Synthesis, crystal structures, magnetic properties and Suzuki and Heck coupling catalytic activities of new coordination polymers containing tetracyanopalladate(II) anions

Article abstract of DOI:10.1016/j.poly.2012.09.030

Four novel coordination polymers, [Ni(bishydeten)Pd(CN)₄] (1), [Cu(bishydeten)Pd(CN)₄] (2), [Zn(bishydeten)Pd(CN)₄] (3) and [Cd(bishydeten)Pd(CN)₄] (4) (bishydeten = N,N′-bis(2- hydroxyethyl)ethylenediamine], have been synthesized and characterized by various techniques (elemental analysis, IR, EPR, X-ray and thermal analysis). In compound 4, all of the cyano groups use -N edges to form coordination bonds to Cd(II) in addition to -C atoms, resulting in the formation of a tridimensional network. The same situation is observed for compound 3 for one of the tetracyanopalladate(II) groups, while two cyano groups remain in the monodentate form coordinated to Pd(II) in the other tetracyanopalladate(II) group. While an EPR signal was not observed for 1, the g parameters obtained from the EPR spectrum of 2 indicated that the Cu(II) ions are located in tetragonal distorted octahedral sites (D_4h) and that the ground state of the paramagnetic electron is d^x2-y2. Variable temperature magnetic susceptibility measurements recorded in the range 15-300 K showed the presence of a very small antiferromagnetic interaction below 20 K for complexes 1 and 2. 2 was proven to be less effective as a catalyst than 1 under the Heck reaction conditions. Moreover, 1 was determined to be a more effective catalyst and more efficient for iodoarenes than bromoarenes under Suzuki coupling conditions.

Full text of DOI:10.1016/j.poly.2012.09.030

Polyhedron 49 (2013) 50–60
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, crystal structures, magnetic properties and Suzuki and Heck
coupling catalytic activities of new coordination polymers containing
tetracyanopalladate(II) anions
Ayßsegül Sßenocak a, Ahmet Karadag˘ a, , Yusuf Yerli b,1, Nevin Gürbüz c,2, Ismail Özdemir c,2, Ertan Sßahin d,3
⇑
_
a Department of Chemistry, Art and Science Faculty, Gaziosmanpaßsa University, 60400 Tokat, Turkey
b Department of Physics, Gebze Institute of Technology, 41400 Kocaeli, Turkey
c
_
Department of Chemistry, Art and Science Faculty, Inönü University, 44280 Malatya, Turkey
d Department of Chemistry, Science Faculty, Atatürk University, 25240 Erzurum, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 June 2012
Accepted 11 September 2012
Available online 26 September 2012
Four novel coordination polymers, [Ni(bishydeten)Pd(CN)4] (1), [Cu(bishydeten)Pd(CN)4] (2), [Zn(bishyde-
ten)Pd(CN)4] (3) and [Cd(bishydeten)Pd(CN)4] (4) (bishydeten = N,N0-bis(2-hydroxyethyl)ethylenedia-
mine], have been synthesized and characterized by various techniques (elemental analysis, IR, EPR,
X-ray and thermal analysis). In compound 4, all of the cyano groups use –N edges to form coordination
bonds to Cd(II) in addition to –C atoms, resulting in the formation of a tridimensional network. The same
situation is observed for compound 3 for one of the tetracyanopalladate(II) groups, while two cyano
groups remain in the monodentate form coordinated to Pd(II) in the other tetracyanopalladate(II) group.
While an EPR signal was not observed for 1, the g parameters obtained from the EPR spectrum of 2 indi-
cated that the Cu(II) ions are located in tetragonal distorted octahedral sites (D4h) and that the ground
Keywords:
Coordination polymers
Palladium complexes
Crystal structures
Thermal analysis
Magnetic susceptibility
Catalyst
state of the paramagnetic electron is dx
. Variable temperature magnetic susceptibility measurements
2ꢀy2
recorded in the range 15–300 K showed the presence of a very small antiferromagnetic interaction below
20 K for complexes 1 and 2. 2 was proven to be less effective as a catalyst than 1 under the Heck reaction
conditions. Moreover, 1 was determined to be a more effective catalyst and more efficient for iodoarenes
than bromoarenes under Suzuki coupling conditions.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
when paramagnetic sites are bridged by tetracyanometallate(II)
and especially tetracyanonickelate(II), suitable model compounds
Cyano-bridged polymeric complexes have attracted consider-
able attention due to their various desirable properties, depending
upon the metal center and ancillary ligand used. While palladium
centered polymeric complexes have been evaluated in the area of
catalysis, polymeric complexes containing a paramagnetic center
may be used as molecular magnets. For example, Pd-catalyzed ary-
lation and vinylation have proven to be among the most powerful
means for the formation of carbon–carbon bonds in organic syn-
thesis [1–13]. Thus, Pd complexes exhibiting catalytic properties
are employed in Suzuki and Heck coupling reactions. Moreover,
for magnetic studies at low temperatures have been obtained
[14–20]. In addition, it has been known that porous cyano-bridged
complexes may be used in the areas of host–guest chemistry and
catalysis [21–30].
