New 4-vinylbenzyl-substituted bis(NHC)-Pd(II) complexes: Synthesis, characterization and the catalytic activity in the direct arylation reaction

Article abstract of DOI:10.1016/j.ica.2017.12.019

This study contains the synthesis of the new 4-vinylbenzyl substituted bis(NHC)-Pd(II) complexes and their catalytic activity in direct arylation reaction. The bis(NHC)-Pd(II) complexes have been prepared from Ag(I)NHC complexes by transmetallation method

Full text of DOI:10.1016/j.ica.2017.12.019

Accepted Manuscript
Research paper
New 4-vinylbenzyl-substituted bis(NHC)-Pd(II) complexes: Synthesis, charac-
terization and the catalytic activity in the direct arylation reaction.
Yetkin Gök, Aydın Aktaş, Hülya Erdoğan, Yakup Sarı
PII:
S0020-1693(17)30922-2
https://doi.org/10.1016/j.ica.2017.12.019
ICA 18053
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
10 June 2017
7 December 2017
9 December 2017
Please cite this article as: Y. Gök, A. Aktaş, H. Erdoğan, Y. Sarı, New 4-vinylbenzyl-substituted bis(NHC)-Pd(II)
complexes: Synthesis, characterization and the catalytic activity in the direct arylation reaction., Inorganica Chimica
Acta (2017), doi: https://doi.org/10.1016/j.ica.2017.12.019
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

New 4-vinylbenzyl-substituted bis(NHC)-Pd(II) complexes: Synthesis,
characterization and the catalytic activity in the direct arylation reaction.
*
Yetkin Gök, Aydın Aktaş , Hülya Erdoğan, Yakup Sarı
İnönü University, Faculty of Science, Department of Chemistry 44280, Malatya, Turkey
Correspondence e-mail: aydinaktash@hotmail.com
Abstract
This study contains the synthesis of the new 4-vinylbenzyl substituted bis(NHC)-Pd(II)
complexes and their catalytic activity in direct arylation reaction. The bis(NHC)-Pd(II)
complexes have been prepared from Ag(I)NHC complexes by transmetallation method. The
1
13
complexes have been characterized by using H NMR, C NMR, FTIR spectroscopy and
elemental analysis techniques. Also, all the complexes showed excellent activity as catalysts in
the direct arylation reaction.
Keywords: N-Heterocyclic carbenes; bis(NHC)-Pd(II) complexes; Direct arylation;
Butylfuran; Butylthiophene; 2-isopropylthiazole.
Introduction
The N-heterocyclic carbenes (NHCs) are one of the most important ligands for metal-
catalyzed reactions. NHCs have had unique properties such as stability to air and moisture,
adjustability as electronically and sterically, and being strong σ-donor and weak π-acceptor [1-
7
]. Increasing the popularity of these ligands in organic and organometallic chemistry is due to
the durability of the metal-carbene bond, as well as having thermal and oxidative stability [8,
].
9
The metal-carbene complexes involving a wide variety of transition metals such as
Au(I), Cu(I), Cu(II), Ni(II), Pd(II), Pt(II), Rh(I), Rh(III), Ir(I), Ir(III), Ru(II), Ru(III), and
Ru(IV) are easily synthesized by the transmetalation method of the transfer agent Ag(I)NHC
complexes [10-12]. Also, Pd-NHC complexes are easily synthesized by this method. In recent
years, there have been numerous studies published in which Pd-NHC complexes are used as

active catalysts [13-15]. In particular, palladium-carbene complexes derived from imidazolium
and benzimidazolium salts have been successfully synthesized as highly active catalysts in a
wide variety of organic transformations including cross-coupling reactions of Suzuki,
Kumada, Hiyama, Stille, Negishi, and Sonogashira [16-19].
In recent years some outstanding studies on the direct arylation reaction (C-H activation)
of bis(NHC)-Pd(II) complexes have been published [20-24]. These studies have showed that
the bis(NHC)-Pd(II) complexes exhibit very good catalytic activity. In our study, we have
investigated the synthesis and the characterization of new bis(NHC)-Pd(II) complexes. Also,
we investigated the catalytic activities of new bis(NHC)-Pd(II) complexes in direct arylation
reactions, and they showed fairly good activity as catalysts in the direct arylation reaction.
Experimental
All synthesis involving bis(NHC)-Pd(II) complexes 1a-i were carried out under an inert
atmosphere in flame-dried glassware using standard Schlenk techniques. The solvents used
were purified by distillation over the drying agents indicated and were transferred under Ar:
Et
2
2 2 4
O (Na/K alloy), CH Cl (P O10), hexane, toluene (Na).
All other reagents were commercially available by Aldrich Chemical Co. and used
without further purification. Melting points were identified in glass capillaries under air with an
Electrothermal-9200 melting point apparatus. FT-IR spectra were saved in the range 400-4000
-1
1
13
cm on Perkin Elmer Spectrum 100 FT-IR spectrometer. Proton ( H) and Carbon ( C) NMR
spectra were recorded using either a Bruker AS 300 Merkur spectrometer operating at 300
1
13
MHz ( H), 75.47 MHz ( C) in DMSO-d
reactions were observed on an Agilent 6890 N GC system by GC-FID with an HP-5 column of
0 m length, 0,32 mm diameter and 0,25 µm film thickness. Column chromatography was
6
with tetramethylsilane as an internal reference. All
3
performed using silica gel 60 (70-230 mesh). Elemental analyses were performed by İnönü
University Scientific and Technological Research Center (Malatya, TURKEY).
Synthesis of bis[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]dichloropalladium(II),
1
a

