The imidazo{[4,5-f][1,10]-phenanthrolin}l-2-ylidene and its palladium complexes: Synthesis, characterization, and application in C-C cross-coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2016.11.013

1,3-dibutyl-1H-imidazo[4,5-f][1,10]phenanthrolinium iodide, L₅.2HI ligand and their mono-, di-, tri-, tetra-nuclear palladium(II) complexes (5.HPF₆, 6–8) were synthesized and characterized by elemental analysis, FTIR, UV–visible and

Full text of DOI:10.1016/j.jorganchem.2016.11.013

Journal of Organometallic Chemistry 827 (2017) 96e104
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The imidazo{[4,5-f][1,10]-phenanthrolin}l-2-ylidene and its palladium
complexes: Synthesis, characterization, and application in C-C
cross-coupling reactions
a
a
b
a
a, *
€
Lütfiye Gok , Salih Günnaz , Zarife Sibel S¸ ahin , Levent Pelit , Hayati Türkmen
a Department of Chemistry, Ege University, 35100 Bornova, Izmir, Turkey
b Department of Energy Systems Engineering, Faculty of Engineering and Architecture, Sinop University, Sinop, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
1,3-dibutyl-1H-imidazo[4,5-f][1,10]phenanthrolinium iodide, L5.2HI ligand and their mono-, di-, tri-,
tetra-nuclear palladium(II) complexes (5.HPF6, 6e8) were synthesized and characterized by elemental
analysis, FTIR, UVevisible and NMR spectroscopy. In addition, the complexes (5.HPF6, 6e8) were
determined by mass spectrometry (MALDI). The ligand L5.2HI was determined by X-ray diffraction. The
complexes (5.HPF6, 6e8) were tested in Suzuki-Miyaura and Mizoroki-Heck reactions at elevated tem-
peratures. The activities of the catalysts were monitored by NMR and GC analysis. We found that the
poly-nuclear complexes display better activities compared to the mono-nuclear derivatives, thus pro-
posing that an increase in metal moieties which leads to an increase in activity in cross-coupling
reaction.
Received 12 October 2016
Received in revised form
3 November 2016
Accepted 4 November 2016
Available online 5 November 2016
Keywords:
Imidazo{[4,5-f][1,10]-phenanthrolin}l-2-
ylidene
Palladium
© 2016 Elsevier B.V. All rights reserved.
Suzuki-Miyaura coupling
Mizoroki-Heck coupling
1. Introduction
in the Suzuki-Miyaura(SM), KumadaeTamaoeCorriu (KTC) and
Mizoroki-Heck(MH) cross-coupling reactions [8]. On the other
Transition metal N-heterocyclic carbene (NHC) complexes were
documented in 1968 [1]. But the isolation of the first stable NHC
was discovered by Arduengo in 1991 [2]. Since that time, their
derivatives and complexes have been comprehensively explored
[3]. Many theoretical and experimental studies have been focused
hand, the transition metal complexes of 1,10-phenanthroline
showed interesting catalytic properties in C-heteroatom coupling
reactions [9] and CeC bond formation reactions such as fluo-
roalkylation [10], direct arylation of heterocycles [11], and decar-
boxylation reactions [12]. Chen et al. have reported that 1-butyl-3-
(1,10-phenanthrolin-2-yl)imidazolylidene as a pincer NNC ligand
forms nikel and palladium complexes which exhibit good activity
in the Sonogashira and KTC coupling reactions [13]. Most recently,
we synthesized a series of ruthenium complexes bearing 1-alkyl-
imidazo[4,5-f][1,10]-phenanthroline and the catalytic activity of
complexes for the hydrogen transfer reaction of ketones was
examined [14].
on s-donation and p-accepting properties of NHCs [4]. These have
been achieved by variation of both the groups attached to the ni-
trogen atoms and the backbone structure on imidazole ring. The
latter approach includes variations in ring size and the backbone
topology by attaching functional groups or heteroatoms into the
backbone. Annulation and carbonylation of NHC decrease the
donation and increase -accepting abilities [5]. Heinicke et al. have
observed that the extension of the system of NHCs by annulation
increases their accepting ability [6]. We found that the less
intensively studied ylidenes derived benzimidazolium or other
s-
p
p
The imidazo{[4,5-f][1,10]-phenanthroline}linium ligands having
large p-conjugated electron systems were prepared [15]. Their di-
p
p-
nuclear complexes were synthesized and investigated in photo-
physical properties [15a], visible-light induced hydrogen-evolving
systems [15b], electrochemical properties [15c], photocatalytic
hydrogen formation [15d], Prolonged Excited-State Lifetimes [15e],
spectroscopic studies [15f]. It is known that polyaromatic linker
extended arylimidazolium salts behave differently [7]. We also re-
ported synthesis of Palladium(II) complexes containing piper-
idoimidazolin-2-ylidene and their catalytic properties were studied
ligands can support catalytic reaction due to their
pep stacking
capability between substrates and ligands [16]. However, the
* Corresponding author. Tel.: þ90 2323111713; fax: þ90 2323888264.
E-mail address: hayatiturkmen@hotmail.com (H. Türkmen).
http://dx.doi.org/10.1016/j.jorganchem.2016.11.013
0022-328X/© 2016 Elsevier B.V. All rights reserved.

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
97
mono-Pd(II) complexes bearing imidazo{ [4,5-f] [1,10]-phenan-
throlin}l-2-ylidene and its derivatives were not studied in detail.
