Two-dimensional holo- and hemidirected lead(II) coordination polymers: Synthetic, spectroscopic, thermal, and structural studies of [Pb(μ-SCN) 2(μ-ebp)1.5]n and {[Pb(μ-OAc)(μ-ebp)] (ClO4)}n (ebp = 4,4′-[(1E)-ethane-1,2-diyl] bis[pyridine]; OAc = Acetato)

Article abstract of DOI:10.1002/hlca.200590187

Two new coordination polymers of Pb¹¹ complexes with bridging 4,4′-[(1E)-ethane-1,2-diyl]bis[pyridine] (ebp), thiocyanato, and acetato ligands, [Pb(μ-SCN)₂(μ-ebp)_1.5]_n (1) and {[Pb(μ-OAc)(μ-ebp)](ClO₄)}_n (2), were synthesized and characterized by elemental analysis, FT-IR, ¹H- and ¹³C-NMR, thermal analysis, and single-crystal X-ray diffraction. In 1, the Pb²⁺ ions are doubly bridged by both the ebp and the SCN ^- ligands into a two-dimensional polymeric network. The seven-coordinate geometry around the Pb²⁺ ion in 1 is a distorted monocapped trigonal prism, in which the Pb²⁺ ions have a less-common holodirected geometry. In 2, the Pb²⁺ ions are bridged by AcO ^- ligands forming linear chains, which are also further bridged by the neutral ebp ligands into a two-dimensional polymeric framework. The Pb ²⁺ ions have a five-coordinate geometry with two N-atoms from two ebp ligands and three O-atoms of AcO^-. Although ClO₄ acts as a counter-ion, it also makes weak interactions with the Pb²⁺ center. The arrangement of the ligands in 2 exhibits hemidirected geometry, and the coordination gap around the Pb²⁺ ion is possibly occupied by a configurationally active lone pair of electrons.

Full text of DOI:10.1002/hlca.200590187

Helvetica Chimica Acta Vol. 88 (2005)
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Two-Dimensional Holo- and Hemidirected Lead(II) Coordination
Polymers: Synthetic, Spectroscopic, Thermal, and Structural Studies of
[Pb(m-SCN)2(m-ebp)1.5]n and {[Pb(m-OAc)(m-ebp)](ClO4)}n
(ebp ˆ 4,4'-[(1E)-Ethane-1,2-diyl]bis[pyridine]; OAc ˆ Acetato)
by Ali Morsali*a), Veysel T. Yilmaz*b), Canan Kazakc), and Long-Guan Zhud)
a) Department of Chemistry, School of Science, Tarbiat Modarres University, P. O. Box 14155-4838, Tehran,
Iran
b) Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Kurupelit,
Samsun, Turkey
c) Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Kurupelit, Samsun,
Turkey
d) Department of Chemistry, Zhejiang University, Hangzhou, 310027, P. R. China
Two new coordination polymers of PbII complexes with bridging 4,4'-[(1E)-ethane-1,2-diyl]bis[pyridine]
(ebp), thiocyanato, and acetato ligands, [Pb(m-SCN)2(m-ebp)1.5
] (1) and {[Pb(m-OAc)(m-ebp)](ClO4)}n (2),
n
were synthesized and characterized by elemental analysis, FT-IR, 1H- and 13C-NMR, thermal analysis, and
single-crystal X-ray diffraction. In 1, the Pb2‡ ions are doubly bridged by both the ebp and the SCNÀ ligands into
a two-dimensional polymeric network. The seven-coordinate geometry around the Pb2‡ ion in 1 is a distorted
monocapped trigonal prism, in which the Pb2‡ ions have a less-common holodirected geometry. In 2, the Pb2‡
ions are bridged by AcOÀ ligands forming linear chains, which are also further bridged by the neutral ebp ligands
into a two-dimensional polymeric framework. The Pb2‡ ions have a five-coordinate geometry with two N-atoms
from two ebp ligands and three O-atoms of AcOÀ. Although ClOÀ4 acts as a counter-ion, it also makes weak
interactions with the Pb2‡ center. The arrangement of the ligands in 2 exhibits hemidirected geometry, and the
coordination gap around the Pb2‡ ion is possibly occupied by a configurationally active lone pair of electrons.
