Heck coupling reaction using monomeric ortho-palladated complex of 4-methoxy- benzoylmethylenetriphenylphosphorane under microwave irradiation

Article abstract of DOI:10.1002/aoc.1705

The activity of [Pd(C₆H₄CH₂ NH ₂-κ²-C-N)PPh₃MOBPPY]OTf complex, A (MOBPPY = 4-methoxybenzoylmethylenetriphenyl- phosphoraneylide), was investigated in the Heck-Mizoroki C-C cross-coupling reaction under conventional heating and microwave irradiation conditions. The complex is an active and efficient catalyst for the Heck reaction of aryl halides. The yields were excellent using a catalytic amount of [Pd(C₆H₄CH ₂ NH₂-κ²-C-N)PPh₃MOBPPY]OTf complex in N-methyl-2-pyrrolidinone (NMP) at 130 °C and 600 W. In comparison to conventional heating conditions, the reactions under microwave irradiation gave higher yields in shorter reaction times. Copyright

Full text of DOI:10.1002/aoc.1705

Full Paper
Received: 23 February 2010
Revised: 18 May 2010
Accepted: 20 May 2010
Published online in Wiley Online Library: 23 August 2010
(wileyonlinelibrary.com) DOI 10.1002/aoc.1705
Heck coupling reaction using monomeric
ortho-palladated complex of 4-methoxy-
benzoylmethylenetriphenylphosphorane
under microwave irradiation
Abdol R. Hajipoura,b∗, Kazem Karamia and Ghazal Tavakolia
The activity of [Pd(C6H4CH2 NH2-κ2-C-N)PPh3MOBPPY]OTf complex, A (MOBPPY = 4-methoxybenzoylmethylenetriphenyl-
phosphoraneylide), was investigated in the Heck–Mizoroki C–C cross-coupling reaction under conventional heating and
microwave irradiation conditions. The complex is an active and efficient catalyst for the Heck reaction of aryl halides. The yields
were excellent using a catalytic amount of [Pd(C6H4CH2 NH2-κ2-C-N)PPh3MOBPPY]OTf complex in N-methyl-2-pyrrolidinone
(NMP) at 130 ◦C and 600 W. In comparison to conventional heating conditions, the reactions under microwave irradiation gave
c
higher yields in shorter reaction times. Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Keywords: orthopalladate; Heck reaction; catalyst; microwaves
Introduction
kinetically/thermallyactivated.[14] Thisrapidin situheatingiscalled
the superheating effect.[15]
Because of the many applications of carbon–carbon bond
formation in the areas of bioactive compounds, natural products
and high performance materials[1] over the past few years, the
C–C coupling reactions have become a versatile tool in organic
synthesis.[2–4] One of the most efficient methods in the formation
of the C(sp2) –C(sp2) bond is the Heck reaction,[5–7] in which a
palladium-catalyzed reaction is carried out between an olefin and
an aryl, alkenyl halide or triflate in the presence of a base. This
reaction was discovered independently by Heck[8] and Mizoroki[9]
about 40 years ago and is generally catalyzed in the solution by
palladium species generated from either Pd(0) complexes or Pd(II)
salts.[10] As the Heck reaction is one of the most promising metal-
catalyzed syntheses[11] of monomers, pharmaceuticals, sunscreen
agents and herbicides, considerable efforts have recently been
devoted to finding new catalytic systems and methodologies to
improve the reaction conditions. However, to develop efficient
methods for these reactions, the catalyst should be chosen
properly and most researches have focused on finding efficient
catalytic systems with higher activity and stability. Among the new
methods the palladacycle catalysts are the most important class
of catalyst; these complexes have been known for over 30 years
and the Heck reaction has been performed with activated and
non-activated aryl halides using very low concentrations of these
catalysts.
Application of MW irradiation as an efficient heating source was
reported as early as the 1940s,[16] and the first application of this
synergy source in organic synthesis was reported in 1986 by Gedye
and Giguere.[17,18] In 1996, Hallberg and co-workers applied this
method in the Heck cross coupling reaction.[19]
Herein, in continuation of our previous work on pal-
ladacycle systems and microwave assisted reactions,[20–25]
we wish to report the application of [Pd(C6H4CH2NH2-
κ2-C-N)PPh3MOBPPY]OTf complex,
A
(MOBPPY
=
4-meth
oxybenzoylmethylenetriphenylphosphoraneylide), as a thermally
stable and oxygen insensitive catalyst[26] for Heck coupling reac-
tion of various types of aryl halides under both traditional heating
and microwave irradiation conditions (Scheme 1).