We now report the palladium complexes of the 1,10-
phenanthroline annulated NHCs and their catalytic application to
Suzuki-Miyaura, Mizoroki-Heck cross-coupling reactions.
according to the literature [14]. The reaction of 1-butyl-imidazo
[4,5-f][1,10]-phenanthroline derivative (L4) with excess butyl io-
dides gave 1,3-dibutyl-1H-imidazo[4,5-f][1,10]phenanthrolinium
iodide (L5.2HI) (Scheme 1). Because of solvating problems of L5.2HI,
an anion exchange was performed replacing the iode ions with
hexafluorophospate (PFꢀ6 ) ions and L5.HPF6 salt was prepared. The
1,3-dibutyl-1H-imidazo[4,5-f][1,10]phenanthroline-2-ylidene (L5)
have large conjugated electron system and they can serve as co-
chelating and co-sensitizing ligand. Ligands have been isolated as
colourful and air stable solids. The 1H and 13C resonance for L5.2HI
moiety NCHN were detected at 9.89 and 150.5 ppm. In the case of
the anion effect, the resonance for the proton on the imidazole ring
2. Results and discussion
2.1. Synthesis, characterization of ligands and their complexes
Phenanthroline (phen) used as a ligand in coordination chem-
istry forms strong complexes with most metal ions [17]. Starting
from phenanthroline (L1), their derivatives (L2-4) were synthesized
in L5.2HI with iodide as an anion (d 9.89 ppm) shifts downfield
Scheme 1. (i) H2SO4, KBrO3, 25 ꢁC; (ii)AcOH, NH4OAC, HCHO, 120 ꢁC; (iii) (CH3)COCH3, KOH, BuI, 80 ꢁC; (iv) BuI, 140 ꢁC; (v) CH2Cl2, PdCl2(MeCN)2, 25 ꢁC.
Fig. 1. The molecular structure of L5.2HI showing the atom numbering scheme.

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
98
compared to that for the L5.HPF6 with PF6
(d
10.17 ppm). To learn
(d 150.4, 154.5 and 171.9 ppm, respectively). Crystallization at-
solvating problem of L5.2HI, the salt was crystallized beautifully out
of an acetonitrile solution using Et2O diffusion, and the structure
was confirmed by single-crystal X-ray diffraction. The molecular
structure of L5.2HI was depicted in Fig. 1. The molecule was entirely
flat and its bond lengths and angles were comparable to those in
related carbene precursors (see Fig. 2).
In order to evaluate the differences between the mono- and
poly-metallic complexes, monometallic complexes (1e4) were
prepared and characterized by spectroscopic methods. But mono-
metallic complexes 1 and 2 have been known in literature [18a,b].
The reaction of L5.HPF6 with PdCl2(MeCN)2 in CH2Cl2 gave 5.HPF6
complex (Scheme 2). For the synthesis of tri- (6) and tetra-nuclear
(7) Pd(II) complexes, 5.HPF6, Pd(OAc)2 and NaBr were used in
different proportions. Pyridine-derived PEPPSI (Pyridine Enhanced
Precatalysts Preparation, Stabilization and Initiation) type Pd(II)
complex (8) was synthesized from cleavage reaction of dimeric Pd
complex (7) with pyridine [19].
tempts were unsuccessful with the mono- and poly-metallic
complexes.
The IR spectra of ligands and complexes showed many bands of
varying intensities within 4000-400 cmꢀ1. The assignment of each
individual band to a specific vibration has not been attempted. The
presence of the eC]N- group in complexes was verified with ʋ
(C]N) vibrations between 1561 and 1407 cmꢀ1
.
The electronic spectra of the salts L5.2HI, 1.PF6, the mono-
metallic complexes (1e4, 5.HPF6) and polymetallic complexes
(6e8) in dimethyl sulfoxide at room temperature showed medium-
intensity bands around 406-383 nm range due to metal to-ligand
charge transfer transitions (MLCT) and intense n-p*, p-p* ligand-
centred transitions bands with maxima in the 358-224 nm range.
The molecular structure of L5.2HI with the atom numbering
scheme is shown in Fig. 1. Molecules of L5.2HI are linked into sheets
by a combination of OeH/I hydrogen bonds and
p … p in-
teractions. The details of these interactions are given in Supple-
mentary material.
Reverse solubility ordering of complexes (5.HPF6, 6e8) in
acetone or chlorinated solvents were observed 7 < 6 < 5.HPF6 < 8
(mg/L). The complex 5.HPF6 can be also soluble in aqueous solu-
tion. All complexes are stable toward air and moisture. The new
complexes were characterized by elemental analysis and spectro-
2.2. Electrochemistry
The electrochemical behaviors of the Pd complexes were
investigated by cyclic voltammetry. Fig. 3 shows the cyclic vol-
tammograms of 1.0 ꢂ 10ꢀ3 M of Pd-complexes recorded at a plat-
inum electrode. Responses of the complexes were qualitatively
similar except 5.HPF6. The cyclic voltammogram of 5.HPF6 dis-
played two irreversible oxidation peaks at ꢀ1.14 V and þ0.56 V and
a quasi-reversible reduction peaks at ꢀ0.60 V. The irreversible
oxidation peak at þ0.56 V can be attributed to the oxidation of
Pd(II) to Pd(IV). The quasi-irreversible reduction peak at ꢀ0.60 V
scopic methods. 1H NMR signal of the NCHN of 5.HPF6
(d
10.23 ppm) was observed to shift slightly to lower field as
compared to its signal in the 5.HPF6 salt (
d
10.17 ppm). The 31P NMR
spectrum for complex 5.HPF6 in deuterated DMSO (ꢀ144.3 ppm)
remains unchanged for up to one month.