Introduction. Crystal engineering of metallo-organic frameworks has been of
great interest due to the preparation of new coordination polymers exhibiting specific
topologies [1]. It is possible to build crystalline metal complexes in one, two, or three
dimensions, and the key factor for the design of such metal complexes is to use
polyfunctional ligands capable to bridge metal centers to form polymeric structures [2].
The construction of coordination polymers has achieved great progress in forming
interesting architectures with novel properties such as magnetism [3], electrical
conductivity [4], nonlinear optical behavior [5], luminescence [6], and porosity [7].
PbII Complexes are frequently discussed with respect to the coordination and
configurational activity of heavy metals with valence-shell-electron lone pairs [8],
which are responsible for coordination-sphere distortions. The possible configurational
activity of the lone pair in divalent PbII compounds has recently been discussed by
Shimoni-Livny et al. [9], based on the crystal data available in the Cambridge Structural
Database. These authors classified the lead coordination geometry as −holodirected×,
when the bonds to ligand atoms are directed throughout the surface of an
encompassing sphere, and as −hemidirected× in cases where the bonds are directed
¹ 2005 Verlag Helvetica Chimica Acta AG, Z¸rich

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throughout only a part of the coordination sphere, leaving a gap in the distribution of
bonds to the ligands.
The 4,4'-[(1E)-ethane-1,2-diyl]bis[pyridine] (ebp) ligand is known to form poly-
nuclear complexes with transition metals [10] and may also be a good candidate as a
bridging ligand for the investigation of the configurational activity of valence-shell
electron lone pairs in PbII. Moreover, the architectures of coordination polymers or
supramolecular compounds constructed from PbII ions and the ebp ligand have not
been reported so far. In this paper, we report the preparations and crystal structures of
two new PbII coordination polymers, namely [Pb(m-SCN)2(m-ebp)1.5]n (1) and {[Pb(m-
OAc)(m-ebp)](ClO4)}n (2), involving the spontaneous aggregation of two bridging
ligands, ebp and thiocyanato (SCNÀ) in 1 and ebp and acetato (AcOÀ) in 2.
Results. The IR spectra of 1 and 2 display characteristic absorption bands for ebp,
SCNÀ and AcOÀ ligands. The relatively weak absorption bands at ca. 2900 and
3050 cmÀ1 are due to the CÀH modes involving the ring and ethene H-atoms. In the IR
spectrum of 1, very strong bands centered at 2025 and 814 cmÀ1 characterize the nÄ(CN)
and nÄ(CS) vibrations of the bridging SCN-group, respectively, while the sharp band at
536 cmÀ1 is attributed to the d(SCN) vibration [11]. The bridging [MÀSCNÀM]
complexes with divalent transition-metal ions is expected to show nÄ(CN) above
2100 cmÀ1 [11], but the significantly lower frequency for the nÄ(CN) vibration of 1 may
be due to the presence of PbII with a relatively large ionic radius relative to that of
transition metals. However, the n(CN) frequency of 1 is comparable to those observed
in the corresponding PbII polymers containing thiocyanate [12]. The absorption bands
with variable intensity in the frequency range 1407 1587 cmÀ1 correspond to ring
vibrations of the pyridine moiety of the ebp ligand. The IR spectrum of 2 presents
strong absorption bands at 615, 1079, and 1100 cmÀ1 for the vibrations of the ClOÀ4
anion. The symmetric and asymmetric vibrations of the COOÀ group are observed at
1479 and 1592 cmÀ1 as sharp absorption bands, respectively. The D(nasym À nsym) value of
113 cmÀ1 indicates that the AcOÀ anions coordinate to the PbII centers in a bridging
mode [13].
The thermal-decomposition behavior of both 1 and 2 was investigated in flowing N2
and under a static air atmosphere. It was shown that each complex exhibits similar
decomposition pathways under both N2 and air. Compound 1 does not melt and is
stable up to 2058, at which temperature it begins to decompose. Removal of the ebp
ligands takes place between 205 and 5008 with an endothermic effect at 2728 and two
exothermic effects at 335 and 4688. The experimental mass loss of 46.1% is consistent

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with the calculated value 45.8% for the elimination of 1.5 mol of ebp. The solid residue
formed at ca. 5008 is suggested to be Pb(SCN)2, based on the IR spectrum of this
residue showing characteristic absorption peaks of the thiocyanate anion at ca.
2100 cmÀ1. At higher temperatures, evaporation or decomposition of the residue
occurs. Compound 2 is stable up to 2508 and decomposes with a continuous weight loss.
