New (NHC)Pd(II)(PPh3) complexes: synthesis, characterization, crystal structure and its application on Sonogashira and Mizoroki–Heck cross-coupling reactions

Article abstract of DOI:10.1007/s11696-019-00859-x

In this study, new six Pd-based complexes containing mixture N-heterocyclic carbene (NHC) and triphenylphosphine (PPh₃) ligands were synthesized from the reaction of the (NHC)PdI₂(pyridine) with PPh₃. The new (NHC)PdI

Full text of DOI:10.1007/s11696-019-00859-x

Chemical Papers
https://doi.org/10.1007/s11696-019-00859-x
ORIGINAL PAPER
New (NHC)Pd(II)(PPh3) complexes: synthesis, characterization, crystal
structure and its application on Sonogashira and Mizoroki–Heck
cross‑coupling reactions
Fatoş Erdemir1 · Aydın Aktaş1 · Duygu Barut Celepci2 · Yetkin Gök1
Received: 22 April 2019 / Accepted: 22 June 2019
© Institute of Chemistry, Slovak Academy of Sciences 2019
Abstract
In this study, new six Pd-based complexes containing mixture N-heterocyclic carbene (NHC) and triphenylphosphine (PPh3)
ligands were synthesized from the reaction of the (NHC)PdI2(pyridine) with PPh3. The new (NHC)PdI2(PPh3) complexes
were characterized using FTIR, 1H-NMR, 13C-NMR, and 31P-NMR spectroscopy and elemental analyses techniques. These
spectra are consistent with the proposed formula. Molecular and crystal structure of two complexes was obtained using
single-crystal X-ray difraction method. Based on the crystal results, a cis geometry was assigned to all the complexes. These
new complexes have been examined as the catalyst in the Sonogashira cross-coupling reaction. The catalytic conversions of
the complexes were obtained between 71 and 99% from the reaction of phenylacetylene and aryl bromides. Also, these new
complexes have been examined as the catalyst in the Mizoroki–Heck cross-coupling reaction. The catalytic conversions of
the complexes were obtained between 80 and 100% from the reaction of styrene and aryl bromides.
Keywords Crystal structure · Mizoroki–Heck reactions · N-Heterocyclic carbenes · Palladium complex · Sonogashira
reactions · Triphenylphosphine
Introduction
of organometallic chemists owing to their highly active and
selective properties. Thus, various Pd(II)-based mixed NHC/
phosphine complexes have been successfully designed for
various cross-coupling reactions. Diferent methods are used
for the synthesis of these complexes. One of these meth-
ods is the synthesis of Pd(II)-based mixed NHC/phosphine
complexes by exchanging ligand from the pyridine-enhanced
precatalyst preparation stabilization and initiation (PEPPSI)
complexes containing the pyridine derivative ligands. These
synthesized complexes have been widely used as the cata-
lyst in cross-coupling reactions (Aktaş et al. 2018a, b, 2019;
Boubakri et al. 2017; Dehimat et al. 2018; Touj et al. 2018;
Herrmann et al. 2001, 2003; Liao et al. 2009; Chan et al.
2010; Diebolt et al. 2010; Schmid et al. 2013).
The activity of homogeneous catalysts is dependent on ancil-
lary ligands, which are largely coordinated with the metal
center (Cornils and Herrmann 1996; Beller and Bolm 1998).
In recent years, the synthesis studies for the synthesis of
palladium-based complexes containing both NHC and phos-
phine ligands have been increasing. In the beginning, the
NHC ligands were selected as alternative ligands to the phos-
phine ligands (Glorius 2006; Diez-Gonzalez et al. 2009).
Both that the metal-carbene bond is more resistant than the
metal-phosphorus bond and that the property of the carbene
ligand can be adjusted electronically and sterically are the
most important reasons for this alternative. However, the
catalysts containing both these ligands attracted the interest
Pd(II)-based vinylic substitution of organometallic rea-
gents was frst reported by Heck (1982) who used stoichio-
metric amounts of Pd(II) salts. Palladium-catalyzed cross-
coupling reactions gained the reputation they deserved
by winning the Chemistry Nobel Prize in 2010. Heck and
Nolley (1972) then independently reported the arylation of
alkenes using aryl halides as electrophiles with a palladium
complex as the catalyst in the presence of a base. In recent
years, Mizoroki–Heck reactions have become an important
* Aydın Aktaş
aydinaktash@hotmail.com
1
2
Department of Chemistry, İnönü University, Faculty
of Science, 44280 Malatya, Turkey
Department of Physics, Dokuz Eylül University, Faculty
of Science, Buca, 35160 İzmir, Turkey
Vol.:(0123456789)
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Chemical Papers
tool for the formation of C–C bonds in organic syntheses
(Mizoroki et al. 1971; Whitcombe et al. 2001; Dounay and
Overman 2003; Beletskaya and Cheprakov 2000; Kondolf
et al. 2003; Oestreich 2009; Watson 2016). Pd-based cata-
lysts are used in the Mizoroki–Heck reactions because of
their selectivity in the bonding of various electrophiles
which are not toxic, and especially exhibiting high reactiv-
ity (Menezes da Silva et al. 2016).
spectrometer. Proton (1H), Phosphorous (31P), and Carbon
(13C) NMR spectra were recorded using either a Bruker
AS 400 Merkur spectrometer operating at 400 MHz (1H),
100 MHz (13C) in CDCl3 with tetramethylsilane as an inter-
nal reference. All reactions were observed on an Agilent
6890 N GC system by GC-FID with an HP-5 column of
30 m length, 0.32 mm diameter and 0.25 μm flm thickness.
Elemental analyses were performed by İnönü University
Scientifc and Technological Research Center (Malatya,
TURKEY).
The Pd catalyzed C(sp2)–C(sp) cross-coupling reaction of
terminal acetylenes with aryl halides are known as Sonoga-
shira coupling (Sonogashira 2002). The triple bond (C≡C)
in the alkynes that is found in material sciences and some
important biochemicals is known as the ideal functional
group for the synthesis of versatile and important organic
molecules (Cosford et al. 2003; Bagley et al. 2005). This
reaction is generally carried out using the copper (I) salts as
the co-catalysts and amines as solvents (Alonso et al. 2003).
Recently, in the Sonogashira cross-coupling reactions, we
evaluated the potential reactivity and catalytic applications
of Pd(II) complexes containing the mixed NHC/phosphine
ligand (Aktaş et al. 2018a, b, 2019; Boubakri et al. 2017;
Dehimat et al. 2018; Touj et al. 2018; Herrmann et al. 2001,
2003; Liao et al. 2009; Chan et al. 2010; Diebolt et al. 2010;
Schmid et al. 2013).
