Synthesis and structural characterization of five new coordination polymer chain structures using a new, Z-shaped ligand, 2,2′-bis-(4-pyridylethynyl) tolane

Article abstract of DOI:10.1007/s10870-005-2801-8

Using the new ligand, 2,2′-bis-(4-pyridylethynyl)tolane we have synthesized five new coordination polymers: HgBr₂[2,2′-bis-(4- pyridylethynyl)tolane] (1), HgI₂[2,2′-bis-(4-pyridylethynyl) tolane] (2), Ni(acetylacetonate)₂[

Full text of DOI:10.1007/s10870-005-2801-8

Journal of Chemical Crystallography, Vol. 35, No. 2, February 2005 (ꢀC 2005)
DOI: 10.1007/s10870-005-2801-8
Synthesis and structural characterization of five new
coordination polymer chain structures using a new,
Z-shaped ligand, 2,2ꢀ-bis-(4-pyridylethynyl)tolane
Jeffrey E. Fiscus,(1,3) Neil Pschirer,(1) Rachael E. Hipp,(1) Andrea M. Goforth,(1)
Craig Chapman,(1) Sandra Shotwell,(1) Ralph C. Layland,(2) Mark D. Smith,(1)
∗
Uwe H.F. Bunz,(1,4) and Hans-Conrad zur Loye(1)
Received August 12, 2004; accepted September 14, 2004
Using the new ligand, 2,2ꢁ-bis-(4-pyridylethynyl)tolane we have synthesized five new
coordination polymers: HgBr2[2,2ꢁ-bis-(4-pyridylethynyl)tolane] (1), HgI2[2,2ꢁ-bis-
(4-pyridylethynyl)tolane] (2), Ni(acetylacetonate)2[2,2ꢁ-bis-(4-pyridylethynyl)tolane]
(3), Zn(acetylacetonate)2[2,2ꢁ-bis-(4-pyridylethynyl)tolane] (4), and Cu(hexafluoro
acetylacetonate)2[2,2ꢁ-bis-(4-pyridylethynyl)tolane]·CHCl3
(5).
2,2ꢁ-Bis-(4-pyridyl
ethynyl)tolane is a rigid ligand with a Z-shape that promotes the formation of zig-zag chains.
Compounds 1–5 were characterized by single crystal X-ray diffraction; and compounds 1–3
were additionally characterized by IR, elemental analysis, and thermogravimetric analysis.
˚
Compound 1 crystallizes in the monoclinic space group C2/c with a = 29.761(3) A,
◦
3
˚
˚
˚
b = 5.0531(5) A, c = 16.7823(15) A, β = 104.090(2) , V = 2447.9(4) A , Z = 4. Each
mercury is bound to two tolane ligands and two bromine anions, resulting in a tetrahedral
coordination environment. Compound 2 crystallizes in the monoclinic space group
◦
˚
˚
˚
P2/c, with a = 20.3061(17) A, b = 5.6303(5) A, c = 24.5459(19) A, β = 110.338(2) ,
3
˚
V = 2631.4(4) A , Z = 4. Here also, each mercury is bound to two tolane ligands and
two iodine anions in a tetrahedral coordination environment. The ligand orientation differs
in compounds 1 and 2 being trans oriented in 1 and cis oriented in 2. Compound 3 crys-
˚
˚
tallizes in the monoclinic space group P21/c with a = 14.5947(14) A, b = 6.3082(6) A,
◦
3
˚
˚
c = 18.3939(18) A, β = 112.112(2) , V = 1568.9(3) A , Z = 2. Each nickel is bound to
two tolane ligands and two bidentate AcAc anions, resulting in an octahedral coordination
environment. Compound 4, which is isostructural with 3, also crystallizes in the monoclinic
˚
˚
˚
space group P21/c with a = 14.6990(9) A, b = 6.2724(4) A, c = 18.6433(11) A,
◦
3
˚
β = 112.8610(10) , V = 1583.86(17) A , Z = 2. Compound 5 crystallizes in the
˚
˚
˚
triclinic space group P-1 with a = 6.5487(4) A, b = 11.6471(7) A, c = 14.3225(9) A,
◦
◦
◦
3
˚
α = 70.1360(10) , β = 89.3990(10) , γ = 88.7680(10) , V = 1027.18(11) A , Z = 1.
(1) Department of Chemistry and Biochemistry, The University of
South Carolina, Columbia, South Carolina 29208.
(2) Department of Physical Sciences, Lander University, Greenwood,
South Carolina 29649.
(3) Present address: Department of Mathematics and Natural Sci-
ences, University of Saint Mary, Leavenworth, Kansas 66048.
(4) Present address: Department of Chemistry, Georgia Institute of
Technology, Atlanta, Georgia 30322.
∗ To whom correspondence should be addressed; at Graduate Sci-
ences Research Center, 631 Sumter Street, Columbia, SC 29208;
e-mail: zurloye@sc.edu.
125
ꢀ
C
1074-1542/05/0200-0125/0 2005 Springer Science+Business Media, Inc.