Due to the presence of the ClOÀ4 anion, 2 was found to be highly explosive in both N2
and air and two peaks at 350 and 3708 of violently exothermic reactions arise from the
explosion of the compound, leaving an empty crucible. The thermal observations
suggest that 2 may be a good candidate for energetic materials.
A view of the coordination environment around the Pb2‡ ion in 1 is shown in Fig. 1,
and Table 1 lists selected bond distances and angles. Single-crystal X-ray-diffraction
analysis reveals that the Pb2‡ ion of 1 is coordinated by four SCNÀ1 and three neutral
ebp molecules, resulting in a seven-coordinate complex with a PbN5S2 chromophore.
Although the coordination geometry around the Pb2‡ ion is irregular, presumably
associated with the steric constraints arising from the shape of the present ligands, it is
Fig. 1. View of the coordination environment around lead(II) in 1 with atom-labeling scheme and thermal
ellipsoids at the 40% probability level (small spheres for the H-atoms). Symmetry codes: i ˆ x À 1, 1 ‡ y, z;
ii ˆ À x, 1 À y, 1 À z; iii ˆ Àx, 1 À y, À z; iv ˆ À 1 À x, 2 À y, 1 À z.
Table 1. Selected Geometric Data for 1. For symmetry codes i iii, see Footnotes a c.
Length [ä]
Angles [8]
Angles [8]
Pb(1)ÀS(1)
2.900(2)
3.062(2)
2.612(5)
2.966(7)
2.801(4)
2.540(6)
2.785(7)
N(1)ÀPb(1)ÀS(1)
83.44(13)
91.04(13)
143.91(11)
145.60(12)
75.62(19)
79.79(18)
109.20(16)
85.58(16)
70.46(16)
135.22(16)
73.25(16)
N(3)ÀPb(1)ÀS(1)
N(3)ÀPb(1)ÀS(2)
N(3)ÀPb(1)ÀN(4)b)
N(3)ÀPb(1)ÀN(5)c)
N(4)b)ÀPb(1)ÀS(1)
N(4)a)ÀPb(1)ÀS(2)
N(4)b)ÀPb(1)ÀN(5)c)
N(5)c)ÀPb(1)ÀS(1)
N(5)c)ÀPb(1)ÀS(2)
S(1)ÀPb(1)ÀS(2)
80.82(13)
94.27(13)
74.42(11)
122.79(10)
91.22(16)
70.24(16)
151.2(2)
71.12(15)
125.40(16)
161.44(5)
Pb(1)ÀS(2)
Pb(1)ÀN(1)
Pb(1)ÀN(2)a)
Pb(1)ÀN(3)
Pb(1)ÀN(4)b)
Pb(1)ÀN(5)c)
N(1)ÀPb(1)ÀS(2)
N(1)ÀPb(1)ÀN(2)a)
N(1)ÀPb(1)ÀN(3)
N(1)ÀPb(1)ÀN(4)b)
N(1)ÀPb(1)ÀN(5)c)
N(2)a)ÀPb(1)ÀS(1)
N(2)a)ÀPb(1)ÀS(2)
N(2)a)ÀPb(1)ÀN(3)
N(2)a)ÀPb(1)ÀN(4)b)
N(2)a)ÀPb(1)ÀN(5)c)
a) i ˆ x À 1, 1 ‡ y, z. b) ii ˆ À x, 1 À y, 1 À z. c) iii ˆ Àx, 1 À y, z.

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best described as a distorted monocapped trigonal prism. The S(1)ÀPb(1)ÀS(2) and
N(4)iiÀPb(1)ÀN(5)iii bonds with SCNÀ form the equatorial plane (for symmetry codes
ii and iii, see Table 1), and their bond angles are 161.44(5) and 151.2(2)o, respectively,
while the N(1) atom occupies the axial position and the N(2) and N(3) atoms are
placed in the pseudoaxial positions as shown in Fig. 1.