2 2
To a solution of bis(benzonitrile)palladium(II) chloride [PdCl (PhCN) ] (100 mg. 0.26 mmol)
in dichloromethane (20 mL) was added chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-
ylidene]silver(I) (204 mg. 0.52 mmol). The reaction mixture was stirred for 24 h at room
temperature in the dark conditions. Then filtered through celite and the solvents were
evaporated under vacuum to afford the product as a light yellow solid. The crude product was
recrystallized from dichloromethane/diethyl ether (1:3) at room temperature. Yield: 85 % (145
0
-1
mg). m.p: 206-207 C; ν(CN): 1446 cm . Anal. Calc. for C34
H
22
N
4
PdCl
) δ (ppm) = 4.49 (s, 6H,
, J: 10.8 Hz); 6.22 (s, 4H, CH CH=CH );
, J: 4.5 Hz); 7.13-7.93 (m, 16H, Ar-H). C NMR (75.47 MHz,
) δ (ppm) = 34.7 (-CH ); 51.2 (-CH CH=CH ); 110.2, 111.2, 113.9, 114.2,
14.8, 123.1, 125.5, 126.0, 126.5, 126.7, 127.4, 127.7, 128.1, 128.8, 134.1, 135.3, 135.9,
36.4, 137.0, 138.3 (Ar-C and -CH=CH ); 181.5 (2-C-Pd).
2
: C: 60.59, H: 4.79, N:
1
8
.31. Found: C:60.42, H:4.89, N:8.26. H NMR (300 MHz, DMSO-d
6
CH
.65 (dd, 2H, C
DMSO-d
3
); 5.25 and 5.96 (d, 4H, CH
2
C
6
H
4
CH=CH
2
2
C
6
H
4
2
1
3
6
6
H
4
CH=CH
2
6
3
2
C
6
H
4
2
1
1
2
Synthesis of bis[1-ethyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]dichloropalladium(II),
1
b
The synthesis of 1b was carried out in the same way as that described for 1a, but chloro[1-
ethyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (210 mg. 0.52 mmol) was used
instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield: 81%
0
-1
(
148 g). m.p.: 198-200 C; ν(CN): 1443 cm . Anal. Calc. for C36
H
36
N
4
PdCl
2
C: 61.59, H: 5.17,
1
N: 7.98. Found: C: 61.48, H: 5.11, N: 8.03. H NMR (300MHz, DMSO-d
6
) δ (ppm) = 1.07 (t,
6
5
1
5
H, -CH
2
CH
3
, J: 4.2 Hz); 5.26 (m, 4H, -CH
CH=CH ); 6.25 (dd, 2H, CH
6H, Ar-H). C NMR (75.47 MHz, DMSO-d ) δ (ppm) = 15.7 (-CH
6.5 (-CH CH=CH ); 111.4, 111.9, 114.9, 115.1, 123.6, 126.6, 126.8, 128.6, 133.7, 136.2
); 181.3 (2-C-Pd).
2
CH
3
); 6.18 (s, 4H, -CH
CH=CH J: 10.2 Hz); 6.65-7.98 (m,
CH ); 51.2 (-CH CH );
2
6 4 2
C H CH=CH ); 5.15 and
.87 (m, 4H, -CH
2
C
6
H
4
2
2
C
6
H
4
2
1
3
6
2
3
2
3
2
C
6
H
4
2
and 137.1. (Ar-C and -CH=CH
2
Synthesis of bis[1-butyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]dichloropalladium(II),
1
c
The synthesis of 1c was carried out in the same way as that described for 1a, but chloro[1-
butyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (225 mg. 0.52 mmol) was used

instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield: 83%
0
-1
(
164 mg). m.p: 211-212 C; ν(CN): 1445 cm . Anal. Calc. for C40
H
44
N
4
PdCl
2
: C: 51.25, H:
) δ (ppm) =
); 2.31 (m, 4H, -
J: 6.0 Hz); 5.82 and 6.01 (m, 4H,
); 6.62 (dd, 2H, -CH CH=CH J:
) δ (ppm) = 14.3 (-
CH CH ); 51.3 (-
); 111.5, 114.8, 123.5, 123.7, 124.6, 128.7, 133.4,
); 181.6 (2-C-Pd).
1
4
0
.95, N: 5.98. Found: C: 51.28, H: 4.91, N: 5.99. H NMR (300MHz, DMSO-d
6
.70 (t, 6H, -CH
2
CH
); 5.23 (t, 4H, -CH
CH=CH ); 6.21 (s, 4H, -CH
2
CH
2
CH
3
, J: 4.5 Hz); 1.53 (m, 4H, -CH
CH CH CH
CH=CH
2
CH
2
CH CH
3
2
CH
2
2
CH
2
CH
2
CH
3
2
2
2
3
CH
C
6
H
4
2
2
C
6
H
4
2
2
C
6
H
4
2
1
3
1
0.4 Hz); 7.22-7.81 (m, 16H, Ar-H). C NMR (75.47 MHz, DMSO-d
6
CH
2
CH
2
2
CH
2
2
CH
3
); 20.3 (-CH
2
CH
2
CH
2
CH
3
); 32.4 (-CH
2
CH
2
2
3
CH
2
CH
CH
CH
3
); 55.4 (-CH
2
C
6
H
4
CH=CH
2
1
33.6, 134.4, 136.1 and 137.2 (Ar-C and -CH=CH
2
Synthesis of bis[1-(2-methoxyethyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]dichloro
palladium(II), 1d
The synthesis of 1d was carried out in the same way as that described for 1a, but chloro[1-(2-
methoxyethyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (227 mg. 0.52 mmol) was
used instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield:
0
-1
7
5
8%. (155 mg). m.p.: 221-222 C; ν(CN): 1444 cm . Anal. Calc. for C38
H
40
N
4
O
2
PdCl
2
C:
1
9.89, H: 5.29, N: 7.35. Found: C: 59.73, H: 5.22, N: 7.42. H NMR (300MHz, DMSO-d
6
) δ
(
ppm) = 3.18 (s, 6H, -CH
2
CH
J: 8.4 Hz); 5.67 and 6.31 (m, 4H, -CH
CH=CH ); 6.86 (m, 2H, -CH CH=CH ); 7.22-7.91 (m, 16H, Ar-H). C NMR
) δ (ppm) = 48.1(-CH CH OCH ); 51.9 (-CH CH OCH ); 59.2 (-
); 72.1 (-CH CH OCH ); 110.9, 111.2, 113.9, 114.1, 123.1, 126.5, 127.8,
); 181.9 (2-C-Pd).
2
OCH
3
); 5.13 (m, 4H, -CH
2
CH
2
OCH
3
); 5.29 (t, 4H, -
CH
CH
2
2
CH
2
OCH
3
2
C
6
H
4
CH=CH
2
); 6.12 (s, 4H, -
1
3
C
6
H
4
2
2
C
6
H
4
2
(
75.47 MHz, DMSO-d
6
2
2
3
2
2
3
CH
2
C
6
H
4
CH=CH
2
2
2
3
1
33.8, 135.2, 136.3, 136.4 and 137.3 (Ar-C and -CH=CH
2
Synthesis
of
bis[1-(2-ethoxyethyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]dichloro
palladium(II), 1e
The synthesis of 1e was carried out in the same way as that described for 1a, but chloro[1-(2-
ethoxyethyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (234 mg. 0.52 mmol) was
used instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield:
0
-1
8
44 4 2 2
4% (173 mg). m.p.: 229-230 C; ν(CN): 1443 cm . Anal. Calc. for C40H N O PdCl : C:

