479(6)
2.491(2)
2.458(2)
N(1)–Hg–N(2)
N(1)–Hg–N(3)
N(2)–Hg–N(3)
N(1)–Hg–Cl(1)
N(1)–Hg–Cl(2)
N(2)–Hg–Cl(1)
N(3)–Hg–Cl(1)
Cl(2)–Hg–Cl(1)
Cl(2)–Hg–N(2)
Cl(2)–Hg–N(3)
88.1(2)
86.5(2)
174.5(2)
92.0(2)
97.2(2)
89.8(2)
90.9(2)
170.7(7)
91.3(2)
88.8(2)
Hg–N(1)
Hg–N(2)
Hg–N(3)
Hg–Cl(1)
Hg–Cl(2)
2.464(4)
2.493(4)
2.515(4)
2.430(1)
2.451(1)
N(1)–Hg–N(2)
N(1)–Hg–N(3)
N(2)–Hg–N(3)
Cl(1)–Hg–N(2)
Cl(1)–Hg–N(1)
Cl(1)–Hg–N(3)
Cl(1)–Hg–Cl(2)
Cl(2)–Hg–N(3)
Cl(2)–Hg–N(1)
Cl(2)–Hg–N(2)
90.2(1)
178.3(1)
88.7(1)
99.4(1)
91.3(9)
87.5(9)
167.9(4)
91.3(9)
90.1(9)
92.7(1)
1c
1d
Hg(1)–N(1)
Hg(1)–I(1)
Hg(2)–N(2)
Hg(2)–N(3)
Hg(2)–I(2)
Hg(2)–I(3)
2.353(1)
2.634(2)
2.440(2)
2.406(2)
2.623(2)
2.653(2)
N(1)–Hg(1)–N(1)
N(1)–Hg(1)–I(1)
N(1)–Hg(1)–I(1)
I(1)–Hg(1)–I(1)
N(3)–Hg(2)–N(2)
N(2)–Hg(2)–I(2)
N(3)–Hg(2)–I(3)
N(3)–Hg(2)–I(2)
N(2)–Hg(2)–I(3)
I(2)–Hg(2)–I(3)
83.0(7)
Hg–N(2)
Hg–N(3)
Hg–Br(1)
Hg–Br(2)
2.342(1)
2.348(1)
2.520(2)
2.515(2)
N(2)–Hg–N(3)
N(2)–Hg–Br(1)
N(2)–Hg–Br(2)
N(3)–Hg–Br(1)
N(3)–Hg–Br(2)
Br(2)–Hg–Br(1)
119.6(4)
103.0(3)
101.2(3)
98.8(3)
101.0(3)
135.3(7)
104.7(4)
105.0(4)
140.0(9)
85.6(6)
102.2(4)
101.1(4)
107.8(4)
101.3(4)
143.8(7)
1e
1f
Hg(1)–N(1)
Hg(1)–Br(1)
Hg(2)–N(2)
Hg(2)–N(3)
Hg(2)–Br(2)
Hg(2)–Br(3)
2.421(2)
2.455(3)
2.346(2)
2.370(2)
2.485(3)
2.448(3)
N(1)–Hg(1)–N(1)
81.9(9)
Hg–N(1)
Hg–N(2)
Hg–Br(1)
Hg–Br(2)
2.310(2)
2.380(2)
2.486(4)
2.509(3)
N(1)–Hg–N(2)
N(1)–Hg–Br(1)
N(1)–Hg–Br(2)
N(2)–Hg–Br(2)
N(2)–Hg–Br(1)
Br(1)–Hg–Br(2)
116.7(9)
100.8(6)
103.5(6)
98.6(7)
N(1)–Hg(1)–Br(1) 102.0(4)
N(2)–Hg(2)–N(3)
88.1(7)
N(2)–Hg(2)–Br(2) 99.9(4)
N(2)–Hg(2)–Br(3) 105.4(4)
N(3)–Hg(2)–Br(2) 100.5(4)
N(3)–Hg(2)–Br(3) 99.6(3)
Br(1)–Hg(1)–Br(1) 148.1(1)
Br(3)–Hg(2)–Br(2) 148.0(1)
98.6(8)
139.7(1)
Figure 2. (a) Presentation of the cavities occupied by dmso molecules in the crystal structure of 1a. The different types of interaction
between the dmso molecules are shown in the insets. Disorder in dmso is omitted for purposes of clarity. (b) Three –dimensional formation
of the channels; the alignment of the cavities is shown in (a).
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Metal–Organic Hybrids of HgII Halides
FULL PAPER
Figure 3. (a) ORTEP drawing of the asymmetric unit in the crystal structure of 1b along with the solvent of crystallization, dmf. (b)
Arrangement of dmf molecules in the cavities, and the intermolecular interactions between the adjacent molecules are shown in the inset.