The Heck reaction has been shown to be very useful for the
preparation of disubstituted olefins [6]. The rate of coupling de-
pends on a variety of parameters, such as temperature, solvent,
base and catalyst loading. Heck reactions are generally conducted
with a tertiary phosphine [8] or NHC [31] palladium complex
and require high temperatures (>120 °C) and polar solvents, but
the reaction can be carried out at lower temperatures using an ade-
quate Pd catalysts. Also, the Suzuki cross-coupling reaction repre-
sents a powerful method for C–C bond formation [10]. Recently,
the Suzuki coupling of aryl chlorides catalyzed by Pd/tertiary phos-
phine [8] and Pd/NHC [32] systems has been extensively studied
due to the economically attractive nature of the starting materials.
Therefore, it was thought that the polymeric cyano bridged Pd(II)
complexes synthesized in this study could be useful catalysts in
Suzuki and Heck coupling reactions.
⇑
Corresponding author. Tel.: +90 356 2521616; fax: +90 356 2521585.
E-mail addresses: asenocak@purdue.edu, ayseon@gmail.com (A. Sßenocak),
ahmet.karadag@gop.edu.tr, akaradag68@gmail.com (A. Karadag˘), yyerli@gyte.
edu.tr (Y. Yerli), ngurbuz@inonu.edu.tr (N. Gürbüz), iozdemir@inonu.edu.tr (I.
_
Özdemir), ertan@atauni.edu.tr (E. Sßahin).
1
Tel.: +90 262 6051000; fax: +90 262 6538490.
Tel.: +90 422 3773680; fax: +90 422 3410037.
Tel.: +90 442 2314380.
2
3
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.09.030

A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
51
Table 1
Crystal data and structure refinement for 3 and 4.
3
4
Empirical formula
Crystal color
Fw
C
10H16N6O2PdZn
C10H16CdN6O2Pd
Colorless
471.10
Colorless
424.08
Crystal system
Space group
Triclinic
P1
Monoclinic
C2/c
ꢀ
Crystal size (mm3)
Z
0.72 ꢂ 0.43 ꢂ 0.16
2
0.12 ꢂ 0.14 ꢂ 0.18
4
a (Å)
b (Å)
c (Å)
7.3298(4)
7.8650(4)
13.6882(11)
82.90(2)
86.94(2)
80.16(2)
771.12(9)
1.826
9.9565(4)
11.0302(3)
14.8226(6)
90
109.10(2)
90
1538.27(1)
2.034
2.561
a
(°)
b (°)
c
(°)
V (Å3)
qcalcd (g cmꢀ3
l
)
(mmꢀ1
)
2.73
F(000)
h range (°)
Limiting indices
420
912
Fig. 2. ORTEP drawing of 4 in the asymmetric unit, showing the atom labelling
scheme. Thermal ellipsoids are drawn at the 40% probability level.
2.7 6 h 6 26.5
ꢀ8 6 h 6 9
ꢀ9 6 k 6 9
ꢀ17 6 l 6 17
16107
2.8 6 h 6 40.3
ꢀ17 6 h 6 18
ꢀ20 6 k 6 16
ꢀ26 6 l 6 26
30746
Measured reflections
some of the first examples studied as catalysts in Suzuki and Heck
Coupling reactions by our group [37].
Independent reflections
2947
1.237
4781
1.275
Goodness-of-fit (GOF) on F2
R1, wR2 [I > 2
r
I]
0.047, 0.210
0.029, 0.103
2. Materials and methods
PdCl2, NiCl2ꢁ6H2O, CuCl2ꢁ2H2O, ZnCl2, CdSO4ꢁ8/3H2O, KCN and
bishydeten [N,N0-bis(2-hydroxyethyl)ethylenediamine, (C6H16N2
O2)] were purchased and used without further purification.
Elemental analyses (C, H and N) were carried out by standard
_
methods using a CHNS-932 (LECO) Elemental Analyzer (TÜBITAK
Ankara Test and Analysis Laboratory, Turkey and ODTÜ Central
Laboratory, Turkey). The IR spectra were recorded on a Jasco 430
FT-IR spectrophotometer using KBr pellets in the 4000–400 cmꢀ1
range (Gaziosmanpaßsa University, Turkey). The thermogravimetric
analysis (TG), differential thermal analysis (DTA), and derivative
thermogravimetric analysis (DTG) measurements were carried
out using a Perkin–Elmer Diamond TG/DTA Thermal Analysis
instrument under a nitrogen atmosphere with a heating rate of
10 °C minꢀ1 and sample weights of approximately 10 mg. In addi-
tion, the enthalpy values of each stage were calculated by convert-
ing the DTA signals to DSC signals (Gaziosmanpaßsa University,
Turkey). The 15–300 K magnetization measurements were carried
out on a Quantum Design PPMS system.
v–T plots were recorded
under a constant magnetic field of 0.5 kOe. The magnetic data were
corrected for the diamagnetic contribution of the sample holder.
The EPR powder spectrum was recorded using a Bruker EMX
X-band spectrometer (9.8 GHz) with an approximate microwave
power of 20 mW and 100 kHz magnetic field modulation (Gebze
Institute of Technology, Turkey). All reactions were monitored on
an Agilent 6890 N GC system by GC–FID with a HP-5 column
Fig. 1. ORTEP drawing of 3 in the asymmetric unit, showing the atom labelling
scheme. Thermal ellipsoids are drawn at the 40% probability level (symmetry code
(i): 1 ꢀ x, ꢀy, 1 ꢀ z).