Complex 1 is a two-dimensional neutral metallopolymer as illustrated in Fig. 2. The
2‡
complex crystallizes in the triclinic space group P 1and consists of the Pb
ions
bridged by both ebp and SCNÀ ligands, thus forming a two-dimensional, infinite
framework. On the other hand, the structure may be considered a coordination polymer
of PbII consisting of one-dimensional linear chains, running parallel to the c axis, with a
building block of [Pb(SCN)2]. Two SCNÀ anions doubly bridge two Pb2‡ ions via the N
and S atoms with bond distances Pb(1)ÀS(1) ˆ 2.900(2) ä, Pb(1)ÀS(2) ˆ 3.062(2) ä,
Pb(1)ÀN(4)ii ˆ 2.540(6) ä and Pb(1)ÀN(5)iii ˆ 2.785(7) ä. The two PbÀS bond
distances in 1 are practically similar, but significantly shorter than those found in the
reported Pb2‡ complexes with thiocyanate [12]. The intrachain Pb ¥¥¥ Pb distances
Fig. 2. Fragment of the two-dimensional framework in 1 viewed along the a-axis. H-Atoms of CH groups are
omitted for clarity.

Helvetica Chimica Acta Vol. 88 (2005)
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within the [Pb(SCN)2]n chains are 5.291and 6.149 ä. The individual polymeric chains
are almost parallel to each other and further bridged by bidentate bridging ebp ligands,
with bond distances Pb(1)ÀN(1) ˆ 2.612(5) ä, Pb(1)ÀN(2)i ˆ 2.966(7) ä and
Pb(1)ÀN(3) ˆ 2.801(4) ä, resulting in a two-dimensional framework, as shown in
Fig. 2 (for symmetry code i, see Table 1). The Pb(1)ÀN(2)i and Pb(1)ÀN(3) bond
distances are significantly longer than the third PbÀN (ebp) bond, and the lengthening
of the PbÀN(ebp) bonds is explained by the poor overlap of the sp3 lone pair on the
N-atoms of ebp with the valence orbitals of the adjacent Pb2‡ ion, due to steric
constrains.
The two pyridine rings of the ebp ligand are essentially planar with an r.m.s.
deviation of ca. 0.035 ä. However, atoms C(6) and C(7) are displaced from the
pyridine best planes by 0.043(4) and 0.339(4) ä, respectively. The C(18) atom and its
symmetry equivalent partner also deviate by the same amount as atoms C(6) and C(7).
Since the inversion center is located at the middle of the C(18)ÀC(18)iv bond
(symmetry code iv ˆ À1 À x, 2 À y, 1 À z], the aromatic rings of the ebp ligand are
suppose to be coplanar, and the whole ebp molecule may be considered flat, because
the dihedral angle between the two pyridine rings within the ebp ligand is only 2.40(3)8.
The structure of 1 does not exhibit conventional H-bonds. In the crystal packing,
the two-dimensional layers are shifted against each other by half of the distance
between two Pb2‡ centers connected by the ebp ligands, and are held together by
aromatic p p stacking interactions between the pyridine fragments of the ebp ligands
in the adjacent layers, with average centroid centroid distances of 3.68(5) ä.
The fundamental building unit of the crystal structure of 2 is shown in Fig. 3, and
selected bond lengths and angles are listed in Table 2. Complex 2 crystallizes in the
‡
orthorhombic space group Pna21. The structure consists of [Pb(m-OAc)(m-ebp)]
cations and ClOÀ4 anions. Some of the O atoms (C2 C4) of the ClO4 anion are
disordered over two positions with essentially equal occupancy. The complex cation is a
Fig. 3. Molecular view of the building-block unit in 2 with atom-labeling scheme and thermal ellipsoids at the
40% probability level (small spheres for the H-atoms)

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Table 2. Selected Geometric Data for 2. For symmetry codes i v, see Footnotes a e.