In the polymetallic complexes (6e8), the coordination of the
NHC ligands to the palladium is confirmed by the appearance of
a downfield shifted in the 13C NMR spectra for the carbenic carbon
Fig. 2. The OeH/I, NeH/O and CeH/O hydrogen bonds of L5.2HI.
Scheme 2. (vi) Pd(OAc)2, DMSO, NaBr, 80 ꢁC; (vii) Pd(OAc)2, DMSO, NaBr, 80 ꢁC; (viii) Pyridine, CH2Cl2, 25 ꢁC.

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
99
2.3. Catalytic activity
Peris at al. were prepared di- and tri-metallic complexes with
polyaromaticeNHC-based ligands, and observed that the use of
these complexes as catalysts enhanced catalytic activity
compared to that offered by the related monometallic analogues
[16]. This catalytic enhancement may be a catalytic cooperativity
between the metals and a consequence of the
pep interaction
between the substrate and the ligands. In their other study, a
series of mono- and dimetallic complexes of palladium with N-
methyleneepyrene substituents were described and proved that
their activity in the SuzukieMiyaura C-C coupling was highly
influenced by the presence of
p-stacking additives (pyrene and
anthracene) in the reaction media [16c]. Transition metal-
catalyzed coupling reactions are extremely powerful tools for
carbon-carbon bond formation and have been widely utilized in a
great number of syntheses. In particular, palladium-catalyzed C-C
cross coupling reactions (Mizoroki-Heck, Suzuki-Miyaura, and
Stille) have become classical vehicles to occur various carbon-
carbon bonds.
Fig. 3. Cyclic voltammogram of the complexes (5.HPF6, 6e8).
was attributed to Pd(II) to Pd(0). The irreversible oxidation peak
at ꢀ1.14 can be attributed the oxidation of electrochemically
reduced imidazolium group [20]. On the other hand, the complex 6
The activities of mono-metallic complexes (1e4, 5.HPF6) and
poly-metallic complexes (6e8) toward the Suzuki-Miyaura
coupling reactions of chloroacetophenone with phenyl boronic
acid in the presences of Cs2CO3 as base in DMF-H2O mixture (1:1,
4 mL) yielding the corresponding biphenyl products are given in
Fig. 4. In order to evaluate the differences between the mono-, di-
displayed two quasi-reversible reduction peaks at ꢀ0.91
V
and þ0.20 V respectively. Similarly, complex 7 and 8 displayed two
quasi-reversible reduction peaks at ꢀ0.69, þ0.26
V
and ꢀ0.73, þ0.38 V respectively. In the same manner, the first
quasi-reversible peaks about 0.3 V can be attributed to the reduc-
tion of Pd(IV) to Pd(II) and the second irreversible peaks
about ꢀ0.7 V can be attributed to the reduction of Pd(II) to Pd(0) of
complex 7 and 8 respectively.
tri-and tetra-metallic complexes, we applied
a low catalyst
loading at 100 ꢁC, 1.5 h.
The mol% of palladium was an important parameter to keep
constant catalytic reaction while carrying out reactions of 1 mol%
mono-nuclear complex (1e4, 5.HPF6), 0.5 mol% di-nuclear complex
(8), 0.33 mol% for tri-nuclear complex (6) and 0.25 mol% tetra-
nuclear complex (7). In the course of the SuzukiꢀMiyaura
coupling reaction, black particles appear, which suggest that cata-
lysts (5.HPF6, 6e8) are probably precursors to a catalytically active
complex which is formed during the reaction. A direct comparision
between mono-metallic (1e4, 5.HPF6) and poly-metallic com-
plexes (6e8) was performed by GC analysis, which revealed nearly
identical catalytic behavior for complexes. The poly-metallic cata-
lysts are often substantially more efficient than a monometallic
The ease in reduction of Pd(IV) to Pd(II) in complexes was
investigated and was sorted as 8 > 7 > 6 > 5HPF6. The reduction
potential of the complex is related to the charge density on metal.
Thus, stronger electron-donor ligands will form Pd complexes with
a smaller positive charge density on the metal [21]. As a result, the
reduction potential will shift to more positive potential values.
Therefore, the complex 8 bearing electron-donating pyridine group
has the smallest positive charge density and the highest catalytic
activity.
Fig. 4. The SuzukieMiyaura reaction of 4-chloroacetophenone (1.0 mmol),and phenylboronic acid(1.5 mmol), Cs2CO3 (2.0 mmol), 1 mol % Pd., solvent DMF- H2O (1:1, 4 mL), 100 ꢁC,
90 min.

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
100
Table 1
shows a significantly higher activity compared to dimer complex 7.
Tri-nuclear complex 6 showed no difference in activity compared to
the mono-nuclear complex 5.HPF6.
Selected UVevisible, IR and NMR spectroscopic data.
Entry
Complex
IR (
n
-cmꢀ1
)
UVevisible (nm)
dCcarbene (ppm)
We explored the effectiveness of catalyst 8 on other aryl bro-
mides (Table 6). The catalyst 8 gave good results when electron-
donating (OMe, Me) and electron withdrawing (NO2, CHO) sub-
stituents were present at the para-position of the arylbromide. It
should be noted that in all cases only the trans products were
selectively obtained as confirmed by 1H NMR.