Single-crystal X-ray difraction data of the complexes 1b
and 1f were recorded at room temperature by ω-scan tech-
nique, on a Rigaku-Oxford Xcalibur difractometer with an
EOS-CCD area detector operated at 50 kV and 40 mA using
graphite-monochromated MoKα radiation (λ=0.71073 Å)
from an enhance X-ray source with CrysAlisPro software
(CrysAlisPro 2015). Data collections, reductions, and
analytical absorption corrections were performed using
CrysAlisPro software package (Clark and Reid 1995). Struc-
ture solutions were performed using SHELXT (Sheldrick
2015a) embedded in the Olex2 (Dolomanov 2009). Refne-
ment of coordinates and anisotropic thermal parameters of
non-hydrogen atoms were carried out by the full-matrix
least-squares method in SHELXL (Sheldrick 2015b). For
both complexes, hydrogen atoms were placed using stand-
ard geometric models and with their thermal parameters
riding on those of their parent atoms. During the structure
analysis, two disordered dichloromethane solvent molecules
in the complex 1b and two disordered chloroform solvent
molecules in 1f were observed. Total volumes of these sol-
vent molecules are 293 Å3 and 334 Å3, respectively. Density
identifed in these solvent-accessible areas was calculated
and corrected for using the solvent mask in Olex2. In 1b,
two carbon atoms are disordered with a 44:56 (C25:C25A;
C26:C26A) population distribution in one of the benzene
rings of PPh3. The details of the crystal data, data collec-
tion and structure refnement of the complexes are given
in Table 1.
As a continuation of our studies (Aktaş et al. 2018a, b,
2019) on the development of palladium-based mixed NHC/
phosphine ligand catalysts, we describe here the synthesis
of a series of Pd (II) based mixed NHC/phosphine com-
plexes. In particular, these Pd (II) complexes containing
mixed NHC/phosphine ligand can be used as efective cata-
lysts in the Sonogashira and Mizoroki–Heck cross-coupling
reactions with various aryl halides (aryl chlorides and aryl
bromides). The structure of two of these complexes was con-
frmed by the single-crystal X-ray difraction method. Also,
we have researched the catalytic activity of all complexes in
the Sonogashira and Mizoroki–Heck cross-coupling reac-
tions and they demonstrated excellent activity in these cross-
coupling reactions.
Experimental
Synthesis
All syntheses involving Pd(II) based mixed NHC/phosphine
complexes 1a–f were prepared under an inert atmosphere in
fame-dried glassware using standard Schlenk techniques.
The solvents used were commercially available and used
without purifcation.
Synthesis of diiodo[1‑benzyl‑3‑(2‑hydroxyethyl)
benzimidazol‑2‑ylidene]triphenyl
phosphinepalladium (II), 1a
For this synthesis of the (NHC)PdI2(PPh3) complex,
first, diiodo[1-benzyl-3-(2-hydroxyethyl)benzimidazol-
2-ylidene]pyridinepalladium(II) (138 mg, 0.2 mmol) and
triphenylphosphine PPh3 (52 mg, 0,2 mmol) were added
in chloroform (10 mL) at room temperature (Aktaş et al.
2018a, b, 2019). The reaction mixture was stirred for 24 h
at room temperature. Then, solvents were evaporated under
All other reagents were commercially available from
Sigma-Aldrich, abcr and Merck Chemical Co. and used
without further purifcation. Melting points were identifed
in glass capillaries under air with an Electrothermal-9200
melting point apparatus. FT-IR spectra were saved in the
range 400–4000 cm−1 on Perkin Elmer Spectrum 100 FT-IR
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Table 1 Crystallographic
data and structure refnement
parameters for 1b and 1f
1b
1f
Formula
C35H33I2N2OPPd
888.80
Monoclinic
0.454×0.251×0.244
P21/c, 4
15.8083(8)
C38H39I2N2OPPd
930.88
Triclinic
0.475×0.363×0.275
P-1, 2
10.8564(5)
Formula weight (g/mol−1
Crystal system
Crystal size (mm3)
Space group, Z
a (Å)
)
b (Å)
c (Å)
11.8071(5)
19.1353(8)
12.0155(6)
16.0984(8)
α, β, γ (°)
90, 96.738(4), 90
3546.9(3)
1.664
2.337
84.738(4), 82.502(4), 85.119(4)
2067.53(18)
1.495
2.008
Volume (Å3)
ρcalc (mg m−3
)
μ (mm−1
F (000)
)
1728
912
Refections collected
Independent refections
Parameters
11,151
10,081
6208 [Rint =0.0231, Rsigma =0.0411]
399
1.036
7250 [Rint =0.0211, Rsigma =0.0494]
411
1.032
GOF on F2
Final R indices [I>2σ(I)]
R indices (all data)
R1 =0.0379 wR2 =0.0927
R1 =0.0539 wR2 =0.1002
R1 =0.0398 wR2 =0.0790
R1 =0.0563 wR2 =0.0870
vacuum to get the product as a yellow solid. The crude
product was washed with n-pentane and recrystallized from
chloroform/n-pentane (1:2) at room temperature. Yield:
and 3.01 (s, 2H, –NCH2CH2OH); 4.42 and 4.75 (s, m, 2H,
–NCH2CH2OH); 5.29 and 5.85 (s, 2H, –NCH2C6H4(CH3));
6.99–7.89 (m, 23H, Ar–H). 13C {1H}NMR (100 MHz,
CDCI3) δ (ppm)=19.7 (–NCH2C6H4(CH3)); 50.3 and 50.4
(–NCH2CH2OH); 51.4 and 53.4 (–NCH2C6H4(CH3)); 59.8
and 60.3 (–NCH2CH2OH); 111.0–111.3–111.5–123.1–12
7.7–127.8–127.9–128.3–128.4–130.3–135.1–135.2–135
.3 and 149.8 (Ar–C); 178.3 (2-C) 31P {1H}NMR (CDCI3,
162 MHz, δ, ppm)=16.1 and 24.3.
73% (0.128 g); m.p: 88–90 °C; ν(CN): 1434 cm−1; ν(O–H)
:
3453 cm−1. Anal. Calc. for C34H31I2N2OPPd: C: 46.68; H:
3.57; N: 3.20. Found: C: 46.73; H: 3.50; N: 3.23. 1H NMR
(400 MHz, CDCI3) δ (ppm)=2.17 (s, 1H, –NCH2CH2OH);
3.96 (s, 2H, NCH2CH2OH); 4.10 (s, 2H, –NCH2CH2OH);
5.81 (s, 2H, –NCH2(C6H5); 6.27–7.63 (m, 23H, Ar–H). 13
C
{1H} NMR (100 MHz, CDCI3) δ (ppm) = 51.3 (–NCH-
2CH2OH); 54.5 (–NCH2(C6H5)); 59.9 (–NCH2CH2OH); 110
.9–111.8–127.9–128.0–128.1–128.2–128.4–128.6–128.9–
130.3–131.1–131.9–132.3–134.5 and 135.3 (Ar–C); 171.7
(2-C). 31P {1H} NMR (CDCI3, 162 MHz, δ, ppm)=27.0.