Length [ä]
Angle [8]
Angle [8]
Pb(1)ÀN(1)
Pb(1)ÀN(2)a)
Pb(1)ÀO(5)
Pb(1)ÀO(6)
Pb(1)ÀO(6)b)
Pb(1)ÀO(3)b
Pb(1)ÀO(5)c)
2.646(13)
2.606(10)
2.464(8)
2.579(8)
2.471(10)
2.938(7)
2.962(8)
O(5)ÀPb(1)ÀO(6)
50.3(3)
O(6)ÀPb(1)ÀN(1)
O(6)ÀPb(1)ÀN(2)a)
O(6)b)ÀPb(1)ÀN(1)
91.2(5)
90.4(4)
82.1(5)
O(5)ÀPb(1)ÀO(6)b) 69.3(3)
O(5)ÀPb(1)ÀN(1)
80.1(4)
81.4(3)
O(5)ÀPb(1)ÀN(2)a)
O(6)b)ÀPb(1)ÀN(2)a) 74.9(5)
O(6)ÀPb(1)ÀO(6)b) 119.4(3)
N(1)ÀPb(1)ÀN(2)a)
154.4(4)
DÀH ¥¥¥ A
d(DÀH) [ä] d(H ¥¥¥ A) [ä] d(D ¥¥¥ A) [ä] < (DÀH ¥¥¥ A) [8]
C(1)ÀH(1) ¥¥¥ O(5)
0.93
0.93
2.52
2.50
2.56
2.36
2.50
3.17(2)
3.36(5)
3.20(2)
3.19(6)
3.35(2)
126
154
127
148
151
C(5)ÀH(5) ¥¥¥ O(3)a
C(2)ÀH(2) ¥¥¥ O(2)bd) 0.93
C(4)ÀH(4) ¥¥¥ O(4)be) 0.93
C(9)ÀH(9) ¥¥¥ O(1)d)
0.93
a) i ˆ x À 1/2, y À 1/2, 1/2 ‡ z. b) ii ˆ x À 1/2, 1/2 À y, z. c) iii ˆ 1/2 ‡ x, 1 /2À y, z. d) iv ˆ 1/2 À x, y À 1/2, 1/2 ‡ z.
e) v ˆ 1 À x, 1 À y, 1 /2‡ z.
two-dimensional framework, in which Pb2‡ ions are bridged by both AcOÀ and ebp
ligands as illustrated in Fig. 4. The COOÀ moiety of the AcOÀ ligand act as both
bidentate and bridging group (totally tridentate) in a m-1,3 mode, where the two O-
atoms of the COOÀ group bidentately coordinate to a Pb2‡ ion, creating a four-
membered chelate ring, and one of them also bridges two adjacent Pb2‡ ions, yielding a
one-dimensional chain. The intrachain distance between two neighboring Pb2‡ ions is
4.312 ä. These one-dimensional chains running parallel to the a axis are further linked
by the ebp ligands, which behave as bidentate bridging ligands via two N-atoms, thus
creating a two-dimensional coordination polymer as shown in Fig. 4.
The Pb2‡ ions in 2 are five-coordinate of the PbO3N2 type. The calculated structural
index parameter t value of 0.57 reflects a significantly distorted trigonal-bipyramidal
geometry since the t values of square-based-pyramidal and trigonal-bipyramidal
extremes are 0 and 1, respectively [14]. The best equatorial trigonal plane is defined by
atoms O(6)ii, Pb(1), O(6), and O(5) with a torsion angle of À 4.78, while the N(1) and
N(2) atoms occupy the axial positions (N(1)ÀPb(1)ÀN(2)i ˆ 154.4(4)8) (for symmetry
codes, see Table 2). The large distortion in the coordination polyhedron of 2 may be the
consequence of a very small bite angle (50.3(3)8) of the AcOÀ ligand, which is similar to
that found in [Pb(H2O)(OAc)(sac)]n (sac ˆ saccharinato) [15].
The PbÀN distances of 2.606(10) and 2.646(13) ä are significantly shorter in 2 than
the corresponding distances in 1. The PbÀO(bidentate AcO) distances are 2.464(8)
and 2.579(8) ä, while the PbÀO(bridging AcO) distance is 2.471(10) ä. The
PbÀO(AcO) distances are significantly different from those reported for [Pb(en)-
(OAc)(NO3)]n [44], [Pb(phen)(OAc)(ClO4)]n [16], [Pb(phen)(OAc)(NO3)] [17],
[Pb(bpy)(OAc)(ClO4)] [18], [Pb(phen)(OAc)2]2 ¥ 4 H2O [19] and [Pb(dpa)2(OAc)2]n
[20] (en ˆ ethane-1,2-diamine, phenˆ 1,10-phenanthroline, dpaˆ di(pyridin-2-yl)-
amine). There are also weak interactions of Pb2‡ with the O(5) atom of adjacent
AcOÀ anions (Pb ¥¥¥ O(5)iii ˆ 2.962(8) ä) and the O(3) atom of the ClOÀ4 anion (Pb ¥¥¥
O(3b) ˆ 2.938(7) ä).