In an additional series of experiments we also studied the
coupling reactions between aryl bromides and n-butyl acrylate. A
methodology similar to that described for styrene was also
employed for this purpose. Again, activated aryl bromides (4-
1
2
3
4
5
6
7
8
9
L5.2HI
L5.HPF6
1
2
3
4
1580, 1408, 842
1561, 1411, 842
1580, 1423, 840
1573, 1424, 817
1537, 1445, 807
1525, 1403, 804
1530, 1416, 828
1560, 1408, 750
1550, 1407, 802
1515, 1407, 847
359, 285, 265, 236
383, 334, 291, 224
330, 305, 230, 205
385, 370, 320, 230
390, 355, 330, 305
405, 370, 345, 330
413, 374, 301, 245
401, 351, 304, 268
396, 347, 300, 257,
406, 358, 307, 262
e
e
e
e
e
e
5.HPF6
e
6
7
8
171.9
150.4
154.5
10
bromoacetophenone,
4-bromonitrobenzene,
4-
catalyst of similar structure with the increase in catalyst perfor-
mance attributed to “cooperative” interactions between the two
metals and the substrate of the reaction [22]. The highest catalytic
activity was observed with complex 8 bearing pyridine. Recently,
Pd(NHC) complexes with PEPPSI have been used in the Suzuki-
Miyaura coupling reaction with high activities [19,23]. Control
experiment indicated that the coupling reaction did not occur in
the absence of the complex. In order to improve the reactivity of
our catalytic system, we firstly started to examine the influence of
solvent. Among the various solvents explored; IPA, DMF, H2O, DMF-
H2O, the best result were obtained with DMF-H2O mixture (1:1,
4 mL). Catalyst 8 demonstrated very low activity with NaOH and
KOH (Table 3). Na2CO3 was somewhat more effective than K3PO4.
We also performed an additional experiment with mercury to
assess whether the reaction system is homogeneous or heteroge-
neous. The suppression of catalysis by Hg(0) is evidence for a het-
erogeneous catalyst [24]. It was found that the our system was
homogenous by Hg(0) which did not influence suppression of the
catalysis (Entry 9) (see Table 1).
After a brief catalyst 8 optimization study, the initial substrate
range to 8 was tested in the cross-coupling of a number of aryl
chloride substrate from reactive (electron-deficient) to unreactive
(electron rich) with phenyl boronic acid (Table 4). This conditions
allowed for the coupling of unactivated (entries 3, 4, 6), activated
(entries1, 2, 5, 7) aryl chlorides in short reaction times.
The coupling of 4-bromoacetophenone with styrene (in DMF at
100 ꢁC, Na2CO3 as base) was used as the model reaction in order to
highlight the influence of complexes (5.HPF6, 6e8) on the catalytic
activity. As shown in Table 5, the complex 8 bearing the pyridine
bromobenzaldhyde) provide the corresponding cinnamic esters in
plausible yields (35e69%), while 4-bromoanisole yields 29% of the
desired product. 4-bromotoluene gave lower yield; 22% in the
presence of 0.33 mol % catalyst.
Both catalytic reactions indicate that the presence of the
dimetallic structure in the catalyst introduces some benefits to the
catalytic outcomes of the reactions. This study reveals several
important implications regarding the influence of metal-metal in-
teractions and ligand-substrate interactions in the performance of
the catalysts used. Comparison of our results with those based on
the use of monometallic complexes in other reaction systems show
the advantages of the present method [25a,b].
3. Conclusion
In this work, the preparation and characterization of Pd(II)
complexes containing imidazo{ [4,5-f] [1,10]-phenanthrolin}l-2-
ylidene were investigated. The complexes were successfully used
as catalysts in the C-C coupling reactions such as Suzuki-Miyaura
and Mizoroki-Heck reactions. The poly-nuclear complexes display
better activities compared to the mono-nuclear derivatives, thus
proposing that an increase in metal moieties leading to an increase
in activity in cross-coupling reaction. The most active complex was
8. This activity of 8 may be a consequence of the lability of pyridine
ligands in the PEPPSI type complex. We believe that the unique
topological properties of palladium complexes derived from imi-
dazo{ [4,5-f] [1,10]-phenanthrolin}l-2-ylidene, that migh have
facilitated the interaction between aromatic substrate and the
catalyst through
p stacking. The systems reported here are likely to
be appropriate synthons for generating supramolecular assemblies
and catalytic properties. Current research in our laboratory is
focused in synthesis heterobimetalic complexes and their different
cross-coupling reactions.
Table 2
Crystal data and structure refinement parameters for compound
L5.2HI.
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C21H30N4I2O2
624.29
Triclinic
P-1
8.3747 (5)
10.6876 (6)
13.9932 (8)
91.687 (5)
99.713 (4)
96.391 (4)
1225.35 (12)
2
1.692
2.59
1.5e27.2
16786
5157
4. Experimental
All manipulations were performed in air. The solvents were used
as received. The reagents were purchased from Sigma-Aldrich,
Merck, Alfa Aesar and Acros Organics. The compound L1-4 were
prepared according to the literature methods [14]. 1H, 13C NMR
spectra were recorded with a Varian AS 400 Mercury instrument.
b (Å)
c (Å)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
As solvent, CDCl3 and DMSO was employed. Chemical shifts (d)
V (Å3)
were given in ppm and coupling constants (J) in Hz. FT-IR spectra
were recorded on a Perkin Elmer Spectrum 100 series and UV
spectra were on PG T60 UVevisible spectrophotometer. Elemental
analyses were performed on Perkin Elmer PE 2400 elemental
analyzer.