Table 2. Crystallographic data of metal complexes of L1, 1a–1f.
1a
1b
1c
1d
1e
1f
Empirical
formula
Formula mass
Crystal shape
Crystal color
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
(HgCl2)(C27H27N3S3)· (HgCl2)(C27H27N3S3)· (HgI2)3(C27H27N3S3)2 (HgBr2)(C27H27N3S3)· (HgBr2)3(C27H27N3S3)2 (HgBr2)(C27H27N3S3)·
2C2H6SO
917.44
blocks
colorless
triclinic
¯
P1
2C3H7NO
905.36
blocks
colorless
triclinic
¯
P1
C2H6SO
928.23
thin plates
colorless
monoclinic
P21/c
C3H7NO
922.19
thin plates
colorless
monoclinic
P21/n
2342.56
blocks
colorless
monoclinic
C2/c
2060.62
blocks
colorless
monoclinic
C2/c
9.049(2)
13.646(4)
16.298(4)
111.99(1)
90.43(1)
101.57(1)
1820.6(8)
2
8.979(3)
13.611(5)
16.355(5)
111.57(1)
92.37(1)
101.07(1)
1810.5(11)
2
27.661(7)
18.821(4)
15.786(4)
90
113.13(1)
90
17.950(5)
9.031(2)
22.200(6)
90
113.62(1)
90
26.753(15)
18.415(10)
14.940(7)
90
109.50(1)
90
17.697(10)
9.224(5)
21.933(12)
90
112.50(1)
90
γ [°]
V [Å3]
7558(3)
4
3297.3(15)
4
6938(6)
4
3308(3)
4
Z
Dcalcd. [gcm–3
]
1.674
1.661
2.059
1.870
1.973
1.852
T [K]
133
133
133
133
133
133
Mo-Kα
0.71073
4.693
46.54
0.71073
4.609
52.12
0.71073
8.730
46.66
0.71073
7.373
46.62
0.71073
10.295
46.82
0.71073
7.289
46.62
µ [mm–1
2θ range [°]
F(000)
]
912
900
4296
1800
3864
1788
Total reflections 15091
18822
7103
15672
5451
13942
4755
4747
4002
13554
4758
Unique reflns.
5225
[R (int)]
[0.0469]
[0.0468]
6481
425
0.747
0.0354
0.0928
[0.1232]
2929
339
0.927
0.0570
0.1374
[0.0543]
4411
356
1.380
0.0729
0.1558
[0.0255]
2542
339
1.265
0.0517
0.1493
[0.1469]
3305
320
1.142
0.1079
0.3029
No. reflns. used 4931
No. parameters 403
GOF on F2
R1 [IϾ2σ(I)]
wR2
1.512
0.0532
0.1486
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J. PrakashaReddy, V. R. Pedireddi
FULL PAPER
Figure 4. ORTEP drawing of the coordination geometry in the crystal structure of 1c.
Further, the coordination geometry around HgII in 1c is nected square grids with cavities (Figure 5a, b). However,
distorted tetrahedral and differs from the square pyrimidal the cavities could not be translated into channels in a three-
geometry observed in 1a and 1b. Thus, the coordination dimensional arrangement as the void space is filled by moi-
moieties in 1c yield a polymer network comprising intercon- eties from adjacent chains as shown in Figure 5c.
Figure 5. (a) Square-grid network mediated coordination polymers in the crystal structure of 1c. (b) Arrangement of two adjacent polymer
networks. (c) The three-dimensional arrangement of the coordination polymers. Each polymer network is shown in different colors.
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Metal–Organic Hybrids of HgII Halides
FULL PAPER
Solid-State Structures of Complexes of L1 with HgBr2 (1d–
1f)
shown in Figure 6. Such adjacent chains are held together
by C–H···N hydrogen bonds with H···N distances of 2.66–
2.89 Å, as observed in the structure of the free ligand (Sup-
porting Information) and form cavities of dimension
11ϫ16 Å2 (Figure 7), which are aligned in a three-dimen-
sional arrangement to yield channels. The channels are oc-
cupied by the solvent molecules dmso and dmf in 1d and
1f, respectively. Thus, 1d and 1f show some similarities with
1a and 1b in the formation of an open-frame network.
However, the metal coordination and geometry around
each HgII in 1d and 1f has a close resemblance to that of
1c. Further, the solvent molecules present in the channels
of the structures 1d and 1f do not interact with each other
but are bound to the host lattice through numerous inter-
molecular interactions.