1
6
0.80, H: 5.61, N: 8.97. Found: C: 60.87, H: 5.64, N: 9.02. H NMR (300MHz, DMSO-d
ppm) = 1.16 (t, 6H, -CH CH OCH CH , J: 4.6 Hz); 3.53 (m, 4H, -CH CH OCH CH ); 4.09
CH , J: 4.4 Hz); 5.98 (m, 4H, -CH CH OCH CH ); 5.63 and 6.28 (m,
); 6.19 (s, 4H, -CH CH=CH ); 6.84 (m, 2H, -CH CH=CH );
.21-7.86 (m, 16H, Ar-H). C NMR (75.47 MHz, DMSO-d ) δ (ppm) = 15.2 (-
CH OCH CH ); 66.6 (-
); 110.9, 111.2, 113.8, 114.1, 114.2, 126.7,
); 181.9 (2-C-
6
) δ
(
(
2
2
2
3
2
2
2
3
t, 4H, -CH
2
CH
2
OCH
2
3
2
2
2
3
4
7
H, -CH
2
C
6
H
4
CH=CH
2
2
C
6
H
4
2
2
C
6
H
4
2
1
3
6
CH
2
CH
2
OCH
2
CH
3
); 48.2 (-CH
2
CH
2
OCH
2
CH
3
); 51.9 (-CH
2
2
2
3
CH
2
CH
2
OCH
2
CH
3
); 69.9 (-CH
2
C
6
H
4
CH=CH
2
1
26.9, 127.8, 130.8, 134.0, 135.2, 136.4, 137.1 and 137.3. (Ar-C and -CH=CH
2
Pd).
Synthesis
of
bis[1-benzyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]
dichloropalladium(II), 1f
The synthesis of 1f was carried out in the same way as that described for 1a, but chloro[1-
benzyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (243 mg. 0.52 mmol) was used
instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield: 82 %
0
-1
(
176 mg). m.p: 236-237 C; ν(CN): 1447 cm . Anal. Calc. for C46
H
40
N
4
PdCl
2
: C: 66.87, H:
) δ (ppm) =
6 5
C H ); 6.10 (s, 4H, -
1
4
5
.88, N: 6.78. Found: C: 66.73, H: 4.92, N: 6.75. H NMR (300 MHz, DMSO-d
6
.22 and 5.71 (d, 4H, -CH
CH=CH ); 6.62 (dd, 2H, -C
NMR (75.47 MHz, DMSO-d ) δ (ppm) = 40.4 (-CH
11.2,113.9, 114.5, 123.1, 125.5, 125.8, 126.5, 127.1, 127.7, 127.9, 128.4, 128.8, 134.5, 135.1,
35.3, 135.9, 136.4, 137.1 and 138.1 (Ar-C and -CH=CH ); 182.4 (2-C-Pd).
2
C
6
H
4
CH=CH
2
, J: 8.1 Hz); 6.01 (s, 4H, -CH
, J: 8.4 Hz); 7.08-7.72 (m, 26H, Ar-H). C
); 51.8 (-CH CH=CH );
2
1
3
CH
2
C
6
H
4
2
6
H
4
CH=CH
2
6
2
C
6
H
5
2
C
6
H
4
2
1
1
2
Synthesis
of
bis[1-(2-methylbenzyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]
dichloropalladium(II), 1g
The synthesis of 1g was carried out in the same way as that described for 1a, but chloro[1-(2-
methylbenzyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (250 mg. 0.52 mmol) was
used instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield:
0
-1
7
6% (170 mg). m.p: 265-266 C; ν(CN): 1439 cm . Anal. Calc. for C48
H
44
N
4
PdCl
2
: C: 67.49,
) δ (ppm) =
, J: 8.4 Hz); 5.88 (s, 4H,
); 6.72 (m, 2H, -CH CH=CH ); 6.95-
1
H: 5.19, N: 6.56. Found: C: 67.35, H: 5.11, N: 6.47. H NMR (300 MHz, DMSO-d
6
2
.27 (s, 6H, -CH
2
C
6
H
4
CH
3
); 5.23 and 5.69 (d, 4H, -CH
2
C
6
H
4
CH=CH
2
-
CH CH ); 6.02 (s, 4H, -CH
2
C
6
H
4
3
2
C
6
H
4
CH=CH
2
2
C
6
H
4
2

1
3
7
.51 (m, 24H, Ar-H). C NMR (75.47 MHz, DMSO-d
6 2 6 4 3
) δ (ppm) = 19.4 (-CH C H CH ); 49.5
(
-CH CH 51.9 (-CH CH=CH ); 110.9, 111.2, 113.9, 123.1, 126.4, 126.6, 127.2,
2
C
6
H
4
3
)
,
2
C
6
H
4
2
1
1
27.4, 127.9, 130.1, 133.6, 134.2, 134.7, 135.1, 135.4, 136.5 and 137.1 (Ar-C and -CH=CH
2
);
82.7. (2-C-Pd).
Synthesis of bis[1-(4-methylbenzyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]dichloro
palladium(II), 1h
The synthesis of 1h was carried out in the same way as that described for 1a, but chloro[1-(4-
methylbenzyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (250 mg. 0.52 mmol) was
used instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I). Yield:
0
-1
8
2% (182 mg). m.p: 244-245 C; ν(CN): 1436 cm . Anal. Calc. for C48
H
44
N
4
PdCl
2
: C: 67.49,
) δ (ppm) =
); 5.65 (s, 4H, -
CH=CH , J: 7.5 Hz);
) δ (ppm) = 21.2 (-CH CH );
); 111.2, 112.2, 113.9, 114.8, 123.0, 124.4,
26.6, 127.4, 127.8, 129.8, 131.7, 132.7, 133.9, 134.5, 135.9, 136.5, 137.4, 137.9 and 138.6
); 182.1 (2-C-Pd).
1
H: 5.19, N: 6.56. Found: C: 67.42, H: 5.14, N: 6.48. H NMR (300 MHz, DMSO-d
6
2
.35 (s, 6H, -CH
CH CH ); 6.05 (s, 4H, -CH
.04-7.45 (m, 24H, Ar-H). C NMR (75.47 MHz, DMSO-d
2.1 (-CH CH ); 54.0 (-CH CH=CH
2
C
6
H
4
CH
3
); 5.35 and 5.83 (m, 4H, -CH
2
C
6
H
4
CH=CH
2
2
C
6
H
4
3
2
C
6
H
4
CH=CH ); 6.71 (dd, 2H, C
2
6
H
4
2
13
7
5
1
6
2
C
6
H
4
3
2
C
6
H
4
3
2
C
6
H
4
2
(
Ar-C and -CH=CH
2
Synthesis of bis[1-(2,3,5,6-tetramethylbenzyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]
dichloropalladium(II), 1i
The synthesis of 1i was carried out in the same way as that described for 1a, but
chloro[1-(2,3,5,6-tetramethylbenzyl)-3-(4-vinylbenzyl)benzimidazol-2-ylidene]silver(I) (272
mg. 0.52 mmol) was used instead of chloro[1-methyl-3-(4-vinylbenzyl)benzimidazol-2-
0
-1
ylidene]silver(I). Yield: 83% (202 mg). m.p: 248-249 C; ν(CN): 1455 cm . Anal. Calc. for
1
C
54
H
56
N
4
PdCl
MHz, DMSO-d
Hz -C CH=CH
.86-7.55 (m, 18H, Ar-H). C NMR (75.47 MHz, DMSO-d
9.7 (-C H(CH ); 50.8 (-CH H(CH ); 51.8 (-CH
2
: C: 69.12, H: 6.02, N: 5.97. Found: C: 69.19, H: 6.06, N: 5.91. H NMR (300
6
) δ (ppm) = 2.28 and 2.39 (s, 24H, -C
); 6.37 (s, 4H, -CH H(CH ); 6.55 (dd, 2H, J: 7.2 Hz -C
) δ (ppm) = 15.3, 16.7, 20.6 and
CH=CH ); 110.7, 111.9, 113.7,
6
H(CH
3
)
4
); 5.21 and 5.67 (d, 4H, J: 7.5
6
H
4
2
2
C
6
3
)
4
6
H
4
CH=CH );
2
1
3
6
2
6
6
3
)
4
2
C
6
3
)
4
2
C
6
H
4
2