In previous studies, we reported the properties and structures
of cyano bridged complexes containing the hydeten [N-(2-hydroxy-
ethyl-ethylenediamine)] ligand [33–36]. The hydeten ancillary li-
gand acts as a bidentate ligand in the structures of all six
complexes determined by X-ray single crystal analysis. The 1D
chain structures of these complexes extend to 3D networks by
hydrogen bonds forming among the cyano groups and hydeten li-
gands. Herein, we have synthesized four novel cyano-bridged com-
plexes with different stoichiometries by replacing hydeten with
bishydeten. The X-ray structures of 3 and 4 were determined. The
spectroscopic (IR and EPR) and thermal properties of the four com-
plexes were also investigated. Additionally, the catalytic and mag-
netic properties of 1 and 2, having Ni(II) and Cu(II) ions as the
central metal, were studied. In addition to interesting crystal struc-
tures, a remarkable aspect of the study is to report on the catalytic
activities of the cyano bridged polymeric complexes, which are
length of 30 cm, 0.32 mm diameter and 0.25 lm film thickness
for catalysis studies. Column chromatography was performed
using silica gel 60 (70–230 mesh). The solvent ratios are given as
_
v/v (Inönü University, Turkey).
2.1. Synthesis of the complexes
2.1.1. Complex 1
Complex 1 was prepared by the self-assembly method. Solid
NiCl2ꢁ6H2O (0.85 mmol, 0.201 g) was added to a freshly prepared
K2[Pd(CN)4]ꢁ3H2O solution (15 mL water: 5 mL ethanol) by mixing
PdCl2 (0.85 mmol, 0.150 g) with KCN (3.38 mmol, 0.220 g). To the
resulting pale blue slurry, an ethanolic solution containing
bishydeten (0.85 mmol, 0.125 g) was added dropwise and then

52
A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
Table 2
Selected bond lengths and bond angles for the complexes.
3
4
Bond lengths (Å)
Pd1–C1
Pd1–C2
Pd2–C3
Pd2–C4
C4–N6
C7–N4
C1–N1
2.002(5)
1.990(5)
1.994(4)
1.989(7)
1.155(4)
1.467(3)
1.138(3)
N4–Zn
N5–Zn
N6–Zn
N1–Zn
N2–Zn
O1–Zn
2.138(5)
2.200(5)
2.117(4)
2.206(4)
2.090(3)
2.194(4)
Pd–C1
Pd–C3
C1–N1
C3–N3
1.985(2)
1.996(2)
1.149(3)
1.145(3)
Cd–N1
Cd–N2
Cd–N3
2.315(2)
2.361(2)
2.371(2)
Bond angles (o)
C1–Pd1–C1
C1–Pd1–C2
C1–Pd1–C2
C3–Pd2–C3
C3–Pd2–C4
C3–Pd2–C9
N4–Zn–N5
C8–N4–Zn
180.0
91.1(3)
88.9(3)
180.0
N1–Zn–N4
O1–Zn–N4
O1–Zn–N1
N1–Zn–N4
N5–Zn–N1
N5–Zn–N6
N4–Zn–N4
Zn–N1–C1
N1–C1–Pd1
89.02(7)
76.66(7)
86.58(6)
89.02(7)
89.02(6)
93.40(7)
91.59(7)
162.63(7)
176.76(5)
N3–C3–Pd
N1–C1–Pd
C1–Pd–C1
C3–Pd–C3
C1–Pd–C3
C1–Pd–C3
N1–Cd–N1
N1–Cd–N2
177.6(2)
178.7(2)
180.0
180.00(11)
90.42(9)
89.58(9)
89.93(13)
95.90(9)
N1–Cd–N2
N2–Cd–N2
N1–Cd–N3
N1–Cd–N3
N2–Cd–N3
N2–Cd–N3
N3–Cd–N3
C3–N3–Cd
174.00(8)
78.30(12)
86.99(8)
97.71(9)
84.00(9)
90.86(8)
173.38(11)
156.0(2)
87.6(3)
87.34(8)
178.33(7)
166.91(17)
162.52(16)
C10–N5–Zn
the reaction mixture was stirred for a while. This blue slurry was
then filtered. The product was washed with alcohol and dried in
air. Yield: 67%. Anal. Calc. for 1: C, 28.78; H, 3.86; N, 20.13. Found:
C, 29.37; H, 4.11; N, 20.37%. IR (KBr disk; cmꢀ1): 3593, 3178
2.2.2. General procedure for the Suzuki coupling reaction
Complex 1 or 2 (1.0 mmol%), aryl bromide (1.0 mmol), phenyl-
boronic acid (1.5 mmol), Cs2CO3 (2 mmol) and DMF (3 mL) were
added to a small Schlenk tube, and the mixture was heated at
80 °C for 6 h. At the conclusion of the reaction, the mixture was
cooled, extracted with ethyl acetate/hexane (1:5), filtered through
a pad of silica gel with copious washings, concentrated, and puri-
fied by flash chromatography using silica gel. The purity of the
compounds was confirmed by NMR and GC, and yields were based
on aryl halide.
[m
(O–H)]; 3282, 3261 [
m (N–H)]; 2976, 2931, 2881 [m (C–H)];
2170, 2148 [ (C„N)].
m
2.1.2. Complex 2
Complex 2 was synthesized according to the procedure adopted
for 1, using CuCl2ꢁ2H2O (0.85 mmol, 0.144 g) rather than NiCl2ꢁ6H2-
O. The dark blue crystalline product, obtained by crystallization at
room temperature, was washed with alcohol and dried in air.