However, complex 1e, obtained as concomitant crystals
along with 1d and 1f, crystallizes in the monoclinic space
group C2/c. Further, packing analysis reveals that the struc-
ture of 1e is identical to that formed by HgI2 (1c) in all
respects except for the difference of the halogen atoms. A
typical structural arrangement in complex 1e is shown in
Figure 8 for purposes of comparison with the structure of
1c.
The complexes formed by HgBr2 are quite intriguing and
in fact further reinforce the systematic changes generally
observed in the halogen series. Crystallization of a solid
mixture of L1 and HgBr2 from dmso and dmf gave concom-
itant crystals of two different morphologies from each sol-
vent. Structure analysis reveals that, while one of the mor-
phologies from each solvent [1d (dmso) and 1f (dmf)] corre-
sponds to a solvated structure such as for HgCl2 (1a and
1b, respectively), the other morphologies gave structures
without a solvent of crystallization (1e) like 1c formed by
HgI2.
Although 1d and 1f have similar unit cell parameters,
they are not isomorphous, as they crystallize in different
space groups, P21/c and P21/n, respectively. The full crystal-
lographic details are given in Table 2. However, structure
analysis reveals that both 1d and 1f are isostructural with
the formation of identical three-dimensional arrangements.
In a typical interaction, as shown in Figure 6, the ligand L1
interacts with HgII by forming Hg–N bonds (Table 1) to
yield an infinite coordination polymer chain.
Figure 6. Coordination polymer formed between L1 and HgBr2
yielding a chain.
Figure 8. Square-grid network found in the solid-state structure of
complex 1e.
Thus, out of the available three pyridyl moieties only two
interact with HgII. Also, each HgII is bonded to two Br
By comparing the crystal structures of the metal com-
atoms (Table 1). Thus, in 1d and 1f, the coordination geom- plexes described herein, it is clearly evident that the struc-
etry around each HgII atom is also distorted tetrahedral as tures obtained are in agreement with the proposition of
Figure 7. Representation of cavities formed by the interaction of the adjacent polymeric chains through C–H···N hydrogen bonds in the
crystal structures (a) 1d and (b) 1f, along with the solvent molecules dmso and dmf, respectively.
Eur. J. Inorg. Chem. 2007, 1150–1158
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J. PrakashaReddy, V. R. Pedireddi
FULL PAPER
utilization of pyridylsulfanyl ligands in the supramolecular
synthesis through either dative bonds (1a–1c, 1e) or a com-
bination of dative bonds and hydrogen bonds (1d and 1f).
Another intriguing feature of these metal complexes is the
systematic variation with the change in halogen. While
HgCl2 forms solvated structures, HgI2 forms structures ex-
clusively without solvents of crystallization.
One more interesting feature is the conformational
changes in ligand L1 that occur when the ligand is uncoor-
dinated and when it is in the different complexes (Figure 9).
It is apparent that all the metal complexes, except 1d and
1f, adopt the same conformation (cis, trans, trans), which is
different from that of the conformation observed in the
pure structure of L1 (cis, cis, cis). It is well known from the
literature that tripodal ligands like L1 show both types of
conformation observed in this study, but often the confor-
mation was attributed to the nature of the anion present in
the structures.
Conclusions
In conclusion, we have reported the solid-state structures
of metal–organic hybrids of conformationally flexible thio
ligand L1 with different mercuric halides. Complexes 1a–1f
were prepared and the supramolecular assembly networks
have been analyzed, and it is understood that all the com-
plexes have open-frame networks with void space. In com-
plexes 1a, 1b, 1d, and 1f, solvent of crystallization occupies
the void space, while in other structures (1c and 1e), the
void space was filled by the self-protrusion of functional
groups from adjacent molecules. In particular, the varia-
tions observed in the conformations of the ligand L1 are
intriguing and may provide further insight in modeling ex-
periments, especially for the evaluation of metal-hybrids as
catalysts, which has increased demands under the current
research themes.
Experimental Section
Synthesis of 1,3,5-Tris(4-pyridylsulfanylmethyl)-2,4,6-trimethylben-
zene
(L1):
1,3,5-tris-(bromomethyl)-2,4,6-trimethylbenzene
(399 mg, 1 mmol) was added to an ice-cooled solution of pyridine-
4-thiol (333 mg, 3 mmol) and KOH (560 mg, 10 mmol, slight ex-
cess) in methanol whilst stirring. The mixture was heated at reflux
for 48 h at 80 °C. The solution was poured into ice-cold water, the
crude product was filtered and separated by column chromatog-
raphy, and a colorless microcrystalline solid was obtained (L1) in
72% yield (m.p. 228–230 °C). Single crystals of L1 suitable for X-
ray diffraction were obtained from methanol solution after 2–3 d.