Z
Dc (g cmꢀ3
)
m
q
(mmꢀ1
)
range (ꢁ)
Measured refls.
Independent refls.
Mass spectrometry analysis was performed on an autoflex III
MALDI TOF/TOF MS system (Bruker Daltonics, Bremen, Germany).
The instrument was operated in positive ion reflectron mode with a
reflectron acceleration voltage of 21 keV. The ions were generated
Rint
S
0.076
1.06
0.052/0.134
2.20/-1.47
R/wR
Drmax/ )
Drmin (eÅꢀ3

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
101
Table 3
Screening of bases and reaction conditions.
Entry
Base
Solvent
Yield (%)
1
2
3
4
5
6
7
8
9
Cs2CO3
Cs2CO3
Cs2CO3
KOH
Na2CO3
K2CO3
Cs2CO3
K3PO4
NaOH
iPrOH
DMF
H2O
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
DMF/H2O
21
44
15
52
67
59
99
63
52
89a
10
Cs2CO3
The SuzukieMiyaura reaction of 4-chloroacetophenone (1.0 mmol), and phenylboronic acid (1.5 mmol), base (2.0 mmol), solvent (1:1, 4 mL), % 0.5 mol of cat. (8). Yields were
determined by gas chromatography for an average of 2 runs.
a
The reaction was carried out in the presence of a drop of Hg(0).
Table 4
Suzuki-Miyaura reaction of aryl chlorides.
Entry
Ar-Cl
Ar-Ph
Yield (%) 0.5 h
Yield (%) 1.0 h
Yield (%) 1.5 h
1
2
3
4
5
6
7
8
9
CH3(O)C-C6H4-4-Cl
CH3(O)C-C6H4-2-Cl
Me-C6H4-4-Cl
CH3O-C6H4-4-Cl
OHC-C6H4-4-Cl
CH3O-C6H4-2-Cl
NO2-C6H4-4-Cl
2,4-(Me)2 -C6H3-Cl
2,3-(Me)2 -C6H3-Cl
2,4,6-(Me)3 -C6H2-Cl
CH3(O)C-C6H4-4-Ph
CH3(O)C-C6H4-2-Ph
Me-C6H4-4-Ph
CH3OC-C6H4-4-Ph
OHC-C6H4-4-Ph
CH3O-C6H4-2-Ph
NO2-C6H4-4-Ph
2,4-(Me)2 -C6H3- Ph
2,3-(Me)2 -C6H3-Ph
2,4,6-(Me)3 -C6H2-Ph
49
37
35
30
34
21
29
32
38
17
76
68
65
71
69
47
56
65
59
38
99
89
80
82
82
54
83
73
69
51
10
The SuzukieMiyaura reaction of Aryl chlorides (1.0 mmol), and phenylboronic acid (1.5 mmol), Cs2CO3 (2.0 mmol), DMF/H2O (4 mL), % 0,5 mol of cat. (8), 100 ꢁC.
Table 5
Palladium-catalyzed C-C coupling reaction of styrene with 4-bromoacetophenone.
Entry
Catalyst
Cat. loading (mol%)
Yield (%) 0.5 h
Yield (%) 1.0 h
Yield (%) 2.0 h
Yield (%) 4.0 h
1
2
3
4
5.HPF6
1.00
0.25
0.33
0.50
12
25
34
13
26
38
45
30
38
51
66
46
45
65
84
54
7
8
6
The 4-bromoacetophenone (1.0 mmol), styrene (1.2 mmol), Na2CO3 (2.0 mmol), DMF (4 mL), 100 ꢁC.
using 337-nm nitrogen laser and the spectra were acquired over a
400e5000 m/z mass range. For each spectrum, at least 1000 laser
shots were averaged at a laser frequency of 100 Hz and the system
was externally calibrated using peptide calibration mixture (Bruker
Daltonics, Peptide Calibration mixture).
The all-trans retinoic acid (RA) was used as a matrix throughout
the analysis. The matrix was prepared at a concentration of 0.1 M in
THF. The small amounts of samples were dissolved in the DMSO
solvent. Each sample were mixed separately with an RA matrix as a
conditions based on dried droplet method.
Synthesis of the L5.2HI: A mixture of L4 (2.0 g, 7.23 mmol), in 1-
Iodobutane (10 mL) was refluxed for 48 h with stirring. The reaction
mixture is allowed to cool down to room temperature and the 1-
Iodobutane was distilled under reduced pressure. The dark red
residue was washed with diethyl ether (3 ꢂ 10 mL) and dried in
vacuum. Dark red crystals were obtained from slow evaporation of
acetonitrile. Yield 3.00 g, 90%, 1H NMR (400 MHz, DMSO-d6):
d 9.89
(s, 1 H, C2-H), 9.20 (d, J ¼ 4.2 Hz, 2 H, phen-H), 8.92 (d, J ¼ 8.4 Hz,
2 H, phen-H), 7.96 (dd, J ¼ 8.4, 4.4 Hz, 2 H, phen-H), 4.92 (t,
J ¼ 7.1 Hz, 4 H, butyl-CH2), 1.99 (m, 4 H, butyl-CH2), 1.48 (m, 4 H,
ratio of 2:5 and, 1
mL, of final solution was deposited onto the
stainless MALDI target and allowed to dry under ambient

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
102
Table 6
Palladium-catalyzed C-C coupling reaction of styrene and n-butyl acrylate with aryl bromides.