Yield: 53%. Anal. Calc. for 2: C, 28.45; H, 3.82; N, 19.90. Found: C,
2.3. X-ray analysis
28.61; H, 3.09; N, 19.85%. IR (KBr disk; cmꢀ1): 3476 [
3220 [ (N–H)]; 2977, 2916, 2873 [ (C–H)]; 2186, 2143 [
m
m
(O–H)];
(C„N)].
For the crystal structure determinations, single crystals of 3 and
4 were used for data collection using a four-circle Rigaku R-AXIS
RAPID-S diffractometer equipped with a two-dimensional area IP
detector at room temperature. Graphite-monochromatized Mo
m
m
2.1.3. Complex 3
Complex 3 was synthesized according to the procedure adopted
for 1, using ZnCl2 (0.85 mmol, 0.115 g) rather than NiCl2ꢁ6H2O.
Shiny, colorless single crystals suitable for X-ray analysis were ob-
tained by crystallization at room temperature. Yield: 41%. Anal.
Calc. for 3: C, 28.32; H, 3.80; N, 19.82. Found: C, 28.62; H, 3.88;
Ka
radiation (k = 0.71073 Å) and oscillation scan techniques
(Dx = 5° for one image) were used for the data collection. The
lattice parameters were determined by the least-squares method
on the basis of all reflections with F2 > 2 (F2). The intensity integra-
r
tions, correction for Lorentz and polarization effects, and cell
refinement were performed using CRYSTAL-CLEAR software [38]. The
structures were solved by a direct method, SHELXS-97 [39] and the
non-H atoms were refined using a full-matrix least-squares meth-
od with anisotropic temperature factors, SHELXL-97 [39]. The details
of the final refinements are given in Table 1.
N, 19.88%. IR (KBr disk; cmꢀ1): 3600, 3184 [
(N–H)]; 2988, 2964, 2927, 2885 [ (C–H)]; 2170, 2148 [m
m
(O–H)]; 3280, 3265
(C„N)].
[m
m
2.1.4. Complex 4
Complex 4 was synthesized according to the procedure adopted
for 1, using CdSO4ꢁ8/3H2O (0.85 mmol, 0.217 g) rather than NiCl2-
ꢁ6H2O. Shiny, colorless single crystals suitable for X-ray analysis
were obtained by crystallization at room temperature. Yield: 48%.
Anal. Calc. for 4: C, 25.49; H, 3.42; N, 17.84. Found: C, 25.86; H,
3. Results
3.33; N, 17.79%. IR (KBr disk; cmꢀ1): 3589 [
(N–H)]; 2960, 2939, 2916, 2885, 2868 [ (C–H)]; 2160 [m
m
(O–H)]; 3292
(C„N)].
3.1. X-ray single crystal analysis
[m
m
Catena-poly-[[di-
l
-cyano-1:200j2C:N-
l
-cyano-1:2j2C:N-[N,N0-
-cyano-10:2 2C:
2.2. Catalysis studies
bis(2-hydroxyethyl)ethylenediamine-2j3N,N0,O]-
l
j
N-dicyano-10j2C- -cyano-10:20j2C:N-[N,N0-bis(2-hydroxyethyl)
l
2.2.1. General procedure for the Heck coupling reaction
ethylenediamine-20j3N,N0,O]zincIIpalladiumII]-
l
-cyano-1:20j2C:N]
ꢀ
Complex 1 (1.0 mmol%), aryl halogenide (1.0 mmol), styrene
(1.5 mmol), Cs2CO3 (2 mmol) and DMF (3 mL) were added to a
small Schlenk tube, and the mixture was heated at 80 °C for 6 h.
At the conclusion of the reaction, the mixture was cooled,
extracted with ethyl acetate/hexane (1:5), filtered through a pad
of silica gel with copious washings, concentrated, and purified by
flash chromatography using silica gel. The purity of the compounds
was confirmed by NMR and GC; yields were based on aryl halide.
(3) crystallized in the triclinic space group P1 and Fig. 1 shows the
asymmetric unit and the labelling scheme. In this complex, the tet-
racyanopalladate(II) ions act as bridging ligands between the Zn(II)
ions, which are present in the coordination sphere of the tridentate
bishydeten ligands (N, N0, and O edges) and the bridging cyano
groups through –N atoms (Fig. 1). The chain structure of the com-
plex can be classified as the TT-type, according to the relative posi-
tion of the bridgig cyano groups of tetracyanopalladate(II) with

A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
53
Fig. 3. (a) 1D, (b) and (c) 2D perspective views of 4.
two terminal cyano ligands. In this chain structure, the Pd atoms
are collinear at a distance of 10.370 Å (Pd. . .Pd. . .Pd angle = 180°).
Both complexes have tetracyanopalladate(II) units, formed by
coordination of CN groups to Pd(II) ions in a square planar arrange-
ment. There are two crystallographically different tetracyanopalla-
date(II) groups in complex 3. While all the cyano groups act as
bridging ligands in one of these units, two of them remain as termi-
nal ligands in the other. In spite of this crystallographic difference,
the Pd–C bond distances in 3 are almost of the same value due to
the hydrogen bonds between terminal cyano ligands and the OH
groups of the bishydeten ligands on the adjacent chains. The mean
Pd–C bond lengths (1.994 for 3 and 1.991 Å for 4) in these struc-
tures (Table 2) is within the range usually found in cyano-bridged
palladates(II) [17,35,36,40–42]. The C–Pd–C bond angles, which
are equal to 180°, indicate that the complexes retain their original
square planar geometry. The Pd–C–N bonds are almost linear, with
angles in the 175.9–178.7° range. However, the C–N–Zn and
C–N–Cd angles are bent, in keeping with the literature data [43].