Synthesis
of diiodo[1‑(2‑hydroxyethyl)‑3‑(3‑methylbenzyl)
benzimidazol‑2‑ylidene] triphenylphosphinepallad
ium(II), 1c
Synthesis
The synthesis of 1c was prepared in the same way as that
described for 1a, but diiodo[1-(2-hydroxyethyl)-3-(3-meth-
ylbenzyl)benzimidazol-2-ylidene]pyridinepalladium(II)
(141 mg, 0.2 mmol) was used instead of dichloro[1-
(2-hydroxyethyl)-3-benzylbenzimidazol-2-ylidene]
pyridinepalladium(II). Yield: 72% (0.128 g); m.p:
138–140 °C; ν(CN): 1433 cm−1; ν(O–H): 3738 cm−1. Anal.
Calc. for C35H33I2N2OPPd: C: 47.29; H: 3.74; N: 3.15.
of diiodo[1‑(2‑hydroxyethyl)‑3‑(2‑methylbenzyl)
benzimidazol‑2‑ylidene] triphenylphosphinepallad
ium(II), 1b
The synthesis of 1b was prepared in the same way as that
described for 1a, but diiodo[1-(2-hydroxyethyl)-3-(2-meth-
ylbenzyl)benzimidazol-2-ylidene]palladium(II) (141 mg,
0.2 mmol) was used instead of diiodo[1-(2-hydroxyethyl)-
3-benzylbenzimidazol-2-ylidene]pyridine palladium(II).
Yield: 77% (0.137 g); m.p: 149–151 °C; ν(CN): 1433 cm−1;
ν(O–H): 3446 cm−1. Anal. Calc. for C35H33I2N2OPPd: C:
47.29; H: 3.74; N: 3.15. Found: C: 47.32; H: 3.72; N: 3.12.
1H NMR (400 MHz, CDCI3) δ (ppm)=1.62 (s, 1H, –NCH-
2CH2OH); 2.33 and 2.49 (s, 3H, –NCH2C6H4(CH3)); 2.94
1
Found: C: 47.33; H: 3.78; N: 3.09. HNMR (400 MHz,
CDCI3) δ (ppm) = 5.35 (s, 1H, –NCH2CH2OH); 2.53 (s,
3H, –NCH2C6H4(CH3)); 4.48 (s, 2H, –NCH2CH2OH); 4.99
(t, 2H, J=6 Hz –NCH2CH2OH); 6.01 (s, 2H, –NCH2C6H4–);
6.55-7.49 (m, 23H, Ar–H). 13C {1H}NMR (100 MHz,
CDCI3) δ (ppm)=20.0 (–NCH2C6H4(CH3)); 51.8 (–NCH-
2CH2OH); 52.4 (–NCH2C6H4(CH3)); 61.1 (–NCH2CH2OH);
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Chemical Papers
110.6–111.2–111.4–114.1–123.4–123.4–126.5–128.2–
128.7–130.6–132.2–135.0–138.4–148.3–149.3–157.4
and 158.0. (Ar–C); 167.0 (2-C). 31P {1H}NMR (CDCI3,
162 MHz, δ, ppm)=29.5.
Synthesis of diiodo[1‑(2‑hydroxyethyl)‑3‑(2,3,5
,6‑tetramethylbenzyl)benzimidazol‑2‑ylidene]trip
henylphosphinepalladium(II), 1f
The synthesis of 1e was prepared in the same way as
that described for 1a, but diiodo[1-(2-hydroxyethyl)-
3-(2,3,5,6-tetramethylbenzyl)benzimidazol-2-ylidene]
pyridinepalladium(II) (149 mg, 0.2 mmol) was used
instead of diiodo[1-(2-hydroxyethyl)-3-benzyl benzi-
midazol-2-ylidene] pyridinepalladium(II). Yield: 65%
Synthesis
of diiodo[1‑(2‑hydroxyethyl)‑3‑(4‑methylbenzyl)
benzimidazol‑2‑ylidene] triphenylphosphinepallad
ium(II), 1d
(0.121 g); m.p: 168–169 °C; ν(CN): 1434 cm−1; ν(O–H)
:
The synthesis of 1d was prepared in the same way as that
described for 1a, but diiodo[1-(2-hydroxyethyl)-3-(4-meth-
ylbenzyl)benzimidazol-2-ylidene]pyridinepalladium(II)
(141 mg, 0.2 mmol) was used instead of diiodo[1-
(2-hydroxyethyl)-3-benzylbenzimidazol-2-ylidene]
pyridinepalladium(II). Yield: 73% (0.130 g); m.p:
88–90 °C; ν(CN): 1433 cm−1; ν(O–H): 3442 cm−1. Anal. Calc.
for C35H33I2N2OPPd: C: 47.29; H: 3.74; N: 3.15. Found:
3556 cm−1. Anal. Calc. for: C38H39I2N2OPPd: C: 49.03; H:
4.22; N: 3.01. Found: C: 49.01; H: 4.26; N: 3.05. 1HNMR
(400 MHz, CDCI3) δ (ppm)=1.57 (s, 1H, –NCH2CH2OH);
1.93, 2.13 and 2.23 (s, 15H, –NCH2C6(CH3)5); 4.42 (m,
2H, –NCH2CH2OH); 4.77 (t, 2H, J: 4 Hz –NCH2CH2OH);
5.93 (s, 2H, –NCH2C6(CH3)5); 7.00–7.76 (m, 19H, Ar–H).
13C {1H} NMR (100 MHz, CDCI3) δ (ppm) = 15.4 and
19.8 (–NCH2C6H4(CH3)); 44.3 (–NCH2CH2OH); 54.6
(–NCH2C6H4(CH3)); 65.8 (–NCH2CH2OH); 110.5–111.1–
111.6–122.4–122.9–123.2–127.7–127.9–128.0–128.3–128
.4–129.4–130.3–130.4–132.0–132.5–132.7–133.1–134.3–1
35.2–135.3–135.6 and 136.3. (Ar–C); 173.4 (2-C). 31P {1H}
NMR (CDCI3, 162 MHz, δ, ppm)=12.8–15.9 and 23.7.