Entry
R-Br
R'
Yield (%) 0.5 h
Yield (%) 1.0 h
Yield (%) 2.0 h
Yield (%) 4.0 h
1
2
3
4
5
6
7
8
9
CH3(O)C-C6H4-4-Br
NO2-C6H4-4-Br
Me-C6H4-4-Br
CH3O-C6H4-4-Br
OHC-C6H4-4-Br
CH3(O)C-C6H4-4-Br
NO2-C6H4-4-Br
Me-C6H4-4-Br
C6H5
C6H5
C6H5
C6H5
29
41
25
38
42
9
10
4
5
44
50
38
45
58
17
19
11
13
27
63
65
54
66
78
21
28
15
18
42
84
71
65
76
92
35
46
22
29
69
C6H5
COOnBu
COOnBu
COOnBu
COOnBu
COOnBu
CH3O-C6H4-4-Br
OHC-C6H4-4-Br
10
15
Aryl bromide (0.50 mmol), styrene/n-butyl acrylate (0.75 mmol), Na2CO3 (2.00 mmol), 8 (0.33% mol), DMF (4 mL). Yields were determined by gas chromatography for an
average of 2 runs.
butyl-CH2), 0.98 (t, J ¼ 7.3 Hz, 6 H, butyl-CH3). 13C NMR (100 MHz,
1H-imidazo[4,5-f] [1,10]phenanthroline (55 mg, 0.2 mmol) in MeCN
(5 mL), stirred for 24 h at room temperature. The resulting cream
precipitates were filtered. The crude product was washed with
diethyl ether (2 ꢂ 5 mL), dried under vacuum. Yield 79 mg, 87%, 1H
DMSO-d6): d 150.5, 144.8, 142.1, 130.8, 125.4, 124.9, 118.4, 50.3, 30.9,
19.3, 13.9. Anal. Calc. for C21H26N4I2 (M ¼ 588.27): C, 42.88; H, 4.45;
N, 9.52; Found: C, 42.78, H, 4.40, N, 9.58%.
L5.HPF6: Yield: 1.80 g, 72%. 1H NMR (400 MHz, DMSO-d6):
NMR (400 MHz, CDCl3):
d
9.17 (m, 2 H, phen-H), 8.98 (dd, J ¼ 8.0,
d
10.17 (s, 1 H, C2-H), 9.21 (m, 2 H, phen-H), 8.43 (d, J ¼ 8.0 Hz, 2 H,
1.6 Hz, 1 H, phen-H), 8.54 (dd, J ¼ 8.0, 1.8 Hz, 1 H, phen-H), 7.99 (s,
1 H, C2-H), 7.71 (m, 2 H, phen-H), 4.61 (t, J ¼ 7.2 Hz, 2 H, butyl-CH2),
2.03 (m, 2 H, butyl-CH2), 1.51 (m, 2 H, butyl-CH2), 0.98 (t, J ¼ 6.8 Hz,
phen-H), 7.94 (m, 2 H, phen-H), 4.95 (t, J ¼ 8.0 Hz, 4 H, butyl-CH2),
2.03 (m, 4 H, butyl-CH2), 1.50 (m, 4 H, butyl-CH2), 1.02 (m, 6 H,
butyl-CH3). 13C NMR (100 MHz, DMSO-d6):
d
149.1, 144.7, 144.0,
3 H, butyl-CH3). 13C NMR (100 MHz, CDCl3):
d 155.9, 148.9, 147.9,
135.6, 127.1, 126.5, 120.8, 50.7, 30.3, 19.5, 14.0.19F NMR (376 MHz,
142.8, 130.4, 128.1, 123.6, 122.2, 47.9, 32.0, 22.6, 19.8. Anal. Calc. for
DMSO-d6):
d
d
ꢀ70.5 (d, J ¼ 639.2 Hz). 31P NMR (161 MHz, DMSO-d6):
C
17H16Cl2N4Pd (M ¼ 453.66): C, 45.01; H, 3.55; N, 12.35; Found: C,
ꢀ144.1 (septet, J ¼ 709.7 Hz). Anal. Calc. for C21H27N4F6P
44.98; H, 3.49; N, 12.31.
(M ¼ 480.43): C, 52.50; H, 5.66; N, 11.66; Found: C, 52.68, H, 5.80, N,
5.HPF6: A mixture of Pd(MeCN)2Cl2 (26 mg, 0.1 mmol) and
L5.HPF6 as a ligand (48 mg, 0.1 mmol) in MeCN (5 mL), stirred for
2 h at room temperature. The resulting cream precipitates were
filtered. The crude product was washed with diethyl ether
(2 ꢂ 5 mL), dried under vacuum. Yield: 58 mg, 88%, 1H NMR
11.42%.
1: A mixture of Pd(MeCN)2Cl2 (52 mg, 0.2 mmol) and 1,10-
phenanthroline (36 mg, 0.2 mmol) in MeCN (5 mL), stirred for
24 h at room temperature. The resulting cream precipitates were
filtered. The crude product was washed with diethyl ether
(2 ꢂ 5 mL), dried under vacuum. Yield 61 mg, 86%, 1H NMR
(400 MHz, DMSO-d6):
d 10.23 (s, 1 H, C2-H), 9.32 (m, 2 H, phen-H),
8.74 (d, J ¼ 8.0 Hz, 2 H, phen-H), 8.09 (m, 2 H, phen-H), 5.03 (t,
J ¼ 8.0 Hz, 4 H, butyl-CH2), 2.11 (m, 4 H, butyl-CH2), 1.56 (m, 4 H,
butyl-CH2), 1.05 (m, 6 H, butyl-CH3). 13C NMR (100 MHz, DMSO-d6):
(400 MHz, DMSO-d6):
d
9.30 (dd, J ¼ 5.0, 1.2 Hz, 2 H, phen-H), 9.07
(dd, J ¼ 8.2, 1.6 Hz, 2 H, phen-H), 8.35 (s, 2 H, phen-H), 8.22 (dd,
J ¼ 8.2, 4.4 Hz, 2 H, phen-H). 13C NMR (100 MHz, DMSO-d6):
d
148.2,
d 149.8, 145.0, 143.6, 135.1, 126.9, 126.8, 120.3, 50.2, 30.0, 19.0,
142.4, 138.0, 130.1, 128.0, 126.2. Anal. Calc. for C12H8Cl2N2Pd
(M ¼ 357.53): C, 40.31; H, 2.26; N, 7.84; Found: C, 40.27; H, 2.18;
N,7.83.