Results and Discussion
Initially, the Heck cross-coupling reaction conditions using
[Pd(C6H4CH2NH2-κ2-C-N)PPh3MOBPPY]OTf complex were opti-
mized for the reaction of iodoanisole and methylacrylate using
0.2 mol% catalyst, various bases and solvents under microwave
irradiation (600 W, 130 ◦C). As demonstrated in Table 1 (entry 4),
K2CO3 as base and 1-methyl-2-pyrolidinone (NMP) as solvent gave
the best results.
Microwave irradiation methodology has advantages in organic
and inorganic synthesis such as greater energy efficiency and
higher reaction rates, and in many cases improved yields in
comparison to the conventional conditions.[12] The reaction rate
improvement could be explained by considering the higher and
more rapid temperature homogeneity reached by employing
microwave (MW) heating methods.[13] Although in conventional
heating methods the vessel is heated and then the heat transfers
by convention, in MW-assisted reactions molecules are directly
∗
Correspondence to: Abdol R. Hajipour, Pharmaceutical Research Laboratory,
Department of Chemistry, Isfahan University of Technology, Isfahan 84156,
I. R. Iran. E-mail: haji@cc.iut.ac.ir
a
Pharmaceutical Research Laboratory, Department of Chemistry, Isfahan
University of Technology, Isfahan 84156, I. R. Iran
b
Department of Pharmacology, University of Wisconsin, Medical School, 1300
University Avenue, Madison, WI 53706-1532, USA
c
Appl. Organometal. Chem. 2010, 24, 798–804
Copyright ꢀ 2010 John Wiley & Sons, Ltd.

Heck coupling with monomeric ortho-palladated complex of MOBPPY
NH2
Pd
+PPh3
Cl
Cl
1/2
NH2
Pd
Pd
PPh3
H2N
Cl
Ye =4-methoxybenzoylmethylene-
triphenylphosphorane ylide (MOBPPY)
i)+AgOTf, THF or Me2CO
ii)-AgCl
iii)+Ye
Scheme 1. Synthesis of Palladacycle Complex [Pd (C6H4CH2NH2-κ2-C-N)PPh3MOBPPY]OTf.
Table 1. Optimization of base and solvent under microwave
Table 2. Optimization of catalyst concentration under microwave
irradiationa
irradiationa
Temperature Time
Mol%
catalyst
Entry
Base
Solvent
(◦C)
(min) Conversion (%)
Time (min)
Temperature (◦C)
Conversion (%)
1
2
3
4
5
6
7
Et3N
Cs2CO3
Na2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NMP
NMP
130
130
130
130
130
130
130
2
2
2
2
2
2
2
0
70
Trace
95
75
0
None
0.01
0.02
0.05
0.1
2
2
2
2
2
2
2
2
130
130
130
130
130
130
130
130
0
30
NMP
50
NMP
85
DMF
95
CH3CN
Toluene
0.2
95
0
0.4
98
0.6
100
a Reaction conditions: 2 mmol aryl halide, 5 mmol olefin, 2.2 mmol
a Reaction conditions: 2 mmol aryl halide, 5 mmol olefin,
K2CO3, 0.2 mol% palladacycle A.
2.2 mmol K2CO3, and palladacycle A.
We also optimized the concentration of catalyst, employing
various amounts of catalyst for the reaction of iodoanisole and
methylacrylate using K2CO3 as base and NMP as solvent. The
data clearly showed that 0.1 mol% of catalyst gave the highest
yields (Table 2). As this catalyst is not sensitive to oxygen,
the reactions were carried out under an air atmosphere. We
applied these conditions for Heck cross-coupling reaction of
different types of aryl halides with methylacrylate under both
conventional heating and microwave irradiation, as shown in
Tables 3 and 4.