1
1
22.6, 123.0, 127.8, 131.1, 132.2, 134.2, 134.4, 134.5, 134.6, 134.8, 135.3, 135.5, 136.9 and
37.0. (Ar-C and -CH=CH ); 182.3 (2-C-Pd).
2
Table 1. Physical properties of compounds and their results of spectroscopic analysis.
(
Yield (%) m.p. C)
o
13
-1
(cm )
Compound
Formula
C 2-C-Pd (δ
181.5
)
IR: ν(CN)
1
a
C H N PdCl
2
85
81
83
78
84
82
76
82
83
206-207
198-200
211-212
221-222
229-230
1446
3
4
22
4
1
b
C H N PdCl
2
181.3
181.6
181.9
181.9
182.4
182.7
182.1
182.3
1443
1445
1444
1443
1447
1439
1436
1455
3
6
36
4
1
c
40 44 4 2
C H N PdCl
1
d
38 40 4 2 2
C H N O PdCl
1
e
40 44 4 2 2
C H N O PdCl
1
f
C H N PdCl
2
236-237
265-266
244-245
4
6
40
4
1
1
g
48 44 4 2
C H N PdCl
h
48 44 4 2
C H N PdCl
1
i
C H N PdCl
2
248-249
5
4
56
4
General Method for Direct Arylation of Furan and Thiophene With Aryl Bromides
The aryl bromide derivatives (4-bromo acetophenone, 4-bromoanisole, 4-bromotoluene
and 4-bromobenzene) (1 mmol) and heteroaryl derivatives (2-n-butylfuran, 2-n-butylthiophene
and 2-isopropylthiazole) (2 mmol), KOAc (1 mmol) and bis(NHC)-Pd(II) complexes 1a-i
(
0.003 mmol) were dissolved in N,N-dimethylacetamide (DMAc) (2 mL) in a small Schlenk
tube under argon as described in the literature [23]. The reaction mixture was stirred in an oil
0
bath at 130 C for 1 hour. Then was cooled to room temperature and the solvent was removed
under vacuum. The obtained residue was purified by column chromatography (silica gel 60–
1
20 mesh) by using diethyl ether/n-hexane (1:5) as eluent to afford the pure product. The purity
of the compounds was checked by gas chromatography (GC) and gas chromatography-mass
spectrometry (GC-MS). Conversions were calculated by taking into account the conversion of
aryl bromides to products.
Results and Discussion

Synthesis of Bis(NHC)-Pd(II) Parent Complexes. (1a-i)
The parent 4-vinylbenzyl substituted bis(NHC)-Pd(II) complexes described in this work
have been seen in Scheme 1. The new bis(NHC)-Pd(II) complexes 1a-i were prepared from the
synthesized Ag(I)NHC complexes via transmetallation method. The new bis(NHC)-Pd(II)
complexes 1a-i were prepared by mixing chloro[1-alkyl(or aryl)-3-(4-vinylbenzyl)
2 2
benzimidazol-2-ylidene]silver(I) with 0.5 equivalents of [PdCl (PhCN) ] in dichloromethane
(
20 mL). Then the reaction mixture was stirred at room temperature for 24 h. in dark condition.
The new bis(NHC)-Pd(II) complexes were obtained as a light yellow solid in 76 % to 85 %
yield. The air and moisture stable the new bis(NHC)-Pd(II) complexes were soluble in solvents
such as toluene, dichloromethane, and chloroform. The formations of the nonsymmetrical
1
13
substituted complexes were confirmed by FT-IR, H NMR and C NMR spectroscopic
methods and elemental analysis techniques. These spectra are consistent with the proposed
1
3
formula. In the C NMR spectra, the Pd-Ccarbene resonances of these new bis(NHC)-Pd(II)
1
3
complexes in the C NMR spectra appeared highly downfield shifted at δ 181.5, 181.3, 181.6,
1
81.9, 181.9, 182.4, 182.7, 182.1 and 182.3 ppm for 1a-i, respectively. The results of the
elemental analysis, which is one of the analytical techniques used to prove the synthesis of
compounds, were evaluated and it was observed that the calculated values were very close to
the found values. The FT-IR data clearly indicated the presence of ν(CN) at 1446, 1443, 1445,
-1
1
444, 1443, 1447, 1439, 1436 and 1455 cm for the new bis(NHC)-Pd(II) complexes (1a–i),
respectively.