13.5.19F NMR (376 MHz, DMSO-d6):
NMR (161 MHz, DMSO-d6):
d
ꢀ70.2 (d, J ¼ 564.0 Hz). 31P
d
ꢀ144.3 (septet, J ¼ 709.9 Hz). Anal.
Calc. for C21H25Cl2F6N4PPd (M ¼ 655.74): C, 38.46; H, 3.84; N, 8.54;
Found: C, 38.41, H, 3.79, N, 8.48%.%. MS (MALDI): m/z ¼ 736.88
[Mþ2 þ DMSO]þ.
2: A mixture of Pd(MeCN)2Cl2 (52 mg, 0.2 mmol) and 1,10-
phenanthroline-5,6-dione (42 mg, 0.2 mmol) in MeCN (5 mL),
stirred for 24 h at room temperature. The resulting cream pre-
cipitates were filtered. The crude product was washed with diethyl
ether (2 ꢂ 5 mL), dried under vacuum. Yield 64 mg, 89%, 1H NMR
6: The salt 5.HPF6 (66 mg, 0.1 mmol), Pd(OAc)2 (12 mg,
0.05 mmol), KBr (120 mg, 0.1 mmol) ve NaOAc (33 mg, 0.40 mmol)
were suspended in DMSO (10 mL) and stirred at 90 C for 48 h. After
the solution was cooled, DMSO was distilled in vacuum. The
product was purified by column chromatography on silica gel.
Elution with CH2Cl2 gave a product. Yield: 106 mg, 82%, 1H NMR
(400 MHz, DMSO-d6):
d
9.19 (d, J ¼ 5.2 Hz, 2 H, phen-H), 8.76 (dd,
J ¼ 8.4, 1.2 Hz, 2 H, phen-H), 8.02 (dd, J ¼ 8.0, 5.4 Hz, 2 H, phen-H).
13C NMR (100 MHz, DMSO-d6):
d
173.2, 150.6, 140.6, 128.1, 126.4,
109.4. Anal. Calc. for C12H6Cl2N2O2Pd (M ¼ 387.51): C, 37.19; H, 1.56;
(400 MHz, DMSO-d6):
d
9.37 (d, J ¼ 8.0 Hz, 4 H, phen-H), 9.10 (d,
N, 7.23; O, 8.26; Found: C, 37.16; H, 1.49; N, 7.21; O, 8.23.
J ¼ 8.0 Hz, 4 H, phen-H), 8.17 (m, 4 H, phen-H),5.42 (t, J ¼ 8.0 Hz, 8 H,
3: A mixture of Pd(MeCN)2Cl2 (52 mg, 0.2 mmol) and 1H-imi-
dazo[4,5-f] [1,10]phenanthroline (44 mg, 0.2 mmol) in MeCN
(5 mL), stirred for 24 h at room temperature. The resulting cream
precipitates were filtered. The crude product was washed with
diethyl ether (2 ꢂ 5 mL), dried under vacuum. Yield 68 mg, 85%, 1H
butyl-CH2), 2.12 (m, 8 H, butyl-CH2), 1.73 (m, 8 H, butyl-CH2), 1.10
(m, 12 H, butyl-CH3). 13C NMR (100 MHz, DMSO-d6):
d
171.9, 150.3,
144.2, 133.7, 126.8, 126.7, 118.9, 50.9, 29.9, 19.2, 13.7. Anal. Calc. for
C
42H52N8Br2Cl4Pd3 (M ¼ 1287.78): C, 39.17; H, 3.91; N, 8.70; Found:
C, 39.28, H, 3.76, N, 8.64%. MS (MALDI): m/z ¼ 1072.86 [Mþ2-2Br-
NMR (400 MHz, DMSO-d6):
d
9.11 (d, J ¼ 6.4 Hz, 2 H, phen-H), 9.09
Bu]þ.
(d, J ¼ 8.4 Hz, 2 H, phen-H), 8.66 (s, 1 H, C2-H), 8.11 (dd, J ¼ 8.2,
5.4 Hz, 2 H, phen-H). Anal. Calc. for C13H8Cl2N4Pd (M ¼ 397.56): C,
39.27; H, 2.03; N, 14.09; Found: C, 39.17; H, 2.00; N, 14.03.