126
Fiscus et al.
Each copper in 5 is bound to two tolane ligands and two bidentate hfAcAc anions, resulting
in an octahedral coordination environment identical to that found in 3 and 4.
KEY WORDS: N,Nꢁ-Bipyridyl ligands; coordination polymers; Z-shaped ligand; tolane.
Introduction
were recorded on a Nicolet 5DXBO FT-IR spec-
trophotometer using KBr pellets. Thermogravi-
There has been an intense interest in the
metricanalysis(TGA)measurementswerecarried
out using a TA Instruments SDT 2960 simultane-
ous DTA-TGA. Compounds 1–3 were heated un-
der flowing helium from 30 to 1000◦C at a heating
rate of 20◦C min−1. Elemental analyses were car-
ried out by Desert Analytics Laboratory.
preparation and structural characterization of new
organic/inorganic coordination polymers. The
field is driven by the search for functional solid
materials that may be useful as new porous
frameworks,1,2 as new grid structures for chiral
separations,3−14 or as new optical materials for
sensing and LED applications,12 among other po-
tential uses. The key to achieving the synthesis of
such structures is the organic ligands that one uses
in their preparation. The most versatile ligands to
datehavebeentheN-R-Nꢁ-bipyridine-typeligands
since they readily bind to many different metals,
and the challenge has been to develop new lig-
and geometries to realize new structural motifs.
Typical synthetic strategies have included vary-
ing the position of the nitrogen donor atom in
the pyridine ring, as well as modifying the con-
necting R-group. We have been investigating the
use of diverse N-R-Nꢁ-type ligands and have em-
ployed both strategies. In this paper, we report on
the synthesis of the N-R-Nꢁ-bidentate ligand 2,2ꢁ-
bis-(4-pyridylethynyl)tolane, which is also called
the Z-ligand because of its zig-zag shape. Further-
more, we describe the utility of this ligand in as-
sembling five new organic/inorganic coordination
polymers.
Synthesis of the 2,2ꢁ-bis-(4-pyridylethynyl)
tolane ligand
A 200 mL Schlenk flask was charged with
2-bromo-iodobenzene (23.0 g, 81.5 mmol) which
was dissolved in piperidine. Pd(PPh3)2Cl2 (0.1 g,
0.1 mmol) and CuI (0.5 g, 2.5 mmol) were then
added, the flask was evacuated, and then charged
with acetylene. The flask was then placed on a
mechanical shaker overnight. The product was
extracted with hexanes and washed with am-
monium hydroxide and water. The crude prod-
uct was then filtered over silica (hexanes) and
recrystallized from ethanol resulting in 2,2ꢁ-
dibromotolane (8.4 g, 61%) as white crystals. 1H
NMR (CDCl3) = 7.63–7.61 (m, 2H), 7.60–7.59
(m, 2H), 7.29 (dt, J = 7.7, 1.4 Hz, 2H), 7.19
(dt, J = 8.2, 1.9 Hz, 2H); 13C NMR (CDCl3) =
133.6, 132.5, 129.7, 127.0, 125.5, 125.1, 92.2.
A 100 mL Schlenk flask was charged with
2,2ꢁ-dibromotolane (3.00 g, 8.9 mmol) which
was dissolved in 10 mL THF/NEt3 (50/50).
TMS acetylene (3.94 g, 40.1 mmol) was then
added to the flask, which was flushed with N2.
Pd(PPh3)2Cl2 (0.1 g, 0.1 mmol), CuI (0.1 g,
0.5 mmol) and PPh3 (0.13 g, 0.5 mmol) were
added and the reaction was stirred at 70◦C
overnight. The product was extracted with methy-
lene chloride and washed with ammonium hy-
droxide and water. Following column chromatog-
raphy (hexanes), 2,2ꢁ-bis-(trimethylsilylethynyl)
Experimental
Materials and methods
The chemicals for all syntheses were pur-
chased from commercial sources and were used
as received. 1H and 13C NMR spectra of the lig-
and were recorded in CDCl3 on a Varian Mer-
cury/VX 300 spectrometer operating at 300 MHz
(proton) or 75 MHz (carbon). Infrared spectra