1
C: 47.33; H: 3.76; N: 3.12. HNMR (400 MHz, CDCI3)
δ (ppm) = 1.60 (s, 1H, –NCH2CH2OH); 2.29 and 2.34 (s,
3H, –NCH2C6H4(CH3)); 4.41 (s, 2H, –NCH2CH2OH); 5.29
(s, 2H, –NCH2CH2OH); 5.84 (s, 2H, –NCH2C6H4–); 6.94-
7.72 (m, 23H, Ar–H). 13C {1H}NMR (100 MHz, CDCI3) δ
(ppm) = 21.2 (–NCH2C6H4(CH3)); 50.3 and 51.2 (–NCH-
2CH2OH); 53.2 and 54.2 (–NCH2H4(CH3));110.8–111.8–12
2.9–123.0–127.9–128.0–128.1–128.2–128.4–129.4–130.3–
131.1–131.7–132.0–132.4–134.4–134.5–134.6–135.1–135
.3 and 137.8. (Ar–C); 171.5 (2-C). 31P {1H}NMR (CDCI3,
162 MHz, δ, ppm)=16.0 and 23.9.
General procedure for the catalytic activity of (NHC)
PdI2PPh3 complexes in Sonogashira cross‑coupling
reaction
For the catalytic activity of (NHC)PdI2PPh3 complexes in
Sonogashira cross-coupling reaction, frst, phenylacetylene
(1.5 mmol), aryl halides (1 mmol), Cs2CO3 (2 mmol) and
(NHC)PdI2PPh3 complexes 1a–f (0.01 mmol) were dissolved
in DMF (2 ml) in a small Schlenk tube as described in the
literature (Aktaş et al. 2018a, b, 2019). The reaction mixture
was stirred in an oil bath at 80 °C for 4 h. Then, the reaction
mixture was cooled to room temperature. The solvent was
evaporated under vacuum. The mixture was passed through
(1 cm thick) silica gel column using an ethyl acetate/n-hex-
ane (1/5) solvent mixture. After the excess of the solvent was
evaporated, the products were checked by gas chromatogra-
phy (GC). The conversions were calculated as the conversion
of aryl halides to diphenylacetylene products.
Synthesis of diiodo[1‑(2‑hydroxyethyl)‑3‑(2,4,6
‑trimethylbenzyl)benzimidazol‑2‑ylidene]triph
enylphosphinepalladium(II), 1e
The synthesis of 1e was prepared in the same way as
that described for 1a, but diiodo[1-(2-hydroxyethyl)-
3-(2,4,6-trimethylbenzyl)benzimidazol-2-ylidene]
pyridinepalladium(II) (146 mg, 0.2 mmol) was used
instead of diiodo[1-(2-hydroxyethyl)-3-benzyl benzi-
midazol-2-ylidene] pyridinepalladium(II). Yield: 70%
(0.128 g); m.p: 283–285 °C; ν(CN): 1434 cm−1; ν(O–H)
:
3359 cm−1. Anal. Calc. for C37H37I2N2OPPd: C: 48.47;
H: 4.07; N: 3.06. Found: C: 48.51; H: 4.10; N: 3.09.
1HNMR (400 MHz, CDCI3) δ (ppm)=1.57 (s, 1H, –NCH-
2CH2OH); 1.91 and 2.25 (s, 9H, –NCH2C6H2(CH3)3); 4.33
(m, 2H, –NCH2CH2OH); 4.69 (m, 2H, –NCH2CH2OH);
5.77 (s, 2H, –NCH2C6H2–); 6.81–7.66 (m, 21H, Ar–H).
13C {1H}NMR (100 MHz, CDCI3) δ (ppm) = 14.7 and
18.6 (–NCH2C6H2(CH3)3); 42.5 (–NCH2CH2OH); 56.2
(–NCH2C6H2(CH3)3); 62.6 (–NCH2CH2OH); 111.3–125.0–
128.2–128.3–129.0–129.5–131.4–132.7–134.9–135.1–138
.2 and 149.6. (Ar–C); 174.2 (2-C). 31P {1H}NMR (CDCI3,
162 MHz, δ, ppm)=27.0 and 29.7.
General procedure for the catalytic activity
of (NHC)PdI2PPh3 complexes in Mizoroki–Heck
cross‑coupling reaction
For the catalytic activity of (NHC)PdI2PPh3 complexes
in Mizoroki–Heck cross-coupling reaction, frst, styrene
(1.5 mmol), aryl halides (1 mmol), KOAc (2 mmol) and
(NHC)PdI2PPh3 complexes 1a–f (0.01 mmol) were dis-
solved in DMF/(CH3)2CHOH (1:1) (2 ml) in a small Schlenk
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Chemical Papers
a
b
c
d
e
f
Scheme 1 Synthesis (NHC)PdI2PPh3 complexes 1a–f
tube. The reaction mixture was stirred in an oil bath at 80 °C
for 4 h. Then, the reaction mixture was cooled to room tem-
perature. The solvent was evaporated under vacuum. The
mixture was passed through (1 cm thick) silica gel column
using an ethyl acetate/n-hexane (1/5) solvent mixture. After
the excess of the solvent was evaporated, the products were
checked by gas chromatography (GC). The conversions were
calculated as the conversion of aryl halides to diphenyle-
thene products.
that are observed between 160.0 and 162.0 in the 13C NMR
spectra of the starting PEEPSI complexes were highly
downfeld shifted at δ 171.7, 178.3, 167.0, 171.5, 174.2
and 173.4 ppm for complexes 1a–f, respectively. The Pd–P
resonances of the (NHC)PdI2PPh3 complexes in the 31P
NMR spectra appeared highly downfeld shifted at δ 27.0,
16.1–24.3, 25.9, 16.0–23.9, 25.3 and 12.8–15.9–23.7 ppm
for 1a–f, respectively. The FT-IR data clearly indicated
the presence of ν(CN) at 1434, 1433, 1433, 1433, 1434,
1434 cm−1 for the (NHC)PdI2PPh3 complexes 1a–f, respec-
tively. The FT-IR data clearly indicated the presence of
ν(OH) at 3453, 3446, 3738, 3442, 3359 and 3556 cm−1
for the (NHC)PdI2PPh3 complexes 1a–f, respectively. The
results of all data are consistent with similar studies (Aktaş
et al. 2018a, b, 2019; Boubakri et al. 2017; Dehimat et al.