4: A mixture of Pd(MeCN)2Cl2 (52 mg, 0.2 mmol) and 1-butyl-
7: The salt 5.HPF6 (66 mg, 0.1 mmol), Pd(OAc)2 (23 mg,
0.1 mmol), KBr (240 mg, 0.60 mmol) and NaOAc (33 mg, 0.40 mmol)
were suspended in DMSO (10 mL) and stirred at 90 C for 48 h. The
solvent was removed under vacuum. The product was purified by

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L. Gok et al. / Journal of Organometallic Chemistry 827 (2017) 96e104
103
column chromatography on silica gel. Elution with CH2Cl2 gave a
product. Yield: 127.0 mg, 82%, 1H NMR (400 MHz, DMSO-d6):
9.45
(d, J ¼ 4.0 Hz, 4 H, phen-H), 9.10 (d, J ¼ 4.0 Hz, 4 H, phen-H), 8.18 (m,
4 H, phen-H),5.42 (m, 8 H, butyl-CH2), 2.13 (m, 8 H, butyl-CH2), 1.73
(m, 8 H, butyl-CH2), 1.11 (m, 12 H, butyl-CH3). 13C NMR (100 MHz,
chromatography for an average of two runs. Products were purified
by column chromatography on silica gel using a mixture of hexane
and EtOAc (4:1) as eluent.
d
4.4. General procedure for the Heck coupling reactions
DMSO-d6):
d 150.4, 144.3, 133.7, 126.8, 126.6, 118.9, 50.9, 29.9, 19.2,
13.7. Anal. Calc. for C42H52N8Br4Cl4Pd4 (M ¼ 1554.01): C, 32.46; H,
3.24; N, 7.21; Found: C, 32.14, H, 3.19, N, 7.17%. MS (MALDI): m/
z ¼ 855.98 [M/2þDMSO]þ.
A two-necked 25 mL flask fitted with a reflux condenser was
charged with aryl chlorides (1.0 mmol), 2 mmol Na2CO3, styrene
(1.5 mmol), diethyleneglycol-di-n-butylether (0.6 mmol, internal
standard), 1 mol% for 5.HPF6; 0.5 mol % for 8; 0.33 mol % for 6;
0.25 mol % for 7 in 4 mL of DMF. The flask was placed in a preheated
oil bath (100 ꢁC) under argon atmosphere for 4 h. After the required
reaction time, the solution was allowed to cool down to room
temperature and then extracted with Et2O (3 ꢂ 5 mL). The com-
bined organic layers were dried over anhydrous Na2SO4 and the
solvent evaporated. The residue was purified by column chroma-
tography on silica gel using a mixture of hexane and EtOAc (4:1) as
eluent. Yields were determined by gas chromatography for an
average of two runs.
8: A sample of compound 7 (100 mg, 0.07 mmol) and pyridine
(13 mg, 0.10 mmol) were dissolved in 10 mL of CH2Cl2. The mixture
was stirred at ambient temperature for 1 h. The volume of the so-
lution was reduced to about 5 mL in vacuo. Diethyl ether (10 mL)
was added to the solution to obtain a bright cream precipitate,
which was collected by filtration, washed with 10 mL of diethyl
ether, and dried in vacuo. Yield: 44 mg, 74%, 1H NMR (400 MHz,
DMSO-d6):
d
9.46 (d, J ¼ 5.2 Hz, 2 H, py-H), 9.13 (d, J ¼ 8.2 Hz, 2 H,
Py-H), 8.93 (m, 2H, phen-H), 8.19 (m, 2 H, phen-H), 8.04 (m, 1 H, Py-
H), 7.63 (m, 2 H, phen-H), 5.49 (br, 4 H, butyl-CH2), 2.18 (m, 4 H,
butyl-CH2), 1.76 (m, 4 H, butyl-CH2), 1.12 (m, 12 H, butyl-CH3). 13
C
NMR (100 MHz, DMSO-d6): d 154.5, 150.9, 144.9, 134.2, 127.3, 127,0,
Acknowledgements
125.8, 119,5, 51.4, 30.6, 19.8, 14.1. Anal. Calc. for C26H30Br2Cl2N5Pd2
(M ¼ 856.10): C, 36.48; H, 3.53; N, 8.18; Found: C, 36.88, H, 3.49, N,
8.26%. MS (MALDI): m/z ¼ 856.90 [M]þ.
We sincerely thank to Prof. Dr. S¸ amil Is¸ ık for his help with the
data collection. Thanks to Biological Mass Spectrometry and Pro-
teomics Laboratory at IYTE Chemistry Department for their help
with mass measurements. Financial support from Ege University
4.1. Crystallographic data collection and refinement
_
(Project 2012-BIL-042; 2013 FEN 062) and TÜBITAK (111T398) is
Diffraction experiments were carried out at 296 K on a Stoe IPDS
diffractometer. The structure was solved by direct methods and
refined using the programs SHELXS97 and SHELXL97 [26]. All non-
hydrogen atoms were refined anisotropically by full-matrix least
squares methods [26]. The parameters for data collection and
structure refinement of compound L5.2HI are listed in Table 2.
Water H atoms were located in a difference map refined subject to a
DFIX restraint. All hydrogen atoms bonded to C atoms were refined
using a riding model with CeH ¼ 0.93e0.97. The constraint
gratefully acknowledged.
Supplementary material
CCDC 937867 contains the supplementary crystallographic data
for L5.2HI. This data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.htmL (or from the CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: þ44 1223 336033; e-mail:
deposit@ccdc.cam.ac.uk). Supplementary data contain NMR
spectra and Mass data for new complexes.
U
iso(H) ¼ 1.2Ueq(C and CH2) or 1.5Ueq(CH3) was applied. The
following procedures were implemented in our analysis: data
collection: X-Area, cell refinement: X-Area, data reduction: X-RED
[27]; program(s) used for molecular graphics were as follows:
Mercury programs [28] software used to prepare material for
publication: WinGX [29].
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́