Helvetica Chimica Acta Vol. 88 (2005)
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Fig. 4. Fragment of the two-dimensional layer in 2 viewed along the b-axis. H-Atoms of CH groups are omitted
for clarity, and dashed lines indicate weak interactions of PbIII with some O-atoms of the AcO ligands and ClOÀ4
anions.
The pyridine rings of the ebp ligand, (C(1) to C(5), and N(1)) and (C(8) to C(10),
and N(2)) are essentially planar with r.m.s. deviations of ca. 0.010 ä. In contrast to 1,
the ebp ligand in 2 is not flat, since the dihedral angle between the two pyridine rings is
27.23(5)8. The two- dimensional layers of 2 are held together by aromatic p p stacking
interactions of ca. 3.72(2) ä and weak CH ¥¥¥ O interactions as listed in Table 2.
Discussion. PbII Complexes 1 and 2, two new two-dimensional coordination
polymers, were prepared by the branch-tube method and structurally characterized.
Their crystal structures are consistent with the results obtained from the physical-
characterization measurements. Complexes 1 and 2 are the first two-dimensional PbII
frameworks with the bridging ebp ligand. In addition to ebp, 1 contains bridging SCNÀ
ions, whereas 2 is a mixed-anion compound with bridging AcOÀ ions and ClO4À as
counter-ion.
It is very interesting to note that, although 1 and 2 show similar polymeric networks,
their Pb2‡ ions exhibit different coordination geometries. Shimoni-Livny et al. [9]
stated that hemidirected geometry (see Introduction) is present in all Pb2‡ compounds

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with coordination numbers as low as 2 5 and also quite common for coordination
numbers 6 8, while holodirected geometry (see Introduction) becomes dominant at
higher coordination numbers such as 9 and 10. Furthermore, holodirected geometry is
also favored at the intermediate coordination numbers 6 8 in the presence of soft and
bulky ligands.
The Pb2‡ ion in 1 is seven-coordinate, and the direction of the PbÀN and PbÀS
bonds shows that the coordination around the Pb2‡ ion in this complex is holodirected.
Therefore, the arrangement of ebp and SCNÀ ligands do not leave any gap or hole in
the coordination sphere around the PbII atom, indicating that the electron lone pair of
PbII is inactive. The presence of four anionic SCNÀ and three bulky ebp ligands
increases steric crowding around the PbII atom and results in strong interligand
repulsions. This may be the reason of the disappearance of the gap in the coordination
polyhedron, thereby resulting in the less-common holodirected geometry. This is in
accord with the holodirected eight-coordinate Pb2‡ ions in [Pb(bpy)(NO3)(SCN)]n
containing the bulky 4,4'-bipyridine (bpy) ligand together with two different anionic
species [8].
The Pb2‡ ion in 2 is five-coordinate and displays hemidirected geometry with a
configurationally active lone pair as expected. Additionally, the O(6)ÀPbÀO(6)ii angle
of 119.4(3)8 suggests that there is a hole in the coordination sphere of 2 due to lone-
pair/bond-pair repulsion. The hybrid orbital containing the putative electrons lone pair
is possibly located at the trans position to the shorter PbÀO bond, and the observed
shortening of this PbÀO bond (bond distances for Pb(1)ÀO(5), Pb(1)ÀO(6) and
Pb(1)ÀO(6)ii of 2.464(8), 2.579(8), and 2.471(10) ä, resp.) supports the presence of
this feature [21]. It is important to note that the presence of a lone pair is not directly
determined, but it is deduced from the spatial distribution of the donor atoms of ligands
around the metal center. Therefore, the identification of these donors is essential for
the analysis of any particular system. For example, in 2, the coordination number of 5
was estimated assuming an upper limit of ca. 2.75 ä for PbÀdonor atom interactions,
and, therefore, a hemidirected coordination sphere was established due to the PbÀN
and PbÀO bond distances ranging from 2.464(8) to 2.646(13) ä. However, if the
weaker PbÀO separations over 2.9 ä are taken into consideration, the coordination
number becomes 7. In this case, PbII ions in 2 are still hemidirected, because the
O(6)ÀPbÀO(6)ii angle of 119.4(3)8 was not influenced by the coordination of the
perchlorate anion, due to occupation of this site by the configurationally active electron
lone pair at the PbII atom. It may be concluded that the identification of a lone pair is
not readily achieved in mixed-ligand PbII coordination polymers when relatively weak
donors are present.
This work was supported financially by the Tarbiat Modarres University, Iran, and the Ondokuz Mayis
University, Turkey.