The results showed that aryl halides with either electron-
withdrawing or electron-donating substituents reacted with
olefins rapidly and generated the coupled products with excellent
yields. We also tried these reactions employing styrene as the
olefin under both microwave irradiation and traditional heating
c
Appl. Organometal. Chem. 2010, 24, 798–804
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

A. R. Hajipour, K. Karami and G. Tavakoli
Table 3. Heck reaction of aryl halides under conventional heating conditions in an oil batha
Time
(h)
Conversion
(%)
Yieldb
(%)
Entry
1
ArX
RꢁCH CH2
Product
2.5
100
91
2
3
7
90
84
1.5
100
92
4
5
1.5
6.5
100
100
94
90
6
7
8
1.75
3
100
100
100
89
90
93
3
9
8
90
85
10
11
1.75
9.5
100
90
93
83
12
8
85
78
a Reaction conditions: 2 mmol aryl halide, 5 mmol olefin, 2.2 mmol K2CO3, 0.1 mol% palladacycle A and temperature 130 ◦C, 600 W.
b Isolated yield.
conditions (Tables 3 and 5). We found that, in comparison to
the heating conditions, the microwave irradiation reduced the
reaction times from hours to minutes. Also, the results listed
in Tables 4 and 5 clearly show that the coupling reactions with
methylacrylate as the olefin were faster than styrene. In the case of
1-bromo-3-chlorobenzene,althoughthisprocedurecouldactivate
the C–Cl bond, by using stoichiometric amount of olefins only the
Br was substituted in each case, which may be due to the higher
activity of Br compared with Cl [21]. In all of the reactions, only the
trans isomers were produced. Furthermore as shown in Table 4
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2010, 24, 798–804

Heck coupling with monomeric ortho-palladated complex of MOBPPY
Table 4. Microwave assisted Heck reaction of aryl halides with methylacrylatea
Time
(min)
Conversion
(%)
Yieldb
(%)
Entry
1
ArX
Product
1
1
4
100
100
100
93
94
93
2
3
4
6
100
90
5
6
7
1
6
100
100
90
94
91
84
10
8
9
10
40
90
88
84
81
10
13
100
89
11
12
4
100
90
93
82
20
a Reaction conditions: 2 mmol aryl halide, 5 mmol olefin, 2.2 mmol K2CO3, 0.1 mol% palladacycle A, temperature 130 ◦C and 600 W.
b Isolated yield.
c
Appl. Organometal. Chem. 2010, 24, 798–804
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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A. R. Hajipour, K. Karami and G. Tavakoli
Table 5. Microwave assisted Heck reaction of aryl halides with styrenea
Time
(min)
Conversion
(%)
Yieldb
(%)
Entry
1
ArX
Product
1
100
100
100
95
94
96
2
3
2
12
4
18
98
92
5
6
6
100
85
96
80
17
7
18
90
83
8
9
10
30
98
97
92
91
10
40
85
78
11
12
6
100
87
92
80
25
a Reaction conditions: 2 mmol aryl halide, 5 mmol olefin, 2.2 mmol K2CO3, 0.001 mmol palladacycle A and temperature 130 ◦C and 600 W.
b Isolated yield.
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2010, 24, 798–804

Heck coupling with monomeric ortho-palladated complex of MOBPPY
(entries 11 and 12) and Table 5 (entries 11 and 12), this method
can be used for the Heck reaction of even less reactive aryl chloride
derivatives with longer reaction times.
trans-4-Methoxystilbene (entry 3, Table 3 and entry 3, Table 5)
M.p. 135.5–137.1 ◦C;[27] found 131–135 ◦C.1H NMR (400 MHz,
CDCl3): δ = 7.50–7.46 (m, 4H), 7.38–7.36 (br t, 3H), 7.11 (d,
1H, J = 16.4 Hz), 7.01 (d, 1H, J = 16.4 Hz), 6.93 (d, 2H, J = 8.4 Hz),
3.85 (s, 3H). 13C NMR (100 MHz, ppm, CDCl3): δ = 159.6, 137.7,
130.1, 130.0, 129.8, 128.5, 128.4, 127.7, 127.4, 127.2, 126.6, 126.5,
114.2, 114.1, 55.2. IR (KBr, cm−1): ν 3055, 2963, 1580.