2018; Touj et al. 2018). When we evaluated which is one
of the analytical techniques used to prove the synthesis of
compounds, it was observed that the calculated values were
very close to the found values. Also, we have obtained an
appropriate single-crystal for complexes 1b and 1f by using
X-ray difraction method.
Results and discussion
Synthesis of (NHC)PdI2PPh3 complexes (1a–f)
In here we have defned the new 2-hydroxyethyl-substi-
tuted (NHC)PdI2PPh3 complexes illustrated in Scheme 1.
These complexes 1a–f have been prepared from the (NHC)
PdI2(pyridine) complexes (PEPPSI) with the PPh3. The air
and moisture-stable complexes 1a–f are soluble in halogen-
ated solvents such as dichloromethane and chloroform. The
new (NHC)PdI2PPh3 complexes were obtained as a yellow
solid in between 65 and 77% yields. The isolated products
were identifed and characterized on the basis of elemental
The catalytic activity of (NHC)PdI2PPh3 complexes
in Sonogashira cross‑coupling reaction
1
and spectroscopic analysis (FTIR, H, 13C, 31P NMR and
elemental analyses data) techniques. The 1H-NMR spectra of
(NHC)PdI2PPh3 complexes, when compared with the start-
ing PEPPSI complexes (Erdemir et al. 2019), the pyridine
peaks between 7.50 and 9.00 were not observed. Instead, an
increase in aromatic peaks between 7.00 and 8.00, attributed
to the PPh3, was observed. Similarly, no signs of the pyridine
peaks on 13C-NMR spectra were observed between 153.0
and 155.0 for the corresponding PEPPSI complexes. Instead,
an increase in aromatic peaks between 120.0 and 130.0 from
the PPh3 was observed. Also, the Pd–Carbene resonances
In this work, we performed the Sonogashira coupling reac-
tion in DMF using (NHC)PdI2PPh3 complexes 1a–f as cata-
lyst. Thanks to the unique electronic properties of NHC and
PPh3 ligands, all complexes exhibited high catalytic activ-
ity in the Sonogashira cross-coupling reaction. In the litera-
ture, when the DMF was used as the solvent, the catalytic
activities of (NHC)Pd(II)PPh3 complexes in Sonogashira
cross-coupling reaction obtained higher conversions (Aktaş
et al. 2018a, b). Thus, we used DMF as the solvent. The
catalytic activities of (NHC)PdI2PPh3 complexes 1a–f were
1 3

Chemical Papers
Table 2 The catalytic activity of phenylacetylene with aryl bromides in Sonogashira cross-coupling reactions catalyzed by (NHC)PdI2PPh3 com-
plexes 1a–f
Entry
R
Product
2
Cat.
Conversion (%)
1
2
3
4
5
6
7
8
–COCH3
1a
1b
1c
1d
1e
1f
1a
1b
1c
1d
1e
1f
1a
1b
1c
1d
1e
1f
92
89
>99
>99
99
94
82
78
79
96
97
94
79
75
71
83
90
89
–CH3
3
4
9
10
11
12
13
14
15
16
17
18
–OCH3
Reaction conditions Phenylacetylene (1.5 mmol), 4-bromoaryl (1 mmol), (NHC)PdI2PPh3 complexes 1a–f (0.01 mmol) and Cs2CO3 (2 mmol)
were added in DMF (3 ml) to the Schlenk tube in open air. It was stirred at 80 °C for 4 h
examined in Sonogashira cross-coupling reactions under
optimum conditions (Aktaş et al. 2018a, b). Phenylacety-
lene (1.5 mmol), 4-arylhalides (1 mmol), (NHC)PdI2PPh3
complexes 1a–f (0.01 mmol) and Cs2CO3 (2 mmol) were
added in DMF (2 ml) to the Schlenk tube in open air. It
was stirred at 80 °C for 4 h. Then, the solvent (DMF) was
evaporated under vacuum. The residue was passed through
a silica gel column (1 cm thick) by using ethyl acetate/n-
hexane (1/5) solvent mixture. After the redundancy of the
solvent was evaporated, the products were checked using
GC. The results were calculated as the conversion of the
aryl halides to diphenylacetylene products. Conversions
were illustrated in Tables 2, 3 and 4. Also, the dimeriza-
tion product of phenylacetylene was observed at the end of
the catalysis experiments (Nishihara et al. 2000; Aktaş et al.
2018a, b). But this dimerization product was not taken into
account in the conversion calculations.
in the Sonogashira cross-coupling reactions. As mentioned
in our recently published study, the electronic properties
of aryl halides are efective in catalytic conversions (Aktaş
et al. 2018a, b). In the catalytic experiments performed with
the aryl halides (containing chloride, bromide, and iodide)
diferent results were obtained (Tables 2, 3, 4).
In the result of the experiments with iodinated aryl hal-
ides, very high conversions were obtained in a shorter time
(Table 3), while in the result of experiments with chlorin-
ated aryl halides, very low conversions were obtained over
a longer time (Table 4). This is related to the durability or
weakness of the bond between carbon (Cbenzene) and halogen
atoms (C–X). First, when the orbitals forming the Cbenzene–X
bond in the aryl halide are examined [Cbenzene (2sp2), Cl
(3p), Br (4p) and I (5p) orbital], the overlap rates of the
orbitals are 2sp2–3p>2sp2–4p>2sp2–5p, respectively. The
durability of the Cbenzene–X bond happens due to the fact
that the orbital overlap decreases in the following order:
Cbenzene–Cl>Cbenzene–Br>Cbenzene–I. Second, the anion sta-
bility of the leaving group (halides) decreases in the follow-
ing order: I− >Br− >Cl−. The more stable the anion (halides)
Here, we examined the catalytic effects of (NHC)
PdI2PPh3 complexes 1a–f in the coupling reactions of aryl
halides and phenyl acetylene. The (NHC)PdI2PPh3 com-
plexes 1a–f exhibited high catalytic activity as the catalyst
1 3

Chemical Papers
Table 3 The catalytic activity of phenylacetylene with iodotoluene in Sonogashira cross-coupling reactions catalyzed by (NHC)PdI2PPh3 com-
plexes 1a–f
Entry
Product
5
Cat.