The X-ray diffraction analysis of catena-poly-[[di-
0j2C:N- -cyano-1:2j2C:N-[N,N0-bis(2-hydroxyethyl)ethylenedi-
amine-2j2N,N0]cadmiumIIpalladiumII]- 2C:N] (compound
-cyano-1:2
l-cyano-1:
2
l
l
j
4) disclosed Cd(II) units linked by tetracyanopalladate(II) anions
to form a 3D neutral network with the general formula of
[Cd(bishydeten)Pd(CN)4]n. While the Cd(II) ions adopt an octahe-
dral geometry in this complex, crystallized in the monoclinic
system, the Pd(II) ion is coordinated with four cyano carbons, all
of which serve as bridges by bonding to theCd(II) ions, in a square
planar geometry (Fig. 2). The volume of 4 is twice that of 3. This
dissimilarity may be attributed to difference between the radius
as well as to a more firmly-closed crystal packing for 3. Neverthe-
less, the Pd. . .Pd distance in compound 4 (10.285 Å) is shorter than
the Pd. . .Pd distance in compound 3 (10.370 Å).

54
A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
Fig. 4. Hydrogen bonds’ geometry along the b-axis for 3.
position. However, for complex 4, a significant bending (173.38°)
Table 3
is observed for the axial N(3)–Cd–N(3) angle. In addition, the
tension arising from the methylene groups of bishydeten likely
causes the widening of the N(2)–Cd–N(1) angle and narrowing of
the N(2)–Cd–N(2) angle in comparison with the ideal 90° angle
(Table 2).
In 3, as shown in Fig. 4, there are various hydrogen bonding
interactions between the donor atoms of bishydeten and the nitro-
gen atom of the cyano ligand and non-coordinate oxygen atom of
bishydeten (Table 3). As for complex 4, three possible hydrogen
bonds are displayed: O(1)–H(1). . .N(1), 3.174(5) Å; N(2)–
H(2). . .O(1), 2.913(5) Å; N(2)–H(2). . .O(1)i, 3.063(4) Å [symmetry
code: (i) –x, 1 ꢀ y, ꢀz] (Table 3). These weak hydrogen bonds sta-
bilized the structure by bonding adjacent chains (Figs. 5 and 6).
Hydrogen bonds (Å, o).
D–H. . .A
d(D–H)
d(H. . .A)
d(D. . .A)
<(DHA)
3
O1–H1. . .N3i
N4–H4. . .N3ii
N5–H5. . .O2
N5–H5. . .O2iii
O2–H2. . .N5
0.93
0.91
0.91
0.91
0.82
2.25
2.58
2.56
2.35
2.54
2.762(4)
3.332(3)
2.855(4)
3.167(5)
2.855(5)
114
139
100
150
104
4
O1–H1. . .N1
N2–H2. . .O1
N2–H2. . .O1i
0.82
0.90
0.90
2.58
2.58
2.27
3.174(5)
2.913(5)
3.063(4)
130
103
147
Symmetry codes: (i) ꢀx, 1 ꢀ y, 1 ꢀ z; (ii) ꢀx, 1 ꢀ y, ꢀz; (iii) x, 1 + y, z for 3; (iv) ꢀx,
1 ꢀ y, ꢀz for 4.
3.2. FT-IR spectra
Bishydeten, acting as a tridentate ligand, constitutes the equato-
rial plane with a bridged cyano ligand, while the remaining axial
coordination sites of the Zn(II) ion in an octahedral geometry are
occupied by two cyano nitrogens in complex 3. Bishydeten serves
as a bidentate ligand in complex 4, distinct from 3. The octahedral
Cd(II) coordination environment is composed of two nitrogen
atoms from bishydeten and two cyano nitrogens in the equatorial
plane, and other two cyano nitrogens located at the axial sites
(Fig. 3). Zn–N and Cd–N bond lengths are observed in this type of
cyano-bridged complexes [35,40,44–47]. The bond lengths in the
coordination environment of the Zn(II) follow the order of:
N(1) > N(5) > O(1) > N(4) > N(6) > N(2). The steric hindrance arising
from the non-coordinated ethanolic edge of bishydeten probably
causes Zn–N(1) and Zn–N(5) to be the longest bonds in the coordi-
nation environment of Zn(II) ion. As for complex 4, the Cd–N(3)
and Cd–N(2) bond distances are longer than Cd–N(1), probably be-
cause the ethanolic edges of bishydeten, which are not participating
in coordination, give rise to steric hindrance.
The IR spectra of all four complexes have stretching and
bending vibration peaks indicating the existence of cyano and
bishydeten ligands. The strong absorption bands resulting from
the stretching vibration of the cyano groups
m (CN) are very
characteristic and may serve to identify the cyano complexes.