N
N
[PdCl (PhCN) ]
N
Ag O
2
2
2
Cl
2
AgCl
PdCl2
2
o
DCM
DCM, 25 C, 24 h
2
N
R
N
R
N
R
o
2
5 C, 24 h
1
O
O
,
R:
CH3 ,
C H ,
,
,
2
5
a
b
c
d
e
,
,
,
,
f
g
h
i
Scheme 1. Synthesis of 4-vinylbenzyl substituted bis(NHC)-Pd(II) Complexes 1a-i.
Direct Arylation of 2-n-butylfuran, 2-n-butylthiophene and 2-isopropylthiazole with
Various Aryl Bromides
Table 2. Bis(NHC)-Pd(II) complexes (1a-i) catalysed direct arylation of 2-n-butylfuran by
using aryl bromides.
Bis(NHC)-Pd(II) complexes (1a-i)
(
0.003mmol)
+
R
Br
R
DMAc (2 ml), KOAc (1mmol)
O
O
o
1
30 C, 1 h
Entry
Ar-Br
Pd(II)NHC
Product
% Conv.
1
2
1a
1b
94
96

3
4
5
6
7
8
9
1c
1d
1e
1f
93
95
99
96
98
96
99
80
74
75
79
88
84
79
87
89
82
81
85
O
O
Br
O
2
1g
1h
1i
1
0
1
2
3
4
5
6
7
8
9
0
1
1a
1b
1c
1d
1e
1f
1
1
1
1
1
1
1
1
1
2
2
O
Br
O
O
3
1g
1h
1i
1a
1b
1c

2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
1d
1e
1f
82
92
91
88
90
89
96
98
95
96
96
97
91
95
93
Br
O
4
1g
1h
1i
1a
1b
1c
1d
1e
1f
Br
O
5
1g
1h
1i
Reaction conditions: 2-n-butylfuran (2 mmol), aryl bromide (1 mmol), bis(NHC)-Pd(II) complexes (1a-i) (0.003
o
mmol), KOAc (1 mmol), DMAc (2 mL), 130 C, 1 h, product purity was checked by GC and NMR, conversions
were calculated according to aryl bromide.
Table 3. Bis(NHC)-Pd(II) complexes (1a-i) catalysed direct arylation of 2-n-butylthiophene
by using aryl bromides.

Bis(NHC)-Pd(II) complexes (1a-i)
0.003mmol)
(
+
R
Br
R
DMAc (2 ml), KOAc (1mmol)
S
S
o
1
30 C, 1 h
Entry
Ar-Br
Pd(II)NHC
Product
% Conv.
96
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
96
94
97
O
O
95
Br
S
96
6
1g
1h
1i
98
96
98
1
1
1
1
1
1
1
0
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
79
74
72
77
85
O
Br
O
S
71
7
1g
79

1
1
1
2
2
2
2
2
2
2
2
7
8
9
0
1
2
3
4
5
6
7
1h
1i
69
75
88
87
90
92
94
87
91
89
90
1a
1b
1c
1d
1e
1f
Br
S
8
1g
1h
1i
2
8
1a
97
2
3
3
3
3
3
3
9
0
1
2
3
4
5
1b
1c
1d
1e
1f
95
93
96
98
95
94
97
Br
S
9
1g
1h

3
6
1i
93
Reaction conditions: 2-n-butylthiophene (2 mmol), aryl bromide (1 mmol), bis(NHC)-Pd(II) (1a-i) (0.003
o
mmol), KOAc (1 mmol), DMAc (2 mL), 130 C, 1 h, product purity was checked by GC and NMR, conversions
were calculated according to aryl bromide.
Table 4. Bis(NHC)-Pd(II) complexes (1a-i) catalysed direct arylation of 2-isopropylthiazole
by using aryl bromides.
Bis(NHC)-Pd(II) complexes (1f-i)
0.003mmol)
N
N
(
+
R
Br
i-pr
i-pr
DMAc (2 ml), KOAc (1mmol)
S
S
R
o
1
30 C, 1 h
Entry
Ar-Br
Pd(II)NHC
Product
% Conv.
1
2
3
4
1f
1g
1h
1i
96
99
99
99
O
N
Br
i-pr
O
S
1
0
5
6
7
8
1f
1g
1h
1i
90
87
92
83
N
O
Br
i-pr
S
O
1
1
9
1f
1g
1h
94
91
96
N
1
1
0
1
Br
i-pr
S