Coordination polymer chain structures
127
Synthesis of HgI2[2,2ꢁ-bis-(4-
pyridylethynyl)tolane] (2)
tolane (1.63 g, 49%) was isolated as a yellowish
1
solid. H NMR (CDCl3) = 7.33–7.29 (m, 2H).
7.28–7.26 (m, 2H), 7.10–7.00 (m, 4H), 0.02 (s,
18H); 13C NMR (CDCl3) = 132.2, 131.9, 128.1,
128.0, 126.1, 125.6, 103.4, 98.7, 92.1, 0.0.
HgI2 (0.01 mmol) was dissolved in 1 mL of
ethanol and then layered on top of a 1 mL solu-
tion of the ligand (0.02 mmol) in dichloromethane
with a layer of neat ethanol separating them.
Yellow needles suitable for X-ray diffraction
were isolated in 90% yield. IR (KBr pellet,
cm−1) – [753(m), 823(m) (C C bends)], 948(w),
1006(m), 1055(w), 1093(w), [1209(m) (C H
bend)], 1417(w), [1446(w), 1475(w), 1500(w)
(C H bend)], [1602(s) (C C stretch)], [2225(w)
(C≡C stretch)], 2331(w), 2361(w), [3013(w),
3067(w) (C H stretch)]. Anal. Calcd. for 2 – C,
40.29; H, 1.93; N, 3.36%. Found: C, 38.50; H,
1.76; N, 3.08%.
A 100 mL Schlenk flask was charged with
2,2ꢁ-bis-(trimethylsilylethynyl)tolane (1.63 g,
4.4 mmol) and dissolved in 10 mL THF/NEt3
(50/50) and approximately 10 mL of a 10%
KOH/EtOH solution. 4-bromopyridine (3.42 g,
4.4 mmol) was added to the solution, and the
flask was flushed with N2 gas. Pd(PPh3)2Cl2 (0.1
g, 0.14 mmol), CuI (0.04 g, 0.21 mmol), and
PPh3 (0.1 g, 0.03 mmol) were added followed by
an N2 purge and stirring at 70◦C for 2 days. The
product was extracted with methylene chloride
and washed with NH4OH and H2O. Flash chro-
matography using CH2Cl2 as eluent and slowly
increasing the polarity with methanol (>2%)
resulted in 2,2ꢁ-bis-(4-pyridylethynyl)tolane
(1.02 g, 61%) as a grayish-white solid. 1H NMR
(CDCl3) = 8.47 (bs, 4H), 7.60–7.56 (m, 4H),
7.38–7.35 (m, 4H), 7.25 (d, J = 5.5 Hz, 4H);
13C NMR (CDCl3) = 149.6, 132.3, 132.1, 131.1,
129.0, 128.5, 126.0, 125.5, 124.5, 92.5, 92.1,
90.8. Melting point: 189–191◦C. Anal. Calcd. for
C28H16N2 C, 88.40; H, 4.24; N, 7.36. Found: C,
86.42; H, 4.85; N, 7.16.
Synthesis of Ni(acetylacetonate)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane) (3)
Ni(acetylacetonate)2 (0.005 mmol) was dis-
solved in 1 mL of methanol and then lay-
ered on top of a 1 mL solution of the lig-
and (0.01 mmol) in dichloromethane with a
layer of neat methanol separating them. Yellow
plates suitable for X-ray diffraction were iso-
lated in 61% yield. IR (KBr pellet, cm−1) –
653(m), 697(w), [763(s), 829(s) (C C bends)],
928(m), 1013(s), 1055(w), 1089(m), [1206(s)
(C H bend)], 1258(m), 1309(m), [1363(m),
1400(s), 1460(s), 1483(s), 1514(s) (acetylace-
tonate vibrations)], [1597(s) (C C stretch)],
1930(w), 1959(w), [2220(w) (C C stretch)],
[2448(w) (nickel acetylacetonate)], 2917(w),
2958(w), [3068(w) (C H stretch)]. Anal. Calcd.
for 3 – C, 71.61; H, 4.74; N, 4.40%. Found: C,
70.74; H, 4.65; N, 4.84%.
Synthesis of HgBr2[2,2ꢁ-bis-(4-
pyridylethynyl)tolane] (1)
HgBr2 (0.005 mmol) was dissolved in 1
mL of methanol and then layered on top of a
1 mL solution of the ligand (0.01 mmol) in
dichloromethane with a layer of neat methanol
separating them. Yellow plates suitable for X-
ray diffraction were isolated in 64% yield. IR
(KBr pellet, cm−1) – 697(m), [759(s), 822(s)
(C C bends)], 1007(s), 1064(m), [1214(s) (C H
bend)], 1316(w), 1421(s), [1442(m), 1475(m),
1500(m) (C H bends)], 1533(m), [1604(s) (C C
stretch)], 1920(w), [2222(m) (C C stretch)],
[3057(w) (C H stretch)]. Anal. Calcd. for 1 – C,
45.40; H, 2.18; N, 3.78%. Found: C, 45.50; H,
2.26; N, 3.79%.
Synthesis of Zn(acetylacetonate)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane) (4)
Zn(acetylacetonate)2 (0.005 mmol) was dis-
solved in 1 mL of ethanol and then layered on
top of a 1 mL solution of the ligand (0.01 mmol)