Conclusion
In summary, here we repot a highly active and efficient catalyst for
promoting the Heck cross-coupling reaction of various aryl halides
with olefins to produce the corresponding products in excellent
yields and high chemoselectivity in short reaction times. Reactions
were carried out under both conventional heating and microwave
irradiation conditions. The results showed that under microwave
irradiation conditions, the reactions were completed in shorter
reaction times.
trans-4-Cyanostilbene (entry 7, Table 3 and entry 4, Table 5)
M.p. 117–119 ◦C;[28] found 115–118 ◦C. 1H NMR (400 MHz, CDCl3):
δ = 7.65 (d, 2H, J = 8.2 Hz, Ph), 7.60 (d, 1H, J = 8 Hz, Ph), 7.55 (d,
2H, J = 7.2 Hz, Ph), 7.41 (t, 2H, J = 7.2 Hz), 7.34–7.35 (br d, 2H,
Ph), 7.23 (d, 1H, J = 16.2 Hz, CH), 7.10 (d, 1H, J = 16.4 Hz, CH). 13C
NMR (100 MHz, ppm, CDCl3): δ = 141.9, 136.3, 132.5, 132.4, 128.9,
128.7, 128.5, 127.9, 127.5, 127.2, 126.9, 126.8, 126.7, 119.5, 110.8.
IR (KBr, cm−1): ν 3044, 2924, 2226, 1602.
Experimental
General
1H-NMR spectra were recorded using 500 and 400 MHz and
13C-NMR spectra were recorded using 125 and 100 MHz in CDCl3
solutions at room temperature on a Bruker Avance 500 instrument
(Rheinstetten, Germany) and Varian 400 NMR (TMS was used
as an internal standard). The FT-IR spectra were recorded on a
spectrophotometer (Jasco-680, Japan). We used the Milestone
Microwave (Microwave Labstation) for synthesis. All chemicals
werepurchasedfromMerckandAldrichandwereusedasreceived.
The reactions were carried out in N-methyl-2-Pyrrolidinone (NMP)
at 130 ◦C 600 W microwave irradiation or at 130 ◦C under heating
conditions using an oil bath.
Methyltrans-3-chlorocinnamate(entry4,Table 3andentry5,Table 4)
1H NMR (400 MHz, CDCl3): δ = 7.64 (d, 1H, J = 16 Hz, CH),
7.53–7.52(brt,1H,Ph),7.41–7.25(m,3H,Ph),6.45(d,1H,J = 16 Hz,
CH), 3.82 (s, 3H, CH3). 13C NMR (100 MHz, ppm, CDCl3): δ = 175.3,
167.8, 143.2, 136.2, 135.1, 131.4, 127.8, 126.2, 119.2, 51.5. IR (KBr,
cm−1): ν 3034, 2940, 1718.
Methyl trans-4-formylcinnamate (entry 7, Table 4)
M.p. 82–84 ◦C;[21] found 81–84 ◦C. 1H NMR (400 MHz, CDCl3):
δ = 10.10 (s, 1H, CHO), 7.92 (d, 2H, J = 8.4 Hz, Ph), 7.71 (d,
1H, J = 15.6 Hz, CH), 7.66 (d, 2H, J = 8.2 Hz, Ph), 6.57 (d, 1H,
J = 15.8 Hz, CH), 3.85 (s, 3H, CH3). 13C NMR (100 MHz, ppm, CDCl3):
δ = 191.3, 168.8, 143.1, 140.0, 137.2, 130.2, 130.1, 128.3, 128.0,
121.0, 52.5. IR (KBr, cm−1): ν 3034, 2940, 2750, 1725, 1710.
Synthesis of Palladacycle Complex [Pd(C6H4CH2NH2-κ2-C-
N)PPh3MOBPPY]OTf (A)
[Pd(C6H4CH2NH2-κ2-C-N)PPh3MOBPPY]OTfasapalladacyclecom-
plex was prepared according to our previous work.[26]
General Procedure for the Microwave-assisted Heck
Cross-coupling Reaction
trans-1-Styrylnaphthalene (entry 8, Table 5)
A suspension of aryl halide (2 mmol), olefin (5 mmol), K2CO3
(2.2 mmol), palladacycle complex (0.1 mol%) and NMP (5 ml)
equippedwithamagneticstirringbarandacondenserforrefluxing
wasstirredunderairatmosphere.Inthecaseofmicrowaveassisted
reactions, themixturewasheatedundermicrowaveovenat130 ◦C
and 600 W microwave irradiation. In the case of conventional
heating reactions, the above mixture was heated at 130 ◦C in an oil
bath. The reaction progress was followed by TLC (hexane–EtOAc,
85 : 15, as eluent). After competition of the reaction, the mixture
was cooled to room temperature and was diluted with ether and
water. Then the organic layer was washed with brine, dried over
MgSO4, filtered and evaporated under reduced pressure using
rotary evaporator to give the crude product that was purified by
recrystallization from ethanol.