1
1
1
1
1
2
3
4
5
6
1i
1f
12
92
93
N
1g
1h
1i
91
96
95
Br
i-pr
S
1
3
Reaction conditions: 2-isopropylthiazole (2 mmol), aryl bromide (1 mmol), bis(NHC)-Pd(II) (1f-i) (0.003
o
mmol), KOAc (1 mmol), DMAc (2 mL), 130 C, 1 h, product purity was checked by GC, conversions were
calculated according to aryl bromide.
We performed some experiments for the parameters of direct arylation reaction of para-
substituted aryl bromides with 2-n-butylfuran, 2-n-butylthiophene and 2-isopropylthiazole (for
1
f-i) in the presence of 1a-i as catalyst.
Conversions of the products for 2-n-butylfuran are between 74% and 99%, for 2-n-
butylthiophene are between 71% and 98%, and for 2-isopropylthiazole are between 83% and
9% (Table 2-4). When 4-bromoacetophenone was used, the best conversion was obtained.
9
However, when we used 4-bromoanisole, it was obtained at fewer conversion (Table 2-4).
Initially, we investigated the binding of 2-n-butylfuran with 4-bromoacetophenone, 4-
bromoanisole, 4-bromotoluene and 4-bromobenzene by using complexes 1a-i as catalyst.
When the effects of 1a-i in the formation of the products 2-5 were analysed, conversions of
9
3–99%, 74–89%, 81–92% and 91–98% were observed respectively (Table 2). The use of 4-
bromoacetophenone with 2-n-butylfuran gave the desired coupling product for different
complexes (1e, 1g and 1i) as catalysts in better excellent conversion than the others, such as
9
4
9%, 98% and 99%, respectively (Table 2). When 4-bromoacetophenone, 4-bromotoluene and
-bromobenzene with 2-n-butylfuran were utilized in the direct arylation reaction, conversions
of the products (2, 4 and 5) were obtained and observed to be better than the product 3 (Table
). Then, we investigated the binding of 2-n-butylthiophene with 4-bromoacetophenone, 4-
bromoanisole, 4-bromotoluene and 4-bromobenzene with complexes 1a-i as the catalyst.
2

When the effects of 1a-i in the formation of products 6-9 were analyzed, conversions of 94–
8%, 71–85%, 87–94% and 93–98% were observed respectively (Table 3). The use of 4-
9
bromoacetophenone with 2-n-butylthiophene gave the desired coupling product for different
complexes (1g and 1i) as catalysts in better excellent conversion than the others, such as 98%
and 98%, respectively (Table 3). The 2-n-butylthiophene was bound with 4-bromoanisole to
give the arylated products 7 in fewer conversions. When 4-bromoacetophenone, 4-
bromotoluene and 4-bromobenzene with 2-n-butylthiophene were utilized in the direct
arylation reaction, conversions of the products (6, 8 and 9) were obtained and observed to be
better than the product 7 (Table 3). Finally, we investigated the binding of 2-isopropylthiazole
with 4-bromoacetophenone, 4-bromoanisole, 4-bromotoluene and 4-bromobenzene with
complexes 1f-i as the catalyst. When the effects of 1f-i in the formation of products 10-13
were analyzed, conversions of 96–99%, 83–92%, 91–96% and 91–96% were observed
respectively (Table 4). The use of 4-bromoacetophenone with 2-isopropylthiazole gave the
desired coupling product for different complexes (1g, 1h and 1i) as catalysts in better excellent
conversion than the others, such as 99%, 99% and 99%, respectively (Table 4). When 4-
bromoacetophenone, 4-bromotoluene and 4-bromobenzene with 2-isopropylthiazole were
utilized in the direct arylation reaction, conversions of the products (10, 12 and 13) were
obtained and observed to be better than the product 11 (Table 4). The 2-isopropylthiazole was
bound with 4-bromoanisole to give the arylated products 11 in fewer conversions (Table 4).
When compared to similar studies [25, 26] published recently, bis(NHC)-Pd(II) complexes
that we have synthesized to have appeared highly active catalysts. Also, as compared to the
bis(NHC)-Pd(II) complexes 1a-e containing aliphatic substituents, when the bis(NHC)-Pd(II)
complexes 1f-i containing aromatic substituents are used, the conversion is somewhat more
efficient (Table 2-4).
Conclusions
Consequently, our study is containing the synthesis of the new 4-vinylbenzyl substituted
bis(NHC)-Pd(II) complexes 1a-i. The bis(NHC)-Pd(II) 1a-i complexes were prepared from the
Ag(I)NHC complexes via transmetallation route. The catalytic effects of this new 4-
vinylbenzyl substituted bis(NHC)-Pd(II) complexes have been investigated that they are more
efficient and stable catalysts for the direct arylation reactions of 2-n-butylfuran 2-n-
butylthiophene and 2-isopropylthiazole with aryl bromide.