Conversion (%)
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
97
94
98
99
99
>99
Reaction conditions Phenylacetylene (1.5 mmol), 4-iodotoluene (1 mmol), (NHC)PdI2PPh3 complexes 1a–f (0.01 mmol) and Cs2CO3 (2 mmol)
were added in DMF (3 ml) to the Schlenk tube in open air. It was stirred at 50 °C for 30 min
Table 4 The catalytic activity of phenyl acetylene with 4-chloroacetophenone in Sonogashira cross-coupling reactions catalyzed by (NHC)
PdI2PPh3 complexes 1a, 1d and 1e
Entry
R
Product
6
Cat.
Con-
version
(%)
1
2
3
–COCH3
1a
1d
1e
18
21
32
Reaction conditions Phenylacetylene (1.5 mmol), 4-chloroacetophenone (1 mmol), (NHC)PdI2PPh3 complex 1a, 1d and 1e (0.01 mmol) and
Cs2CO3 (2 mmol) were added in DMF (3 ml) to the Schlenk tube in open air. It was stirred at 80 °C for 16 h
is, the weaker the C–X bond is. Thus, the conversions of
substrates in catalytic reactions decrease, respectively, as
follows: aryl iodide>aryl bromide>aryl chloride (Tables 2,
3, 4).
–OCH3) are used, the conversions of catalytic reactions are
less (Tables 3, 4).
Finally, in our study, the substitution groups that were dif-
ferent in the (NHC)PdI2PPh3 complexes 1a–f had little efect
on catalytic conversions. The conversions were obtained
slightly higher in the catalytic reactions containing bulky
substituents. Also, the (NHC)PdI2PPh3 complexes 1a–f were
observed to be active catalysts compared to the similar stud-
ies previously published (Aktaş et al. 2018a, b, 2019; Bou-
bakri et al. 2017; Dehimat et al. 2018; Touj et al. 2018).
In a similar study that we have published recently, (NHC)
Pd(II)PPh3 complexes containing chloride and bromide
ligand were used for the same catalytic reaction (Aktaş et al.
2018a, b, 2019). We observed that the halide ligands in the
complexes had little efect on catalytic activity.
The groups of –OCH3, –CH3 and –COCH3 in the para
position of the aryl halides used as substrates afect the
aromatic ring electronically (Aktaş et al. 2013, 2018a, b,
2019; Aktas and Gök 2014, 2015; Sarı et al. 2017; Erdoğan
et al. 2018; Gök et al. 2018; Gök et al. 2019). The elec-
tron withdrawing group (–COCH3) weakens the Cbenzene–X
bond in the para position while the electron donating groups
(–CH3 and –OCH3) strengthen the Cbenzene–X bond. Thus,
when electron withdrawing groups (–COCH3) are used in
substrates, the conversions of catalytic reactions are higher
(Table 2). But, when electron donating groups (–CH3,
1 3

Chemical Papers
Table 5 The catalytic activities of (NHC)PdI2PPh3 complex 1f using diferent bases in the Mizoroki–Heck cross-coupling reactions
Entry
Solvent
Base
Temperature (°C)
Time (h)
Conversion (%)
1
2
3
4
5
6
7
8
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
KOBut
K2CO3
NaOH
KOH
Na2CO3
Cs2CO3
KACO3
KOAc
100
100
100
100
100
100
100
100
4
4
4
4
4
4
4
4
99
58
70
99
54
94
99
100
Reaction conditions Styrene (1.5 mmol), 4-bromoacetophenone (1 mmol), (NHC)PdI2PPh3 complex 1f (0.01 mmol) and base (2 mmol) were
added in DMF (3 ml) to the Schlenk tube in open air. Was stirred at 100 °C for 4 h
[DMF/(CH3)2CHOHv(1/2), DMF/H2O (2/1), and EtOH/
H2O (1/2)] were used. The results of the experiment were
checked using GC. The conversion of the products was
calculated by taking 4-bromoacetophenone into con-
sideration. The conversions were illustrated in Table 6.
The high conversion was obtained when DMF and DMF/
(CH3)2CHOH (1/2) solvent mixture was used as the
solvent. The DMF/(CH3)2CHOH (1/2) solvent system
was used since it is cheaper. Thus DMF/(CH3)2CHOH
(1/2) mixture was used as the solvent in the following
experiments.
The catalytic activity of (NHC)PdI2PPh3 complexes
in Mizoroki–Heck Cross‑coupling reaction
We performed the Mizoroki–Heck cross-coupling reac-
tion using (NHC)PdI2PPh3 complexes 1a–f as the catalyst.
To determine the optimum conditions, suitable base was
selected frst. The (NHC)PdI2PPh3 complex 1f was mixed
with styrene and 4-bromoacetophenone in DMF (3 ml), at
100 °C for 4 h using KOBut, K2CO3, NaOH, KOH, Na2CO3,
K2CO3, Cs2CO3, and KOAc bases. Then, DMF was removed
under vacuum and the reaction mixture was purifed by pass-
ing it through a silica gel column (1 cm thick) in a mixture of
ethyl acetate/n-hexane (1/5). After the redundant solvent was
evaporated, the remaining reaction mixture was injected into
the GC. The conversion was calculated as the conversion of
4-bromoacetophenone to the products. The conversions are
illustrated in Table 5. When KOAc was used as the base, the
highest conversion was obtained. Thus KOAc was used as a
base in the next experiments.
The palladium-catalyzed Mizoroki–Heck cross-cou-
pling reaction is the most effective way to bind aryl/
vinyl halides. After Heck’s pioneering work, Mizoroki
et al. published preliminary results for the purifcation of
the alkenes catalyzed by iodobenzene in the presence of
potassium acetate. Then, Mizoroki et al. (Mori et al. 1973)
extended their preliminary study to aryl bromides. How-
ever, they were discovered to be much less reactive than
aryl iodides. The reactivity of the aryl halides decreases in
the following order: PhI > PhBr ≫ PhCl. Then, Mizoroki
et al. reported that the use of the phosphine ligand (PPh3)
was somewhat advantageous (Mori et al. 1973). Dieck and
Heck (1974) developed the use of PPh3 with palladium
acetate. After this study, a mechanism for reactions cata-
lyzed by palladium acetate was proposed by Dieck and
Heck (1974) against monophosphine ligands. The mecha-
nism (Heck 1978, 1979) was presented as a catalytic cycle
for successive reactions by Heck.
The selection of the solvent is important for catalytic
reactions. The solvent must dissolve the base, substrates and
especially the Pd complex in the solvent. Another important
issue is the coordination of the solvent (such as water and
pyridine) to the metal center. This condition can afect the
catalytic activity of Pd complexes because of its altering the
structure of the Pd complex (Li et al. 2019).