The cyanide stretching vibration of KCN is observed at
2080 cmꢀ1, and this peak is shifted to 2143 cmꢀ1 in the tetracyano-
palladate(II) ion because of the CN coordination to the Pd(II) ion
[48]. The splitting of the
m (CN) stretching band is observed as a
result of the existence of bridged and terminal cyano groups in
the structure at the same time. A single cyano stretching peak
was observed at 2160 cmꢀ1 for 4 because all of the cyano groups
act as bridging ligands. On the other hand, two separate
m (CN)
peaks, belonging to bridging and terminal cyano ligands, were
found in the spectra of 1, 2 and 3. Coordinated and non-coordi-
nated OH groups were also found in 1 and 3, while one stretching
band corresponding to non-coordinated OH groups was observed
in the IR spectrum of 4. When it comes to the N–H stretching vibra-
tion, peak splitting was observed in 1 and 3 due to the different
coordination environments of the NH groups. However, a single
N–H stretching peak appeared in 2 and 4 since the NH groups
presented the same environment. The remaining stretching and
The in plane N–Zn–N and N–Zn–O angles deviate from 90° due
to the tension resulting from methylene chains of bishydeten and
steric hindrance from the non-coordinated ethanolic edge of
bishydeten. In contrast to the situation in the equatorial plane,
the ideal linear angle is approximately conserved at the axial

A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
55
Fig. 5. (a) 1D, (b) 2D and (c) 3D perspective views of 3.
bending vibration peaks appeared in similar positions for all the
3.4. EPR spectra
complexes.
The Pd(II) ions in both 1 and 2 exhibit a square planar coordina-
tion, adopting low spin (S = 0) and as a result of this, all spins of the
d8 ion are paired. For this reason, an EPR signal for the Pd(II) ion
was not observed. Because of very short relaxation times of the
Ni(II) ion in complex 1 at room temperature, the Ni(II) ion did
not exhibit an EPR signal.
Fig. 9 shows the powder EPR spectrum for 2. Two parallel and
perpendicular components were observed in this spectrum. Hyper-
fine splitting could not be observed due to the line broadening that
originated from spin-exchange and spin–orbital interactions. The
values of the g// and g\ components, extracted from the powder
spectrum, are 2.259 and 2.075, respectively. The g parameters
indicate that the paramagnetic center is axially symmetric. From
the order g// > g\ > ge (free electron g value, ge = 2.0023), it can be
concluded that the Cu(II) ions are located in tetragonal distorted
octahedral sites (D4h) elongated along the z-axis and that the
ground state of the paramagnetic electron is (2B1g state) [49–51].
3.3. Thermal analysis
TG and DTG curves of 1, 2, 3 and 4, studied under identical
experimental conditions, are depicted in Figs. 7 and 8, respectively.
All the complexes followed an identical decomposition mecha-
nism: release of a neutral bishydeten ligand followed by the loss
of the cyano groups. The thermal decomposition products were
metal mixtures. However, the Pd metal solely remained in 4 due
to the relatively low boiling point of Cd metal. Although Zn has rel-
atively low boiling point too, not all of the Zn was liberated from 3
due to temperature limitation (1350 °C) of the thermal analysis
equipment.
Significant thermoanalytical data belonging to the four com-
plexes are summarized in Table 4.

56
A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
Fig. 6. Hydrogen bonding geometry (a) and (b) packing diagram for 4.
The Pt analogue of this complex (g// = 2.257 and g\ = 2.075) [40]
and the [Cu(hydeten)2Pd(CN)4] complex (g// = 2.256 and g\
2.075) [36] exhibited similar EPR spectra with very close g compo-
nents. In contrast, lower g components (g// = 2.237 and g\ = 2.059)
were observed in the [Cu(hydeten)2Pt(CN)4] complex [33].
perature dependence of vm was fitted by the relationship
(T ꢀ h) where C is the Curie constant, h is the Weiss constant and
is temperature independent susceptibility (TIP) [52]. The posi-
tively sloped dependency in Fig. 10 (inset) has shown a presence
of TIP in this structure. TIP can originate from a couple of reasons:
coupling of the ground state with excited states [existence of itin-
erant (conducting) electrons] and the effect of the orbital moments
of d electrons. The fitting results were determined and listed as
a + C/
=
a
3.5. Magnetic susceptibility studies
followed:
emuK/mol.Oe; and h = ꢀ2.71 0.005 K. The effective magnetic
moment, eff, was calculated to be 3.1, using the
eff = 2.83(C)1/2
a = 0.00107 0.0000017emu/mol.Oe; C = 1.20 0.00032
The magnetic susceptibility of 1 was obtained in the tempera-
ture range 15–300 K. The temperature dependences of the molar
magnetic susceptibility vm and vmT are shown in Fig. 10. The tem-
l
l

A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
57
Fig. 7. TG curves of 1–4.
Fig. 8. DTG curves of 1–4.
relationship, in Bohr magnetons (
l
B). While a lower leff value
C = 0.433 0.00003 emuK/mol.Oe, and h = ꢀ0.77 0.003 K. The leff
value was found to be 1.86 B using the relationship
eff = 2.83(C)1/
close value of 1.87 was obtained for the [Cu(bishyde-
ten)Pt(CN)4] complex [40]. Similarly, a very close value (1.85)
was observed for the hydeten analogue of this complex [37]. The
mixing of some spin–orbital angular momentum from the excited
(3.04) was observed for the [Ni(bishydeten)Ni(CN)4] complex, a
higher leff value (3.57) was obtained for the [Ni(bishyde-
ten)Pt(CN)4] complex [40]. For the hydeten analogue of 3, a lower
leff value (3.03) was obtained [37]. The value of leff at room tem-
perature for 1 appeared to be significantly above that of the two
spin values due to the mixing of some spin–orbital angular
momentum from excited states via spin–orbit coupling [53].