128
Fiscus et al.
in dichloromethane with a layer of neat methanol
separating them. Yellow plates suitable for X-ray
diffraction were isolated in 30% yield. Infrared
and microanalytical data were not obtained for 4
due to the low product yield.
located on two-fold rotation axes and are con-
nected to symmetry related pairs of Z-ligands and
bromine atoms, giving rise to a distorted tetra-
hedral coordination environment around the mer-
cury atom (Fig. 1). All of the mercury bond dis-
˚
tances are normal with Hg N at 2.418(3) A and
˚
Hg Br at 2.4894(4) A. The N Hg N angle is
SynthesisofCu(hexafluoroacetylacetonate)2(2,2ꢁ-
bis-(4-pyridylethynyl)tolane)·CHCl3 (5)
compressed from the ideal tetrahedral angle to
100.19(14)◦ while the bromines are pushed apart
to a 152.13(2)◦ angle.
Cu(hexafluoroacetylacetonate)2 (0.01 mmol)
was dissolved in 1 mL of methanol and then lay-
ered on top of a 1 mL solution of the ligand
(0.02 mmol) in chloroform with a layer of neat
methanol separating them. Green plates suitable
for X-ray diffraction were isolated in 74% yield.
Infrared and microanalytical data for 5 were not
obtained.
The Z-ligands in 1 rest on inversion centers,
such that the asymmetric unit contains one mer-
cury atom, one bromine atom, and half of a Z-
ligand. The overall structure consists of zig-zag
chains of the 1-D coordination polymer running
parallelto(101);andthesechainsstackinanoffset
fashion along the crystallographic b-axis (Fig. 2).
Despite the possibility for aromatic stacking in-
teractions, the closest ring–ring centroid distance
˚
is greater than 4.7 A, with the nearest, perpendic-
Single-crystal structure determinations
˚
ular interchain distance being only about 3.5 A.
The ring centroids are, however, in the vicinity
of the triple bond pi clouds of ligands in neigh-
boring chains (centroid (N1 C5) – C6 C7 mid-
Suitable single crystals of 1–5 were selected
and attached in air to thin glass fibers. Inten-
sity measurements were made using a Bruker
SMART APEX platform diffractometer (Mo Kα
˚
point=3.58A, centroid(C8 C13)–C6 C7mid-
˚
point = 3.49 A). Thermal analysis of 1 indicates
radiation, λ = 0.71073 A).15 The structures were
˚
that the coordination polymer chains are stable up
to 123◦C.
solved and refined by a combination of direct
methods and difference Fourier syntheses, using
SHELXTL.16 All non-hydrogen atoms were re-
fined with anisotropic displacement parameters.
Hydrogen atoms were placed in the calculated po-
sitions and refined using a riding model. Crystal
data, data collection parameters, and refinement
statistics for 1–5 are compiled in Table 1. Rel-
evant interatomic distances and bond angles for
1–5 are collected in Table 2.
HgI2[2,2ꢁ-bis-(4-pyridylethynyl)tolane] (2)
The one-dimensional coordination polymer
2 crystallizes from the reaction of HgI2 and the
Z-ligand upon slow diffusion of the two solutions
together. The mercury cation is connected to two
iodine atoms and two crystallographically distinct
Z-ligands (Fig. 3), both of which lie on inver-
sion centers. Both 1 and 2 possess mercury in a
highly distorted tetrahedral coordination environ-
ment (compound 2 has a compressed N Hg N
angle of 100.6(2)◦ and an expanded I Hg I angle
of 146.01(2)◦) and have normal mercury-ligand
Results and discussion
HgBr2[2,2ꢁ-bis-(4-pyridylethynyl)tolane] (1)
The one-dimensional coordination polymer
1crystallizedfromthereactionbetweenthebiden-
tate Z-ligand and HgBr2, which were slowly dif-
fused together. The mercury cations in 1 are
˚
bond lengths (average Hg N is 2.429 A and aver-
˚
age Hg I is 2.661 A in 2). Both structures consist
of zig-zag coordination polymer chains running