M.p. 58–60 ◦C;[21] found 58–61 ◦C 1H NMR (500 MHz, CDCl3):
δ = 8.31 (d, 1H, J = 8.3 Hz, Ph), 7.97 (d, 1H, J = 15.8 Hz, CH),
7.88 (d, 1H, J = 8.2 Hz, Ph), 7.83 (d, 1H, J = 7.2 Hz, Ph), 7.69 (d,
2H, J = 7.4 Hz, Ph), 7.63–7.55 (m, 3H, Ph), 7.49 (t, 2H, J = 7.5 Hz,
Ph), 7.38 (t, 1H, J = 7.3 Hz, Ph), 7.24 (d, 1H, J = 16 Hz, CH). 13C
NMR (100 MHz, ppm, CDCl3): δ = 136.7, 134.2, 133.9, 132.8, 130.7,
130.4, 130.1, 129.5, 128.7, 127.5, 126.4, 126.3, 126.1, 125.7, 125.6,
124.7, 123.8, 123.4. IR (KBr, cm−1): ν 3045, 1593.
trans-9-Styrylphenanthrene (entry 9, Table 5)
M.p. 104–108 ◦C;[21] found 106–108 ◦C 1H NMR (400 MHz, CDCl3):
δ = 8.72 (d, 1H, J = 8 Hz, Ph), 8.72 (d, 1H, J = 8 Hz, Ph), 8.28 (d, 1H,
J = 8.8 Hz, Ph), 7.93 (s, 1H, Ph), 7.94 (d, 1H, J = 8.8 Hz, Ph), 7.90 (d,
1H, J = 16 Hz, CH), 7.74–7.61 (m, 6H, Ph), 7.41 (t, 2H, J = 7.6 Hz,
Ph), 7.34 (t, 1H, J = 7.6 Hz), 7.25 (d, 1H, J = 16 Hz, CH). 13C NMR
(100 MHz, ppm, CDCl3): δ = 137.6, 134.0, 132.2, 131.9, 130.8, 130.5,
130.3, 128.8, 128.7, 128.3, 128.1, 127.1, 126.9, 126.8, 126.7, 126.6,
126.4, 124.7, 124.6, 123.2, 122.8, 122.6. IR (KBr, cm−1): ν 3045, 1593.
trans-Stilbene (entry 2, Table 3 and entries 1, 2 and 11, Table 5)
M.p. 122–123 ◦C;[27] found 121–122 ◦C. 1H NMR (500 MHz, CDCl3):
δ = 7.60 (d, 4H, J = 7.4 Hz, Ph), 7.45 (t, 4H, J = 7.6 Hz, Ph), 7.35
(t, 2H, J = 7.6 Hz, Ph), 7.22 (s, 2H, CH). 13C NMR (100 MHz, ppm,
CDCl3) δ = 137.8 (2 C), 128.7 (4 C), 127.9 (4 C), 127.7 (2 C), 126.5
(2 C). IR (KBr, cm−1): ν 3076, 1594, 1493.
c
Appl. Organometal. Chem. 2010, 24, 798–804
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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A. R. Hajipour, K. Karami and G. Tavakoli
trans-4-Acetylstilbene (entry 6, Table 3 and entries 6 and 12, Table 5)
[2] K. Hamza, R. Abu-Reziq, D. Avnir, J. Blum, Org. Lett. 2004, 6, 925.
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2005, 24, 4416.