The magnetic susceptibility of 2 was obtained in the tempera-
ture range 15–300 K. The temperature dependences of the molar
magnetic susceptibility vm and 1/vm are shown for this complex
in Fig. 11. It was observed that the variable temperature depen-
dence of vm obeyed the relationship of C/(T ꢀ h) where C is the
Curie constant and h is the Weiss constant [52]. From this fitting
l
l
2
.
A
states via spin–orbit coupling resulted in increasing leff in compar-
ison with the spin only value at room temperature for 2 [53].
There might be very little antiferromagnetic interactions in
both 1 and 2, as shown in Figs. 10 and 11 (insets) respectively.
For both complexes,
vmT (C) is not affected by decreasing the
temperature until around 20 K, but below this temperature, its
value begins to decrease. This magnetic interaction might be be-
tween and within the chains through CN bridges and hydrogen
bonds.
process,
the
following
components
were
determined

58
A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
Table 4
Thermoanalytical data of the complexes with the general formula [M(bishydeten)Pd(CN)4].
Complex
Temperature range (°C)
DTGmax. (°C)
D
H (J/g)
Mass loss,
Found
D
m (%)
Residue (%)
Found
Calc.
Calc.
1
226–353
353–375
375–465
465–566
566–659
659–969
346
365
385
507
619
885
451.96
830.26
441.41
125.62
232.84
5128.36
13.12
15.72
18.53
3.01
3.11
6.29
47.98
86.88
71.16
52.63
49.62
46.51
40.22
52.02
6.23
6.23
45.79
39.56
Ni + Pd
2
3
155–221
221–512
512–887
887–1181
203
309
757
ꢀ2109.02
11044.67
4087.56
2674.79
2.58
45.32
7.12
47.43
12.32
97.42
52.10
44.98
40.35
52.57
40.25
Cu + Pd
1081
4.63
205–279
279–507
507–952
952–1344
256
286
607
3924.39
673.92
77779.25
14.09
19.24
23.89
11.52
34.95
85.91
66.67
42.78
31.26
65.05
24.54
15.42
40.51
25.09
1253
0.25Zn + Pd
4
233–569
569–890
890–1185
281
811
931
467.35
460.50
690.79
37.53
16.53
22.92
36.98
16.57
23.86
32.47
45.94
23.02
63.02
46.45
22.59
Pd
Fig. 9. The powder EPR spectrum of 2 at room temperature.
Fig. 11. The temperature dependence of the molar magnetic susceptibility
vm for 2.
Solid line represents fit with the Curie–Weiss law. Inset: The temperature
a
dependence of
vmT.
Table 5
Yields of the Heck reaction of aryl halides with styrene.
Entry
R
Cat.
Yielda (%)
1
2
3
4
5
6
7
8
9
COCH3
COCH3
COCH3
COCH3
CHO
CH3
H
H
OCH3
1
1
1
2
1
1
1
1
1
43
24b
37c
76d
39
35
41
61e
54e
a
Reaction conditions: 1.0 mmol of R-C6H4Br-p, 1.5 mmol of styrene, 2 mmol Cs2-
CO3, 1 mmol% metal complex, DMF (3 mL), purity of compounds was checked by
NMR and yields are based on aryl bromide, all reactions were monitored by GC,
80 °C, 6 h.
b
K2CO3.
DMAc as solvent.
K2CO3, 80 °C, 15 h.
1.0 mmol of R-C6H4I-p.
c
Fig. 10. The temperature dependence of the molar magnetic susceptibility
Solid line represents fit with the Curie–Weiss law. Inset: The temperature
dependence of mT.
vm for 1.
d
a
e
v

A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
59
1 (1 mmol %)
Br
R
+
R
º
DMF, 80 C
Cs2CO3 (2 equiv.)
Scheme 1. The Heck reaction of aryl halides with styrene.
1 or 2 (1 mmol %)
B(OH)2
Br
R
R
+
º
Dioxan, 80 C
Cs2CO3 (2 equiv.)
Scheme 2. The Suzuki coupling reaction of aryl halides with phenylboronic acid.
potential bases and DMF and dioxane as solvents. We found that
the reactions performed in DMF with Cs2CO3 or K2CO3 at 80 °C
are most effective. We initiated our investigation with the coupling
of 4-bromoacetophenone with phenylboronic acid in the presence
of 1. Table 6 summarizes the results obtained with 1 and 2. The
scope of the cross-coupling reaction with respect to the aryl halide
component was also investigated. Chloroarenes do not react under
standard conditions, and yields are typically 16%. It can be seen
that 1 is an effective catalyst for the coupling of inactivated, acti-
vated and deactivated bromides (Table 6, entries 5–7).
4-Iodoanisole reacts with phenylboronic acid to afford the cou-
pled product in 61% yield (Table 6, entry 9) in contrast to 4-bromo-
anisole which does not react under standard conditions. Under
these reaction conditions, 2 was proven to be a less effective cata-
lyst than 1; however, the reaction was completed within 15 h in an
87% yield (Table 6, entry 4). Also, as shown in Table 6, 1 more effi-
ciently catalyzed the Suzuki coupling reaction with iodoarenes
than with bromoarenes (Table 6, entries 8 and 9). The purity of
coupled products was checked by NMR and the results were con-
cordant with the literature data [54,55].
Table 6
Yields of the Suzuki coupling reaction of aryl halides with phenylboronic acid.