Coordination polymer chain structures
129

130
Fiscus et al.
Table 2. Bond Lengths and Angles for 1–5
Table 2. Continued
Angles (◦)
˚
Bond
Distance (A)
Bonds
Angles (◦)
˚
Bond
Distance (A)
Bonds
O(1) Cu O(1)#1 180.0
1
2
C(5) N(1) Cu
C(1) N(1) Cu
C(21) O(1) Cu
C(23) O(2) Cu
122.6(2)
Hg N(1) 2.418(3)
Hg Br 2.4894(4)
N(1) Hg N(1)#1
N(1) Hg Br
N(1)#1 Hg Br
Br Hg Br#1
C(1) N(1) Hg
C(5) N(1) Hg
100.19(14)
99.04(7)
98.74(7)
152.13(2)
121.7(2)
121.2(3)
120.4(2)
122.9(2)
127.7(2)
Hg N(1) 2.423(6)
Hg N(2) 2.435(6)
N(1) Hg N(2)
N(1) Hg I(2)
N(2) Hg I(2)
N(1) Hg I(1)
N(2) Hg I(1)
I(2) Hg I(1)
C(1) N(1) Hg
C(5) N(1) Hg
C(19) N(2) Hg
C(15) N(2) Hg
100.6(2)
parallel to (101), and the chains in both com-
pounds stack along the crystallographic b-axis
(Fig. 4). However there is an unexpected differ-
ence between 1 and 2, namely the trans versus cis
orientation of the Z-ligands coordinated to the Hg
center, and this difference is illustrated in Fig. 5.
In the trans orientation, the central tolane units
(Ph C C Ph) of the ligands are approximately
parallel; whereas in the cis orientation, the central
tolane groups of two ligands attached to the same
metal point directionally opposite.
100.73(18)
101.76(15)
101.22(17)
99.33(16)
146.01(2)
120.0(5)
121.0(6)
122.7(5)
119.5(5)
Hg I(1)
Hg I(2)
2.6745(7)
2.6475(7)
3
4
5
Ni N(1)
Ni O(2)
Ni O(1)
2.1515(19) O(2) Ni O(2)#1
2.0151(16) O(2) Ni O(1)
2.0258(16) O(2)#1 Ni O(1)
O(1) Ni O(1)#1
180.00(11)
90.87(6)
89.13(6)
180.00(16)
90.21(7)
No aromatic stacking interactions are present
in 2, with the closest ring-ring centroid distance
N(1)#1 Ni O(2)
O(2)#1 Ni N(1)#1 89.79(7)
O(1) Ni N(1)#1 88.75(7)
O(1)#1 Ni N(1)#1 91.25(7)
N(1)#1 Ni Ni(1)
C(5) N(1) Ni
C(1) N(1) Ni
C(15) O(1) Ni
C(17) O(2) Ni
˚
being greater than 4.4 A. In contrast to 1, no ring-
alkyne pi cloud interactions can be identified for
2. Thermal analysis indicates that the chains in 2
are stable to 187◦C.
180.00(9)
122.69(16)
120.29(16)
125.07(16)
126.11(16)
Ni(acetylacetonate)2(2,2ꢁ-bis-(4-pyridylethynyl)
tolane) (3) and Zn(acetylacetonate)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane (4)
Zn N(1)
Zn O(2)
Zn O(1)
2.2361(12) O(2) Zn O(2)#1
2.0428(10) O(2) Zn O(1)
2.0720(11) O(2)#1 Zn O(1)
O(1) Zn O(1)#1
180.00(7)
89.42(4)
90.58(4)