M.p. 140–144 ◦C,[27] found 136–140 ◦C.1H NMR (500 MHz, CDCl3):
δ = 8.01 (d, 2H, J = 8.3 Hz), 7.64 (d, 2H, J = 8.3 Hz), 7.59 (d, 2H,
J = 7.5 Hz), 7.44 (t, 2H, J = 7.6 Hz), 7.35 (t, 1H, J = 7.1 Hz), 7.28
(d, 1H, J = 16.3 Hz), 7.19 (d, 1H, J = 16.3 Hz), 2.53 (s, 3H).13C NMR
(100 MHz, ppm, CDCl3): δ = 197.5, 142.0, 136.7, 136.0, 131.5, 129.5,
129.1, 129.0, 128.8, 128.3, 128.2, 127.5, 127.4, 126.8, 126.5, 26.8. IR
(KBr, cm−1): ν 3019, 2960, 1678, 1600.
[8] R. F. Heck, Acc. Chem. Res. 1979, 12, 146.
[9] T. Mizoroki, K. Mori, A. Ozaki, Bull. Chem. Soc. Jpn 1971, 44, 581.
[10] A. Biffis, M. Zecca, M. Basato, J. Mol. Catal. A: Chem. 2001, 173, 249.
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Heterogeneous Catalysis, Wiley–VCH: Weinheim, 2001.
[12] a) C. S. Cundy, Collect. Czech. Chem. Commun. 1998, 63, 1699; b)
A. Loupy, Microwaves in Organic Synthesis, Wiley–VCH: Weinheim,
2002;c)A. Loupy,MicrowavesinOrganicSynthesis,Wiley:Weinheim,
2006.
trans-3-Chlorostilbene (entry 5, Table 5)
M.p. 64–69 ◦C;[21] found 65–69 ◦C.1H NMR (400 MHz, CDCl3): 7.51
(d, 1H, J = 7.2 Hz), 7.40–7.38 (m, 3H), 7.39–7.26 (m, 5H), 7.13 (d,
1H, J = 16.4 Hz), 7.11 (d, 1H, J = 16.4 Hz). 13CNMR(100 MHz, ppm,
CDCl3): δ = 139.9, 136.6, 134.7, 130.3, 131.1, 129.1, 128.1, 128.0,
127.5, 127.5, 126.7, 126.6, 126.3, 124.8. IR (KBr, cm−1): ν 3045, 2950,
1589.
[13] N. Kuhnert, Angew. Chem. Int. Ed. 2002, 41, 1863.
[14] B. L. Hayes, Aldrichim. Acta. 2004, 37, 66.
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2000, 65, 4537.
[16] N. N. Romanova,A. G. Gravis,N. V. Zyk,Russ.Chem.Rev.2005,74(11),
969.
Methyl trans-4-cyanocinnamate (entry 4, Table 4)
[17] R. Gedye, F. Smith, K. Westaway, H. Ali, L. Baldisera, L. Laberge,
J. Rousell, Tetrahedron Lett. 1986, 27, 279.
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[19] M. Larhed, A. Hallberg, J. Org. Chem. 1996, 61, 9582.
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2009, 23, 504.
M.p. 119–121 ◦C;[21] found 118–121 ◦C.1H NMR (500 MHz, CDCl3):
δ = 7.69 (t, 2H, J = 8.4 Hz), 7.62 (d, 1H, J = 8 Hz), 7.58 (d, 1H,
J = 8.1 Hz), 7.28 (d, 1H, J = 16 Hz), 6.54 (d, 1H, J = 16 Hz), 3.88
(s, 3H). 13C NMR (100 MHz, ppm, CDCl3): δ = 166.6, 142.4, 138.6,
132.7, 132.7, 128.4, 128.3, 121.4, 118.4, 113.4, 52.0. IR (KBr, cm−1):
ν 3044, 2956, 2225, 1720, 1639.
[21] A. R. Hajipour, K. Karami, A. Pirisedigh, A. E. Ruoho, J. Organomet.
Chem. 2009, 694, 2548.
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Acknowledgments
We gratefully acknowledge the funding support received for
this project from the Isfahan University of Technology, I. R. Iran
and Isfahan Science and Technology Town, I. R. Iran. Further
financial support from Center of Excellence in Sensor and Green
Chemistry Research (Isfahan University of Technology) is gratefully
acknowledged.
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Appl. Organometal. Chem. 2010, 24, 798–804