The solvents were determined after selecting the base
for optimum conditions. The styrene (1.5 mmol), 4-bro-
moacetophenone (1 mmol), (NHC)PdI2PPh3 complex
1f (0.01 mmol) and KOAc (2 mmol) were added in the
solvent (3 ml) to the Schlenk tube in open air. It was
stirred at 80 °C for 4 h. Three diferent solvents (DMF,
(CH3)2CHOH, and EtOH) and three solvent mixtures
In our study, we used the (NHC)PdI2PPh3 complexes
1a–f for the Palladium-catalyzed Mizoroki–Heck cross-
coupling reaction. In this reaction, we examined the cou-
pling of styrene and aryl halides. In general, we observed
1 3

Chemical Papers
Table 6 The catalytic activities of (NHC)PdI2PPh3 complex 1f using diferent solvents in the Mizoroki–Heck cross-coupling reactions
Entry
Solvent
Base
Temperature (°C)
Time (h)
Conversion (%)
1
2
3
4
5
6
DMF/H2O
EtOH/H2O
EtOH
(CH3)2CHOH
DMF
KOAc
KOAc
KOAc
KOAc
KOAc
KOAc
80
80
80
80
80
80
4
4
4
4
4
4
35
24
12
73
100
100
DMF/(CH3)2CHOH
Reaction conditions Styrene (1.5 mmol), 4-bromoacetophenone (1 mmol), (NHC)PdI2PPh3 complex 1f (0.01 mmol) and KOAc (2 mmol) were
added in the solvent (1/2) (3 ml) to the Schlenk tube in open air. Was stirred at 80 °C for 4 h
Table 7 The catalytic activity of styrene with arylbromide in the Mizoroki–Heck cross-coupling reactions catalyzed by (NHC)PdI2PPh3 com-
plexes 1a–f
Entry
R
Product
7
Cat.
Conversion (%)
1
2
3
4
5
6
7
8
–COCH3
1a
1b
1c
1d
1e
1f
1a
1b
1c
1d
1e
1f
1a
1b
1c
1d
1e
1f
100
100
100
88
100
100
85
98
97
95
82
80
88
85
95
83
85
80
–OCH3
–CH3
8
9
9
10
11
12
13
14
15
16
17
18
Reaction conditions Styrene (1.5 mmol), arylbromide (1 mmol), (NHC)PdI2PPh3 complexes 1a–f (0.01 mmol) and KOAc (2 mmol) were added
in DMF/(CH3)2CHOH (1/2) (3 ml) to the Schlenk tube in open air. Was stirred at 80 °C for 4 h
that all the (NHC)PdI2PPh3 complexes 1a–f were active.
The reactivity of the aryl halides was obtained in accord-
ance with the literature as PhI>PhBr≫PhCl, respectively
(Oestreich 2009).
Here, the coupling reactions of the aryl bromides with
styrene were examined as catalysts for all (NHC)PdI2PPh3
complexes 1a–f. The results we obtained from the Mizo-
roki–Heck cross-coupling were in parallel with the results
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Chemical Papers
Table 8 The catalytic activity of styrene with 4-iodotoluene in the Mizoroki–Heck cross-coupling reactions catalyzed by (NHC)PdI2PPh3 com-
plexes (1b, 1c and 1e)
Entry
Product
10
Cat.
Con-
version
(%)
1
2
3
1b
1c
1e
98
96
89
Reaction conditions Styrene (1.5 mmol), 4-iodotoluene (1 mmol), (NHC)PdI2PPh3 complex 1b, 1c and 1e (0.01 mmol) and KOAc (2 mmol)
were added in DMF/(CH3)2CHOH (1/2) (3 ml) to the Schlenk tube in open air. Was stirred at 80 °C for 30 min
Table 9 The catalytic activity of styrene with arylchloride in the Mizoroki–Heck cross-coupling reactions catalyzed by (NHC)PdI2PPh3 com-
plexes (1b and 1c)
Entry
R
Product
Cat.
Con-
version
(%)
1
2
7
8
–COCH3
–OCH3
11
12
1a
1b
1a
1b
17
11
3
4
Reaction conditions Styrene (1.5 mmol), arylchloride (1 mmol), (NHC)PdI2PPh3 complexes (1b and 1c) (0.01 mmol) and KOAc (2 mmol) were
added in DMF/(CH3)2CHOH (1/2) (3 ml) to the Schlenk tube in open air. Was stirred at 80 °C for 18 h
we obtained from Sonogashira coupling reactions (above).
The experimental results show that the electronic efects of
the aryl bromides are efective on the conversions of cata-
lytic reactions (Tables 7, 8, 9). When electron withdraw-
ing groups (–COCH3) were used in substrates, the con-
versions of catalytic reactions are higher (Table 7). But,
when electron donating groups (–CH3, –OCH3) were used,
the conversions of catalytic reactions are less (Tables 8,
9). When the (NHC)PdI2PPh3 complexes 1a–f were com-
pared among themselves, there are very few diferences
between the conversions of catalytic reactions (Tables 7,
8, 9). We observed that the conversion in catalytic experi-
ments increased slightly while using generally bulky
(NHC)PdI2PPh3 complexes. The reason for this diference
in catalytic conversion may be the ease of the reductive
elimination in the catalytic cycle.
Second, we performed coupling reactions using sty-
rene with aryl chloride and aryl iodide substrates for the
Mizoroki–Heck cross-coupling reaction. In these experi-
ments, we used the (NHC)PdI2PPh3 complexes 1a and 1b
for chloride substrate (Table 8) and the (NHC)PdI2PPh3
complexes 1b, 1c and 1e for iodide substrate (Table 9).
As a result of these experiments, in the conversions of
the catalytic reactions that were used aryl iodides, very
high conversions were obtained in 30 min as we expected
(Table 8). In contrast, when aryl chlorides were used in the
catalytic reactions, very low conversions were obtained
at 18 h (Table 9). These results are consistent with the
literature (Siemeling et al. 2012).
1 3

Chemical Papers
Structural description of the complex 1b and 1f
Molecular structures of two cis-(NHC)PdI2PPh3 complexes
1b and 1f are shown in Figs. 1 and 2. The Pd-metal ions are
coordinated by NHC and PPh3 ligands, and two iodide atoms
in cis disposition. In the complex 1b, NHC ligand connects
to a methylbenzyl on the ortho-position, and a hydroxyethyl
via methylene bridges, while in 1f, NHC ligand connects to a
tetramethylbenzyl and a hydroxyethyl, similarly through the
methylene bridges. Coordination spheres around the Pd(II)
atoms adopt slightly distorted square-planar geometry.