Experimental Part
General. Thermal-analysis curves (TG and DTA): Rigaku-TG8110 thermal analyzer; heating rate
108 minÀ1 in flowing N2 or under a static air atmosphere. FT-IR Spectra: Perkin-Elmer 597 spectrophotometer,
KBr pellets; 4000 400 cmÀ1 range. NMR Spectra: Bruker DRX-500-Avance spectrometer, d in ppm. Elemental
analyses: Heraeus CHN-O-Rapid Analyzer for C, H, and N.

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Sesqui{4-[2-(pyridin-4-yl)ethyl]pyridine-kN}bis(thiocyanato-kS)lead Homopolymer ([Pb(m-SCN)2(m-
ebp)1.5]n; 1). The so-called −branch-tube× method was used: ebp (0.180 g, 1 mmol) was placed in one arm of
the branched tube, and mixtures of lead(II) acetate (0.36 g, 1mmol) and KSCN (1.96 g, 2 mmol) in the other.
MeOH was carefully added to fill both arms. The tube was sealed and the ligand-containing arm was immersed
in a bath at 608 while the other was at r.t. After 15 d, colorless crystals were collected in the cooler arm. They
were filtered off, washed with acetone and Et2O, and air-dried: 1 (45%). M.p. 2058 (dec.). 1H-NMR (DMSO):
7.53 (s, 2 H), 7.60 (d, 4 H): 8.60 (d, 4 H). 13C-{1H}-NMR (DMSO): 121.2; 130.6; 143.3; 150.20. Anal. calc. for
C20H15N5PbS2: C 40.22, H 2.51, N 11.73; found: C 40.35, H 2.25, N 11.60.
(Acetato-kO,kO'){4-[2-(pyridin-4-yl)ethyl]ethyl]pyridine-kN}lead(1‡) Perchlorate Homopolymer ({[Pb(m-
OAc)(m-ebp)](ClO4)}n; 2). As described for 1, but with NaClO4 replacing KSCN. After 20 d, white crystals were
deposited in the cooler arm: 2 (40%) M.p. 2508 (dec). 1H-NMR (DMSO): 1.729 (s, 3 H); 7.53 (s, 2 H); 7.60 (d,
4 H); 8.60 (d, 4 H). 13C-{1H} NMR (DMSO): 27.536 (MeCOO); 178.817 (MeCOO); 121.242, 130.567, 143.337,
150.183. Anal. calc. for C14H13ClN2O6Pb: C 30.69, H 2.39, N 5.11; found: C 30.80, H 2.50, N 5.30.
X-Ray Crystallography. Intensity data for 1 and 2 were collected with a Stoe-IPDS-2 diffractometer
(MoÀKa radiation, l 0.71073 ä) at 293(2) K. The structures were solved by direct methods and refined by full-
matrix least-squares techniques on F2. All H-atoms were placed in idealized locations and refined by riding on
their carrier atoms. Crystal data of 1: C20H15N5PbS2, M 596.71; crystal dimensions 0.33 Â 0.27 Â 0.20 mm;
triclinic, P À 1; a ˆ 9.899(2), b ˆ 9.989(2), c ˆ 11.425(2) ä, a ˆ 107.910(15), b ˆ 104.464(16), g ˆ 90.894(16)8;
Z ˆ 2, Vˆ 1035.7(4) ä3, Dc ˆ 1.913 g/cm3; m ˆ 8.361mm À1; F(000) ˆ 568, q range ˆ 2.14 28.668; reflections
collected (independent) ˆ 18793 (5273), R1(wR1) ˆ 0.0399 (0.0757). Crystal data of 2: C14H13ClN2O6Pb, M
547.90, crystal dimensions 0.50  0.30  0.16 mm; orthorhombic, Pna21; a ˆ 7.4359(3), b ˆ 16.5857(11), c ˆ
13.6191(6) ä, Z ˆ 4, Vˆ 1679.64(15) ä3, Dc ˆ 2.167 g/cm3; m ˆ 10.236 mmÀ1, F(000) ˆ 1032; q range ˆ 1.93
27.508; reflections collected (independent) ˆ 26548 (2013); R1(wR1) ˆ 0.0369 (0.0940). CCDC Nos. 253686
and 248252 contain the supplementary crystallographic data for 1 and 2, respectively. These data can be obtained
free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Received March 14, 2005