180.00(9)
90.48(4)
O(2) Zn N(1)#1
Compound 3 crystallized out of solution
through the slow diffusion of the reactants. Both
the Ni center and the Z-ligand rest on inversion
centers, and the asymmetric unit therefore con-
tains one Ni center, one acetylacetonate, and half
a Z-ligand (Fig. 6). This arrangement gives Ni a
distorted [4 + 2] octahedral coordination environ-
O(2)#1 Zn N(1)#1 89.52(4)
O(1) Zn N(1)#1 88.36(4)
O(1)#1 Zn N(1)#1 91.64(4)
N(1) Zn N(1)#1
C(5) N(1) Zn
C(1) N(1) Zn
C(15) O(1) Zn
C(17) O(2) Zn
180.00(6)
122.49(10)
120.10(10)
125.04(10)
126.62(10)
˚
ment with an Ni N distance of 2.1515(19) A and
Cu N(1)
Cu O(2)
Cu O(1)
2.051(2)
2.031(2)
2.242(2)
O(2) Cu O(2)#1
O(2) Cu N(1)#1
O(2)#1 Cu N(1)
N(1)#1 Cu N(1)
O(2) Cu O(1)
180.00(12)
90.13(9)
89.87(9)
180.000(1)
86.21(8)
93.79(8)
88.10(9)
91.90(9)
˚
an average Ni O distance of 2.02 A. Because the
Z-ligands are attached to the Ni center in a trans
fashion, the zig-zag character of the 1-D chains is
solely a product of the ligand geometry (Fig. 7).
The chains stack along the b-axis while simultane-
ously forming layers perpendicular to the c-axis.
O(2)#1 Cu O(1)
N(1)#1 Cu O(1)
N(1) Cu O(1)

Coordination polymer chain structures
131
Fig. 1. Thermal ellipsoid plot of the Hg coordination environment in HgBr2(2,2ꢁ-bis-
(4-pyridylethynyl)tolane) (1). Displacement ellipsoids drawn at the 50% probability
level.
Thermal analysis shows a multi-step decomposi-
tion of 3 starting at 203◦C.
is shown in Fig. 8. No significant aromatic inter-
actions are present in either 3 or 4.
Compound 4 was also characterized by sin-
gle crystal X-ray diffraction and was determined
to be isostructural to 3. Compound 4, likewise,
contains Zn2+ in a [4 + 2] octahedral coordination
environment with a Zn N distance of 2.2361(12)
Cu(hexafluoroacetylacetonate)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane)·CHCl3 (5)
˚
˚
As with 3 and 4, compound 5 crystallized
A and an average Zn O distance of 2.06 A. A
out of solution through the slow diffusion of the
thermal ellipsoid plot of the asymmetric unit of 4
Fig. 2. The crystal packing of 1 viewed along the b-axis. Z-ligands are trans oriented
about Hg2+. Hg atoms shown as black spheres; Br, green; N, blue; C, white; H atoms
not shown.