PPdI2C planes are almost planar with the r.m.s deviations
of 0.054 and 0.093 Å for 1b and 1f, respectively. Pd–Ccarbene
bond lengths are 1.990(5) Å in 1b, 1.992(6) Å in 1f, are
comparable with similar cis-(NHC)PdI2PPh3 complexes in
our previous study and the study of Hahn et al. (Aktaş et al.
2019; Hahn et al. 2004). Considering bond angles around
the phosphorus atoms, both complexes have distorted tet-
rahedral environments. The NHC ligands are oriented
almost perpendicular to Pd/C/P/I/I planes with the values of
89.21(10)° for 1b, 87.06(10)° for 1f. The palladium–iodide
bond lengths trans to the carbenes are very slightly shorter
than that trans to the phosphines. In the literature, it is sug-
gested that the reason for the longer Pd–I bond distance,
which trans to the phosphine ligand is due to the fact that
the strong trans efect of phosphine (Zamora et al. 2012;
Modak et al. 2015). Thus, palladium(II) complexes bearing
both NHC and phosphine ligands usually adopt a square
planar cis-confguration due to this transphobia. Hydroxethyl
groups are almost perpendicular to the NHC ring systems
of 1b and 1f, with the C1–N1–C8–C9 torsion angles to be
103.33(2)° and 99.30(4)°, respectively. On the other hand, in
1b, the torsion angle [C1–N2–C10–C11] between the NHC
and methylbenzyl is −121.25(2)°, while this value, in 1f,
is − 166.18(9)° between the NHC and tetramethylbenzyl
fragment.
Fig. 1 Molecular structure of 1b showing the atom-labeling
scheme. Displacement ellipsoids are drawn at the 25% probability
level. Selected bond parameters (Å, °): Pd1–I1 2.6465(5), Pd1–I2
2.6681(5), Pd1–P1 2.2963(13), Pd1–C1 1.990(5), C1–N1 1.345(6),
C1–N2 1.358(6), N1–C8 1.472(7), N2–C10 1.464(6), C9–O1
1.422(9); I1–Pd1–I2 92.474(17), I1–Pd1–P1 92.03(3), I1–Pd1–C1
176.63(14), I2–Pd1–P1 174.42(4), I2–Pd1–C1 85.25(13), P1–Pd1–
C1 90.40(14), C1–N1–C8 124.9(5), N1–C8–C9 114.0(5), C8–C9–O1
108.5(6), C1–N2–C10 125.8(4), N2–C10–C11 114.4(5), Pd1–P1–
C18 115.69(17), Pd1–P1–C24 113.02(18), Pd1–P1–C30 113.60(16)
The crystal structure of complex 1b is stabilized by
C–H···N type intra-molecular interactions and Van der
Waals forces. Stacking of the molecules, viewing along
the c-axis, are shown in Fig. 3. In 1f, molecules connect
to each other via the O1–H1···I2i inter-molecular hydrogen
bonds, to form a dimeric R2(16) graph-set motif (Fig. 4)
(Etter and MacDonald 19902). In addition, intra-molecular
C–H···N type interactions and C–H···π stacking interactions
are responsible for the stabilization of the crystal structure
[C3–H3···Cg1, C3···Cg1=3.467(5) Å, C3–H3···Cg1=145°,
Cg1: C11/16; C31–H31···Cg2, C31···Cg2 = 3.525(7) Å,
C31–H31···Cg2=137°, Cg2: C2/7].
Fig. 2 Molecular structure of 1f showing the atom-labeling
scheme. Displacement ellipsoids are drawn at the 25% probability
level. Selected bond parameters (Å, °): Pd1–I1 2.6283(5), Pd1–I2
2.6433(5), Pd1–P1 2.2804(12), Pd1–C1 1.987(4), C1–N1 1.357(5),
C1–N2 1.353(5), N1–C8 1.457(6), N2–C10 1.477(5), C9–O1
1.398(6); I1–Pd1–I2 90.765(16), I1–Pd1–P1 91.57(3), I1–Pd1–C1
172.91(13), I2–Pd1–P1 176.22(4), I2–Pd1–C1 87.21(11), P1–Pd1–
C1 91.87(12), C1–N1–C8 123.6(4), N1–C8–C9 113.0(4), C8–C9–O1
111.0(5), C1–N2–C10 121.1(4), N2–C10–C11 115.3(4), Pd1–P1–
C21 114.10(17), Pd1–P1–C27 112.18(17), Pd1–P1–C33 114.81(15)
1 3

Chemical Papers
Conclusion
In conclusion, we reported the synthesis of new 2-hydrox-
yethyl substituted (NHC)PdI2PPh3 1a–f using PPh3 and
starting PEPPSI complexes. The catalytic activities of
these complexes were examined in the Sonogashira cross-
coupling and Mizoroki–Heck cross-coupling reaction. All
complexes showed excellent activity when the aryl iodide
and aryl bromide were used in these reactions. But, all
complexes showed less activity when the aryl chloride
was used in these reactions. The crystal structures of the
complexes 1b and 1f were performed using single-crys-
tal X-ray difraction technique. The results of the analy-
sis indicate that both (NHC)PdI2PPh3 complexes adopt
distorted square-planar environments around the Pd(II)
centers.
Acknowledgements The authors acknowledge Dokuz Eylul University
for the use of the Rigaku Oxford Xcalibur Eos Difractometer (pur-
chased under University Research Grant no.: 2010.KB.FEN.13). The
authors thank the Inonu University Faculty of Science Department of
Chemistry for the spectroscopy and elemental analysis characterization
of compounds.
Fig. 3 Stacking of the molecules of complex 1b, viewed along the
c-axis. The Pd metals and iodide anions are shown as balls, while the
other atoms are shown as stick drawing style. For the sake of clarity,
hydrogen atoms are omitted
Compliance with ethical standards
Conflicts of interests The authors declare that there are no conficts
of interests.
Appendix A: Supplementary data
CCDC 1897240 for 1b and 1897153 for 1f contain the sup-
plementary crystallographic data. Copies of the data can be
obtained free of charge at http://www.ccdc.cam.ac.uk/conts
/retrieving.html or from the Cambridge Crystallographic
Data Center, 12, Union Road, Cambridge CB2 1EZ, UK.
fax: (+44) 1223-336-033, e-mail: deposit@ccdc.cam.ac.uk.
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Fig. 4 Graphical representation of molecular packing within the unit
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drawing style. For the clarity, hydrogen atoms not to play role in
bonding are omitted
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