Acknowledgment
This work was financially supported by Inönü University Research Fund (IUBAP
012/02) and the authors acknowledge İnönü University Scientific and Technology Center for
2
the elemental analyses of the compounds.
References
[
[
[
[
[
1] K. Öfele, J. Organomet. Chem. 12 (1968) 42.
2] H.-W Wanzlick, H.-J. Schönherr Angew. Chem. Int. Ed. Engl. 7 (1968) 141.
3] L. Faraji, K. Jadidi, B. Notash, Tetrahedron Lett. 55 (2014) 346.
4] N.M. Scott, S.P. Nolan, Eur. J. Inorg. Chem. 2005 (2005) 1815.
5] A.C. Hillier, G.A. Grasa, M.S. Viciu, H.M. Lee, C. Yang, S.P. Nolan, J. Organomet.
Chem. 653 (2002) 69.
[
6] R. Dorta, E.D. Stevens, N.M. Scott, C. Costabile, L. Cavallo, C.D. Hoff, S.P. Nolan, J.
Am. Chem. Soc. 127 (2005) 2485.
[
[
[
[
[
7] T. Weskamp, V.P.W. Böhm, W.A. Herrmann, J. Organomet. Chem. 600 (2000) 12.
8] O. Schuster, L. R. Yang, G. Raubenheimer, M. Albrecht, Chem. Rev. 109 (2009) 3445.
9] G. C. Fortman, S. P. Nolan, Chem. Soc. Rev. 40 (2011) 5151.
10] P. L. Arnold, Heteroat. Chem. 13 (2002) 534.
11] I. J. B. Lin, C. S. Vasam, Comments Inorg. Chem. 25 (2004) 75.
[
[
12] J C. Garrison, W J. Youngs, Chem. Rev. 105 (2005) 3978.
13] S. Akkoç, I.Ö. İlhan, Y. Gök, V. Kayser, Inorganica Chimica Acta 461 (2017) 52.
[
14] S. Akkoç, Y. Gök, I.Ö. İlhan, V. Kayser, Beilstein Journal of Organic Chemistry 12
(
2016) 81.
[
15] A. Aktaş, S. Akkoç, Y. Gök, Journal of Coordination Chemistry 66 (2013) 2901.

[
[
[
[
[
[
16] H. D. Velazquez, F. Verpoort, Chem. Soc. Rev. 41 (2012) 7032.
17] X. Bugaut, F. Glorius, Chem. Soc. Rev. 41 (2012) 3511.
18] G. C. Fortman, S. P. Nolan, Chem. Soc. Rev. 40 (2011) 5151.
19] S. Díez-González, N. Marion, S. P. Nolan, Chem. Rev. 109 (2009) 3612.
20] S. Akkoç, Y. Gök, Applied Organometallic Chemistry 28 (2014) 854.
21] İ. Özdemir, N. Gürbüz, N. Kaloğlu, Ö. Doğan, M. Kaloğlu, Christian Bruneau and Henri
Doucet. Beilstein J. Org. Chem. 9 (2013) 303.
[
[
[
22] S. Akkoç, Y. Gök, M. Akkurt, M.N. Tahir, Inorganica Chimica Acta 413 (2014) 221.
23] İ. Özdemir, Y. Gök, Ö. Özeroğlu, M. Kaloğlu, H. Doucet, C Bruneau, 2010 (2010) 1798.
24] Y. Gaoa, W. Zhua, L. Yina, B. Donga, J. Fua, Z. Yea, F. Xueb, C. Jianga, Tetrahedron
Letters 58 (2017) 2213.
[
[
25] S. Akkoç, Y. Gök, Inorganica Chimica Acta 429 (2015) 34.
26] M. Kaloğlu, İ. Özdemir, V. Dorcet, C. Bruneau, H. Doucet, Eur J Inorg Chem 2017
(
2017) 1382.

Highlight
1
2
3
. The bis(NHC)PdCl
2
complexes have been prepared from the 4-vinylbenzyl substituted
Ag(I)NHC complexes via transmetallation method.
1
13
2
. The bis(NHC)PdCl complexes have been characterized by using H NMR, C NMR, FTIR
spectroscopy and elemental analysis techniques.
2
. The bis(NHC)PdCl complexes have been examined as catalysts in the direct arylation
reactions with 2-n-butylfuran, 2-n-butylthiophene and 2-isopropylthiazole, and have
demonstrated excellent activity in these reactions.

Graphical Abstract
R
Br
+
E
R
E
bis-NHC-Pd(II)
This study contains the synthesis of the new 4-vinylbenzyl substituted bis(NHC)-Pd(II)
complexes and their catalytic activity in direct arylation reaction. The bis(NHC)-Pd(II)
complexes have been prepared from Ag(I)NHC complexes by transmetallation method. The
1
13
complexes have been characterized by using H NMR, C NMR, FTIR spectroscopy and
elemental analysis techniques. Also, all the complexes showed excellent activity as catalysts in
the direct arylation reaction.