132
Fiscus et al.
Fig. 3. The asymmetric unit of HgI2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane) (2). Displacement ellipsoids are
drawn at the 30% probability level.
Fig. 5. cis and trans arrangements of two Z-ligands about an
Hg2+ center.
˚
˚
reactants. Both the Cu center and the ligand rest
on inversion centers with the asymmetric unit con-
taining one Cu center, one hfAcAc−, and half a Z-
ligand (Fig. 9). Additionally, the asymmetric unit
contains one chloroform solvate molecule, disor-
dered over two orientations.
Cu N = 2.051(2) A, and Cu O(2) = 2.031(2) A
in 5), whereas the metal–nitrogen bonds are the
longest bonds in 3 and 4. However, as in 3 and 4,
the polymer chain structure is propagated through
the trans Cu N bonds, and the zig-zag character
of the chains is a result of the ligand geometry
alone (Fig. 10). The polymeric chains stack along
the crystallographic a-axis while simultaneously
forming layers perpendicular to the b-axis. No sig-
nificant aromatic interactions were observed for 5.
The ligand arrangement about Cu is a dis-
torted [4 + 2] octahedral environment. An un-
usual characteristic of 5 is that the longest bond
˚
is a metal–oxygen bond (Cu O(1) = 2.242(2) A,
Fig. 4. Crystal packing in 2 viewed along [010] and highlighting the cis orientation
of the Z-ligands around Hg2+. Hg atoms shown as black spheres; I, green; N, blue; C,
white; H atoms not shown.

Coordination polymer chain structures
133
Fig. 8. Displacement ellipsoids drawn at the 50% probability
level for Zn(AcAc)2(2,2ꢁ-bis-(4-pyridylethynyl)tolane (4).
Fig. 6. Ellipsoid plot of Ni(AcAc)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane) (3). Displacement ellipsoids are
shown at the 50% probability level.
Conclusion
We have synthesized the new N-R-Nꢁ-
bidentate ligand, 2,2ꢁ-bis-(4-pyridylethynyl)
tolane, which has a Z-shape. We have suc-
cessfully used this ligand in the preparation of
five new coordination polymers that consist of
zig-zag 1-D chains. The zig-zag 1-D chains
form as a direct consequence of the ligand
coordination environment around the metal
center in combination with the inherent shape of
the Z-ligand. While the highly conjugated nature
of the ligand suggests the possibility of aromatic
interactions in the compounds, none of the five
display significant pi–pi interactions.
Fig. 9. The copper coordination environment (40%
probability ellipsoids) in Cu(hfAcAc)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane (5). Inversion centers are located
at the Cu center and the C14–C14A midpoint.
Fig. 7. Crystal packing of Ni(AcAc)2(2,2ꢁ-bis-(4-
pyridylethynyl)tolane) (3) viewed along [010]. Ni atoms are
shown as black spheres; O, red; N, blue; C, white; H atoms
omitted.
Fig. 10. Packing of 5 viewed along the crystallographic a-
axis. Chloroform solvate molecules have been omitted for
clarity. Cu atoms are shown as black spheres; F, green; O,
red; N, blue; C, white; H atoms omitted.

134
Fiscus et al.
6. Carlucci, L.; Ciani, G.; Macchi, P.; Proserpio, D.M. Chem. Com-
mun. 1998, 1837.
Acknowledgments
7. Carlucci, L.; Ciani, G.; Proserpio, D.M.; Rizzato, S. Chem.
Commun. 2000, 1319.
8. Chen, Z.-F.; Xiong, R.-G.; Zhang, J.; Zuo, J.-L.; You, X.-Z.;
Che, C.-M.; Fun, H.-K. J. Chem. Soc., Dalton Trans. 2000,
4010.
Financial support was provided by the
National Science Foundation through Grant Num-
bers CHE:0314164 and DMR:0138948. REH ac-
knowledges Brin/EPSCoR for funding through
grant number 1P20RR16461.
9. Ezuhara, T.; Endo, K.; Aoyama, Y. J. Am. Chem. Soc. 1999,
121, 3279.
10. Fragoso, A.; Kahn, M.L.; Casineiras, A.; Sutter, J.-P.; Kahn, O.;
Cao, R. Chem. Commun. 2000, 1547.
11. Mamula, O.; von Zelewsky, A.; Bark, T.; Bernardinelli, G.
Angew. Chem. Int. Ed. 1999, 38, 2945.
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