Preparation of Complex [Hg(L1)Cl2]·(dmso)2 (1a): A white precipi-
tate obtained by dissolving HgCl2 (81 mg, 0.3 mmol) and L1
(49 mg, 0.1 mmol) in methanol was filtered and dissolved in dmso
and allowed to slowly evaporate at room temperature. Within 48 h,
well-grown colorless single crystals of 1a were obtained in 36%
yield (m.p. 204–206 °C).
Preparation of Complex [Hg(L1)Cl2]·(dmf)2 (1b): A white precipitate
was obtained as described for 1a; however dmf was used instead
of dmso. After slow evaporation under ambient conditions, gave
colorless single crystals of 1b were obtained in 42% yield (m.p.
213–215 °C).
Figure 9. An overlay diagram of the molecular conformation of
ligand L1 in its crystal structure (gray) and also in the complexes
1a–1f. Brown and pink correspond to 1d and 1f.
Preparation of Complex [Hg(L1)I2] (1c): A solution of HgI2
(135 mg, 0.3 mmol) in methanol was added to a solution of L1
(49 mg, 0.1 mmol) in methanol, and a white precipitate was ob-
tained. The precipitate was filtered and dissolved in dmso to obtain
colorless crystals of 1c in 31% yield (m.p. 208–210 °C). The com-
plex 1c was also obtained by dissolving the precipitate in dmf and
by evaporating the solution under ambient conditions.
However, it is apparent from this study that the coordi-
nation environment of the metal species as well as denticity
of the ligands also may play a significant role in determin-
ing the conformation. In particular, the complexes formed
by HgBr2 are quite significant in this respect. Since, the
same halogen (Br) gave structures of both conformations,
which can be differentiated by the number of metal coordi-
nation centers, it may be understood that interaction with
three metal ions like HgII leads to strained crowding in a
cis, cis, cis geometry, which might have forced the transfor-
mation of the conformation to cis, trans, trans in 1e,
whereas in 1d and 1f, with only two HgII involved in com-
plex formation, the conformation is retained as such, as in
L1.
Preparation of Complexes [Hg(L1)Br2]·(dmso) (1d) and [Hg(L1)Br2]
(1e): A solution of HgBr2 (108 mg, 0.3 mmol) in methanol was
added to a solution of L1 (49 mg, 0.1 mmol) in methanol. The re-
sulting white precipitate was filtered and dissolved in dmso. Color-
less crystals of two morphologies (plates 1d and blocks 1e) were
obtained in 21 and 11% yields, respectively [m.p. 177–179 (1d) and
197–199 °C (1e)].
Preparation of Complex [Hg(L1)Br2]·(dmf) (1f): A solution of
HgBr2 (108 mg, 0.3 mmol) in methanol was added to a solution of
L1 (49 mg, 0.1 mmol) in methanol. The white precipitate obtained
1156
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Metal–Organic Hybrids of HgII Halides
FULL PAPER
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was filtered and dissolved in dmf. Colorless crystals of two mor-
phologies (blocks 1e; plates 1f) were obtained in 28 and 14% yields,
respectively, (1f: m.p. 184–186 °C).
Crystal Structure Determination: Good quality, single crystals of
L1 and 1a–1f, grown as described above, were carefully chosen with
the aid of a polarized optical microscope and glued to glass fiber
to mount on a X-ray diffractometer goniometer equipped with a
CCD area detector.[13] The data collection proceeded without any
complication and was processed using the Bruker suite of software.
The structures were determined and refined by using the
SHELXTL suite of programs, and absorption corrections were
made on all the crystals with SADABS.[14] All the non-hydrogen
atoms were refined anisotropically except a few atoms in 1d (one
atom) and 1f (nine atoms). All hydrogen atoms were placed in the
calculated positions.
[4]
[5]
[6]
[7]
[8]
[9]
The structural parameters are given in Table 2. All the intra- and
intermolecular distances were computed with PLATON soft-
ware.[15] The packing drawings were generated either by an XP
package of SHELXTL or Cerius2 of Accelrys, Inc. CCDC-625087–
625093 for L1 and 1a–1f, respectively, contain the supplementary
crystallographic 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.
Supporting Information (see footnote on the first page of this arti-
cle): Discussion of the structure of L1 and corresponding figures, its
crystallographic information and powder X-ray diffraction patterns
(both experimental and simulated from crystal data) are given.
Acknowledgments
We thank Dr. S. Sivaram (Director, NCL) and Dr. K. N. Ganesh
(Head of Organic Division, NCL) for their constant support and
encouragement. Also, we acknowledge the financial assistance of
DST and BRNS for the ongoing projects. One of us (J. P.) thanks
the Council of Scientific and Industrial Research (CSIR), New
Delhi for a research fellowship.
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Received: September 16, 2006
Published Online: February 2, 2007
1158
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Eur. J. Inorg. Chem. 2007, 1150–1158