Entry
R
Cat.
Yielda (%)
1
2
3
4
5
6
7
8
9
COCH3
COCH3
COCH3
COCH3
CHO
CH3
H
H
OCH3
1
1
1
2
1
1
1
1
1
58
38b
16c
87d
51
49
52
74e
61e
a
Reaction conditions: 1.0 mmol of R-C6H4Br-p, 1.5 mmol of phenylboronic acid,
2 mmol Cs2CO3, 1 mmol% metal complex, dioxane (3 mL), purity of compounds was
checked by NMR and yields are based on aryl bromide, all reactions were monitored
by GC, 80 °C, 6 h.
b
K2CO3.
1.0 mmol of R-C6H4Cl-p.
K2CO3, 80 °C, 15 h.
1.0 mmol of R-C6H4I-p.
c
d
e
Ni and Cu complexes have been widely used as catalysts in
cross-coupling reactions [56–61]. The reaction was thought to oc-
cur more quickly with Ni(II) and Cu(II) centered complexes, and so
1 and 2 were focused on as catalysts for Heck and Suzuki reactions.
We also investigated the catalytic activity of 3 and 4 in these cou-
pling reactions, but the coupled products could not be obtained.
3.6. Catalysis studies
3.6.1. Heck coupling reaction
We initially evaluated the catalytic activity of 1 for the coupling
reaction of 4-bromoacetophenone with styrene (Table 5, entry 1).
The selection of bases and solvents is usually important for
achieving an efficient cross coupling reaction. Widely used sol-
vents, such as DMF, DMSO, DMAc, toluene, dioxane, THF and CH3-
CN, had remarkable effects on the coupling reaction. We tested
Cs2CO3, K2CO3, K3PO4 and t-BuOK as bases. The most efficient con-
version was carried out with 1 mol% of 1 and 2 equivalents of Cs2-
CO3 in DMF at 80 °C (within 6 h). The results are summarized in
Table 5. Under these reaction conditions, a wide range of aryl bro-
mides bearing electron-donating or electron-withdrawing groups
were able to react with styrene and the coupled products were ob-
tained in yields varying from 24% to 61%. Enhancements in activity,
although less significant, were also observed when 4-bromoaceto-
phenone, rather than 4-bromobenzaldehyde was employed (Ta-
ble 5, entries 1 and 5). While 4-bromoanisole does not react
under standard conditions, 4-iodoanisole does react with styrene
to afford the coupled product in 54% yield (Table 5, entry 9). Under
these reaction conditions, 2 was proven to be the least effective
catalyst relative to 1. However, the reaction was completed within
15 h with 76% yields (Table 5, entry 4). As shown in Table 5, the 1-
catalyzed Heck coupling reaction (Scheme 1) is more efficient for
iodoarenes than for bromoarenes (Table 5, entries 8, 9).
4. Conclusions
In this article, four novel cyano-bridged coordination polymers
were synthesized and characterized by using various spectroscopic
methods. Polymeric structures of 3 and 4 were illuminated by the
X-ray single crystal method. A polymeric structure is also proposed
for compounds 1 and 2. This proposal is consistent with their non-
solubility in common solvents, shape of thermal analysis and high-
ness of thermal stabilities.
The DTGmax values of the initial decomposition stages in the
thermal analysis curves of the four complexes changed in the order
1 > 4 > 3 > 2 and this is deviated from the Irving–Williams series.
The same trend was observed for the Pt analogues of these
complexes.
X-ray single crystal studies of 3 and 4 revealed that bishydeten
acts as a tridentate ligand (N, N0, and O) in 3 while it coordinates
to Cd(II) as a bidentate ligand (N and N0) in 4. Similar coordination
behaviours were observed in the Pt analogues of these complexes
synthesized by our group. This behaviour probably arises from the
differences in the radii of the Zn and Cd metals. In addition, com-
plexes 3 and 4 were each observed to have only one ancillary bishy-
deten ligand in their coordination sphere, distinct from the hydeten
analogues [35]. This difference was thought to arise from having a
3.6.2. Suzuki coupling reaction
To determine the parameters for the Suzuki coupling reaction
(Scheme 2), we chose to examine Cs2CO3, K2CO3 and K3PO4 as

60
A. Sßenocak et al. / Polyhedron 49 (2013) 50–60
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When the magnetic properties of 1 and 2 were examined, weak
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Acknowledgments
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This work was supported by the Scientific and Technical
_
_
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_
Research Council of Turkey (TÜBITAK, Grant TBAG-104T205). Also,
27 (2008) 223.
_
_
_
we thank TÜBITAK BIDEB for the National Scholarship Program for
PhD Students.
[35] A. Karadag˘, A. Bulut, A. Sßenocak, I. Uçar, O. Büyükgüngör, J. Coord. Chem. 60
(2007) 2035.
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[39] G.H. Sheldrick, SHELXS-97 and SHELXS-97, University of Gottingen, Germany,
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Appendix A. Supplementary data
Electronic Supplementary Information (ESI) available: [Cam-
bridge Crystallographic Data Centre, CCDC ID: 783973 (3) and
789843 (4)]. Copies of the data can be obtained free of charge at
www.ccdc.cam.ac.uk. or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223
336033 or e-mail: deposit@ccdc.cam.ac.uk)].
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and Properties of New Cyano-Bridged Polymeric Transition Metal Complexes,
Doctoral Dissertation, Gaziosmanpasa University, Turkey, 2010.
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